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Parameter identification of space manipulator’s flexible joint

Wojtunik Mateusz, Basmadji Fatina Liliana, Granosik Grzegorz, Seweryn Karol

Journal of Automation Mobile Robotics and Intelligent Systems

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2023

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Vol. 17, No. 3

78--87

EN

A manipulator mounted on a satellite is often used to perform active debris removal missions. The space manipulator control system needs to take the dynamic model of the satellite‐manipulator system into account because of the influence of the manipulator motion on the position and attitude of the satellite. Therefore, precise modeling of the space manipulator dynamics as well as parameter identification are needed to improve the credibility of the simulation tools. In this paper, we presented the identification of the flexible‐joint space manipulator model based on dynamic equations of motion. Experiments were performed in an emulated microgravity environment using planar air bearings. The arbitrarily selected joint‐space trajectory was performed by the manipulator’s control system. The experiments were repeated multiple times in order to analyze the identification method sensitivity. The identification is based on the Simulink SimMechanics model. Thus, the procedure can be used for any space manipulator without the need to obtain analytical relations for dynamic equations each time. Including joint flexibility and spring viscous damping in the dynamic model allowed it to reflect the experimental measurements better than the reference model could. Identified parameters of the flexible joint have values of the same magnitude as corresponding real system parameters.

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Application of the KUKA KUBE test-bed for the hardware-in-the-loop validation of the space manipulator control system

Wojtunik Mateusz, Łuczak Piotr, Rybus Tomasz, Granosik Grzegorz

Artificial Satellites : Journal of Planetary Geodesy

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2023

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Vol. 58, Special Issue 1

231--248

EN

The on-ground validation of control systems designed for manipulators working in orbit is very difficult due to the necessity of simulating the microgravity environment on Earth. In this paper, we present the possibilities of utilising the KUKA KUBE test-bed with industrial robots to experimentally verify space systems using hardware-in-the-loop tests. The fixed-base KUKA industrial robot is operated in gravitational environment, while the space system model plant is solved in real time parallel to on-ground experiment. The test-bed measurements are the input of the model plant, and the output of the model is treated as an input for the industrial robot actuation. In the performed experiment, the control system based on the Dynamic Jacobian is validated. The desired point that is reached by the manipulator’s endeffector is constant in the simulated environment and moving with respect to the test-bed frame. The position of the space manipulator’s end-effector is calculated by evaluating dynamics of the satellite in real-time model. The results show that the control system applied to the KUKA robot works correctly. The measurements from the torque sensors mounted in KUKA robot’s joints are in accordance with the simulation results. This fact enhances the possibilities of gravity compensation, thus simulating microgravity environment on the test-bed.

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Active 6 DoF force/torque control based on Dynamic Jacobian for free-floating space manipulator

Dyba Filip, Rybus Tomasz, Wojtunik Mateusz, Basmadji Fatina Liliana

Artificial Satellites : Journal of Planetary Geodesy

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2023

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Vol. 58, Special Issue 1

214--229

EN

In-orbit capture of a non-cooperative satellite will be a major challenge in the proposed servicing and active debris removal missions. The contact forces between the manipulator end-effector and the elements of the target object will occur in the grasping phase. In this paper, an active 6 Degrees of Freedom (DoF) force/torque control method for manipulator mounted on a free-floating servicing satellite is proposed. The main aim of the presented method is to balance the relation between end-effector position and force along each direction in the Cartesian space. The control law is based on the Dynamic Jacobian, which takes into account the influence of the manipulator motion on the state of the servicing satellite. The proposed approach is validated in numerical simulations with a simplified model of contact. Comparison with the classical Cartesian control shows that the active 6 DoF force/torque control method allows to obtain better positioning accuracy of the end-effector and lower control torques in manipulator joints in the presence of external forces.

4

Identyfikacja parametrów elastycznego przegubu manipulatora kosmicznego

Wojtunik Mateusz, Basmadji Fatina Liliana, Granosik Grzegorz, Seweryn Karol

Prace Naukowe Politechniki Warszawskiej. Elektronika

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2022

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z. 197, t. 1

157-168

PL

Wykorzystanie manipulatora umieszczonego na satelicie jest jedną z metod rozpatrywanych w kontekście przeprowadzenia misji usuwania kosmicznych śmieci. Układy sterowania manipulatorami kosmicznymi muszą wykorzystywać model dynamiki ze względu na wpływ ruchu manipulatora na pozycję i orientację satelity serwisowego. Istotne jest więc projektowanie precyzyjnych modeli matematycznych pozwalających na odzwierciedlenie rzeczywistego układu. W tym celu konieczna jest identyfikacja parametrów modelu. W pracy przedstawiona została identyfikacja parametrów elastycznego przegubu manipulatora kosmicznego w oparciu o model dynamiki. Testy wykonano w emulowanych warunkach mikrograwitacji. Wykorzystanie modelu uwzględniającego elastyczność w przegubie pozwoliło na poprawę zgodności pomiędzy symulacją a przebiegami testowymi. Zidentyfikowane parametry osiągają wartości zgodne z rzeczywistymi.

EN

It is considered to use a manipulator mounted on a satellite in order to perform active debris removal missions. Space manipulator control systems need to take dynamic model into account because of the influence of the manipulator motion on the position and attitude of the satellite. Therefore, precise modelling of the system’s dynamics as well as parameter identification are needed in order to reflect the real systems behaviour better. In this paper we presented the identification of the flexible-joint space manipulator model based on dynamic equations of motion. Experiments were performed in emulated microgravity environment using planar air bearings. Including joint flexibility in the dynamic model allowed to reflect the experimental measurements better than the reference model. Identified parameters of the flexible joint have values corresponding to real system parameters.