This paper proposes rigid-body modelling and identification procedures for long-reach dual-arm manipulators in a cable-suspended pendulum configuration. The proposed model relies on a virtually constrained open kinematic chain and lends itself to be simulated through the most commonly used robotic simulators without explicitly account for the cables constraints and flexibility. Moreover, a dynamic parameters identification procedure is devised to improve the simulation model fidelity and reduce the sim-to-real gap for controllers deployment. We show the capability of our model to handle different cable configurations and suspension mechanisms by customising it for two representative cable-suspended dual-arm manipulation systems: the LiCAS arms suspended by a drone and the CRANEbot system, featuring two Pilz arms suspended by a crane. The identified dynamic models are validated by comparing their evolution with data acquired from the real systems showing a high (between 91.3% to 99.4%) correlation of the response signals. In a comparison performed with baseline pendulum models, our model increases the simulation accuracy from 64.4% to 85.9%. The simulation environment and the related controllers are released as open-source code.

In aerial manipulators, the presence of cables between the aerial platform and the articulated system is beneficial to increase the distance between rotors' blades and the obstacles in the workspace and absorb unavoidable impacts arising during the interaction with the environment. However, cables also produce pendulum-like oscillatory behaviour due to dynamic coupling and to the effect of external forces when the robot navigates in free space through the environment. This paper presents a model-based control approach for the suppression of oscillations in cable-suspended dual-arm aerial manipulators. Contrary to many oscillation suppression techniques that act on the suspension platform, we exploit the dynamics of the articulated system to achieve the same goal. A linear controller is devised applying a partial feedback linearization technique for the unactuated variables of our system, i.e. the cables. Simulation and experimental tests are carried out using a quadrotor equipped with a cable-suspended dual-arm system to validate our proposed framework. With our control technique, drone-induced oscillations were reduced by up to 89%, with a settling time of 2.5 seconds.

Stabilising an inverted pendulum on a cart is a well-known control problem. This paper proposes the mechan-ical and control design for solving the oscillation problem of a variable-length flexible beam mounted on a mobile robot. The system under consideration is the robot PovRob, used at the European Organization for Nuclear Research (CERN) for visual and remote inspection tasks of particle accelerators. The flexible beam mounted on the robot houses cameras and sensors. The innovative aspect of the approach concerns the use of actuated masses mounted at the end of the rod, which induces an impulsive moment due to their inertia and angular acceleration. The modelling of the flexible rod has been suitably simplified in a lumped-parameter system, with dynamic parameters related to the rod's flexibility. A linearisation of the dynamic model allows a linear-quadratic control to stabilise the system. Experimental results support the identification and the validation of the dynamic model, while simulation results evaluate the performances of the designed control law.