Rear Wheel Steering Control Device Actuator Response
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Solution Overview
Problem
Rear wheel steering control devices face challenges in generating sufficient drive force due to the need for a large motor size, leading to response delays and strange feelings in vehicle behavior during high-speed steering changes, as existing technologies struggle to manage the reduction ratio and actuator response effectively.
Innovation Solution
A rear wheel steering control device with an actuator control system that includes a steering angle command value calculator, target value setting updater, and command value direction determiner, which calculates and updates the steering angle target values to manage the actuator's response speed and direction, ensuring timely and accurate steering angle changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the reduction ratio of the reduction mechanism is increased to generate sufficient drive force, then the actuator can produce enough steering force, but the response speed of the actuator decreases causing steering angle changing delay
Solution Approach 1:
The control system dynamically adjusts the target steering angle based on the current steering angle and a predetermined maximum changing amount per unit time. This creates a dynamic control strategy that adapts to the actuator's speed limitations while ensuring the steering force requirements are met through controlled progression toward the target angle.
Solution Approach 2:
The control system continuously monitors the current steering angle and compares it with the target steering angle to determine the appropriate control action. This feedback mechanism ensures that the actuator operates within its speed capabilities while progressively achieving the desired steering force and angle.
2Power
If a large motor size is used to increase output power, then sufficient drive force can be generated, but installation and arrangement become difficult
Solution Approach 1:
Instead of increasing motor size to gain power, the system changes the control parameters by implementing a maximum steering angle changing amount per unit time. This allows a smaller motor to achieve the required steering capability through optimized control strategies rather than brute force mechanical power.
3Force
If the reduction ratio is increased to secure drive force, then the actuator can overcome suspension geometry requirements, but the steering angle changing speed decreases causing response delay
Solution Approach 1:
The control system preliminarily determines the target steering angle by considering both the desired final position and the maximum achievable changing amount per unit time. This preliminary calculation ensures that the actuator is prepared to move at optimal speed while maintaining the necessary force output throughout the steering operation.
4Force
If the actuator response is delayed due to increased reduction ratio, then drive force is sufficient, but the actual steering angle becomes reverse to the command value during high speed steering changes
Solution Approach 1:
The control system implements dynamic target angle adjustment by calculating the target steering angle as the sum of the current angle and a predetermined maximum changing amount. This dynamic approach prevents overshooting and reverse movements by adapting the target progression to the actuator's actual response capabilities, ensuring reliable steering control even during high-speed maneuvers.
Data Source
AI summary
Generally, the toe angle target speed limiting unit (84A) adds a toe angle target value αT2P subjected to the primary delay to the result of a min-max processing the tracking error ΔαT1A by an adder (58A) to output it as a toe angle target value αT2A to a target current calculating unit (86). However, in this toe angle target speed limiting unit (84A), a switching control (steering direction change control) for generating a maximum value ΔαTmax as the toe angle target change quantity ΔαT2 and a hold control are made when a neutral position of the toe angle target value αT2A which is prior to the toe angle command value αT1 which is reached.