1. Orthosis: – a rigid, non-moving brace for weak or ineffective joints

or muscles

2. Prosthesis: – an artificial device to replace a missing part of the body

3. Functional Electrical Stimulation (FES): – Surface or surgically implanted current electrodes that

active groups of muscles

4. Gait: – Sequence of foot movements, walking

Definitions Powered Locomotion Devices

Comparison of hybrid walking systems for paraplegics: analysis of study methodology (Ijzerman 1999)

Moorong Medial Linkage Orthosis (Moorong MLO) (Middleton 1998)• Arcuate sliding link centered on the hip joints with roller bearingsWalkabout Orthosis (Middleton 1997)• Medially-mounted hinge joint linking two KAFOSelf-Fitting Modular Orthosis (SFMO) (Popovic 1993)• Three modules to support patient, FES-aided gait• Project has been abandonedWeight Bearing control (WBC) orthosis (Yano 1997)• Consists of: rigid frame for support, reciprocating hip joint; gas powered foot

device that varies sole thickness and push button sequential control system

Orthosis Powered Locomotion Devices

Advantages/Disadvantages• Effects of SCI, muscles used, training requirements, cost, spasticity reduction, reliability (Solomonow 1992)• Builds muscle mass and stroke volume (Merati et al 2000)• High energy expenditure

– Oxygen demand is above 50 % of the VO2 peak (Merati et al 2000)

• Slow ambulation– ~tenfold less than wheelchair (Merati et al 2000)

• Cosmesis and difficult to don/doff– 14 subjects, 3 using RGO, 4 using only FNS (Merati et al 2000)

Parastep System, Sigmedics Corp. (Frank Zeiss)• Only commercially available FES system

Cleveland FES Center and Case Western Reserve U (CWRU) (feswww.fes.cwru.edu)• 16-channel FES with implanted electrodes and a walker. Surface are impractical for everyday use (Kobetic 1999)

– Using a switch initiated gait, paraplegic could stand for 8 minutes and walk for 20 meters

• Isocentric reciprocal gait orthosis (ISO-RGO) vs. FNS or orthosis only (Marsolais 2000)– Slower walking (.2 m/s) and increased energy cost (.5 Kcal/m)– Better stability and walking distance

Self-Fitting Modular Orthosis (SFMO) (Popovic 1993)• Separate knee, hip and ankle modules placed on a pair of jeans• Maximal average speed = 0.4 m/s where upper body support was 60 % of total• Approximately same oxygen uptake as RGO+FES• Has abandoned project

Controlled Brake Orthosis (Goldfarb and Durfee 1994)• Uses magnetic particle brakes to dissipate excessive torque• Dr. Durfee (U. of Minnesota) is looking for second round of funding

FES and Hybrid Walking Systems Powered Locomotion Devices

Hydraulic system (Seireg et al 1981)• Five degrees of freedom (2 at hip, 1 at knee, 2 at ankle)

• Good and simple design and analysis

• Bulky and unusable because of the current state of technology

Powered Gait Orthosis (PGO) – 4 bar linkage and CAM system (Ruthenberg et al 1997)• One degree of freedom run by a linear DC motor

• More of a research tool than a a practical means for paraplegic gait

• Battery pack and control system can be fastened to the back of the corset

• Mechanized hip and knee with cam-modulated linkage for knee function

• Peak power usage is the same as human walking

History of active exoskeletons (Vukobratovic 1990)• Hydraulic powered exoskeleton (1968)

• Two pneumatically driven exoskeletons (1970-1973)

• Electrical exoskeleton using servoelectric D.C. drives (1974)

• Compact, computer controlled active suit for “dysthrophics” (1980)

Dynamic Knee Brace System (DKBS) (Irby 1999)• Allows flexion during swing, restricts it during stance

• Footswitches are inputs, finite state controlled linear solenoid to control knee

Intelligent Orthosis (IO) (Suga et al 1998) • A KAFO that controls the amount of resistance to joint movement using rotary encoder and heel switch

• All subjects had a weakened quadriceps

Advanced Gait Orthosis Powered Locomotion Devices

1. Biped robots

• MIT leg lab “spring flamingo” (Pratt 1999)– Have a 6 degree of freedom biped robot walking on unknown sloped terrain

– Applied a neural network mechanism for a stable adaptive control

• Anthropomorphic biped robot BIP2000 (Espiau 2000)– Bipedal robot with 15 active joints include hip

– Can walk and turn in unknown sloped terrain

2. Feedback controllers– Sensory nerve signal to predict EMG signal for FES (Strange 1999)

– EMG control of actuators (Fukuda 1998)

3. Shape memory alloy (SMA) actuated arm and hand prosthesis (Mavroidis 1999)– Early stages of development, hasn’t been applied to locomotion

– Advantages: small size, high force to weight ratio, low cost

– Disadvantages: low strain, limited life cycle, non-linear effects, low bandwidth and efficiency

4. DARPA exoskeleton project (http://www.darpa.mil/dso/thrust/md/exoskeletons/program.html)

– This program will be used to develop technologies, such as actively controlled exoskeletons, to enable a soldier to handle more fire-power, wear more ballistic protection, and carry more ammunition and supplies

Current Useful Technology Powered Locomotion Devices

1. Shape Memory Alloys (SMA) Actuators– Frequency of actuation: 5 Hz w/o cooling; 15-20 Hz w/ liquid coolant– Low efficiency and cyclic abilities due to heat transfer– Not a feasible option for actuation

2. Pneumatic Muscle Actuators (PMA) (Caldwell 1998) & McKibben Artificial Muscle (Tondu 2000)

– Highly flexible, soft actuators– Strains of 30 %– Max. bandwidth for antagonistic pairs is 5 Hz– Active stress is 3 MPa – Has built orthotic devices out of and controllers for MIMO

3. Series Elastic Actuators (Pratt 1995)– Advantages: greater shock tolerance, lower reflected inertia, more accurate and stable force

control, less inadvertent damage to environment and capacity for energy storage– Disadvantages: low zero motion force bandwidth

4. Electroactive Polymers (Dr. John Madden, MIT Newman Lab)– Safe stress is 3 MPa, Specific power of 39 W/kg– Can survive 100,000 cycles at 2 % (work being done on fatigue characteristics)– 3 % Efficiency (could be as high as 20% if can recover stored electrical energy)– JPL's NDEAA Technologies Group (ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/EAP-web.htm)

Powered Actuators Powered Locomotion Devices

The Odstock Dropped Foot Stimulator (http://www.mpbe-sdh.demon.co.uk/fes.htm)• single channel FES that corrects dropped foot by stimulating the common peroneal nerve using

self adhesive skin surface electrodes placed on the side of the leg• Clinical study finished in 1995, 178 patients have been treated 25 have stopped• Cost is for 1 year is £830

Peroneal Nerve Stimulator (PNS) (Voigt 2000)• Creates an exaggerated dorsiflexion with excessive subtalar eversion• Could not find any excessive and potential harmful mechanical loads

Spring-Type AFO (Brunner 1998)• Stiff AFO with a 10-15o cut at the ankle• Showed that allowing the ankle joint to move facilitates normal gait

Dorsiflexion Assist Controlled by Spring AFO (DACS-AFO) (Hachisuka 1998)• Generates a dorsiflexion assist moment during plantar flexion and no

moment during dorsiflexion using a spring located at the calf• The initial dorsiflexion angle of the ankle joint is adjustable and three springs

with different moments are available.• None of the five subjects that they tested said that they preferred the DACS-

AFO

Spring-assisted dorsiflexion AFO (Lehmann 1986)• Effective in ground clearance, but not stiff enough for lengthening contraction after heel-strike

Ankle Powered Locomotion Devices

Walking Assistance and Rehabilitation Device (WARD) (Gazzani 1999)

• Treadmill with Body Weight Unloading apparatus

• Six of seven patients improved score on ambulation scale

Modified crank and rocker mechanized gait trainer (Hesse 2000)

• Simulates gait, supports subjects and controls their center of mass

• Two subjects improved dramaticallyLokomat robotic gait Orthosis (http://www.aut.ee.ethz.ch/~jezernik/research.msql)• Supported by a harness, robotic orthosis driven by DC electric motors moves the patient’s legs• Currently performing gait-pattern adaptation experiments

Rehabilitative Devices Powered Locomotion Devices

Bipedal walking robot using Cerebellar Model Articulation Controller (CMAC) (Hu 1999)

• Adaptive CMAC neural network control is stable and accounts for disturbances

Modified crank and rocker mechanized gait trainer (Hesse 2000)

• Simulates gait, supports subjects and controls their center of mass

• Two subjects improved dramatically

Comparison of machine learning (ML) techniques (Jonic 1999)

• Adaptive network based fuzzy inference system (ANFIS)

• Minimal number of and most comprehensible rules

• Entropy minimizing inductive learning (IL) and radial basis function (RBF) neural network

• Best generalization

Finite state control of FES (Sweeney 2000)

• Systems receive feedback from sensors on body or from the body’s own natural sensors

Neural network controlled FES maintains high accuracy with two force sensors under foot (Tong 1999)

Fuzzy Walking Pattern (FWP) controller for SMA biped robot (Tu 1998)

Control Systems Powered Locomotion Devices

Paraplegic Standing (Matjacic 1998)

• Paraplegic standing with ankle stiffness of 8 Nm/o

• Models the torque around the ankle for a two-link inverted pendulum

• Did not look at lateral stability

Feedback control of unsupported paraplegic standing (Hunt 1999)• inputs are ankle torques and body inclination and outputs a FES signal to the

plantar flexorsPassive stiffness increases in paretic patients (Lamontagne 2000)

• Use stiffness as an energy storage for toe-off

• Proves that orthotic should help

• Ankle moment is linear with angle

Biomechanics of the Foot (Mann 1997)

Lower Limb Orthoses (Michael 1997)

Normal and Pathological Gait (Perry 1997)

Improved Muscle-reflex actuator for large-scale neuromuscular models (Winters 1995)

Model of the intrinsic and reflex contributions to ankle stiffness dynamics (Kearney)

Lower joint powers during stair climbing at different slopes (Riener et al 1999)

Physiology Powered Locomotion Devices

Fuel Cells

• Methanol-powered alkaline fuel cell used to power piezoceramic actuator (Leo 1999)

Power Sources Powered Locomotion Devices

Overview (Veltink 1999)

• Describes body-mounted sensors for muscle activation, force and movement

Using the natural sensors of subject as feedback signals to control FES (Haugland 1999)

• Replaced heel switch with implanted electrode for a peroneal stimulator

• Provided a hand grasp FES system with sensory feedback from fingertips

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Sensors Powered Locomotion Devices