| With the continuous progress of automation control,manufacturing technology,and robot morphology,the applications of robots have gradually extended from industrial production,transportation,and aerospace to new fields,such as medical health and life services.On the other hand,the complexity and high frequency of robot-human interaction put forward higher requirements on the flexibility,safety,and adaptability of robots.The traditional robots are mainly composed of rigid modules connected by a variety of motion pairs.The rigid structures make them less adaptable to the environment and difficult to guarantee the safety of human-machine interaction,though they possess high motion accuracy.With the development of bionics,3D printing technology,and intelligent materials,the concept of soft robots has been proposed,which provides new ideas for solving the problems of poor adaptability and low safety of traditional rigid robots.Soft actuators are the basic and key technology of soft robots.Their continuous development is of great significance to the application of soft robots.In recent years,soft actuators driven by various methods have been developed.Among them,soft pneumatic actuators are widely used in soft robots due to their high output force,large displacement,and fast response speed.However,the existing soft pneumatic actuators also face challenges such as single motion mode,insufficient reliability and low intelligence.Aiming at the deficiencies of soft pneumatic actuators,this paper is devoted to the design and fabrication of new high-performance soft pneumatic actuators to provide more candidates for soft robots.At the same time,in order to further expand the practical functions and applications of robots,it is necessary to solve the common problems such as theoretical modeling and sensing technology of soft actuators.The main researches of this paper are as follows:(1)First,a new type of pneumatic torsional actuator with small actuating pressure and large torsional angle is designed based on the cooperative and reversible collapse behavior of elastomers.And the finite element model of the torsional actuator is established by the simulation software ABAQUS.The experimental results show that the finite element model can accurately simulate the deformation of the torsional actuator.Based on the experiment and finite element model,the effects of actuating pressures and structural parameters on the torsion performance of the torsional actuator are studied.The research results show that the torsion angle and output torque of the actuator will not change significantly as the actuating pressure exceeds-20 k Pa.The increasing height and helical angle of the torsional actuator is beneficial to improving the torsion angle and output torque.In addition,an approximate model of the structural parameters and the torsional performance is established to realize the rapid design of the torsional actuator.The accuracy of the approximate model is validated by comparing the finite element results.Finally,a soft manipulator and soft gripper with a torsional degree of freedom are designed and fabricated in order to demonstrate the application prospect of the torsional actuator.The experiments show that the torsional actuator is beneficial to increasing the flexibility of the manipulator and gripper.(2)Secondly,a multi-degree of freedom soft pneumatic actuator is designed by the inspiration of earthworms and leeches,which can bend in multiple directions and stretch in its length direction.To analyze the performance of the pneumatic actuator,a finite element model and static theory model of the actuator are established,respectively.The experimental results,finite element results,and theoretical results are basically consistent when different pressures are applied to the actuator,which validates the finite element model and the static theory model.Subsequently,the effects of actuating pressures and structural parameters on the deformation performance of the actuator are revealed.As the actuating pressure is 100 k Pa,the maximum bending angle,maximum contact force,and maximum elongation ratio of the actuator are 151°,0.643 N,and 25.57%,respectively.The analysis of structural parameters shows that the height difference of cosine wave peak to trough and the thickness of the intermediate isolation layer can be further optimized.Therefore,the surrogate model technique and the multi-objective optimization method are used to optimize the structural parameters.The optimized structural parameters can further enhance the maximum bending angle and maximum contact force of the actuator.Finally,two soft grippers are fabricated using the actuators,which demonstrates the flexibility and adaptability of the actuators via different grasping experiments.(3)Thirdly,a soft pneumatic planar actuator that can deform in three-dimensional space is designed and fabricated.To study the deformation characteristics of the planar actuator,a statics theory model is established based on the principle of minimum potential energy.The theoretical results of the deformation of the planar actuator are verified by the experimental results and simulation results,thereby verifying the accuracy of the established theory model.Furthermore,the effects of actuating pressure,structural parameters,and silicone material on the actuator deformation are studied according to the established theory model,which provide a reference for the design of the planar actuator.Finally,inspired by the Venus flytrap biological gripper,a biomimetic soft pneumatic planar gripper is developed using the planar actuators.The experimental results show that the maximum grasping force and the pull-off force of the gripper are 0.713 N and 8.150 N,respectively,when the actuating pressure is 60 k Pa.And the passive deformation of the soft plane makes the gripper possesses high adaptability,reliability,and fault tolerance in the grasping process.(4)Finally,a self-sensing soft pneumatic actuator is proposed based on magnetically responsive smart materials and soft pneumatic structures.The effect of different structural parameters on the induced voltage of the magnetic composite structure is studied experimentally.The results show that the increase of the magnetic powder content,number of winding turns,and width and thickness of the magnetic composite structure can improve the induced voltage.Based on the results,the final parameters of the magnetic composite structure in the actuator are determined.Furthermore,the mechanical deformation and feedback voltage of the actuator are analyzed under different actuating pressures.The experimental results demonstrate that the magnetic flux change is approximately linear with the bending angle of the actuator.And the mathematical relationship between the deformation and feedback voltage of the actuator is established by the fitting method.Then,the effect of the magnetic composite structure on the mechanical properties of the actuator is investigated.Compared with the actuator without embedding magnetic composite structure,the maximum bending angle of the self-sensing soft pneumatic actuator is reduced by 7.15%,while the maximum contact force is increased by 56.68%.Finally,an intelligent bionic hand is fabricated using the self-sensing soft pneumatic actuators.And the feedback signals of the bionic hand under different gestures are demonstrated.Therefore,the self-sensing soft pneumatic actuators have laid the foundation for the research on intelligent soft robots. |
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