Martin Levesley

Systematic review of outcome measures used in the evaluation of robot-assisted upper limb exercise in stroke.

OBJECTIVE To classify and evaluate outcome measures currently used in robot-assisted exercise trials (RAET) in stroke, and to determine selection criteria for outcome measures in future trials. METHODS Outcome measures used in RAET were identified from MEDLINE, EMBASE, CINAHL, PubMed and PsychINFO databases. The scale items were categorized into International Classification of Functioning Disability and Health (ICF) domains. The psychometric properties of scale were rated using a standardized pro forma. RESULTS Thirty outcome measures were identified from 28 published RAET. Commonly used ICF body function scales were: Fugl-Meyer (FM) (24 studies), Modified Ashworth Scale (13 studies), Medical Research Council (11 studies), Kinematic measures (8 studies) and Motor Status Score (6 studies); ICF activity scale was Functional Independence Measure (FIMTM) (9 studies); ICF participation, personal and environmental factors scales were rarely used. Standard-ized rating identified that FM, kinematic measures, Action Research Arm Test, Wolf Motor Function Test, FIMTM, and ABILHAND have adequate measurement properties for use in RAET. CONCLUSION Some of the currently used outcome measures seem appropriate for RAET. The use of the ICF framework enables selection of an appropriate combination of outcome measures depending on patient characteristics, such as severity of weakness and chronicity of stroke impairments.

Coordination of active steering, driveline, and braking for integrated vehicle dynamics control:

Abstract An integrated vehicle dynamics control system which aims to improve vehicle handling and stability by coordinating active front steering (AFS) and dynamic stability control (DSC) subsystems is developed in this paper. The DSC subsystem includes driveline-based, brake-based, and driveline plus brake-based DSC subsystems. The influence of varying forward speed and lateral acceleration on the lateral vehicle dynamics is investigated first. The AFS controller, which is used to improve vehicle steerability in the low to mid-range lateral acceleration, and the DSC controller, which manages to maintain vehicle stability during extreme driving situations, are then designed by using the sliding mode control (SMC) technique and phase plane method respectively. Based on the two independently developed controllers, a rule-based integration scheme is proposed to optimize the overall vehicle performance by minimizing interactions between the two subsystems and extending functionalities of individual subsystems. Computer simulation results confirm the effectiveness of the proposed control system and the overall improvements in vehicle handling and stability.

A Control Strategy for Upper Limb Robotic Rehabilitation With a Dual Robot System

This paper describes the development and use of the cooperative control scheme used by the intelligent pneumatic arm movement (iPAM) system to deliver safe, therapeutic treatment of the upper limb during voluntary reaching exercises. A set of clinical and engineering requirements for the control scheme are identified and detailed, which entail controlled, coordinated movement of a dual robot system with respect to the human upper limb. This is achieved by using a 6-DOF model of the upper limb that forms the controllers coordinate system. An admittance control scheme is developed by using this coordinate system such that robotic assistance can be varied as appropriate. Key controller components are derived, including kinematic and force transformations between the upper limb model and the dual robot task space. The controller is tested using a computational simulation and with a stroke subject in the iPAM system. The results demonstrate that the control scheme can reliably coordinate the dual robots to assist upper limb movements. A discussion considers the ramifications of using the system in practice, including the effects of measurement errors and controller limitations. In conclusion, the iPAM system has been shown to be effective at delivering variable levels of assistance to the upper limb joints during therapeutic movements in a clinically appropriate manner.

Control of ionic polymer metal composites

Robotic devices are traditionally actuated by hydraulic systems or electric motors. However, with the desire to make robotic systems more compact and versatile, new actuator technologies are required. In this paper, the control of ionic polymer metal composite actuators is investigated from a practical perspective. The actuator characteristics are examined through the unblocked maximum displacement and blocked force output. An open-loop position control and closed-loop position proportional-integral-derivative (PID) control are then applied to a strip of actuators. Finally, the performance of the polymer is investigated when implementing an impedance controller (force/position control).

A new tool for assessing human movement: the Kinematic Assessment Tool.

The study of human behaviour ultimately requires the documentation of human movement. In some instances movements can be recorded through a simple button press on a computer input device. In other situations responses can be captured through questionnaire surveys. Nevertheless, there is a need within many neuroscience settings to capture how complex movements unfold over time (human kinematics). Current methods of measuring human kinematics range from accurate but multifarious laboratory configurations to portable but simplistic and time-consuming paper and pen methods. We describe a new system for recording the end-point of human movement that has the power of laboratory measures but the advantages of pen-and-paper tests: the Kinematic Assessment Tool. KAT provides a highly portable system capable of measuring human movement in configurable visual-spatial tasks. The usefulness of the system is shown in a study where 12 participants undertook a tracing and copying task using their preferred and non-preferred hand. The results show that it is possible to capture behaviour within complex tasks and quantify performance using objective measures automatically generated by the KAT system. The utility of these measures was indexed by our ability to distinguish the performance of the preferred and non-preferred hand using a single variable.

Vibration control of a flexible beam with integrated actuators and sensors

The use of system identification to determine linear Auto Regressive Moving Average eXogenous inputs (ARMAX) models for smart structures has been scarcely reported in the literature. However, these models can be used as a basis for a linear discrete-time controller design. This work presents a smart structure vibration control scheme developed using an ARMAX model of the structure and compares its performance to an empirically designed velocity feedback controller. The smart structure is comprised of piezoceramic (such as PZT) actuators and strain gauge sensors attached to a cantilever beam and interfaced to a PC, which provides the control software platform. System identification is carried out in three phases: data collection, model characterization and parameter estimation. Input-output data are collected by stimulating the piezoactuators with a bipolar square wave signal and monitoring the strain gauge response. The model is characterized with second-order plant dynamics and a least-squares estimation algorithm calculates the model parameters. The controller is designed using pole placement to achieve the desired closed-loop response. The ARMAX model is used to calculate the pole placement controllers by solution of the Diophantine equation for the prescribed closed-loop pole positions. Results show that the pole placement controller can match the performance of a velocity feedback controller and maintain this performance when the sampling rate is greatly reduced.

Integrated Active Steering and Variable Torque Distribution Control for Improving Vehicle Handling and Stability

This paper proposes an advanced control strategy to improve vehicle handling and directional stability by integrating either Active Front Steering (AFS) or Active Rear Steering (ARS) with Variable Torque Distribution (VTD) control. Both AFS and ARS serve as the steerability controller and are designed to achieve the improved yaw rate tracking in low to mid-range lateral acceleration using Sliding Mode Control (SMC); while VTD is used as the stability controller and employs differential driving torque between left and right wheels on the same axle to produce a relatively large stabilizing yaw moment when the vehicle states (sideslip angle and its angular velocity) exceed the reference stable region defined in the phase plane. Based on these stand-alone subsystems, an integrated control scheme which coordinates the control actions of both AFS/ARS and VTD is proposed. The functional difference between AFS and ARS when integrated with VTD is explained physically. The effect of the integrated control system on the vehicle handling characteristics and directional stability is studied through an open loop computer simulation of an eight degrees of freedom nonlinear vehicle model. Simulation results confirm the effectiveness of the proposed control system and the overall improvements in vehicle handling and directional stability.

Engaging children in healthcare technology design: developing rehabilitation technology for children with cerebral palsy

This paper presents a case study of users’ involvement in the design and evaluation of two devices for upper limb rehabilitation for children with cerebral palsy to use in their homes. The devices comprise a computer game and a force feedback interface, designed to stimulate children with cerebral palsy to undertake fun arm exercises that are beneficial in terms of improving overall functional use of their impaired arm. This device was developed for children using a combination of informal and formal user-centred design methods. The methods used include standard questionnaires, interviews, a modified peer tutoring process and a comparative method, and have been applied to the iterative design of both the hardware and software components of the rehabilitation systems. Thirty-seven non-disabled children and 15 children with cerebral palsy in the 5–12-year-old age group were involved in the evaluation, held at six local primary schools. Prototypes of the final design were used by 18 patients with cerebral palsy for approximately 4 weeks as a therapeutic intervention. To evaluate the designs, qualitative and questionnaire-based opinion was sought from these children, and their parents, at the end of the intervention. An evaluation of the methodologies employed is presented.

HOME-BASED COMPUTER-ASSISTED UPPER LIMB EXERCISE FOR YOUNG CHILDREN WITH CEREBRAL PALSY: A FEASIBILITY STUDY INVESTIGATING IMPACT ON MOTOR CONTROL AND FUNCTIONAL OUTCOME

OBJECTIVE We developed a home-based rehabilitation exercise system incorporating a powered joystick linked to a computer game, to enable children with arm paresis to participate in independent home exercise. We investigated the feasibility and impact of using the system in the home setting. METHODS Eighteen children with cerebral palsy (median age 7.5 years, age range 5-16 years) were recruited from local National Health Service and the exercise system was installed in their home for approximately 4 weeks. Baseline and post-intervention assessments were taken: Canadian Occupational Performance Measure (COPM); kinematic measurement of movement quality (indexed by duration and smoothness) measured using a motion tracking system when performing a standardized computer task. RESULTS The system was used for a median time of 75 min (interquartile range (IQR) 17-271), equating to 606 outward and 734 inward movements. Pre-COPM, (median 4.2); post-COPM (median 6.0); obs=34; z=3.62, p<0.01). Kinematic analysis of pre- and post-intervention movements on the standardized task showed decreased duration and increased smoothness. CONCLUSION Some improvements in self-reported function and quality of movement are observed. This pilot study suggests that the system could be used to augment home-based arm exercise in an engaging way for children with cerebral palsy, although a controlled clinical trial is required to establish clinical efficacy. The feasibility of this technology has been demonstrated.

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 discussion of future work