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 k Hz and a noise reduction of 13 . 5 (in relation to no observers), at a sample rate and Pulse Width Modulation (PWM) frequency of 25 k Hz . Additionally, experiments verified a precise and high performing controller scheme both during impacts and at a variety of different virtual compliance characteristics.
Highlights
Compliance enables robotics to be used in contexts that include transitions of energy between a robot and fragile or unknown external elements—for instance, interactions with humans or walking on rugged terrain
Experimental Results: Active Impedance Controller Compared with Dynamic Impedance Model
The motor is driven in active impedance control mode with a fixed angle reference
Summary
Compliance enables robotics to be used in contexts that include transitions of energy between a robot and fragile or unknown external elements—for instance, interactions with humans or walking on rugged terrain This ability widens the scope of robotics which makes compliant robotics a fast advancing field. For this reason, the advancements in compliant robotics has made its footprint in areas where compliant interactions are required—for instance, legged robotics [1], rehabilitation robotics [2], wearable robotics [3], robotics surgery [4], robotic prostheses [5], soft robotics [6], collaborative robotics [7] and active vehicle suspension [8]
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