A symmetrical robotic arm design approach with stereo-vision ability for CubeSats

Abstract

This paper introduces a design of a robotic system that can be mounted on a CubeSat. Robotic arms should be small enough to be mounted on a size as 30×10×10 cm or smaller. Meanwhile, robotic arms should provide sufficient space for their actuators, cameras and sensors. The robotic design has one camera on each arm to be used for stereo-vision ability. Velocity and position feedback are desired to be used for controlling the robotic arm's position and minimizing the speed of the arms' motion to reduce the disturbance on attitude control subsystem during arm motions. Each arm provides 5 degrees of freedom. For control design of the system, the Denavit-Hartenberg convention is used for forward and backward kinematics modeling, therefore the position and the orientation of the camera can be calculated after receiving a command from the ground station or ready mission parameters from the memory. By using forward kinematics matrices, the Jacobian matrix will be presented for the system, and it will be used to calculate the inertial tensor matrix which includes the effects of the mass and inertia. After calculating the inertial tensor matrix, Euler-Lagrangian method will be used for dynamic modeling which includes the nonlinear coriolis and centrifugal effects with the inertial forces. The dynamic equation of motion for two arms which includes inertial forces, coriolis and centrifugal effects, friction forces and gravity will be presented for space and the micro gravity environment. Moreover, spin-stabilized satellite motion effect is added to robotic arms' the dynamic equation of the motion. The dynamic equation is used with the proportional-integral coefficients for modeling the control of the prismatic links' actuators chosen for the arms.