Turning Control Torque Variation Limiting With Control-Torque Priority
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Solution Overview
Problem
The variation in torque at the position closer to the turning wheel due to the steering angle in existing steering systems causes a strange feeling for the driver and interferes with intended vehicle behavior control.
Innovation Solution
A turning control device that includes a processor to execute processes for acquiring steering and control torque variables, manipulating an assist motor based on these variables, and restricting torque variation to maintain a suitable balance between steering feel and vehicle controllability by adjusting the priority of control torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the assist motor gives torque to a position closer to the turning wheel than the second Cardan joint, then the torque can be controlled to not vary depending on steering angle, but the torque given to the steering shaft varies depending on steering angle causing driver discomfort
Solution Approach 1:
A torque variation compensation mechanism acts as an intermediary between the assist motor and the steering shaft. The processor calculates the torque variation caused by Cardan joints and applies compensating torque through the assist motor, thereby mediating the torque transmission to eliminate steering angle-dependent variations while maintaining natural steering feel at the steering wheel.
Solution Approach 2:
The system dynamically changes the torque parameter output by the assist motor based on detected steering angle and steering torque. The processor adjusts the assist torque in real-time to compensate for variations introduced by Cardan joints, ensuring consistent steering characteristics across different steering angles while maintaining control stability.
2Measurement precision
If the torque at the position closer to the turning wheel is controlled to not vary depending on steering angle, then torque control precision is improved, but the steering torque varies depending on steering angle causing strange feeling for driver
Solution Approach 1:
The system employs feedback control where the processor continuously detects steering angle and steering torque, calculates the resulting torque variations through Cardan joints, and adjusts the assist motor output accordingly. This closed-loop feedback mechanism ensures precise torque control at the turning wheel while compensating for steering angle effects to maintain natural steering feel.
Solution Approach 2:
The assist torque parameter is dynamically adjusted based on real-time steering conditions. The processor modifies the torque magnitude and direction through the assist motor to counteract variations caused by Cardan joints, achieving both precision control and natural steering characteristics across the full range of steering angles.
3Ease of operation
If the assist motor compensates for torque variation to maintain constant steering torque, then driver comfort is improved, but the control torque for vehicle behavior control is interfered with
Solution Approach 1:
The system dynamically switches between different control modes based on driving conditions. In normal steering conditions, the assist motor compensates for Cardan joint torque variations to provide comfortable steering. In emergency or active control situations, the system prioritizes control torque delivery for vehicle behavior management, dynamically adjusting the compensation level to balance comfort and control effectiveness.
Solution Approach 2:
The assist torque parameter is adaptively adjusted based on the type of steering operation. For manual steering, the system applies full compensation for Cardan variations. For active vehicle control operations, the system modifies or reduces compensation to ensure control torque is effectively transmitted, thereby adapting the steering characteristics to match the required control priority.
Data Source
AI summary
A processor included in a turning control device is configured to execute a manipulation process of manipulating a drive circuit of an assist motor depending on a torque that depends on at least one of the two values, the value of an assist torque variable and the value of a control torque variable. The processor is configured to execute a variation torque control process of varying a torque as an input variable in the manipulation process, depending on a steering angle, based on the value of the steering angle variable as an input variable. The processor is configured to execute a restriction process of restricting the magnitude of variation in the torque as the input variable in the manipulation process depending on the steering angle, to a small side, depending on the priority degree of the value of the control torque variable in the manipulation process.