HK1118770B - Surface vehicle vertical trajectory planning - Google Patents

Abstract

An active suspension system for a vehicle including elements for developing and executing a trajectory plan responsive to the path on which the vehicle is traveling. The system may include a location system for locating the vehicle, and a system for retrieving a road profile corresponding to the vehicle location.

Description

Vertical trajectory design for land vehicles

The present application is a divisional application of the invention patent application entitled "vertical trajectory design for ground vehicle" filed on 18.2.2004, application No. 200410005418.8.

Technical Field

The present invention relates to an active vehicle suspension apparatus, and more particularly, to an active vehicle suspension system equipped with a vertical trajectory planning (tracking) system.

Disclosure of Invention

It is an important object of the present invention to provide an improved active vehicle suspension assembly.

In accordance with one aspect of the present invention, an automotive suspension system for use on a ground vehicle having a payload bay and a ground engaging member, the automotive suspension system comprising: a controllable suspension member for applying force between the payload compartment and the ground engaging member and a profile storage member for storing a plurality of road profiles. The profile includes vertical offset data. The system also includes a profile extraction microprocessor coupled to the controllable suspension component and the profile storage component and configured to extract from the profile storage device a profile corresponding to a section of the vehicle over which the vehicle is traveling.

In accordance with another aspect of the present invention, in a vehicle for operation on a roadway, the vehicle including a payload bay and a ground engaging member, an active vehicle suspension apparatus comprising: a force applying member coupled to the payload compartment and the ground engaging member for applying a force between the payload compartment and the ground engaging member to change the vertical position of the payload compartment relative to the ground engaging member; a profile storage section for storing a vertical profile of the road; a trajectory design development subsystem communicatively coupled to the force application component and the profile storage component for developing a trajectory design based on the stored profile and issuing commands to the force application component, the commands corresponding to the trajectory design.

In yet another aspect of the present invention, a method for operating an active vehicle suspension system installed in a land vehicle provided with a data storage component, comprises the steps of: determining a position of the ground vehicle; determining whether a trajectory plan corresponding to the location exists in the data stored in the surface vehicle; reacting to a determination that a vertical trajectory design is stored in the vehicle suspension system and extracting the design; the trajectory design is performed.

In a further aspect of the present invention, a method for operating an active vehicle suspension system installed in a land vehicle provided with a detecting member capable of detecting a vertical profile of a road and a data storage member, comprises the steps of: detecting the vertical profile of the road; recording the profile; the recorded profiles are compared with profiles stored in a database to determine whether the detected profile matches one of the stored profiles.

In another aspect of the present invention, an active suspension system for use on a road-operable ground vehicle, the system comprising: an active suspension component; a profile sensor for determining a profile of the road; a road profile storage section for storing a road profile database; a road profile microprocessor coupled to the memory component and the profile sensor and adapted to compare the detected profile to a database of profiles.

In yet another aspect of the present invention, an active suspension system for use on a ground vehicle comprises: an active suspension component; a positioning system for determining the location of the ground vehicle; a trajectory design storage section for storing a trajectory design database corresponding to the position; a trajectory planning microprocessor for determining whether the database contains a trajectory plan corresponding to the determined position, and for extracting the corresponding trajectory plan and sending commands to the active suspension component based on the corresponding trajectory plan.

In yet another aspect of the invention, a method for determining a position of a surface vehicle comprises the steps of: storing a plurality of road profiles associated with a plurality of locations and containing only incrementally measured vertical offsets of the road; measuring the vertical offset of a road section on which the vehicle is running; the measured vertical offset is compared to a plurality of road profiles.

In another aspect of the invention, a method for developing a trajectory plan for a vehicle, wherein the vehicle includes a vehicle suspension system, the vehicle suspension system further including a trajectory plan system for developing the trajectory plan and a controllable suspension member for causing a point on the vehicle to move along the trajectory plan, the method comprising: recording a profile comprising a plurality of data points representing positive and negative vertical offsets of the travel path; smoothing the contour data, the smoothing producing a plurality of positive and negative values; these smoothed data are recorded as a track design.

In yet another aspect of the present invention, a method for developing a trajectory plan for an active vehicle suspension apparatus, the method comprising the steps of: causing a vehicle to travel on a road segment; recording a plurality of data points representing the profile of the road segment; these data are smoothed to form the trajectory plan. This smoothing process preserves the positive and negative values of the data points.

In yet another aspect of the present invention, a method for operating a vehicle, the vehicle comprising: a controllable suspension member; a microprocessor; a plurality of sensors for determining at least one of the following parameters: a vertical offset, a force exerted by a controllable suspension component, a vertical velocity, and a vertical acceleration, the method comprising the steps of: storing a database of a plurality of profiles; driving the vehicle over a route and recording data measured by the sensor to provide measured data; the measured data is compared with a plurality of profiles to determine the degree of matching.

In another aspect of the invention, a method for developing an optimal trajectory plan for a vehicle including a controllable suspension component, the method comprising: developing a first track design corresponding to a contour by using a first characteristic value through a microprocessor for the first time; performing a first trace design for a first time, the first performing including recording performance data corresponding to the first trace design; modifying the first characteristic value for the first time to provide a second characteristic value; developing a second track design corresponding to the contour for the second time through the microprocessor by using a second characteristic value; performing a second design of the trajectory, the second execution including recording measurements of performance data corresponding to the second design of the trajectory; comparing the performance data corresponding to the execution of the first track design with the performance data corresponding to the execution of the second track design for the first time to determine better performance data; and recording the characteristic value corresponding to the better performance data in the first characteristic value and the second characteristic value as the current characteristic value for the first time.

In yet another aspect of the invention, a method of developing a vehicle trajectory plan, wherein the vehicle includes a payload compartment, a wheel, a plurality of sensors for determining respective conditions of the vehicle, and a controllable suspension member for applying forces between the vehicle and the payload compartment, the method comprising the steps of: recording a profile comprising a plurality of data points measured by the sensor, the data points representing a plurality of positive and negative values; the plurality of profiles are stored as a series of commands that enable the controllable suspension component to apply a force and a series of vehicle states measured by the at least one sensor are stored.

In yet another aspect of the present invention, an active vehicle suspension apparatus for a ground vehicle, wherein the ground vehicle includes a payload compartment and a ground engaging member, the vehicle for traveling along a roadway comprising: a controllable suspension member for correcting the amount of displacement between the payload compartment and the ground engaging member in response to the amount of vertical displacement of the roadway; a trajectory development system for commanding the controllable suspension member to apply a force to the controllable suspension member to correct the amount of displacement between the payload compartment and the ground engaging member prior to vertical movement of the ground engaging member.

In another aspect of the invention, a method for operating a vehicle comprising a payload bay, a front ground engaging member, and a rear ground engaging member, the vehicle further comprising a suspension system comprising: a controllable front suspension member for applying a force between the front ground engaging member and the payload compartment to modify a distance between the front ground engaging member and the payload compartment, the controllable front suspension member is provided with a centering position, the controllable front suspension member includes a centering subsystem for urging the controllable front suspension member toward the centering position, the suspension system further including a controllable rear suspension member for applying a force between the rear ground engaging member and the payload compartment to modify the distance between the rear ground engaging member and the payload compartment, the controllable rear suspension member is provided with a centering position, the controllable rear suspension member comprises a controllable centering system, the centering subsystem is used for pushing the rear controllable suspension component to a centering position (centered position); the method comprises the following steps: causing the vehicle to travel on a path where an obstacle is present, such that the front ground engaging member encounters the obstacle before the rear ground engaging member and causes the front controllable suspension member to exert a force in accordance with the fluctuation; and judging whether the amplitude of one of the road fluctuation parts is smaller than a first threshold value or not, and accordingly judging the amplitude of the fluctuation part to stop the rear suspension component from working on the centering subsystem.

In still another aspect of the present invention, a ground vehicle includes: a payload bay; a front ground engaging member; a rear ground engaging member; and a suspension system comprising a front controllable suspension member for applying a force between the front ground engaging member and the payload bay to modify a distance between the front ground engaging member and the payload bay, the front controllable suspension member having a centered position, the front controllable suspension member comprising a centering subsystem for urging the front controllable suspension member toward the centered position, the front controllable suspension member further comprising a detection system capable of determining an amplitude of a road disturbance encountered by the front ground engaging member; a rear controllable suspension member for applying a force between the rear ground engaging member and the payload compartment to modify a distance between the rear ground engaging member and the payload compartment, the rear controllable suspension member having a centered position, the rear controllable suspension member including a steerable centering subsystem for urging the rear controllable suspension member toward the centered position; and a control circuit responsive to the detection system for deactivating the centering subsystem of the rear suspension component.

In yet another aspect of the present invention, a method for operating a vehicle, the vehicle comprising a payload bay, a first ground engaging member and a second ground engaging member, the vehicle further includes a suspension system, the suspension system including a first controllable suspension component, means for applying a force between the first ground engaging member and the payload compartment to modify the distance between the first ground engaging member and the payload compartment, the suspension system further comprising a second controllable suspension member for applying a force between the second ground engaging member and the payload compartment, to modify the distance between the second ground engaging member and the payload compartment, the first and second controllable suspension members each include associated sensors capable of determining at least one of: vertical acceleration, vertical velocity, vertical offset of the road, amount of displacement of the suspension member and force exerted by the controllable suspension member, the method comprising the steps of: operating the vehicle over a stretch of road having a plurality of obstacles such that the first ground engaging member encounters portions of the obstacles before the second ground engaging member; determining the obstacle portions using a plurality of sensors coupled to the first controllable suspension component; based on the determination, the second controllable suspension member is caused to apply a force associated with the obstacle before the second ground engaging member encounters the portion of the obstacle.

In another aspect of the invention, a method for operating a vehicle, the vehicle comprising a payload compartment, a first ground engaging member and a second ground engaging member, the vehicle further includes a suspension system, the suspension system including a first controllable suspension component, means for applying a force between the first ground engaging member and the payload compartment to modify the distance between the first ground engaging member and the payload compartment, the suspension system further comprising a second controllable suspension member for applying a force between the second ground engaging member and the payload compartment, to modify the distance between the second ground engaging member and the payload compartment, the first and second controllable suspension members each include associated sensors capable of determining at least one of: vertical acceleration, vertical velocity, vertical offset of the road, amount of displacement of the suspension member and force exerted by the controllable suspension member, the method comprising the steps of: operating the vehicle over a stretch of road having a plurality of obstacles such that the first ground engaging member encounters those obstacles before the second ground engaging member; determining the obstacles using a plurality of sensors coupled to the first controllable suspension component; based on the measurement, the second controllable suspension component is caused to apply a force to the disturbance before the second ground engaging component encounters the obstacle.

In yet another aspect of the invention, a method for operating a vehicle, the vehicle including a payload bay, a ground engaging member, the vehicle further including a suspension system, the suspension system including a controllable suspension member for applying a force between the ground engaging member and the payload bay to modify a distance between the ground engaging member and the payload bay, the controllable ground suspension system having a centered position, the controllable suspension member including a reactive mode of operation and a trajectory planning mode of operation, the method comprising causing the vehicle to travel a section of road having a vertical obstacle; determining the amplitude of the obstacles; operating the controllable suspension component in a reactive mode if it is determined that the magnitude of an obstacle is less than a first threshold; if the amplitude of one fluctuation part is judged to be larger than the first threshold value and smaller than the second threshold value, stopping the operation of the centering subsystem; if it is determined that there is an undulation having a magnitude greater than the second threshold, the controllable suspension member is caused to apply a force against the obstacle before the ground engaging member encounters the obstacle.

Drawings

Other features, objects, and advantages of the invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of a vehicle provided with a controllable suspension arrangement;

FIG. 2 is a partial block diagram and partial schematic view of a controllable suspension apparatus according to the present invention;

FIG. 3 is a schematic diagram of the operation of a prior art active suspension apparatus;

FIGS. 4a-4c are schematic views illustrating the operation of the active suspension apparatus according to the present invention;

FIG. 5 is a schematic diagram of the operation of an active suspension apparatus according to the present invention;

FIGS. 6a, 6b and 6c are flow charts of the operation of the suspension system according to the present invention;

FIG. 7 is a schematic diagram of a trajectory design development method;

FIG. 8 is a schematic diagram of a data acquisition method according to the present invention;

FIG. 9 is a block diagram of a method for optimizing trajectory design;

FIGS. 10a-10c are schematic views of a vehicle according to the present invention traveling on a roadway surface;

fig. 11a-11c are schematic views of a vehicle according to the invention, travelling on a road surface.

Detailed Description

Referring now to the drawings, and more particularly to FIG. 1, there is shown a schematic view of a vehicle according to the present invention. A suspension system includes a plurality of surface engaging members, such as wheels 14, with the wheels 14 being connected to a payload compartment 16 (shown schematically as a plane in the drawings) by a controllable suspension member 18. In addition, the suspension system may also include conventional suspension components (not shown), such as coil or leaf springs or shock absorbers. Since one embodiment of the invention is an automobile, such face-engaging components are a plurality of wheels and the payload also includes a passenger, but the invention may also be practiced on other types of vehicles, such as trucks. Payload compartment 16 may include a plurality of tracks or wheels (runners). The invention may also be used on vehicles that engage the ground by some sort of suspension structure, such as magnetic levitation or air levitation, so that the ground engaging members include a variety of components that do not require physical contact with the ground, and the ground may include tracks or open terrain. For convenience of explanation, the present invention is described only with respect to an example applied to an automobile.

The controllable suspension component 18 may be one of a variety of suspension components capable of receiving or adapted to receive control signals from a microprocessor and react to those signals.

The controllable suspension component 18 may be some component of a conventional active suspension system in which the controllable suspension component is capable of reacting to a control signal in the following manner: the distance between the cabin 16 and the wheels 14 is changed by applying a force. Some suitable active suspension systems are disclosed in U.S. patent nos. 4960290 and 4981309, the contents of which are incorporated herein by reference. The force may be transmitted through components such as linear or rotary actuators, ball screws, pneumatic systems or hydraulic systems, and may include a plurality of intermediate components disposed between the wheels and the force generating components. The controllable active suspension component may also include an adaptive active vehicle suspension component, as described in U.S. patent 5432700, in which the signal may be used to modify the adaptive parameter and the adaptive increment. The controllable suspension components 18 may also be some of the components of a conventional suspension system that are capable of reacting to vertical forces resulting from the passage of the wheels 14 from uneven ground and applying forces reactively between the payload compartment 16 and the wheels 14. In conventional suspension systems, controllable suspension components may react to control signals by lengthening or compressing springs, by varying the rate of damping, or in other ways. In the following, the invention will be explained by way of an example of an embodiment in which the controllable suspension member is an active suspension member. Referring now to fig. 2a, there is shown a block diagram of a suspension arrangement according to the present invention. The controllable suspension member 18 is connected to a microprocessor 20, and the microprocessor 20 is in turn connected to a profile storage member 22 and an optional positioning system 24. The suspension system further includes a plurality of sensors 11, 13 and 15 connected to the payload compartment 16, the controllable suspension member 18 and the wheels 14, respectively. The sensors 11, 13 and 15 are connected to a microprocessor 20. Positioning system 24 may receive signals from external signal sources, such as positioning satellites 23. For convenience, only one controllable suspension member 18 is shown. The remaining wheels 14, controllable suspension components 18 and the various sensors 11, 13 and 15 are connected to a microprocessor 20 substantially in the manner shown in figure 2 a.

Microprocessor 20 may be a single microprocessor as shown. Alternatively, the functions performed by microprocessor 20 may be performed by multiple microprocessors or equivalent components, some of which may be located remotely from vehicle 10 and may also be in wireless communication with certain components of the suspension system located on vehicle 10.

The profile storage component 22 can be one of a variety of writable memory (e.g., RAM) or mass storage memory (e.g., magnetic or readable-writable optical disk). The profile storage component 22 may be included in the illustrated vehicle or may be located at a remote location and provided with a broadcast system for wirelessly communicating the road profile data with the vehicle. The positioning system 24 may be one of a variety of systems that may be used to provide longitudinal and latitudinal positions, such as a Global Positioning System (GPS) or an Inertial Navigation System (INS). The location system 24 may include a plurality of systems for indicating a location to a user input and may also include a plurality of contour matching systems that compare the contours of the roadway on which the vehicle is traveling with the contours stored in memory.

In one embodiment, the road on which the vehicle is traveling is a highway. However, the invention is also applicable to other types of vehicles that do not travel on public roads, such as open-road vehicles and vehicles that travel on tracks. A road may be generally defined by a location and a direction. The invention will be described in the following as an example of a motor vehicle for driving on roads.

The suspension system in which the present invention is installed may also include a trajectory planning system that may include (referring to fig. 2a) a microprocessor 20, a profile storage component 22, and a positioning system 24.

The location system 24 detects the location of the vehicle and the microprocessor 20 extracts a copy of the road profile from the plurality of profiles stored in the profile storage component 22 if possible. The microprocessor 20 calculates or extracts a trajectory plan according to the contour of the road and sends control signals to the controllable suspension members 18 to execute the trajectory plan. The extraction of the profile, calculation of the trajectory and control of the suspension components can be performed by a single microprocessor as shown, or, if desired, by a plurality of separate microprocessors. The method for designing and developing the trajectory will be described in detail with reference to fig. 6a and 6 b. If the controllable suspension member 18 is an active suspension device capable of acting in response to road forces, the microprocessor 20 may send an adjusted control signal to the controllable suspension member 18 based locally on the contour of the road.

In one conventional form of construction, a road profile includes a series of vertical offsets (z-axis) from a reference position. The z-axis offset measurement is typically determined over a plurality of equal distances from the position at which the direction of travel is determined. A road profile may also contain other data, such as x-axis and y-axis offsets; a compass heading; a steering angle; or other information that may be included in a navigation system, which may be, for example, a commercially available vehicle navigation product. Other data may involve the microprocessor 20 and the profile storage component 22 having greater processing power, but these additional data may be useful in more accurately locating the vehicle or in uniquely relating a location to a road profile when using the "dead reckoning" or pattern matching techniques described below. In addition, these additional data are also useful in determining the magnitude of the tractive effort, which should be considered in designing the trajectory.

The trajectory plan is a predetermined path in space for a point or set of points on the payload compartment. To control the pitch of the vehicle, the trajectory may be expressed as at least two points, a forward point and a rearward point within the payload compartment. To control the swing of the vehicle, the trajectory plan may be expressed as at least two points located on either side of the vehicle. In a four-wheeled vehicle, four points can be conveniently used to develop the trajectory design in the payload bay. These pairs of points are averaged (e.g., by averaging two points on either side of the vehicle to account for hunting during the rendering of the trajectory design, or by averaging two points at the front and rear of the vehicle to account for jerking during the rendering of the trajectory design). For convenience of explanation, the present invention will be described with respect to only one point. The microprocessor issues commands to the controllable suspension members 18 to move the vehicle along the trajectory plan. The details of the trajectory design and the implementation of the trajectory design are described in more detail in the examples below.

The trajectory design should take into account a number of factors, such as matching the pitch or roll of the vehicle to the degree of pitch or roll desired by the occupant; reducing the vertical acceleration of the payload bay; the stroke of the suspension device to absorb a bump or a sink (hereinafter referred to as "surge") on the road surface becomes large; reducing the magnitude or occurrence of acceleration at undesirable frequencies, such as frequencies of about 0.1 hertz, which would result in nausea; increasing the traction of the tire; or other factors. Trajectory planning may also include "predicting" and reacting to obstacles on the road before encountering the obstacle, as will be described below in connection with fig. 5. Furthermore, if the suspension system includes a conventional type spring capable of supporting the weight of the vehicle and operation of the active suspension components will either elongate or compress the conventional type spring, the tracking design should take power losses into account.

Referring now to fig. 2b, there is shown another embodiment of the present invention incorporating a track design storage component 25. The other components in fig. 2b are substantially identical to those in fig. 2a, except that the profile component 22 in fig. 2a is replaced by a trajectory design storage component 25. The track design storage means 25 may be one of a variety of writable memory, such as RAM, or a mass storage means such as a magnetic or read-write disc. The storage means 25 for the trajectory plan may be included in the illustrated vehicle or may be located at a remote location via a broadcast system capable of wirelessly communicating the road profile data with the vehicle.

The operation of the embodiment of fig. 2b is similar to that of the embodiment of fig. 2a, except that microprocessor 20 extracts and calculates a trajectory design related to position, rather than an outline.

Another embodiment of the invention comprises both the profile storage means shown in fig. 2a and the trajectory plan storage means shown in fig. 2 b. In an embodiment comprising a profile storage component 22 and a trajectory design storage component 25, these storage components may be separate components or may be different parts of one memory component. The operation of these embodiments including the track design storage component 25 will now be described with reference to figure 6 c.

FIG. 3 illustrates an example of operation of a conventional active suspension apparatus without a trajectory design subsystem. In fig. 3, when the front wheel 14f 'encounters an inclined section 41, the controllable suspension member 18 f' will exert a force to shorten the distance between the payload compartment 16 'and the front wheel 14 f'. As the height difference r due to the ramp approaches the maximum amount of downward displacement of the suspension member, the suspension member 14f 'will "tip" toward the ramp 41 and, in extreme cases, the suspension member 14 f' may reach or approach a "bottoming out" condition, leaving little or no travel for the suspension member necessary to allow a crash to occur on the rising surface.

Many suspension systems are provided with a centering subsystem that maintains the desired suspension travel and prevents the suspension components from reaching the highest or lowest points. These centering systems may push the suspension system toward a centered position if the suspension system is near the lowest or highest position. The spring system itself has a centering system because the force exerted by the spring is proportional to the amount of extension or compression of the spring. A "centered" position generally refers to a condition where no upward or downward force is acting on the suspension, other than the weight of the vehicle. The centered position is not necessarily a position that has the same levitation effect on the upward and downward wave motion.

Referring now to figures 4a-4c, there is shown an example of operation of an active suspension arrangement according to the present invention. The microprocessor 20 shown in fig. 2a provides a calculated track design 47 that closely matches the road surface including the ramp section 41, and the microprocessor 20 also sends appropriate control signals to the controllable suspension members 18f and 18r to move the suspension members 18f and 18r along the track design 47. In this example, the suspension components can be moved along the track design by: not exerting a force that can shorten or lengthen the distance between the vehicles 14f, 14r and the payload bay 16; alternatively, if the suspension system includes a conventional spring, the suspension components can be moved along the track design by: a sufficient force is applied to counteract the acceleration caused by the force applied by the spring. In fig. 4b, the payload compartment 16 is tilted slightly when the vehicle reaches the same road position as in fig. 3. In fig. 4c, the payload bay is at an angleAnd the angle is consistent with the inclination angle theta of the road. The payload compartment is gradually tilted in order to be able to follow the inclination of the road, which corresponds to the driver's expectations. Another advantage is that: if there are fluctuations, such as bumps 49 or dimples 51 on the road, the suspension device can absorb such fluctuations with full travel.

The examples shown in figures 4a-4c illustrate the principles and performance of the trajectory planning subsystem that may affect the proper operation of the active suspension assembly after the trajectory planning has been completed when the controllable suspension member 18 is exerting a small or no net force. In fig. 4b and 4c, the vehicle is accelerating in an upward direction, and normal reactive operation of the active suspension will shorten the distance between the wheel 14f and the payload compartment 16, as shown in fig. 3. For a suspension arrangement provided with the present invention, the active suspension will remain in a centered position when operated according to the trajectory plan, thus enabling the payload compartment of the vehicle to move along the trajectory plan 47. Alternatively, the example shown in FIGS. 4b-4c may be combined with the operational example shown in FIG. 5, described below, such that the payload compartment of the vehicle moves along the trajectory design 47 a.

FIG. 5 illustrates another example of operation of an active suspension apparatus provided with a trajectory planning subsystem. The road profile 50 comprises a large protrusion 52. The microprocessor 20 (shown in fig. 2a or 2 b) provides a calculated trajectory plan 54 suitable for the road profile 50. At point 56, the controllable suspension member 18 will exert a force to gradually lengthen the distance between the wheel 14 and the payload compartment 16 before the wheel 14 encounters the bump 52. Normal operation of the controllable suspension member 18 will cause the controllable suspension member 18 to exert a force that will shorten the distance between the payload compartment and the wheel 14 when the wheel 14 passes over the protrusion 52. When the wheel 14 reaches the top 57 of the bump 52, the controllable suspension member 18 begins to exert a force that will elongate the distance between the payload compartment 16 and the wheel 14. After the wheel 14 moves past the end of the projection 52, the controllable suspension member 18 will exert a force that will shorten the distance between the payload compartment 16 and the wheel 14. The example of fig. 5 illustrates the principle of the trajectory planning subsystem enabling the controllable suspension member 18 to exert a force that elongates or shortens the distance between the wheel 14 and the payload compartment 16, even over a horizontal road segment, and the principle of the trajectory planning scheme enabling the controllable suspension member to react to a disturbance in the road before encountering the disturbance.

The example shown in fig. 5 illustrates several advantages of a suspension system according to the present invention. By beginning to react to the bump 52 before encountering the bump 52 and by continuing to react to the bump after passing the bump, the vertical displacement of the payload compartment is distributed over a greater range of distances and over a longer period of time than if the suspension system had only reacted to the bump 52 when the tire hit the bump 52. In this way, the vertical displacement, vertical velocity and vertical acceleration of the payload compartment 16 are low, which reduces occupant discomfort compared to suspension systems without a track design system. Such a trajectory planning subsystem can be effectively applied in the presence of the large bump 52 and the normal operation of the controllable suspension components can still handle disturbances that are not represented in the road profile. If the road profile has sufficient resolution to identify a large disturbance, such as a large bump 52 or a long or large slope, or if the road profile is slightly less accurate, the active suspension component in the reactive mode of operation reacts only to the difference between the profile and the actual road surface. For example, if the design profile of the larger lobe 52 is slightly different from the stored profile from which the trajectory is designed, then the active suspension system need only react to the difference between the actual profile of the lobe 52 and the stored profile. Thus, even if the contour is not very precise, the ride feel of the occupant is generally better than if the suspension system lacks a track design system.

The trajectory design may take into account the perception threshold of the passenger. For example, in FIG. 5, if the trajectory plan begins to rise before point 56 and the vehicle returns to an equilibrium position after point 58, the driver of the vehicle will experience very little vertical acceleration. However, the difference in vertical acceleration may not be so great as to be felt by the vehicle occupant that the active suspension device does not have to react before point 56 or continue to react after passing point 58. Furthermore, if the vehicle includes a conventional suspension spring, the force applied by the active suspension between points 56 and 47 may need to apply a force that elongates the spring in addition to the force required to lift the vehicle, so that the track design does not begin to rise, and so that less power is consumed than if the rise had earlier begun.

Referring now to FIG. 6a, a method for developing, implementing and modifying a trajectory plan using a system that does not have the optional positioning device 24 installed is shown. At step 55, sensors 11, 13 and 15 collect profile information of the roads and transmit the information to microprocessor 20, which in turn records the profiles of the roads in profile storage unit 22. In step 58, the contour microprocessor compares the contour information of the road with the contour of the road that has been stored in the contour storage section 22 in advance. This comparison may be accomplished using a pattern matching system as described below. If the profile information for the road is consistent with the pre-stored road profile, then the profile is extracted at step 62a and the microprocessor 20 will calculate a trajectory plan appropriate for the profile. At the same time, in step 62b, the sensors 11, 13 and 15 provide signals representative of the road profile, which can be used to modify the profile stored in the profile storage unit 22, if required.

If at step 58 it is determined that: if all of the road profiles that are pre-stored do not match the road profile information collected at step 56, then the controllable suspension component 18 will be operated in the reactive mode at step 64.

Referring now to FIG. 6b, a method for developing, modifying and performing trajectory planning tasks with a system including optional positioning system 24 is shown. In step 70, the positioning system 24 determines the position and orientation of the vehicle. In step 72, the trajectory planning microprocessor 20 examines the contours stored in the contour storage unit 22 to determine if a contour exists that is associated with the location. If a contour is associated with the location, microprocessor 20 extracts the contour and calculates or extracts a trajectory plan at step 74 a. Depending on the manner in which the data is stored and processed, the direction of travel may be taken into account in step 72 in addition to the location when determining whether a relevant profile exists. At the same time, at step 74b, the sensors 11, 13 and 15 provide a plurality of signals representative of the road profile, which can be used to modify the profile stored in the profile storage unit 22 if required.

If it is determined at step 72 that all of the pre-stored road profiles are not associated with the above-described position and orientation, then at step 76a, the controllable suspension member 18 will act in a reactive, active suspension member manner. Meanwhile, at step 76b, the sensors 11, 13 and 15 provide a plurality of information indicative of the road profile stored in the profile storage section 22.

Reference is now made to fig. 6c, which shows a method for developing, modifying and executing a trajectory planning in the embodiment of the invention shown in fig. 2b, but also provided with some kind of component capable of positioning the vehicle, such as the positioning system 24 or the profile storage component 22 shown in fig. 2 a. At step 70, the positioning system 24 determines the position and orientation of the vehicle. At step 172, the trajectory design microprocessor 20 reviews the trajectory design in the trajectory design storage component 25 to see if there is a trajectory design associated with the location. If there is a trajectory design associated with that position, then at step 174a, the microprocessor 20 extracts the trajectory design and transmits the information to the controllable suspension member 18 for execution by the suspension member 18. In addition to the position, the direction of travel can also be taken into account in step 172 depending on the way in which the data is stored and processed when determining whether a relevant contour is present. At the same time, in step 174b, the signals representing the actual profile emitted by the sensors 11, 13 and 15 can be recorded, so that the trajectory plan associated with that position can be subsequently modified to make the driving smoother or more comfortable.

If it is determined at step 172 that all of the pre-stored road profiles are not associated with the above-described position and orientation, then at step 176a, the controllable suspension member 18 is operated in a reactive active suspension mode. At the same time, the trajectory formed by the reactive operation of the controllable suspension member 18 is represented by a plurality of signals that are recorded as the trajectory plan at step 176b, so that the existing trajectory plan can be modified to provide a smoother or more comfortable driving feel.

The track design may be stored in a variety of forms, as will be described below with reference to FIG. 8. Furthermore, if the trajectory design is calculated using characteristic parameters (e.g., filter break-through points or window widths, as described below), these parameters may be saved and the trajectory design may be calculated "on the fly". This approach enables the system to operate with less memory but requires more computing power.

The method of fig. 6a, 6b and 6c illustrates one learning feature of the present invention. The contour or trajectory design, or both, may be modified each time the vehicle is driven over a road segment so that the trajectory design provided by microprocessor 20 may be used to provide a smoother driving feel for the owner of the vehicle later on during travel over the same road segment. In addition, such a vehicle suspension system may also employ the optimization routine shown in fig. 9.

While active suspension devices provided with a less accurate positioning system can operate in a manner that is superior to conventional active suspension devices, it is desirable to be able to accurately determine the position of the vehicle, ideally to within 1 meter. One way to achieve high accuracy is to install a high accuracy GPS system, such as a differential system with a centimeter accuracy, in the positioning system 24 shown in fig. 2 a. Another approach is to install a less accurate GPS system (e.g., a 50 meter non-differential system or other positioning system without GPS) and an assisted pattern matching system in the positioning system 24 shown in fig. 2 a.

A pattern matching system includes searching a target data string for a known data sequence. A method particularly suited for pattern matching data that is respectively incremented or decremented by a reference point includes multiplying a number of data strings having the same length as the target data string by the number n of a known sequence. Then, the n products are accumulated, and when the sum reaches a maximum, it is said that there is a high degree of consistency (matching). Of course, other pattern matching methods (using other methods to determine high degree of matching) may be used.

This pattern matching method can be applied to a track design type active suspension apparatus by recording a pattern of z-axis displacement with respect to a reference point and using the pattern of z-axis displacement as a search data string. Pattern matching can then be performed in at least two ways. In one application, the GPS system is used to obtain the general location of the vehicle (within 30 meters), and then more accurately locate the vehicle using a pattern matching method by applying a target string to a pre-stored z-axis offset stored in the profile storage component 22 shown in FIG. 2 a. In a second application, pattern matching is used to compare the z-axis offset pattern measured by the sensors 11, 13 and 15 shown in FIG. 2a with the z-axis offset stored in the profile storage component 22 to determine if there is a profile stored in memory.

To supplement the GPS and pattern matching systems, a "dead reckoning" system may also be employed. In a dead reckoning system, a change in the position of a vehicle is estimated by monitoring the distance traveled by the vehicle and the direction of travel of the vehicle. When the position of the vehicle is accurately found, the travel distance of the vehicle can be tracked (determined) by calculating the number of revolutions of the wheel, and the travel direction of the wheel can be determined by recording the angle or steering angle of the wheel. Dead reckoning is useful if the GPS readings are very difficult (e.g., if there are tall buildings nearby), and also reduces the number of times GPS readings must be taken.

Reference is now made to fig. 7, which is a schematic illustration of an automobile and a road surface, showing the development of a track design. Line 80 represents the road profile stored in the profile-section 22 shown in figure 2 a. Line 82 represents road profile 80 after having been filtered in a two-way low-pass manner by a break frequency in the range of 1Hz, and is used as a trajectory plan; the bi-directional filtering removes phase lag inaccuracies that can be represented by a single directional filter. The controllable suspension member 18 shown in fig. 2a causes the payload compartment of the vehicle 84 to move along the trajectory design shown by line 82 as the vehicle 84 passes over the road surface indicated by line 80. Conventional operation of an active suspension device can easily handle high frequency, low amplitude disturbances on the road. The trajectory design formed by low-pass filtering is very useful for handling the situation shown in fig. 3 and 4a-4 c.

When the speed of the vehicle is constant, the road profile data is processed in the time domain of developing the track design, so that the method is very beneficial; i.e. the vehicle travels at the same speed during each journey of the entire road section.

In some cases, it may be more useful to process data in the spatial domain than in the temporal domain. As it is more convenient to store the data in a spatial form and processing the data in the spatial domain does not require conversion of the data to a temporal form. In addition, the data are processed in the space domain, and the speed can be used as a variable to calculate the track design; that is, the trajectory design may vary from speed to speed. If the data is processed in the spatial domain, it is suitable to convert a certain amount of the time domain, for example with the aim of reducing the acceleration at harmful frequencies, which may be for example the "seasickness" frequency of 0.1 Hz.

In addition to filtering road contours in the spatial or temporal domain, the development of trajectory design should take into account a number of factors. For example, the trajectory design may take into account large disturbances on the road, as shown in fig. 5, and particularly as described in corresponding sections herein.

Referring now to FIG. 8, a methodology of collecting data points that facilitate processing of data in either the time domain or the spatial domain is illustrated. FIG. 8 also illustrates a method of converting data from the time domain to the spatial domain. Data from sensors 11, 13 and 15 are collected over a time interval Δ t. The typical value of Δ t ranges from 0.1ms (equal to the sampling rate of 10 kHz) to 1ms (equal to the sampling rate of 1 kHz). The data points taken within the interval 94 are combined and averaged, where the interval 94 is the distance Δ x traveled by the vehicle. Next, the averaged data is used as data for determining a road contour and data for calculating a trajectory design. Conventional values for Δ x are 4 to 8 inches (10.2 to 20.3 centimeters); the interval Δ x may be determined by sensors disposed in the vehicle driveline, which are also capable of providing readings from the vehicle speedometer and odometer. The number n of time intervals Δ t92 acquired in the section of the vehicle travel distance Δ x changes with the change in vehicle speed.

In one embodiment of the invention, the averaged data points are processed to determine a profile that consists of the z-axis offset from time (i.e., the representation of the profile in the time domain). Since the data from the sensors 11, 13 and 15 may be indicative of the displacement, velocity or acceleration of the suspension components; thus, the processing method may include mathematically transforming some of the data to obtain the z-axis offset.

In another embodiment of the invention, the time domain representing the profile is converted to a spatial domain consisting of z-axis offsets from the spatial measurements or to a spatial position by processing the time domain data with distance traveled or speed from a reference position. A profile consisting of the offset of the z-axis relative to the distance traveled can also be developed by directly collecting the data in the form of the spatial domain over the spatial interval Δ x '96 (and, if desired, over the average data points acquired over the larger spatial interval Δ x94, which in turn includes the m distance intervals Δ x'). The road profile, expressed in the spatial domain, is not governed by the vehicle speed. The contours are preferably represented in the spatial domain in the following cases: if the contour is supplemented by position information determined by a GPS system, inertial navigation system, pattern matching method or dead reckoning, or other method in spatial form; if there is a profile data corresponding to a location, and if the corresponding profiles are represented in spatial form; or if driving over the road section at a greatly varying speed.

In yet another embodiment of the present invention, the profile may be recorded as a series of data points representing the vehicle state, which are measured by sensors 11, 13 and 15. In this embodiment, data from some or all of the sensors 11, 13, and 15 is stored in its natural dimensions (i.e., force, acceleration, and velocity are stored as force, acceleration, and velocity, respectively, and not converted to other units of measure, such as vertical deflection). These data may be averaged over the time and distance described above. This embodiment is particularly useful in the pattern matching system described above. For the road profile recorded in this embodiment, the pattern matching work can be done in such a manner that the vehicle state measured by the sensors 11, 13, and 15 is compared with the recorded profile, thereby determining the degree of coincidence. Recording the profile as a series of data points facilitates the inclusion of other data in the profile data in addition to the vehicle condition measured by sensors 11, 13 and 15. Other data may include lateral acceleration, velocity or displacement of the suspension device, compass direction, steering angle, or other data that may be included in commercially available navigation systems. This additional data can be used to make the pattern matching more accurate.

One way to develop trajectory planning is to smooth the data representing the contours in a positive and negative manner. One method of smoothing is to perform a low pass filtering, preferably bi-directional low pass filtering, on the contour data. If the contour is represented in spatial form, then the filter is a spatial filter; in one embodiment, the spatial filter is a true low pass filter with a fixed break point of about 15 to 30 feet (4.6 to 9.1 meters). If the contour is represented in the form of time data, then the filtering operation can be done in the form of time or frequency domain (the time data can be converted into the frequency domain by fourier transform). In other embodiments, these filters may be real or complex filters having different sizes or grades. The trajectory design can be developed by performing multiple passes in each direction of the filter. Although low-pass filtering of temporal or spatial data is one method of developing a trajectory design, other methods of smoothing contour data may be used to develop a trajectory design. Other methods of smoothing the data include anti-causal nonlinear filtering, averaging, windowed averaging, and the like.

As described above, data may be represented in the form of positive and negative values, e.g., bumps may be treated as positive values and pits (or "craters") may be treated as negative values. The smoothing of the data still retains positive and negative values. The positive and negative values in the retained data enable the trajectory design to cause the controllable suspension component to apply a force in either direction, for example in the case of a bump, which can shorten the distance between the wheel and the passenger compartment, and in the case of a dent, which can lengthen the distance between the wheel and the passenger compartment. Retaining positive and negative values does not require the active suspension system to modify a parameter of the controller, such as an increment; it is sufficient to always represent the data as a positive value, e.g. root mean square. The active suspension system, which controls the increments, controls the suspension device to apply a force that shortens or lengthens the distance between the wheel and the passenger compartment according to road disturbance conditions only when a disturbance is encountered; and when a disturbance is encountered, it can be determined whether such disturbance is a positive or negative value. The active suspension system according to the invention applies a force capable of lengthening or shortening the distance between the wheel and the passenger compartment before a disturbance is encountered; thus, the data used in the suspension system of the present invention preferably retains positive and negative values.

The filter used to develop the trajectory design may have a fixed break point or a variable break point. For example, a filter with a greater length (with a greater length in the spatial or temporal domain, or with a lower frequency in the frequency domain) can advantageously be used on long, flat road sections than on undulating road sections.

FIG. 9 illustrates a method for optimizing a trajectory design. In step 100, a contour is determined by driving on a road or by extracting a contour from a database. At step 106, a trajectory plan is developed. At step 108, a simulation executes or actually executes a new trajectory plan and records measurements (or combinations of measurements) of certain properties (e.g., suspension displacement, power loss, tractive effort, vertical velocity or vertical acceleration of the payload compartment) determined during execution of the new trajectory plan. At step 109, these performance results are compared with the measurements of all prior trajectory designs obtained by calculating the profile, and the characteristics corresponding to the better performance are retained based on the measurements of these performance parameters. Of course, depending on the performance metric, a "better performance" may be a performance measurement with a greater or lesser value. For convenience, in this specification, it is assumed that the performance index refers to "better performance" as a measurement result with a smaller value (e.g., power loss, vertical velocity, vertical acceleration). In optional step 110, it is determined whether an appropriate optimization condition exists. If a suitable optimization condition exists, then the optimizer is activated. If a suitable optimization condition does not exist, then at step 104 one or more of the characteristic parameters used to develop the trajectory plan are modified. Steps 106, 108, 109, and 110 may then be repeated until an optimization condition exists, or until something occurs (e.g., changing a characteristic value across a range of values or within a predetermined range of values).

The specific trajectory design characteristic values that may be modified depend on the method used to develop the trajectory design. For example, if the trajectory design is developed by low-pass filtering the contour data, the break point of the filter may be the property value that has been modified; if the trajectory design is developed by window averaging, the size of the window may be the modified characteristic value.

In one embodiment of the invention, the trajectory design may be developed by smoothing the contour data using a low pass filter. The first trajectory design was developed using an initial seed value (initial seed value) of the interrupt frequency of the low-pass filter. The initial seed value may be selected based on the smoothness of the road: longer (or low frequency) discontinuities are used if the road surface is flat, and shorter (or high frequency) discontinuities are used if the road is undulating. The latter trajectory design may be done with filters having different (spatial or temporal) break points. If either increasing or decreasing the break point of the filter results in a better performance index, or some predetermined performance limit is reached, then there is a condition that can be optimized appropriately.

The above-described method is consistent with the concept of finding local maxima in system performance. A variety of known optimization techniques may be employed that enable the system to find the best overall performance. For example, if only one characteristic is changed, the characteristic may be changed over the entire range of possible values for the characteristic and its performance calculated for each value. Alternatively, more sophisticated gradient-based search methods may be used to increase the speed with which the best conditions are found. These gradient-based methods can also be used to find the best performance (local or global) when more than one characteristic parameter can be changed at a time.

The procedure shown in fig. 9 can be modified in various ways. Also, the length of the link using the program shown in fig. 9 may vary. The program shown in fig. 9 may be executed by a computer remote from the vehicle and may be downloaded into the vehicle. The program shown in fig. 9 may be executed by a microprocessor installed in the automobile. The individual characteristics may vary within a limited range of values, and the characteristics corresponding to the best performance index remain unchanged. The procedure may be executed when the computing power of the vehicle is not being used, for example when the vehicle is in a parked state. The trajectory planning may be performed when the vehicle actually passes through the road section, or may be simulated when convenient, for example when the vehicle is parked or not driving.

As mentioned above, a trajectory plan is a predetermined path of movement of a point or a set of points on a payload compartment in a space. The trajectory plan may be stored in space or as a series of forces applied by the controllable suspension member 18 between the payload compartment 16 and the wheels 14 that cause a point, such as a point within the passenger compartment, to move along the trajectory specified by the trajectory plan. If the trajectory planning has been performed, the trajectory planning may also be stored in the form of a series of vehicle states measured by the sensors 11, 13 and 15, or in the form of a set of commands to controllable suspension components.

Calculating and storing the trajectory plan in the form of the force or in the form of the vehicle state simplifies the calculation process of the trajectory plan, since this eliminates the need to mathematically convert the data to obtain the appropriate units of measure. For example, if the trajectory plan is expressed in terms of the force exerted by the controllable suspension element, the profile data can be low-pass filtered to obtain a trajectory plan that is also expressed in terms of the force exerted by the controllable suspension element. Thus, the calculation of converting the data from force to acceleration, acceleration to velocity, and velocity to displacement is omitted.

Figures 3, 4a-4c and 5 and the corresponding portions herein illustrate situations where operation of the trajectory planning subsystem may affect the normal reactive operation of the active suspension components. In fig. 3, normal reactive operation of the suspension components "tilts" the vehicle toward the slope. In fig. 4a-4c, the controllable suspension components of the trajectory planning system are used to move the vehicle along a predetermined path at a slope within a range, rather than "leaning" toward the slope. This trajectory design does not cause the controllable suspension components to exert forces even if there are disturbances on the road. The track design also allows the controllable suspension components to apply a force related to road undulations before a disturbance is encountered. Even if the obstacle has been crossed, the trajectory design may still allow the controllable suspension component to continue to exert a force related to road undulations.

Fig. 10a-10c are schematic views of a car and a road surface, respectively, showing the application of the invention to front and rear wheels. The "front to back" feature is particularly useful when the vehicle first passes a road segment and there is no available road profile. Fig. 10a and 10b use information from sensors relating to the front wheels in order to develop a track design for the rear wheels. This feature of the invention is illustrated by the trajectory of a point 114 located above the front wheel 14 and within the passenger compartment and the trajectory of a point 116 located above the rear wheel 14r and within the passenger compartment. The front and rear wheels 14f and 14r are mechanically coupled to the payload compartment 16 by controllable suspension members 18f and 18r, respectively. The vehicle travels on a road having an obstacle 112a with a height h1 that is greater than the available hover stroke of the suspension device in the centered position and less than the total combined hover stroke (i.e., the sum of the available up and down strokes of the suspension device in the centered position). When the front wheel 14f hits an obstacle 112a, the suspension system reacts to keep the trajectory of point 114 straight. When the suspension system bottoms out or near, such as at point 118, the upward force generated by the road barrier will be transferred to point 114, and point 114 will move along path 120. As mentioned above, many suspension systems are provided with centering subsystems that can be used to prevent the suspension from bottoming out and remaining with a certain suspension travel; the action of these systems will also cause point 114 to produce an upward acceleration and will also form a route similar to route 120.

As the front wheel travels over the section s, the microprocessor records the road profile and smoothes the profile data to provide a trajectory plan executed by the rear wheel controllable suspension member 18 r. As the rear wheel approaches the starting point 122 of the section s, the controllable suspension member 18r will exert a force to elongate the distance between the vehicle 14r and the passenger compartment 16 prior to engagement with the obstruction 112a, thereby causing the point 116 to move gradually upward. When the wheel 14f encounters an obstacle 112a, the normal reactive action of the controllable suspension component 18r is to apply a force that moves the point 116 along the trajectory design 124. A greater suspension travel is achieved because the controllable suspension components have lengthened the distance between the wheels and the passenger compartment, and the controllable suspension components are able to absorb the undulations 112a without reaching or approaching the lowest position. A trajectory such as trajectory 124 may be more comfortable for passengers in the vehicle because it avoids the problems of excessive vertical acceleration and velocity.

Another feature of the present invention is shown in fig. 10 b. A vehicle similar to the vehicle shown in figure 10a is provided with a centering system for maintaining available suspension travel and for bottoming out the suspension components. If the suspension member is near the lowest or highest point, the centering subsystem urges the suspension member system toward a centered position, which preserves suspension travel and allows for some vertical acceleration of the passenger compartment. The road barrier 112a has a height h2 that is slightly less than the available suspension travel when the suspension member is in the centered position. When the front wheel 14f contacts the obstacle 112b, the controllable suspension member 18f is actuated to maintain the passenger compartment level and prevent vertical acceleration of the passenger compartment. The centering system is actuated when the suspension component is near the lowest point, such as point 126, to prevent the suspension component from reaching the lowest point by causing some vertical acceleration of the passenger compartment, as indicated by point 126 in path 128. As the front wheel moves over the obstacle 112b, the sensor records the height h2 of the obstacle. Because the height of the obstacle 112b is less than the available suspension travel, the controllable suspension components are unable to operate the centering subsystem of the rear wheels. When the rear wheel 14r passes over the obstacle 112b, the passenger compartment does not move vertically, as shown by path 130.

A variant of the example shown in figure 10b is shown in figure 10 c. In the example of fig. 10c, when the passenger cabin begins to move in the vertical direction, and the front wheel is at point 126 and the rear wheel is at point 126', the rear controllable suspension component will apply a force to move the path 130 of the rear point 116 along the same trajectory as the front point 114. This reduces the degree of lean experienced by the passenger. When the rear wheel hits an obstacle 112b, the rear suspension components can be operated in the manner shown in fig. 10 b.

Referring now to fig. 11a and 11b, another feature of the present invention is shown. In fig. 11a, the front controllable suspension member 18f is actuated to maintain the passenger compartment level when the front wheel 14f encounters the starting point 136 of a long uphill 138 on the road and the controllable suspension member lacks the contour of the road segment. The action of the front controllable suspension member to maintain the passenger compartment level continues until point 132 is reached, toward which point 132 the front controllable suspension member 18f is angled, and which point is near the lowest point as described with reference to fig. 3. When the front controllable suspension component reaches or approaches the lowest point, a centering subsystem may cause the front controllable suspension component 18f to move toward a centered position, such as toward point 134. In the interval between points 132 and 134, the vehicle occupants, particularly the front row occupants, experience a "leaning" sensation and, unexpectedly, an upward acceleration after the vehicle encounters the incline. This may disconcert the driver. Furthermore, if the front suspension components are held in a centered position and the vehicle is not held horizontally, the occupant will also experience a vertical acceleration event that the occupant has not previously experienced. This vertical acceleration, suspension displacement and other measurements are recorded by the microprocessor, which causes the rear suspension components to react.

In fig. 11b, when the rear wheel 14r hits the starting point 136 of the long uphill 138, the microprocessor issues a command to the rear suspension component to keep it in a centered position and not react to the uphill. As a result, the rear point 116 will follow a path similar to the uphill slope of the road, so that the driver of the vehicle, in particular the passengers in the rear row, will experience less acceleration when the rear wheels encounter an uphill slope than when the front wheels encounter an uphill slope. Furthermore, the magnitude of the upward acceleration experienced by the passenger is at its discretion, as well as the upward acceleration it experiences.

The examples shown in figures 11a and 11b show that a controllable suspension member according to the invention reacts less to certain road obstacles than a conventional reactive suspension arrangement. In a practical embodiment, the operational embodiment of FIG. 11b may be combined with the operational example of FIG. 10a to reduce the upward acceleration at point 136 of FIGS. 11a-11b, thereby allowing the actual trajectory to distribute the upward acceleration over a longer vertical distance, such as trajectory 130a of FIG. 11 c.

Automotive suspension systems that do not utilize information from the front suspension components to affect the operation of the rear wheel suspension components do not achieve the effect of improving ride comfort shown in fig. 10a, 10b, and 11 b. Automotive suspension systems that utilize information from the front suspension components to alter the characteristics of the control system for the rear suspension components do not allow the rear suspension components to exert a force before encountering an obstacle.

The above has described a novel apparatus and technique for designing a vertical trajectory. It will be apparent to those skilled in the art that various modifications can be made, and that the invention can be used in many ways without departing from the scope of the specific apparatus and techniques disclosed. Accordingly, the invention is to be construed as embracing all novel features and novel combinations of features already disclosed in the above-described apparatus and techniques and the scope of the invention is limited only by the appended claims.

Claims (7)

1. A method for operating a vehicle, said vehicle comprising a payload compartment, a front ground-engaging member, and a rear ground-engaging member, said vehicle further comprising a suspension system, said suspension system comprising a front controllable suspension member for applying a force between said front ground-engaging member and said payload compartment to modify a distance between said front ground-engaging member and said payload compartment, said front controllable suspension member having a centered position, said front controllable suspension member comprising a centering system for urging said front controllable suspension member toward said centered position, said suspension system further comprising a rear controllable suspension member for applying a force between said rear ground-engaging member and said payload compartment, to modify the distance between said rear ground engaging member and said payload compartment, said rear controllable suspension member having a centered position, said rear controllable suspension member including a controllable centering subsystem for urging said rear controllable suspension member toward its centered position, said method comprising:

causing the vehicle to travel on a route section including a wave portion in the following manner: causing said front ground engaging member to encounter said undulating portion before the rear ground engaging member and causing said front controllable suspension member to exert a force in accordance with said undulating portion;

determining the amplitude of one of the road undulations;

deactivating the centering subsystem of the rear controllable suspension component if the amplitude of the one undulation portion is determined to be less than a first threshold.

2. The method for operating a vehicle according to claim 1, further comprising:

when it is determined that the amplitude of the one undulating portion is greater than a second threshold value, the controllable suspension member is caused to apply a force associated with the one undulating portion before the ground engaging member encounters the undulating portion.

3. A ground vehicle, comprising:

a payload bay;

a front ground engaging member;

a rear ground engaging member; and

a suspension system, the suspension system comprising:

a forward controllable suspension member for applying a force between said forward ground engaging member and said payload bay to modify a distance between said forward ground engaging member and said payload bay, said forward controllable suspension member having a centered position, said forward controllable suspension member including a centering subsystem for urging said forward controllable suspension member toward said centered position, said forward controllable suspension member further including a measurement system for measuring an amplitude of a portion of a roadway undulation encountered by said forward ground engaging member;

a rear controllable suspension member for applying a force between said rear ground engaging member and said payload bay to modify the distance between said rear ground engaging member and said payload bay, said rear controllable suspension member having a centered position, said rear controllable suspension member including a controllable centering subsystem for urging said rear controllable suspension member toward its centered position;

a control circuit responsive to said measurement system for deactivating a centering subsystem of said rear controllable suspension component.

4. A method for operating a vehicle, the vehicle comprising: a payload bay, a first ground engaging member and a second ground engaging member, said vehicle further comprising a suspension system, said suspension system comprising: a first controllable suspension member for applying a force between said first ground engaging member and said payload bay to modify a distance between said first ground engaging member and said payload bay, said suspension system further comprising a second controllable suspension member for applying a force between said second ground engaging member and said payload bay to modify a distance between said second ground engaging member and said payload bay, said first controllable suspension member and said second controllable suspension member each comprising a plurality of associated sensors capable of determining at least one of: vertical acceleration, vertical velocity, vertical offset of the road, suspension displacement and force exerted by the controllable suspension component, the method comprising:

causing the vehicle to travel on a route having undulating portions in the following manner: causing the first ground engaging member to encounter the undulating portion before the second ground engaging member;

detecting said fluctuations with a sensor associated with said first controllable suspension component; and

in accordance with the detection result, the second controllable suspension member is caused to exert a force related to the undulating portion before the second ground engaging member hits the undulating portion.

5. The method for operating a vehicle according to claim 4, further comprising: developing a profile of the road segment based on the detection result.

6. The method for operating a vehicle according to claim 5, further comprising: developing a trajectory design performed by the second controllable suspension component.

7. A method for operating a vehicle, the vehicle comprising: a payload bay and a ground engaging member, said vehicle further comprising a suspension system, said suspension system comprising: a controllable suspension member for applying a force between a ground engaging member and said payload bay to modify a distance between said ground engaging member and said payload bay, said ground controllable suspension member having a centered position, said controllable suspension member comprising a reactive mode of operation and a trajectory planning mode of operation, said method comprising:

causing the vehicle to travel on a road segment having a vertically undulating portion;

determining the amplitude of the fluctuation part;

operating said controllable suspension component in said reactive mode of operation if it is determined that the amplitude of one of said undulating portions is less than a first threshold;

if the amplitude of the fluctuation part is judged to be larger than the first threshold value and smaller than the second threshold value, stopping the operation of the centering system; and

if it is determined that the amplitude of the above-indicated one of the undulating portions is greater than the second threshold value, the controllable suspension member is caused to apply the force associated with the one undulating portion before the ground engaging member hits the undulating portion.