Mechanism Synthesis,dynamics And Motion Control Of The End-effector Of Two-class Cable-driven Parallel Robots Containing Elastic Cables

In the past 2 decades,the cable-driven parallel robot has some satisfying characteristics and has been widely studied and applied.However the existence of the nontrivival coupling among dynamics of elastic cables,of the end-effectors as well as as of the actuators,the difficulty of tackling the issue of motion control of the end-effector based on mechanism dynamics has handered the practical application of this kind of robots when the cable elasticity can not be neglected.A method based on Riemannian Geometry to deal with the issue of boundary control of dynamics mechanism system of cable-driven parallel robots with 2 linearly elastic cables have been proposed.Another method is presented based on the creation of novel mechanisms suitable for practical applications,mechanism dynamics of which is solved easily by combining the robots with other mechanisms(or new end-effectors),mechanism configuration,dynamics and motion control of the end-effector for two-class linearly elastic cable-driven parallel mechanisms are investigated using both the theoretical investigation and experimental verification.1.Each cable of the first-type mechanisms is composed as a massless rigid strut with a linear spring.There is only one elastic cable in the second-type cable mechanisms composed of a rigid strut and a linear spring.The end-effector of these two mechanisms can obtain accelerated motion trajectories.2.The affine nonlinear state-space representation of the direct mechanism dynamics of these two-class cable mechanisms is derived and the informal representation of differential flatness are given.The correctness of the the informal representation of differential flatness are proven using linearization of nonlinear control,differential algebra as well as generalized controller form via quasi-state static feedback linearization,and the linearized and decoupled system with a Brunovsky-type canconical form diffeomorphic to the previous direct mechanism dynamics is found respectively using the property of differential flatness.3.The feedforward control of the motion of the end-effector is achieved through the design of the inverse system of mechanism dynamics system for the two-class linearly elastic cable-driven parallel mechanisms on the basis of the differential parameterization of the flat outputs.In order to ensure the control performance,an outer linearized feedback controller for the asymptotically stable trajectory tracking of the end-effector is proposed on the basis of the Brunovsky canconical system in the continuous domain.The principle,signal procedure and design guidelines of the cable robot system contained the controller are analyzed,then the design idea of quadratic optimal servo tracking for the error feedback controller is given,and the case study for the control simulation of the error feedback controller is presented,as well as the design idea for the error feedback trajectory tracking controller considering the disturbing errors.These research outcomes can provide research ideas,methods and conclusions applied in the cable-driven parallel robots with elastic cables for special applications to fulfill the requirement of the control performance of the end-effector.4.An experimental protype for the cable-driven parallel robot mechanism with2 elastic cables is built to achieve the real-time acquisition of state variables and quadratic optimal servo tracking for the error feedback system,and the experimental investigation for the motion control of the end-effector is given to indicate the validity of the theoretical research outcomes.