Hybrid position and orientation tracking for a passive rehabilitation table-top robot.

This paper presents a real time hybrid 2D position and orientation tracking system developed for an upper limb rehabilitation robot. Designed to work on a table-top, the robot is to enable home-based upper-limb rehabilitative exercise for stroke patients. Estimates of the robot's position are computed by fusing data from two tracking systems, each utilizing a different sensor type: laser optical sensors and a webcam. Two laser optical sensors are mounted on the underside of the robot and track the relative motion of the robot with respect to the surface on which it is placed. The webcam is positioned directly above the workspace, mounted on a fixed stand, and tracks the robot's position with respect to a fixed coordinate system. The optical sensors sample the position data at a higher frequency than the webcam, and a position and orientation fusion scheme is proposed to fuse the data from the two tracking systems. The proposed fusion scheme is validated through an experimental set-up whereby the rehabilitation robot is moved by a humanoid robotic arm replicating previously recorded movements of a stroke patient. The results prove that the presented hybrid position tracking system can track the position and orientation with greater accuracy than the webcam or optical sensors alone. The results also confirm that the developed system is capable of tracking recovery trends during rehabilitation therapy.

Development of the iPAM MkII system and description of a randomized control trial with acute stroke patients.

iPAM (intelligent Pneumatic Arm Movement) is a dual robot system for providing assistive upper-limb exercise to people with arm weakness as a result of stroke. This paper highlights refinements made to the system in the development of iPAM MkII. The rationale of an on-going random control trial using the iPAM MkII is also presented.

A novel robotic system for quantifying arm kinematics and kinetics: description and evaluation in therapist-assisted passive arm movements post-stroke.

We developed a system for quantitatively measuring arm movement. Our approach provides a method to simultaneously capture upper limb kinetic and kinematic data during assisted passive arm movements. Data are analysed with respect to Cartesian and upper limb coordinate systems to obtain upper limb joint angles and torques. We undertook an evaluation of the system in participants with stroke to show the feasibility of this approach. During rehabilitation after stroke, one aspect of treatment includes the physiotherapist applying assistive forces to move the impaired arm of the patient who remains passive. There is a dearth of published data on the relationship between upper limb kinematics and the underlying forces (kinetics) in this mode of physiotherapy treatment. Such quantitative data are crucial in facilitating research into therapy practice, for example by measuring variation in practice and determining dosage. An experienced therapist prescribed passive movements tailored to the needs of 16 participants with stroke (41-81 years) with a range of anthropometric sizes and motor impairments. Our novel measurement tool recorded kinematic and kinetic data at 100 Hz for 6-11 movements per participant. The kinetic data show that the majority of movements fall within upper limits of 36.7 N in shoulder elevation, 22.4N in shoulder protraction, 4.6 Nm in shoulder abduction, 12.8 Nm in shoulder flexion, 2.4 Nm in shoulder rotation and 5.5 Nm in elbow flexion. These data show the potential of this system to better understand arm movement, in particular to objectively evaluate physical therapy treatments and support development of robotic devices to facilitate upper limb rehabilitation.

Effector force requirements to enable robotic systems to provide assisted exercise in people with upper limb impairment after stroke.

iPAM (intelligent Pneumatic Arm Movement) is a dual robotic system that aims to assist in the recovery of upper-limb movement in people with all severities of motor impairment after stroke. This paper presents effector force data gathered during the course of a pilot clinical study. It identifies the forces and workspace required to facilitate reach-retrieve exercises in a range of patients as part of rehabilitation treatments. These findings have been used in further refinements of the iPAM system.

Hardware-in-the-loop-simulation of the cardiovascular system, with assist device testing application.

This paper presents a technique for evaluating the performance of biomedical devices by combining physical (mechanical) testing with a numerical, computerised model of a biological system. This technique is developed for evaluation of a cardiac assist device prior to in vivo trials. This device will wrap around a failing heart and provide physical beating assistance (dynamic cardiac compression). In vitro, the device to be tested is placed around a simulator comprising a mechanical simulation of the beating ventricles. This hardware model interfaces with a computerised (software) model of the cardiovascular system. In real time the software model calculates the effect of the assistance on the cardiovascular system and controls the beating motion of the hardware heart simulator appropriately. The software model of the cardiovascular system can represent ventricles in various stages of heart failure, and/or hardened or congested blood vessels as required. The software displays physiological traces showing the cardiac output, depending on the natural function of the modelled heart together with the physical assist power provided. This system was used to evaluate the effectiveness of control techniques applied to the assist device. Experimental results are presented showing the efficacy of prototype assist on healthy and weakened hearts, and the effect of asynchronous assist.

An admittance control scheme for a robotic upper- limb stroke rehabilitation system.

This paper presents a control scheme for a dual robot upper-limb stroke rehabilitation system. A model of the human arm is outlined and used to formulate an admittance controller operating in human upper-limb joint space. Initial results are provided together with a discrussion of future work.