Adaptive Impact Blow Detection in Power Tools
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Solution Overview
Problem
Power tools face challenges in delivering a consistent number of impacts across varying motor speeds and battery charges, which affects torque output consistency.
Innovation Solution
A power tool with a motor control unit that employs either an acceleration-based or time-based impact detection algorithm depending on motor speed, ensuring a consistent number of impacts by monitoring motor characteristics and adjusting the detection technique accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single impact detection algorithm is used regardless of motor speed, then the device complexity is reduced, but the measurement precision of impact detection deteriorates
Solution Approach 1:
The system dynamically selects between acceleration-based and time-based impact detection algorithms based on the current motor speed. At low motor speeds, the acceleration-based algorithm is used to accurately detect impacts. At high motor speeds, the time-based algorithm is used. This dynamic adaptation resolves the contradiction by optimizing measurement precision for different operating conditions without requiring a completely complex system redesign.
Solution Approach 2:
The system changes the detection parameter (from acceleration to time) based on the motor speed parameter. When motor speed exceeds a threshold, the system switches from monitoring acceleration changes to monitoring elapsed time between impacts. This parameter change allows the system to maintain high measurement precision across varying motor speeds while avoiding excessive complexity.
2Adaptability or versatility
If the motor speed varies, then the adaptability of the power tool improves, but the consistency of impact number deteriorates
Solution Approach 1:
The system continuously monitors motor speed and provides feedback to the impact detection algorithm selection. Based on this feedback, the system adjusts the detection method to maintain consistent impact counting across varying motor speeds. This feedback mechanism ensures that regardless of whether the motor operates at low or high speed, the impact number consistency is maintained through appropriate algorithm selection.
3Measurement precision
If acceleration-based detection is used at high motor speeds, then the measurement precision is maintained, but the loss of time increases
Solution Approach 1:
The system dynamically adjusts the detection method based on motor speed conditions. At high motor speeds where acceleration changes are minimal and detection would take longer, the system switches to the time-based algorithm which is more efficient. This dynamic adjustment maintains measurement precision by using the appropriate algorithm for each speed range while minimizing detection time.
Data Source
AI summary
A power tool and method of detecting impacts of a power tool that includes a motor driving a hammer to impact an anvil. A motor control unit is configured to determine a motor characteristic indicative of a speed of the motor. When the motor characteristic indicates that the speed of the motor is below a speed threshold, the motor control unit employs an acceleration-based technique to detect a first impact based on a change in motor acceleration and generate a first impact indication in response to detecting the first impact. When the motor characteristic indicates that the speed is above the speed threshold, the motor control unit employs a time-based technique to detect a second impact based on an elapsed time and generates a second impact indication in response to detecting the second impact.