Research On Loading Control Strategy For Machine Tool Spindle Reliability Test

CNC machine tools are known as "working machines" in the equipment manufacturing industry,and their reliability directly affects the level of the manufacturing industry.As the core functional component of CNC machine tools,the reliability of the spindle is of great significance for ensuring the reliability of the entire machine tool.Reliability test data is a prerequisite for reliability research.In order to provide more data support for spindle reliability research and quickly trigger various faults of the spindle under actual working conditions,it is necessary to build functional component test benches based on different test requirements,and design control strategies to enable the loader to simulate the actual working conditions of the spindle with high fidelity based on the load spectrum.In terms of control strategies,previous studies have typically established observers for the parameterized model of a single actuator to complete the design of control strategies.However,such methods only have good control effects when the actuator is determined and the operating conditions are ideal,but their universality is poor.After changes occur in the system,it is necessary to redesign the controller parameters,which is difficult to adapt to factors such as loader uncertainty caused by different loading requirements and actuator uncertainty caused by spindle replacement;In addition,the complex load simulation environment,output coupling disturbances,model mismatch,and other factors seriously affect the control accuracy.In order to explore control strategies suitable for the specific environment of reliability loading tests,based on predictive control strategies based on fast identification models,this paper optimizes predictive control strategies for output coupling disturbances,controller universality,robustness,and other issues that exist in the loading process,and proposes an improved predictive control strategy suitable for reliability loading environments,The control strategy is applied to reliability test benches based on different loaders.The main research work of this article is as follows:(1)A basic predictive control strategy based on fast identification model loading system is established.First,considering that the stiffness of the loading element and the bearing inside the spindle are important parameters for system dynamics modeling,a local quasi dynamic model of the ball bearing spindle loading element based on Hertz contact theory is established,and a bearing simulation environment based on the Levenberg-Marquardt equation solver is established.The influence of axial and radial forces on the spindle stiffness is analyzed;Then,three typical loader structures and working principles based on different actuators are summarized,and factors affecting the control accuracy of the system are summarized in combination with bearing characteristics.A predictive control system has been established,and a hardware implementation platform based on arbitrary loaders has been built based on NI-Compact Rio.(2)Aiming at the problem of coupled disturbances at the output during loading,the system observer and predictive output equations are improved,and a predictive control strategy based on extended disturbance observer is proposed.Firstly,a disturbance observer based on a controlled autoregressive moving average model is established.Secondly,the disturbance estimation is used as a limiting condition for the output optimization equation and a disturbance input incremental output equation is established.This effectively solves the coupling disturbance problem caused by the single form of traditional predictive control strategies.Simulation experiments and application experiments to suppress the excess force of the electro-hydraulic servo loading system verify the effectiveness of this method.Further,this paper unifies the controller form through model transformation to facilitate subsequent improvements to the predictive controller.(3)The tuning method of predictive controller coefficients is optimized.Considering that in predictive controllers,predictive weighting coefficients are controller parameters that require manual design and tuning and have a significant impact on system tracking performance and stability,the impact of predictive weighting parameters on control system performance is first analyzed through simulation,and a nonlinear control strategy based on time-varying predictive weighting coefficients is proposed,and a method for determining the coefficient stability interval is proposed,This provides a theoretical basis for online debugging of predictive weighting parameters,solves the problem of universality of predictive control strategies,and enables them to be applied in different systems.Secondly,considering the pulse disturbance problem in the actual loading system,a fuzzy parameter adjuster is designed to automatically adjust the predictive weighting coefficients online.The effectiveness of this method is verified by the loading application experiment of an electro-hydraulic servo system.(4)Aiming at the robustness of the loading system,the control law and feedback correction law are optimized.Firstly,a sliding mode equation is introduced into the controller to solve the problems of parameter perturbation and model mismatch in the loading process.Secondly,a more flexible feedback correction law based on a nonlinear Luenberger observer is established,which improves the error correction ability of the system.Furthermore,the stability of the system is proved through the Schur stability criterion of interval matrices and the conceptual analysis of asymptotic stability.Simulation experiments and application experiments of a piezoelectric actuator based spindle force loading device for machining centers and a spindle rotation accuracy micro displacement compensation device verify the effectiveness of the method.(5)Based on the previous optimization of predictive control strategies,a comprehensive control system design process based on arbitrary execution loading was developed.loading tests were conducted on a three-phase asynchronous motorized spindle based counter drag test platform,an electro-hydraulic servo system based force loading test platform,and a piezoelectric actuator based force loading test platform to verify the effectiveness and practicality of the overall control strategy.