Electric Motor Trigger Control for Current Impact Reduction
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Solution Overview
Problem
Electric tools with trigger switches experience rapid increases in motor current when the trigger is pressed quickly, leading to reduced service life due to excessive current impact.
Innovation Solution
A method of controlling electric motors by detecting trigger position changes, calculating a difference value, and selecting a smoothing coefficient to adjust the output duty ratio using equations such as DN=DN-1*(N-1)+DRN, where DN is the output duty ratio, DN-1 is the previous output duty ratio, N is the smoothing coefficient, and DR is a preset duty ratio based on the trigger position, to manage current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the trigger is pressed quickly to activate the electric motor, then the motor activation speed is improved, but the current increases too fast which reduces the service life of the electric tool
Solution Approach 1:
The patent applies preliminary action by detecting the trigger position change rate before the motor is fully activated. When rapid trigger pressing is detected (high position change rate), the system pre-adjusts the duty ratio increase rate to be slower, preventing excessive current surge before it occurs. This anticipatory control resolves the contradiction by preparing the motor current in advance based on predicted user input patterns.
Solution Approach 2:
The patent implements dynamics by making the duty ratio adjustment rate variable rather than fixed. The controller dynamically adjusts the duty ratio increase rate based on the detected trigger position change rate. When the trigger is pressed quickly, the system increases the duty ratio more gradually; when pressed slowly, the duty ratio increases more rapidly. This dynamic adaptation allows fast motor activation while preventing excessive current impact, thereby extending tool service life.
2Speed
If the duty ratio increases rapidly to respond to trigger pressing, then the motor response speed is improved, but the current impact on the motor increases reducing service life
Solution Approach 1:
The patent applies dynamics by making the duty ratio adjustment rate variable rather than fixed. The controller dynamically adjusts the duty ratio increase rate based on the detected trigger position change rate. When the trigger is pressed quickly, the system increases the duty ratio more gradually; when pressed slowly, the duty ratio increases more rapidly. This dynamic adaptation allows fast motor activation while preventing excessive current impact, thereby extending tool service life.
Solution Approach 2:
The patent implements feedback by continuously monitoring the trigger position and calculating its change rate over time intervals. This feedback mechanism allows the controller to detect rapid trigger pressing and adjust the duty ratio increase rate accordingly. The closed-loop control ensures that the motor current increases at an appropriate rate regardless of how quickly the user presses the trigger, resolving the contradiction between response speed and current impact.
3Device complexity
If a fixed duty ratio is used based on trigger position, then the control simplicity is maintained, but the ability to prevent rapid current increase is lost
Solution Approach 1:
The patent applies preliminary action by detecting the trigger position change rate before the motor is fully activated. When rapid trigger pressing is detected (high position change rate), the system pre-adjusts the duty ratio increase rate to be slower, preventing excessive current surge before it occurs. This anticipatory control resolves the contradiction by preparing the motor current in advance based on predicted user input patterns.
Data Source
AI summary
An example method for controlling an electric motor in an electric tool includes detecting travel of the trigger, selecting a smoothing coefficient N according to travel of the trigger in a predetermined time, driving the electric motor with an output duty ratio which is figured out by a formula in which the smoothing coefficient N is a denominator so as to cause the output duty ratio to be lesser than a preset duty ratio. The methods described will decrease the current impact on electric motors when users pull the trigger.