Power Tool Motor Speed Stabilization via Hysteresis Control
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Solution Overview
Problem
Existing power tools experience unstable motor rotational speed due to changes in trigger displacement caused by vibration or user input, leading to inconsistent performance during operations like fastening or loosening tasks.
Innovation Solution
A power tool design incorporating a pressure sensing unit and control circuit that performs hysteresis control of the motor's rotational speed based on measured pressure, distinguishing between increasing and decreasing pressure conditions to maintain stable speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rotational speed of the motor is continuously adjusted based on the pull-in amount of the trigger, then the responsiveness to user input is improved, but the rotational speed becomes unstable due to vibration during work
Solution Approach 1:
The patent applies dynamics by implementing hysteresis control that creates different rotational speed characteristics based on the direction of pressure change. When pressure increases, the motor speed follows one characteristic curve, and when pressure decreases, it follows a different curve, making the system's behavior dynamic rather than static
Solution Approach 2:
The control circuit continuously monitors the pressure on the trigger and adjusts the motor rotational speed accordingly. The feedback mechanism compares current pressure with previous pressure values and adjusts speed based on whether pressure is increasing or decreasing, creating a closed-loop control system that stabilizes rotation despite vibrations
2Adaptability or versatility
If the rotational speed is adjusted according to trigger displacement, then the power tool adapts to user force input, but the rotational speed fluctuates due to vibration caused during work
Solution Approach 1:
The system dynamically adjusts its response characteristics based on the direction of pressure change. By implementing different speed-pressure relationships for increasing versus decreasing pressure, the system adapts to user input while filtering out vibration-induced fluctuations that would otherwise cause instability
Solution Approach 2:
The patent changes the control parameter relationship by implementing hysteresis, where the rotational speed for a given pressure value depends on whether the pressure is increasing or decreasing. This parameter change approach allows the system to maintain adaptability while achieving stability through different operational modes
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
The solution stabilizes the motor's rotational speed even when the trigger's pull-in amount changes due to vibration or user input, ensuring consistent performance by maintaining the rotational speed within a prescribed range.
Implementation Method 1
The pressure sensing unit includes a pressure receiving unit for receiving pressure according to a pull-in amount of the trigger and is configured to measure a magnitude of the pressure received with the pressure receiving unit
Implementation Method 2
The control circuit is configured to perform hysteresis control of the rotational speed of the motor such that the rotational speed of the motor with respect to the measured pressure differs between a case where the measured pressure increases with time and a case where the measured pressure decreases with time
Data Source
Figure 1
Figure 2
Figure 3A~4
AI summary
A power tool configured to stabilize the rotational speed of a motor is provided. A power tool (1) includes a motor (4), a trigger (3), a pressure sensing unit (7), and a control circuit (5). The motor (4) is configured to receive electric power from a battery (241) to rotate a socket (212). The trigger (3) is movably held by a tool body (2). The pressure sensing unit (7) includes a pressure receiving unit (71) for receiving pressure according to a pull-in amount of the trigger (3) and is configured to measure a magnitude of the pressure received with the pressure receiving unit (71). The control circuit (5) is configured to control a rotational speed of the motor (4) based on measured pressure measured by the pressure sensing unit (7). The control circuit (5) is configured to perform hysteresis control of the rotational speed of the motor (4) such that the rotational speed of the motor (4) with respect to the measured pressure differs between a case where the measured pressure increases with time and a case where the measured pressure decreases with time.