Electric Power Steering Motor Controller Vibration Suppression
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Solution Overview
Problem
Existing electric power steering systems experience mechanical vibration in the steering wheel due to the twisting of the torsion bar when an electric motor produces automatic steering torque, which affects the accuracy and comfort of steering assistance.
Innovation Solution
An electric power steering system with a motor controller that controls the response rate of automatic steering torque production, using a torsion sensor to measure twisting and adjust the assist and tracking commands to minimize vibration, ensuring the system is insensitive to noise and reduces steering vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electric motor is actuated to output automatic steering torque, then the steering control accuracy is improved, but mechanical vibration is generated in the steering wheel due to torsion bar twisting
Solution Approach 1:
The system performs preliminary action by predicting the steering torque required for automatic steering control in advance, then pre-compensating for the torsion bar twisting effect before the actual steering action occurs. This allows the system to maintain high control accuracy while eliminating vibration by preparing the compensation in advance rather than reacting to the vibration after it occurs.
Solution Approach 2:
The system creates a virtual model (copy) of the torsion bar twisting behavior and uses this model to predict and compensate for the distortion. By copying the twisting characteristics mathematically, the system can calculate the expected error and counteract it through control algorithms, thereby maintaining accuracy without generating actual mechanical vibration.
2Speed
If the response rate of automatic steering torque is increased, then the steering responsiveness is improved, but the system becomes sensitive to noise causing steering vibration
Solution Approach 1:
The system dynamically adjusts the response rate based on operating conditions. By making the response rate variable rather than fixed, the system can achieve high responsiveness when needed while reducing sensitivity to noise in conditions where rapid response is less critical. This dynamic adaptation allows the system to optimize between responsiveness and noise sensitivity in real-time.
Solution Approach 2:
The system uses feedback mechanisms to monitor the actual steering behavior and compare it with the commanded behavior. When noise sensitivity is detected, the feedback loop adjusts the response rate to reduce gain, thereby suppressing vibration while maintaining the ability to respond to legitimate steering demands. This closed-loop control enables the system to maintain responsiveness without excessive noise sensitivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively suppresses steering vibration by controlling the response rate of automatic steering torque, enhancing the accuracy and comfort of steering assistance while maintaining sensitivity to environmental conditions and control modes.
Implementation Method 1
a torsion sensor which measures twisting of the torsion bar as a steering torque
Implementation Method 2
an electric motor which is joined to the steering mechanism and works to output torque for steering the system vehicle
Data Source
AI summary
An electric power steering system for a vehicle works to determine an assist command based on steering torque to produce assist torque through an electric motor for assisting in turning a steering wheel of the vehicle, also determines a tracking command for producing automatic steering torque which brings a value of a given physical quantity associated with steering of the vehicle into agreement a target value, and controls a response rate at which a value of a given physical quantity is brought into agreement with a target value in a feedback mode. A motor driver works to actuate an electric motor based on the sum of the assist command and the tracking command to output the torque for steering the system vehicle.