Assist-as-needed path control for the PASCAL rehabilitation robot

Abstract

Adults and children with neurological disorders often require rehabilitation therapy to improve their arm motor functions. Complementary to conventional therapy, robotic therapy can be applied. Such robots should support arm movements while assisting only as much as needed to ensure an active participation of the patient. Different control strategies are known to provide arm support to the patient. The path controller is a strategy that helps the patient's arm to stay close to a given path while allowing for temporal and spatial freedom. In this paper, an assist-as-needed path controller is presented that is implemented in the end-effector-based robot PASCAL, which was designed for children with cerebral palsy. The new control approach is a combination of an existing path controller with additional speed restrictions to support, when the arm speed is too slow, and to resist, when the speed is too fast. Furthermore, a target position gain scheduling is introduced in order to reach a target position with a predefined precision as well as an adaptable direction-dependent supportive flux that supports along the path. These path control features were preliminarily tested with a healthy adult volunteer in different conditions. The presented controller covers the range from a completely passive user, who needs full support to an actively performed movement that needs no assistance. In close future, the controller is planned to be used to enable reaching in children as well as in adults and help to increase the intensity of the rehabilitation therapy by assisting the hand movement and by provoking an active participation.

Compliance adaptation of an intrinsically soft ankle rehabilitation robot driven by pneumatic muscles

“…The experiments have been performed at low speeds (when reproducing pure stiffness) in order to avoid the effect of inertial torques and forces. Then the robot compliance can be obtained from the estimated stiffness such as (11), in which the superscript x, y represent the parameters are in ankle dorsiflexion/plantarflexion, inversion/ eversion respectively.…”

“…The paradigm of compliance adaptation is important in rehabilitation field to provide a soft and safe environment for the patients. Actually there have been some extensive work such as patient-cooperative or assist-as-needed strategy [11,12] on Lokomat and LOPES [13,14]. However, most of existing work are applied to traditional rigid robots.…”

Learning a Predictive Model of Human Gait for the Control of a Lower-limb Exoskeleton

“…In contrast to methods that start from a model, such as [1], or methods that start from a force field and/or a "virtual tunnel" [2], this paper learns a model of the gait trajectories from a data set of example gait patterns during a learning phase. During an estimation and prediction phase, the joint trajectories are measured, remaining parameters are estimated and the future evolution of the joint trajectories is predicted.…”

Neurorehabilitation robot system for neurological patients using H-infinity impedance controller

“…In general, the rehabilitation robot assists and guides the patients arms, but it does not completely guide the arms in order to motivate the patient s active contribution to therapy [10,11]. For this reason, controllers have been studied to minimize the robot support and allow for temporal freedom while supporting the patient s arm to fulfill the desired task [12]. A solution to this point is a virtual tunnel.…”