Grindstone Contact Detection Using Servo Control Feedback
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Solution Overview
Problem
Existing methods for detecting contact between a grindstone and a workpiece are time-consuming and prone to mis-detection due to unstable motor power, making accurate contact detection difficult.
Innovation Solution
A method involving controlling actuators to move a tool holder relative to a workpiece holder, using a servo motor to detect contact based on changes in motor control values, such as current, position, and speed feedback, without requiring additional sensors, and utilizing control axes perpendicular to the tool rotation axis for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If motor power is increased to rotate the grindstone at specified speed, then rotational speed is achieved, but power stability deteriorates and detection accuracy worsens
Solution Approach 1:
The patent introduces a second motor as an intermediary device to control the holder's position along the control axis. This mediator allows the primary motor to focus on rotation while the secondary motor handles positioning, separating the functions and improving overall system stability and detection accuracy.
2Productivity
If threshold detection is used for contact detection, then detection speed improves, but detection accuracy deteriorates due to unstable power
Solution Approach 1:
The patent employs feedback control by continuously monitoring the control values (current, position, speed) of the motor and comparing them against reference values. When deviations exceed predetermined thresholds, contact is detected. This feedback mechanism enables both rapid response and high accuracy by dynamically adjusting to power fluctuations.
3Measurement precision
If additional sensors are added for contact detection, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes the motor serve multiple functions: both driving the grindstone rotation and detecting contact through monitoring its control values. This multi-functionality eliminates the need for separate contact detection sensors, maintaining high detection accuracy while avoiding increased system complexity.
Solution Approach 2:
The system uses its own motor control values to detect contact, allowing the motor to serve itself for both actuation and sensing. This self-service approach eliminates external sensors and simplifies the overall system architecture.
4Use of energy by moving object
If motor power is reduced after reaching predetermined speed, then energy consumption decreases, but detection reliability deteriorates due to instability
Solution Approach 1:
The feedback control system continuously monitors motor control values and compares them with reference values. This allows reliable contact detection even when motor power fluctuates during the settling period, maintaining detection reliability while allowing energy-efficient operation at reduced power.
Data Source
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AI summary
A method for a machine tool to detect contact between a grindstone and a workpiece includes controlling at least one actuator to move a tool holder in a movement direction relative to a workpiece holder configured to hold the workpiece. The tool holder is configured to hold the grindstone in a manner in which the grindstone is rotatable about a tool rotation axis. The method also includes controlling a motor to make one holder selected from the tool holder and the workpiece holder stationary in a direction along a control axis crossing the tool rotation axis and crossing the movement direction. The motor is different from the at least one actuator and configured to move the one holder along the control axis. The method also includes detecting the contact between the grindstone and the workpiece based on a change in a control value of the motor.