Research On A Smart Flexible Bending Pneumatic Artificial Muscle

In recent years,with the growing of society and economy,driven by the development of computer science,automation technology,robotic morphology and other scientific fields,the robot is playing an increasingly important role in human society.At the sam e time,due to the unique advantages of flexible actuators in bionics and robotics,in recent years,more and more attention has been paid to its research in worldwide.Conventionally,the traditional drive mechanism relies on rigid gears,hinges,connecti ng rods,cams and other mechanical structures to achieve complex motions,while the flexible actuator or driving structure realizes the complicated and flexible movement with the dexterous deformation of its own structure under the drive of excitation source.The flexible pneumatic artificial muscle studied in this work is a kind of flexible actuator using fluid pressure as the excitation source.Flexible actuators and driving structures own the incomparable flexibility due to the nature of their soft structures,comparing with the traditional driving mechanisms.However,on the other hand,the soft feature generates the strong coupling,nonlinearity,time-variation effect in the structures and control systems,which makes static and dynamic analysis and kinematic control of flexible actuator more difficult.In this paper,a smart flexible bending pneumatic actuator was proposed,developed and analyzed.The actuator has a simple structure and output stability and is composed of the elastic tube,braided tube,embedded elastic frame,end fittings and other structures.Each end of the elastic tube,braid tube and the elastic frame was fixed together with the connectors.When the elastic tube are filled with compressed gas as elastic air chamber,the actuator ten ds to contract or elongate,but due to the restraint of the elastic frame,it generates a bending motion to one side.A humanoid flexible hand based on the actuator proposed in this paper was built and tested.The soft humanoid hand be capable of adapting to various objects of different shapes and sizes,which reflects the versatility,flexibility and adaptability of the flexible pneumatic actuator.In the tests of the flexible pneumatic actuator,it was found that there is hysteresis and non-linear characteristics of the relations among the output force/moment,the deformation of the actuator and the working pressure.Based on the test results,the Mooney-Rivlin hyperelastic material model is involved to establish the force balance model and the energy model based on the principles of force balance and work-energy respectively.Considering the deadband of pressure and the pre-strain in the active state corrections terms were involved into the models to meet the actual working situations.The modified mod el agrees well with the experimental results and can effectively reflect the nonlinear static characteristics of the actuator.An intelligent design of the actuator was also implemented in this paper to realize the self-sensing function,which is the significant point of building the feedback control of flexible actuators.The test results show that the feedback control system not only be able to achieve the motion control and the output force control,but also improve the driver's resistance to damage and anti-jamming capability.In this paper,a reliable and practical static mathematical model was established for the proposed flexible bending pneumatic actuator,which would provide a theoretical reference and basis for the application of this flexible actu ator.The design of self-sensing drivers and intelligent control systems provides a promising solution for the control of flexible actuators and driving structures.It is believed that flexible actuators and driving structures will have more extensive application area and higher application value in the field of soft robot,wearable auxiliary equipment and industrial and agricultural production,medical service,rescue task and so on.