FES Principles & Applications

(1)

iMAD

FES Principles &

Applications

Chung-huang Yu

Intelligent Mechatronic Assistive Device Lab Department of Physical Therapy and Assistive Technology

National Yang Ming University

(2)

What is Electrical Stimulation (ES)?

iMAD



Electrical Stimulation cause muscle contraction

Electrical Stimulation

Innervated Muscle

Msucle

Contraction

(3)

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) ,

Can we make ES functional?

iMAD



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

(4)

The terms

iMAD



Functional Electrical Stimulation (FES)



Functional Neuro-Muscular Electrical Stimulation (FN MES)



A technique that utilizes patterned electrical stimulatio

n of neural tissue with the purpose of restoring or enha

ncing a lost or diminished function

(5)

iMAD

What have been done?

(6)

iMAD

What muscle type have been targeted?



skeletal



distal muscles



axial muscle (few - diaphragm)



smooth



bladder



bow



sexual organ



cardiac (pacemaker)

(7)

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)

(8)

iMAD

Epilepsy control Tremor control

Phrenic pacing

Control of reaching and grasping

Scoliosis control Muscles exercise Control of standing and walking

Vision restoration Cochlear implant

Cardiac pacing

Bowel emptying

Bladder empting and control of incontinence

Wound healing

Applications of Electrical Stimulation

(9)

iMAD

Some examples

(10)

iMAD



The history of FES before 19th

century

(11)

iMAD

Liberson, et al 1961

First registered FES work

(12)

Parastep (Sigmedics Inc.)

iMAD

(13)

iMAD

Parastep System C

omponents

(14)

iMAD

(15)

iMAD

Freehand

(16)

iMAD

(17)

iMAD



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

Bionic Glove

(18)

iMAD

Lower Limb: Odstock foot drop st imulator

 One channel stimulator

 Stimulation:

 common peroneal nerve at head of fibul a (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) f or bilateral dropped foot

(19)

Handmaster (NESS, Israel)

iMAD

(20)

How can we make it functional?

iMAD



The key aspects



Understand Human Sensory-Motor System

 Residual capacities

 Paralysis



Define what “Normal” functions to restore



How to meet the gap?

(21)

iMAD

Human Sensory-Motor System

Visual Vestibular

Skin: Touch, Pressure, Vibration

Posture & Balance

(Braim Stem)

Reach & Fine Movement

(Motor Cortex)

Program Movement

(Supplemental & Premotor)

Planning, coordination

(Cerebellum & Basal Ganglia)

Golgi: Force

Capsule: Extreme Angle

Spindle: Length, Velocity

Feed forward:

1. Synergistic 2. Antagonist

Reflex (stretch, withdraw, in verse myotatic)

Central Pattern Generator

Motor Control

CNS

Muscles

Motor Neuron

Muscle Fibres

Spinal Cord

Corticospinal t ract

Sensory Nerve

Sensory Feedback



(22)

What are “normal” functions?

iMAD



Is it necessary to be “normal”?

(23)

Types of Functions

iMAD



Functional Types

 Kinematically open

 Kinematically closed



Functional Requirements

 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.

(24)

How can we make ES functional?

iMAD

(25)

Artificial Parts in an FES system

iMAD



Stimulator



Controller



Sensors

(26)

iMAD

Stimulator :The Physiological basics (1)?



Why electrical stimulation cause contraction?



What relations between muscle contraction and s timulation pattern?



What stimulation parameter?



Unipolar v.s. Bi-phasic



Element waveform?



Pulse width, height

(27)

iMAD

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.

(28)

iMAD

Problems/Difficulties of Paralyzed Muscle (1)



Excitable?



Spasiticity



What is the response to stimulation?

F or ce

(29)

iMAD

Problems / Difficulties of Paralyzed Muscle (2)



Individual motor unit (David Winter, 1990)

(30)

iMAD

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

(31)

iMAD

Problems / Difficulties of Paralyzed Muscle (4)



Muscle Group



Biarticular Muscle



n-n & non-linear mapping between stimulation and res ponse



Muscle Itself



Fatigue



Time-Varying

 short-term

 long-term (muscle type change)

(32)

iMAD

(33)

iMAD

(34)

What do we want to control?

iMAD



stationary position



withdraw



trajectories



accelerations



joint moment



joint stiffness



contact forces

(35)

Control Strategies

iMAD



Functionally automatically triggered



Open Drop-foot (foot switch)



Close Cycling (crank angle)



Functionally automatically regulated



Close CHRELMS



Artificially triggered



Open Handmaster



Close Demark (slip),

(36)

Difficulties in Sensor system

iMAD



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

(37)

Three levels of concern

iMAD



Command Source

 Natural, subconscious

 Artificial, Volitional



Command Type

 Trigger

 Regulation



Artificial control

 Open-loop

 Close-loop (position, trajectory, force, slip, COG, etc.)

(38)

iMAD

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?

(39)

Application of FES systems

iMAD



User capacity and paralysis



Target function analysis



Stimulation Patterns



System Modeling



Control Strategies



Other considerations

 Safety, Economy, Cosmetic, Don-doff

 etc.

(40)

Conclusions

iMAD



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 eff ects -> FES devices can be used as therapeutic tool com bined with conventional physiotherapy

Functional Electrical Therapy (FET)

(41)

iMAD

Design Example:

CHRELMS

Restoration of standing function to

paraplegic by Functional Electrical

Stimulation

(42)

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)

(43)

Why FES walking at all?

iMAD



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

(44)

iMAD

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

(45)

iMAD

But paraplegics do stand !

Supported Standing



Free-hand Standing



Example: vertical back standing up

(46)

iMAD

Kinematics Analysis: controllable

?

Paralysed/Passive Joints



d.o.f. =3

(not 6)

(47)

iMAD

Kinetic Analysis:

Force Balance

Fx Fy

Mz

WB h

Body Arm

Leg

M M

M   





  ^M ^

^h

^  ^M ^

^H

^ ^h ^

^H

^ ^F ^

^H

  ^ ^h ^ ^ ^W ^

^B



(48)

iMAD

Novel Concept: Deficit as control signals

Leg H

H H

H

H H

H

ARM

Deficit

F a

M

F k

M

F h

M

M 

 







 



















   

 



 





Leg moment produced from Upper-body

 Upper-body Activities

(49)

iMAD

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

(50)

iMAD

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)

(51)

iMAD

System Setup

x y

z

Handle Transducer

Position Sensor Stimulator

Rack Computer

(52)

Software: controller

iMAD

K _P

1/s

 

1 /T _t K _I

e (deficit input)

y (Stimulation Pulse Width) Joint Model

(53)

Software (LabVIEW)

iMAD

(54)

S e n s o r S y s t e m S e n s o r I n t e r f a c e iMAD

C o o r d i n a t o r a l g o r i t h m

R e g u l a t o r A l g o r i t h m

S t i m u l a t o r I n t e r f a c e

M a n - m a c h i n e i n t e r f a c e a n d r e s u l t d i s p l a y

U s e r / E x p e r i m e n t e r

S tring P o t o utput (20 ) B ridge o utput (1 2 )

H andle R eac tio ns (1 2)

& J o int P o sitio n (1 8 )

S agittal plane defic its (6)

S tim ulatio n P ulse W idth (6)

I nstruc tio n P ac k ets v ia R S 2 32

(55)

iMAD

(56)

iMAD

Sagittal only Control Plane

All Joints Control Joint 20.00

Sampling Freq.

Hz

20.00 Stimulation Hz

6.00 Update Rate

Hz COM2 COM port

theta (z) theta (y)

1.6

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 Legs 1.5

R foot L foot Trunk Force Moment ON

Logger

0.20 Flush Rate

Hz 48.38

sec 51.59

34.23

Unknown

3.7 CHRELMS

00000111

40

-40 -20 0 20

100 0

Fx Fy Mz 2

RH Fx, Fy, & 10 Mz

50

-50 -25 0 25

100 0

LH Fx, Fy, & 10Mz

500

150 400

300 0

Calf, Quad.

Glue.

Right PW

500

150 400

100 0

Left PW Disturb(h)

1.00 0.00 1.00 0.00

Kp, Ki, Kd, & Tt for ankle

Kp, Ki, Kd, & Tt for knee 20.00

Sampling Freq PID

Disturb(k) backlog 6

25

Data window

OFF Ankle

RAMP Knee

RAMP Hip

1.0

0.0 0.2 0.4 0.6 0.8

0.000 Level

Up/Down

ON Auto Ankle

1.0

0.0 0.2 0.4 0.6 0.8

0.000 Level

Up/Down

ON Auto Knee

1.0

0.0 0.2 0.4 0.6 0.8

0.000 Level

Up/Down

ON Auto

Hip Manual

OFF SwA

OFF SwP

OFF SwL

OFF SwR

OFF FrL

OFF FrR

OFF Oth.

Other Mcon

(57)

iMAD

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

(58)

iMAD

Control Parameters



Three channels each leg

(i.e. gluteus, quadriceps, calf)



Static Indeterminacy



Conjugate Matrix



Control Parameter Tuning



I = 0.3, 1, 3 M

_con

 

  

  0 5 0 5 0 5 0 5

. .

. . M

_con

 

  

  0 75 0 25 0 25 0 75

. .

M

_con

 

  

 

1 0

0 1

(59)

iMAD

(60)

iMAD

CHRELMS : Standing Up



Consistent timing -> enable to learn



“Quick Knee Locking”



Able to half-stand



Asymmetry



Better Control but not smaller force

(61)

iMAD

Standing maneuver



Posture Switching- Prolong Standing



Swaying Forward



Swaying Backward



Swaying Leftward



Swaying Rightward



Free-one hand



Bending the knees

(62)

iMAD

(63)

iMAD

CHRELMS : Sitting down



“Knee moment

reduction” strategy

 40.2% Moment due to Body Weight

 89.5% Rate of Moment Change



“Release & Re-catch”



Prefer

14.59° 7.19°

44.02 54.43

82.0° 102.0°

57.63kg

CoM of HAT CoM of Thigh CoM of HAT & Thigh

57.63kg

17.0 kg 17.0 kg

32.0° 90.0°

117.0°

110.0°

Joint

(A) (B)

M

_con

 

  

 

1 0

0 1

(64)

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

(65)

iMAD

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

(66)

The future of an FES system?

iMAD



Advance of Electronic technique:

 System-on-Chip

 Micro Sensors

 Micro Stimulator

 Wireless System



Collaboration of Multi-disciplines

 Engineers

 Clinical members

 Patients

(67)

FES clinic

iMAD

P a r a l y s i s & C a p a c i t i e s e v a l u a t i o n

C u s t o m m a d e F E S s y s t e m

M u s c l e

T r a i n i n g C l i n i c a l T r i a l H o m e u s e &

f o l l o w - u p

E v a l u a t i o n S y s t e m

T e c h n i c a l B a n k

E n g i n e e r i n g K n o w l e d g e N e w t e c h n o l o g i e s

M e d i c a l k n o w l e d g e

A n a l y s i s &

E v a l u a t i o n P ati en ts

M E M S , N e r v e C u f f s e n s o r s & e l e c t r o d e s ,

M e c h a t r o n i c , e t c .

C l i n i c al &

B i o m ed i c al R ese arc h T eam