Background: The ability to characterise balance capacity through clinical assessment procedures is often limited by a focus on movement tasks substantially more predictable than those experienced in the real world. Consequently, assessment protocols may not sufficiently elicit and characterise the full range of sensory, cognitive and physical challenges present in daily life. Methods: A task-specific procedure for assessing balance control during gait via a treadmill-based augmented-reality environment called the ‘Benchmarking System for Assessing Balance’ (BeStABle) is proposed. The apparatus utilises unpredictable visual cues that prescribe discrete changes to foot placement patterns, requiring rapid stimulus perception, decision-making, and modification of body dynamics, followed by compensatory corrections to return to steady gait. This is representative of a wide variety of situations in community living and many reported circumstances of real-world falls. This assessment procedure is demonstrated with a case study comparing three high-functioning users of transtibial (below-knee) prostheses with a group of 19 able-bodied persons. Results: The BeStABle successfully discriminates the prosthesis users from the normative group in multiple outcomes, and most prominently when participants are cued to narrow their steps. The finding that certain gait adaptations are not realisable by the prosthesis users may help to refine future protocols for assessing gait and balance impairment with the BeStABle. Conclusion: The BeStABle treadmill-based augmented-reality environment enables the repeatable and objective assessment of gait adaptations through a process that is safe for subjects and efficient for clinicians. ... Read more

Series Elastic Actuation decouples actuator inertia from the interaction ports and is thus advantageous for force-controlled devices. Parallel or even passive compliance can fulfill a complementary role by compensating for gravitational or periodic inertial forces or by providing passive guidance. Here, these concepts are combined in an underactuated six degree of freedom (DoF) compliant manipulator with one actuated DoF. The mechanism comprises a spring assembly in which each spring serves as an actuation element and simultaneously provides passive compliance in the unactuated DoF. The device is designed to assist weight shifting via controlled lateral forces on a human pelvis during treadmill walking and its eigenfrequencies are tuned to align with normal gait. Six-DoF force and torque sensing are realized via a model of the spring deformation characteristics in combination with low-cost inertial and optical sensors. Experimental evaluation demonstrates that the system can effectively follow physiological weight shifting with low interaction forces and also has little impact on remaining pelvis motions. ... Read more