Abstract
Traditional simulation methods are unable to meet the requirements of lunar takeoff simulations, such as high force output precision, low cost, and repeated use. Considering that cable-driven parallel mechanisms have the advantages of high payload to weight ratio, potentially large workspace, and high-speed motion, these mechanisms have the potential to be used for lunar takeoff simulations. Thus, this paper presents a parallel mechanism driven by nine cables. The purpose of this study is to optimize the dimensions of the cable-driven parallel mechanism to meet dynamic workspace requirements under cable tension constraints. The dynamic workspace requirements are derived from the kinematical function requests of the lunar takeoff simulation equipment. Experimental design and response surface methods are adopted for building the surrogate mathematical model linking the optimal variables and the optimization indices. A set of dimensional parameters are determined by analyzing the surrogate mathematical model. The volume of the dynamic workspace increased by 46% after optimization. Besides, a force control method is proposed for calculating output vector and sinusoidal forces. A force control loop is introduced into the traditional position control loop to adjust the cable force precisely, while controlling the cable length. The effectiveness of the proposed control method is verified through experiments. A 5% vector output accuracy and 12 Hz undulation force output can be realized. This paper proposes a cable-driven parallel mechanism which can be used for lunar takeoff simulation.
Highlights
In the third phase of the Chinese lunar exploration project, the verification of lunar takeoff technology will be completed by Chang’e V probe [1]
The available methods for simulating the low-gravity environment on the lunar surface could be classified into four categories, namely, the inertia compensation method [2], the buoyancy balance method [3], the rigidity parallel mechanism simulation method [4], and the sling suspension method [5]
Eng. (2019) 32:73 potentially large workspace, and high-speed motion [6], a parallel mechanism driven by nine cables is proposed for lunar takeoff simulation
Summary
In the third phase of the Chinese lunar exploration project, the verification of lunar takeoff technology will be completed by Chang’e V probe [1]. The objectives of this study are to optimize the dimensions of the CDPM to meet the workspace requirements, and to design a control method to meet the force accuracy requirements. Based on the abovementioned requirements, the CDPM should output the force with high precision and have enough dynamic workspace to output the desired acceleration for the desired time. The “optimal design” in this study aims at obtaining a better set of dimension parameters for the CDPM to meet dynamic workspace requirements under cable tension constraints. We define the variable SUM_DWS as the number of sample points belonging to the dynamic workspace.
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