Turning Control Device Using Steering-Angle Torque Compensation
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Solution Overview
Problem
The variation in the ratio between the steering angle and the turning angle due to the universal joint causes an unintended change in assist torque, leading to a strange feeling for the driver.
Innovation Solution
A turning control device that includes a processor to execute processes for acquiring a turning-corresponding angle, estimating a rudder angle variable, setting a basic assist torque, calculating adjusting torque, and controlling the assist motor torque based on these variables, ensuring the torque is set appropriately relative to the steering angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the assist motor applies torque closer to the turning wheel than to the universal joint, then the torque control should be more direct and effective, but the adjusting torque unintentionally varies depending on the steering angle due to the universal joint's variable ratio
Solution Approach 1:
The control device uses feedback from a sensor detecting the rotational angle of the assist motor to calculate the turning-corresponding angle, then estimates the steering angle and time-differential value to dynamically adjust the assist torque. This closed-loop feedback mechanism compensates for the variable ratio effect of the universal joint, maintaining stable torque control despite the mechanical transmission variations.
Solution Approach 2:
The system changes the control parameter from directly using the assist motor's rotational angle to using an estimated steering angle that accounts for the universal joint's variable ratio. By calculating the turning-corresponding angle and estimating the rudder angle variables, the system adapts the torque control parameters to compensate for mechanical transmission variations, ensuring stable assist torque across different steering angles.
2Ease of operation
If the adjusting torque is set depending on the rotational angle of the transmitting shaft, then the torque control follows the mechanical transmission, but the torque unintentionally varies with steering angle due to universal joint characteristics
Solution Approach 1:
The control device introduces an intermediary estimation process that translates the assist motor's rotational angle into an estimated steering angle, accounting for the universal joint's variable ratio. This intermediary calculation layer mediates between the simple motor control and the complex mechanical transmission, eliminating the unintended torque variations while maintaining control simplicity.
3Ease of operation
If the torque of the assist motor is controlled based on steering angle and time-differential value, then the steering assist should be smooth and natural, but the variable ratio of the universal joint causes unintended torque variations
Solution Approach 1:
The system replaces direct mechanical torque control through the universal joint with an electronic control system that calculates and applies torque based on estimated steering angle and time-differential value. This substitution of mechanical control with electronic control eliminates the precision errors introduced by the universal joint's variable ratio, achieving both smooth steering feel and precise torque control.
Data Source
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AI summary
A turning control device includes a processor. The processor is configured to execute a turning-corresponding angle acquisition process, a rudder angle variable estimation process, a basic assist torque setting process, an adjusting torque calculation process, and a manipulation process. The basic assist torque setting process is a process of setting the value of a basic assist torque variable depending on a steering torque. The adjusting torque calculation process is a process of calculating the value of an adjusting torque variable. The manipulation process includes a process of manipulating a drive circuit of an assist motor (42), so as to control the torque of the assist motor (42) to a torque depending on the sum of a torque indicated by the value of the basic assist torque variable and a torque indicated by the value of the adjusting torque variable.