A Bionic Controllable Stiffness Soft Gripper:Design,Fabrication And Control

The grasping mechanism plays an important role in improving the intelligence and enlarging the application of the service robot,since it is an essential component for the interaction between the service robot and the unstructured environment.Aiming at the requirements from the service robot,in this dissertation,a new bionic soft gripper with the capability of adaptive grasping and controllable stiffness is proposed by innovating the controllable stiffness structure.The research mainly involves the structure design and analysis,prototype fabrication,experimental validation,control system development and autonomous grasping control.Details can be concluded as follows.1.Bionic design of the controllable stiffness soft gripper.Reinforcement mechanism of pangolin scales is researched.Based on the interlock phenomenon of scales on macro and micro point,the scale structure is transformed into a manufacturable mechanical structure.Bionic design of the controllable stiffness structure is achieved.In view of nonlinear finite-element simulation results,pneumatic network actuators are improved and the end grasping force is raised.On this basis,a kind of bionic soft gripper with simple structure,controllable stiffness,strong grasping performance and convenient control is proposed.2.Fabrication and experiments of the controllable stiffness soft gripper.In consideration of the characteristics of liquid silicone,a method of soft material layered fabrication is proposed.Integrated fabrication of structures with multiple hardness is implemented.Based on experiments and simulation,the mapping relationship between the air pressure and the bending angle of the soft gripper is established.With the controllable stiffness structure,the stiffness of the soft gripper is increased by three times when actuated.The validity of structure design of the bionic controllable stiffness soft gripper is verified.3.Grasping control of the controllable stiffness soft gripper.Based on the controllable stiffness grasping,a combination of gas path on-off strategy is established and the control system integrated with gas source,gas path and sensors is developed.The autonomous grasping control strategy is proposed based on the defined grasping failure criterion.Through the autonomous grasping experiments on objects of different mass,the control parameters can be adjusted to the correct settings independently and the effectiveness of the grasping strategy is verified.which provides a new idea for solving the problem of autonomous control of soft grippers.The research results of this paper are of great significance to the analysis and design of soft grippers,which promote the application of soft grippers effectively.