Research On Motion-decoupling Methods And Robust Control Of Cable-driven Manipulator System

Compared with traditional industrial manipulators,the cable-driven manipulators can provide lighter moving inertial,higher load-to-weight ratio and safer interactions with human;therefore,they have been widely used in medical care,flexible manufacture et al.On the other hand,the adoption of cable-driven technique also brings about more complex system dynamics and lower stiffness,which will lead to more challenges for the high performance tracking control.This thesis focuses on the design and robust control of cable-driven manipulator system and can be divided into the following parts,including the research of motion-decoupling module and manipulator design,kinematics and dynamics,robust control algorithms.The motion-decoupling module and design of cable-driven manipulator are studied.The application of cable-driven technique can effectively reduce the moving inertial and increase the interaction safety,nevertheless,it will also bring about inevitable kinematics coupling problem.First,the coupling relationship of the cable-driven manipulator is analyzed,and a novel motion-decoupling module is developed which successfully realizes the effective decoupling of the cable-driven manipulator.Then,a two degrees-of-freedom decoupling comprehensive experimental platform is developed;corresponding experiments demonstrate the effectiveness of the developed motion-decoupling module.More motion-decoupling modules will be required when the cable-driven manipulators have more joints;meanwhile,the adoption of designed motion-decoupling module will increase the volume and weight and torque loss of the cable-driven manipulator,which will bring about more complex system structure.To solve the above-mentioned problems,we develop a cable-driven 4-Dof manipulator named “Polaris-I” which uses algorithm to solve the coupling issue.The kinematic coupling mechanism of the cable-driven manipulator is further studied and the coupling matrix between joint space and drive space is deduced,meanwhile the mapping relationship of the drive space and joint space and Cartesian space is established for the cable-driven manipulators.The kinematic model of “Polaris-I” is established,while the Jacobian matrix is also given.Afterwards,the dynamics modeling problem of cable-driven manipulator is studied,and the integrated dynamic model is obtained with three steps.The parameter identification problem of serial joint robot with cable feature is studied;and the established dynamic model and proposed parameter identification method are demonstrated through simulations and experiments.For the trajectory tracking control problem of cable-driven manipulators under complex lumped disturbances including complex dynamic couplings and large parameter uncertainties and time-varying unknown external disturbance,a sliding mode(SM)control scheme based on time-delay estimation(TDE)technique is proposed.The proposed control scheme mainly contains two parts,i.e.,TDE part and SM part.The TDE part uses intentionally time-delayed value of the system's signals to estimate its own current lumped dynamics,and then ensures a fascinating model-free control structure.Meanwhile,the SM part is used to guarantee high control performance under the complex lumped disturbance.Finally,the effectiveness of the proposed control scheme is verified through experiments.Based on the proposed TDE-based SM control scheme,the author propose a novel TDE-based fractional-order nonsingular terminal SM(FONTSM)control scheme.The proposed control scheme is model-free,simple and easy to use in practical applications.Meanwhile,the proposed control scheme can also ensure good dynamic response and stable control accuracy thanks to the adoption of FONTSM error dynamics.Finally,the effectiveness and superiorities of the proposed control scheme over the existing control schemes are demonstrated through comparative simulations and experiments.To further improve the comprehensive control performance,dynamic response and stable control accuracy,a novel TDE-based adaptive FONTSM(AFONTSM)control scheme is proposed based on the proposed TDE-based FONTSM control scheme.To effectively handle the time-varying lumped disturbance,the proposed control scheme combines TDE technique,FONTSM error dynamics and a novel proposed adaptive reaching law;and then the control performance of cable-driven manipulators is effectively improved.Finally,the effectiveness and advantages of the proposed control scheme over the existing ones are verified by comparative simulations and experiments.Finally,the research work and contributions of this thesis are concluded,while some discussions about the drawbacks and further research directions of this thesis are provided.