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DE-102024210850-A1 - Control method for an electromechanical steering system of a motor vehicle, computer program product and control unit for a motor vehicle

DE102024210850A1DE 102024210850 A1DE102024210850 A1DE 102024210850A1DE-102024210850-A1

Abstract

The invention relates to a control method (10) for an electromechanical steering system (14) of a motor vehicle (16), a computer program, and a control unit (60) for a motor vehicle (16). The steering system (14) comprises at least one electric motor (18), a sensor (20), and control electronics (11) coupled to the sensor (20) and the electric motor (16). The electric motor (18) is coupled, at least indirectly, to a steering wheel (21) or a steerable wheel (66) of the motor vehicle (16). For a motor torque acting on the electromechanical steering system (14) by the electric motor (18), a corresponding setpoint for the motor torque is determined by a complete control loop (12) of the control electronics (11). The complete control loop (12) is configured to compensate for ripple disturbances by determining a compensation torque with respect to the ripple disturbances in order to suppress the disturbances. The compensation torque forms part of the motor torque setpoint. The overall control loop (12) includes a state observer (26) which is configured to reconstruct ripple disturbances intended for compensation based on disturbance models.

Inventors

  • Thomas Schubert
  • Thiemo Olschewski
  • Dennis Husslein
  • Torsten Junker
  • Emad Farshizadeh

Assignees

  • ZF ACTIVE SAFETY GMBH

Dates

Publication Date
20260513
Application Date
20241112

Claims (10)

  1. Control method (10) for an electromechanical steering system (14) of a motor vehicle (16), wherein the electromechanical steering system (14) comprises at least one electric motor (18), a sensor (20), and control electronics (11) coupled to the sensor (20) and the electric motor (16), wherein the electric motor (18) is coupled at least indirectly to a steering wheel (21) or a steerable vehicle wheel (66) of the motor vehicle (16), whereby a corresponding motor torque setpoint is determined for a motor torque acting on the electromechanical steering system (14) by the electric motor (18) by a complete control loop (12) of the control electronics (11), whereby the complete control loop (12) is configured to compensate for ripple disturbances by determining a compensation torque with respect to the ripple disturbances in order to suppress the disturbance states, wherein the compensation torque constitutes a part of the forms motor torque setpoint, and where the overall control loop (12) has a state observer (26) which is set up to reconstruct wavy disturbances intended for compensation using disturbance models.
  2. Regulatory procedure (10) according to Claim 1 , characterized in that the state observer (26) is configured to reconstruct the wavy disturbances intended for suppression independently of the steering angular velocity.
  3. Regulatory procedure (10) according to Claim 1 or 2 , characterized in that in the overall control loop (12) a disturbance of a controlled system (34) is reconstructed in real time by means of a model, wherein the controlled system (34) has at least one electric motor (18).
  4. Regulatory procedure (10) according to Claim 3 , characterized in that the model for reconstructing the disturbance of the controlled system (34) has a parallel connection of disturbance models for describing different orders (30), wherein the parallel connection for each intended order comprises a disturbance model with a sinusoidal impulse response.
  5. Regulatory procedure (10) according to Claim 3 or 4 , characterized in that the model for reconstructing the disturbance of the controlled system (34) further comprises at least one transmission unit, one sensor (20) and/or other components of the steering system (14).
  6. Control method (10) according to one of the preceding claims, characterized in that the state observer (26) is configured to determine a feedback matrix (53) which has separate partitions (54) that are assigned to separate components of the controlled system (34), wherein the separate partitions (54) are each predetermined for at least one predetermined frequency, and wherein the partitions (54) are interpolated for disturbance frequencies that deviate from the predetermined frequencies.
  7. Control method (10) according to one of the preceding claims, characterized in that a dynamic transfer function is taken into account when determining the compensation torque, wherein the dynamic transfer function is determined by a coupling between an input variable of an actuator of the steering system (14) and a point of attack of the respective wave disturbance.
  8. Control method (10) according to one of the preceding claims, characterized in that the method (10) is designed as a computer-implemented method.
  9. Computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to execute the method according to one of the preceding claims.
  10. Control unit (60) for a motor vehicle (16), wherein the control unit (60) is configured to execute the control procedure (10) according to one of the Claims 1 until 8 to execute.

Description

The invention relates to a control method for an electromechanical steering system of a motor vehicle, a computer program product and a control unit for a motor vehicle. All types of electromechanical steering systems (electric power steering, steer-by-wire, active rear-axle steering, and similar systems) incorporate at least one electric motor. During operation, undesirable undulating disturbances can arise due to manufacturing tolerances, aging, wear, or inherent design characteristics of components, negatively impacting the intended function. This particularly affects the haptic feedback to the driver via the steering wheel. These undulating disturbances can manifest as forces or torques, or as a superimposed component of certain measured variables. All of the aforementioned forms are collectively referred to below as "undulating disturbances." The precise characteristics of the wavy disturbances, i.e., the amplitude amplitude corresponding to the respective frequency of a disturbance and the phase angle of the wavy disturbance with respect to position or angle, can change depending on the operating configuration of the underlying components. Furthermore, the aforementioned characteristics can also differ under identical conditions for various otherwise identical components with respect to their respective operating configurations due to manufacturing tolerances or variations in material properties. This means that the dependencies described above are so complex, at least in some scenarios, that predicting the wavy disturbances is not possible. In contrast, there are also operating configurations where the characteristics of the ripple disturbances are largely deterministic. This generally makes it possible to predict the ripple disturbances expected during operation. This prediction of the ripple disturbances can, in turn, be used to suppress them by applying corresponding counteracting forces or torques, or by adapting the measured variables accordingly. In both cases, measured angles or positions are typically used to model the ripple disturbances as a function of angle or position, and thus to replicate them during operation. The dependence of the respective amplitude and phase angle of the ripple disturbance on different operating configurations can be taken into account, for example, using tables of values, descriptive equations, or characteristic curves. For this approach, the operating configurations are acquired and/or determined using suitable system-internal signals and/or additional measured variables. However, the latter approaches have the disadvantage of requiring significant effort to determine the aforementioned dependencies and to ensure deterministic and sufficiently comparable behavior across different operating configurations and, for example, manufacturing-related variations in components. Furthermore, existing approaches carry the risk that, for certain operating configurations or later during series production, individual components may deviate more than expected from the predicted behavior, despite being identical in type. This can lead to the disturbances not only being insufficiently predicted, but also potentially amplifying their effects instead of attenuating or suppressing them. There is therefore a need to be able to control a steering system in such a way that the suppression of undulating disturbances is possible as comprehensively, efficiently and reliably as possible for all operating configurations of the steering system, while at the same time reducing the effort compared to known approaches. The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are specified in the dependent claims and the subsequent description, each of which, individually or in (sub-)combination, can represent aspects of the disclosure. Some aspects are explained with regard to different variants. However, the features are interchangeable. According to one aspect, the invention relates to a control method for an electromechanical steering system of a motor vehicle. The steering system comprises at least one electric motor, at least one sensor, and at least one control electronic unit coupled to the sensor and the electric motor. The electric motor is coupled, at least indirectly, to a steering wheel or a vehicle wheel of the motor vehicle, in particular directly or indirectly mechanically and/or indirectly electrically. For a torque acting on the electromechanical steering system by the electric motor, hereinafter referred to as motor torque, a corresponding motor torque setpoint is determined by an overall control loop of the control electronics. The overall control loop is designed to compensate for ripple disturbances by determining a compensation torque with respect to these disturbances in order to suppress them. This compensation torque forms part of the motor torque setpoint. The overall control loop includes a state observer configured to re