Development of On-orbit Assembly Demonstrator in 3U CubeSat Form Factor

The use of robotics in space has become common in the last half century of space exploration. However, robotic arms are rarely entrusted to perform large assembly tasks without a human in the loop because of the high cost of the hardware involved. As our presence in space grows, developing advanced autonomous robotic systems may be the way forward as time lags associated with teleoperation can easily cripple future space missions operating beyond earth orbit. This research focuses on the derivation of an autonomous control system for spacecraft assembly applications that blends Jacobian path following and visual servoing. Jacobian path following assumes the environment is well known and plans end effector trajectories whose performance for assembly may suffer in dynamic or uncertain environments. Visual servoing approaches use feedback from an effector attached camera and can avoid dynamic obstacles, but provides no guarantee of success if the sensor cannot keep the goal location in its field of view and often traverses inefficient manipulator trajectories. This work proposes a hybrid approach that combines both approaches to improve the performance of a robotic manipulator in both known and unknown environments. The robotic systems are simulated using the proposed hybrid controller. The hybrid controller is developed in MATLAB using a kinematic simulation of a two degree of freedom robotic arm operating in a single plane with a simplified camera model. Following successful implementation of the simulation, a more complex robotic arm is simulated in 3D space. The controller is integrated into an existing robotic arm platform (UR5 Industrial Manipulator) for a proof of concept. The results of the testing highlights the path and final position of each controller to demonstrate the advantages of each controller individually and the advantages of the hybrid approach. The paper describes the algorithm development and results of analysis and testing.