Steering Control Torque Compensation for Resonance

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Solution Overview

Problem

In autonomous driving systems, the hand-off state where the driver is not actively operating the steering wheel can lead to resonance due to the inertia of the steering wheel, causing a decrease in the follow-up performance of the actual turning angle for the target angle, as the frequency characteristics of the vehicle plant and the nominal plant differ, affecting the accuracy of motor control.

Innovation Solution

A steering control apparatus that includes an electronic control unit to compute and correct the feedback control torque by accounting for the inertia torque of the steering wheel, ensuring the actual angle follows the target angle by compensating for the inertia torque and using feedforward control to enhance motor response.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If feedback control is executed based on target angle from host control apparatus during autonomous driving, then automation level is improved, but follow-up performance deteriorates due to resonance from steering wheel inertia in hand-off state

Engineering Contradiction:

Improveautonomous driving controlVSAvoidfollow-up performance

Core Design Contradiction:

Extent of automationVSReliability

Solution Approach 1:

The patent applies feedback control by detecting the actual steering angle through a sensor and comparing it with the target angle from the host control apparatus. The feedback control torque is computed based on the angle deviation, and this torque is used to correct the command value to ensure the actual angle follows the target angle even during autonomous driving in hand-off state.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the control parameter from pure target angle following to target angle following with inertia torque compensation. By detecting the applied torque through a torque sensor and computing the inertia torque component, the system adjusts the command value to compensate for resonance effects, thereby maintaining follow-up performance during autonomous driving.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If disturbance observer is used to estimate disturbance torque, then manufacturing precision is improved, but accuracy deteriorates when resonance occurs due to frequency characteristic mismatch between vehicle plant and nominal plant

Engineering Contradiction:

Improvemotor control accuracyVSAvoiddisturbance torque estimation accuracy

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent uses feedback control with actual angle detection to directly measure the deviation between target and actual angles. This feedback mechanism provides accurate information about the actual system behavior, allowing the controller to compensate for disturbance torque without relying solely on the disturbance observer's estimation, thereby maintaining accuracy even when resonance occurs.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces a torque sensor as an intermediary to directly detect the applied torque on the steering wheel. This intermediary device provides accurate measurement of the actual torque including inertia effects, which is then used to compute and compensate for disturbance torque, bypassing the frequency characteristic mismatch problem of the disturbance observer.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If hand-off state is maintained with driver hands off steering wheel, then ease of operation is improved, but harmful factors increase due to resonance from steering wheel inertia

Engineering Contradiction:

Improvedriver workload reductionVSAvoidresonance from steering wheel inertia

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful resonance effect into a measurable parameter by using a torque sensor to detect the applied torque. The detected torque information, which includes the inertia effects causing resonance, is then used to compute disturbance torque compensation. This transforms the harmful resonance into useful feedback information that enables automatic correction, allowing the system to maintain stability even in hand-off state.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent replaces the mechanical connection between driver and steering wheel with an electronic control system. Instead of relying on the driver's mechanical input to dampen resonance, the system uses electronic sensors (angle sensor and torque sensor) and electronic control to detect and compensate for inertia effects, thereby eliminating the need for mechanical driver involvement while maintaining system stability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11964714B2Steering control apparatus

Publication Date: 2024.04.23 JTEKT CORP

AI summary

A steering control apparatus controls a motor used to turn a steered wheel of a vehicle, which synchronizes with a steering wheel, based on a command value. The steering control apparatus includes an electronic control unit. The electronic control unit is configured to compute a feedback control torque to be reflected in the command value. The electronic control unit is configured to compute a disturbance torque based on the feedback control torque and a predetermined angle. The electronic control unit is configured to correct the feedback control torque by using the disturbance torque. The electronic control unit is configured to correct the command value reflecting the corrected feedback control torque, based on an applied torque.