Forklift Speed Control via Steering Angle Thresholds
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Solution Overview
Problem
Industrial trucks experience instabilities due to centrifugal forces during high-speed cornering, particularly with unloaded counterbalanced forklifts, where the center of gravity shifts, and existing electric steering systems often result in significant deviations between desired and actual steering signals, leading to unnecessary speed restrictions that impair operational efficiency.
Innovation Solution
A method for controlling industrial trucks that limits the maximum driving speed based on the absolute value of the desired or actual steering angle, using a characteristic curve to adjust the driving speed only above a threshold, ensuring safe operating conditions and precise speed limitations, thereby preventing unintended movements and maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum driving speed is limited as a function of the steering angle to prevent instabilities during high-speed cornering, then the stability and safety of the industrial truck is improved, but the driving speed is unnecessarily restricted even when the steering angle is small, reducing operational efficiency
Solution Approach 1:
The patent applies parameter changes by using a threshold value for the steering angle below which no speed limitation is applied. Only when the steering angle exceeds this threshold does the system begin to limit the driving speed based on the steering angle. This resolves the contradiction by changing the parameter (steering angle threshold) to distinguish between normal steering operations that should not restrict speed and actual cornering situations that require speed limitation for stability.
2Reliability
If the driving speed is limited based on the desired steering signal, then the stability during cornering is improved, but the deviation between desired and actual steering signals causes incorrect speed limitations, reducing handling precision
Solution Approach 1:
The patent uses feedback by continuously monitoring the actual steering angle and comparing it with the desired steering signal. The system applies speed limitation based on the actual steering angle (or a combination of desired and actual angles), which is fed back from the steering system. This feedback mechanism ensures that speed limitations are applied accurately according to the real steering state, compensating for deviations between desired and actual steering signals.
3Reliability
If the maximum driving speed is severely restricted to ensure safety during cornering, then the stability is improved, but the work processes experience delays and goods handling performance deteriorates
Solution Approach 1:
The patent applies partial action by implementing speed limitation only partially - specifically, only when the steering angle exceeds a defined threshold value. For small steering angles within the threshold, no speed limitation is applied, allowing full driving speed. This partial application of speed restriction maintains safety for actual cornering while avoiding unnecessary speed reductions during normal steering operations, thus reducing work process delays.
Data Source
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AI summary
In a method for controlling a forklift truck with a control device that regulates the travel speed of the forklift truck based on a travel speed setpoint signal (4) from a travel signal transmitter (2) and with an electric steering system, in which the control device, based on a steering setpoint signal (6) from a steering control device (13), adjusts the steering angle of at least one steered wheel by means of an actuator, whereby an actual steering angle value (7) is detected, and wherein the control device limits the maximum travel speed depending on the steering angle, in particular by limiting the travel speed setpoint signal (4), the control device determines the maximum value of steering setpoint signal (6) and steering angle actual value (7) and the travel speed is limited depending on the maximum value.