Electro hydraulic actuation for a flexible robotic suit

Description

Lower limb exoskeleton technology is used for support and augmentation of human gait, as well as for complete gait restoration [1], but the available devices (and many devices in development) are relatively heavy and large, which degrades the “wearable” aspect of this type of wearable robotics. This is because exoskeletons, as the name implies, often have rigid structures spanning the entire lower limbs with actuators lined up with the biological joints. This paradigm disregards the fact that for almost all user groups the biological skeleton is still in good working condition, which makes the addition of a rigid structure unnecessary. A new approach is using flexible robotic suits, made of soft materials, like polymers and fibrous materials as can be seen in the work of Walsh [2] and a few others. Currently this type of “soft exosuits” is being developed for augmentation of human walking because the forces that can be transmitted comfortably to the wearer are insufficient for full restoration. In this research a new actuation principle is introduced, the inverted Muscle Skeleton approach, in which actuators work opposite biological muscles, by pushing between leg segments. Where most research pursues a biomimetic concept, this is the opposite. A flexible support structure carries the loads introduced by unwanted (shear) forces and keeps the actuators in place with respect to the leg. The actuators themselves should thus be mainly pushing between leg segments. An electro hydraulic actuator is being developed in this research that uses an electric motor to drive an input cylinder and with a hydraulic transmission line the motion and force are transferred to joint level where an output cylinder, supported by the flexible suit, drives the limb segment. Similar concepts were proposed by Buerger and Hogan [3] for high force haptic devices and by Bechet and Ohnishi for upper extremity rehabilitation [4]. Currently, experiments are carried out using off the shelf components to investigate the possibilities of using this electro hydraulic concept for the actuation of the knee joint.

Period	26 Jan 2017
Event title	6th Dutch Bio-Medical Engineering Conference 2017
Event type	Conference
Conference number	6
Location	Egmond aan Zee, Netherlands
Degree of Recognition	National