Electric Power Steering Apparatus Vibration Damping Control
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Solution Overview
Problem
Conventional electric power steering systems face challenges in accurately following a target steering angle due to changes in vehicle speed, road surface reaction forces, and vibrations, leading to potential vehicle drift and inefficient damping.
Innovation Solution
An electric power steering apparatus that calculates a target steering angle by incorporating lateral position and velocity controls, using I-P control and phase compensation to improve followability and damping, thereby enhancing the system's resistance to disturbances and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feedback control is used to adjust motor voltage based on current command value and detected motor current, then the steering assist torque can be generated, but the system cannot effectively suppress vehicle vibrations and the target steering angle followability deteriorates under varying road surface conditions
Solution Approach 1:
The patent introduces a dual feedback mechanism: (1) Current feedback control that adjusts motor voltage based on the difference between current command value and detected motor current, and (2) Steering angle feedback that detects actual steering angle and feeds it back to calculate target steering angle. This combined feedback system enables the controller to compensate for vibrations and road surface reactions, improving followability while maintaining assist torque accuracy.
Solution Approach 2:
The patent calculates a target steering angle in advance based on detected actual steering angle and stored map information corresponding to vehicle speed. This preliminary calculation of target steering angle allows the system to proactively compensate for expected vibrations and road surface reactions before they significantly affect steering accuracy, rather than merely reacting to them.
2Device complexity
If the target steering angle is calculated without considering vehicle speed and road surface conditions, then the control system is simple, but the actual steering angle cannot accurately follow the target angle under varying driving conditions
Solution Approach 1:
The patent dynamically changes the target steering angle parameter based on vehicle speed and detected actual steering angle. The controller selects appropriate map information corresponding to different vehicle speeds and combines it with actual steering angle data to calculate an optimized target steering angle. This parameter adaptation enables accurate followability across varying driving conditions without requiring a fundamentally more complex control architecture.
Solution Approach 2:
The patent creates a universal control approach where a single controller handles multiple functions: generating steering assist torque through current control, calculating target steering angle using map information and actual steering angle, and compensating for vibrations. This multi-functional design achieves high followability without proportionally increasing system complexity.
3Speed
If damping control is not implemented, then the control system responds quickly to steering inputs, but vehicle vibrations are not suppressed and driver comfort deteriorates
Solution Approach 1:
The patent uses steering angle feedback to detect actual steering angle and compares it with the calculated target steering angle. This feedback mechanism enables the controller to identify deviations caused by vibrations and road surface reactions, and generate compensatory control signals that suppress these harmful oscillations while maintaining rapid response to legitimate steering inputs.
Solution Approach 2:
The patent converts the harmful effect of vehicle vibrations and road surface reactions into useful information. By detecting deviations between actual and target steering angles, the system identifies vibration patterns and uses this information to generate compensatory control signals. The previously harmful vibrations become the basis for creating damping control actions that improve driver comfort.
Data Source
AI summary
An electric power steering apparatus that reduces uncomfortable feeling to a driver in steering angle control by improving followability of an actual steering angle to a target steering angle, and performs efficient damping to a vibration of a vehicle. The apparatus includes a torque control section that calculates a first motor current command value based on a steering torque and so on, a target steering angle generating section that generates a target steering angle based on vehicle information, and a steering angle control section that calculates a second motor current command value based on the target steering angle, an actual steering angle and so on, and calculates the motor current command value by the first and second motor current command values.