Mechanism Design And Experiments Of A Semi-physical System For The Simulation Of Weak Collision

The semi-physical ground test system is a key technology of the ground test for the space equipment, and also the necessary test equipment of China’s lunar exploration project. The core of this system is a motion simulator. To faithfully simulate the collision in space, the motion simulator is required to have high rigidity, high load, high accuracy, and good dynamic response. Moreover, large 6DOF workspace and isotropy are required especially due to the feature of the weak collision. The current motion simulators are not qualified for the simulation of the weak collision, because there are many problems in fast dynamic response, large workspace and isotropy. This article proposed a new motion simulator that has high performance to meet the needs of the ground test experiments, and designed the simulator from the configuration, the geometrical parameters, till the actuators. Then the proposed simulator was calibrated after assembly. The details are as follows:(1) A dual motion simulator cooperation system with 9-DOF was proposed. Through the modeling of the ground test experiment, specific design requirements were proposed. The configuration was designed with the GF Sets for the two motion simulator according to these requirements. A novel type of 6-DOF parallel mechanism was proposed with 3-3 orthogonal configuration which is used for the collision simulation. This structure has larger workspace, better dynamic response and isotropy, less prone to singularity. As a parallel mechanism, it also has high rigidity, high load, and high accuracy. Then the kinematics modeling, control strategy design, and virtual reality system building were performed sequentially.(2) Key points based dimensional design. A new description method was proposed, which could fully and concisely describe the 6-D workspace. A class of key point characteristics of the motion simulator was found. With these characteristics, a fast and precise dimensional design method was proposed. Moreover, the interference and singularity of the motion simulators were analyzed.(3) Dynamics based dimensional design. The equivalent mass and stiffness of the system was studied. And then the relationships between the geometrical parameters and the equivalent stiffness / natural frequency were established. Based on these relationships, the advanced design of the geometrical parameters was taken with the key point method and optimization algorithm.(4) Drive system design with the goal of improving the dynamic response. The dynamic model and a mechatronics digital prototype of the motion simulator were built. With these dynamic models, the relationship between the required drive capability and the actuator was analyzed. Based on this, the drive system was designed. Finally, the workspace and dynamic response of the system were checked with experiments.(5) This article took a comprehensive analysis of the factors affecting the accuracy of the system, and established the relationship between the error of the geometrical parameters and the output error of the moving platform. A calibration method was proposed to separate the structure errors, and two calibration models were built. Then the models were evaluated by the computer simulation experiments. Finally, a set of calibration experimental program was proposed according to the difficulty of practice, and then used for the calibration of the system.