Striking Tool Motor Control for Stable Plunger Stop Position
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Solution Overview
Problem
Existing striking tools face challenges in stabilizing the stop position of a plunger due to varying drive speeds and difficulties in detecting the peak current, leading to inconsistent performance across different battery voltages and load conditions.
Innovation Solution
A striking tool equipped with a motor, plunger, moving unit, speed variation acquiring unit, and control unit that acquires and controls the motor based on the rotating speed variations, allowing for precise control and stabilization of the plunger's stop position without relying on position detection sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If energization time to the motor is set only based on the battery voltage, then the control method is simple, but the stop position of the plunger cannot be stabilized due to varying drive speeds
Solution Approach 1:
The control unit acquires the rotating speed of the rotor and uses this feedback information to adjust the energization timing. By monitoring the actual rotating speed and comparing it with expected values, the system dynamically adjusts the control parameters to ensure the plunger stops at the correct position, resolving the contradiction between simple control and precise positioning.
Solution Approach 2:
The system changes the control parameter from fixed energization time based only on battery voltage to variable energization timing based on actual rotating speed measurements. This parameter change allows the control system to adapt to varying drive speeds and maintain accurate stop position control.
2Device complexity
If the peak in current is used to determine stop timing, then the control method is simple, but it becomes difficult to detect the peak when start load increases and current reaches upper limit
Solution Approach 1:
Instead of directly using current peak detection, the system uses rotating speed as an intermediary parameter to determine stop timing. The rotating speed provides reliable feedback that is not affected by current saturation, allowing accurate determination of plunger position even when start load increases and current reaches upper limits.
Solution Approach 2:
The system replaces electrical parameter detection (current peak) with mechanical parameter detection (rotating speed). This substitution eliminates the detection problem caused by current saturation while maintaining simple control logic.
3Manufacturing precision
If position detection sensors are added to stabilize plunger stop position, then positioning accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the motor's own rotating speed information, which is already available for control purposes, to determine plunger position and stop timing. This self-service approach eliminates the need for additional position detection sensors while maintaining accurate positioning control.
Solution Approach 2:
The rotating speed acquisition system serves dual purposes: it controls motor operation and simultaneously provides position information for determining when to stop the plunger. This multi-functionality eliminates the need for separate position sensing systems.
Data Source
AI summary
A striking tool includes: a motor including a rotor; a plunger configured to be movable from a bottom dead point to a top dead point by the motor; a moving unit configured to move the plunger from the top dead point toward the bottom dead point; a speed variation acquiring unit configured to acquire an amount of variation in rotating speed of the rotor; and a control unit configured to control the motor, based on the amount of variation acquired by the speed variation acquiring unit.