biomechatronics lecture 3
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Biomechatronics
Bart Koopman
lower extremity orthotics and prosthetics
Biomechatronics
Plant: Skeletal system,
external load
Actuator:muscles
Sensors: physiological
sensory system
intention
Plant: Orthosis
Prosthesis
Actuator:motor
Sensors: artificial
Artificial
Physiological
Controller:artificial
Controller:CNS
Prosthetics and Orthotics
Prosthesis:• Replacement of body
parts and/or functions
Orthosis:• Support of body functions
Short history: amputation and prosthesiology
• 1000 bC: Rig-Veda (sanskriet)• 400 bC: Hippocrates• 300 bC: eldest prosthesis
Amputation in middle ages
H. Von Gerßdorf, 1517, Feldtbuch der Wundarztney
Armprosthesis
Götz von Berlichingen, Landshut1504
Ambroise Paré (1510-1590)
Prosthesis of Paré
Dominique Jean Larrey (1766-1843)
Modern amputation techniques
Orthotics
Functions:• Support• Redressing• Stabilization (immobilization)• Cosmetic
Control orthosis
Plant: Skeletal system,
external load
Actuator:muscle
Controller:Central Nervous
system (CNS)
Sensors: physiological
sensory system
intentionActiv-ation force Movement
Orthosis
Muscle control
motor unit
fiber
fiber
fiber
fiber
fiber
motor unit
mor
phol
ogy r11
r12
Muscle 1
motor unit
fiber
fiber
fiber
fiber
fiber
motor unit
mor
phol
ogy
r2
Muscle 2
Joint 1
Joint 2+
+
Mj1,pass
Seg
men
ts m
odel
Mj2,pass
347106104
Normal control
r11
r12
r2
knee joint
Hip joint+
+
Mj1,pass
Mj2,pass
Muscle 1
Muscle 2
Mechanical properties
Segments model
Hip angle
Knee angle
External loads
Sensor dynamics
control orthosis
r11
r12
r2
Knee joint
Hip joint+
+
Mj1,pass
Mj2,pass
Muscle 1
Muscle 2
Mechanical properties
Segments model
Hip angle
Knee angle
Orthosis
External loads
Skeletal systemMuscles
Phys. Sensors
CNS
OrthosisProsthesis
MotorArt. Controller
Art. Sensors
Example
UTX-swing orthosis• Knee Ankle Foot Orthosis for
paralyzed knee muscles• controller allows flexion during
swing and locking during stance
Old KAFO UTX-swing
Leg orthoses
Prosthetics
Functions:• Support• Cosmetic
TF-prosthesis:• modular• 1,5 – 4 kg• 3 – 30 k€
Amputations in NL
Amputation causes
Normal control
r11
r12
r2
knee joint
Hip joint+
+
Mj1,pass
Mj2,pass
Muscle 1
Muscle 2
Mechanical properties
Segments model
Hip angle
Knee angle
External loads
Sensor dynamics
control prosthesis
r2 Hip joint+
Mj2,pass
Muscle 2
Mechanical properties
Segments model
Hip angle
Knee angleProsthesis
External loads
Sensor dynamics
control prosthesis
Mechanical properties
Segments model
Hip torque
Knee angleProsthesis
External loads
Sensor dynamics
Hip angle
Prostetic knee design
4-axial knee: • Improve local stability• Improve controllability• No actuation!
Inverted knee design
Posterior view
Model predictions: • increased push-off time• increased velocity
Regular vs. inverse knee
Post. Ant.
polar curve
inverted knee
-0,50
0,00
0,50
1,00
1,50
0 5 10 15 20 25 30 35
Knee Angle [deg]
dM/dϕ stable
regular 4-axial knee
-2,00
-1,50
-1,00
-0,50
0,000 5 10 15 20 25 30 35
Knee Angle [deg]
dM/dϕ instable
Experimental results
Skeletal systemMuscles
Phys. Sensors
CNS
OrthosisProsthesis
MotorArt. Controller
Art. Sensors
Example
EMG-activated prostheses• lower extremities: controlled damping,
no motor, artificial sensors• upper extremities: myo-electric arm
prosthesis, motor, no artificial sensors
Skeletal systemMuscles
Phys. Sensors
CNS
OrthosisProsthesis
MotorArt. Controller
Art. Sensors
Example
Skeletal systemMuscles
Phys. Sensors
CNS
OrthosisProsthesis
MotorArt. Controller
Art. Sensors
Example
Otto Bock C-leg
Prosthetic foot design
passive mechanism: • damping 10 J• energy storing??• No actuation!
Concepts of gait
• Walking is:– preventing to fall– cyclical movement with left/right foot placements in
front of the other supporting body weight
• The purpose of bipedal walking is to maximize the double support time while maintaining the forward velocity.
• Stability is maintained by balancing the trunk through coordinated actions of joints.
Double support phase
Stilt walking
Pelvic tilt: ±35°
Stilt walking + feet
Pelvic tilt: ±15°
Stilt walking + feet + knees
Pelvic tilt: ±0°
Normal walking(feet, knees, ankles, pelvic rotation)
Pelvic tilt: free
Why is d.s. phase important ?
• Largest ground reaction forces
• largest muscle forces• almost all mechanical
work• stable position
slow walking
00,20,40,60,8
11,21,4
0 20 40 60 80 100
time [% stride]
reac
tion
forc
e [-]
right left total
other phases are more or less ballisticMaximize double support time !
Prosthetic / orthotic gait
Walking without knee function would result in…
• Reduced velocity• Reduced double support time• Reduced step length• Increased pelvic tilt
Balancing mechanism
• direct ground reaction force (push against large mass of trunk)
• trunk will rotate (a little)• requires coordinated
joint actions
Balancing mechanism
Trunk movement in walking
Fast walking
Normal walking
Walking with large steps