Research On Dynamics Modeling And Control Of Tandem Tensioning Constant Force System

The operational training of astronauts in the ground simulation of space weightlessness is an important part of the astronauts ground training.The astronauts' work contents walking on the surface of the planet,carrying out experimental operations on the space station and so on.The sling suspension method for astronauts' compensation of gravity can satisfies the needs of the astronauts' training for long time and wide range.In this paper,the dynamic model and the broadband fast constant force control algorithm of the tandem tensioning constant force system in astronauts' micro low-gravity simulation experiment are studied.The former is the theoretical basis of the latter.Based on the existing tandem tensioning constant torque mechanism of the laboratory,a tandem tensioning constant force system with excellent adjustable performance and higher force precision is developed.In this process,the existing tandem tensioning constant force mechanism is improved,and its adjustment performance of set force and constant force curve are improved.Electrical construction of real-time control system based on Simulink Real-time module is carried out.The software platform of the system is designed.The hardware configuration program,the logic control program and the working mode program are compiled.The hardware and software platform of the tandem tensioning constant force system is determined.The dynamic model of the differential equation form of the tandem tensioning constant force system is established based on the Newton's second law.The conclusion that the system is a second order oscillation system in the motor hysteresis condition is obtained by dynamic characteristics analysis.At the same time,the influence of the equivalent stiffness of the mechanism on the system characteristics is analyzed.Simulation analysis of the model error of the tandem tensioning constant force system using ADAMS software is carried out.The influence of non-linear factors such as coulomb friction on the force output of the system is simulated.The effect of the simplified error of the moment of inertia of compression spring assembly that occurs when the system is excited at high frequencies is found.The conclusion that these processes are less effective and dynamic modeling is reasonable at low frequencies is drawn.Which provides a theoretical basis for the study of control algorithms.Based on the dynamic model of the tandem tensioning constant force system,the control algorithm of the system is studied,and a force closed-loop control strategy based on the velocity inner loop of the driver is proposed.The incomplete differential PID is selected as the controller of the system.Based on the sweep method,the identification of the transfer function of controlled object of the system is carried out.And on this basis,the system bandwidth design is carried out.The parameters of the PID controller and the hysteresis correction are determined.Finally,the filter suppression based on the notch filter is performed at the resonant frequency of the system.Aiming at the requirement of dynamic performance test of the tandem tensioning constant force system,a scheme of dynamic characteristic test of the system is proposed by using constant velocity and acceleration excitation,sinusoidal excitatioon and floating load excitation.The constant velocity and acceleration experiments indicate that the system is more sensitive to the speed of this movement,the system can achieve 181mm/s mobile capacity in the condition that the maximum force error is less than 20 N.Through The sinusoidal excitation experiment illustrates that the system can withstand the sinusoidal excitation of 2Hz and amplitude below 17.3mm/s under the conditation that the maximum force error is less than 20 N.The floating load experiment demonstrates that the system can achieve the control of the floating load.It has the ability to respond to 0.1N perturbations,which provides the basis for the future research of the constant force control system of floating load.