Study On Compliant Force Control Of Pneumatic Hydraulic Combination Control System

Pneumatic hydraulic combination control (PHCC) servo system is a new-style composite control system, in which the liquid medium with low compressibility and high viscosity is led into a normal pneumatic servo system and controlled in closed-loop simultaneously. The system compounds the characteristic of"flexibility"in pneumatic system and"rigidity"in hydraulic system, and possesses the excellence of speediness and rigidity, which is good to compliant control of robot. So the paper research compliant control of PHCC servo system.After synthesizing numerous related literatures and reference materials at home and abroad, the research and development situation of pneumatic servo system in recent years is summed up. Then the development situation of compliant control is analyzed. The common control strategy and the key problem in compliant control are detailed.Compared with the other pneumatic servo system, the PWM electricity-pneumatic on/off servo system is applied broadly for its excellence of more fit to continuous control and low cost. But the serious nonlinearity and hard modeling prevented its development. So applied nonlinear PWM average method, the paper changes the model from disperse multi-input to the single-input, which advantaged research of the system.The unionize control of position and force can be realized by impedance control, which is one of main compliant force control theory. The paper introduces the method of impedance control, and applied the force-based impedance control and position-based impedance control respectively to PHCC servo system. Then analysis control performance and impedance parameter by the simulation of two kind impedance. For the better performance and easy application to compliant control, the paper emphases the research on the position-base impedance control.The performance of inner position controller influences the performance of compliant control. To improve the performance of system, the paper applied nonlinear control theory to research the state equation and put forward the variable structure control strategy. Based on the rank of system, which judge by define of relative rank, the three rank variable structure controller is designed. Then computer simulation is carried out. But the performance is not ideal because of the coupling of complex parameters. So the work of lower rank of sliding surface is developed and the two rank variable structure controller is designed. Then computer simulation is carried out, too. Simulation results indicate the speediness and tracking ability of the controller.In the process of compliant force control, the chose of control strategy is affected by the knowability of environment parameters and influent the performance of control. The paper reduces the situation of environment to three case: environment knowable, environment non-knowable and time invariant, environment non-knowable and time variant. Then the control method of fuzzy impedance control, direct adaptive control, and indirect adaptive control is designed respectively to the three situations, which realized the compliant force control in differ environment parameter situations.Finally, the pneumatic-hydraulic compliant force control system is build. the computer control software and the whole experiment scheme is put forward. The simulation and experiment results of system proved the designed experiment system and control software in this paper are successful, and the theories and views set forth are right, and the controller designed are reasonable and feasible.The research of paper established foundation of further application to compliant force control of pneumatic industry robots.