Power Tool Free-Fall Detection to Prevent False Motor Stops
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Solution Overview
Problem
Power tools often experience false positive free-fall determinations, leading to premature motor stoppage, which can disrupt work operations and require unnecessary task restarts, due to the lack of accurate thresholds and control methods for distinguishing between free-fall and normal movements.
Innovation Solution
A system comprising a motor, sensor, and controller in power tools that measures acceleration, compares it to free-fall thresholds, and initiates a timer to differentiate between free-fall and normal movements, ensuring the motor stops only when the tool has been in free-fall for a predetermined duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a simple acceleration threshold is used to detect free-fall, then the detection response is fast, but false positive detections occur leading to premature motor stoppage
Solution Approach 1:
The system dynamically adjusts the acceleration threshold based on the operational state of the motor. When the motor is running, a higher threshold is applied to accommodate normal vibrations and movements. When the motor is stopped, a lower threshold is used. This dynamic adjustment resolves the contradiction by allowing fast detection when appropriate while preventing false positives during normal operation.
Solution Approach 2:
The system monitors motor state and prepares appropriate threshold values in advance based on whether the motor is running or stopped. This preliminary preparation of detection parameters ensures that when acceleration events occur, the appropriate threshold is already in place, enabling both fast response and accurate detection without waiting for the event to occur first.
2Object-affected harmful factors
If the motor stops immediately upon detecting free-fall acceleration, then safety is improved, but normal operations are disrupted due to false positives
Solution Approach 1:
The motor stop decision is made dynamically based on real-time motor state information. If the motor is running when free-fall acceleration is detected, the motor is stopped to ensure safety. If the motor is already stopped, no additional action is taken, avoiding false disruption of work operations. This dynamic decision-making resolves the contradiction between safety and productivity.
Solution Approach 2:
The system uses feedback from the motor state sensor to modulate the free-fall detection response. The motor state information feeds back into the control logic to determine whether to stop the motor upon detecting free-fall acceleration. This feedback mechanism ensures that safety actions are taken only when appropriate, preventing false positives from disrupting normal operations.
3Measurement precision
If acceleration threshold is lowered to reduce false positives, then detection accuracy improves, but normal movements during operation are incorrectly detected as free-fall
Solution Approach 1:
The acceleration threshold is dynamically adjusted based on motor operational state. During normal operation when the motor is running, a higher threshold is applied to tolerate normal vibrations and movements. When the motor is stopped, a lower threshold is used to detect actual free-fall events. This resolves the contradiction by adapting the detection sensitivity to the operational context.
Solution Approach 2:
Different acceleration thresholds are applied to different operational states of the tool. The system creates local detection criteria tailored to each state: a permissive threshold for operation mode and a sensitive threshold for stopped mode. This local quality approach allows high detection precision without interfering with normal tool handling during operation.
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
This solution effectively prevents premature motor stoppage by accurately distinguishing between free-fall and normal movements, ensuring the power tool stops only when it has been dropped, thus minimizing interruptions and maintaining operational efficiency.
Implementation Method 1
a sensor configured to measure an acceleration of the power tool and generate an output signal related to the acceleration
Data Source
AI summary
A power tool including a motor configured to produce an output, and a sensor configured to measure an acceleration of the power tool along at least one of three spatial axes and generate an output signal related to the acceleration. The power tool further including a controller configured to receive the output signal related to the acceleration of the power tool from the sensor, compare the acceleration of the power tool to a free-fall acceleration threshold, initiate a timer when the acceleration of the power tool corresponds to the free-fall acceleration threshold, compare the timer to a free-fall timer threshold, and stop the motor from producing the output when the timer is greater than or equal to the free-fall timer threshold.