Steer-by-Wire Torque Control Without Mechanical Linkage

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Solution Overview

Problem

Steer-by-wire systems lack effective control methods for generating target currents to manage steering wheel reaction forces, which affects driver feedback and steering precision, especially without mechanical connections and torque sensors.

Innovation Solution

An apparatus and method that include a reaction torque generator, driver torque estimator, speed controller, torque adjuster, and target current generator to calculate and adjust motor torque based on rack force, vehicle speed, steering angular velocity, and steering angle, incorporating hysteresis torque and end-lock torque detection to enhance steering feel and prevent wheel over-rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If steer-by-wire system removes mechanical connection between steering wheel and wheels, then fuel efficiency improves and steering layout freedom increases, but driver feedback on steering reaction force deteriorates

Engineering Contradiction:

Improvefuel efficiencyVSAvoiddriver feedback on steering reaction force

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical connection system with an electronic control system. The ECU receives steering wheel rotation signals and controls steering motors to steer wheels, eliminating mechanical connections while maintaining steering functionality through electronic signal transmission and motor actuation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a reaction torque generator as an intermediary device between the steering wheel and the driver. This device generates reaction torque based on rack force, steering angular velocity, and steering angle to simulate the mechanical reaction force feedback, allowing drivers to perceive steering resistance without mechanical connections.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If steer-by-wire system excludes mechanical connection structure, then steering layout freedom improves, but steering precision and reaction force control deteriorate

Engineering Contradiction:

Improvesteering layout freedomVSAvoidsteering precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent implements dynamic control of steering torque through the ECU, which continuously adjusts motor torque based on real-time steering wheel rotation signals, rack force feedback, and steering angle data. This dynamic adjustment enables precise steering control and reaction force management despite the absence of mechanical connections.

Inventive Principle:

Principle #15Dynamics

3Object-generated harmful factors

If steer-by-wire system removes mechanical connection, then disturbances from wheels are eliminated, but control complexity increases

Engineering Contradiction:

Improvedisturbances from wheelsVSAvoidcontrol system complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent implements multiple feedback mechanisms where the ECU receives real-time signals from steering wheel rotation sensors, rack force sensors, and steering angle sensors. The system continuously adjusts steering motor torque based on these feedback signals, maintaining precise steering control and reaction force management despite the electronic nature of the system.

Inventive Principle:

Principle #23Feedback

4Ease of manufacture

If no torque sensor is used in steer-by-wire system, then manufacturing cost reduces, but measurement of driver torque and rack force becomes difficult

Engineering Contradiction:

Improvemanufacturing costVSAvoiddriver torque and rack force measurement

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent uses the reaction torque generator as an intermediary device that calculates rack force and driver torque based on measurable parameters such as steering angular velocity, steering angle, and motor torque. This approach enables indirect measurement of torque values without requiring direct torque sensors, reducing manufacturing costs while maintaining measurement capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11634173B2Apparatus and method for controlling steer-by-wire system

Publication Date: 2023.04.25 HYUNDAI MOBIS CO LTD

AI summary

A apparatus for controlling a steer-by-wire system including: a reaction torque generator configured to generate reaction torque as a calculated value of steering reaction torque applied to a steering wheel; a driver torque estimator configured to detect a driver torque estimation value as an estimated value of driver steering torque; a speed controller configured to generate a motor torque command value of a motor-driven power steering system; a torque adjuster configured to calibrate the motor torque command value and the reaction torque based on the driver torque estimation value, and output final active return torque and final reaction torque; and a target current generator configured to generate a target current for motor control by using the final active return torque and the final reaction torque, inputted from the torque adjuster, and input the generated target current to a motor.