Teleoperation of AZIMUT-3, an omnidirectional non-holonomic platform with steerable wheels

AZIMUT-3 is an omnidirectional non-holonomic (or pseudo-omnidirectional) robotic platform intended for safe human-robot interaction. In its wheeled configuration, shown in Fig. 1, AZIMUT-3 uses eight actuators for locomotion: four for propulsion and four for steering the wheels, which can rotate 180 degrees around their steering axis. Propulsion is done using standard DC brushless motors (Bayside K064050-3Y) with optical encoders (US Digital E4-300-157-HUB, 0.3 deg of resolution), capable of reaching 1.47 m/s. The platform uses steerable wheels motorized using differential elastic actuators (DEA), which provide compliance, safety and torque control capabilities. AZIMUT-3's hardware architecture consists of distributed modules for sensing and low-level control, communicating with each other through a 1 Mbps CAN bus. A Mini-ITX computer equipped with a 2.0 GHz Core 2 duo processor running Linux with real-time patches (RT-PREEMPT) is used on-board for high-level control modules. Nickel-metal hydride batteries provide power to the platform for up to 3 hours of autonomy. A passive vertical suspension mechanism (Rosta springs) is used to connect the wheels to AZIMUT-3's chassis, allowing them to keep contact with the ground on uneven surfaces. The platform has a 34 kg payload capacity and weights 35 kg.