Controlling a multi-joint arm actuated by pneumatic muscles with quasi-DDP optimal control

Ganesh Kumar Hari Shankar Lal Das (1) , Bertrand Tondu (2, 1) , Florent Forget (1) , Jérôme Manhes (3) , Olivier Stasse (1) , Philippe Souères (1)

1 LAAS-GEPETTO - Équipe Mouvement des Systèmes Anthropomorphes
2 LESIA-INSA - Laboratoire d'Étude des Systèmes Informatiques et Automatiques
3 LAAS-I2C - Service Instrumentation Conception Caractérisation

Pneumatic actuators have inherent compliance and hence they are very interesting for applications involving interaction with environment or human. But controlling such kind of actuators is not trivial. The paper presents an implementation of iterative Linear Quadratic regulator (iLQR) based optimal control framework to control an anthropomorphic arm with each joint actuated by an agonist-antagonistic pair of Mckibben artificial muscles. The method is applied to positioning tasks and generation of explosive movements by maximizing the link speed. It is then compared to traditional control strategies to justify that optimal control is effective in controlling the position in highly non-linear pneumatic systems. Also the importance of varying compliance is highlighted by repeating the tasks at different compliance level. The algorithm validation is reported here by several simulations and hardware experiments in which the shoulder and elbow flexion are controlled simultaneously.

Mots clés: explosive motion; model; Pneumatic muscles; optimal control; Differential Dynamic Programming

Domaines: Robotique [cs.RO]; Automatique / Robotique

Ganesh Kumar Hari Shankar Lal Das, Bertrand Tondu, Florent Forget, Jérôme Manhes, Olivier Stasse, et al.. Controlling a multi-joint arm actuated by pneumatic muscles with quasi-DDP optimal control. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2016), Oct 2016, Daejon, South Korea. ⟨10.1109/IROS.2016.7759103⟩. ⟨hal-01432100⟩