Orthosis:

1
Definitions
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

2
Orthosis
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

3
FES 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

4
Advanced 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)

5
Current 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

6
Powered 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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8
Ankle
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

9
Rehabilitative 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

10
Control 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)

11
Physiology
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)

12
Power Sources
Powered Locomotion Devices

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

13
Sensors
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