The Rope Pulling Parallel Mechanism A Number Of Key Theoretical Issues In The Wind Tunnel Support System In Applied Research

Based on a review of the state-of-the-art theory and technology about the wire-driven parallel kinematic manipulators (PKMs), disregarding further restrictions due to currently available technology, the exposition of the research subject "Research on Key Theoretical Issues of Wire-Driven Parallel Kinematic Manipulators and the Application to Wind Tunnel Support Systems" focuses on new perspectives of wire-driven PKMs inherent in the concept themselves, key techniques and design methodology of wire-driven parallel support systems in wind tunnels, so that it could give an overall theoretical research of what can be achieved at most in the aspects of structure, workspace, optimal tension distribution, static stiffness, kinematics, design methods and motion control schemes of wire-driven parallel support systems in wind tunnels.At first, the constraint equation of wire-driven manipulators with holonomic constraints is built and analyzed. And its partial differential equation is set up to analyze the mobility and controllability of the manipulators. The number of end-effector's degrees of freedoms(DOFs) is defined as the dimension n of linearity space R~n which is positively spanned by all of the column vectors of the structure matrix J~T, obtained from the force equilibrium equation transforming forces in actuator space into wrenches in end-effector space. The number of the combinations of end-effector's DOFs, which a wire-driven PKM can have evenly in all postures has been proven. On the other hand, on the connections between wire-driven PKMs and multi-finger grasp, the architecture correspondence and similarity of force transmission between a wire-driven PKM and its corresponding grasp with frictionless point contacts has been exploited, and the close relationship between force-closure grasp planning and the number of the combinations of end-effector's DOFs has been discussed.Then, the definition of Controllable Workspace(CWS) is given according to the fact whether a posture of the moving platform is controllable or not. CWS is classifiedinto Force-Closure Workspace(FCW, for short), Static Equilibrium Workspace under Gravity(SEWG for short) and Dynamic Equilibrium Workspace(DEW for short) according to the property of the wrenches exerting on the moving platform. The methods of determining the workspace volume of every kind of CWS are given, especially, some important conclusions and theorems are obtained to determine the workspace volume and its boundary of FCW. Also, force transmission index based workspace analysis of CRPMs is conducted. It is proposed that the singularity with over-mobility of wire-driven PKMs is due to the wrench deficiency of the moving platform because the dimension of the set of wrench decreases. And the influence of the gravity of the moving platform on the wrench deficiency is discussed. Using Planar Antipodal Grasp Theorem, a way to build up singularity-free CRPMs in 1R2T class with 2-2 type and 2R3T class with 3-3 type is proposed. Considering the fact that a wire-driven PKM with the decoupling of every rotational DOFs and the translational DOFs completely controlled is singularity-free, a way to build up singularity-free CRPMs in 1R2T class with 1-2-1 type, RRPMs in 2R3T class with 2-3-2 type is proposed. Using the theorem of 3-dimension force-closure grasp proposed by Canny, a method to build up singularity-free RRPMs in 3R3T class with 3-3-3 type is presented.Furthermore, considering the tension limits, the optimal tension distribution problem can be transformed into a nonlinear optimization problem on a convex polyhedron, which the optimal solution can be the linear interpolation of the lowest solution and the highest solution, in order to deal with the disadvantages of the optimal solutions solved by the traditional methods. To solve the discontinuity of the optimal solutions in some cases such as in a singular posture, the optimal solution can be approximately expressed by its p-norm. The programming in the environment of Matlab is developed to solve the optimal solutions.Moreover, a rat...