Electric Power Steering Vibration Suppression via Torque Correction
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Solution Overview
Problem
Electric power steering systems experience mechanical vibrations in the steering wheel due to the twisting of the torsion bar when an electric motor produces assist or automatic steering torque, which can lead to discomfort and reduced control for the driver.
Innovation Solution
An electric power steering system that includes an electric motor, a torsion bar, a torque sensor, an assist controller, a target tracking controller, and a vibration correction controller, which calculates and generates a vibration correction torque to suppress resonance and eliminate steering vibrations by actuating the electric motor based on the transfer characteristic of the torsion bar's output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an electric motor is actuated to produce automatic steering torque, then the steering system can perform lane-keep control, but mechanical vibration is generated in the steering wheel due to torsion bar twisting
Solution Approach 1:
The vibration correction controller calculates a vibration correction torque that acts in advance to counteract the harmful vibrations generated by the electric motor. The controller determines the motor torque that will be output, predicts the resulting torsion bar twisting and steering wheel vibrations, and generates a correction torque to suppress these vibrations before they occur. This preliminary anti-action effectively cancel the harmful vibrations while maintaining the automatic steering torque functionality.
Solution Approach 2:
The vibration correction torque acts as an intermediary element between the electric motor and the steering wheel. By introducing this correction torque through the motor controller, the system mediates the interaction between the motor's automatic steering torque and the torsion bar, preventing the harmful vibrations from being transmitted to the steering wheel while allowing the motor to continue producing the required automatic steering torque.
2Measurement precision
If a torsion bar is installed between the steering wheel and electric motor, then steering torque can be measured, but the torsion bar twisting causes vibration transmission to the steering wheel
Solution Approach 1:
The vibration correction torque serves as an intermediary that decouples the measurement function of the torsion bar from its harmful vibration transmission. By introducing the correction torque through the motor controller, the system allows the torsion bar to continue measuring steering torque accurately while preventing the motor-induced twisting from being transmitted as vibrations to the steering wheel.
Solution Approach 2:
The invention extracts the harmful vibration transmission aspect from the torsion bar's function while preserving its measurement capability. By calculating and applying a vibration correction torque that counteracts the motor-induced twisting, the system separates the useful measurement function from the harmful vibration transmission, allowing the torsion bar to measure steering torque without transmitting harmful vibrations to the steering wheel.
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 minimizes steering vibrations by calculating and producing a vibration correction torque, thereby reducing resonance and enhancing the comfort and control of the steering mechanism, ensuring smoother operation and reduced mechanical stress on the steering components.
Implementation Method 1
a torsion bar which is installed in the steering mechanism and located between the mechanical steering member and a joint of the electric motor and the steering mechanism
Implementation Method 2
an electric motor which is joined to the steering mechanism and works to output torque for steering the system vehicle
Implementation Method 3
a vibration correction controller which works to calculate a vibration correction torque which suppresses vibration of the steering torque which arises from output of the torque from the electric motor based on a transfer characteristic of transmission of the output of torque from the electric motor
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 calculates a vibration correction command for use in producing vibration correction torque which suppresses vibration of the steering torque which arises from output of the torque from the electric motor based on a transfer characteristic of transmission of the output of torque from the electric motor as a part of the steering torque through the steering mechanism. A motor driver works to actuate the electric motor based on the sum of the assist command, the tracking command, and the vibration correction command.