Research On Multi-degree-of-freedom Pneumatic Elephant Trunk-like Soft Robo

The elephant trunk is a continuum structure composed of muscles,which can perform complex and flexible motions such as rotation,extension,and torsion.It has important significance and value for the research of bionics and soft robots.In this paper,based on the motion characteristics of the elephant trunk,we designed and constructed a modular bionic elephant trunk robot driven by pleated actuators.The main contents of this paper include:(1)Structural design: We analyzed the motion mechanism and degree of freedom distribution of the elephant trunk,and simplified it into several modules,each with four degrees of freedom: rotation in two directions,extension in the axial direction,and torsion in the circumferential direction.We designed the structure and driving mode of the bionic elephant trunk robot,and used pleated actuators as the basic execution units to achieve unidirectional extension motion,Thus,the four-degree-of-freedom motion of a single module is realized,meeting the needs of continuum robots.(2)Model establishment: We established the kinematic and static models of the bionic elephant trunk robot,and used the Yeoh hyperelastic model to describe the deformation characteristics of the pleated actuators.We derived the kinematic and static equations of a single pleated actuator,a single module,and the whole robot,and verified the correctness and feasibility of the model through finite element simulation.(3)Control system: We designed the control system of the bionic elephant trunk robot,using Dallin pure lag algorithm and improved single neuron adaptive PID control algorithm as control strategies.The Dallin pure lag algorithm can eliminate the lag effects caused by hyperelastic materials and control delay,obtain the delay values under different situations through response experiments,avoid training the lag model,and improve control efficiency.The single neuron adaptive PID control algorithm can automatically adjust PID parameters,increasing control accuracy and robustness.We added incomplete differential terms in the control system to enhance anti-interference ability,suitable for soft robot control requirements.The hardware of the robot is introduced,and the control strategy is introduced.(4)Experimental verification: We introduced various experiments conducted on the built experimental platform for the bionic elephant trunk robot.In addition to verifying four degrees of freedom motion,we also tested motion characteristics under different environments,such as underwater sealing,temperature and atmospheric pressure effects on motion,etc.,providing data support for establishing more accurate models and controls for bionics elephant trunk robots.The experimental results show that bionic elephant trunk robots can achieve similar motion capabilities and flexibility to elephant trunks,adapt to different environmental conditions,and demonstrate good application prospects.We also performed error analysis on experimental results,discussed error sources and influencing factors,providing guidance for further improving bionic elephant trunk robot performance。Finally,we summarize our work and propose future research directions.