Hybrid Force/Velocity Control for Simulating Contact Dynamics of Satellite Robots on a Hardware-in-the-Loop Simulator

Contact operations of free-floating satellite robots are difficult and risky and therefore, they must be thoroughly tested and verified by ground-based facilities. A hardware-in-the-loop (HIL) simulation system with industrial robots is commonly used for simulating space robotic operations. However, a great challenge is to handle simulation divergence due to intrinsic time delay between the measured forces and the simulation driven reaction of the robot. This paper presents a novel hybrid force/velocity control method for compensating the time delay of a HIL simulation. A real-time identification method for contact stiffness and damping is proposed based on the adaptive Kalman filter. Then, an energy observer is designed to monitor the energy flow and an energy controller (EC) is established. The EC acts a variable damping and thus the contact damping is amended. Therefore, a compensation strategy based on parameter identification and damping amendment is proposed to eliminate the effects of time delays. Finally, numerical simulations and experimental results show that the simulation divergence due to time delay can be prevented. Moreover, space robotic operations with high fidelity of both contact force and contact velocity are reproduced by the proposed method.