Electric Work Machine Current Control for Sustained Load Torque
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Solution Overview
Problem
Existing electric work machines face challenges in maintaining output torque when continuously receiving a relatively large load, leading to insufficient output and potential work interruption.
Innovation Solution
The electric work machine incorporates a controller that measures the drive current, sets a maximum correction value, and adjusts the control parameter to decrease the drive current when it reaches a threshold, allowing for continuous operation and increased drive current as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive current is continuously inhibited when the motor continuously receives a relatively large load, then the drive current is reduced, but the output torque becomes insufficient and work cannot continue
Solution Approach 1:
The patent applies dynamics by making the current inhibition dynamic rather than static. The controller dynamically adjusts the degree of current inhibition based on whether the overload is momentary or continuous, and whether the motor is in acceleration or deceleration phase. This allows the system to adapt its protection strategy to the actual operating conditions, preventing excessive inhibition during continuous large load operations while still protecting against momentary overloads.
Solution Approach 2:
The patent changes the control parameter (drive current) based on different operating conditions. By detecting whether the overload is momentary or continuous, and whether the motor is accelerating or decelerating, the controller adjusts the current inhibition level accordingly. This parameter change approach allows the system to maintain sufficient output torque during continuous large load operations while still providing protection during momentary overloads.
2Productivity
If the drive current is not inhibited when the motor receives a momentary large load, then the output torque is maintained, but the motor may stop or be damaged
Solution Approach 1:
The patent applies preliminary anti-action by preemptively inhibiting the drive current when a momentary large load is detected. The controller monitors the drive current and, upon detecting a momentary overload condition, immediately applies current inhibition to prevent motor stoppage or damage. This preliminary protective action occurs before the motor can be damaged, while the system maintains the ability to recover quickly once the momentary load passes.
Solution Approach 2:
The patent uses feedback by continuously monitoring the drive current and motor operating conditions, then adjusting the current inhibition level accordingly. The controller receives feedback about whether the overload is momentary or continuous, and whether the motor is in acceleration or deceleration phase, and uses this feedback to dynamically adjust the protection strategy. This closed-loop feedback mechanism ensures appropriate protection while maintaining productivity.
3Reliability
If the correction value is not limited to a maximum value, then the drive current can be reduced more aggressively, but the motor may stop during continuous large load operation
Solution Approach 1:
The patent applies dynamics by making the correction value adaptive rather than fixed. The controller dynamically determines the correction value based on whether the overload is momentary or continuous, and whether the motor is in acceleration or deceleration phase. During continuous large load operations, the correction value is limited to a maximum value that prevents motor stoppage, while during momentary overloads, larger correction values can be applied for more aggressive current inhibition.
Solution Approach 2:
The patent changes the correction value parameter based on different operating conditions. By detecting whether the overload is momentary or continuous, and whether the motor is accelerating or decelerating, the controller adjusts the correction value within appropriate limits. This parameter change approach allows the system to apply strong current inhibition during momentary overloads while maintaining continuous operation capability during sustained large load conditions.
Data Source
AI summary
The electric work machine in one aspect of the present disclosure includes an output shaft, a motor, a current measuring circuit, and a controller. The current measuring circuit measures a current value, the current value corresponding to a magnitude of a drive current flowing through the motor. The controller sets a maximum value and a threshold. The controller calculates the correction value less than or equal to the maximum value so that the drive current decreases, in response to the current value having reached the threshold. The controller subtracts, from the control parameter, the correction value calculated, thereby correcting the control parameter. The controller drives the motor based on the control parameter corrected.