FES Principles &
Applications
Chung-huang Yu
Intelligent Mechatronic Assistive Device Lab
Department of Physical Therapy and Assistive
Technology
National Yang Ming University
iMAD
What is Electrical Stimulation (ES)?

Electrical Stimulation cause muscle contraction
Electrical
Stimulation
Innervated
Muscle
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Msucle
Contraction
iMAD
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.
iMAD
The terms



iMAD
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.
What have been done?
iMAD
What muscle type have been
targeted?

skeletal



smooth

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distal muscles
axial muscle (few - diaphragm)
bladder
bow
sexual organ
cardiac (pacemaker)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
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.
iMAD
Applications of Electrical Stimulation
Vision restoration
Epilepsy control
iMAD
Cochlear implant
Tremor control
Cardiac pacing
Phrenic pacing
Control of reaching and
grasping
Scoliosis control
Bowel emptying
Bladder empting and
control of incontinence
Muscles exercise
Control of standing and
walking
Spasticity reduction
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Wound healing
Pain suppression
Some examples
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The history of FES before 19th
century

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
First registered FES work
Liberson, et al 1961
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Parastep (Sigmedics Inc.)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
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Parastep System
Components
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Freehand
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Bionic Glove

iMAD
Restoration of hand function in C5-6 tetraplegia and CVA

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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.
Lower Limb: Odstock foot drop
stimulator


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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.
iMAD
Handmaster (NESS, Israel)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
How can we make it functional?

The key aspects

Understand Human Sensory-Motor System

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

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.
iMAD
Human Sensory-Motor System
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Planning, coordination
(Cerebellum & Basal Ganglia)
CNS
Vestibular
Program Movement

Visual
(Supplemental & Premotor)
Reach & Fine Movement

(Motor Cortex)
Corticospinal
tract
Skin: Touch,
Pressure,
Vibration
Spinal Cord
Motor
Nerve
Neuron
Spindle: Length, Velocity

Sensory
Golgi: Force
Sensory Feedback
(Braim Stem)

Capsule: Extreme
Angle
Posture & Balance
Muscles
Central Pattern Generator
Reflex (stretch, withdraw,
inverse myotatic)
Feed forward:
1. Synergistic
2. Antagonist
Muscle Fibres
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Motor Control
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.
iMAD
Types of Functions

Functional Types
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Functional Requirements

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Kinematically open
Kinematically closed
State change
 Sit-to-stand, drop-foot
Constant regulation
 Sit-to-stand, drop-foot
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.
iMAD
How can we make ES functional?
Spinal Cord
Motion-feedback
Motion command
Stimulation
Artificial
Controller
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Sensors
iMAD
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.
iMAD
Stimulator :The Physiological
basics (1)?
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

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.
iMAD
Stimulator: Physiological basics
(2)?

What stimulation parameter?

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Single pulse, doublet, triplet, etc.
Frequency between elements
 Fixed v.s. Sweep
Overall envelop
Muscle Response
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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.
iMAD
Problems/Difficulties of
Paralyzed Muscle (1)


Force

Excitable?
Spasiticity
What is the response to stimulation?
Stimulation
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
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.
iMAD
Problems / Difficulties of
Paralyzed Muscle (3)
iMAD
Muscle Group

Selectivity

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recruitment sequence

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Surface electrode (rough, limited muscle sites, high working
power, don-doff, etc.)
implant electrode (invasive, large number of electrodes,
breakage)
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.
Problems / Difficulties of
Paralyzed Muscle (4)

Muscle Group



Biarticular Muscle
n-n & non-linear mapping between stimulation and
response
Muscle Itself

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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.
iMAD
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Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
What do we want to control?
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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.
iMAD
Control Strategies

Functionally automatically triggered
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Functionally automatically regulated
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Open Drop-foot (foot switch)
Close Cycling (crank angle)
Close CHRELMS
Artificially triggered


Open
Close
Handmaster
Demark (slip),
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Difficulties in Sensor system

Why sensors in a FES system
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Artificial sensors
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Feedback control
Command controller
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.
iMAD
Three levels of concern

Command Source
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Command Type
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Natural, subconscious
Artificial, Volitional
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.
iMAD
Object of an FES system: Realtime and Patient Driven

Real-time regulation
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Sensors
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Automatic Controller


position of joint
contact forces
what algorithm
Patient Driven

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What capacities to use?
Command controller?
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Application of FES systems
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User capacity and paralysis
Target function analysis
Stimulation Patterns
System Modeling
Control Strategies
Other considerations

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Safety, Economy, Cosmetic, Don-doff
etc.
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Conclusions

FES systems as orthosis based on superficial stimulation
still have low acceptance due to practical reasons:


iMAD
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.
Design Example:
CHRELMS
Restoration of standing function to
paraplegic by Functional Electrical
Stimulation
iMAD
FES standing/walking
iMAD
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.
Why FES walking at all?








Simple forward progressing only
Short distance, i.e. fatigue quickly
high energy
still wheel chair dependent
high cost
Cardiovascular
bone loading
muscle exercise
Psychological
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Effect
Long term Goals:

Good standing




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.
iMAD
But paraplegics do stand !
iMAD
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.
Kinematics Analysis:
controllable ?
iMAD

d.o.f. =3
(not 6)
Paralysed/Passive Joints
Intact/Active Joints
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Kinetic Analysis:
Force Balance
  
 
 B
h
 H H  H
M  M  h  F  h W
Fy
Mz
iMAD
Fx
h
WB



M Leg  M Arm  M Body
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.

Novel Concept: Deficit as control
signals

Leg moment produced from Upper-body

M ARM
 H H  H
M  h  F 
  H H  H 
  M  k  F   Deficit Leg
 H H  H
M  a  F 


 Upper-body Activities
 Control
Signals (later)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
Proposed Control System
iMAD


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.
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.
iMAD
System Setup
iMAD
y
z
x
Handle
Transducer
Position
Sensor
Stimulator
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Rack
Computer
Software: controller
iMAD
KP
Joint Model
e
(deficit input)
KI
1/s

1/Tt
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.

y
(Stimulation
Pulse Width)
Software (LabVIEW)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
iMAD
String Pot output (20)
Bridge output (12)
Sensor System
Sensor Interface
Handle Reactions (12)
& Joint Position (18)
iMAD
Man-machine interface
and result display
Coordinator
algorithm
Sagittal plane deficits (6)
User/ Experimenter
Regulator Algorithm
Stimulation Pulse Width (6)
Stimulator Interface
Instruction Packets via RS232
(6)
Stimulator
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Note: The number in bracket
indicates the channels or
variables being transferred
iMAD
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Disturb(k)
CHRELMS
Logger
ON
34.23
Ankle
Unknown
51.59
48.38
25
Knee
backlog 6
Hip
RAMP
Manual
Legs
20.00
1.5
1.3
L foot
All Joints
Fx
Calf,
Trunk
1.2
Fy
Quad.
Force
1.1
Mz 2
Glue.
Update Rate
1.0
Moment
RH Fx, Fy, & 10 Mz
6.00
0
-20
0
100
Right PW
Flush Rate
Hz
0.20
0.6
0.6
0.4
0.4
0.4
0.2
0.2
0.2
0.0
0.0
Up/Down
Up/Down
Up/Down
Auto
Auto
ON
ON
ON
-50
0.5
SwA SwPSwL SwR
0
100
Left PW
FrL FrR Oth.
OFF OFF OFF OFF OFF OFF OFF
500
Sampling Freq
400
PID
20.00
Kp, Ki, Kd, & Tt for ankle
0.1
0.0
0.6
Auto
0.2
-50.00
0.8
0
-25
0.3
-180.0
0.8
0.7
400
300
0.8
25
500
0
theta (y)
1.0
0.0
Hz
0.000
1.0
0.8
0.4
150
0.000
1.0
50
0.6
-40
Other
Level
LH Fx, Fy, & 10Mz
0.9
40
20
Mcon
iMAD
Hip
Level
0.000
COM2
Control Plane
Sagittal only
Control Joint
Knee
Level
Stimulation Hz COM port
1.4
R foot
Ankle
3.7 00000111
RAMP
1.6
sec
Sampling Freq.
20.00 Hz
Data window
OFF
Disturb(h)
150
0.0
0
theta (z)
-0.1
-0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
-90.0
0.7
100
-7.35
90.0
0.00
1.00
0.00
1.00
Kp, Ki, Kd, & Tt for knee
0.00
1.00
0.00
1.00
Kp, Ki, Kd, & Tt for hip
Program
Option
CHRELMS
Hardware
Setup
Hardware
Test
Antrho.
Data
Joint
Model
Controller
Parameter
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Replay
QUIT
Porg.
0.00
1.00
0.00
1.00
The subject
iMAD




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

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.
Control Parameters
iMAD

Three channels each leg
(i.e. gluteus, quadriceps, calf)

Static Indeterminacy

Conjugate Matrix
M con

0.5 0.5


0
.
5
0
.
5


M con
1 0


0
1


Control Parameter Tuning

I = 0.3, 1, 3
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
M con
0.75 0.25


0
.
25
0
.
75


iMAD
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
CHRELMS : Standing Up
iMAD





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.
Standing maneuver
iMAD

Posture Switching- Prolong Standing






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.
iMAD
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
CHRELMS : Sitting down
iMAD
57.63kg

“Knee moment reduction”
strategy
57.63kg
3 2 .0
44.02
M con
1 0


0
1


17.0 kg
17.0 kg
14.59 °
11
0. 0
7.19°
11
7 .0
°
°
CoM of HAT & Thigh
°
.0
82

“Release & Re-catch”
Prefer
°

3

40.2% Moment due to
Body Weight
89.5% Rate of Moment
Change
54.4
°
.0
90

CoM of HAT
10
CoM of Thigh
Joint
(A)
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
(B)
2.
0
°
Conclusion for the Controller





iMAD
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.
Conclusion of the Study
iMAD


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.
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.
iMAD
FES clinic
Patients
Clinical &
Biomedical
Research Team
Paralysis & Capacities
evaluation
iMAD
Muscle
Training
Evaluation
System
Custom made
FES system
New technologies
Technical
Bank
MEMS, Nerve Cuff
sensors & electrodes,
Mechatronic, etc.
Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,
National Yang Ming University.
Clinical Trial
Home use &
follow-up
Analysis &
Evaluation
Engineering
Knowledge
Medical
knowledge