## 1 Introduction  
Hand-transmitted vibration refers to the mechanical vibration or shock directly acting on or transmitted to the human arm when using handheld vibration tools or contacting vibrating workpieces in production. When astronauts carry out extravehicular activities, the hand-transmitted vibration of EVA power tools can easily cause astronauts to feel uncomfortable or even tired [1]. Coupled with the joint actions of many factors, such as low orbit zero-gravity [2], thermal circulation [3, 4], extravehicular spacesit [5, 6, 7], and so on, the muscle movement ability and fine operation ability of astronauts are decreased in varying degrees, which will threaten the health of astronauts and affect the successful implementation of maintenance missions. At present, it is difficult to simulate and verify the measurement conditions of hand-transmitted vibration of EVA power tools. Based on the hand-transmitted vibration test, the theoretical prediction model research is carried out to accurately obtain the vibration exposure of EVA power tools. It is of great significance to guide the frequency of manned on-orbit maintenance missions and to predict the maximum workload of astronauts [8, 9]. At present, the research on the prediction model of hand-transmitted vibration of many scholars is focused on the biomechanical model, mostly based on the simplified physical model to establish the dynamic equation of hand-transmitted vibration for parameter identification to predict the vibration transmissibility or acceleration magnitude. [PERSON] et al. [10, 11, 12, 13] studied the four-degree-of-freedom model and five-degree-of-freedom model of the arm system based on two-point coupling, which are used to predict the vibration power absorption (VPA) and distribution of the arm substructure. [PERSON] et al. [14]used the curved arm six-degree-of-freedom model to predict the vibration transmissibility of bare hands, air bladder gloves, and gel-filled gloves. [PERSON] et al. [15] estimated VPAs using biomechanical models of the hand-arm system derived from both the driving-point mechanical impedance and distributed vibration transmissibility. [PERSON] et al. [16] proposed a seven-degree-of-freedom model of the foot-ankle system to predict the dynamic response of the vibration transmitted to the foot in a specific frequency range. At the same time, some scholars use the method of establishing a finite element model of the arm system to study hand-transmitted vibration. [PERSON] et al. [17] proposed a hybrid hand-arm finite element model considering bone, soft tissue, and connective tissue to predict the vibration of the forklift steering wheel to the hand when different grasping forces are applied. [PERSON] et al. [18] developed a hybrid finger model based on the traditional finite element model, multi-body musculoskeletal model, and lumped parameter model to predict the local vibration behavior of fingers. [PERSON] et al. [19] developed a hybrid finite element hand-gripping model that combines the features of conventional finite element models and multi-body dynamic models to simulate hand-gripping on a cylindrical handle with covering materials of different softness levels. In the actual operation of power tools, vibration exposure, as a physical quantity that can more directly reflect the impact of hand-transmitted vibration on human health, has not been reported at present. On-orbit replacement unit (ORU) is a modular component applied to the space station or large and medium-sized spacecraft in orbit. When ORU reaches its design life or fails, astronauts mainly use EVA power tools to replace it in orbit, to complete the update and maintenance of spacecraft components. Aiming at the on-orbit maintenance method of the Chinese space station, which is mainly based on the on-orbit replacement of the ORU and supplemented by the internal maintenance of the ORU. Beijing Institute of Spacecraft Environment Engineering has developed a pistol power tool (PPT).