Steering Torque Control for Friction and Return Force Feel
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Solution Overview
Problem
Existing steering systems fail to provide a pleasant and precise steering sensation, particularly in the initial movement phase of the steering control element, lacking adequate friction and return force simulation.
Innovation Solution
A method and device that calculate and adjust motor torque to simulate friction and return force by determining system friction through motor and torsion bar torques, using gearing efficiency and a predetermined factor to enhance steering sensation, with optional filtering and speed-based adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a motor is added to provide return force and friction simulation, then steering sensation is improved, but device complexity increases
Solution Approach 1:
A torque sensor is introduced as an intermediary component to measure the actual torque at the steering column. This measured torque serves as feedback to the control unit, which then calculates the required motor torque to simulate friction and provide return force. The torque sensor acts as a mediator between the mechanical steering system and the electric motor, enabling precise control of steering sensation without requiring complex mechanical linkages.
Solution Approach 2:
The system implements a closed-loop feedback mechanism where the torque sensor continuously monitors the actual torque at the steering column, and this information is fed back to the control unit. The control unit compares the actual torque with the desired torque (calculated based on steering angle, steering speed, and friction characteristics) and adjusts the motor torque accordingly. This feedback loop enables dynamic simulation of friction and return force, improving steering sensation while maintaining system simplicity.
2Measurement precision
If friction torque is increased to improve steering precision, then steering sensation is enhanced, but energy loss increases
Solution Approach 1:
The system replaces mechanical friction elements with an electric motor that simulates friction through controlled torque application. Instead of using physical friction surfaces that would cause energy loss, the motor generates a calculated friction torque based on steering angle and steering speed. This substitution allows for precise control of friction characteristics while minimizing actual energy dissipation, as the motor can recover energy during regenerative braking or idle periods.
Solution Approach 2:
The system dynamically adjusts the friction torque parameter based on steering conditions. The control unit calculates the desired friction torque as a function of steering angle and steering speed, applying higher friction during low-speed maneuvers for precision and reducing friction during high-speed operation to minimize energy loss. This parameter adaptation allows the system to optimize the balance between steering precision and energy efficiency in real-time.
Data Source
AI summary
In a method for producing a steering sensation in a steering system, which includes a motor and a torsion bar which are connected to each other via a gearing, a torque of the motor and a torsion bar torque at the torsion bar are determined, a stepped-up motor torque is determined depending on the motor torque and on a transmission ratio and efficiency of the gearing, a friction torque is determined depending on a difference between the stepped-up motor torque and the torsion bar torque, a desired friction torque is determined depending on the friction torque, a desired motor torque is determined depending on the desired friction torque and the motor torque, and the motor is activated to produce the desired motor torque.