Servomotor Control Device Rigidity Estimation and Error Correction
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Solution Overview
Problem
Existing servomotor control systems face challenges in accurately estimating the magnitude of rigidity in connection mechanisms, which affects the precision of machine tools due to elastic deformation and aging, leading to positional errors that require maintenance.
Innovation Solution
A servomotor control device with a motor control unit that includes a force estimation section, correction amount generation section, and rigidity estimation section to estimate the drive force and correct positional errors, allowing for the gradual increase of a correction constant to detect variations in rotation position information, drive force, and correction amounts, thereby estimating the magnitude of rigidity and detecting deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the connection mechanism is used to transmit drive power from servomotor to driven body, then power transmission is achieved, but elastic deformation occurs causing positional errors
Solution Approach 1:
The system uses feedback control by detecting the rotation position of the servomotor via encoder and comparing it with the actual position of the driven body. The correction amount generation section generates a correction amount based on the difference between commanded and actual positions, which is then applied to compensate for elastic deformation in the connection mechanism, thereby maintaining positioning accuracy while preserving power transmission capability.
Solution Approach 2:
The system dynamically adjusts the correction constant parameter based on the estimated rigidity of the connection mechanism. By changing this parameter according to the actual rigidity conditions, the system optimizes the correction amount to compensate for elastic deformation, thus resolving the contradiction between power transmission and positioning accuracy.
2Ease of manufacture
If the rigidity of connection mechanism is low to allow flexibility, then ease of assembly is improved, but elastic deformation increases causing larger positional errors
Solution Approach 1:
The feedback mechanism continuously monitors the actual position of the driven body and compares it with the commanded position. The correction amount generation section uses this information to generate real-time corrections that compensate for elastic deformation, allowing the system to use flexible connection mechanisms for ease of assembly while maintaining positioning accuracy through active compensation.
Solution Approach 2:
The system performs self-diagnosis by estimating the rigidity of the connection mechanism using the correction amount and detected position information. This self-assessment allows the system to automatically adjust its control parameters to compensate for the specific rigidity characteristics of the installed connection mechanism, enabling easy assembly with various components while maintaining precision.
3Manufacturing precision
If the correction constant is increased to compensate for elastic deformation, then positioning accuracy is improved, but the system becomes more sensitive to rigidity variations requiring frequent adjustments
Solution Approach 1:
The system automatically estimates the rigidity of the connection mechanism using the correction amount and detected position information during operation. This self-diagnosis function eliminates the need for manual rigidity measurements and frequent adjustment of control parameters, as the system adapts to rigidity variations autonomously, maintaining positioning accuracy without increasing operational complexity.
Solution Approach 2:
The system dynamically changes the correction constant parameter based on the estimated rigidity of the connection mechanism. By automatically adjusting this parameter according to actual rigidity conditions rather than using fixed values, the system maintains optimal positioning accuracy across different rigidity scenarios without requiring manual intervention or complex adjustment procedures.
4Reliability
If maintenance is performed frequently to prevent rigidity aging, then reliability is improved, but productivity is reduced due to downtime
Solution Approach 1:
The system performs continuous self-diagnosis by estimating the rigidity of the connection mechanism using operational data from the servomotor and position detectors. This real-time monitoring allows the system to detect rigidity aging and deterioration during normal operation, enabling condition-based maintenance that prevents unexpected failures without requiring frequent scheduled downtime, thus maintaining both reliability and productivity.
Solution Approach 2:
The system detects rigidity deterioration trends before they lead to actual positioning errors or failures. By monitoring changes in the correction amount and estimated rigidity over time, the system can predict when maintenance will be needed and schedule it proactively, preventing reliability issues while minimizing disruption to productivity through planned rather than reactive maintenance.
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
Enables precise estimation of connection mechanism rigidity, detecting deterioration, and informing maintenance needs, thereby improving machining precision and reducing errors caused by elastic deformation.
Implementation Method 1
the connection mechanism has relatively low rigidity, and elastic deformation occurs. When the connection mechanism elastically deforms, error in the amount of elastic deformation arises in the position of the table
Data Source
AI summary
A servomotor control device includes: a servomotor, detection unit, driven body, connection mechanism, and motor control unit, in which the motor control unit includes: a force estimation section that estimates a drive force acting on the driven body at a connection part between the connection mechanism and the driven body; a correction amount generation section that generates a correction amount for correcting the position command value, based on the drive force estimated and a constant for correction; and a rigidity estimation section that gradually increases the constant for correction in a state suspending generation of the position command value, and estimates a magnitude of rigidity of the connection mechanism based on the constant for correction when a variation point occurs in behavior of rotation position information of the servomotor detected, drive force estimated, or correction amount generated.