Steering Motor Control Without Torque Sensor
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Solution Overview
Problem
Power assisted steering systems without torque sensors can cause instability in assist motor control, compromising driver and passenger safety due to inconsistent driver feedback under varying driving conditions, such as low traction or sudden traction changes.
Innovation Solution
A power assisted steering system that controls the electric assist motor based on signals derived from the angular position, angular acceleration, and assistance torque output, allowing for consistent driver feedback without a dedicated torque sensor, by comparing theoretical and actual dynamic states and adjusting control signals accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a power assisted steering system is implemented without a torque sensor, then the device complexity is reduced, but the reliability deteriorates due to instability in assist motor control under limit usage conditions
Solution Approach 1:
The patent introduces an intermediary computational model that mediates between available sensors (position, speed) and the required control function. This model simulates driver torque intent without requiring a physical torque sensor, thereby reducing device complexity while maintaining control reliability through virtual sensing.
Solution Approach 2:
The patent replaces the mechanical torque sensor with an electronic/computational system that calculates equivalent torque information from other measurable parameters (motor position, speed, and dynamic models). This substitution eliminates the need for complex mechanical sensing while preserving the essential control function.
2Ease of manufacture
If a power assisted steering system without torque sensor is used, then the ease of manufacture is improved, but the stability deteriorates causing inconsistent driver feedback under varying driving conditions
Solution Approach 1:
The patent implements a feedback mechanism where the control system continuously monitors actual motor behavior and compares it with expected behavior from the computational model. This feedback loop allows real-time adjustment of control parameters to maintain stable and consistent driver feedback across varying driving conditions, compensating for the absence of direct torque sensing.
Solution Approach 2:
The patent employs dynamic adjustment of control parameters based on real-time operating conditions. The system adapts its behavior according to vehicle speed, steering rate, and road conditions, ensuring stable driver feedback characteristics across different scenarios without requiring complex hardware modifications.
Data Source
AI summary
The invention relates to a power assisted steering system (21) that includes an electric assist motor (22) arranged to assist the manual force exerted by a driver on the steering wheel of the automobile, a processing means (23) arranged to control the electric assist motor (22), the processing means (23) including a means (28) for predetermining a signal (S3) for controlling the electric assist motor on the basis of a first operation signal (S1) determined on the basis of the angular position of the electric assist motor, and a second operation signal (S2) determined on the basis of the measurement or calculation of the angular acceleration of the electric assist motor and the measurement or calculation of the assistance torque output by the electric assist motor.