| Servo loading test system,also known as load simulator or torque servo system,is mostly used to simulate the load moment acted on servo system in the actual working conditions.To realize the control and mechanical performance test of a series of servo valve,a set of dual-channel Electric Linear Loading Test System(ELLTS)was developed,and the system structure,hardware architecture and control method were optimized.Firstly,based on the mechanism modeling method,the system overall coupling model considering the movement characteristics of bearing unit is established.The model uncertainty analysis of loading unit and the bearing unit is carried out.The influences of transmission stiffness,friction damping and moment of inertia on the characteristics of forward and disturbance channels are studied.The results show that the effect of servo stiffness on the suppression of excess force and the loading accuracy should be considered synthetically.Secondly,the closed-loop stability of the system is analyzed,and the local feedback and phase lag correction are used to improve the stability.In order to suppress the surplus force,a nominal model disturbance-observer(DOB)with low-pass filter is used.A hybrid control strategy based on current inner loop,position inner loop and force outer loop is proposed.The fuzzy adaptive PID control is applied to the force outer loop,and the effectiveness of control strategy is verified by simulation.In view of the hardware architecture based on PXI bus,the overall architecture and principle structure of the software system are optimized.The UI Main program of host computer,the RT Main program of the realtime controller and the communication program of the above devices are designed.For a type of bearing unit,the control performance test and position servo unit output force test are carried out.The system dynamic debugging results show that the designed system meets the requirements of dynamic and static index. |
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