Title: Orthosis
1Definitions
Powered Locomotion Devices
- 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
2Orthosis
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 bearings - Walkabout Orthosis (Middleton 1997)
- Medially-mounted hinge joint linking two KAFO
- Self-Fitting Modular Orthosis (SFMO) (Popovic
1993) - Three modules to support patient, FES-aided gait
- Project has been abandoned
- Weight 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
3FES and Hybrid Walking Systems
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
4Advanced Gait Orthosis
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)
5Current Useful Technology
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, hasnt 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
6Powered Actuators
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)
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8Ankle
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
9Rehabilitative Devices
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 dramatically
- Lokomat robotic gait Orthosis (http//www.aut.ee.e
thz.ch/jezernik/research.msql) - Supported by a harness, robotic orthosis driven
by DC electric motors moves the patients legs - Currently performing gait-pattern adaptation
experiments
10Control Systems
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 bodys 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)
11Physiology
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 flexors - Passive 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)
12Power Sources
Powered Locomotion Devices
- Fuel Cells
- Methanol-powered alkaline fuel cell used to power
piezoceramic actuator (Leo 1999)
13Sensors
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 -