Mobile Vehicle Steering Actuator Control for Low-Speed Stability
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Solution Overview
Problem
Two-wheeled vehicles, such as motorcycles, face challenges in maintaining stability, especially when stopped or traveling at low speeds, due to the large positive trail and passive steering of the rear wheel, which can lead to oscillations in posture control during steering.
Innovation Solution
A mobile vehicle equipped with a steering actuator and a control device that stabilizes the vehicle's posture by controlling the front or rear wheel's steering, adjusting the sensitivity of steering force based on the steering angle to prevent oscillations and enhance robustness over a wide steering range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the steering axis is tilted backward with a positive caster angle to enhance straight traveling property, then the straight traveling stability is improved, but the trail becomes large which causes oscillation in posture control during steering
Solution Approach 1:
The patent dynamically adjusts the caster angle parameter during steering operations. The control device changes the steering axis tilt angle from a positive caster angle during straight traveling to a reduced or negative caster angle during steering, thereby reducing the trail and preventing oscillation while maintaining straight traveling stability when needed
2Device complexity
If the rear wheel is passively steered by reaction force to simplify the structure, then the device complexity is reduced, but the posture control robustness deteriorates especially at low speeds
Solution Approach 1:
The patent transitions the rear wheel steering from a passive static system to an active dynamic system. The control device actively controls the rear wheel steering angle based on vehicle state (speed, posture, acceleration) rather than relying solely on passive reaction forces, thereby improving posture control robustness while maintaining structural simplicity through electronic control
3Speed
If the steering actuator generates strong steering force to improve response speed, then the steering response speed is improved, but the sensitivity to inclination angle changes increases causing oscillation
Solution Approach 1:
The control device employs periodic or pulsed steering actuation rather than continuous strong force application. By applying steering force in controlled intervals and adjusting the magnitude based on current posture error, the system achieves fast response while avoiding excessive sensitivity and oscillation
Solution Approach 2:
The patent implements feedback control where the control device continuously monitors the inclination angle and steering angle, and adjusts the steering actuator output accordingly. The feedback mechanism reduces the actuator sensitivity to inclination angle changes by dynamically scaling the steering force based on the current state, preventing oscillation while maintaining fast response
Data Source
AI summary
In a mobile vehicle 1A having a front wheel 3f and a rear wheel 3r, the steered wheel 3f can be steered by an actuator 8. A control device 15 controls the actuator 8 so as to stabilize the inclination angle φb in the roll direction of the vehicle body 2 and the steering angle δf of the steered wheel 3f. The control device 15 causes the sensitivity of the steering of the steered wheel 3f to the change in observed value of the inclination angle φb to be changed in accordance with the steering angle of the steered wheel 3f.