Design And Analysis Methods For Modular Cable-Driven Manipulators With Co-Shared Driving Cables

Modular cable-driven manipulators have simple,light weight,high dexterity,high flexibility and intrinsic safe structures as well as reconfigurable configurations.It is an important development direction of service robots for rehabilitation,medical treatment and taking care of the elderly and the disabled people.However,in traditional modular cable-driven manipulators,each joint modules are usually independent motion control units driven by multiple cables in parallel,resulting in excessive redundancy in the number of driving cables of the modular cable-driven manipulator,which not only increases the complexity of the system but also increases the manufacturing cost,but also limit the application of the modular cable-driven manipulators.To reduce the number of driving cables,this thesis systematically studies the configuration design,kinematics and dynamics modeling,tension analysis,stiffness analysis,trajectory planning and other key scientific issues of a modular cable-driven manipulator based on co-shared driving cables.The main work and contributions are as follows:1.A cable routing method using a co-shared driving cable is proposed,which uses minimal number of cables and effectively reduces the number of driving cables without affecting the working space.With the property that the universal joint kinematic chain can perform a self-rotation motion,a base rotating joint and an end rotating joint rotating joint are added to the manipulator,as such the manipulator can perform a selfrotation motion without changing the pose of the end and the spatial positions of each joint module,which not only improves the dexterity of the manipulator,but also creates conditions for optimizing the distribution of the cable tensions.2.The kinematics modeling method of the modular cable-driven manipulator with co-shared cables is studied,the forward kinematics,inverse kinematics,velocity analysis and acceleration analysis algorithms of the joint module and the manipulator are proposed,which provides a tool for motion control,dynamic modeling and performance analysis.A self-rotation motion analysis method based on local product of exponential algorithm for the manipulator is proposed to provide a mathematic tool for the tension optimization via self-rotation.3.The statics is studied where the cable tension analysis method is proposed which decomposes the cable tensions into the load-carrying tension and the internal tension,and revealed the tension magnifying phenomenon of the manipulator at specific configurations.An optimization algorithm is proposed to reduce the cable tension through the self-rotation of the manipulator,which significantly reduces the cable tensions.4.The stiffness analysis method of the modular cable-driven manipulators with co-shared cables is proposed.The stiffness of the joint module and the stiffness of the manipulator under different external loads are analyzed.An algorithm to compute the stiffness matrix of the end based on the principle of minimum potential energy is proposed.With the application of the driving unit stiffness matrix,the system potential energy can be represented as a standard form of a quadratic programming problem,which improves the computational efficiency.5.To improve the performance of the manipulator,the trajectory planning problem of the modular cable-driven manipulator for cable tension minimization is studied,and a trajectory planning method aiming at reducing the peak value of the average loadcarrying tension is proposed.By an alternate iteration optimization algorithm,the computational complexity is reduced,and the computational efficiency of the trajectory planning algorithm is improved.6.To verify the effectiveness of the proposed methods,a 5-joint modular cabledriven manipulator prototype is developed,and the performance measurement experiment,self-rotation experiment and the experiment to verify the trajectory optimization algorithm of the manipulator are carried out.The experimental results verified the effectiveness of the theoretical analysis algorithm.In summary,this thesis proposes a new type of modular cable-driven manipulator configuration design that reduces the number of cables.Systematically studies of its performance analysis,optimal design and trajectory planning have been proposed.The correctness and the effectiveness of the method are verified by experiments.The research work contributes to the wide application of the modular cable-driven manipulators.