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Trans. JSASS Aerospace Tech. Japan Vol. 12, No. ists29, pp. Pc_9-Pc_14, 2014 Original Paper Contact Dynamics Analysis for HTV Capturing by SSRMS 1) 1) 2) 3) By Akihiko HONDA , Mitsushige ODA , Hiroki NAKANISHI and Satoshi SUZUKI 1) Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, Tokyo, Japan 2) Japan Aerospace Exploration Agency, Tsukuba, Japan 3) Advanced Engineering Services Co.,Ltd., Tsukuba, Japan (Received June 24th, 2013) This paper discusses a contact dynamics which is happened when a massive spacecraft named H-II Transfer Vehicle (HTV) is captured by a Space Station Remote Manipulator System (SSRMS). If the point of the first contact is different from the planned one, then HTV’s motion will be completely change and may collide with ISS. Therefore, if we can predict motion of HTV depending on the telemetry data in real operation time, it will be useful to assure safety of the mission. To develop a dynamics simulator, at first, we studied telemetry data obtained in the 1st HTV (HTV-1) capture operation. Then, we developed a simple models with some parameters. In that phase, some preliminary experiment and deliberation in kinematics was conducted to model mechanical behavior and determine parameters. Then, optimization of parameters was conducted to identify some unknown parameters of contact dynamics based on telemetry data. And with following the course of optimization, we discuss key parameters which have large effect on dynamic HTV’s behavior and can be used in developing a low calculation-cost model. Finally, we apply key parameters and compare the results with an actual telemetry data of HTV-2 to verify its efficiency. Key Words: Contact Dynamics, Numerical Analysis, Parameter Identification, HTV, SSRMS, Nomenclature Missions like the HTV capture becomes more important : elapsed time from start a capture factor to conduct such as orbital construction, debris removal operation with snare wire and re-supply. Therefore researches are proposed their (ݐ : stiffness of snare wire solution to assure safety of these missions. M. Oda et al4 : spring constant of contact developed a new control method of space robot arm to reduce ܭ a disturbances to satellite’s attitude. And K. Senda, et al5) : stiffness of Grapple Fixture base ܭ developed an air-float test bed for flexible manipulator to : angular velocity of wire elements ܭ verify their control method on the ground. On the other hand, ௪௜௥௘ : contact force between snare wire and ߱ S. Matsunaga, et al6) proposed a new debris handling end ௖ Grapple Fixture ܨ : displacement of snare wire effector using wires. As an approach of the dynamics p : parameter set simulator, Ou Ma developed flexible SSRMS model and ݔ conducted a simulation in which SSRMS handles some payloads7). And Uyama, et al. developed a model of snare Subscripts 8) : number of iterations wire and draw a comparison with experiment . ݇ 1. Introduction ©JAXA This paper discusses a contact dynamics which is occured when a massive spacecraft named H-II Transfer Vehicle (HTV) is captured by the Space Station Remote Manipulator System (SSRMS). HTV is an un-manned logistics supply vehicle1) whose mass is 16 metric tons and to carry logistics to the International Space Station (ISS). When SSRMS captures HTV, HTV will make rendezvous manoeuver to ISS and makes HTV’s relative velocity against ISS to be near zero. Then, SSRMS approaches HTV and captures a grapple fixture 2) (GF) mounted on HTV. Images of both HTV and SSRMS are Fig. 1. Overview of space station supplier; HTV and Space Station shown in Fig. 1. Remote Manipulator System; SSRMS. Copyright© 2014 by the Japan Society for Aeronautical and Space Sciences and ISTS. All rights reserved. Pc_9 Trans. JSASS Aerospace Tech. Japan Vol. 12, No. ists29 (2014) If we can predict a motion of HTV depending on the 2.2. Latching end effector and grapple fixture telemetry data from HTV and SSRMS in real operation time, To grasp with LEE, there are a GFs (Grapple©JAXA©JAXA Fixture) on it will be useful to assure safety of the mission. And, HTV. Fig.2 shows shapes of LEE and GF, and Fig.3 shows developing a real-time dynamics simulator has advantages in the capture sequence using these mechanisms. At a tip of the easily changing mechanical and environmental conditions and LEE, there are three metal, movable wires to fix the shaft part diversion to other missions. Therefore, we have been focusing of GF. The wires snare the shaft with closing and guide a and researching on dynamics simulator / teleoperation system position of the GF to center of LEE. After tighten up the shaft, for the contact operation. Current problems for the real-time the wires start pulling up the shaft and fix an attitude of GF dynamics simulator are existence of some unknown with adjusting a LEE to guide parts of the GF. Therefore, it is parameters in a contact dynamics and high calculation cost of important to analyze a contact wires and the shaft to simulate models. an initial contact phenomenon of capture operation. In this paper, we develop a dynamics simulator based on a one developed by Nakanishi9), et al and identify the some unknown parameters of contact dynamics with telemetry data. In developing the models, some preliminary experiment and deliberation in kinematics were conducted. And then, optimization of parameters was conducted to identify some unknown parameters of contact dynamics. For the purpose, we developed an optimization routine using the Nelder-Mead Simplex Method. And with following the course of optimization, we discuss key parameters which have large effect on dynamic behavior of HTV and can be used in Fig. 2. Overview of LEE and GF. developing a low calculation-cost dynamics model. Finally, we apply key parameters to our dynamics simulator with initial condition of HTV-2 and compare results with an actual telemetry data to verify its efficiency 2. HTV Capture with SSRMS 2.1. HTV and SSRMS HTV is an unmanned spacecraft which transport supplies to ISS. HTV was developed by JAXA to contribute ISS project after a retirement of a Space Shuttle. Major parameters of Fig. 3. Capture sequence using GF and LEE. HTV are indicated in Table 1. 3. Model Configuration Table 1. Major Parameters of HTV. Total Weight 16 [t] The models were developed with general-purpose multi Total Length 9.8 [m] body dynamics simulation software called ADAMS/View. Diameter 4.4 [m] And transient mechanical analysis was conducted by ADAMS/Solver. In this section, modeling capture The primary feature of HTV is that it docks to CBM mechanisms and preliminary experiment to determine models (Common Berthing Mechanism) of ISS. This feature provides are explained. an advantages to transportation because aperture size of CBM 3.1. Dynamics model of HTV and SSRMS is larger than other docking mechanisms. However, CBM HTV was modeled based on geometrical data provided by does not allow to dock directly unlike other mechanisms. JAXA. To adjust a dynamical behavior, a bushing element Therefore HTV is captured by a SSRMS10,11) (Space Station connects a GF parts and HTV main body. And mass and Remote Manipulator) once after rendezvous and attached to rotary inertia properties were also assigned based on provided CBM2). data. At the first place in simulation, the HTV is set to The SSRMS is a large, lightweight robotic arm used in provided initial velocity and then shifts to free draft condition. construction and transport operation on ISS. Table 2 are major SSRMS was also modeled base on geometrical data. parameters of SSRMS. The SSRMS has 7 degrees of freedom SSRMS has some number of operation modes and be assumed and 3 degrees of freedoms are allocated in both side of tip and to change modes in HTV capture operation. Therefore, 1 degree of freedom is in center. As end effector, SSRMS has time-variable force element which simulates a joint stiffness LEE12) (Latching End Effector) on both sides. torque and back drive torque is assign to each joint. The joint stiffness torque is applied on both in a manual operation mode Table 2. Major Parameters of SSRMS. and limp mode. On the other hand, the back drive torque is Max Length 17.6 [m] applied only in the limp mode. Total Weight 1.8 [t] Weight capacity 116 [t] Pc_10 A. HONDA et al.: Contact Dynamics Analysis for HTV Capturing by SSRMS 3.2. Mechanical model of latching end effecter 3.2.2. Moving speed The snare wires are modeled with rotational rod elements as Preliminary experiment was conducted to determine a change shown in Fig.4. Contact force functions are applied on of moving speed of wire using a mock-up of LEE and imaging between grapple shaft and rod elements and that reaction force sensor. From a result of the experiment, we conclude a moving is calculated based on differences between angular rotation speed of wire is nearly-constant if a mechanism is drove at command value and simulated operation-result value. Details constant rate. Fig. 6 shows result of the preliminary experiment. are mentioned in next part. From this result, the rod elements were modeled rotating at steady rate . Information about a real operating time was not provided fully, the rotate rate is a variable changed with ߱௪௜௥௘ operating time which the snare wire is moving to tighten up the shaft of GF. Fig. 4. Behavior of snare wire modeled with a rotation of rod elements. 3.2.1. Reaction force Fig. 6. Moving speed of snare wires. To modeling a vertical reaction force of snare wire, a simple model of the stretched wire which is fixed at both side is introduced into our model (Fig.5).

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