Machine Tool Drop Detection Using 3D Acceleration Thresholds
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Solution Overview
Problem
Existing machine tools with switching devices having a catch function do not reliably switch off when dropped, posing safety risks due to continued operation of moving parts, and existing sensor-based solutions are complex and prone to errors from user positioning and environmental interference.
Innovation Solution
Implementing a method that uses a machine tool's existing acceleration sensors to detect drops by recording and comparing total acceleration in three dimensions against predetermined threshold values, triggering a state change such as switch-off if the acceleration falls below a threshold for a specified time, thereby ensuring safe and reliable shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensors are integrated in the handle of the machine tool to detect user contact, then the machine tool can detect whether it is being held by a user, but the integration becomes very complex and laborious due to limited space
Solution Approach 1:
The patent extracts the detection function from the handle area and relocates it to the main body of the machine tool. The acceleration sensor is mounted on the machine tool body rather than the handle, eliminating the complexity of integrating sensors in the limited handle space while maintaining the ability to detect drop conditions through acceleration measurements.
2Reliability
If capacitive sensors are used in the grip region to detect user contact, then the machine tool can detect user holding, but the user's hand must be positioned very precisely over the sensors to be detected
Solution Approach 1:
The patent replaces the capacitive sensor-based detection system with an acceleration sensor-based detection system. Instead of measuring electrical capacitance changes that require precise hand positioning, the system measures mechanical acceleration forces. This substitution eliminates the need for precise user positioning while reliably detecting drop conditions through acceleration threshold comparisons.
3Reliability
If capacitive sensors are used in the grip region, then the machine tool can detect user contact, but the detection may be hampered by dirt or by the user wearing a glove
Solution Approach 1:
The patent substitutes the capacitive sensing mechanism with an acceleration sensing mechanism. The acceleration sensor measures mechanical motion and gravitational forces, which are not affected by environmental factors such as dirt or gloves. This replacement eliminates the harmful effects that plague capacitive sensors while maintaining reliable detection of drop conditions.
4Adaptability or versatility
If the machine tool uses a switching device with a catch function, then the machine remains active when dropped, but this poses safety risks as the tool continues to move and rotate
Solution Approach 1:
The patent implements a feedback mechanism where the acceleration sensor continuously monitors the machine tool's motion state and provides information to the control unit. When the control unit detects acceleration patterns consistent with a drop (exceeding threshold values for specified time periods), it automatically triggers a shutdown command to the drive unit, stopping the tool's rotation. This closed-loop feedback system eliminates the safety risks associated with catch-function switches while preserving their operational versatility.
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 method provides a simple, efficient, and reliable way to detect drops and switch off the machine tool quickly, minimizing safety risks by leveraging existing acceleration data without additional hardware, ensuring early detection and swift shutdown.
Implementation Method 1
recording an acceleration of the machine tool in the three spatial directions, whereby the acceleration values x, y and z are obtained
Implementation Method 2
ascertaining a total acceleration of the machine-tool total acceleration based on the acceleration values x, y and z; comparing the total acceleration to a threshold value a_drop; changing an operating state of the machine tool if the total acceleration falls below the threshold value a_drop for longer than a time period t_drop
Data Source
AI summary
Various methods for changing an operating state of a machine tool are provided. A machine tool has an acceleration sensor, wherein the acceleration of the machine tool may be recorded in the three spatial directions by the acceleration sensor. Based on these values, a total acceleration may be ascertained, which may be compared with a threshold value a_drop. The machine tool may be switched off, for example, or change its operating state if the total acceleration exceeds the threshold value a_drop for longer than a time period t_drop. According to an alternative method for changing an operating state of a machine tool, the machine tool may be switched off or change its operating state if the total acceleration is below the threshold value a_drop for longer than a time period t_min_drop_impact and exceeds a second threshold value a_impact within a time period t_post_drop_impact. A machine tool for carrying out one of the methods for changing an operating state of the machine tool.