Forklift Regenerative Braking Torque Control to Prevent Wheel Lock
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Solution Overview
Problem
Existing methods for regenerative braking in industrial trucks often fail to achieve efficient braking with a short stopping distance without additional components, as they struggle to determine the optimal braking torque due to varying ambient conditions, leading to potential wheel blocking or extended braking distances.
Innovation Solution
A method that adjusts regenerative braking torque based on the speed of the driven wheel, reducing torque if the speed is low and increasing it if the speed is above a minimum, ensuring optimal braking without wheel blocking, and combining this with a counter to manage the timing of torque adjustments to prevent premature or delayed braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If regenerative braking torque is increased to reduce braking distance, then braking efficiency is improved, but the drive wheel may lock causing instability
Solution Approach 1:
The braking torque is made dynamic rather than constant. The control unit continuously adjusts the regenerative braking torque based on real-time wheel speed measurements, increasing torque when speed is high and reducing it when speed approaches zero or wheel locking is detected, thereby optimizing braking efficiency while preventing wheel lock
Solution Approach 2:
A feedback mechanism is implemented where the actual wheel speed is continuously measured by a speed measuring device and fed back to the control unit. The control unit compares the measured speed with reference values and adjusts the braking torque accordingly, creating a closed-loop control system that prevents wheel locking while maximizing braking efficiency
2Reliability
If regenerative braking torque is reduced to prevent wheel locking, then wheel stability is maintained, but braking distance increases
Solution Approach 1:
The braking torque is dynamically adjusted based on wheel speed conditions. Rather than using a fixed reduced torque, the system applies high torque when wheel speed is above the minimum threshold and smoothly reduces torque only when necessary to prevent locking, thereby minimizing the impact on braking distance while maintaining wheel stability
Solution Approach 2:
The control unit proactively reduces braking torque before wheel locking actually occurs by monitoring wheel speed and comparing it with minimum speed thresholds. This preliminary action prevents wheel locking from happening in the first place, avoiding the need for corrective measures that would extend braking distance
3Use of energy by moving object
If minimum speed threshold is set low to maximize regenerative braking, then energy recovery is improved, but wheel locking risk increases
Solution Approach 1:
The minimum speed threshold is not fixed but dynamically adjusted based on operating conditions. The control unit can adapt the threshold value to account for factors like surface conditions, load, and vehicle speed, allowing maximum energy recovery under favorable conditions while maintaining safety margins when wheel locking risk is higher
Solution Approach 2:
The system changes the parameter of minimum speed threshold based on real-time conditions. Rather than using a single fixed threshold, the control unit can modify this parameter to optimize the balance between energy recovery and wheel locking prevention, thereby resolving the contradiction between maximizing energy recovery and maintaining reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise control of braking torque, preventing wheel blocking and minimizing braking distance, ensuring efficient regenerative braking without overloading electrical components, and achieving a braking process close to optimal with minimal deviation from theoretical values.
Implementation Method 1
an electric drive motor (3) is controlled as a generator, so that an electric current is generated by the braking movement of the vehicle
Data Source
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AI summary
A method for regenerative braking of a forklift truck with a speed measuring device for a driven wheel and a regenerative braking device whose braking torque is adjustable, comprising the following method steps: • Generating a regenerative braking torque (a) for the driven wheel in response to a braking request signal, • Determining a rotational speed (n_actual) of the driven wheel and an applied regenerative braking torque (a_actual), • Reducing the braking torque (a) by a predetermined first value (a_reduced) if the rotational speed (n_actual) of the driven wheel is below a minimum rotational speed (n_min) for a predetermined minimum duration (z), • Increasing the braking torque (a) by a second predetermined value (a_plus) if the rotational speed (n_actual) of the driven wheel is greater than the minimum rotational speed (n_min) and the applied braking torque (a_actual) is less than a predetermined maximum braking torque (a_max).