Adaptive Threshold Sensor for Power Tool Jamming Detection
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Solution Overview
Problem
Hand-held power tools often experience uncontrolled jamming, leading to potential user injury due to the reaction torque overcoming the operator's holding force, with existing sensors failing to effectively identify and mitigate such events in a variable and adaptive manner.
Innovation Solution
A sensor device with a sensor unit and protective unit that senses motion characteristic values and adjusts triggering threshold values based on frequency, operating mode, and rotational-speed characteristics to control the power tool, including braking or switching off the motor, to prevent uncontrolled rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed triggering threshold value is used for jamming detection, then the device complexity is reduced, but the reliability of jamming detection deteriorates because it cannot adapt to different operating conditions
Solution Approach 1:
The triggering threshold value is changed from a fixed parameter to a dynamic parameter that automatically adapts to different operating conditions. The control unit adjusts the threshold based on detected operating modes (e.g., different drill speeds, hammer modes, or tool configurations), enabling reliable jamming detection across varying operational contexts without requiring manual intervention or complex external calibration systems.
2Measurement precision
If the triggering threshold value is adjusted frequently to improve detection accuracy, then the measurement precision of jamming detection is improved, but the loss of time due to continuous threshold adjustment increases
Solution Approach 1:
The control unit performs preliminary detection of operating conditions and pre-adjusts the triggering threshold value before actual jamming detection is needed. By anticipating operating mode changes and proactively setting appropriate thresholds, the system maintains high detection precision without requiring continuous real-time threshold adjustments during operation, thus minimizing time loss.
3Reliability
If the protective unit continuously monitors motion characteristic values with high sensitivity, then the reliability of safety protection is improved, but the false triggering frequency increases reducing user convenience
Solution Approach 1:
The triggering threshold is differentiated based on specific operating conditions and motion characteristic types. Instead of using a single universal threshold, the control unit applies locally optimized threshold values tailored to each operating mode (e.g., different thresholds for drilling vs. hammering modes, or for different rotational speeds). This localized thresholding maintains high safety reliability by being sensitive to relevant jamming indicators while remaining insensitive to normal operational variations, thereby reducing false triggers.
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
Enhances user safety by adaptively setting and resetting triggering thresholds, reducing the risk of uncontrolled jamming and improving the accuracy of jamming detection, while maintaining user convenience and tool functionality.
Implementation Method 1
the sensor unit comprises at least an acceleration sensor
Implementation Method 2
the sensor unit comprises at least an acceleration sensor, a Hall sensor
Implementation Method 3
the sensor unit comprises at least an acceleration sensor, a Hall sensor, an inertial rotation rate sensor
Data Source
AI summary
The disclosure is based on a sensor device, in particular a hand-held power-tool sensor device, for identifying an uncontrolled occurrence of jamming in the case of a hand-held power tool, having at least one sensor unit, which is provided to sense at least one motion characteristic value of the hand-held power tool, and having a protective unit, which is provided to control the hand-held power tool in dependence on at least one triggering threshold value and the at least one motion characteristic value. It is proposed that the protective unit be provided to set the at least one triggering threshold value in a variable manner and/or to define at least one further triggering threshold value.