Steer-by-Wire Torque Modulation for Smaller Control Motors
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Solution Overview
Problem
Existing electric power steering systems without mechanical links require large and power-hungry control motors to generate the full range of motor torque, leading to high component costs and failure risks due to additional mechanical parts.
Innovation Solution
A method to determine a corrected set motor torque by comparing the set motor torque with a normal operating threshold, adjusting it within a corrected operating range using a correction frequency, and applying it to a control motor to simulate a greater torque sensation while reducing the motor's size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a large control motor is used to generate the full range of motor torque (30 Nm to 50 Nm), then the motor torque capability is improved, but the motor size and power consumption increase
Solution Approach 1:
The patent applies periodic action by modulating the control motor torque at a frequency of 8 Hz to 12 Hz. Instead of maintaining constant high torque, the system varies the torque periodically around an operating value, creating a vibratory sensation that simulates higher torque capability while using a smaller motor. This allows the control motor to generate time-varying torque rather than sustained maximum torque.
Solution Approach 2:
The patent utilizes mechanical vibration by inducing a vibratory sensation in the steering wheel through controlled torque modulation. The control motor generates torque variations at 8 Hz to 12 Hz that create perceptible vibrations, allowing the driver to sense torque information consistent with vehicle conditions without requiring the motor to continuously produce high torque levels.
2Weight of moving object
If a reducer is added to enable a smaller motor to generate the required torque range, then the motor size is reduced, but the device complexity and failure risk increase
Solution Approach 1:
The patent replaces the mechanical reducer system with an electronic control system. Instead of using mechanical components to multiply torque, the system uses electronic modulation of motor torque combined with vibratory feedback to achieve the desired torque sensation. This substitution eliminates additional mechanical parts and their associated failure risks while maintaining the ability to provide appropriate torque feedback to the driver.
3Force
If the control motor generates full torque (30 Nm to 50 Nm) during rack abutment, then the torque capability is maintained, but the steering wheel becomes blocked and cannot turn
Solution Approach 1:
During rack abutment conditions, the system applies periodic torque modulation at 8 Hz to 12 Hz rather than maintaining constant high torque. This periodic action creates a vibratory sensation that allows the steering wheel to continue turning while providing torque feedback to the driver, preventing complete blocking while maintaining torque information consistency with the abutment condition.
Data Source
AI summary
A method determines a corrected set motor torque for a control motor of a power steering system without mechanical link, the control motor receiving the corrected set motor torque and exerting a motor torque on an axis of rotation including a steering wheel. The method includes: a step of receiving a set motor torque and a correction step in which the corrected set motor torque is determined based on a result of a comparison between the set motor torque and a normal operating threshold, the corrected set motor torque varying with a correction frequency around a corrected operating value over a corrected operating range, the corrected operating value being lower than the set motor torque.