Numerical Controller Adaptive Acceleration for Induction Motor Stability
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Solution Overview
Problem
Induction motors in machine tools face challenges with heat generation and stability during position control, leading to increased machining errors and synchronization issues when switching from speed control to position control, as they cannot immediately accelerate or decelerate with maximum torque due to weakened magnetic flux.
Innovation Solution
A numerical controller that includes a storage unit for maximum acceleration data, a magnetic flux acquisition unit, and an acceleration change unit that adjusts the position command's acceleration based on the current magnetic flux amount, allowing for stable position control by reducing acceleration when magnetic flux is low, thereby preventing overheating and improving synchronization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If magnetic flux is weakened to suppress heat generation in the induction motor, then heat generation is reduced, but the motor cannot immediately accelerate or decelerate with maximum torque, causing position control instability and synchronization errors
Solution Approach 1:
The patent applies dynamics by making the acceleration command adaptive rather than fixed. The acceleration command is dynamically adjusted based on the ratio of actual magnetic flux to reference magnetic flux, allowing the system to optimize between heat suppression and responsive acceleration/deceleration in real-time operational conditions
Solution Approach 2:
The patent changes the acceleration parameter based on magnetic flux conditions. When magnetic flux is weakened to suppress heat, the acceleration command is proportionally reduced to match the motor's actual capability, preventing control instability while maintaining heat suppression benefits
2Speed
If acceleration is increased to improve responsiveness to position commands, then position control responsiveness is improved, but heat generation increases due to higher excitation current requirements
Solution Approach 1:
The patent adjusts the acceleration parameter based on magnetic flux levels. When magnetic flux is reduced to suppress heat generation, the acceleration command is proportionally reduced to match the motor's actual capability, preventing control instability while maintaining heat suppression benefits
Solution Approach 2:
The system uses feedback from the magnetic flux sensor to continuously monitor actual magnetic flux levels and adjusts the acceleration command accordingly. This closed-loop feedback ensures acceleration remains within the motor's capability envelope, preventing both overheating and control instability
3Manufacturing precision
If position control is implemented with synchronous operation between spindle motor and feed axis motor, then machining precision is improved, but the induction motor cannot follow position commands accurately when magnetic flux is weakened
Solution Approach 1:
The patent adjusts the acceleration parameter based on magnetic flux levels. When magnetic flux is reduced to suppress heat generation, the acceleration command is proportionally reduced to match the motor's actual capability, preventing control instability while maintaining heat suppression benefits
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
This solution effectively suppresses heat generation and ensures stable position control during acceleration and deceleration, reducing machining errors and maintaining synchronization accuracy between spindle and feed axis motors.
Implementation Method 1
an induction motor is a motor that causes an excitation current to flow into a stator coil to generate a rotating magnetic field and generate an induction current in a rotor so that the rotor rotates with the electromagnetic force
Implementation Method 2
a magnetic flux amount acquisition unit (for example, a magnetic flux amount acquisition unit 102 to be described later) that acquires a present magnetic flux amount of the spindle motor
Data Source
AI summary
A numerical controller for controlling a machine tool including a spindle motor formed of an induction motor includes: a storage unit that stores a maximum acceleration at which the spindle motor can operate when a magnetic flux amount of the spindle motor reaches its maximum; a magnetic flux amount acquisition unit that acquires a present magnetic flux amount of the spindle motor; and an acceleration change unit that changes an acceleration of a position command based on a maximum acceleration of the spindle motor stored in the storage unit according to a magnetic flux amount at the start of movement of the spindle motor acquired by the magnetic flux amount acquisition unit when the spindle motor is operated by position control using a position command.