JP2019018773A - Suspension control system - Google Patents

Abstract

A suspension control system capable of increasing the estimation accuracy of stroke speed while suppressing the number of sensors to be used is provided. A suspension control system includes a suspension and a control device that estimates a stroke speed. The control device calculates the first stroke speed based on the detected sprung vertical acceleration and unsprung vertical acceleration. Further, the control device calculates the second stroke speed using a single-wheel model observer with one degree of freedom. The complementary filter includes a high-pass filter that removes a low-frequency component of the first stroke speed and a low-pass filter that removes a high-frequency component of the second stroke speed, and these filters have a gain sum in all frequency regions. 1 to be configured. The first stroke speed and the second stroke speed input to the complementary filter are combined after each predetermined frequency component is removed. [Selection] Figure 4

Description

  The present invention relates to a suspension control system, and more particularly to a suspension control system mounted on a vehicle including a suspension that can change a damping force in accordance with a drive current.

  Skyhook damper control using a suspension capable of changing damping force is known. In the skyhook damper control, a relative speed (hereinafter referred to as “stroke speed”) between an unsprung structure and an unsprung structure connected via a suspension is estimated in order to generate a required damping force. There is a need. As a technique for estimating the stroke speed, for example, there is one described in Patent Document 1. This document proposes a method for estimating a stroke speed using a plant model and an observer configured based on a state space of an equation of motion based on a two-degree-of-freedom single-wheel model.

JP-A-2006-2844

  When a two-degree-of-freedom single-wheel model observer is used in the estimation of the stroke speed as in the prior art, there is a problem that the estimation accuracy is high on the high frequency side, but the estimation accuracy is low on the low frequency side. In order to increase the estimation accuracy of the stroke speed in a wide frequency range, for example, three types of sensors are required: a sprung vertical acceleration sensor, a sprung vertical acceleration sensor, and a vehicle height sensor. However, with this configuration, the number of sensors used is large, and there are significant problems in terms of mounting on a vehicle and cost.

  As described above, in the conventional technique, there is still room for improvement in accurately estimating the stroke speed in a wide frequency range with a smaller number of sensors.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a suspension control system capable of increasing the estimation accuracy of stroke speed while suppressing the number of sensors used in a vehicle including a suspension. And

  In order to solve the above problems, the present invention is applied to a suspension control system mounted on a vehicle. The suspension control system is a suspension composed of an absorber and a spring connecting between a sprung structure and an unsprung structure of a vehicle, and a relative speed between the sprung structure and the unsprung structure. And a control device for estimating a stroke speed. The control device includes a sprung vertical acceleration detecting means for detecting the sprung vertical acceleration and a sprung vertical acceleration detecting means for detecting the unsprung vertical acceleration. Here, “sprung vertical acceleration” indicates the vertical acceleration of the sprung structure located directly above the suspension, and “unsprung vertical acceleration” indicates the vertical acceleration of the unsprung structure positioned directly below the suspension. ing. The control device includes first estimating means for outputting a first stroke speed that is an estimated value of the stroke speed based on the sprung vertical acceleration and the unsprung vertical acceleration, and an equation of motion based on a single-wheel model with one degree of freedom. The second estimation means for outputting the second stroke speed, which is the estimated value of the stroke speed, using the observer configured based on the state space, the first stroke speed and the second stroke speed are respectively set to predetermined frequencies. And a complementary filter that calculates an estimated value of the stroke speed by combining the components after removing the components. The complementary filter is configured as a digital filter including a high-pass filter that removes a low-frequency component of the first stroke speed and a low-pass filter that removes a high-frequency component of the second stroke speed. The high-pass filter and the low-pass filter are configured so that the sum of gains becomes 1 in the entire frequency region.

  Further, in order to solve the above problems, the present invention is applied to a suspension control system mounted on a vehicle. The suspension control system is a suspension composed of an absorber and a spring connecting between a sprung structure and an unsprung structure of a vehicle, and a relative speed between the sprung structure and the unsprung structure. And a control device for estimating a stroke speed. The control device includes a sprung vertical acceleration detecting means for detecting the sprung vertical acceleration and a sprung vertical acceleration detecting means for detecting the unsprung vertical acceleration. The control device uses a observer configured based on a state space of an equation of motion based on a two-degree-of-freedom single-wheel model, and outputs a first stroke speed that is an estimated value of a stroke speed; A second estimating means for outputting a second stroke speed, which is an estimated value of the stroke speed, using an observer configured based on a state space of an equation of motion based on a single-degree-of-freedom single wheel model; and a first stroke speed And a complementary filter that calculates an estimated value of the stroke speed by combining the second stroke speed after removing predetermined frequency components. The complementary filter is configured as a digital filter including a high-pass filter that removes a low-frequency component of the first stroke speed and a low-pass filter that removes a high-frequency component of the second stroke speed. The high-pass filter and the low-pass filter are configured so that the sum of gains becomes 1 in the entire frequency region.

  According to the suspension control system of the present invention, the first stroke speed is output as the estimated value on the high frequency side, and the second stroke speed is output as the estimated value on the low frequency side. This makes it possible to accurately estimate the stroke speed in a wide frequency range with a smaller number of sensors.

It is a figure which shows the structure of the vehicle by which the suspension control system which concerns on Embodiment 1 is mounted. It is a figure which shows the model structure of the single-wheel model observer of 1 degree of freedom. It is a control block diagram of a single-wheel model observer. FIG. 3 is a diagram illustrating a configuration of a complementary filter used in the system according to the first embodiment. 4 is a flowchart of a routine that is executed when the ECU estimates a stroke speed of a variable suspension in the system according to the first embodiment. It is a figure which shows the model structure of the single-wheel model observer of 2 degrees of freedom. It is a figure which shows the structure of the complementary filter used in the system of Embodiment 2. FIG. 4 is a flowchart of a routine that is executed when the ECU estimates a stroke speed of a variable suspension in the system according to the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. However, in the embodiment shown below, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the reference However, the present invention is not limited to these numbers. Further, the structures, steps, and the like described in the embodiments below are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

Embodiment 1 FIG.
<System configuration of vehicle according to Embodiment 1>
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a vehicle on which the suspension control system according to the first embodiment is mounted. In the following description, the traveling direction (front-rear direction) of the vehicle 10 is defined as the X direction, the left-right direction of the vehicle 10 is defined as the Y direction, and the vertical direction of the vehicle 10 is defined as the Z direction. In addition, the positive sign of the Z direction is “positive”.

  The vehicle 10 according to the first embodiment includes four wheels 12. Each wheel 12 is provided with a variable suspension 14, a sprung vertical acceleration sensor 16, and an unsprung vertical acceleration sensor 18. The variable suspension 14 includes a tension-dependent variable shock absorber and a spring that can change the damping force according to the drive current. The variable suspension 14 connects the sprung structure (body, etc.) and the unsprung structure (wheels, etc.) of the vehicle 10. Since the structure itself of the variable suspension 14 does not form the gist of the present invention, any structure can be adopted.

The sprung vertical acceleration sensor 16 is disposed in a sprung structure of each wheel 12 of the vehicle 10 and detects acceleration in the vertical direction (Z direction) of the vehicle (hereinafter referred to as “sprung vertical acceleration”). The unsprung vertical acceleration sensor 18 is disposed in the unsprung structure of each wheel 12 of the vehicle 10 and detects acceleration in the vertical direction (Z direction) of the vehicle (hereinafter referred to as “unsprung vertical acceleration”). . In the following description, the vertical displacement (Z direction) displacement above the spring of the variable suspension 14 is Z _b , the vertical displacement (Z direction) displacement below the spring is Z _w , the sprung vertical acceleration is Z _b ″, and the spring The upper vertical speed is _expressed as Z _b ′, the unsprung vertical acceleration is expressed as Z _w ″, and the upper vertical speed is expressed as Z _w ′.

  The vehicle 10 according to the first embodiment includes an ECU 20 as a control device for the variable suspension 14. The ECU 20 estimates the stroke speed of the variable suspension 14 based on signals input from the sprung vertical acceleration sensor 16, the unsprung vertical acceleration sensor 18, and the variable suspension 14. In the following description, the sign of the stroke speed is defined as “positive” for the extension side of the variable suspension 14 and “negative” for the compression side. The ECU 20 controls the drive current value output to the variable suspension 14 so that the posture of the vehicle 10 is stabilized based on the estimated stroke speed.

<Operation of Embodiment 1>
The ECU 20 is configured to execute skyhook damper control using the variable suspension 14. The skyhook damper control individually determines the required damping force of the variable suspension 14 of each wheel 12 so that the posture of the body portion that is the sprung structure of the vehicle 10 is stabilized. The damping force F _fc of the variable suspension 14 varies depending on the stroke speed, which is the relative speed between the sprung structure and the unsprung structure, and the drive current value applied to the variable suspension 14. For this reason, in order to bring the damping force of the variable suspension 14 close to the required damping force, it is required to increase the estimation accuracy of the stroke speed. In particular, in the skyhook damper control using the shock absorber of the tension dependent variable type, the tension reversal occurs when the stroke speed becomes an unsprung resonance frequency of about 10 to 15 Hz. For this reason, it is important to improve the estimation accuracy when the stroke speed becomes the unsprung resonance frequency in order to realize the posture stabilization of the vehicle.

  Here, for estimation of the stroke speed, an estimation method using the sprung vertical acceleration sensor 16 and the unsprung vertical acceleration sensor 18 and an observer (hereinafter referred to as an observer) configured based on a state space of an equation of motion based on a single wheel model. And an estimation method using a “single-wheel model observer”. The system according to Embodiment 1 is characterized by an estimation method that combines these methods. Hereinafter, the stroke speed estimation method will be described in order.

(Estimation method using sprung vertical acceleration sensor and unsprung vertical acceleration sensor)
First, an estimation method using the sprung vertical acceleration sensor and the unsprung vertical acceleration sensor will be described. In systems with sprung vertical acceleration sensor 16 and the unsprung vertical acceleration sensor 18 can be sprung vertical acceleration Z _{b "and} unsprung vertical acceleration Z _w" is calculated from the sensor signal of the acceleration sensor. The integrated values of the sprung vertical acceleration Z _b ″ and the unsprung vertical acceleration Z _w ″ are the sprung vertical speed Z _b ′ and the unsprung vertical speed Z _w ′, respectively. Therefore, by calculating the sprung vertical speed Z _b ′ and the unsprung vertical speed Z _w ′ of each wheel 12 and calculating the difference between them, the stroke speed (Z _b ′) of the variable suspension 14 in each wheel 12 is calculated. −Z _w ′) can be calculated. In the following description, the stroke speed estimated using the sprung vertical acceleration sensor 16 and the unsprung vertical acceleration sensor 18 is referred to as a “first stroke speed”.

(Stroke speed estimation method using a single-wheel model observer)
Next, a stroke speed estimation method using a single-wheel model observer will be described.
Here, a stroke speed estimation method using a single-degree-of-freedom single-wheel model observer that performs feedback of sprung vertical acceleration as a single-wheel model observer will be described.

FIG. 2 is a diagram illustrating a model configuration of a single-wheel model observer having one degree of freedom. In the example of the single wheel model shown in this figure, the sprung mass is M _b , the suspension spring constant is K _s , and the shock absorber base damping coefficient is C _s . Further, in the example of the single-wheel model shown in this figure, the force in the Z direction acting on the variable suspension 14 is f, the vertical displacement on the spring is Z _b , and the vertical displacement on the spring is Z _w .

When the state quantity x is as shown in the following equation (1), the observed quantity y is the sprung vertical acceleration Z _b ″, f is the known input u, and Z _w is the unknown input w: The state equation and observation equation of the single-wheel model with one degree of freedom are expressed as the following equations (2) and (3).

  Here, the coefficient matrices A, B, C, D, G, and H in the above equations (2) and (3) are as follows.

  Next, assuming that the estimated values of the state quantity x and the observation quantity y are x ^ and y ^, respectively, the state quantity estimation equation and the observation quantity estimation equation using the Kalman filter are expressed by the following equations (4) and (5). expressed.

  Here, L is an observer gain, and is determined by the following equation (7) from a solution P that is a positive definite object of the Riccati equation represented by the following equation (6).

FIG. 3 is a control block diagram of the single-wheel model observer. Hereinafter, the configuration of the single-wheel model observer for calculating the estimated value of the stroke speed that is the estimated value x ^ of the state quantity x will be described in more detail with reference to FIG. A force f is input to the single-wheel model observer 30 as a known input u. The force f here is the damping force F _fc of the variable suspension 14. The damping force F _fc varies according to the drive current value supplied to the variable suspension 14 and the stroke speed. The ECU 20 stores a map in which the relationship of the damping force F _fc to the stroke speed is associated with the drive current value. The calculator 32 receives an estimated stroke speed value and a drive current value, which are estimated values x ^ of the state quantity x. The computing unit 32 calculates the damping force F _fc corresponding to the drive current value and the estimated stroke speed according to this map. The damping force F _fc includes a response delay element. For this reason, the damping force F _fc output from the calculator 32 is output as the force f after the first-order lag of the damping force is corrected in the calculator 34.

  The known input u output from the calculator 34 is input to the adder 36 after being multiplied by the coefficient matrix B. In the adder 36, the calculation of Expression (4) is performed, and the time differential value x ^ 'of the estimated value x ^ of the state quantity x is output. The output from the adder 36 is input to the integrator 38. The estimated value x ^ of the state quantity x output from the integrator is multiplied by the coefficient matrix A and then input to the adder 36.

  The estimated value x ^ of the state quantity x output from the integrator 38 is input to the adder 40 after being multiplied by the coefficient matrix C. The product of the known input u and the coefficient matrix D is also input to the adder 40. In the adder 40, the calculation of Expression (5) is performed, and an estimated value y ^ of the observation amount y is output.

The estimated value y ^ of the observation amount y output from the adder 40 is input to the adder 42. The sprung vertical acceleration Z _b ″ as the observation amount y is also input to the adder 42. The adder 42 calculates an estimation error (y− ^) of the observation amount y using these input values. The estimation error (y− ^) is input to the adder 36 after being multiplied by the observer gain L.

It is possible to estimate the state quantity x that cannot be directly measured, that is, the stroke speed (Z _b ′ −Z _w ′) of the variable suspension 14 in each wheel 12 by performing the calculation by the above method for each wheel 12. It becomes possible. In the following description, the stroke speed estimated using the single-wheel model observer with one degree of freedom is referred to as “second stroke speed”.

<Characteristics of Embodiment 1>
Next, features of the first embodiment will be described. The first stroke speed described above includes integration processing in the calculation process. For this reason, the first stroke speed is characterized in that the high frequency estimation accuracy is high but the low frequency estimation accuracy is low. On the other hand, since the second stroke speed described above is calculated using a model of a single-wheel model observer with one degree of freedom, unsprung movement, that is, high-frequency vibration is difficult to be reflected in the model. For this reason, the second stroke speed is characterized in that the estimation accuracy of the low frequency is high but the estimation accuracy of the high frequency is low.

  Therefore, in the system according to the first embodiment, the first stroke speed and the second stroke speed are weighted and added to each other using a complementary filter, so that a stroke with high estimation accuracy at both low frequency and high frequency is obtained. Output speed.

  FIG. 4 is a diagram illustrating a configuration of a complementary filter used in the system according to the first embodiment. Hereinafter, the function of the complementary filter will be described in more detail with reference to FIG.

The sprung vertical acceleration Z _b ″ and the unsprung vertical acceleration Z _w ″ detected using the sprung vertical acceleration sensor 16 and the unsprung vertical acceleration sensor 18 are input to the integrators 50 and 52, respectively. The integrators 50 and 52 calculate the sprung vertical speed Z _b ′ and the unsprung vertical speed Z _w ′, respectively, by integrating the input acceleration. The adder 54 calculates the difference value between the sprung vertical speed Z _b ′ and the unsprung vertical speed Z _w ′ output from the integrators 50 and 52, and outputs it as the first stroke speed Z _s1 ′. Further, the observer 30 receives the input of the sprung vertical acceleration Z _b ″ and outputs the second stroke speed Z _s2 ′.

The complementary filter 60 receives the first stroke speed Z _s1 ′ and the second stroke speed Z _s2 ′. The complementary filter 60 includes a high pass filter (HPF) 602 and a low pass filter (LPF) 604. The complementary filter 60 is configured as a digital filter that synthesizes and outputs values generated by the HPF 602 and the LPF 604. The sum of the gains of HPF 602 and LPF 604 is 1 in the entire frequency region.

The HPF 602 receives the first stroke speed Z _s1 ′, removes low frequency components using a predetermined cutoff frequency, and then outputs the remaining high frequency components. On the other hand, the second stroke speed Z _s2 ′ is input to the LPF 604, the high frequency components are removed using the same cutoff frequency as the HPF 602, and the remaining low frequency components are output. Since the complementary filter 60 adds and outputs these, the first stroke speed Z _s1 ′ is output on the high frequency side, and the second stroke speed Z _s2 ′ is output on the low frequency side. Thereby, it is possible to improve the estimation accuracy of the stroke speed in the entire frequency region.

<Specific processing of the first embodiment>
Next, a specific process executed when the system of the first embodiment estimates the stroke speed will be described with reference to a flowchart. FIG. 5 is a flowchart of a routine executed when the ECU 20 estimates the stroke speed of the variable suspension 14.

In this routine, first, the sensor signal of the sprung vertical acceleration sensor 16 is A / D converted (step S1). In the following description, the A / D-converted values of the sensor signals of the front right, left front, right rear, and left rear sprung vertical acceleration sensors 16 are detected accelerations Z ₁ ″, Z ₂ ″, Z ₃ ″, Z, respectively. ₄ ".

Next, the sprung vertical acceleration at each wheel position is calculated (step S2). Here, first, according to the following equations (8) to (11) using detected accelerations Z ₁ ″, Z ₂ ″, Z ₃ ″, Z ₄ ″, the vertical acceleration Zg ″ of the center of gravity position of the sprung structure, roll acceleration Φg ″ and pitch acceleration Θg ″ are calculated. In the following formulas (8) to (11), L ₁ , L ₂ , L ₃ , L ₄ , and W ₁ , W ₂ , W ₃ , W ₄ are calculated. Represents the position in the X direction and the position in the Y direction of each sprung vertical acceleration sensor 16. Further, L _g and W _g are the gravity center position in the X direction of the sprung structure and the Y direction, respectively. These values L _i , W _i (i = 1, 2, 3, 4), L _g , W _g are fixed values determined from the sensor arrangement and the like, and are stored in the memory of the ECU 20 in advance. The value stored in is used.

Next, in step S2, the sprung vertical acceleration Z _b ″ at each wheel position is calculated. Here, according to the following equation (12), the sprung vertical acceleration Z _bfl ″, immediately above each variable suspension 14 is calculated. _{Z bfr ", Z brl",} Z brr " is calculated. in expression (12), _{T f} is the front of the tread width, _{T r} is the tread width of the rear wheel, _{l f} is the front axle - the distance between the sprung centroid, _{l r} is Kowajiku -. the distance between the sprung centroid these values _{T f, T r, L f} , L r is a fixed value determined from the configuration of the vehicle 10 Therefore, a value stored in advance in the memory of the ECU 20 is used.

Next, the unsprung vertical acceleration Z _w ″ at each wheel position is calculated (step S3). The unsprung vertical acceleration sensor 18 is provided in the unsprung structure directly below the variable suspension 14. Therefore, in this case, the A / D converted values of the sensor signals of the front right, left front, right rear, and left rear unsprung vertical acceleration sensors 18 are the unsprung vertical accelerations Z _wfl ”directly below the respective variable suspensions 14. _{, Z wfr ", Z wrl"} , is the _{Z wrr} ".

Next, the first stroke speed Z _s1 ′ at each wheel position is calculated (step S4). Here, according to the following equations (13) and (14) using the sprung vertical acceleration at each wheel position calculated in step S2 and the unsprung vertical acceleration at each wheel position calculated in step S3: The sprung vertical speed Z _b ′ and the unsprung vertical speed Z _w ′ at each wheel position are calculated. Then, according to the following equation (15), the first stroke speeds Z _s1fr ′, Z _s1fl ′, Z _s1rr ′, and Z _s1rl ′ at each wheel position are calculated.

Next, the second stroke speed Z _s2 ′ at each wheel position is calculated (step S5). Here, the second stroke speed Z _s2 ′ at each wheel position is calculated using a single-degree-of-freedom single-wheel model observer 30 that receives the sprung vertical acceleration at each wheel position calculated in step S2. Is done.

Next, the first stroke speed Z _s1 ′ and the second stroke speed Z _s2 ′ are added using the complementary filter 60 (step S6). Here, the high frequency component of the first stroke speed Z _s1 ′ that has passed through the HPF 602 and the low frequency component of the second stroke speed Z _s2 ′ that has passed through the LPF 604 are added together and output.

As described above, according to the suspension control system of the first embodiment, the high frequency side of the first stroke speed Z _s1 ′ and the low frequency side of the second stroke speed Z _s2 ′ are added together. It is possible to estimate the stroke speed with high accuracy in the entire frequency region without using any additional sensor.

  The suspension control system of the first embodiment may apply a modified form as follows.

  As long as the observer 30 is a single-wheel model observer with one degree of freedom, there is no limitation on how to take the state equation, continuous system, discrete system, or the like.

In the calculation of the first stroke speed Z _s1 ′, the first stroke is calculated by calculating the difference value between the sprung vertical acceleration Z _b ″ and the unsprung vertical acceleration Z _w ″ first and inputting the difference value to the integrator. It may be configured to calculate the speed Z _s1 ′.

  In the suspension control system of the first embodiment, the ECU 20 executes the process of step S2 to realize the “sprung vertical acceleration detecting means” of the first invention, and the ECU 20 executes the process of step S3. Thus, the “unsprung vertical acceleration detecting means” of the first invention is realized, and the ECU 20 executes the process of step S4, thereby realizing the “first estimating means” of the first invention. By executing the processing, the “second estimation means” of the first invention is realized.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to the drawings. The suspension control system of the second embodiment has the same configuration as the suspension control system of the first embodiment, except that the unsprung vertical acceleration sensor 18 is not provided.

<Characteristics of Embodiment 2>
Features of the second embodiment will be described. In the system of the first embodiment described above, the first stroke speed Z _s1 ′ is calculated using the sprung vertical acceleration sensor 16 and the unsprung vertical acceleration sensor 18. This first stroke speed has a feature that high frequency estimation accuracy is high but low frequency estimation accuracy is low. Here, since the two-degree-of-freedom single-wheel model observer has a degree of freedom in the unsprung motion, high-frequency vibration is accurately modeled. For this reason, the stroke speed estimated by using a two-degree-of-freedom single-wheel model observer has a feature that high frequency estimation accuracy is high but low frequency estimation accuracy is low.

In the system according to the second embodiment, the first stroke speed Z _s1 ′ is calculated using the single-wheel model observer 70 having two degrees of freedom using the above-described features. Hereinafter, a stroke speed estimation method using the two-degree-of-freedom single-wheel model observer 70 will be described.

FIG. 6 is a diagram illustrating a model configuration of a two-degree-of-freedom single-wheel model observer. In the example of the two-degree-of-freedom single-wheel model shown in this figure, the sprung mass is M _b , the suspension spring constant is K _s , the shock absorber base damping coefficient is C _s , and the tire spring constant is Kt. In the example of the two-degree-of-freedom single-wheel model shown in this figure, the force in the Z direction acting on the variable suspension 14 is f, the vertical displacement on the spring is Z _b , the vertical displacement on the spring is Z _w , and the road surface The vertical displacement of is Zr.

When the state quantity x is as shown in equation (16), the observed quantity y is the sprung vertical acceleration Z _b ″, f is the known input u, and Z _r is the unknown input w 2 A state equation and an observation equation of a single-wheel model with a degree of freedom are expressed as the following equations (17) and (18).

Here, the coefficient matrices A, B, C, D, G, and H in the above equations (17) and (18) are as follows.

  If the estimated values of the state quantity x and the observation quantity y are x ^ and y ^, respectively, the state quantity estimation equation and the observation quantity estimation equation using the Kalman filter are expressed in the same manner as the equations (4) and (5). Further, L is an observer gain, and is determined from the solution P which is a definite object of the Riccati equation shown in the equation (6) to the following equation (7).

Note that the control block of the two-degree-of-freedom single-wheel model observer 70 has basically the same structure as the control block of the one-degree-of-freedom single-wheel model observer 30 shown in FIG. According to the two-degree-of-freedom single-wheel model observer 70, the state quantity x that cannot be directly measured, that is, the sprung vertical speed Z _b ′ and the unsprung vertical speed Z _w ′ of each wheel 12 can be estimated. These difference values (Z _b ′ −Z _w ′) can be calculated as the first stroke speed Z _s1 ′ of the variable suspension 14.

FIG. 7 is a diagram illustrating a configuration of a complementary filter used in the system according to the second embodiment. As shown in this figure, a two-degree-of-freedom single-wheel model observer 70 receives a sprung vertical acceleration Z _b ″ and outputs a first stroke speed Z _s1 ′. Also, a one-degree-of-freedom single-wheel model The observer 30 receives the input of the sprung vertical acceleration Z _b ″ and outputs the second stroke speed Z _s2 ′.

The complementary filter 60 receives the first stroke speed Z _s1 ′ and the second stroke speed Z _s2 ′. The complementary filter 60 adds and outputs the first stroke speed Z _s1 ′ that has passed through the HPF 602 and the second stroke speed Z _s2 ′ that has passed through the LPF 604. Thereby, it is possible to improve the estimation accuracy of the stroke speed in the entire frequency region.

<Specific Processing of Second Embodiment>
Next, specific processing executed when the system of the second embodiment estimates the stroke speed will be described with reference to a flowchart. FIG. 8 is a flowchart of a routine executed when the ECU 20 estimates the stroke speed of the variable suspension 14.

  In this routine, first, the sensor signal of the sprung vertical acceleration sensor 16 is A / D converted (step S11). Here, specifically, the same processing as in step S1 is executed. Next, the sprung vertical acceleration at each wheel position is calculated (step S12). Here, specifically, the same processing as in step S2 is executed.

Next, the first stroke speed Z _s1 ′ at each wheel position is calculated using the two-degree-of-freedom single-wheel model observer 70 that receives the sprung vertical acceleration at each wheel position calculated in step S2. (Step S13).

Next, the second stroke speed Z _s2 ′ at each wheel position is calculated using a single-degree-of-freedom single-wheel model observer 30 with the sprung vertical acceleration at each wheel position calculated in step S2 as an input. (Step S14).

Next, the first stroke speed Z _s1 ′ and the second stroke speed Z _s2 ′ are added using the complementary filter 60 (step S15). Here, the high frequency component of the first stroke speed Z _s1 ′ that has passed through the HPF 602 and the low frequency component of the second stroke speed Z _s2 ′ that has passed through the LPF 604 are added together and output.

As described above, according to the suspension control system of the second embodiment, the high frequency side of the first stroke speed Z _s1 ′ and the low frequency side of the second stroke speed Z _s2 ′ are added together. It is possible to estimate the stroke speed with high accuracy in the entire frequency region without using any additional sensor. In addition, when calculating the first stroke speed Z _s1 ′ and the second stroke speed Z _s2 ′, the unsprung vertical acceleration sensor and the vehicle height sensor are not required, so the stroke speed can be estimated with a smaller number of sensors with high accuracy. It becomes possible to do.

  The suspension control system according to the second embodiment may be modified as follows.

  As long as the observer 30 is a single-wheel model observer with one degree of freedom, there is no limitation on how to take the state equation, continuous system, discrete system, or the like. Further, if the observer 70 is a two-degree-of-freedom single-wheel model observer, there is no limitation on how to take the state equation, continuous system, discrete system, or the like.

  In the suspension control system of the second embodiment, the ECU 20 executes the process of step S12 to realize the “sprung vertical acceleration detecting means” of the second invention, and the ECU 20 executes the process of step S13. Thus, the “first estimating means” of the second invention is realized, and the “second estimating means” of the second invention is realized by the ECU 20 executing the process of step S14.

10 vehicle 12 wheel 14 variable suspension 16 sprung vertical acceleration sensor 20 ECU
30 One-degree-of-freedom single-wheel model observer 70 Two-degree-of-freedom single-wheel model observer 36, 40, 42, 54 Adder 38, 50, 52 Integrator 32, 34, 46 Calculator 60 Complementary filter 602 High-pass filter (HPF)
604 Low-pass filter (LPF)

Claims (2)

A suspension control system mounted on a vehicle,
A suspension composed of an absorber and a spring connecting the sprung structure and the unsprung structure of the vehicle;
A controller that estimates a stroke speed that is a relative speed between the sprung structure and the unsprung structure, and
The control device includes:
A sprung vertical acceleration detecting means for detecting a sprung vertical acceleration which is a vertical acceleration of the sprung structure positioned directly above the suspension;
Unsprung vertical acceleration detecting means for detecting unsprung vertical acceleration which is vertical acceleration of the unsprung structure located directly under the suspension;
First estimation means for outputting a first stroke speed that is an estimated value of the stroke speed based on the sprung vertical acceleration and the unsprung vertical acceleration;
Second estimating means for outputting a second stroke speed that is an estimated value of the stroke speed, using an observer configured based on a state space of an equation of motion based on a single-degree-of-freedom single-wheel model;
A complementary filter that calculates an estimated value of the stroke speed by combining the first stroke speed and the second stroke speed after removing predetermined frequency components, respectively.
The complementary filter is:
A high pass filter for removing low frequency components of the first stroke speed;
A low pass filter for removing high frequency components of the second stroke speed;
A suspension control system, wherein the high-pass filter and the low-pass filter have a gain sum of 1 in all frequency regions. A suspension control system mounted on a vehicle,
A suspension composed of an absorber and a spring connecting the sprung structure and the unsprung structure of the vehicle;
A controller that estimates a stroke speed that is a relative speed between the sprung structure and the unsprung structure, and
The control device includes:
A sprung vertical acceleration detecting means for detecting a sprung vertical acceleration which is a vertical acceleration of the sprung structure positioned directly above the suspension;
First estimating means for outputting a first stroke speed that is an estimated value of the stroke speed, using an observer configured based on a state space of an equation of motion based on a two-degree-of-freedom single-wheel model;
Second estimating means for outputting a second stroke speed that is an estimated value of the stroke speed, using an observer configured based on a state space of an equation of motion based on a single-degree-of-freedom single-wheel model;
A complementary filter that calculates an estimated value of the stroke speed by combining the first stroke speed and the second stroke speed after removing predetermined frequency components, respectively.
The complementary filter is:
A high pass filter for removing low frequency components of the first stroke speed;
A low pass filter for removing high frequency components of the second stroke speed;
A suspension control system, wherein the high-pass filter and the low-pass filter have a gain sum of 1 in all frequency regions.

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