Machine Tool Servo Control During Main Spindle Voltage Drop
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Solution Overview
Problem
Machine tools experience alarms of excessive error due to variations in power source voltage, particularly when the driver for the main spindle starts, as existing technologies do not effectively control the acceleration/deceleration time constant of the servo motor based on the driver's state.
Innovation Solution
A machine tool and control device that include a current detector, a voltage detector, and a controller. The controller adjusts the acceleration/deceleration time constant of the servo motor based on the detected current and voltage values immediately after starting the main spindle, changing it from a first time constant to either a second or third time constant that is lower or higher in power consumption respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the acceleration/deceleration time constant is kept at a standard value for normal operation, then the servo motor responds quickly to commands, but voltage drops during main spindle startup cause excessive error alarms and unstable operation
Solution Approach 1:
The acceleration/deceleration time constant is made dynamic rather than fixed. The controller automatically adjusts the time constant based on the operational state of the main spindle driver, switching between a first time constant during normal operation and a second time constant during main spindle startup. This dynamic adjustment resolves the contradiction by adapting the servo motor's response characteristics to match the current system conditions, ensuring stability when voltage fluctuations occur while maintaining efficiency during normal operation.
2Reliability
If the acceleration/deceleration time constant is increased to reduce current demand during voltage drops, then excessive error alarms are avoided, but the servo motor's reactivity and speed response deteriorate
Solution Approach 1:
The acceleration/deceleration time constant parameter is changed based on operational conditions. During main spindle startup when voltage drops occur, the controller switches to a second time constant that is larger than the first, which reduces the rate of current change and prevents excessive error alarms. During normal operation, the first time constant is used to maintain fast response. This parameter change strategy resolves the contradiction by optimizing the time constant value for each operational phase.
3Reliability
If the acceleration/deceleration time constant is adjusted dynamically based on main spindle driver state, then stable operation is maintained during voltage variations, but the control system complexity increases
Solution Approach 1:
The control system uses feedback from the main spindle driver's operational state to automatically adjust the acceleration/deceleration time constant. The controller monitors whether the main spindle driver is in the startup phase or normal operation mode, and based on this feedback, selects the appropriate time constant value. This feedback mechanism resolves the contradiction by providing automatic, condition-based adjustment without requiring complex manual intervention or overly sophisticated control algorithms.
Data Source
AI summary
A machine tool includes a driver that drives a main spindle for holding a workpiece rotatably, a servo motor that drives a tool for machining the workpiece held on the main spindle, a power source that supplies electric power to at least the driver and the servo motor, a current detector that detects a current value to be inputted into the servo motor, a storage that stores an upper limit of the current value to be inputted into the servo motor, and a controller that controls the servo motor to execute driving control of the tool. When a current value detected by the current detector exceeds the upper limit of the current value immediately after starting the main spindle, the controller changes an acceleration/deceleration time constant from a first time constant to a second time constant that is lower in power consumption than the first time constant, thereby controlling the servo motor.