class+12 (1).ppt
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TRANSCRIPT
Wednesday, November 18
• Orthoses : passive, powered• Hand movers• Ankle rehabilitators• Walking Lab
AFO adjustable for PF correction
DAAJ
Knee stability in an AFO
Standard MetalAFO: 375 in. lbs.
60% reductionIn Quad torque
Types of ankle bracing
More types
Powered Gait OrthosesHydraulic Actuation (Seireg et al 1981)• Five DOFs (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
• linear DC motor (Ruthenberg et al 1997) 4 bar linkage and CAM system• One DOF run by a Battery pack and control system • Mechanized hip and knee with cam-modulated linkage for knee function• Peak power usage ~ human walking• May be a practical means for paraplegic gait?
Powered ankle
• http://www.ossur.com/prosthetics
• http://www.ossur.com/bionictechnology/propriofoot
Functional Electrical Stimulation
• Can re-animate paralyzed muscles• External or internal electrodes• User triggered with switches. How else?• Most are open loop, but reflexes not
necessary for rhythmic motions. • Problem because cutaneous nerves are
stimulated first. Also larger motoneurons have lower threshold.
Functional Arm Orthoses
See also pp. 319 yellow
FES
Correcting muscle Atrophy
• Atrophy is the loss of muscle mass
• Present methods for preventing atrophy– Myoplasty
– Myodesis
– Implantable devices
Continuation of Class 5 on muscles
Muscle Characteristics
• Irritability– ability to respond to a stimulus
• Conductivity– propagate a stimulus
• Contractility– ability to modify length (shorten)
• Adaptability– ability to change structure
Time scale(All or none)
Elasticity
Muscle adaptation
• Two types : fast and slow• or twitch and tonic• white and red• Interchangeable
• Fibers extend full length of • muscle
Bion (Loeb et al.) • BIONs are individually
addressable, single channel stimulators that can be injected in or near muscles and nerves to treat paralysis, spasticity and other neurological dysfunctions. BIONs receive power and digital commands from an externally worn RF transmitter coil and generate precisely timed, current-regulated electrical stimulus pulses.
System for functional electrical stimulation
Prototypes of Bion2 have sensing capability for acceleration, & proximity.
Non-polarizable
High surface area
Galvani discovery of electricity
The BION™
• A system using BIONs consists of a personal computer, a transduction coil, and the associated implantable BIONs
• A computer can control up to 256 BIONs at a time
• What are present uses for the BION?• 560 KHz carrier, need 20 Hz stim• E Storage in body’s capacitance
Flow Charts of BION OperationImplantable Device
Comparison of Std. FES and the BION™ System
• Battery Powered• Switch to turn power on or
off
• Not battery powered• External computer
controls BION™
activation
Similarities
Differences
• Both use magnetic fields to activate the implants• Both are used to stimulate muscle contraction
Implantable FES
BION™
Idea for Bion in Preventing Atrophy
• Currently bions are controlled by an outside source, the personal trainer
• Goal would be to have the body control the computer that controls the bions.
• The trick would be creating a component that would be able to sense/detect an action potential along the severed nerve and use that signal to activate the bions.
Some Applications• Shoulder Subluxation
• Hand assist devices
• Without a glove• May be difficult for a
paralytic hand to don.
Ankle Exercisor
• Drop foot is due to central paralysis; injury, I.e. PTT; osteoarthritis; Charcot foot.
Range of Motion Ankle Rehabilitator
• An inverted joystick interface to computer.
Rehabilitation Engineering
Linking virtual to real world