DE102014206465A1 - Control device for an electromechanical power steering - Google Patents

Abstract

A governor device for a steering device is described in which at least two regulators (1, 2) are used. These can be z. B. process variables of different frequency and / or amplitude ranges.

Description

The present invention relates to a control device for an electromechanical power steering and a steering device with such a control device.

In the majority of currently produced in series electronic power steering (EPS) steering systems requirements of the steering functions, in particular a steering assist force, applied according to the principle of control.

This means that there is no internally closed loop, but a regulation is closed as it were about the driver and the vehicle. This structure means that complex functional measures have to be taken in order to be able to operate the controller stably in every possible situation.

For EPS steering systems not only a steering torque exerted by the driver on the steering device and a steering force, but also the entire system behavior below a steering column, d. H. additional effects, eg. As the inertia and friction of a ball screw (KGT), an engine and other components, are taken into account. As a result, models for designing a high-Q controller used in such a system can become very complex and difficult or impossible to implement on typical EPS steering controllers.

In the publication DE 602 13 436 T2 A control strategy for a power steering system is described that allows control of the driver's steering characteristics. In this case, a first control unit calculates an assist torque applied to a steering gear assembly by a motor. A second control unit may be included in the system to minimize any remaining steering system errors to zero.

Thereby, separation of damping of road disturbances transmitted to the driver from delivery of a target steering wheel resistance torque is achieved.

The publication US 2012 0109466 describes a driver assistance system in which the driver obtains an improved steering feel by detecting a drive force along with a desired friction in a steering device. For this purpose, the steering device is supported by an actuator which is controlled by a reference generator and a control loop. The reference generator is based on a mathematical operating model and has the task of providing a signal in the control loop that corresponds to a desired torque. The control loop includes a regulator that receives the signal from the reference generator and generates an output signal that is provided to a control unit of an engine. The control unit of the motor controls the actuator that acts on the steering device.

In the publication DE 602 01 478 there will be described a steer-by-wire mobility system in which a discrepancy between a home position of a steering wheel for force feedback control and a home position of the vehicle mounted steering system is automatically compensated.

In this case, during a drive in which a steering wheel is rotated continuously in a clockwise and counterclockwise direction, a steering wheel operating angle, which corresponds to the starting position of the steering system, is most frequently used. Accordingly, the larger the steering wheel operating angle, the less frequently it is used. In this case, a frequency of a signal is continuously calculated, which corresponds to the different operating angles of the steering wheel. The operating angle that occurs most frequently is stored in the controller as a new starting position of the steering wheel and brought the steering wheel output position for the force feedback control with the starting position of the steering system in accordance. Once both home positions have been matched, the actuator actuator can be controlled with respect to the new home position.

The object of the present invention, based on the prior art described above, is to provide a control device which makes it possible to simplify a control circuit for controlling a steering device while maintaining the quality and quality of the control and to use more cost-effective components.

In this regard, a control device according to claim 1 and a steering device with such a control device according to claim 8 is provided. The subclaims define further embodiments.

The object of the present invention is achieved by dividing a control device into at least two control loops. A first control loop is controlled by a manual torque controller for controlling a first actual value to a first setpoint value and a second control loop is controlled by an auxiliary force controller for controlling a second actual value to a second setpoint value. wherein an input for receiving the second setpoint of the boost controller is coupled to a controller output of the manual torque controller.

An advantage of the proposed distribution of the control device in two control loops is that each of the two controllers is easier to construct with the same quality than solutions with a controller and thereby a less complex hardware and software can be used, which z. B. facilitates an implementation in a control unit.

In this case, the manual torque controller is preferably set up such that the first actual value and / or the first nominal value have amplitudes below a certain first amplitude threshold value and / or frequencies above a certain first frequency threshold value, and the second actual value and / or the second nominal value of the assisting force controller have amplitudes above one certain second amplitude threshold and / or frequencies below a certain second frequency threshold.

In general, the control of an EPS steering system is usually associated with very high demands on the underlying control system, since reference variables, for. B. actual and setpoints, a broad amplitude and frequency range include and corresponding reference models can be very complex. Therefore, by the above-defined division of the amplitude and / or frequency range on the two controllers, these controllers can be simplified. Each of the two controllers can be designed more easily while maintaining the same quality, using less complex hardware and software.

An exemplary embodiment of a desired value as reference variables of the manual torque controller comprises an auxiliary torque. This auxiliary torque can be used to advantage to improve the driving experience of the driver.

The at least one auxiliary torque of the manual torque controller may comprise, for example, an output signal of a driver assistance function, a signal for influencing the steering torque of the steering column or else a signal of a calculated additional torque. Thus, various influences can be considered.

An advantage of the embodiment of the manual torque controller with such auxiliary moments, it is also that such auxiliary moments are typically represented by signals with low amplitude and high frequency and the manual torque controller, z. B. a control software thereof, together with mathematical reference models can be adapted specifically to this signal range. Accordingly, the implementation for this controller is less complex than for a single overall system controller.

The assist force controller is preferably set up such that the second setpoint value comprises at least one auxiliary power. The at least one auxiliary power may, for example, correspond to a signal of a steering function and / or a signal for influencing a steering force of a steering column.

One possible advantage of this embodiment is that such auxiliary forces can typically be represented by signals with high amplitude and low frequency, and so the assist force controller, for. B. an underlying software together with mathematical reference models, can be adapted specifically to this signal range. Accordingly, the implementation for this controller is less complex than for a single overall system controller.

In addition, the control device may further include a motor controller for controlling or controlling a third actual value to a third setpoint value, wherein the third actual value comprises a moment caused by a motor of a power assistance. In this case, the third set value comprises a signal output by the assist force controller.

An advantage of this control device of the engine governor is that the signal of the servo governor is already acted upon by the manual torque controller and thus the motor controller is a high-quality signal available.

A steering apparatus of the power steering apparatus may include a steering column and a steering torque sensor for detecting a steering torque of the steering column, wherein an output of the steering torque sensor is coupled to an input of the manual torque controller for receiving the first actual value.

With this arrangement, the first actual value can be adjusted to the setpoint value of the calculated moments in such a way that the driver is given an accurate driving feeling.

The steering torque of the steering column can, for. B. are transmitted to a rack, wherein the steering force acting on the rack corresponds to the second actual value.

Thus, the actual value of the steering force can be controlled to the desired value such that the driver is given an accurate driving experience.

The steering device may also include a motor coupled to the rack and controlled by the engine controller.

With the thus configured steering device, the division of the entire regulator device in manual torque controller, assistive force controller and motor controller is advantageously incorporated into a mechanical construction of the steering device.

The invention will be explained in more detail below with reference to the accompanying drawings with reference to embodiments. Show it:

1 a schematic arrangement of a control device for an electromechanical power steering according to an embodiment, and

2 a spatial arrangement of various components of an electromechanical power steering according to an embodiment.

1 shows an embodiment of the invention in which two separate regulators are provided to control an electromechanical power steering.

A manual torque controller 1 is set up, one of a combiner 3 output desired torque M_soll with a measured or estimated actual torque M_act, z. B. from a steering column, and based on the signals M_soll and M_ist, z. B. based on a difference of these signals to calculate an output signal F_R_soll. Such an estimate can be made, for example, that an unknown size to be estimated, here z. B. the actual torque M_ist, is generated by a model. The model can be generated by comparing known quantities that follow a system state of the real system.

The combiner 3 receives signals corresponding to different moments, the z. B. serve to improve the driving characteristics in certain driving situations. In the illustrated embodiment, here is a signal M_Ass_soll from a lane departure warning 20 or a signal M_Feel_soll corresponding to a moment for generating a certain characteristic driving feeling at a corresponding assistance function 21 shown.

In addition, the combiner receives 3 in the illustrated example, a signal M_xxx_soll corresponding to a desired torque from a device 22 , The combiner 3 combined, z. B. added, the signals M_Ass_soll, M_Feel_soll and M_xxx_soll to obtain the target torque M_soll.

The output signal F_R_soll becomes another combiner 4 fed. The other combiner 4 combined, z. B. added, the signal F_R_soll with other signals F_xxx_soll and F_servo_soll to generate a signal F_soll according to a desired force and a support force controller 2 supply.

The support force controller 2 is set up based on an estimated or measured force F_ist z. B. on a rack of a steering device and the output signal F_soll of the other Kombinierers 4 , z. B. Based on a difference thereof, a target torque M_Motor_soll to calculate which a motor controller 5 the steering device is supplied as a reference variable.

The support force controller 2 can be set up to determine the desired torque M_Motor_soll so that the estimated or measured force F_ist is controlled to the desired force F_soll.

The above-mentioned further signals to the further combiner 4 in the illustrated embodiment, include the signal F_Servo_soll from a servo assistance 24 and the signal F_xxx_soll, which is a desired steering force by a device 23 pretends. In other embodiments, other signals may be used.

The engine governor 5 is set up, based on the desired torque M_Motor_soll and a measured or estimated actual torque M_Motor_ist, z. On the basis of a difference thereof, to generate an output signal PWM. With the output signal PWM can then z. B. the engine of the steering device can be controlled. The signal PWM can be a pulse width modulated signal. So the engine controller z. B. the actual torque M_Motor_ist on the target torque M_Motor_soll regulate.

The through the engine regulator 5 implemented motor control can also be realized on the basis of measured or estimated currents with which the electric motor is operated. These currents can be measured with electronic components or estimated from other quantities available in the system (for example voltage, temperature ...). In some embodiments, the engine controller may 5 also implement a control.

In the embodiment, the controllers 1 and 2 controlled only by reference variables that the respective controller 1 respectively. 2 include associated amplitude and frequency ranges. the Hand torque controller 1 In this case, reference variables of low amplitudes and high frequencies are assigned.

The backup force controller 2 On the other hand, high amplitudes and low frequencies are assigned. Clearly, a low amplitude value or a high frequency means a small maximum deflection of the signal, but this signal occurs very often. This is true, for example, for fine steering changes that are relevant to the conveyed character of the driving feel and for improving the driving characteristics in certain driving situations. As an illustrative example here is the signal M_Ass_soll of the lane departure warning 20 or the signal M_Feel_soll for generating a certain characteristic driving feeling.

As examples of low amplitude and high frequency signals are signals 1 to take account of road excitations: here high steering angle velocities (ie high frequencies) can occur, but the maximum steering angle excursions are small (ie small amplitudes).

The division of the controller system into 2 parts described above makes it possible to use two separate controllers 1 . 2 individually designed less complex than would be the case with a design with only a single controller. Accordingly, the functional measures are in each of the two controllers 1 . 2 individually less complex, and requirements for. As to mathematical reference models and thus to the system resources of the controller (eg., The dimensioning of the hardware) lower than in a single system with only one controller. In addition, the reference models can be adjusted more precisely in their respective frequency and amplitude ranges, which means that the controllers can each have at least as high a performance or quality as would be the case in a system with only one controller.

For technical realization of the controller 1 . 2 and 5 PI or PID controllers (proportional-integral derivative controllers) whose technical characteristics and adaptability to a controlled system are suitable for meeting the technical requirements described above can be used very well. There are also regulators, the more complex design method z. B. from the field of optimal control (H_inf) work possible.

2 shows a possible mechanical arrangement of components in the electromechanical power steering according to one embodiment. This is one of a steering torque sensor 11 measured or estimated moment M_act that is on the input shaft or steering column 10 acts with a control unit 14 coupled. A control device according to an embodiment, z. B. as in 1 shown is in a control unit 14 implemented. The moment of the steering column is via a steering pinion 12 on a rack 13 transmitted there and generates a steering force which is part of a sum F_ist of all forces acting on the rack. The force F_ist is z. B. from the controller 14 estimated or measured and z. B. as a reference variable the support force controller 2 fed.

The control unit 14 continues to control an electric motor 15 for example, via the belt 16 with a ball screw drive 17 connected, which is the rack 13 drives. In other possible embodiments of mechanical EPS steering, other types of coupling may be used. For example, a rack-and-pinion electric motor may be used without a belt, or the drive of the rack may be via a second pinion and worm. Other types of mechanical coupling are possible. The electric motor 15 generates a moment M_Motor_ist, which from the control unit 14 is measured or estimated and compared with the calculated moment of the assisting force controller M_Motor_soll, for e.g. B. by the engine controller 5 to form a control signal (PWM signal) for the synchronous motor.

LIST OF REFERENCE NUMBERS

1

Hand torque controller

2

Support force regulator

3

combiners

4

combiners

5

motor controller

10

Input Source / steering column

11

Steering torque sensor

12

steering pinion

13

rack

14

control unit

15

electric motor

16

belt

17

Ball Screw

20

Lane Keeping Assist

21

Assistant generation driving feeling

22

Steering torque on steering column

23

power steering

24

Steering function power assistance

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 60213436 T2 [0005]
• US 20120109466 [0007]
• DE 60201478 [0008]

Claims (10)

A control device for an electromechanical power steering system, comprising: a manual torque controller ( 1 ) for controlling a first actual value (M_act) to a first desired value (M_setpoint) and an assisting force controller ( 2 ) for controlling a second actual value (F_act) to a second desired value (F_setpoint), wherein an input for receiving the second nominal value (F_setpoint) of the assisting force controller ( 2 ) with a controller output of the manual torque controller ( 1 ) is coupled. Control device according to claim 1, characterized in that the manual torque controller ( 1 ) is configured to process the first actual value (M_act) and / or the first desired value (M_setpoint) with amplitudes below a certain first amplitude threshold value and / or frequencies above a certain first frequency threshold value, and the assisting force controller ( 2 ) is arranged to process the second actual value (F_act) and / or the second desired value (F_setpoint) with amplitudes above a certain second amplitude threshold value and / or frequencies below a certain second frequency threshold value. Control device according to claim 1 or 2, characterized in that the first setpoint value (M_soll) as reference variables at least one auxiliary torque ( 3 ). Control device according to claim 3, characterized in that the at least one auxiliary torque ( 3 ) comprises a first auxiliary torque, which corresponds to an output signal (M_ass_soll) of a driver assistance function, and / or a second auxiliary torque ( 3 ), which corresponds to a signal (M_xxx_soll) for influencing the steering torque of the steering column, and / or a third auxiliary torque ( 3 ), which corresponds to a signal of a calculated additional torque (M_Feel_soll). Control device according to one of claims 1-4, characterized in that the second set point (F_soll) at least one auxiliary power ( 4 ). Control device according to claim 5, characterized in that the at least one auxiliary power ( 4 ) comprises: a first auxiliary force corresponding to a signal (F_servo_soll) of a steering function for a power assistance. and / or a second auxiliary force, which corresponds to a signal (F_xxx_soll) for influencing a steering force of the steering column. Control device according to one of claims 1-6, comprising: a motor controller ( 5 ) for controlling or controlling a third actual value (M_Motor_ist) to a third desired value (M_Motor_soll), wherein the third actual value is one of a motor ( 15 ) comprises a servo assist caused moment (M_Motor_ist), and wherein the third set point is one of the assist force controller ( 2 ) output signal (M_Motor_soll). Steering device comprising a control device according to one of claims 1-7, a steering column ( 10 ) and a steering torque sensor ( 11 ) for detecting a steering torque Mist of the steering column ( 10 ), wherein an output of the steering torque sensor ( 11 ) with an input of the manual torque controller ( 1 ) is coupled to receive the first actual value. Steering device according to claim 8, further comprising: a rack ( 13 ), with one on the rack ( 13 ) acting steering force (F_ist) corresponds to the second actual value. Steering device according to claim 8 or 9, further comprising: a motor ( 15 ), with the rack ( 13 ), wherein the control device is designed according to claim 7.

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