Machine Tool Collision Detection With State-Based Acceleration Thresholds
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Solution Overview
Problem
Existing collision detection methods in machine tools are prone to errors due to varying load torques in cutting and rapid traverse states, and require cumbersome adjustments based on tool changes, leading to inaccurate collision detection.
Innovation Solution
Implementing an acceleration sensor to detect collisions by setting threshold values based on the control state, with distinct thresholds for cutting and non-cutting operations, and adjusting these thresholds according to the operation mode, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the torque threshold value is set based on the load torque in the cutting feed state, then collision detection during cutting is improved, but false detection occurs during rapid traverse due to higher load torque
Solution Approach 1:
The patent applies dynamics by making the threshold value adaptive rather than fixed. The threshold dynamically changes based on the current control state (cutting feed, rapid traverse, or other feed states). This allows the system to maintain high detection accuracy during cutting while avoiding false detections during rapid traverse, as each state has its own appropriately calibrated threshold value.
Solution Approach 2:
The patent implements parameter changes by modifying the threshold value parameter according to the control state. Different threshold parameters are set for different operational modes: a lower threshold for cutting feed state to detect actual collisions, and a higher threshold for rapid traverse state to accommodate normal operational variations. This parameter adaptation resolves the contradiction between detection sensitivity and false alarm prevention.
2Reliability
If the torque threshold value is set high based on the load torque in the rapid traverse state, then false detection during rapid traverse is reduced, but collision detection during cutting control becomes unreliable
Solution Approach 1:
The system dynamically adjusts the threshold based on operational state. During rapid traverse, a higher threshold is applied to maintain reliability and avoid false detections. During cutting feed, the system switches to a lower threshold to ensure accurate collision detection. This dynamic adaptation allows the same system to satisfy both reliability and precision requirements under different operating conditions.
Solution Approach 2:
The patent changes the threshold parameter value according to the control state. By setting state-dependent thresholds, the system achieves high reliability during rapid traverse (where higher thresholds prevent false alarms) while maintaining high detection accuracy during cutting operations (where lower thresholds enable sensitive collision detection).
3Measurement precision
If the torque threshold value is adjusted each time a tool is mounted to account for weight changes, then detection accuracy is improved, but operational complexity and time consumption increase
Solution Approach 1:
The patent segments the threshold setting by control state rather than by tool type. Instead of requiring separate threshold adjustments for each tool weight, the system divides operations into distinct states (cutting feed, rapid traverse, other feed) and applies appropriate thresholds to each segment. This eliminates the need for manual reconfiguration when tools are changed.
Solution Approach 2:
The patent creates a universal threshold setting mechanism that works across all tool types without requiring tool-specific calibration. The control state-based threshold system serves multiple functions: it handles different tool weights, different operational modes, and different load conditions through a single unified approach. This multi-functional system maintains detection accuracy while eliminating cumbersome adjustment procedures.
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
Accurately detects collisions in machine tools by minimizing false positives during cutting operations and ensuring detection during rapid traverses without tool-specific adjustments.
Implementation Method 1
an acceleration sensor that is provided on the movable body and detects acceleration of the movable body
Data Source
AI summary
A machine tool includes: a movable body that supports a tool; a feed drive unit that feed-drives the movable body; a numerical control unit that controls the feed drive by the feed drive unit to perform cutting by the tool; an acceleration sensor that is provided on the movable body and detects acceleration of the movable body; and a command unit that outputs a stop command to stop driving of the feed drive unit to the numerical control unit when the acceleration of the movable body exceeds a threshold value set in advance on the basis of an output of the acceleration sensor. The command unit sets the threshold value to a first threshold value in a cutting control state, and sets the threshold value to a second threshold value lower than the first threshold value in a feed control in a non-cutting control state.