Directional Singularity-Robust Torque Control for Gyroscopic Actuators

Abstract

Abstract-Gyroscopic actuation is appealing for wearable applications due to its ability to impart free moments on a body without exoskeletal structures on the joints. We recently proposed an unobtrusive balancing aid consisting of multiple parallelmounted control moment gyroscopes (CMGs) contained within a backpack-like orthopedic corset. Using conventional CMG control techniques, geometric singularities result in a number of performance issues, including either unintended oscillations or freezing of the gimbals at certain alignments, which are typically mitigated by the addition of redundant actuators or by allowing errors in the generated moment; however, because of the minimalistic design of the proposed device and focus on accurate moment tracking, a new methodology is required.In this paper, a control scheme is proposed for non-redundant CMG systems in which oscillations at saturated states are avoided and all remaining singularities are efficiently escaped by exploiting the system geometry; due to its use of classification-specific singularity proximity measures that account for the command moment orientation, it is named the directional singularity-robust (DSR) control law. The performance of this control law is assessed in both simulations and hardware testing. The proposed method is suitable for a wide range of CMG systems, including both balancing and aerospace applications.

Directional Singularity Escape and Avoidance for Single-Gimbal Control Moment Gyroscopes

“…We also propose the quantity of gimbal potential, to characterize the future ability to produce the reference moment, according to the alignment of each gimbal frame with respect to the reference direction. This generalizes and formalizes our previous method, where Berry et al outlined a control method for a collinear configuration of two gimbals [20].…”

“…The orthogonality index presented by Oh and Vadali [22] used in our previous study [20] also identified reference-aligned singularities (δ track = 0), but it did not unambiguously identify configurations that allowed good reference tracking (δ track = 1), making it less effective for the design of a steering law.…”

Controller synthesis and clinical exploration of wearable gyroscopic actuators to support human balance

“…Finally, arguments also exist for the suitability of certain types of controllers for this particular actuation concept. Due to a finite ability to exchange angular momentum (limited by geometric saturation), gyroscopic actuators are physically incapable of sustaining indefinite or prolonged support to overcome persistent postural bias 85 , but are rather better suited to providing dynamic assistance in response to rapid, transient motions, in which the angular momentum exchange is not monotonic but ideally varying over time such that the net exchange is small. Nevertheless, a posture-dependent controller could, in theory, be adapted to mitigate low-frequent biases, but the behaviour and perception of such a controller has not yet been studied.…”

Design and Implementation of Model Predictive Control for a Gyroscopic Inverted Pendulum

“…In aerospace and astronautic engineering, the gyroscopic effect is used in attitude guidance systems for spacecraft and satellites [2,3]. Lemus and Berry [4,5] applied it to develop a balance assistance device for humans.…”

“…Similarly, Jin et al [23] used an inverted pendulum to evaluate the efficiency of a stabilizing device before applying it to a bicycle. In studies to enhance human balance using gyroscopic effect, Lemus et al [4,5] conducted experiments on an inverted pendulum test bench instead of using an actual human.…”