REGULATING DEVICE AND METHOD FOR REGULATING THE STEERING ANGLE OF A VEHICLE

Abstract

A regulating device for regulating the steering angle of a vehicle includes a first controller unit having at least one integrating component and configured to receive a control difference between first steering angle information, which is deduced from nominal steering angle information, and an actual steering angle. The first controller unit provides actuation information for a motor operating the steering. A compensation control circuit superposed on the first controller unit is provided. The compensation control circuit has a feedback path receives actuation information of the motor, the output torque of the motor, and/or information dependent on the output torque of the motor as the input variable and, based on the input variable, provides steering angle compensation information.

Claims

1. A regulating device for regulating the steering angle of a vehicle, comprising: a first controller unit, the regulating behavior of which has at least one integrating component, wherein the first controller unit is configured to receive a control difference between first steering angle information, which is deduced from nominal steering angle information, and an actual steering angle and to provide actuation information for a motor operating the steering, a compensation control circuit superposed on the first controller unit, wherein the compensation control circuit has a feedback path (4) which receives actuation information of the motor, the output torque of the motor, and/or information dependent on the output torque of the motor as the input variable and, based on said input variable, provides steering angle compensation information, wherein, based on the steering angle compensation information, an adjustment of the nominal steering angle information is effected to the first steering angle information and wherein the control behavior of the compensation control circuit can be modified depending on at least one control variable, wherein the control variable is an influence quantity of the human driver on the steering device and/or a driving situation-dependent measured variable.

2. The regulating device according to claim 1, wherein the first controller unit includes a PID controller.

3. The regulating device according to claim 1, wherein the first controller unit is a self-contained controller unit which does not have an external interface via which the control behavior of the first controller unit can be adjusted.

4. The regulating device according to claim 1, wherein the input variable of the feedback path of the compensation control circuit is at least one of nominal torque information of the first controller unit, the current intensity of the electric current flowing through the motor, and measurement information proportional to the current intensity.

5. The regulating device according to claim 1, wherein the feedback path of the compensation control circuit has a first control element which is configured as a threshold-dependent dead zone.

6. The regulating device according to claim 5, wherein the threshold of the dead zone can be modified depending on the at least one control variable.

7. The regulating device according to claim 5, wherein the regulating device is configured to calculate the threshold of the dead zone based on a first mathematical function depending on the at least one control variable.

8. The regulating device according to claim 1, wherein the feedback path of the compensation control circuit has a second control element which is configured as a low-pass filter.

9. The regulating device according to claim 8, wherein the second control element has a PT1 element or a PT element of a higher order.

10. The regulating device according to claim 8, wherein the control behavior of the second control element can be modified depending on the at least one control variable.

11. The regulating device according to claim 10, wherein the regulating device is configured to calculate the control behavior of the second control element based on a second mathematical function depending on the at least one control variable.

12. The regulating device according to claim 1, wherein the feedback path of the compensation control circuit has a third control element which is configured as a limiter.

13. The regulating device according to claim 12, wherein the limiter has a threshold as of which the amplitude of the output signal is limited and the threshold can be modified depending on the at least one control variable.

14. The regulating device according to claim 13, wherein the regulating device is configured to calculate the threshold of the third control element based on a third mathematical function depending on the at least one control variable.

15. A method for regulating the steering angle of a vehicle with a regulating device which includes a first controller unit having at least one integrating component, wherein the first controller unit receives a control difference between first steering angle information, which is deduced from nominal steering angle information, and the actual steering angle and provides actuation information for a motor operating the steering, wherein a compensation control circuit superposed on the first controller unit is provided with a feedback path, wherein the feedback path receives actuation information of the motor, the output torque of the motor, and/or information dependent on the output torque of the motor as the input variable and, based on the input variable, provides steering angle compensation information, wherein, based on the steering angle compensation information, the nominal steering angle information is adjusted to the first steering angle information and wherein the control behavior of the compensation control circuit is modified depending on at least one control variable, wherein the control variable is an influence quantity of the human driver on the steering device and/or a driving situation-dependent measured variable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The disclosed subject matter is explained in greater detail below on the basis of the figures with reference to exemplary embodiments, wherein:

[0031] FIG. 1 shows by way of example a schematic representation of a control circuit of an electromechanical steering system of a vehicle;

[0032] FIG. 2 shows by way of example a schematic representation of a control circuit of an electromechanical steering system of a vehicle which has a superposed compensation control circuit; and

[0033] FIG. 3 shows by way of example and schematically the control circuit according to FIG. 1, in which a first controller unit is configured as a PID controller.

DETAILED DESCRIPTION

[0034] FIG. 1 shows by way of example a schematic block diagram of a control circuit of a steering device EPS having an electromechanical drive, in which a program-controlled electric motor supports the steering movements of the driver or carries out at least partially inherent steering movements during autonomous or partially autonomous driving.

[0035] In the block wiring diagram, the block designated with the number 2 represents the steering angle controller, the block designated with the number 3 represents the motor and the block designated with the reference numeral 5 represents a control engineering reproduction of the steering mechanics. Together with the motor 3, the steering mechanics form the electromechanical steering device EPS.

[0036] The control circuit obtains, for example, the nominal steering angle φ.sub.soll which is provided for example by an electronic control unit, in particular a computer unit controlling an autonomous or partially autonomous driving function, as input information. The term “nominal steering angle information” is also used here for the nominal steering angle φ.sub.soll.

[0037] Following the subtraction point of the control circuit, at which the nominal steering angle φ.sub.soll is amended based on the actual steering angle φ, a first controller unit 2 is provided, which provides for example a nominal actuating torque T.sub.soll. The first controller unit 2 is for example a PID controller, as depicted by way of example in FIG. 3. In particular, the first control unit 2 has an integrating component. This leads to the nominal actuating torque increasing continually if a difference between the nominal steering angle φ.sub.soll and the actual steering angle φ is adjusted. This is for example the case if the human driver selects a different steering angle at the steering wheel to the nominal steering angle φ.sub.soll over a longer period of time. This results in an unwanted way in a continually increasing steering force which the driver has to exert in order to hold the steering angle that deviates from the nominal steering angle φ.sub.soll. This represents unnatural driving behavior for the driver and is therefore perceived as disturbing.

[0038] The first controller unit 2 is for example a self-contained or enclosed controller unit which does not make possible an interface for supplying external control signals, via which the control behavior could be influenced in a manner that depends on the driving conditions and/or the situation, in particular depending on the driving commands of the human driver. Consequently, it is not possible to compensate for the disturbing control behavior arising inter alia from the integrating component directly at the first controller unit 2.

[0039] The output side of the first control unit 2 is coupled to the motor 3. This is in particular an electric actuator which provides the steering forces for the mechanical steering system of the vehicle. The motor 3 receives a nominal actuating torque T.sub.soll, which is converted by the motor 3 into a motor steering torque T.sub.EPS, from the first control unit 2 for example. The steering torque T.sub.EPS is the actual torque that is transferred by the motor 3 to the steering. The steering torque T.sub.EPS can either be measured directly or can be determined indirectly via the current intensity of the current which flows through the motor 3, since a direct or substantially direct proportionality exists between the current intensity and the steering torque T.sub.EPS produced by the motor.

[0040] In FIG. 1, the reference numeral 5 denotes the mechanical steering system which is schematically depicted as a regulating model. The regulating model of the mechanical steering system 5 can for example be reproduced as an IT.sub.1 element. It firstly contains a point of difference to which the steering torque T.sub.EPS produced by the motor, the disturbance variable d.sub.L and an internal feedback variable, here the first derivative of the steering angle φ′ multiplied by the friction d, is supplied.

[0041] The disturbance variable d.sub.L can be any external disturbance variable (rut, road gradient, transverse forces due to cornering, additional moments which are generated by the motor due to steering assistance functions of the EPS, etc.) and/or the steering torque applied to the steering wheel by the human driver via a steering movement.

[0042] The output variable of the control circuit is the actual steering angle φ, which is fed back to the point of difference lying before the input of the first controller unit 2.

[0043] The disturbance variable d.sub.L is compensated for by the integrating component in the steering angle regulation. This leads to the integrating component being built up. Based on the assumed IT.sub.1 structure, the following is produced for the motor steering torque T.sub.EPS:

T.sub.EPS=j{umlaut over (φ)}+d{dot over (φ)}+d.sub.L.  (Formula 1)

[0044] It is obvious from formula 1 that the disturbance variable d.sub.L leading to the buildup of the integrating component is also reflected in the steering torque T.sub.EPS produced by the motor. I.e., the feedback of the steering torque T.sub.EPS produced by the motor is suitable for compensating for the buildup of the integrating component in the first controller unit 2.

[0045] Alternatively, it is also possible to use the nominal actuating torque T.sub.soll, instead of or in addition to the steering torque T.sub.EPS produced by the motor, as the variable to be fed back, since the nominal actuating torque T.sub.soll also contains information about the integrating component which is building up. This is in particular advantageous if no information regarding the current steering torque T.sub.EPS produced by the motor is available, at least temporarily.

[0046] The following transfer function is thus produced for the control circuit according to FIG. 1 in conjunction with FIG. 3:

φ/φ.sub.soll=Ds.sup.2+Ps+1/J.sub.s.sup.3+(d+D)s.sup.2+Ps+1;  (Formula 2)

[0047] FIG. 2 shows a regulating device 1, in which the control circuit shown in FIG. 1 is superposed by a compensation control circuit having a feedback path 4 in order to be able to mitigate or prevent the disturbing effects of the steering angle regulation if, due to lack of influence possibilities, this is not directly possible at the first controller unit 2.

[0048] In the exemplary embodiment shown, the steering torque T.sub.EPS produced by the motor is supplied to the feedback path 4 of the compensation control circuit as the input variable. Alternatively, as explained above, the nominal actuating torque T.sub.soll can also be used as the input variable. The feedback path of the compensation control circuit provides steering angle compensation information as the output variable. Said information is supplied to a subtraction point, so that the first steering angle information φ′.sub.soll, also referred to as compensated nominal steering angle information, arise from the nominal steering angle information φ.sub.soll by subtracting the steering angle compensation information. This first steering angle information φ′.sub.soll should then in turn serve as input information for the control circuit of the steering device EPS.

[0049] The feedback path 4 of the compensation control circuit can contain one or more control elements, by means of which different regulating functions are executed. It is understood that even more complex regulating structures can be used, which illustrate the functionality of multiple control elements in a physical controller.

[0050] In the exemplary embodiment shown, three control elements 4.1, 4.2, 4.3 are provided. It is understood that this purely serves as one example and more or fewer regulating elements can also be provided.

[0051] The first control element 4.1 is for example configured as a dead zone, i.e., an output signal deviating from zero is not output until the input signal of the first control element 4.1 has exceeded or fallen below a threshold. After exceeding the threshold, there can be a linear relationship between the input information and the output information. The threshold as of which the compensation control circuit should become active can therefore be specified by the first control element 4.1.

[0052] The threshold of the first control element 4.1 can be modifiable, and indeed preferably depending on one or more control variables s.

[0053] The at least one control variable s can either be transferred directly to the first control element 4.1 as the input variable or can be converted into control information which is dependent on the control variable s via a first mathematical function f.sub.1(s), which control information is then transferred to the first control element 4.1 in order to modify the threshold.

[0054] The feedback path 4 of the compensation control circuit can have a further, second control element 4.2 which preferably receives the output information of the first control element 4.1 as input information. The second control element 4.2 has a transfer function GT which has low-pass behavior for example. The second control element 4.2 can be configured for example as a PT.sub.1 element or as a PT.sub.x element of a higher order (i.e., x∈{2, 3, 4, . . . }). Other regulating functions with low-pass behavior are also fundamentally conceivable. Components above a cutoff frequency are filtered out by the low-pass behavior. As a result, low-frequency components, i.e., slow changes in the steering angle come into play to a greater extent so that the cause for the growing nominal actuating torques resulting from the integrating component is therefore back-coupled and, as a result, a more natural steering behavior is achieved. Alternatively, other transfer functions for example can also be used, for example those that arise from standard design methods such as e.g., pole-zero compensation, state controller, etc.

[0055] The control behavior of the second control element 4.2 can be modifiable, and indeed preferably in turn depending on one or more control variables s.

[0056] The at least one control variable s can either be transferred directly to the second control element 4.2 as the input variable or can be converted into control information which is dependent on the control variable s via a second mathematical function f.sub.2(s), which control information is then transferred to the second control element 4.2 in order to modify the control properties.

[0057] The feedback path 4 of the compensation control circuit can have a further, third control element 4.3 which preferably receives the output information of the second control element 4.2 as input information. The third control element 4.3 can for example be configured as a limiter, also referred to as a saturation element. The limiter preferably serves to restrict the amplitude of the feedback information (in particular the output signal of the second control element 4.2) in order to avoid feedback values which are too high for safety reasons.

[0058] The third control element 4.3 preferably has a threshold as of which the amplitude is limited. This threshold can be modifiable, and indeed preferably depending on one or more control variables s.

[0059] The at least one control variable s can either be transferred directly to the third control element 4.1 as the input variable or can be converted into control information which is dependent on the control variable s via a third mathematical function f.sub.3(s), which control information is then transferred to the third control element 4.3 in order to modify the threshold.

[0060] One or more monotonically nondecreasing or nonincreasing functions can be used as the first to third mathematical functions f.sub.1(s) to f.sub.3(s), which functions influence the influence of the at least one control variable s on the respective control element 4.1 to 4.3. Deviating from the monotonically nondecreasing or nonincreasing functions indicated, other types of functions can also be used, for example quadratic functions.

[0061] In the event that multiple different control variables s are used, the mathematical functions f.sub.1(s) to f.sub.3(s) can also have multiple functional parts, wherein one control variable s is used in each case as the input variable for a functional part and, as a result, the overall result of the respective mathematical function f.sub.1(s) to f.sub.3(s) can be influenced by multiple control variables.

[0062] One or more of the items of information indicated below can be used as the control variable s: [0063] The steering torque applied by the human driver to the steering wheel. The width of the dead zone can therefore be decreased for example as the steering torque of the human driver increases in order to thereby avoid the driver being corrected by the first controller unit 2 as a disturbance. [0064] The steering angle speed, i.e., the speed with which the steering angle is changed, in order to decrease the threshold of the dead zone, i.e., the width of the dead zone, as the steering speed increases, and to optionally increase the amplification of the transfer function GT of the second control element 4.2 and thus avoid an overshoot on the basis of the too heavily loaded I component. [0065] The bend curvature (i.e., the reciprocal of the bend radius of the bend driven through), in order to decrease the threshold of the dead zone, i.e., the width of the dead zone, and thus avoid oscillations, as the bend curvature lowers. [0066] The vehicle speed, in order to be able to make the adaptions of the control elements 4.1 to 4.3 at least partially speed-dependent.

[0067] The disclosed subject matter has been described above with reference to exemplary embodiments. It is understood that numerous amendments and variations are possible, without departing from the scope of protection defined by the claims.