Steering Device Virtual Limit Control via Dual Correction
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Solution Overview
Problem
Conventional steering systems struggle to prevent drivers from turning the steering wheel beyond a virtual limit position, leading to difficulties in controlling the steering reaction force and potentially causing the wheel to be operated past the intended limit.
Innovation Solution
A steering device with a control system that calculates a base command value and two correction values to resist and correct the steering angle, using a first correction value to increase the steering reaction force near the virtual limit and a second correction value to maintain the steering angle at the desired limit, along with a variable threshold setting and turning-back determination to adjust the correction values based on steering angular velocity and operation direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the correction value is increased sharply when the steering angle reaches the threshold to prevent the steering wheel from being operated beyond the virtual limit position, then the steering reaction force increases sharply, but the steering wheel may still be operated to a position beyond the virtual steering limit position if the steering torque applied from the driver becomes too large
Solution Approach 1:
The patent divides the correction value calculation into two separate correction values: a first correction value that increases the steering reaction force when the steering angle reaches the threshold, and a second correction value that actively controls the steering angle to return to the desired value when the steering angle exceeds the threshold. This segmentation allows each correction value to have a specific function, improving the reliability of virtual limit position control while maintaining ease of operation.
Solution Approach 2:
The patent dynamically adjusts the correction values based on the steering angle and steering torque. The first correction value is applied when the steering angle reaches the threshold, and the second correction value is applied when the steering angle exceeds the threshold. This dynamic adjustment ensures that the steering reaction force is appropriately increased to prevent excessive steering wheel operation while allowing smooth operation within the virtual limit.
2Force
If the first correction value is calculated to increase the steering reaction force when the steering angle reaches the threshold, then it becomes difficult for the driver to operate the steering wheel to a position beyond the virtual limit position, but if steering torque becomes too large, the steering wheel may still be operated beyond the steering limit position
Solution Approach 1:
The patent implements a feedback mechanism where the second correction value calculation circuit continuously monitors the steering angle and steering torque, and adjusts the correction value to maintain the steering angle at or below the desired value. This feedback ensures that even when large steering torque is applied, the steering wheel is restrained from being operated beyond the virtual limit position, thereby improving steering angle control reliability.
Solution Approach 2:
The patent changes the parameter of the correction value based on the steering angle and steering torque conditions. When the steering angle exceeds the threshold, the second correction value is calculated to actively control the steering angle back to the desired value. This parameter change ensures that the steering reaction force is appropriately adjusted to maintain reliable steering angle control under varying steering torque conditions.
3Device complexity
If a single correction value is used to control the steering reaction force, then the control system is simpler, but the steering wheel may be operated beyond the virtual steering limit position under high steering torque conditions
Solution Approach 1:
The patent segments the correction value control into two distinct correction values calculated by separate calculation circuits. The first correction value handles the basic steering reaction force control when the steering angle reaches the threshold, while the second correction value handles the additional control needed when the steering angle exceeds the threshold. This segmentation improves virtual steering limit position restraint reliability while keeping each individual calculation circuit relatively simple.
Solution Approach 2:
The patent introduces an addition circuit that combines the first correction value and the second correction value to produce the total correction value. This intermediary addition circuit allows the two correction values to work together synergistically, improving the reliability of virtual steering limit position restraint without requiring a completely complex control system architecture.
Data Source
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AI summary
A steering device is provided which can restrain the driver from turning a steering wheel to a position beyond a virtual steering limit position. A base current command value calculation circuit (55) calculates a base current command value (Ias*) based on a steering torque (Th) and a vehicle speed (V). A memory (59) has stored therein a desired steering angle value (θE) that is a constant representing the virtual steering limit position. In the case where a steering angle threshold is set to a value close to, and smaller than, the desired steering angle value (θE), a first correction value calculation circuit (56) calculates a first correction value (Ira*) so that a steering reaction force is increased rapidly when a steering angle (θs) becomes equal to or larger than the steering angle threshold. A second correction value calculation circuit (57) calculates a second correction value (Irb*) so that the steering angle (θs) becomes equal to the desired steering angle value (θE) when the steering angle (θs) becomes equal to or larger than the steering angle threshold. The base current command value (Ias*) is corrected by the first correction value (Ira*) and the second correction value (Irb*). The driver is thus restrained from turning the steering wheel to a position beyond the desired steering angle value (θE).