| Cable-Driven Parallel Robot has the characteristics of high precision, high load capacity, light weight, small inertia and large workspace. It is widely used in medical rehabilitation equipment, heavy lifting equipment, high-speed machinery manufacturing and other applications. However, since the cable can only withstand tension but can’t push. The Cable-Driven Parallel Robot with n degree freedom should be driven by at least n+1 cables. This redundant driving will results in the complexity of solving the cable force. It also creates a great deal of difficulties in control and increases the cost of mechanism. If we add springs to the Cable-Driven Parallel Robot and provide the passive force by the springs in the form of Cable-Spring Hybrid Mechanism, the number of degree freedom of this mechanism is equal to the number of cable that can keep certain tension and achieve the movement of mechanism. This can keep the advantage of cable driving mechanism and also can avoid the shortage of cable force. This paper concentrates on the analysis of the characteristic of Cable-Spring Hybrid Mechanism, which is shown as follows:1) Extend the jacobian matrix of the Cable-Driven Parallel Robot to the Cable-Spring Hybrid Mechanism. Based on the wrench closure workspace of three degree-of-freedom restrained Cable-Driven Parallel Robot, a method is put forward to solve feasible workspace of the Cable-Spring Hybrid Mechanism and calculated the workspace of different configuration of the hybrid mechanism. Single variable method is proposed to analyze the effects of workspace by altering the spring location, the initial length and stiffness. Based on the genetic algorithm, an algorithm program is proposed to optimize the structure and the spring’s parameters of the Cable-Spring Hybrid Mechanism. An indicator to measure the quality of workspace is put forward and an example is calculated and analyzed.2) A kinematics analysis theory of Cable-Spring Hybrid Mechanism is proposed. The kinematics analysis theory of the Cable-Spring Hybrid Mechanism consists in describing the theory and deducing the mathematical formula from the position, velocity, acceleration and statics.The position equation, one-order influence coefficient matrix, second-order influence coefficient matrix and force balance equation which contains thespring force is deduced and an example is calculated and analyzed.3) Firstly, the dynamic model of end effector of the Cable-Spring Hybrid Mechanism is established. Secondly, the system dynamic model of mechanism was established with combining the dynamics model of driver and the end effector. Thirdly, the stiffness characteristic of the Cable-Spring Hybrid Mechanism is analyzed and the Heather matrix of the active stiffness is deduced. Finally, the effect of adding the spring to cable-spring hybrid mechanism of the system stiffness is analyzed and an example is calculated and analyzed. Based on the multivariate nonlinear equations linearized, the vibration equation of the system is established4) The kinematics and dynamics model of the Cable-Spring Hybrid Mechanism is set up in ADAMS software. At the same time, the inverse kinematics and inverse dynamics model were established in SIMULINK. Through the co-simulation of MATLAB and ADAMS, the inverse solution that calculated by MATLAB is input to ADAMS to verify the correctness of the kinematics and the dynamics analysis of the mathematical model which established in this paper. |
PDF Full Text Request