| Micro-nano scale manufacturing technology is the key to modern high-performance weapons and equipment,integrated circuit chips,high-precision aspheric lenses and other high-end defense,information and medical products,and directly affects China’s national defense strength and industrial manufacturing level.How to realize the micro-nano-level feed is the main bottleneck of ultra-precision machining technology.At present,unipolar drive and macro-micro bipolar drive are often used,but there are disadvantages of nonlinear hysteresis,creep,low rigidity,difficult control,slow frequency response and high cost.The dual-drive micro-feed system based on the differential composite principle proposed by our research group can fundamentally solve the crawling phenomenon,but the system is still inevitably disturbed by friction,vibration,and external nonlinear disturbances.Therefore,this paper further studies the characteristics and control algorithms of the system.The main research contents are as follows:(1)The hardware structure and software platform of the differential dual-drive micro-feed system are built,and the motion principle and motion combination of the system are analyzed.According to the dynamic characteristics of the system,two control models of the differential dual-drive micro-feed system are established.It includes rigid body model and flexible body model.The lumped mass method is used to establish the rigid body dynamics model,and the forgetting factor least square method is used to identify the parameters of the rigid body model system.Considering the flexible mode,the flexible body model of the system is established,which can reflect the first-order torsional coupling vibration mode of the system and accurately predict the vibration of the system.On the basis of the mathematical model,the frequency response and fitting transfer function of the system obtained by the frequency sweep test are used to identify the parameters of the flexible body model by the undetermined coefficient method.(2)Taking the rigid body model as the control object,based on the LuGre friction model,considering the influence of factors such as the motion synthesis of the differential dual-drive micro-feed system on the friction state such as the temple hair offset of the LuGre friction model,and considering the two cases of uniform change and uneven change of friction,a single friction change adaptive coefficient and multiple friction change adaptive coefficients are introduced to improve the friction model.A nonlinear observer is designed to estimate the internal state of the friction model.On this basis,an adaptive friction compensation controller is designed,and the uncertain parameters in the system are estimated by the parameter adaptive law.The effectiveness of the method to improve the accuracy of the control system is verified by experimental comparison,and the influence of introducing single adaptive coefficient and multiple adaptive coefficients on the control performance of the system is analyzed.(3)Taking the flexible body model as the control object,the nonlinear friction,parameter uncertainty and external disturbance are taken as the external total disturbance of the system.The generalized extended state observer is designed to estimate the matched disturbance and the mismatched disturbance.It is proved that the observation error of the observer is bounded and can effectively observe the system state variables such as external disturbance.Based on the observer,an integral sliding mode controller is designed.It is proved by Lyapunov function that the controller is asymptotically stable and the tracking error can converge to zero after reaching the sliding surface.According to the principle of quadratic optimal control,the optimal gain feedback gain matrix is determined,and the cost function is introduced to simplify the tuning process of system control parameters.The simulation and experimental results show that the control algorithm can effectively improve the tracking accuracy of the servo system and has good robustness.(4)The error sources and error classification of the servo motion platform are analyzed.The specific characteristics of the geometric error,thermal error and control system error of the dual-drive system are analyzed.The geometric error measurement method and compensation strategy are given.And a comprehensive error compensation strategy is proposed.The effectiveness of the comprehensive compensation of geometric error and nonlinear force error is verified by experiments. |
