Forklift Joystick Steering with Variable Ratio Control
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Solution Overview
Problem
Industrial truck joystick steering systems face challenges with limited deflection path and sensitivity, leading to deviations between intended and actual steering movements, affecting driving behavior due to the inherent differences between joystick and steering actuator dynamics.
Innovation Solution
An electronic control device operates the steering system in a closed control loop, adjusting the steering ratio and rate of change based on driving speed, optimizing joystick utilization for balanced sensitivity and range, and incorporating variable steering ratios to align joystick and steering actuator movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a joystick with limited range of motion is used for steering, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The steering ratio is made variable rather than fixed, allowing the system to dynamically adjust the relationship between joystick movement and steering wheel movement. This enables the limited joystick range to effectively cover the full steering angle range needed for different driving conditions
Solution Approach 2:
The steering ratio parameter is changed based on driving speed and steering angle requirements. At low speeds, a higher steering ratio amplifies small joystick movements for precise control, while at high speeds, a lower ratio provides broader steering range
2Device complexity
If a fixed steering ratio is used, then device complexity is reduced, but adaptability deteriorates
Solution Approach 1:
The steering ratio is made variable rather than fixed, allowing the system to dynamically adjust the relationship between joystick movement and steering wheel movement. This enables the limited joystick range to effectively cover the full steering angle range needed for different driving conditions
Solution Approach 2:
The steering ratio parameter is changed based on driving speed and steering angle requirements. At low speeds, a higher steering ratio amplifies small joystick movements for precise control, while at high speeds, a lower ratio provides broader steering range
3Stability of the object's composition
If the steering actuator has high inertia for stable operation, then stability is improved, but speed deteriorates
Solution Approach 1:
A closed-loop control system continuously monitors the actual steering angle and compares it with the target steering angle from the joystick input. The control device adjusts the steering actuator in real-time to minimize deviations, ensuring both stability and responsiveness
Solution Approach 2:
The steering ratio is made variable rather than fixed, allowing the system to dynamically adjust the relationship between joystick movement and steering wheel movement. This enables the limited joystick range to effectively cover the full steering angle range needed for different driving conditions
Data Source
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AI summary
The invention relates to a forklift truck (1) with a steer-by-wire steering system comprising a joystick (7) as an actuating element and a steering actuator (11). An electronic control unit (13) is provided, which communicates with the joystick (7) on the input side and with the steering actuator (11) on the output side and controls the steering system in a closed control loop. Actuation of the joystick (7) generates a control variable (w) for the closed control loop. Furthermore, a variable steering ratio is provided, by means of which the steering angle range and/or the steering speed of the steering actuator (11) can be changed depending on the travel speed of the forklift truck (1).