Straddled Vehicle Steering Assist Device Speed-Dependent Control
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Solution Overview
Problem
Conventional straddled vehicles with steering assist devices do not effectively manage steering torque assistance based on vehicle speed, leading to inconsistent steering characteristics, particularly at low and high speeds, where different magnitudes of steering torque and angle require varying levels of assist force.
Innovation Solution
A steering assist device that adjusts assist force in response to vehicle speed, decreasing assist force at low speeds and increasing it at higher speeds, with specific zones defined for these changes to match the rider's input torque, ensuring optimal steering characteristics across the vehicle speed range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If assist force is decreased as vehicle speed increases, then steering control precision is improved in high-speed zone, but steering ease deteriorates in high-speed zone
Solution Approach 1:
The steering assist device dynamically adjusts the assist force based on vehicle speed, transitioning from decreasing assist force at low speeds to increasing assist force at high speeds. This dynamic adaptation resolves the contradiction by optimizing steering characteristics for different operating conditions, improving both control precision and ease of operation in their respective speed zones.
Solution Approach 2:
The system changes the parameter of assist force magnitude based on vehicle speed conditions. By switching the control strategy between two different speed zones, the system adapts the assist force parameter to match the rotational moment characteristics at different speeds, thereby resolving the contradiction between control precision and steering ease.
2Speed
If steering ratio is close to 1, then handling responsiveness is improved, but rotational moment increases at high speed
Solution Approach 1:
The system compensates for the increased rotational moment at high speeds by dynamically adjusting the assist force parameter. When vehicle speed is high and steering ratio is close to 1, the system increases assist force to counterbalance the larger rotational moment, thereby maintaining ease of operation while preserving the responsive handling characteristics.
3Ease of operation
If assist force is increased at high vehicle speed, then steering ease is improved, but steering control precision deteriorates
Solution Approach 1:
The system dynamically switches between two control modes based on vehicle speed: decreasing assist force at low speeds for precision, and increasing assist force at high speeds for ease of operation. This dynamic switching resolves the contradiction by applying the appropriate control strategy for each operating condition.
Data Source
AI summary
A straddled vehicle includes a vehicle body frame, a steering shaft supported by the vehicle body frame, a handlebar that includes a left grip and a right grip and is connected to the steering shaft, a steering wheel, and a steering assist device that applies assist force in a same direction as that of a steering torque that has been input to the handlebar by a rider to the steering shaft. The steering assist device causes the assist force to decrease as speed of the vehicle increases in a first vehicle speed zone and causes the assist force to increase as the speed of the vehicle increases in a second vehicle speed zone that is higher than the first vehicle speed zone.