Dual Motor Electric Power Steering with Compensation Control

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Solution Overview

Problem

Existing electric power steering systems for large commercial vehicles struggle to accurately reflect the driver's steering intention and provide sufficient assistance power, especially during rapid lane changes or evasive maneuvers, due to their high steering ratios and the need for high power and load handling.

Innovation Solution

The implementation of a dual motor electric power steering apparatus with a controller that calculates compensation rotation by comparing the steering angle and sector shaft angle, allowing for precise control of the motor's rotation and selective operation of dual motors based on vehicle state and steering wheel position, to provide appropriate assistance power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a single motor is used in the electric power steering system, then the device complexity is reduced, but the steering response speed and assistance power are insufficient for rapid lane changes and evasive maneuvers

Engineering Contradiction:

Improvesteering response speedVSAvoidmotor system complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The steering motor is divided into two independent motors (first motor and second motor) that can operate separately or together. This segmentation allows the system to provide rapid steering assistance when needed by activating both motors, while maintaining simpler operation during normal conditions by using only one motor.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control system dynamically selects which motor(s) to activate based on the steering situation. The controller determines whether to use the first motor alone, the second motor alone, or both motors simultaneously, allowing the system to adapt its complexity and power output to the specific driving conditions.

Inventive Principle:

Principle #15Dynamics

2Force

If the steering ratio is increased for high power handling, then the load bearing capacity is improved, but the steering precision and driver intention reflection are degraded

Engineering Contradiction:

Improveload bearing capacityVSAvoidsteering angle precision

Core Design Contradiction:

ForceVSMeasurement precision

Solution Approach 1:

The system uses feedback from the angle sensor to detect the actual sector shaft rotation and compares it with the commanded rotation. The compensation rotation is calculated based on this feedback to correct any deviations, ensuring precise steering control even with high steering ratios.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control system adjusts the motor rotation amount dynamically based on the calculated compensation rotation. By changing the rotation parameter in real-time according to the actual steering state, the system maintains precision despite the mechanical advantage provided by high steering ratios.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If compensation rotation is not calculated, then the control system is simpler, but the steering accuracy and driver intention reflection are insufficient

Engineering Contradiction:

Improvesteering angle accuracyVSAvoidcontrol algorithm complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of using complex mechanical linkages or additional sensors to directly measure steering angle, the system substitutes a computational approach. The controller calculates the compensation rotation by comparing the commanded sector shaft rotation with the actual rotation detected by the angle sensor, achieving accurate steering control through software-based correction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Power

If both dual motors are always driven, then the steering power is sufficient for all conditions, but the energy consumption increases and assistance power suitability is reduced

Engineering Contradiction:

Improvesteering assistance powerVSAvoidmotor energy consumption

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The system applies partial action by activating only the necessary motor(s) based on the steering situation. During normal steering conditions, only one motor is driven, consuming less energy. During emergency maneuvers requiring rapid lane changes, both motors are activated to provide excessive power when needed, optimizing the balance between power availability and energy consumption.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11524717B2Electric power steering apparatus and control method thereof

Publication Date: 2022.12.13 HL MANDO CORP

AI summary

An electric power steering apparatus and a control method thereof. A motor includes a first motor providing power to move a rack and a second motor providing power to move the rack in synchronization with the first motor. A sensor includes a torque angle sensor detecting a torque value and a steering angle in response to manipulation of a steering wheel and an angle sensor detecting an angle of rotation of a sector shaft. A controller controls the motor in response to the manipulation of the steering wheel, calculates an amount of compensation rotation of the motor by comparing the steering angle and the angle of rotation, and controls an amount of rotation of the motor in accordance with an amount of compensation rotation. The amount of rotation of a vehicle's wheel is controlled, so that actual intention of the driver in steering is accurately reflected.