Servomotor Control Device with Dynamic Compensator Switching
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Solution Overview
Problem
Existing control devices for servomotors used in machine tools face challenges in maintaining control stability and response, particularly in high frequency ranges, due to the use of PI compensators in current control loops, which can lead to resonance and deteriorated stability.
Innovation Solution
A control device with a current control loop selecting unit that switches between a PI compensator and an I-P compensator, along with a filter that adjusts its attenuation ratio based on the selected loop, ensuring equal gains in specific frequency ranges to stabilize the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a PI compensator is used in the current control loop, then the response speed and cutting precision are improved, but the control stability deteriorates due to resonance in high frequency ranges
Solution Approach 1:
The patent applies dynamics by making the compensator type changeable based on operating conditions. The control device switches between PI compensator and I-P compensator depending on whether the machine tool is in locus control mode or non-locus control mode, allowing the system to adapt its characteristics dynamically to maintain both response speed and stability.
Solution Approach 2:
The patent changes the parameter of compensator type (PI vs I-P) based on control mode. By switching the compensator configuration according to operating conditions, the system optimizes the balance between response speed and control stability for different operational requirements.
2Manufacturing precision
If a PI compensator is used in the current control loop, then the cutting precision is enhanced, but the amount of overshooting increases
Solution Approach 1:
The control device dynamically switches between PI and I-P compensators based on control mode. During locus control mode, PI compensator provides high response for precision cutting. During non-locus control mode, I-P compensator reduces overshooting, demonstrating adaptive dynamic control.
Solution Approach 2:
The compensator type parameter is changed according to control mode requirements, allowing the system to optimize both precision and overshooting characteristics for different operational scenarios.
3Productivity
If the compensator is switched between PI and I-P based on control mode, then the control performance is optimized, but the gain in high frequency range increases causing resonance
Solution Approach 1:
The patent introduces a filter as an intermediary element in the current control loop. This filter attenuates the gain in high frequency ranges, thereby reducing resonance while allowing the compensator switching to maintain optimized control performance across different operating modes.
Solution Approach 2:
The filter is configured to preliminarily counteract the harmful high frequency gain increase that occurs during compensator switching. By attenuating high frequency signals in advance, the system prevents resonance from developing while maintaining the benefits of compensator optimization.
Data Source
AI summary
A control device of a servomotor includes a current control loop selecting unit configured to select a first current control loop or a second current control loop having a response speed slower than that of the first current control loop, as a current control loop for controlling a current flowing through the servomotor; a filter configured to attenuate an input or an output of the first current control loop or the second current control loop selected by the current control loop selecting unit in accordance with a set attenuation ratio in a specific frequency range; and a filter attenuation ratio setting unit configured to set, as the attenuation ratio of the filter, a first attenuation ratio when the first current control loop is selected by the current control loop selecting unit, and a second attenuation ratio smaller than the first attenuation ratio when the second current control loop is selected.