This document provides an overview of rehabilitation engineering and equipment. It discusses what rehabilitation is and examples of rehabilitation equipment like wheelchairs, prosthetics, and orthotics. The course outline covers sensors, motion capture equipment, assistive devices, and prosthetics. Sensors like gyroscopes, EMG sensors, and force sensors are explored. Motion capture using video cameras, infrared cameras, and depth sensors is examined. Virtual reality and its use in virtual rehabilitation is also summarized.

1. 10/4/2018
1
SBE 310
Rehabilitation Equipment
Fall 2018
What is Rehabilitation?
What is Rehabilitation Engineering?
How do we (Engineers) solve rehabilitation problems?
Can you think of examples of rehabilitation equipment??

2. 10/4/2018
2
Examples
Wheelchairs
Prosthetics
Orthotics
Assistive devices
Hearing aids
Brain computer interfaces (BCI) for control
Musculoskeletal Rehabilitation Equipment

3. 10/4/2018
3
Course Outline
• Sensors
• Types of motion capture/analysis equipment
• Applications of motion capture equipment
• Assistive devices for paralysis
• Prosthetics: upper and lower limb
ILOs
▪ Understand what is rehabilitation engineering
▪ Know different sensors used for rehabilitation equipment applications
▪ Learn the different methods and applications of human motion
capture and analysis
▪ Design of some examples of rehabilitation equipment and devices ..
devices for paralysis
▪ Understand principles and design of upper and lower limb
prosthetics.

4. 10/4/2018
4
SENSORS
They are used in many types of rehabilitation equipment
What is a Sensor?
A device that detects events or changes in quantities and provides a
corresponding output, generally as an electrical signal.
• Gyroscope
• Tilt sensor
• Pulse rate sensor
• EMG
• Flex sensor
• Force sensor
Examples:
• Temperature
• Humidity
• Pressure
• Motion (IR)
• Acceleration
• Proximity

5. 10/4/2018
5
Example: Accelerometer
How does the sensor measure acceleration?
Not using dv/dt
Using the concept of F = ma
Example: Gyroscope
▪ Measures angular velocity, rotational motion
▪ Based on the principle of conservation of angular momentum
▪ Can be 1, 2 or 3 axis gyro

6. 10/4/2018
6
Example: Flex sensor
Resistance changes with flexion / bending
Applications:
▪ Medical devices
▪ Rehabilitation devices
▪ Electrogoniometer
Inertial Motion Sensors
▪ IMS or IMU (unit)
▪ Used in human motion tracking systems
▪ Consist of : 3 axis accelerometer + 3 axis gyroscope on 1 chip (+ 3 axis
magnetometer)
▪ What is the size of these chips??
HOW ARE
THEY MADE??

7. 10/4/2018
7
What are MEMS?
▪ Micro-electro-mechanical systems
▪ Miniaturized mechanical and electro-mechanical elements
▪ Physical dimensions of MEMS devices range from below one micron
to several millimeters.
▪ Can be microsensors or microactuators
▪ In microsensors, the device converts a measured mechanical signal
into an electrical signal.
Advantages of MEMS
▪ Made using IC processes, ability to integrate multiple functionalities
onto a single microchip.
▪ Use techniques of batch fabrication so the per-unit microchip cost of
complex miniaturized electromechanical systems can be radically
reduced
▪ Reliability of miniaturized electromechanical systems is usually better
than the large scale equivalent
▪ Lower weight, increased portability, lower power consumption

8. 10/4/2018
8
Example: MEMS Accelerometer
Etched in Silicone
1. red electrode (electrical terminal) that has enough mass
to move up and down very slightly when accelerometer
moves.
2. The electrode is supported by a tiny beam (cantilever)
that's rigid enough to hold it but flexible enough to allow
it to move.
3. Electrical connection from the cantilever and electrode to
the outside of the chip so it can be wired into a circuit.
4. Below the red electrode, and separated from it by an air
gap, there's a second electrode (purple). The air gap
between the two electrodes means the red and purple
electrodes work together as a capacitor. As you move the
accelerometer and the red electrode moves up and
down, the distance between the red and purple
electrodes changes, and so does the capacitance
between them (microns). Insulation (shown as black
lines) prevent the red electrode from making direct
electrical contact with the purple one if the
accelerometer experiences a really big force (a sudden
jolt).
5. blue electrode above red electrode and another air gap
making a second capacitor. As before, the capacitance
between the blue and red electrodes changes as you
move the accelerometer.
Motion Analysis
Motion Analysis is the quantitative measurement and assessment of
human motion
Gait analysis is the quantitative measurement and assessment of
human locomotion.
Recall

9. 10/4/2018
9
Motion Analysis
Kinetic variables Kinematic Variables
Spatial and
temporal variables
Forces
Recall
Kinesiology
• Kinematics
Characteristics of motion
• Kinetics
Forces involved in motion (causing motion
or resulting from motion)
Recall

10. 10/4/2018
10
Methods of Gait/Motion Analysis
• Observational gait/motion analysis
• Instrumented gait/motion analysis
Usually kinematic and kinetic data
are recorded at the same time (motion capture) followed by
data processing (motion analysis)
Types of variables to quantify motion
Variables that can be measured
Variables that can be calculated from the measurements (inverse
dynamics)

11. 10/4/2018
11
Motion Capture Equipment
Equipment to capture Kinematic variables
1. Electrogoniometers
2. Optical Motion capture using markers and cameras
3. Inertial Motion sensor systems
Equipment to capture Kinetic variables
1. Dynamic electromyography
2. Force plates (ground reaction force)
3. Foot pressure distribution sensors
Equipment to measure Kinematic
variables
1. Electrogoniometers
2. Optical Motion capture
a. Video camera and markers
b. IR cameras and markers
c. 3D depth cameras
3. Inertial Motion Sensor systems

12. 10/4/2018
12
Selection: Evaluating functionality
1. Electrogoniometers
2. Optical Motion capture
a. Video camera and markers
b. IR cameras and markers
c. 3D depth cameras (Kinect)
3. Inertial Motion Sensor systems
Criteria:
• Accuracy
• Ease of use (setup, data acquisition and processing)
• Sufficiency of data (number of joints, DOF etc..)
• Does not affect motion pattern of subject
• Not constrained to a fixed location
• Cost
Rotational Motion
Angular motion.. Motion of bones relative to each other.
Variables: q (radians), w, a

13. 10/4/2018
13
Kinematics: Joint angles
One of the important
kinematic spatial
parameters is:
Joint Angles (ROM)
From angles we can
calculate velocity and
acceleration
Kinematics: 1.Electrogoniometer
Device that measures joint
angles
Converts change in angle
to change in voltage
Based on potentiometers
or strain gauges or flex
sensors

14. 10/4/2018
14
Motion Capture Equipment
Equipment to capture Kinematic variables
1. Electrogoniometers
2. Optical Motion capture
3. Inertial Motion sensor systems
Equipment to capture Kinetic variables
1. Dynamic electromyography
2. Force plates (ground reaction force)
3. Foot pressure distribution sensors
2. Optical Motion Capture
a. Video camera motion capture
b. IR Camera motion capture
c. 3D Depth camera (Kinect)

15. 10/4/2018
15
Kinematics: 2.a.Video Motion Capture
using passive markers
Define 2D reference frame (axes)
Table of 2D data: x,y position of each marker vs time
(for each frame)
Kinematics: 2.a.Video Motion Capture

16. 10/4/2018
16
Connect marker points to construct stick figure
From the joint angles you can calculate angular
velocity, linear velocity, accelerations.
Kinematics: 2.a.Video Motion Analysis
Calculate relative angles of joints in 2D

17. 10/4/2018
17
Graphical
results from
inverse
dynamics
calculation
Angle
Velocity
Acceleration
Kinematics: 2.b.IR camera systems
Gold standard of motion capture
Motion Capture systems include:
Hardware (cameras & markers) + Software (data capture)
Companies:
Qualysis
Innovision
Vicon
+ Advanced Biomechanical analysis modeling software (Visual3D) for motion
analysis

18. 10/4/2018
18
Typical Set up of IR Camera Motion
Analysis Lab
Hardware: Cameras
High speed cameras (1 – 8 or more)
Sampling rate (50– 1000 frames per sec (FPS))
Camera resolution
Marker detection (automatic or manual)

19. 10/4/2018
19
Hardware: Markers
Markers placed on joints and key
points
• reflective markers (passive
markers)
• infrared LEDs (active markers)
• emit RF for unique marker
identification.
M Taher
Motion capture data is 3D
Analysis is similar to video analysis but angles
calculated in 3D

20. 10/4/2018
20
Kinematics: 2.c. 3D Depth Sensors
• A single, low cost, physical sensor device that allows for a
3D representation of the environment.
• Built-in RGB color camera, an IR emitter and depth
sensor, and a microphone array.
• Example: The Microsoft Kinect, used in many
rehabilitation applications
s.
Microsoft Kinect
• The Kinect sensor provides
skeletal tracking and can retrieve
twenty joints coordinates of
the tracked user.
• Kinect is wireless and markerless thus offering total freedom in
movement.
• Research showed that the computation of joint angles using the
Kinect guarantees enough precision for most of the clinical
rehabilitation treatments.

21. 10/4/2018
21
Facial Tracking
How can the Kinect sensor be considered rehabilitation equipment??
It is for games!!
Virtual Rehabilitation

22. 10/4/2018
22
Virtual Rehabilitation
• What is Virtual Rehabilitation (VR)?
Virtual Reality and Gaming for Rehabilitation
• Why don't we just have subjects perform motor
tasks in the real world?
➢Virtual Reality creates a computer-generated virtual world with
which the user can interact in 3 dimensions so that the user feels that
he or she is part of the scene.
➢Virtual Reality brings the complexity of the physical world into the
safe environment of the laboratory.
➢Creates a synthetic environment with precise control over a large
number of physical variables while recording kinematic responses.
Types of Virtual Reality
• Immersive
A totally immersive VR system is where the subject sees only the virtual
world and the rest of the physical world is blocked from view. The virtual
environment is delivered by equipment worn by the user (like goggles or
head-mounted displays).
• Non-Immersive
Non-immersive VR is usually two-dimensional and delivered through a
computer screen. The user can control what is happening on screen by using
a device such as a joystick, mouse, or sensor.

23. 10/4/2018
23
Virtual Rehabilitation is Interactive
In the virtual environment:
• Design interactive exercises/games for specific neuromuscular
problems/disabilities
• Allow the user to interact with the Virtual World and with virtual
objects within the Virtual World.
Key feature: Interactive
Virtual Rehabilitation
• Based on principle of Neuroplasticity (Brain Plasticity)
• VR-based therapy can improve motor learning, balance, functional
mobility and participation in children and adults with neuromotor
impairments.
• Research shows improvement in stroke patients

24. 10/4/2018
24
Examples of games
Placing objects on shelves.
Interaction may be achieved by pointer controlled by
a mouse or joystick.
Examples of games
A representation of the user's hand is generated within the
environment where movement of the virtual hand is "slaved"
to the user's hand allowing a more natural interaction with
objects.

25. 10/4/2018
25
Examples of games
Images of the users themselves that appear as players
in the environment to interact with the Virtual
Environment.
Motion Capture for VR
Early VR system
• Motion Capture Based on cameras
• Large space required
• Expensive

26. 10/4/2018
26
Motion Capture for VR
Kinect
Inertial motion sensors
Data glove
Why Virtual Rehabilitation?
• Entertaining.. Increased motivation by making
therapy fun
• Real-time performance feedback
• Low cost if gaming sensors are used (home use)
• Telerehabilitation (can be monitored at a distance to
save time and effort)
For the Patient

27. 10/4/2018
27
Why Virtual Rehabilitation?
• Selection of Task
Can be a simple game with a score.
Can be individualized exercises to meet specific therapy goals
Can be tailored to individual’s level of ability
Can be self adaptive
• A safe testing and training environment (virtual world)
• Quantitative outcome measures
Can compute 3D joint angles
Quantitative Progress reports
• Low cost if gaming sensors are used (clinic use)
• Telerehabilitation (can be monitored and modified at a distance to
save time and effort)
For the Therapist
Motion Capture Equipment
Equipment to measure Kinematic variables
1. Electrogoniometers
2. Optical Motion capture
3. Inertial Motion Sensor systems
Equipment to measure Kinetic variables
1. Dynamic electromyography
2. Force plates (ground reaction force)
3. Foot pressure distribution sensors

28. 10/4/2018
28
Kinematics: 3. Inertial Motion Sensors
▪ IMS or IMU (unit)
▪ Each unit consists of : 3 axis accelerometer + 3 axis gyroscope on 1
chip (+ 3 axis magnetometer)
▪ Used in human motion tracking systems
▪ Attached to body segments to track motion
Applications of IMSs
Once you have the kinematic data:
• Gait analysis
• Physical therapy
• Sports studies
ST = I α

29. 10/4/2018
29
Wireless IMU System in Lab
• Full body wireless motion capture (camera free)
• One IMU attached on each segment
• Detects and measures acceleration, tilt, shock, vibration,
rotation
• Functional assessment of Biomechanics (FAB) software
• Real time 3D Kinematics and Kinetics (inverse dynamics)
of body motion with graphical models.
• http://www.biosynsystems.net/
Can you name one significant advantage of this technology over optical
systems??
Not constrained by LOCATION

30. 10/4/2018
30
Fall Detection
Motivation: Why do we need to study this topic??
• Accidental falls are common among elderly people and some
neurology patients
• Falls can result in lasting and critical consequences: injury, long-
term disability etc…
• Recovery/prognosis is dependent on time taken till treatment
starts (i.e. speed of discovery important)
Types of Falls
• Most falls in the elderly occur during ADLs
• A fall can occur not only when a person is standing, but
also while sitting on a chair or lying in bed

31. 10/4/2018
31
Fall Management Approaches
Fall Management
Fall Prevention Fall Detection
Interventions such as:
• exercise
• improved footwear
• assistive devices
• modification of the home
environment
• modification of medication
Fall Detection
Monitoring Approaches
Environment
Sensors
Wearable Body
sensors
• pressure sensors on chairs
• cameras
• RFID tags embedded
throughout the home
• Inertial motion sensors

32. 10/4/2018
32
Fall Detection
Can you think of an algorithm to detect a fall occurrence??
How to differentiate between a fall and a normal motion??
Detection Algorithms
Think of ‘free fall”
Maximum velocity just before impact followed by 0 velocity
Kinetic Variables
• Muscle forces (can be calculated from EMG or as explained in first
year)
• Ground reaction force (Force plate)
• Joint reaction forces (calculated)
• Foot pressure (Plantar pressure) distribution

33. 10/4/2018
33
Equipment to capture Kinetic variables
1. Dynamic electromyography
2. Force plates (ground reaction force)
3. Pressure sensors (Plantar pressure)
Kinetics: 1. Dynamic Electromyography
We have a wireless system in Rehab Lab

34. 10/4/2018
34
Kinetics: 2. Force Plate
To measure ground
reaction force (6D)
Most common based on
strain gauges
Ground reaction force during gait
Vertical component of GRF

35. 10/4/2018
35
Kinetics: 3. Pressure sensors (Plantar pressure)
Plantar Pressure
Importance in Rehabilitation
and
Measurement
What is plantar pressure??

36. 10/4/2018
36
Foot Anatomy
Plantar surface
Why measure plantar pressure?
➢Treat/prevent/predict medical conditions affecting
foot such as:
• Diabetes
• Ulcers
• Sensory neuropathy
• Multiple sclerosis

37. 10/4/2018
37
Diabetes/Ulcers/Sensory neuropathy
• Egypt has approx. 7.8 million adults suffering from diabetes
• Peripheral neuropathy or nerve damage is one of the most serious
complications of diabetes.
▪ Loss of protective sensation
▪ Cannot feel an ongoing injury due to the increased plantar pressure leading to
foot ulceration, serious infections and in some cases amputations.
The pressure map formed by
these pressure areas can be
compared to an "ideal"
(normal) pattern
Static plantar pressure distribution
Pressure distribution plate:
Sensor array

38. 10/4/2018
38
Important features of dynamic p. p.
Not only the magnitude of the plantar pressure is important but also
other factors such as:
• Rate of increase of pressure
• Duration of high pressure
• Frequency of applied pressure
• Pressure-time integral (widely used)
This is why dynamic measurement is important
How do we measure dynamic pp?
Very thin insoles with a sensor array
Can be worn inside shoes like any insole

39. 10/4/2018
39
Masking
Number of regions is a choice depending on application
Tradeoff: high processing time vs. loss of detail
Pressure peaks
Critical regions
at high risk for ulceration
Once critical regions are identified, pressure relieving insoles are custom made

40. 10/4/2018
40
Wireless System in Rehab Lab
Prosthetics
Very important type of rehabilitation equipment
References:
Atlas of Limb prosthetics, http://www.oandplibrary.org/alp/
Otto Bock catalogs: http://www.ottobockus.com/

41. 10/4/2018
41
Prosthesis: An artificial substitute or replacement of a
part of the body after amputation. A prosthesis is
designed for functional or cosmetic reasons or both.
Orthosis: An orthopedic appliance or apparatus used to
support, align, prevent, or correct deformities or to
improve function of movable parts of the body.

42. 10/4/2018
42
Considerations when choosing a prosthesis
• Amputation level
• Contour of the residual limb
• Expected function of the prosthesis
• Cognitive function of the patient
• Vocation of the patient (example, desk job vs. manual labor)
• Cosmetic importance of the prosthesis
• Financial resources of the patient
Characteristics of a successful prosthesis
• Achieves required mechanical function
• Comfortable to wear
• Easy to put on and off
• Lightweight
• Easy to operate/control
• Silent
• Durable
• Cosmetic
• Low and easy maintenance
• Patient motivation

43. 10/4/2018
43
Types of Prostheses
Upper Limb
Lower Limb
http://armdynamics.com/videos.php?news_id=185

44. 10/4/2018
44
DESIGN
Understand anatomy and function of missing limb
Decide how much function will be restored.
Design mechanical parts
Select materials (function, durability, weight, cost)
Design control source and methodology (easy to use)
Design attachment to body (secure, comfortable, easy to put on and off)
Power
DESIGN
1. Understand anatomy and function of missing limb
2. Decide how much function will be restored.
3. Design mechanical parts
4. Select materials (function, durability, weight, cost)
5. Design control source and methodology (easy to use)
6. Design attachment to body (comfortable, easy to put on and off)
7. Power

45. 10/4/2018
45
Anatomy and functions of the Upper Limb
(will not include shoulder)
Elbow
Flexion/Extension
Hand rotation

46. 10/4/2018
46
Wrist Flexion/Extension
Types of prehension

47. 10/4/2018
47
Types of prehension

48. 10/4/2018
48
Levels of Amputation
• Partial hand amputation -
• Wrist disarticulation -
• Transradial amputation - Below-
elbow amputation
• Elbow disarticulation - Transection
through the elbow joint
• Transhumeral amputation - Above-
elbow
• Shoulder disarticulation -
Transection through the shoulder
joint
Classification according to function
• Passive Cosmetic Prostheses
• Functional:
• Body-powered prostheses - Cable controlled
• Externally (electrically) powered prostheses – Myoelectric or neural control
UL
Prosthesis
Passive Functional
Myoelectric
Body
powered

49. 10/4/2018
49
Passive Cosmetic Hand
Functional Upper Limb Prostheses
UL
Prosthesis
Passive Functional
Myoelectric
Single Axis
Hand
Advanced
Hand
Body
powered

50. 10/4/2018
50
Functional Upper Limb Prostheses
We will Describe and discuss Components of the
prosthesis :
1. Body-powered prosthesis
(low cost)
2. Externally powered myoelectric prosthesis
(high cost)
3. Advanced Hand designs
(very high cost)
General Components of Upper Limb
Prosthesis
Terminal device (hand/gripper)
Wrist unit
Forearm unit
Elbow joint
Socket (fits over stump)
Suspension
Control system
Power

51. 10/4/2018
51
1. Body Powered Upper Limb Prosthesis
Body powered Trans-humeral Prosthesis
Terminal Devices
Hand Hook

52. 10/4/2018
52
Terminal Devices
Are operated by pulling cable
Can be voluntary opening or v. closing
Hand Hook
Opening and closing the hook
Single axis
1 Degree of freedom

53. 10/4/2018
53
Otto Bock voluntary opening hand
1 DOF
Covered with
cosmetic glove
Wrist unit
• Connects terminal
device to forearm.
• Provides:
Rotation
Flexion/Extension
Quick release

54. 10/4/2018
54
Forearm and elbow
Elbow hinge joint
1 DOF
Lock
Socket
Fits over stump.
Made by making a negative
then positive cast of stump.
Pour plastic material to
make total contact socket.
Suspension by straps or
suction.
Must be strong enough to
carry weight.
New materials: porous
Suspension socket

55. 10/4/2018
55
Socket using 3D laser scanner
Suspension straps and control cables
Shoulder Harness

56. 10/4/2018
56
Below Elbow: body powered control
Stainless steel cable to open
terminal device
2 Control cables:
1. For Locking elbow
2. For Flexing elbow and opening terminal device
Above-elbow body powered control

57. 10/4/2018
57
Above-elbow body powered control
Functional Upper Limb Prostheses
Describe and discuss:
• Components of the prosthesis in general.
• Body-powered prosthesis
• Externally powered myoelectric prosthesis
• Advanced Hand designs

58. 10/4/2018
58
Externally powered myoelectric prosthesis
Trans-radial (below elbow)
Socket (same)
Terminal device (hand)
Actuator (should be light weight,
silent, quick response)
Control
Power
Hands for myoelectric prosthesis
• Actuator: DC Motor
• High proportional grip force (up to 100 N)
• High proportional speed (up to 300 mm/s)
• Weight 460 gm
• Opening width 100 mm
Otto Bock Hand

59. 10/4/2018
59
Motion Control Hand
Actuator: DC Motor
Weight: about 400 gm
Antagonistic (opposite) pairs
Elbow joint
Biceps muscle
Triceps muscle

60. 10/4/2018
60
Myoelectric Control
EMG from 2 antagonistic muscles (can be biceps and
triceps)
Preamplification/processing
Microcontroller: can use threshold method
Control output to operate motor (open/close/stop)
NB EMG is for control NOT power
Power
Battery
• Rechargeable
• lightweight
• compact
• long lifetime

61. 10/4/2018
61
New Advanced Hands
Anthropomorphic Hands
Increasing DOF to mimic natural
hand and for fine motor control.
Problem is the need for more
control inputs
New Actuators
Hand Anatomy
Anthropomorphic hands
try to follow the shape
and movement of the
natural hand

62. 10/4/2018
62
-Finger structure similar to natural finger
-More DOF than standard prosthetic hand
-Flexion using control cable to flex 3 joints
at the same time i.e. with one control input
Finger flexion by pulling cable

63. 10/4/2018
63
Cylindrical Adaptive Grasp
The Shadow hand

64. 10/4/2018
64
iLimb
Remaining design issues:
Thumb: Manual positioning to change type of grasp.
4 predefined types of grasps
Actuators
New materials eg Shape Memory Alloys
Material that decreases in length when heated by electric current thus
producing FORCE
Advantages: Lightweight, silent, low cost…
Disadvantages: long length needed, small force produced

65. 10/4/2018
65
SMA wires
• Wire diameters ranging from 0.025mm – 0.5mm
• Price range $4 - $10 /m
ELECTROMYOGRAPHY
Electrical signal that can be detected from skeletal muscles when they
contract.
1. How is it generated?
2. How is it detected?
3. What does it look like?
4. How is it processed?
5. What can we do with it?

66. 10/4/2018
66
1. How is it generated? Motor Unit
The functional unit of the
neuromuscular system
Action Potential
http://upload.wikimedia.org/wikipedia/en/thumb/7/78/Apshoot.jpg/300px-Apshoot.jpg

67. 10/4/2018
67
Motor Unit Action Potential
• Typically, each motor neuron innervates several hundred muscle
fibers
• Motor Unit Action Potential (MUAP) = summed electrical activity of
all muscle fibers activated within the motor unit
• Muscle force increased through higher recruitment of motor units
2. How is it detected?
ELECTRODE TYPES
• Intramuscular -
Needle Electrodes
• Extramuscular –
Surface Electrodes

68. 10/4/2018
68
Surface electrodes
• Most common type is Silver – Silver Chloride electrodes.
• The EMG detected is call sEMG
Electrode placement
Surface Electrodes
• Advantages
• Quick, easy to apply
• No medical supervision, required certification
• Minimal discomfort
• Disadvantages
• Generally used only for superficial muscles
• Cross-talk concerns
• No standard electrode placement
• May affect movement patterns of subject
• Limitations with recording dynamic muscle activity

69. 10/4/2018
69
3. What does it look like?
Typical EMG Interference Pattern
4. How is EMG processed?
Amplification
& Filtering
Signal pick up
Conversion of Analog
signals to Digital signals
Signal
processing

70. 10/4/2018
70
Average Rectified Amplitude
• Rectified = all negative values converted to positive
values (absolute value)
• N.B. periods of activation & periods of inactivity
EMG Amplitude vs Muscle Contraction Intensity
• Amplitude increases with increased contraction
intensity
• BUT it is not a linear relationship
• Non-linear relationship between EMG amplitude and
contraction intensity

71. 10/4/2018
71
5. What can we do with it?
Control myoelectric prosthetic hand
Simplest form of control:
▪ Measure EMG from 2 antagonistic muscles
▪ Calculate rectified integrated EMG
▪ Depending on level of each muscle activity:
open, close or stop the hand
CONTROL
EMG from Biceps EMG from Triceps
Continuous segmentation
rectification and integration
Continuous segmentation
rectification and integration
COMPARE
If B > T OPENIf T > B CLOSE If T & B < threshold STOP

72. 10/4/2018
72
Lower Limb Prosthesis
DESIGN
Understand anatomy and function of missing limb
Decide how much function will be restored.
Design mechanical parts
Select materials (function, durability, weight, cost)
Design control source and methodology (easy to use)
Design attachment to body (secure, comfortable, easy to put on and off)
Power

73. 10/4/2018
73
Anatomy and Function of Lower Limb
Major joints:
Hip, Knee, Ankle
Major function:
Gait
Levels of lower limb amputation
We will only describe:
Above Knee (AK)
(transfemoral)
Below Knee (BK)
(transtibial)

74. 10/4/2018
74
Two basic types
• Exoskeletal
• Endoskeletal
• Exoskeletal
Older design, plastic shell
or wood
• Endoskeletal
Modular, support consisting
of an internal pylon usually
covered with a lightweight
material, such as foam.

75. 10/4/2018
75
Components of Prosthesis
• Socket
• Liner
• Suspension
• Knee joint
• Pylon (shank)
• Terminal device (foot/ankle)
What is the advantage of modular???
• Only the socket needs to be custom made.
• All other components are standard off-the-
shelf
• Pylons are adjustable lengths. Pylons and
adaptors made of titanium, steel or
aluminum.

76. 10/4/2018
76
• Socket
Many different types depending
on level and on shape and quality
of stump
(Job of prosthetist)
• Liner
• Suspension
What is the major
difference between an
upper limb and lower
limb socket???
Total Surface Bearing Sockets
Even distribution of
pressures using maximum
surface area

77. 10/4/2018
77
Prosthetic Knees
The prosthetic knee is the most complex component.
Essential Functions to be restored:
• Give support when people stand
(STABILITY during STANCE phase of gait),
• Allow smooth motion when people walk,
(SWING phase CONTROL)
• Permit movement when people sit, bend or kneel.
Types of prosthetic knees
▪ More than 100 different knees available today.
▪ Range from simple knees to complex mechanical knees to
microprocessor controlled knees.
▪ Will discuss small selection to show different types.

78. 10/4/2018
78
Major classification of knees
• Mechanical
Single Axis
Polycentric
• Computerized
How do you select??
Depending on patient level of activity
Mechanical Single Axis Knee
• Simple Hinge joint
• No Stance phase stability
• Needs lock
• Swing phase control by friction
• Low cost, light
• Easy maintenance
Otto Bock knee
Adjustable
flexion angle

79. 10/4/2018
79
Locking options
Manual Lock
Weight activated lock
Variable center of rotation of human knee joint
So single–axis (hinge) joint knee
is not good enough!

80. 10/4/2018
80
Mechanical Polycentric Knee
Why polycentric? To mimic human knee center of rotation (similar to
cruciate ligaments)
How? Four Bar Linkage
Otto Bock 4-bar knee
(Demo 4-bar knee)
Actuator/Power
What makes the knee joint rotate to provide flexion and extension?
Can you tell what the actuator is?
Where the power comes from?

81. 10/4/2018
81
Swing phase control
How fast can the knee flex and extend?
This determines walking speed.
• Can be simple friction
Or adjustable damping by:
• Hydraulic knee
• Pneumatic knee
compresses air as the knee is flexed,
storing energy, then returning energy as
the knee moves into extension
Modular Polycentric
Knee Joint with
Pneumatic Swing Phase
Control
Otto Bock C-Leg knee joint
Disadvantage: EXPENSIVE
Computerized Knees

82. 10/4/2018
82
Computerized Knees
• Fully microprocessor-controlled stance and swing phase.
• It measures the flexion angle and angular velocity of the knee joint.
• Strain gauges in the tube adapter and a knee angle sensor provide
measurement data, which enables microprocessors to calculate the
required resistances to movement.
• Servomotors correspondingly open and close hydraulic valves to
provide the required flexion and extension damping.
Prosthetic Feet
Functions:
• Joint simulation.
• Shock absorption.
• A stable weight-bearing base of support.
• Muscle simulation.
a few specialized feet actually provide some degree of dynamic
"push-off" during late stance.
• Cosmetic.

83. 10/4/2018
83
Prosthetic Feet
Four types of prosthetic feet:
• SACH
• Single axis foot
• Multi-axis foot
• Dynamic (energy storage)
Ref: Ch 18B Atlas of limb prosthetics
SACH Foot
Solid Ankle – Cushioned Heel
Simulates joint movement by compression of the heel
wedge.
Stable, light weight, low cost, easy to use, provides
shock absorption, no moving parts, cosmetic

84. 10/4/2018
84
Single Axis and Multi-axis foot
1 DOF
Ankle plantar flexion and
dorsiflexion
Heavier than SACH
3 DOF
Allows motion in three planes
Heavier than single axis
Less stable
Reminder about deformation
• Stress and strain
• Hooke’s Law (linear)
• Can also be non-linear

85. 10/4/2018
85
What is Strain Energy?
• Kinetic , potential energy
• Conservation of energy
• Strain energy
• Example springs
• U = ½ se (per unit volume)
• Total strain energy depends on volume
Dynamic Energy-Storage Feet
Carbon and
carbon
composite
springs store
energy
Dorsiflexion moment allows
the spring to compress or
distort, thereby absorbing
energy that is released
during push-off, and aids in
propelling the patient
forward.
Otto Bock C-Walk

86. 10/4/2018
86
Pylon Feet
Pylon feet store and release energy
both in the lower foot complex as well
as through deformation of the vertical
shank portion of the system. This
creates higher levels of elasticity in the
system and provides benefits in
recreational sports while not
compromising the function during
everyday activities.
The very low distal weight of these
products and their narrow, easily
finished construction provide
additional advantages
Carbon/ carbon-
polyurethane
springs
Very Light weight
Rehabilitation Engineering
Rehabilitation Equipment for Paralysis
You need to be the DESIGNER

87. 10/4/2018
87
What is the most common device used by paralyzed patients?
Wheelchair design

88. 10/4/2018
88
Wheelchair design
Design requirements:
Functional performance
Seating and postural support
Strength, durability and safety
Will give one example
Wheelchair design
Center of gravity and possibility of tipping

89. 10/4/2018
89
Neuro-rehabilitation
M Taher
Neuro-Rehabilitation
Is applicable in cases of:
• Stroke
• Traumatic brain injury
• Spinal cord injury
Resulting in paralysis or muscle weakness
M Taher

90. 10/4/2018
90
Paralysis
Paralysis is most often caused by damage in the nervous system,
especially the spinal cord. Other major causes are stroke, trauma
with nerve injury, or damage (disease) to the muscles.
Among the types of paralysis:
• Paraplegia (legs)
• Quadriplegia (arms and legs)
• Arm (after stroke)
How can we help patients with paralysed or weak muscles???
• Rehabilitation robots (robotic exoskeleton)
• Functional electrical stimulation
• Brain computer interface for:
oDevice control
M Taher

91. 10/4/2018
91
What would you design for arm paralysis after stroke?
A device that can move the arm.
Recall design requirements:
What is the actuator?
What is the control source?
How do you attach it to arm?
Neuro - Robotic Arm Brace
• Developed at MIT
• The mPower 1000 is indicated for
use to facilitate the following:
• (1) Brain injury rehabilitation by
muscle re-education.
• (2) Maintain or increase range of
motion.
Actuator: Motor

92. 10/4/2018
92
Input to device:
• EMG recorded using Surface electrodes.
Placement on Biceps and Triceps Muscles.
• EMG signals indicate the desire to move elbow.
• Control signal sent to elbow motor.
• Range of Motion: 3-to-130 Degrees
http://www.myomo.com/myomo-solutions-mPower-1000
What if we want a paraplegic to walk???
Bionic Walker

93. 10/4/2018
93
Ekso™ is the bionic
exoskeleton that
allows
wheelchair users to
stand and walk.
Actuators: Hip and knee motors
Control: external user control for step length and cadence. Stand and
sit. (see next slide)
Power: batteries

94. 10/4/2018
94
• Choice of 3 Walk Modes
• 1. FirstStep™A physical therapist actuates steps with a button push.
The user progresses from sit to stand and using a walker to walking
with crutches, often in their first session.
• 2. ActiveStep™User take control of actuating their steps via buttons
on the crutches or walker.
• 3. ProStep™The user achieves the next step by moving their hips
forward and shifting them laterally. The Ekso device recognizes that
the user is in the correct position and steps.
Ekso Bionics
• http://www.nytimes.com/video/2012/09/12/technology/100000001
778614/bionic-suits-aid-paraplegics.html

95. 10/4/2018
95
What if there is damage to the nerves but the muscles are intact.
What do you suggest???
Functional Electrical Stimulation (FES) or
(TENS)
It is a technique that causes a paralyzed muscle to contract
through the use of an electrical current.
To design an orthotic device: you need to know WHEN to
activate the muscle.
M Taher
Components: sensing, decision making, activation

96. 10/4/2018
96
Orthotic FES
• The actuator is the muscle
• The force produced by the stimulated muscle depends on the pulse
amplitude, duration, and frequency as well as the shape of the pulse
train.
• Joint angles can be controlled by modulating the intensity of
stimulation delivered to the flexor and extensor muscles, which
actuate the joint in opposite directions.
Application 1: Drop Foot correction
FES of 1 muscle
Challenge: Control ..
Ankle dorsiflexion must be at the
correct time for normal gait
Solution: Must track continuously
where we are in the gait cycle
M Taher

97. 10/4/2018
97
Muscle stimulation causes
ankle dorsiflexion
The challenge is
to select the
correct
transducer to get
the timing
accurately
M Taher
Application 2: Walking Assist
FES of 2/3 muscles
• Cases of hemiplegia or hemiparesis (muscle
weakness)
• 1 FES circuit + Wireless electrodes for:
➢knee (flexion and/or extension)
➢ankle dorsiflexion
• Transducers (to detect timing in the gait cycle)
• Microcontroller to sequentially stimulate
selected muscles.
M Taher

98. 10/4/2018
98
Walking Assist
FES for knee and ankle
Wireless
Brain Computer Interface (BCI)
Objective: to detect the user's
commands from EEG signal

99. 10/4/2018
99
Recording EEG signals
Electrode cap
Wireless electrode headset
Challenge of
reducing number
of electrodes, and
selecting the best
locations
M Taher
Simple EEG Signal

100. 10/4/2018
100
Subject is trained to visualise 1 or 2 motor tasks.
EEG processing, classification, machine learning/ training
Output can be used for control.
Example:
Wheelchair
Orthosis
Prosthetic arm….