Motion Simulation in Virtual Environment of Flying Robots Inside Orbital Space Stations

The task of motion simulation of flying manipulation robots used in space modules in near-earth orbit is considered. As part of this task, a nonlinear mathematical model of flying robot dynamics was obtained, in which manipulator mass and dimensions are significantly less than those of the base link. The resulting mathematical model is used to motion control synthesis of the flying robot based on sliding modes. The proposed solution consists in providing such control that ensures the absence of oscillations in the vicinity of sliding surface. For this purpose, the control law of the flying robot is implemented using a continuous hyperbolic tangent function, which is an approximation of the discontinuous switching function. This approach makes it possible to effectively implement the robot’s movement along a given trajectory, its reorientation and stabilization. The approbation of methods and approaches proposed in the paper was carried out in virtual environment complex VirSim created by the authors. In this software package, the manipulation robot dynamics is performed using a universal sequential impulses method, which allows to handle various types constraints that arise due to the joints of robot links, body collisions, friction, etc. The flying robot control is implemented by means of a created functional diagram scheme that computes the control actions applied to the robot’s actuators based on virtual sensors readings and flight program’s input commands. Regarding this, the robot manipulator control in this complex is performed using PD controllers and inverse kinematics solving to ensure the required position of robot’s end effector (gripper). Simulation results showed the adequacy of the solutions proposed in the paper, which can be further used to flying robot control when solving more complex tasks related to the grip and transfer load inside the orbital station. 

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