| Soft robots generally have good flexibility and passive compliance,which makes them suitable for complex application scenarios such as narrow channel detection and minimally invasive surgery.At present,many types of soft manipulators have been developed,such as pneumatic actuation,tendon-driven,as also as smart materialsactuation.Pneumatic actuation is often complicated to control,tendon-driven generally has less deformation,and smart materials are still in the development stage.Contradict to compliance,soft manipulators sometimes require greater stiffness to achieve greater load capacity,then stiffness control methods have become the research focus and difficulty in the field of soft robots.In this thesis,the tendondriven with high motion accuracy is adopted,and the body structure of the robotic arm is innovatively designed to enable the structure to achieve large deformation and scalability.This thesis studied the kinematics,statics,self-perception of self-pose,stiffness and motion control of soft manipulators.The main research content of this thesis is as follows: First,a new type of flexible joint of the soft manipulator based on a spring skeleton is designed.This joint has large space for movement,small size,light weight and high controllability.The theoretical analysis of the kinematics and workspace of the flexible joint lays the foundation for the follow-up research.The analytical statics model was established based on the Karnofsky’s theorem,and the force analysis of the spring structure was performed based on vector mechanics to obtain the analytical expression of its strain energy.The equivalent method was used to simplify the calculation process,and the equivalent axial direction of the soft arm was given,as well as the bending stiffness formula.Use the statics model to complete the optimal design of the flexible joints;secondly,connect two flexible joints in series to form a 6-DOF soft manipulator,and for the problem of insufficient stiffness,surround LMPA(Low Melting-point Alloy,low melting point alloy)around the copper spiral coil,a high-efficiency phase change structure is formed,which realizes the rapid and wide-range stiffness control of the soft manipulator.The stiffness changing ratio of the rigid-soft state is greater than 45,and the phase transition time can be as low as 15 seconds;then,the positive kinematics and Jacobian models of the two-segment soft manipulator are established,which shows the advantages in space and flexibility of the contractible joint compared to the non-contractible joint.More,based on the virtual linkage method,an analytical inverse kinematics model of a two-segment soft manipulator is proposed and simple motion planning verification is carried out.This model can meet the requirements of real-time motion control of the manipulator;finally,the principle of the highprecision flexible strain sensor measured based on inductance was proposed and applied to the feedback control of the soft manipulator-the sensor is arrayed on the periphery of the manipulator,giving the soft manipulator the ability to sense itself when it is in contact with the external environment.In this thesis,a new mechanism of soft manipulator is proposed.The kinematics,static,and the optimization design method the single-segment manipulator,the kinematics,stiffness control and motion control method of two-segment manipulator are studied. |
