Power Tool Motor Control for Reduced-Output Overload Protection
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Solution Overview
Problem
Existing power tools experience frequent and disruptive shutdowns due to immediate overload protection activation, leading to decreased operational efficiency and user satisfaction.
Innovation Solution
Implementing a motor control mechanism that transitions between two operating states based on load detection, using a load detector and controller to manage overload protection by adjusting PWM duty cycle, frequency, or waveform, and switching states based on predefined thresholds and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If immediate overload protection activation is implemented, then motor damage is prevented, but operational efficiency decreases due to frequent shutdowns
Solution Approach 1:
The system dynamically adjusts the motor operating state between first and second states based on real-time load detection. When overload is detected, the controller transitions the motor to a second operating state with reduced output, and can further transition to a third state with zero output if overload persists, creating a dynamic response rather than immediate static shutdown
Solution Approach 2:
The controller monitors load parameters and transitions the motor to a reduced output state before complete overload damage can occur. This preliminary protective action allows the system to prepare for potential damage by gradually reducing load rather than waiting for critical failure conditions
2Productivity
If the motor is transitioned to a second operating state with reduced output, then shutdown frequency is reduced, but motor protection capability must be maintained
Solution Approach 1:
The controller continuously monitors load parameters and uses this feedback to determine when to transition between operating states. The system monitors whether the load exceeds thresholds and adjusts the motor state accordingly, creating a closed-loop control system that maintains protection while optimizing operation
Solution Approach 2:
The system changes operational parameters by transitioning between different motor operating states with different output levels. The controller adjusts PWM duty cycle, frequency, or waveform to achieve different output states, allowing the motor to operate at reduced power when needed while maintaining protection capabilities
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
Reduces the frequency of power tool shutdowns, enhancing user experience by allowing smoother operation and preventing motor damage while maintaining protection against overloading.
Implementation Method 1
a load detector configured to detect a changed load by measuring a change of a first physical quantity related to the motor operation
Implementation Method 2
the motor has a smaller duty ratio of Pulse Width Modulation (PWM) in the second operating state than in the first operating state
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The present disclosure provides an electric power tool and a method of controlling the same. The power tool comprises a motor, a load detector configured to detect a changed load by measuring a change of a first physical quantity related to the motor operation; a controller configured to transition the motor from a first operating state to a second operating state when it is detected that the first physical quantity deviates from the first threshold and simultaneously deviates from the second threshold different from the first threshold in the same direction for a cumulative time reaching a pre-defined period of time; and is further configured to transition the motor from the second operating state back to the first operating state upon detection of a change of a second physical quantity of the motor by a predefined amount; wherein the motor has a reduced output in the second operating state than in the first operating state. According the present disclosure, when the tool experiences an overload, it maintains a reduced output level to remind that the tool is currently overloaded, and enables the restoration of normal output once the overload is alleviated.