CNC Motor Deceleration Control via Dynamic Power Limiting
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Solution Overview
Problem
CNC machine tools face inefficiencies in motor deceleration, leading to prolonged operation times due to the inability to quickly and safely reduce motor speed without overloading the motor drive system.
Innovation Solution
A method for calculating a present rate of deceleration for a motor in a CNC machine tool based on its current speed and a reference rate, ensuring that the power generated during deceleration does not exceed the motor drive system's maximum power rating, thereby preventing overload and optimizing deceleration rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor decelerates quickly to reduce operation time, then productivity is improved, but the motor drive system may be overloaded
Solution Approach 1:
The patent applies dynamics by making the deceleration rate variable rather than constant. The controller continuously adjusts the deceleration rate based on real-time power generation feedback, allowing the system to operate at maximum deceleration when safe and reduce deceleration when power limits are approached. This dynamic adjustment resolves the contradiction by enabling fast deceleration when possible while preventing overload when necessary.
Solution Approach 2:
The patent implements feedback control by monitoring the power generated during deceleration and using this information to adjust the deceleration rate. The controller calculates instantaneous power based on motor parameters and deceleration rate, then modifies the deceleration profile accordingly. This closed-loop feedback mechanism allows the system to achieve rapid deceleration while automatically preventing motor drive system overload.
2Ease of operation
If a fixed reference deceleration rate is used, then control simplicity is maintained, but the system cannot adapt to varying power conditions
Solution Approach 1:
The system transitions from a static fixed deceleration rate to a dynamic adaptive deceleration rate. While maintaining the simplicity of a reference deceleration rate as a baseline, the system dynamically adjusts the actual deceleration rate based on real-time power conditions. This allows the control mechanism to remain simple in structure while becoming highly adaptable to varying operational conditions.
Solution Approach 2:
The patent changes the deceleration rate parameter dynamically based on power conditions. Instead of using a single fixed parameter, the system adjusts the deceleration rate parameter in real-time according to measured power generation. This parameter adaptation enables the system to maintain simplicity while achieving versatility across different operating conditions.
Data Source
AI summary
A method for decelerating a motor in a computer numerical controlled machine tool is provided. The method includes calculating a present rate of deceleration DP, for a motor of a motor drive system, based on a present speed SP of the motor, a reference speed SR of the motor, and a reference rate of deceleration DR of the motor. The method also includes decelerating the motor from SP according to DP. The motor drive system comprises a maximum power rating that defines a maximum power, generated by the motor while decelerating, that can be dissipated without overloading the motor drive system. DR is a rate of deceleration such that power, generated by the motor while decelerating from SR according to DR, is equal to the maximum power rating. Power, generated while decelerating the motor from SP according to DP, is equal to or less than the maximum power rating.