Steering Assist Torque Control for Smooth Maneuvering and Neutral Return
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Solution Overview
Problem
Existing steering control devices fail to smoothly adjust steering torque when a driver is holding the steering wheel and return the steering to a neutral position when the driver releases their hands, leading to unsatisfactory steering feelings in both states.
Innovation Solution
A steering control device that includes a motor, steering torque detection, target steering torque setting, and multiple assist torque calculation units to calculate and apply steering assist torque based on integral, velocity, and proportional control components, ensuring smooth steering and appropriate return to neutral position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a steering assist torque is generated based on deviation between target steering torque and detected steering torque, then smooth steering is achieved when driver holds steering wheel, but steering wheel does not return to neutral position or over returns when driver releases hands
Solution Approach 1:
The patent applies dynamics by making the control system adapt its behavior based on the detected steering state. The control unit dynamically switches between different control modes: when driver input is detected, it provides assist torque for smooth steering; when driver input ceases, it activates return-to-neutral control. This dynamic adaptation resolves the contradiction by allowing the system to optimize for smoothness during steering and reliability for return-to-neutral during hands-off states.
Solution Approach 2:
The patent changes control parameters based on steering state. The control unit monitors steering torque and angular velocity to detect when the driver releases the steering wheel, then adjusts the assist torque calculation to promote return to neutral position. This parameter change allows the system to transition from smooth-steering optimization to return-to-neutral optimization, resolving the contradiction between the two operational requirements.
2Measurement precision
If steering assist torque is calculated using integral control of torque deviation, then steady-state accuracy is improved, but steering wheel return speed becomes uncontrolled
Solution Approach 1:
The patent dynamically adjusts the control strategy based on operating conditions. During normal steering with driver input, the system uses integral control for accurate torque following. When driver input stops and the steering wheel begins returning, the system transitions to a different control mode that prioritizes controlled return speed. This dynamic switching resolves the contradiction between steady-state accuracy and return speed control.
Solution Approach 2:
The patent employs feedback by continuously monitoring both steering torque and motor rotational angular velocity. This dual feedback allows the control unit to detect the transition from steering to return-to-neutral states and adjust control parameters accordingly. The feedback mechanism enables the system to maintain integral control benefits during steering while preventing uncontrolled return speed during hands-off states.
3Device complexity
If a single steering assist torque calculation method is used, then device complexity is reduced, but steering performance deteriorates in hands-off state
Solution Approach 1:
The patent implements multi-functionality by enabling the control unit to perform multiple control tasks using a single integrated system. The same control unit that calculates assist torque during steering also detects hands-off states and controls return to neutral. This universal approach maintains device simplicity while achieving adaptability to different steering states through software-based control logic rather than separate hardware systems.
Solution Approach 2:
The patent makes the control system dynamic by allowing it to change its control strategy based on detected steering states. The control unit continuously monitors steering conditions and adapts its torque calculation method accordingly - using integral control during steering and return-to-neutral control during hands-off states. This dynamic behavior provides versatility without requiring complex separate systems for each function.
Data Source
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AI summary
Provided is a steering control device capable of causing a steering torque to follow a target steering torque when a driver holds a steering wheel (1) for steering, thereby achieving smooth steering, and making an adjustment so that the steering wheel (1) returns to a neutral position at an appropriate speed, when the driver releases his or her hands from the steering wheel (1), thereby being able to achieve satisfactory steering feelings even in a steering state and in a hands-off state. A motor (6) is controlled based on a motor steering assist torque, which is a sum of a first steering assist torque, which is proportional to an integral value of a deviation between the target steering torque and the steering torque, and a second steering assist torque, which is proportional to a motor rotational angular velocity and acting in a direction of suppressing a return speed of the steering wheel (1) when the steering wheel (1) returns to the neutral position.