Servo Motor Control for Electric Steering Friction Compensation
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Solution Overview
Problem
Conventional electric vehicular steering systems face inefficiencies due to system-inherent friction, which limits the effectiveness of superposition moments in assisting steering, especially when using automatic lane assist systems, as the maximum superposition moment values are insufficient to induce effective steering motions.
Innovation Solution
A method for controlling a servo motor in electric vehicular steering systems that compensates for system-inherent friction by modifying the superposition moment based on detected driver steering and superposition moments, ensuring the modified superposition moment is larger than the original, thereby enhancing the motor moment and improving steering actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum superposition moment is limited to a predeterminable value for safety reasons, then driver control is ensured, but effective steering motion hardly occurs due to system friction
Solution Approach 1:
The control method performs preliminary compensation for friction by determining a modified superposition moment that is larger than the originally requested superposition moment. This preliminary adjustment ensures that when the moment is applied through the friction-prone mechanical system, the effective steering motion remains sufficient while still maintaining driver override capability.
Solution Approach 2:
The invention changes the parameter of the superposition moment by introducing a modified version that compensates for friction losses. The control unit determines a modified superposition moment based on the originally requested moment, effectively adjusting the moment parameter to overcome friction without exceeding safety limits.
2Ease of operation
If a non-linear amplification function is used to generate assistance moment from driver steering moment, then steering assistance is provided, but the effectiveness is reduced by system-inherent friction
Solution Approach 1:
The invention applies parameter changes by modifying the superposition moment to compensate for friction. The control unit determines a modified superposition moment that is larger than the originally requested moment, adjusting the moment parameter to ensure effective steering actuation despite friction losses in the mechanical system.
Solution Approach 2:
The control method incorporates feedback by using the originally requested superposition moment to determine the modified superposition moment. The system continuously monitors the requested moment and adjusts the modified moment accordingly, creating a feedback loop that compensates for friction effects in real-time.
Data Source
AI summary
A method comprising the steps: a manually applied driver steering moment is detected; a requested superposition moment is detected; the driver steering and superposition moments are combined to form an intermediate moment from which an assistance moment is generated by means of a predefined, non-linear amplification function; starting from detected values of the driver steering and superposition moments, a modified superposition moment compensating for friction in the electric steering system at least in part is determined such that the amount of the modified superposition moment is larger than the amount of the superposition moment at least for some pairs of variates comprised of driver steering and superposition moments; the assistance and modified superposition moments are combined to form a motor moment from which a corresponding input signal for a servo motor is established; the servo motor is controlled with the established input signal to provide the motor moment.