Indirect Force Control of a Cable-Suspended Aerial Multi-Robot Manipulator

We present the control in physical interaction with the environment of a Cable-suspended Aerial Multi-Robot Ma- nipulator (CS-AMRM) called the Fly-Crane, composed of three aerial vehicles towed to a platform by means of six cables. The control strategy enables the system to accurately and safely per- form tasks involving expected or unexpected interactions between the platform and the environment, in the absence of dedicated force/torque sensors. A previously developed Inverse Kinematic Controller (IKC) is enhanced with an admittance framework, and contacts are estimated through a generalized momentum- based observer. To assess the validity of our approach, and to provide practical insights into the method, we perform exten- sive experimental tests, comprehending the admittance property shaping to modulate stiffness, damping, and virtual mass, as well as experiments in a more realistic scenario involving contacts between the Fly-Crane and the environment.