Electric Power Steering Motor Control with Dynamic Road Reaction
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Solution Overview
Problem
Existing motor control devices for electric power steering systems face challenges in reducing the risk of accidents due to a driver's wrong maneuvers during driver assistance, as they do not effectively account for road reaction forces in real-time.
Innovation Solution
A motor control device that includes a manual steering command value generation unit, an integrated angle command value calculation unit, and a control unit for electric motor angle control. This device generates manual steering command values based on an equation of motion incorporating road reaction force characteristic coefficients, which are dynamically adjusted based on vehicle environment information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If driver assistance mode is activated to reduce manual steering workload, then ease of operation is improved, but the risk of accidents due to driver wrong maneuvers increases
Solution Approach 1:
The system applies preliminary anti-action by pre-calculating and storing road reaction force characteristics for various road conditions before driver intervention occurs. When the driver makes a wrong maneuver, the system immediately retrieves the pre-prepared reaction force characteristics that counteract the wrong direction, reducing the response time and effectiveness of corrective action.
Solution Approach 2:
The system dynamically adjusts the road reaction force characteristics based on detected road conditions and driving state. The reaction force coefficients are not fixed but are continuously updated according to the current environment, allowing the steering assist force to adapt in real-time to prevent wrong maneuvers while maintaining ease of operation.
2Device complexity
If fixed road reaction force coefficients are used in the equation of motion, then device complexity is reduced, but the system cannot adapt to changing vehicle environments
Solution Approach 1:
The system performs preliminary action by pre-storing multiple sets of road reaction force characteristics corresponding to different road conditions (wet, dry, icy, etc.) in a database before actual driving situations occur. This allows the system to quickly retrieve appropriate coefficients without complex real-time calculations, maintaining low device complexity while achieving high adaptability.
Solution Approach 2:
The system changes parameters by selecting different road reaction force coefficient sets based on detected road conditions. Instead of using a single fixed coefficient, the system switches between pre-defined parameter sets (k1, k2, k3 for spring constants and c1, c2, c3 for damping coefficients) to match the current environment, achieving adaptability without increasing fundamental system complexity.
Data Source
AI summary
A motor control device includes: a manual steering command value generation unit that generates a manual steering command value; an integrated angle command value calculation unit that calculates an integrated angle command value by adding the manual steering command value to an automatic steering command value provided in a driver assist mode; and a control unit that performs angle control on an electric motor for steering angle control based on the integrated angle command value. The manual steering command value generation unit generates the manual steering command value based on an equation of motion including road reaction force characteristic coefficients. The motor control device further includes a road reaction force characteristic changing unit that changes a value of at least one of the road reaction force characteristic coefficients included in the equation of motion, based on vehicle environment information that is information on an environment in which a vehicle travels.