Development of a Testbed for Robotic Neuromuscular Controllers

Abstract

Abstract-Current control approaches to robotic legged locomotion rely on centralized planning and tracking or motion pattern matching. Central control is not available to robotic assistive devices that integrate with humans, and matching predefined patterns severely limits user dexterity. By contrast, biological systems show substantial legged dexterity even when their central nervous system is severed from their spinal cord, indicating that neuromuscular feedback controls can be harnessed to encode stability, adaptability, and maneuverability into legged systems. Here we present the initial steps to develop a robotic gait testbed that can implement and verify neuromuscular controls for robotic assistive devices. The initial stage consists of an antagonistically actuated two segment leg with a floating compliant joint. We detail its electromechanical design and low level, velocity-based torque control. Additionally, we present experiments that test the leg's performance during human-like high fidelity motions. The results show that the robot can track fast motions corresponding to 87% of the maximum performance limit of human muscle. The experiments also reveal limitations of our current implementation and we discuss solutions to overcoming them.

Robust swing leg placement under large disturbances

“…This step will enable indirect verification of the control by comparing predicted and observed muscle actuations in disturbed human swing phases. In addition, we plan to transfer the control to robotic legs in humanoid and rehabilitation robotics, for which we are currently developing a robotic leg testbed [28].…”

Recent Trends in Lower-Limb Robotic Rehabilitation Orthosis: Control Scheme and Strategy for Pneumatic Muscle Actuated Gait Trainers

“…Since then, numerous research studies have been implemented on the co-contraction of antagonistic muscle control, which have proven its ability to increase the stiffness and stability at the joints during volitional movements [75][76][77][78][79][80][81][82][83][84][85][86]. Based on these research studies, it was shown that by utilizing information from the antagonistic muscle co-contraction, muscular activation levels could be manipulated to control the movements of the joints.…”

“…Furthermore, analyses on the implementation of mono-and bi-articular actuators for achieving the high muscle moment required at the joints and better gait trajectories were also taken into consideration in real practice [91][92][93][94][95]. The study of antagonistic muscle co-contraction suggested that the control of the orthosis, which implements these mono-and bi-articular actuators, could achieve good joint stiffness and stability [75][76][77][78][79][80][81][82][83][84][85][86]. The design was biologically inspired (by human muscles), as it employed two compliant elements to manipulate the joints.…”

Compact nonlinear springs with user defined torque-deflection profiles for series elastic actuators

“…We target NLSs for SEAs in a neuromuscular gait testbed [21]. The NLSs for these SEAs must generate an exponentially stiffening torque with a zero torque at zero deflection, and a maximum torque τ max = 5Nm at ∆θ = ∆θ max .…”