Dynamic Steering Angle Limiting for Forklift Overturn Prevention
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Solution Overview
Problem
Existing solutions for preventing forklift overturning by reducing speed deteriorate workability and may still result in overturning during abrupt steering with small radius turns before speed reduction occurs.
Innovation Solution
A steer-by-wire type industrial vehicle equipped with sensors to detect steering and wheel angles, traveling speed, load weight, and load height, which calculates and limits the wheel angle to prevent overturning, and includes a warning system to prevent operator errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If speed reduction is used to prevent overturning, then overturning prevention is improved, but workability deteriorates
Solution Approach 1:
The system dynamically changes the steering angle parameter based on vehicle speed, load weight, and load height. At high speeds with heavy loads, the maximum steering angle is limited to prevent overturning, while at lower speeds the full steering range is available, maintaining workability without compromising safety
Solution Approach 2:
The steering angle limitation is not fixed but dynamically adjusted based on real-time operating conditions (speed, load weight, load height). The control unit continuously monitors these parameters and adjusts the permissible steering angle range accordingly, allowing full steering capability when safe and restricting it only when necessary
2Reliability
If speed reduction is used to prevent overturning, then overturning prevention is improved, but response time increases
Solution Approach 1:
The system performs preliminary action by proactively limiting the steering angle before an overturning condition can develop. The control unit calculates the safe steering angle range based on current speed and load conditions and restricts steering input within this range, preventing dangerous situations before they arise rather than reacting after speed reduction is needed
3Reliability
If steering angle is limited to prevent overturning, then overturning prevention is improved, but steering operability worsens
Solution Approach 1:
The system changes the steering angle parameter dynamically based on operating conditions. When speed is high and load is heavy, the maximum steering angle is reduced to prevent overturning. When conditions are safe, the full steering angle range is restored, maintaining natural steering operability without artificial limitations
Data Source
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AI summary
A control unit (30) includes: a steered wheel angle control unit for changing a steered angle of rear wheels so that an angle of a steering handle (15) corresponds to an angle of the rear wheels, based on signals from a steering angle sensor (21) and a steered wheel angle sensor (22); a gravity center height calculation unit configured to calculate a gravity center height obtained by combining a forklift and a load based on a weight of the load detected by a weight sensor (43) and a height position of the load detected by a position sensor (44); an angle calculation unit configured to calculate an angle of the rear wheels corresponding to a minimum turning radius at which a vehicle does not turn over based on the gravity center height calculated by the gravity center height calculation unit and a speed of the vehicle detected by a speed sensor (42); a steered wheel angle limitation unit configured to limit the angle of the rear wheels based on an angle of the rear wheels corresponding to the minimum turning radius calculated by the angle calculation unit; a steering angle limitation unit configured to control an angle of a steering handle (15) based on the angle of the rear wheels corresponding to the minimum turning radius calculated by the angle calculation unit; and a warning notification unit configured to execute a warning notification based on the angle of the rear wheels corresponding to the minimum turning radius calculated by the angle calculation unit.