Method and device for operating a steering system of a motor vehicle

Abstract

The invention relates to a method and a device for operating a steering system of a motor vehicle, the method for operating a steering system (1) with an electromechanical steering intervention system (10), which has a plurality of redundant control paths (11a, 11b), wherein each control path (11a, 11b) has a control unit (12a, 12b), a power unit (13a, 13b) and a winding circuit (14a, 14b) of a servo motor, wherein an adjustment parameter unit (15a, 15b) is provided in each control unit (12a, 12b) in order to provide an adjustment parameter (S a , S b ) according to input parameters, wherein the adjustment parameters (S a , S b ) of all adjustment parameter units (15a, 15b) are averaged, and wherein a nominal adjustment parameter (S a理论 , S b理论 ) is provided by each control unit (12a, 12b) according to the averaged adjustment parameter.

Description

Field of the Invention

[0001] The present invention relates to a motor vehicle, in particular a motor vehicle with an automatic steering system for automatically fulfilling steering requirements. Background Art

[0002] Electromechanical steering systems are used in motor vehicles to generate an electrically generated steering torque or an electrically generated steering force. Such steering systems are used, for example, to implement driver assistance functions (such as lane keeping assistance), to take over partial tasks during driving operations (such as during parking steering assistance), or to autonomously adjust the steering position of the wheels in a steer-by-wire system.

[0003] For all these functions, the desired steering requirements are implemented and a theoretical adjustment parameter (Soll-Stellgroesse) is provided in the form of a corresponding theoretical adjustment torque or a corresponding theoretical adjustment force. The theoretical adjustment parameter is often provided by means of a regulator, such as a steering position regulator (Lenkstellungsregler), etc.

[0004] Since the proper functioning of the steering system is critical for safety, the steering system is constructed either completely or partially redundantly. In particular, a fully redundant construction is required for steer-by-wire systems, because in the event of a failure of the steering system, there are no alternative intervention possibilities for the driver due to the lack of a mechanical connection between the steering wheel and the steered wheels.

[0005] In principle, two concepts are known for the redundant design of steering control. In the master / slave concept, the steering system is controlled via a master control path. Additionally, a redundant slave control path is provided. In the event of a failure of the master control path, the slave control path takes over the control of the steering servo motor (Lenkstellmotor). In the so-called master / master concept, a plurality of equal control paths are provided for controlling a plurality of steering servo motors or a single steering servo motor with a plurality of separate winding circuits (Wicklungskreis). Although only a reduced adjustment torque is available for the steering adjustment movement in the event of a failure of one of the control paths, a total failure (Totalausfall) is avoided.

[0006] A redundant controller for an electromechanical steering system for a motor vehicle is known from document DE 10 2018 108 597 A1, which has a main control path and a secondary control path. The main control path has a main computing unit, a main driver stage (Treiberstufe), and a main power module, while the secondary control path correspondingly has a secondary computing unit, a secondary driver stage, and a secondary power module. The power module is used to control two physically separated electric motors or a single electric motor with two winding groups. Torque can be applied to the same shaft through these two physically separated torque generators. Additionally, communication between the two control paths is provided via signal lines directly between the computing units.

[0007] In the master / master concept for constructing a steering controller, regulating signals are generated equally for multiple winding circuits of one or more steering servo motors. This can lead to different theoretical regulation parameters due to deviations between the independently determined input signals used, which results in different regulating torques or different regulating forces being provided in these multiple winding circuits. Since two theoretical regulation parameters are correspondingly considered in the positioning of the steering system, the winding circuits can also generate interacting regulating forces or regulating torques if necessary. This is particularly applicable if the theoretical regulation parameters are generated based on a regulation that optionally has an integrator part (Integratoranteil). There, small regulating deviations with different signs on the two control paths can then accumulate and thus lead to regulating torques or regulating forces in different directions. SUMMARY OF THE INVENTION

[0008] Accordingly, it is an object of the present invention to provide an improved method for operating a steering system, which is constructed with a control according to the master / master concept. In particular, interacting control paths should be avoided.

[0009] The object of the present invention is achieved by a method according to the present invention for operating a steering system of a motor vehicle and by a device and a steering system according to the present invention.

[0010] Further embodiments are described in the description.

[0011] According to a first aspect, there is provided a method for operating a steering system with an electromechanical steering intervention system, which has a plurality of redundant control paths, wherein each control path has a control unit, a power unit, and a winding circuit of a servo motor, wherein an adjustment parameter unit is provided in each control unit to provide adjustment parameters according to input parameters, wherein the adjustment parameters of all adjustment parameter units are averaged, and wherein each control unit provides a theoretical adjustment parameter according to the averaged control quantity.

[0012] In particular, the average adjustment parameter can be transmitted as the theoretical adjustment parameter to the power unit of the relevant control path accordingly.

[0013] In a master / master concept for the control of a steering system, two or more than two equal control paths are provided, each of which includes a control unit for providing a theoretical control variable for a power unit to convert the theoretical control variable into a corresponding motor actuation, and a winding circuit for generating an adjustment torque corresponding to the theoretical adjustment parameter or an adjustment force corresponding to the theoretical adjustment parameter. The winding circuit can be arranged in one or more steering servo motors.

[0014] Due to deviations in the input parameters of the equal control paths, for example due to differently (i.e., at other times, by other sensors) measured steering positions or steering angles, optionally longitudinal- and lateral accelerations (depending on the adjustment concept) and rack positions, the control unit can generate different theoretical control variables, which result in different adjustment torques / adjustment forces generated by the winding circuit. In addition, deviations in the measured steering movement speed or steering angular speed can also be relevant for cascaded regulators.

[0015] Depending on the functional scope performed by the control unit, small deviations in the input parameters with different signs in the two control paths can accumulate, so that theoretical adjustment parameters with different signs can be formed. The sum of the adjustment torques is usually correct here and corresponds to the goal of the implemented control function. However, the winding circuit consumes unnecessarily much electrical energy here because of the interaction of its actual adjustment torques / adjustment forces. Due to excessive thermal stress, the availability and service life of the components of the control path can be negatively affected.

[0016] Therefore, according to the above method, it is provided to supply the theoretical adjustment parameters of a plurality of control paths (which are provided at the output of the respective control unit) to other control paths accordingly. The control path is then set to perform the averaging of these two adjustment parameters and to generate the corresponding adjustment torque / adjustment force.

[0017] Therefore, the interaction of the control paths can be prevented because the averaging of the two theoretical adjustment parameters is performed at the level of digital data processing without torque- or force superposition.

[0018] In particular, the adjustment parameter unit can correspondingly have an adjustment with an integrator component, in particular a steering position adjustment, where the integrator component is operated accordingly based on the average adjustment parameter. In addition, the difference between the theoretical adjustment parameter and the actual adjustment parameter can be used to influence the integrator component.

[0019] In particular, the integrator share of the steering position adjustment can cause the theoretical adjustment parameters of these two control paths to deviate from each other and thus result in different signs of the adjustment parameters. Even small adjustment deviations with different signs in the two control paths are accumulated, thus forming increased theoretical adjustment parameters with different signs.

[0020] This negatively affects the regulator dynamics of the regulation. By considering the average theoretical adjustment parameter in the integrator share, the regulations executed in multiple control units limit each other and prevent excessive differences between the integrator shares and thus excessive deviations of the theoretical adjustment parameters. By influencing the integrator share by means of the difference between the average theoretical adjustment parameter and the theoretical adjustment parameter of each control path, the integrator share of the regulation is reduced. This can reduce or avoid the so-called windup effect of the integrator of the regulation.

[0021] By considering the average theoretical adjustment parameter as the output of the control unit, the dispersion of the theoretical adjustment parameters from each other can be resisted, so that opposite adjustment torques or adjustment forces are not caused by the corresponding winding circuits.

[0022] It can be set that the difference between the theoretical adjustment parameter and the adjustment parameter is weighted. By setting the weighted feedback of the difference between the theoretical adjustment parameter output in each control path and the average theoretical adjustment parameter, the influence of the averaging of the theoretical adjustment parameter on the corresponding integrator share can be adjusted.

[0023] It can be set to control the integrator share based on events in order to achieve anti-saturation.

[0024] This can be achieved, for example, by setting (freezing) the integration to a suitable value and temporarily suspending the integration if one or more of the following criteria are met:

[0025] - Exceeding a certain deviation between the theoretical adjustment parameters;

[0026] - Below a certain adjustment difference and

[0027] - Reaching the saturation limit.

[0028] After the integrator is reset, it can be set to the average value of the integrator shares of the two control paths or to a preset value deviating from the average value in order to optimize the dynamics in the saturation characteristic.

[0029] According to a further aspect, a steering system for operating an electromechanical steering intervention system is provided, which has a plurality of redundant control paths, wherein each control path has a control unit of a servo motor, a power unit, and a winding circuit, and wherein an adjustment parameter unit is provided in each control unit for providing an adjustment parameter based on an input parameter, and wherein the control paths are configured to average the adjustment parameters of all adjustment parameter units and to provide a setpoint adjustment parameter through each control unit based on the averaged adjustment parameter.

[0030] According to a further aspect, a steering system for steering a wheel of a motor vehicle is provided, which has one or more servo motors and / or one or more winding circuits for generating a steering force or a steering torque and has the above-described device. Description of the Drawings

[0031] The embodiments will be explained in detail hereinafter with reference to the drawings. Among them:

[0032] Figure 1 A schematic view of a steering system for a motor vehicle is shown;

[0033] Figure 2 A block diagram of a control system with two control paths for providing a steering adjustment torque is shown;

[0034] Figure 3 A block diagram of a steering control system according to a further embodiment is shown, in which an adjustment parameter difference is taken into account in the adjustment parameter unit; and

[0035] Figure 4 A block diagram of a steering control system according to a further embodiment is shown, in which an adjustment parameter difference is taken into account in the adjustment parameter unit and in the extraction of a change in the adjustment parameter. Detailed Description of the Embodiments

[0036] Figure 1 A steering system 1 with an electromechanical steering intervention system 10 is shown schematically. The steering system 1 has a steering transmission 3, which has a pinion 4 and a rack 5 for transmitting a manual steering torque or a manual steering force applied manually, for example via a steering wheel 6 and a steering shaft 7, to the rack 5. The rack 5 is connected to the steered wheels 8 in order to steer them according to the position of the steering shaft 7.

[0037] The electromechanical steering intervention system 10 of the steering system 1 enables the application of an electrically generated steering torque or steering force for steering support or for fully automatically adjusting the steering position, especially in autonomous driving or in an automatic shunting process.

[0038] The steering intervention system 10 has two (as shown in the illustrated embodiment) or more redundant control paths 11a, 11b, each having a control unit 12a, 12b, a power unit 13a, 13b, and a winding circuit 14a, 14b of one or more servo motors controlled by the power unit 13a, 13b. The control units 12a, 12b are in communication connection.

[0039] The winding circuits 14a, 14b can be arranged in separate servo motors or separately in a common servo motor. In the illustrated embodiment, two servo motors act on the steering shaft to apply an adjustment torque there. In an alternative embodiment, the servo motor can also act directly on the rack and apply a steering force there.

[0040] The power units 13a, 13b are used to provide a generally digitally provided theoretical adjustment parameter as an electrical control signal for the winding circuits 14a, 14b, such that the winding circuits provide a corresponding steering torque to the steering shaft or a corresponding steering force to the rack.

[0041] In Figure 2 is schematically and exemplarily shown Figure 1 an embodiment of the steering intervention system 10. A first control path 11a with a first control unit 12a, a first power unit 13a, and a first winding circuit 14a of a servo motor is identified, as well as a second control path 11b with a second control unit 12b, a second power unit 13b, and a second winding circuit 14b of a common servo motor or a separate servo motor.

[0042] The first and second control units 12a, 12b respectively provide theoretical adjustment parameters S a理论 , S b理论 , which are a theoretical adjustment force or a theoretical adjustment torque.

[0043] The control units 12a, 12b in the illustrated embodiment have a first or second adjustment parameter unit 15a, 15b, which generates the adjustment parameters S a , S b , and controls the power units 13a, 13b according to the adjustment parameters.

[0044] Now, in averaging elements 16a, 16b, the respectively provided first adjustment parameter S a of the adjustment parameter units 15a, 15b is averaged with the second adjustment parameter S b . Now, the averaged adjustment parameter is used as the corresponding theoretical adjustment parameter S a理论 , S b理论is fed to the corresponding power units 13a, 13b. This enables a reduction in the system deviation between the theoretical adjustment parameters S a理论 , S b理论 and in particular avoids the adjustment parameter S a , S b from causing a regulating force or regulating torque to be formed conversely in the winding circuits 14a, 14b due to minute deviations accumulated in the adjustment parameter units 15a, 15b. In particular, this avoids excessive heating of the power units 13a, 13b and the winding circuits 14a, 14b, because the averaging of the adjustment parameters S a , S b takes place at the software level without torque - or force superposition.

[0045] Another embodiment of the steering intervention system 10 is shown in Figure 3 . There, a steering position adjustment is implemented in the adjustment parameter units 15a, 15b, which has at least one integrator. The steering position adjustment can here have a PI regulator or a PID regulator and is adjusted to a preset theoretical steering position. Other forms of regulating structures with an integrator component can also be applied.

[0046] Here, the averaged adjustment parameter is fed to the difference elements (Differenzglied) 17a, 17b accordingly in order to calculate the difference between the averaged adjustment parameter and the adjustment parameter S a , S b produced by the respective adjustment parameter units 15a, 15b, and this adjustment parameter difference is fed to or taken into account by the integrator of the regulation implemented in the adjustment parameter units 15a, 15b. For this purpose, the averaged adjustment parameters S a , S b and the averaged adjustment parameter of each regulation path are subtracted from each other and the integrator component is loaded. In this way, only the deviation in the respective difference elements 17a, 17b can be used to load the integrator component of the regulation implemented in the respective adjustment parameter units 15a, 15b. This enables the difference corresponding to the deviation of the two theoretical adjustment parameters S a理论 , S b理论 output by the control unit to compensate the integrator component. This effectively prevents saturation of the integrator component.

[0047] It can be set to control the integrator component based on events in order to achieve anti - saturation. For this purpose, the integration can be set (frozen) to a suitable value and the integration can be temporarily aborted if one or more of the following criteria are met:

[0048] - Exceeding a certain deviation between the theoretical adjustment parameters;

[0049] - Falling below a certain regulation difference and

[0050] - Reach the saturation limit.

[0051] After the integrator is reset, it can be set to the average value of the integrator shares of the two control paths or to a preset value deviating from this average value in order to optimize the dynamics in the saturation characteristic.

[0052] Furthermore, on the one hand, this variant prevents the integrator shares from dispersing from each other and the occurrence of residual deviations (which are caused, for example, by the proportional share of the steering position regulation), and on the other hand, the theoretical regulation parameter can be reduced by averaging.

[0053] If necessary, the averaged regulation parameter can be weighted with respect to the respective regulation parameter S a , S b actually generated by the respective regulation parameter units 15a, 15b, so that the influence on the integrator shares can be adjusted in this way.

[0054] Alternatively, as shown in the steering intervention system 10 of the block circuit diagram in Figure 4 , for controlling the power units 13a, 13b, the regulation parameters S a , S b directly output by the respective control units 12a, 12b can be used, because this output is directly based on the regulation output taking into account the integrator shares of the steering position regulation. That is, the averaged regulation parameter is not used to control the power units 13a, 13b, but the regulation parameters S a , S b are directly applied, which calculate the integrator shares based on the averaged regulation parameter as described above. This reduces the running time within the regulation loop of the respective control unit, because this averaging corresponds to a kind of filtering.

[0055] List of reference numerals

[0056] 1 Steering system

[0057] 3 Steering transmission

[0058] 4 Pinion

[0059] 5 Rack

[0060] 6 Steering wheel

[0061] 7 Steering rod

[0062] 8 Steered wheel

[0063] 10 Electro-mechanical steering intervention system

[0064] 11a, 11b First and second control paths

[0065] 12a, 12b First and second control units

[0066] 13a, 13b First and second power units

[0067] 14a, 14b Winding circuits

[0068] 15a, 15b First and second regulating parameter units

[0069] 16a, 16b Averaging elements

[0070] 17a, 17b Differential element S a理论 , S b理论 Theoretical regulating parameter

[0071] S a , S b Regulating parameter.

Claims

1. A method for operating a steering system (1) with an electromechanical steering intervention system (10), which has a plurality of redundant control paths (11a, 11b), wherein, Each control path (11a, 11b) has a control unit (12a, 12b), a power unit (13a, 13b) and a winding circuit (14a, 14b) of the servo motor, wherein an adjustment parameter unit (15a, 15b) is provided in each control unit (12a, 12b) to provide an adjustment parameter (S a , S b ) according to the input parameter, wherein the adjustment parameters (S a , S b ) of all the adjustment parameter units (15a, 15b) are averaged, and wherein a theoretical adjustment parameter (S a理论 , S b理论 ) is provided by each control unit (12a, 12b) according to the averaged adjustment parameter, wherein the adjustment parameter units (15a, 15b) each have an adjustment with at least one integrator fraction, and wherein the integrator fraction is influenced according to the averaged adjustment parameter, and wherein the integrator fraction is operated with the difference between the theoretical adjustment parameter (S a理论 , S b理论 ) and the adjustment parameter (S a , S b ).

2. The method according to claim 1, wherein The average of the adjustment parameters is used as the theoretical adjustment parameter (S a理论 , S b理论 ) and is correspondingly transmitted to the power units (13a, 13b) of the relevant control paths (11a, 11b).

3. The method according to claim 1 or 2, wherein The adjustment parameter units (15a, 15b) each have a steering position adjustment with at least one integrator component accordingly.

4. The method according to claim 1 or 2, wherein, The difference between the theoretical adjustment parameter (S a理论 , S b理论 ) and the adjustment parameter (S a , S b ) is weighted.

5. The method according to claim 1 or 2, wherein The integrator component is controlled based on an event in order to achieve anti-windup.

6. A device for operating a steering system (1) with an electromechanical steering intervention system (10), having a plurality of redundant control paths (11a, 11b), wherein, Each control path (11a, 11b) has a control unit (12a, 12b), a power unit (13a, 13b), and a winding circuit (14a, 14b) of a servo motor, wherein an adjustment parameter unit (15a, 15b) is provided in each control unit (12a, 12b) to provide an adjustment parameter (S a , S b ) according to an input parameter, wherein the control paths (11a, 11b) are configured to average the adjustment parameters (S a , S b ) of all the adjustment parameter units (15a, 15b) and to provide a setpoint adjustment parameter (S a理论 , S b理论 ) by each control unit (12a, 12b) according to the averaged adjustment parameter, wherein the adjustment parameter units (15a, 15b) each have an adjustment with at least one integrator component, wherein the integrator component is influenced according to the averaged adjustment parameter, and wherein the integrator component is run with the difference between the setpoint adjustment parameter (S a理论 , S b理论 ) and the adjustment parameter (S a , S b ).

7. A steering system (1) for steering a wheel of a motor vehicle, having a servo motor for generating a steering force or a steering torque and having the device according to claim 6.

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