Tong Zhizhong

Hybrid Realtime Simulation of the Space Docking Process

In order to test the space docking mechanism on the ground, the docking process of two spacecrafts must be simulated. The hybrid simulation (hardware-in-loop simulation) is a preferred method for its great applicability to different spacecrafts. Therefore, a space docking hybrid simulation (SDHS) prototype system is established. In this system actual spacecrafts are replaced by virtual ones and the docking dynamics model is built according to moment of momentum equations of the spacecrafts. Then a distributed realtime computer system is used for calculating the relative motion of the spacecrafts and driving a Stewart platform to implement this motion. Adopting an imitated docking mechanism in the experiment, the whole process of space docking is simulated successfully. On the basis of this system, a SDHS system using for testing actual docking mechanisms can be constructed in the future

Modal space decoupled optimal design for a class of symmetric spatial parallel mechanisms with consideration of passive joint damping

In this study, we analyze the influence of passive joint viscous friction (PJVF) on modal space decoupling for a class of symmetric spatial parallel mechanisms (SSPM). The Jacobian matrix relating the platform movements to each passive joint velocity is first gained by vector analysis and the passive joint damping matrix is then derived by applying the Kane method. Next, an analytic formula index measuring the degree of coupling effects between the damping terms in the modal coordinates is proposed using classical modal analysis of dynamic equations in task space. Based on the index, a new optimal design method is found which establishes the kinematics parameters for minimizing the coupling degree of damping and achieves optimal fault tolerance for modal space decoupling when all struts have identical damping and stiffness coefficients in their axial directions. To illustrate the effectiveness of the theory, the new method was used to redesign two configurations of a specific manipulator.

Visual design study and implementation for 3 DOF parallel kinematic manipulator

Traditional design of 3-DOF parallel kinematic manipulator is a serial design, in which physical prototype based design and verification bring about restrictions to the development period and efficiency. In order to realize rapidly and efficiently from the conceptual design step to prototyping step, its proposed to combine VR with kinematics analysis, structure design and kinetic analysis to develop a visual design environment (VDE). Based on visualization of kinematic solutions the analysis results can fully account for kinematic behavior of the real machine. Moreover, the verification based on kinetic mode makes sure the design reasonable and reliable. Compared with traditional design our developed routines are very effective. In this paper the implementation is described in detail