Research On The Modeling And Control Of Precision Harmonic Drive System

Along with the rapid development of modern science and technology,the mechatronic servo system presents a trend towards miniaturization,lightweight,high precision and high dynamic characteristics.Harmonic,cycloid,cable drive,movable teeth and other transmissions,which have high accuracy and good dynamic characteristic,are being more and more widely used in the mechatronic servo system.The researches on their dynamics and control algorithms are highly significant for the improvement of performance of the servo system in the aspect of theory and engineering.Harmonic has many advantages,such as: large output torque,compact structure,little backlash and high transmission accuracy.It has been widely used as precision drive in Aircraft,spacecraft,robots,weapons,etc.In the field of mechatronic servo drive,it even becomes the research focus.Modeling and control of harmonic drive system are researched in this paper.The researches include: principle,dynamics modeling,model parameter identification,nonlinear dynamics characteristic compensation,model simulation,system performance prediction and so on.A model-based design method of harmonic drive system is proposed.It can provide a support for the design and application of harmonic drive.The following studies are included in this thesis:1.The principle,kinematics and dynamics of harmonic are investigated in order to grasp the relationship between harmonic dynamics characteristics and its structural parameters.Harmonic drive nonlinear dynamics characteristics include friction,stiffness and hysteresis.The simple models of the nonlinear dynamics characteristics are established and the equation relations between these parameters of the models and harmonic structural parameters are derived.By using description function method,the simple models of the nonlinear dynamics characteristics can be linearized.Based on these linearized dynamics characteristics models,a harmonic drive linear model is established,which has friction,stiffness and hysteresis.Using the linear model,the nonlinear dynamics characteristics effects of harmonic drive servo performance are studied.2.In order to establish the harmonic drive system dynamics model accurately,the actual nonlinear dynamic models of friction,stiffness and hysteresis should be established.A Stribeck model and a Lu Gre model of harmonic friction characteristic are established,the model parameters are identified,and an online rapid parameter identification method of Stribeck friction model is proposed.A Taylor series model and a finite element model of harmonic stiffness characteristic are established and the model parameters of Taylor series model are identified.The main structural parameters,which influence the low-order resonance frequency of harmonic drive system,are identified and the influence law is also identified.A Maxwell model and a Preisach model of harmonic hysteresis characteristic are established.The online discrete recursive algorithm of Preisach model is studied.The selection principles between Maxwell model and Preisach model are discussed.By integrating the three nonlinear dynamic models above,the harmonic drive simulation model can be established,and some simulation analyses of system characteristics are done.3.In order to improve the performance of harmonic drive system,the compensation method for nonlinear dynamics characteristics is studied.The model based friction feedforward compensation controller and hysteresis inverse model compensation controller are designed.Due to the uncertain value changes of the system parameters,the Backstepping adaptive compensation controller is designed.Using the harmonic drive simulation model,the simulation analyses of control performances are done.Simulation results show that the controllers designed are correctly.The selection principles between the compensation controllers are discussed.4.In order to improve the design efficiency of harmonic drive system and reduce the design costs,a model-based design method of harmonic drive system is proposed.By using the modeling and control research results above,a design process of automatic weapons station elevation servos is proposed.According to the design process,the design scheme of automatic weapons station elevation servos is proposed.By using the harmonic drive simulation model above,the performance of design scheme is simulated and analyzed.The simulation results meet the design specifications of the automatic weapons station elevation servos.Based on the design scheme,a prototype is manufactured and performance testing is done.The test results verify the correctness and effectiveness of the model-based design method.5.In order to accurately measure the nonlinear dynamics characteristics,low-order resonance frequencies,the open loop characteristics and closed loop characteristics in harmonic drive system,the performance test methods are studied.A nonlinear dynamics characteristic experimental device is designed.the nonlinear dynamics characteristics of friction,stiffness and hysteresis are measured.A structural modal and open loop characteristic experimental device is designed.the low-order resonance frequencies and the open loop amplitude frequency characteristics are measured.The test methods of lowest smooth rate,stability accuracy,positioning accuracy and maximum output torque are studied in closed loop system,and the above characteristics of automatic weapon stations elevation servo are measured.These tests obtain a lot of accurate experimental data,which can reflect the true character of the system under test.