for their participation in the valuable discussions at various stages of the work. This work has been supported by a startup grant on Bio-inspired Robotics from Vidyasirimedhi Institute of Science & Technology (VISTEC) (P.M., project PI). We also thank FIGO company for participating in technical discussions, and PTT Exploration and Production Public Co. Ltd., for taking part in general discussions and providing the industrial pipes for robot testing.

No abstract

Dynamic compliant robotics is a fast growing field because of its ability to widen the scope of robotics. The reason for this is that compliant mechanisms may ensure safe/compliant interactions between a robot and an external element-for instance, a human operator. Active impedance control may widen the scope even further in relation to passive elements, but it requires high-bandwidth robust torque and active impedance control which induces high-noise issues even if high-end sensors are used. To address these issues, a complete controller design scheme, including Field-Oriented Control (FOC) of a Brushless Direct Current (BLDC) motor, is proposed. In this paper, controller designs for controlling the virtual impedance, motor torque and field are proposed which enables high-bandwidth robust control. Additionally, a novel speed and angle observer is proposed that aims to reduce noise arising in the angle sensor (typically a 12-bit magnetic encoder) and a Kalman/Luenberger based torque observer is proposed that aims to reduce noise arising in the phase current sensors. Through experimental tests, the combination of the controller designs and observers facilitated a closed-loop torque bandwidth of 2.6 kHz and a noise reduction of 13.5 dB (in relation to no observers), at a sample rate and Pulse Width Modulation (PWM) frequency of 25 kHz. Additionally, experiments verified a precise and high performing controller scheme both during impacts and at a variety of different virtual compliance characteristics.