Human Wrist Impedance Estimation Based on Impulse Response Induced by Snap-Through Buckling of Closed-Elastica.

A human joint impedance estimation method employing a wearable device using the snap-through buckling of closed-elastica has been proposed in our previous study and tested for the ankle joint. In the present study, the method is applied to the wrist impedance estimation scheme. Our method aims at the task-dependent scenarios. The wrist joint is involved in a variety of tasks, where the impedance plays a key role in physical interaction with environments. Because of the unique design and actuation concept, the proposed device does not disrupt the voluntary movements of the wrist and can be used in the estimation during the user's own motion planning. In this paper, to verify our method, the wrist impedance under the quasi-stationary condition is estimated, and the results are compared with the related works. Also, we discuss the profiles of the induced impulse responses and suggest an alternative estimation manner which does not require any force (torque) information.

Optimized Design of a Variable Viscosity Link for Robotic AFO.

Herein we present the development of a novel Ankle Foot Orthosis for gait support of people with foot-drop symptoms. The developed AFO uses an elastic link mechanism to brake the ankle joint during initial contact, thus mitigating foot-slap, and an integrated energy store-and-release mechanism to support toe lift in the swing phase, thus mitigating toe-drag. This paper presents improvements in the braking-holding power of the elastic link mechanism over its previous version, the torque-angle characteristics of the developed AFO with the renewed elastic link, and a pilot test with one person with foot-drop symptoms to verify the proposed functions of the developed AFO.

Tarsusmeter: Development of a wearable device for ankle joint impedance estimation.

We present the development and basic evaluation of a new wearable device for estimation of ankle joint impedance called Tarsusmeter. The device is intended for application with persons with locomotion disabilities to quantify the ankle joint impedance, especially in cases of spasticity where the joint's impedance is expected to differ significantly from healthy persons. The lack of a simple and light weight solution to provide objective evaluation of ankle joint impedance motivates the design criteria of this device to be as such. The target application is also to quantify variable stiffness actuator based orthosis in-vivo. Thus the form factor avoids overlap with custom shapes of such orthosis. The paper presents the mechanical design of the device, physical simulations to characterize the device-leg system, the used algorithm for impedance parameter estimation, and preliminary testing of the device.