Spindle Thermal Error Compensation Under Cooling Disturbance
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Solution Overview
Problem
Existing spindle thermal error compensation methods are not robust enough to handle disturbances from the cooling system, leading to reduced accuracy and efficiency in machining processes.
Innovation Solution
A spindle thermal error compensation method is developed, involving spindle model coefficient identification using multi-state speed variables, correlation analysis to determine significant temperature measurement points, and a nonlinear quadratic programming algorithm to establish a thermal error model insensitive to cooling system disturbances, with compensation values input via OPC UA communication protocol to the numerical control system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensor mode thermal error compensation is used, then prediction robustness to rotational speed fluctuations is improved, but compensation accuracy deteriorates when cooling system disturbance occurs
Solution Approach 1:
The patent implements feedback by continuously monitoring spindle temperature through sensors and using this information to dynamically adjust thermal error compensation. The temperature feedback loop allows the system to detect cooling system disturbances and adapt the compensation model in real-time, maintaining accuracy despite disturbances while preserving robustness to speed fluctuations.
Solution Approach 2:
The patent changes the parameter set used for thermal error prediction by incorporating multiple temperature sensor readings at different spindle locations and operating conditions. By using temperature parameters alongside rotational speed, the model can distinguish between normal speed-induced thermal variations and abnormal cooling system disturbances, thereby maintaining both robustness and accuracy.
2Manufacturing precision
If machine tool operates for certain period after turning on, then thermal error influence on machining accuracy is reduced, but energy waste increases and processing efficiency decreases
Solution Approach 1:
The patent applies preliminary action by pre-characterizing the thermal error behavior of the spindle across different operating conditions during the coefficient identification phase. This pre-established thermal model allows the system to immediately compensate for thermal errors from the start of operation, eliminating the need for warm-up periods and enabling immediate high-precision machining.
Solution Approach 2:
The patent replaces the mechanical thermal equilibrium approach (relying on natural cooling and stabilization) with an active computational compensation system. By using thermal error prediction models and real-time temperature monitoring, the system substitutes passive thermal management with active error correction, achieving high precision without requiring extended warm-up periods.
3Manufacturing precision
If thermal insulation materials and thermal symmetrical structural design are used, then thermal error prevention is improved, but cost increases
Solution Approach 1:
The patent applies self-service by enabling the numerical control system to perform thermal error compensation using its own existing temperature sensors and computational resources. Rather than requiring external specialized equipment or complex structural modifications, the system uses its built-in capabilities to measure, model, and compensate thermal errors, achieving precision improvement without significant additional cost or complexity.
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 method enhances the robustness and accuracy of thermal error compensation, reducing energy waste and improving machining precision by accounting for real-world operational conditions and eliminating the need for constant temperature environments.
Implementation Method 1
temperature sensors need to be placed at critical locations, to make thermal error prediction based on temperature information
Implementation Method 2
many internally located sources (such as bearings and motors) generate heat. Such heat is transferred to the various parts of the machine, causing thermal deformations, which subsequently create thermal errors
Data Source
AI summary
A spindle thermal error compensation method which is insensitive to the disturbance of the cooling system is provided, belonging to the technical field of error compensation in numerical control machine tools. First, the spindle model coefficient identification test, based on multi-state speed variable, is performed; after which, based on the correlation analysis between temperature and thermal error, the temperature measurement point, significantly correlated with the axial thermal error of the spindle, is determined. Next, a spindle thermal error model is established, which is insensitive to the cooling system disturbance. In addition, the coefficients in the model are identified under constraint condition, according to the nonlinear quadratic programming algorithm. Finally, based on the OPC UA communication protocol, the compensation value, as calculated by the model, is input to the numerical control system, in order to realize the compensation of the spindle thermal error.