Motor Control Device for Machine Tool Spindle
Solution Overview
Problem
Induction motors used in machine tools face challenges with heat generation and responsiveness during speed control and position control, particularly when using magnetic flux weakening technology, which results in insufficient torque and extended acceleration times due to delayed magnetic flux rise.
Innovation Solution
A motor control device that includes an advance detection unit to pre-read operation commands and an advance change unit to increase the secondary magnetic flux of the induction motor before a change in the operation command, allowing for timely adjustment of the excitation current or magnetic flux command to ensure sufficient torque and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If magnetic flux weakening technology is used to reduce heat generation during light load, then heat generation is reduced, but torque becomes insufficient and acceleration time extends when speed command changes
Solution Approach 1:
The control device predicts future speed command changes by analyzing the operation program in advance, and proactively adjusts the magnetic flux before the actual change occurs. This preliminary action ensures that when acceleration is needed, the magnetic flux is already at an appropriate level, eliminating the delay that would otherwise occur after the speed command change.
Solution Approach 2:
The control device dynamically adjusts the magnetic flux based on predicted operation conditions rather than using a fixed weakening strategy. By continuously monitoring the operation program and predicting future demands, the system optimizes magnetic flux in real-time, transitioning from static magnetic flux weakening to dynamic adjustment that adapts to upcoming load requirements.
2Use of energy by moving object
If magnetic flux weakening is applied during light load, then energy efficiency improves, but control responsiveness declines when switching from speed control to position control
Solution Approach 1:
The system predicts control mode changes by analyzing the operation program in advance and adjusts the magnetic flux before the actual switching occurs. This ensures that when position control is initiated, the magnetic flux is already optimized for the upcoming high-responsiveness requirement, eliminating the lag that would otherwise occur during mode transition.
Solution Approach 2:
The control device uses feedback from the predicted operation program to continuously optimize magnetic flux levels. By comparing predicted future conditions with current magnetic flux states, the system makes proactive adjustments that maintain both energy efficiency during light load and high responsiveness when control mode changes are anticipated.
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 solution effectively reduces heat generation and enhances control responsiveness by ensuring sufficient torque is available during acceleration and mode switching, shortening acceleration times and maintaining high control responsiveness even during light loads.
Implementation Method 1
The induction motor is a motor that causes a rotating magnetic field to be generated by flowing excitation current to the stator coil, as well as causing induction current to generate in the rotor, in which the rotor rotates so as to follow the rotation of the rotating magnetic field by way of this electromagnetic force.
Implementation Method 2
there is a magnetic flux weakening technology which weakens the magnetic flux of the rotating magnetic field or excitation current
Data Source
AI summary
A motor control device controls an induction motor driving a spindle of a machine tool, and includes: a spindle control unit that controls a rotational position or rotational speed of the spindle, and a secondary magnetic flux of the induction motor in accordance with an operation command based on an operation program of the machine tool; an advance detection unit that pre-reads the operation program, and detects a change in the operation command requiring to increase the secondary magnetic flux of the induction motor in advance; and an advance change unit that causes the secondary magnetic flux of the induction motor to increase prior to a change in the operation command in the spindle control unit, in a case of a change in the operation command being detected by the advance detection unit.