L25 Exoskeleton Device Design Flashcards
Exoskeleton Device Design Considerations
- Application: Walking or Running, Stairs (Lower) and pick/place, other (Upper)
- Augmenting or Assistive
- Degrees of Freedom
- Range of Motion
- Torque Velocity
- Frequency
- Actuation: Active/PassiveDC servo motors, elastic and transmission, hydraulics, cable/pulley system
- Weight/Inertia
- Interface: how does it connect to the human
- Human Machine Interface
- Adults or Children
Exoskeleton Device Design Considerations
Actuation
* Electric
* Geared motor-cable- pulley system
* DC servo motors, tendons
* Hydraulic
* Pneumatic
Human Machine Interface
* Mirroring function of other side
* Buttons, switches
* EMG recognition
* Automated
* Weight shifting
* Force sensors
Hocoma Lokomat
- Driven gait orthosis
- Used to treat individuals with neurological diseases or injuries such as stroke, SCI, brain injury, MS and cerebral palsy
Rehabilitation and Health Benefits
of Exoskeleton Devices
Functional gain and improved fitness is evidenced by:
* Greater heart rate and increased oxygen uptake (VO2)
* Significant increase in joint range of motion specifically ankle dorsi-flexion and hip
extension
* Multi-system impact, meaning many of our bodily systems are stimulated: motor, sensory, nervous, brain, cardiac, and digestive
* Increased bladder and bowel efficiency and regularity with a decrease in urinary tract
infections
* Increased blood flow and circulation in the lower extremities
* Reduction in edema or fluid retention
* Decreased spasticity
* Improved mental acuity and alertness
* Improved sleep
* Decrease in neuropathic pain
* Improved self-reported quality of life, motivation to exercise, and overall health and wellness
Electrical Stimulation
- Applying low levels of electrical currents to stimulate a physiological response
- Relaxation of spasticity, controlled muscle contractions, increase muscle fiber recruitment, circulatory stimulation
- Pain management, control of seizures, controlled stimulation of muscles to return function, SCI or peripheral nerve damage, cardiac pacemakers, tissue
repair, reduction of edema, increase functional activity, stimulation of de-
enervated muscles
Type of Electrodes: Transcutaneous
Attached to surface of the skin
Percutaneous
Placed below the skin (needle) or implanted
Subcutaneous
Implantable receiver/stimulator, an externally worn transmitter and implanted electrodes
Effects of Muscle Contraction
- Increase muscle metabolism
- Increase oxygen demand by muscles
- Increase output of waste product & metabolic (carbon dioxide, lactic acid)
- Dilation of capillaries and arterioles
- Increase blood flow
- Increase local temperature
- Increase venous and lymphatic drainage
- Changes in muscle structure (fast twitch to slow twitch)
- Increase joint range of motion
Potential Benefits of Functional Electrical Stimulation
- Reduced spasticity
- Carryover effect
- Reduced effort in walking
- Slowing of osteoporosis and/or bone mineral loss
- Reduced swelling, formation of blood clots
- Improved cardiovascular health with increased walking,
walking speed - Improve proprioception
- Reduce frequency of pressure sores and urinary tract
infections
Foot drop
- Cuff with electrodes and a foot switch
- Stimulate peroneal nerve and TA muscle; lift foot during swing
phase
AFOs (Ankle Foot Orthosis):
* Pros: improve functional ambulation, low tech, inexpensive,
simple to don/doff
* Cons: cumbersome in weight, size, poor cosmesis,
uncomfortable, limit ankle mobility
FES:
* Pros: cosmesis, variable models (switch off dorsiflexion);
reduce self awareness during gait; greater perceived safety
and independence, greater ankle free movement
* Cons: skin irritation due to electrodes, difficulty donning,
unsuitable near water, and for some travel, expensive
Parastep 1 System
- Microcomputer controlled
neuromuscular stimulation unit - A battery activated power pack with
re-charger - A unit for pre-testing main system
operation and electrode cables - Surface applied skin electrodes
- Power and electrode cables
- A control and stability walker with
finder activated control switches
Some Challenges of FES:
Lower Limb
- Cumbersome in design
- Unable to provide any long term/permanent solution to the problem (e.g. Dystonia)
- Inefficiency of energy required to move the lower limb
- Lack of empirical evidence which suggests the benefits of FES compared to other treatments
- Lack of clinical testing supporting a better quality of life for the patient when using FES in
comparison to other treatments - Lack of supporting evidence towards the reduced cost of care when using FES
