1. FES Principles & Applications
Chung-huang Yu
Intelligent Mechatronic Assistive Device Lab Department of Physical Therapy and Assistive Technology
National Yang Ming University
Functional Electrical Stimulation

2. What is Electrical Stimulation (ES)?
Electrical Stimulation cause muscle contraction
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

3. Can we make ES functional?
Yes! (theoretically)
Why, in theory?
In body, very movement is actuated by muscle contraction.
Why, in practice?
Independence & Quality of Life
Maintain muscle volume
Improve physiological condition
Psychological Benefit
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

4. The terms Functional Electrical Stimulation (FES)
Functional Neuro-Muscular Electrical Stimulation (FNMES)
A technique that utilizes patterned electrical stimulation of neural tissue with the purpose of restoring or enhancing a lost or diminished function
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

5. What have been done?

6. What muscle type have been targeted?
skeletal
distal muscles
axial muscle (few - diaphragm)
smooth
bladder
bow
sexual organ
cardiac (pacemaker)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

7. What have been done on limb muscles?
upper-limb
hand grasping & release
hand orientation (wrist, elbow, shoulder)
whole upper-limb(s) -> not yet
lower limb
ankle (drop-foot - dorsiflexor)
knee (standing - quadriceps)
whole leg (standing, walking, cycling)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

8. Applications of Electrical Stimulation
Vision restoration
Epilepsy control
Cochlear implant
Tremor control
Cardiac pacing
Phrenic pacing
Control of reaching and grasping
Bowel emptying
Scoliosis control
Bladder empting and control of incontinence
Muscles exercise
Control of standing and walking
Wound healing
Spasticity reduction
Pain suppression
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

9. Some examples

10. The history of FES before 19th century
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

11. First registered FES work
Liberson, et al 1961
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

12. Parastep (Sigmedics Inc.)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

13. Parastep System Components
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

14. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

15. Freehand
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

16. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

17. Bionic Glove Restoration of hand function in C5-6 tetraplegia and CVA
Wrist movement must be preserved
3 channels self-adhesive electrodes over motor points
Conductive panels in the glove make contact electrodes
Control: wrist movements (tenodesis) sensed by a transducer
Wrist flexed > extensors tension > hand opens
Wrist extended > flexors tension > hand closes
Independent Don-Doff
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

18. Lower Limb: Odstock foot drop stimulator
One channel stimulator
Stimulation:
common peroneal nerve at head of fibula (TA) or
popliteal fossa (withdrawal reflex)
Heel switch trigger:
Heel off > stimulation ON
Heel on > stimulation OFF
Rise and fall stimulation envelope can be adjusted
Odstock 2 Channel Stimulator (O2CHS) for bilateral dropped foot
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

19. Handmaster (NESS, Israel)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

20. How can we make it functional?
The key aspects
Understand Human Sensory-Motor System
Residual capacities
Paralysis
Define what “Normal” functions to restore
How to meet the gap?
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

21. Human Sensory-Motor System
Planning, coordination (Cerebellum & Basal Ganglia)
Visual
Vestibular
Program Movement (Supplemental & Premotor) 
Motor Control
CNS
Muscles
Motor Neuron
Muscle Fibres
Spinal Cord
Corticospinal tract
Sensory Nerve
Sensory Feedback
Reach & Fine Movement (Motor Cortex) 
Posture & Balance (Braim Stem)
Skin: Touch, Pressure, Vibration 
Central Pattern Generator
Reflex (stretch, withdraw, inverse myotatic) 
Golgi: Force
Capsule: Extreme Angle
Spindle: Length, Velocity
Feed forward:
1. Synergistic
2. Antagonist
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

22. What are “normal” functions?
Is it necessary to be “normal”?
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

23. Types of Functions Functional Types Functional Requirements
Kinematically open
Kinematically closed
Functional Requirements
State change
Sit-to-stand, drop-foot
Constant regulation
Functional Joint Involved
Single Joint v.s. Multiple Joint
Single d.o.f. vs. Multiple d.o.f.
Single limb v.s. Multiple limbs.
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

24. How can we make ES functional?
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

25. Artificial Parts in an FES system
Stimulator
Controller
Sensors
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

26. Stimulator :The Physiological basics (1)?
Why electrical stimulation cause contraction?
What relations between muscle contraction and stimulation pattern?
What stimulation parameter?
Unipolar v.s. Bi-phasic
Element waveform?
Pulse width, height
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

27. Stimulator: Physiological basics (2)?
What stimulation parameter?
Single pulse, doublet, triplet, etc.
Frequency between elements
Fixed v.s. Sweep
Overall envelop
Muscle Response
threshold, saturation, in-between shape
short term effect (fatigue)
long term effect (muscle transfer, volume, etc.
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

28. Problems/Difficulties of Paralyzed Muscle (1)
Excitable?
Spasiticity
What is the response to stimulation?
Force
Stimulation
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

29. Problems / Difficulties of Paralyzed Muscle (2)
Individual motor unit (David Winter, 1990)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

30. Problems / Difficulties of Paralyzed Muscle (3)
Muscle Group
Selectivity
Surface electrode (rough, limited muscle sites, high working power, don-doff, etc.)
implant electrode (invasive, large number of electrodes, breakage)
recruitment sequence
size principle
F voluntary >> F implant >> F surface
F normal >> F paraplegic
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

31. Problems / Difficulties of Paralyzed Muscle (4)
Muscle Group
Biarticular Muscle
n-n & non-linear mapping between stimulation and response
Muscle Itself
Fatigue
Time-Varying
short-term
long-term (muscle type change)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

32. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

33. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

34. What do we want to control?
stationary position
withdraw
trajectories
accelerations
joint moment
joint stiffness
contact forces
Contact Slip reactions forces
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

35. Control Strategies Functionally automatically triggered
Open Drop-foot (foot switch)
Close Cycling (crank angle)
Functionally automatically regulated
Close CHRELMS
Artificially triggered
Open Handmaster
Close Demark (slip),
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

36. Difficulties in Sensor system
Why sensors in a FES system
Feedback control
Command controller
Artificial sensors
limited type
limited number
limited accuracy
don-doff
Natural sensors (Nerve cuff)
Demark & Canada Group
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

37. Three levels of concern
Command Source
Natural, subconscious
Artificial, Volitional
Command Type
Trigger
Regulation
Artificial control
Open-loop
Close-loop (position, trajectory, force, slip, COG, etc.)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

38. Object of an FES system: Real-time and Patient Driven
Real-time regulation
Sensors
position of joint
contact forces
Automatic Controller
what algorithm
Patient Driven
What capacities to use?
Command controller?
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

39. Application of FES systems
User capacity and paralysis
Target function analysis
Stimulation Patterns
System Modeling
Control Strategies
Other considerations
Safety, Economy, Cosmetic, Don-doff
etc.
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

40. Conclusions
FES systems as orthosis based on superficial stimulation still have low acceptance due to practical reasons:
long Don-Doff time, electrode positioning, braking parts, high EC/efficiency ratio, complicated to set and adjust -> Implants
After periods of FES training patients show carry over effects -> FES devices can be used as therapeutic tool combined with conventional physiotherapy
Functional Electrical Therapy (FET)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

41. Design Example: CHRELMS
Restoration of standing function to paraplegic by Functional Electrical Stimulation

42. FES standing/walking FES Normal Oxygen cost (ml/kg/m) 0.6 0.15
Speed (m/min) 60 85
Heart Rate (beats/min)
118 95
Use of upper Extremities
23% 0%
Cost (NT$500,000)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

43. Why FES walking at all? Psychological Effect
Simple forward progressing only
Short distance, i.e. fatigue quickly
high energy
still wheel chair dependent
high cost
Cardiovascular
bone loading
muscle exercise
Psychological Effect
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

44. Long term Goals: Good standing Good walking
Standing up: at will, trajectory, speed
Standing: longer, more comfortable, maneuvers
Sitting down: controlled descent
Good walking
long distance walk
walk in community (different surface)
different direction, step length, speed
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

45. But paraplegics do stand !
Supported Standing
Free-hand Standing
Example: vertical back standing up
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

46. Kinematics Analysis: controllable ?
d.o.f. =3
(not 6)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

47. Kinetic Analysis: Force Balance
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

48. Novel Concept: Deficit as control signals
Leg moment produced from Upper-body
Upper-body Activities
Control Signals (later)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

49. Proposed Control System
Deficits as error signals for artificial control
Advantages:
Patient driven
natural error signals for each joint each axis
no anthropometric data required
less demanding of sensors
handle reactions
joint positions
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

50. Theoretical Difficulties and Assumptions
Leg Joints in alignment -> maneuver
Mapping to desired muscle -> brain
Bi-articulator muscles
Muscle force change with length & velocity
Muscle fatigue
Static Indeterminacy -> (Discussed Later)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

51. System Setup
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

52. Software: controller
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

53. Software (LabVIEW)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

54. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

55. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

56. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

57. The subject Subject : TC (8 years after accident)
Gender: Male, Age: 49
Height: 1.85 m, Weight: 85 kg
Lesion: T6 complete
FES standing user for 7 years
Asymmetry: left thigh is 5 cm shorter
Crooked Spine
Remarried during our experiment period
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

58. Control Parameters Three channels each leg Static Indeterminacy
(i.e. gluteus, quadriceps, calf)
Static Indeterminacy
Conjugate Matrix
Control Parameter Tuning
I = 0.3, 1, 3
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

59. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

60. CHRELMS : Standing Up Consistent timing -> enable to learn
“Quick Knee Locking”
Able to half-stand
Asymmetry
Better Control but not smaller force
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

61. Standing maneuver Posture Switching- Prolong Standing Free-one hand
Swaying Forward
Swaying Backward
Swaying Leftward
Swaying Rightward
Free-one hand
Bending the knees
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

62. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

63. CHRELMS : Sitting down “Knee moment reduction” strategy
40.2% Moment due to Body Weight
89.5% Rate of Moment Change
“Release & Re-catch”
Prefer
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

64. Conclusion for the Controller
Deficits provide 3D signals but 2D seems enough
No preset mode/function
Perform different tasks with the same control parameter
Control of speed
Feel of lower limbs with ability to correct posture
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

65. Conclusion of the Study
Deficits: better understanding of paraplegic standing
Control system
simple & effective
user preference
potentially practical
Supported Standing should be considered by overall system level
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

66. The future of an FES system?
Advance of Electronic technique:
System-on-Chip
Micro Sensors
Micro Stimulator
Wireless System
Collaboration of Multi-disciplines
Engineers
Clinical members
Patients
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

67. FES clinic
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.