Design And Control Of Self-sensing Actuator Based On Super-coiled Nylon Polymer

Super-coiled nylon polymer(SCNP)is a kind of smart material which can be made by fishing line or sewing thread.It can generate considerable force and stroke by heating.Compared with the traditional smart material,SCNP has the advantages of low price,convenient production and simple driving conditions.Excellent actuation effect and low price make it have very bright application prospects in the field of robot actuator.However,the traditional SCNP usually has problems such as small output force,difficult heating and lack of proper temperature sensing method.These problems greatly affect the performance of SCNP actuator and hinder its wide application.For the problems of small output force and difficult heating,after analyzing the structure and actuating mechanism of SCNP and comparing many common heating methods,the fabricating process of SCNP made of nylon 66 multifilament material and the reasonable heating way are proposed.The SCNP made by this method can produce greater output force without sacrificing the output stroke,which makes it possible to be used in large load.The premise of the control of SCNP is real-time accurate temperature feedback.In this paper,an improved self-sensing temperature measurement method with real-time measurement error less than 5% is proposed,and the temperature measurement method is further combined with the SCNP fabricating process to complete the SCNP actuator.Besides,the temperature closed-loop control of SCNP actuator is realized by establishing the thermoelectric model,designing the control system and simulating the control strategy.In order to realize the position closed-loop control of the SCNP actuator,this paper establishes the experimental platform,designs the experimental processes to obtains several parameters that affect the output force of the SCNP actuator,realizes the construction of SCNP actuator thermomechanical model,and uses this model to carry out the simulation position control.Finally,based on the improved self-sensing temperature measurement method,a nested closed-loop control strategy and hardware control system are designed to realize the double closedloop control of temperature and position of SCNP actuator.In order to test the actual performance of the SCNP actuator and explore its application prospects,this paper designs a soft gripper based on the SCNP actuator,and achieves accurate control of the bending posture by hardware control system and nested closed-loop control strategy.In addition,through experiments verify the adaptability to different shapes objects and the load capacity of the gripper,at the same time verify the practical application ability of the SCNP actuator.