Steering System Redundancy Control via Voltage-Based Channel Assignment
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Solution Overview
Problem
The existing motor vehicle steering systems with parallel redundant channels experience operating disturbances due to variable power supply conditions, leading to one channel operating in a degraded mode, which affects the driver's feeling and efficiency, and previous solutions either compromise redundancy or reduce assist power.
Innovation Solution
A method that evaluates the channel with the lowest power supply voltage and designates a master and slave channel function to ensure redundancy by adjusting the assist force distribution, allowing the channel with the failed power supply to provide an initial part of the total assist force requirement, with the other channel compensating to meet the total requirement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two independent power supply networks are used to ensure redundancy, then system reliability is improved, but power supply voltage variations cause operating disturbances and degraded performance
Solution Approach 1:
The control system dynamically adjusts the assist force distribution between the two channels based on real-time power supply voltage levels. The method monitors voltage variations and redistributes the assist force requirement adaptively, allowing the system to respond to changing power supply conditions and maintain stable operation without compromising redundancy
Solution Approach 2:
The system changes the operational parameters by adjusting the assist force contribution of each channel according to the power supply voltage status. When one channel experiences voltage drops, the control method modifies the force distribution parameters to compensate, thereby maintaining overall system performance and stability despite power supply variations
2Ease of operation
If the channel with lowest power supply voltage is offloaded to prevent generator mode, then operating disturbances are reduced, but redundancy is lost and driver feeling becomes undesirable
Solution Approach 1:
Instead of completely offloading one channel, the method applies local quality adjustment by distributing the assist force requirement unevenly between channels based on their individual power supply conditions. Each channel contributes according to its capability, with the control system optimizing the local force distribution to prevent generator mode while maintaining overall redundancy and acceptable driver feeling
3Reliability
If power supply voltage of the undisturbed channel is decreased to equalize power supply, then redundancy is maintained, but no-load speed decreases and maximum assist power is reduced
Solution Approach 1:
The control method applies partial action by having the undisturbed channel provide only the necessary complementary assist force rather than operating at full capacity. This allows the channel to contribute enough to meet the total assist force requirement while avoiding the need to reduce its power supply voltage to equalize with the other channel, thereby preserving maximum assist power capability
Data Source
AI summary
A method for controlling a steering system of a motor vehicle, including first and second channels in parallel, each including an electric power unit delivering an assist force to the steering system of the vehicle, in order to obtain the sum of two delivered assist forces, corresponding to the total assist force required, the method including: evaluating the channel having the lowest power unit power supply voltage value; defining a master channel function delivering an initial portion of the total assist force requirement and a slave channel function delivering a variable complementary portion of the assist force, corresponding to the difference between the initial portion of force actually delivered and the total force requirement; and pairing the master channel function with the channel having the lowest power unit power supply voltage value, and the slave channel function with the channel having the highest power unit power supply voltage value.