Emulating On-Orbit Interactions Using Forward Dynamics Based Cartesian Motion

The paper presents a novel Hardware-In-the-Loop (HIL) emulation framework of on-orbit interactions using on-ground robotic manipulators. It combines Virtual Forward Dynamic Model (VFDM) for Cartesian motion control of robotic manipulators with an Orbital Dynamics Simulator (ODS) based on the Clohessy Wiltshire (CW) Model. VFDM-based Inverse Kinematics (IK) solver is known to have better motion tracking, path accuracy, and solver convergency than traditional IK solvers. Therefore it provides a stable Cartesian motion for manipulator-based HIL on-orbit emulations. The framework is tested on a ROS-based robotics testbed to emulate two scenarios: free-floating satellite motion and free-floating interaction (collision). Mock-ups of two satellites are mounted at the robots' end-effectors. Forces acting on the mock-ups are measured through an in-built F/T sensor on each robotic arm. During the tests, the relative motion of the mock-ups is expressed with respect to a moving observer rotating at a fixed angular velocity in a circular orbit rather than their motion in the inertial frame. The ODS incorporates the force and torque values on the fly and delivers the corresponding satellite motions to the virtual forward dynamics model as online trajectories. Results are comparable to other free-floating HIL emulators. Fidelity between the simulated motion and robot-mounted mock-up motion is confirmed.Comment: Submitted to ICRA2023, for associated video, see: https://www.youtube.com/watch?v=N2KYCKJ4KM

Six-DOF Spacecraft Dynamics Simulator For Testing Translation and Attitude Control

This paper presents a method to control a manipulator system grasping a rigid-body payload so that the motion of the combined system in consequence of externally applied forces to be the same as another free-floating rigid-body (with different inertial properties). This allows zero-g emulation of a scaled spacecraft prototype under the test in a 1-g laboratory environment. The controller consisting of motion feedback and force/moment feedback adjusts the motion of the test spacecraft so as to match that of the flight spacecraft, even if the latter has flexible appendages (such as solar panels) and the former is rigid. The stability of the overall system is analytically investigated, and the results show that the system remains stable provided that the inertial properties of two spacecraft are different and that an upperbound on the norm of the inertia ratio of the payload to manipulator is respected. Important practical issues such as calibration and sensitivity analysis to sensor noise and quantization are also presented

Hybrid Simulator for Space Docking and Robotic Proximity Operations

In this work, we present a hybrid simulator for space docking and robotic proximity operations methodology. This methodology also allows for the emulation of a target robot operating in a complex environment by using an actual robot. The emulation scheme aims to replicate the dynamic behavior of the target robot interacting with the environment, without dealing with a complex calculation of the contact dynamics. This method forms a basis for the task verification of a flexible space robot. The actual emulating robot is structurally rigid, while the target robot can represent any class of robots, e.g., flexible, redundant, or space robots. Although the emulating robot is not dynamically equivalent to the target robot, the dynamical similarity can be achieved by using a control law developed herein. The effect of disturbances and actuator dynamics on the fidelity and the contact stability of the robot emulation is thoroughly analyzed

Modeling, Stability Analysis, and Testing of a Hybrid Docking Simulator

A hybrid docking simulator is a hardware-in-the-loop (HIL) simulator that includes a hardware element within a numerical simulation loop. One of the goals of performing a HIL simulation at the European Proximity Operation Simulator (EPOS) is the verification and validation of the docking phase in an on-orbit servicing mission.....Comment: 30 papge

Development of On-Ground Hardware In Loop Simulation Facility for Space Robotics

Over a couple of decades, space junk has increased rapidly, which has caused significant threats to the LEO operation satellites. An Active Debris Removal $(ADR)$ concept continuously evolves for space junk removal. One of the ADR methods is Space Robotics, whose function is to chase, capture and de-orbit the space junk. This paper presents the development of an on-ground space robotics facility in the TCS Research for on-orbit servicing $(OOS)$ like refueling and debris capture experiments. A Hardware in Loop Simulation (HILS) system will be used for integrated system development, testing, and demonstration of on-orbit docking mechanisms. The HiLS test facility of TCS Research Lab will use two URs in which one UR is attached to the RG2 gripper, and the other is attached to a force-torque sensor and with a scaled mock-up model. The first UR5 will be mounted on a 7-axis linear rail and contain the docking probe. First, UR5 with a suitable gripper has to interface its control boxes. The grasping algorithm was run through the ROS interface line to demonstrate and validate the on-orbit operations. The manipulator will be mounted with LIDAR and a camera to visualize the mock-up model, find the target model's pose and rotational velocity estimation, and a gripper that will move relative to the target model. The other manipulator has the UR10 control, providing rotational and random motion to the mockup, enabling a dynamic simulator fed by force-torque data. The dynamic simulator is fed up with the orbit propagator, which will provide the orbiting environment to the target model. For the simulation of the docking and grasping of the target model, a linear rail of a 6m setup is still in the procurement process. Once reaching proximity, the grasping algorithm will be launched to capture the target model after reading the random motion of the mock-up model.Comment: 11 pages, 15 figures, Accepted at Small Satellite Conference 2023; Weekday Sessions: Orbital Debris, SSA & STM; Tuesday, 8th Aug 202

Development of On-Ground Hardware In Loop Simulation Facility for Space Robotics

Over a couple of decades, space junk has increased rapidly, which has caused significant threats to the LEO operation satellites. A mitigating measure should be taken to protect the LEO space environment. An Active Debris Removal (ADR) concept continuously evolves for space junk removal. One of the ADR methods is Space Robotics, whose function is to chase, capture and de-orbit the space junk. This paper presents the development of an on-ground space robotics facility in the TCS Research for on-orbit refueling and debris capture experiments. A Hardware-in-Loop Simulation (HILS) system will be used for integrated system development, testing, and demonstration. HILS is the most effective and vital system to test the on-orbit docking mechanism\u27s reliability, usability, and safety. The HiLS test facility of TCS Research Lab will use two Universal Robot(UR)5e and UR10 manipulators in which one manipulator is attached to the robotic-RG2 gripper, and the other is attached to a force-torque sensor named Hexa-E Onrobot and with a scaled mock-up satellite model. The first UR5 manipulator will be mounted on a 7-axis linear rail and contain the docking probe. First UR5 manipulator with the suitable gripper has to interface its control boxes. The grasping algorithm was run through the ROS interface line to demonstrate and validate the On-orbit and Debris removal operation. The manipulator will be mounted with LIDAR and a Real sense camera to visualize the mock-up model, find the target model\u27s pose and rotational velocity estimation, and a gripper that will move relative to the target model. The other manipulator has the UR10 control, providing rotational and random motion to the mock-up satellite, enabling a dynamic simulator fed by force-torque data. The dynamic simulator is fed up with the orbit propagator model SGP4, which will provide the orbiting environment to the target model. For the simulation of the docking and grasping of the target model, a 7-axis linear rail of a 6-meter setup is still in the procurement process. Once reaching proximity, the grasping algorithm will be launched to capture the target model after reading the random motion of the mock-up satellite model. The HILS system proposed in this paper helps develop on-orbit servicing (OOS) like repairing, upgrading, transporting, rescuing technologies, on-orbit refueling and berthing and debris removals

DETC2009-86529 IMPEDANCE CONTROL OF MANIPULATORS WITH HEAVY PAYLOAD FOR SPACECRAFT RENDEZVOUS & DOCKING SIMULATORS

ABSTRACT This paper presents a method to control a manipulator system grasping a rigid-body payload so that the motion of the combined system in consequence of external applied forces to be the same as another free-floating rigid-body (with different inertial properties). This allows zero-g emulation of a scale