Spindle Motor Control Device for Load Fluctuation Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large load fluctuations in spindle motors of machine tools make automatic control of feed rates difficult and reduce the responsiveness of machining conditions, leading to potential machining abnormalities or increased machining time.
Innovation Solution
A motor control device that uses a moving average filter to generate averaged load information by calculating an optimal averaging time based on the spindle's rotation period and the number of cutting teeth, allowing for adaptive control of machining conditions to suppress load fluctuations and maintain responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a first-order filter is used to average load fluctuation, then load fluctuation is suppressed, but responsiveness of control declines due to increased time constant
Solution Approach 1:
The patent applies dynamics by making the averaging time variable rather than fixed. The averaging time calculation unit dynamically adjusts the averaging time based on spindle rotation speed and cutting conditions, allowing the system to adapt between suppression and responsiveness needs in different operating states
Solution Approach 2:
The patent changes the parameter of averaging time from a constant value to a variable value that depends on spindle rotation speed and cutting tooth count. This parameter change allows the system to optimize between load fluctuation suppression and control responsiveness based on actual machining conditions
2Reliability
If automatic control of feed rate is implemented, then machining abnormalities are suppressed, but control becomes difficult when load fluctuation is too large
Solution Approach 1:
The patent introduces an intermediary moving average filter between the load detection and control execution. This intermediary processes the raw load information to generate smoothed averaged load information, making the control input more stable and easier to handle even when original load fluctuations are large
Solution Approach 2:
The system uses feedback by continuously monitoring the averaged load information and adjusting the feed rate accordingly. The averaging time calculation unit also uses feedback from spindle rotation speed to optimize the filtering characteristics in real-time
3Adaptability or versatility
If manual control of feed rate is implemented, then machining conditions can be adjusted, but control becomes difficult when load information fluctuates
Solution Approach 1:
The moving average filter acts as an intermediary that processes fluctuating load information before presenting it to the operator or control system. This intermediary provides stable, averaged load information that is easier to use for manual control decisions
4Reliability
If feed rate is lowered to suppress load fluctuation, then machining abnormalities are prevented, but machining time increases
Solution Approach 1:
The system dynamically adjusts feed rate based on averaged load information rather than reacting to instantaneous fluctuations. This dynamic approach allows maintaining higher feed rates when load is stable while preventing abnormalities when load increases, optimizing both reliability and productivity
Solution Approach 2:
The feedback mechanism uses averaged load information to make informed feed rate adjustments. By using averaged rather than raw load data, the system makes smoother, more accurate decisions that prevent unnecessary feed rate reductions and maintain productivity
Data Source
AI summary
A motor control device is a motor control device which controls a spindle motor in a machine tool, and includes: a moving average filter which moving averages a torque command value or drive current value of the spindle motor for averaging time and generates averaged load information of the spindle motor; and an averaging time calculation unit which calculates, as the averaging time of the moving average filter, a first time of an integral multiple of a period of one rotation of the spindle driven by the spindle motor, or a second time of an integral multiple of a value arrived at by dividing the period of one rotation of the spindle by the number of cutting tooth of the tool.