1
Human-Friendly Robot Design
Retrofitting the PUMA with Torque Sensors
Torque Control
• manipulation
• cooperation
• safety, interactivity
• compliance, force control
• dynamic performance
: a basic capability
ARTISAN(1990-95)
ARTISAN(1990-95)
1 2
3 4
5 6
2
intelligence
for
mechanisms
Safety
Safety
Performance
Competing?
Requirements
Human-Friendly Robots Human-Friendly Robots
• Dependable & Safe• Soft Actuators• Light Structures• Impact-Reduction Skin• Low Reflected Inertia• Distributed Sensing• Good Performance
PumaConventional Geared Drive:
• Lighter structure
• Large reflected actuator inertia
Jmotor
Ngear
Jlink
Jmotor
Ngear
Jlink
(Jlink + N2Jmotor)
Effective Inertia
Heavy structure
Technology
Puma
Effective Joint Inertia
2( )rigid body i motor iA A diag N J
7 8
9 10
11 12
3
Safety Metric
Effective MassNormalized
PUMA560 (Payload 20N)
1.16
Safety Metric
Normalized Effective Mass
Human (Payload 60N)
0.04
PUMA560 (Payload 22N)
1.16
Safety Metric
Normalized Effective Mass
Human (Payload 62N)
0.04
DM2 (Payload 60N)
0.06
PUMA560 (Payload 22N)
1.16
Safety Metric
Normalized Effective Mass
Human (Payload 62N)
0.04
DM2 (Payload 60N)
0.06
2s (Payload 33N)
0.02
Inertia Property
1
1( )u Tu u
Effective Inertia/mass perceived in a direction u u
Acceleration Capacity
:E Torque to Acceleration Transmission
13 14
15 16
17 18
4
Acceleration CapacityOptimized Design
Initial Design Optimized Design
Why Are Robotic Arms Unsafe?
Robot Collision
Head Injury Criteria (HIC)
Torq
ue
Mag
nit
ud
e
Frequency
Actual Torque Requirements
Actuation Requirements
Torque Vs Frequency: Square Wave
+
Assumed Torque Requirements
Torq
ue
Mag
nit
ud
e
Frequency
ElasticCoupling Large Base
Actuator
Parallel Actuation
Small JointActuator
Distributed Macro Mini (DM2) Approach
Robot Characteristics
Equivalent Mass-Spring Model
Robot Collision
• Effective Inertia• Effective Stiffness• Impact Velocity
Effective Inertia at Contact
1 1 Tv vJ A J 1
1a T
v
Iu u
19 20
21 22
23 24
5
2coseK K 1 1 1
a hk k k
Effective Stiffness
with
Impact Velocity
Manipulator Safety Index (MSI) Manipulator Safety Index (MSI)
Variation with contact point – Interface Stiffness constant at 20KN/m
Manipulator Safety Index (MSI)
Variation with Configuration – Interface Stiffness constant at 20KN/m
“the high capacity of a large robot with the fast dynamics and safety of a small one”
DM2 - Human-Friendly Robot
25 26
27 28
29 30
6
To
rqu
e M
agn
itu
de
+
Joint actuator(high frequency)
Base actuator(low frequency)
Elastic Coupler
(Torsional Spring)Mini actuator
Brushless motor
Macro actuator
Brushed DC motor
DM2 New Testbed DM2 vs. PUMA 560: Effective Mass Comparison
PUMA 560 (link 2 and link 3)
HFR (conventional actuation)
HFR (DM2 actuation)
Maximum effective mass:
PUMA 560: 24.37 kg
HFR (Macro actuation): 12.71 kg
HFR (DM2 actuation): 2.81 kg
10
20
30
30
210
60
240
90
270
120
300
150
330
180 0
10x reduction in effective inertia
3x increase in position control bandwidth
10x decrease in trajectory tracking error
SafetyAND
Performance
DistributedMacro-MiniActuation
DM2
DM2 Performance
31 32
33 34
35 36
7
DM2 - Hybrid Actuation
artificial muscles with compact pressure regulators pneumatic artificial muscles
DM2 - Hybrid Actuation
pneumatic artificial muscles
DM2 - Hybrid Actuation
pneumatic artificial muscles
DM2 - Hybrid Actuation
pneumatic artificial muscles
DM2 - Hybrid Actuation
pneumatic artificial muscles
DM2 - Hybrid Actuation
37 38
39 40
41 42
8
DM2 - Hybrid Actuation
artificial muscles with compact pressure regulators
Human-Friendly Robot Design – DM2
2.S
: Stanford Human-Safe Robot 2s : Stanford Human-Safe Robot
muscle 300N @ 4bar
upper arm 34cm
lower arm 29cm
total mass 1.5kg
torque (7.5,5.0)Nm
mini (1.0,0.3)Nm
force@effector 14N
2.S
Macro……………0.5HzMacro/Tension 7.0HzMacro/Mini……. 35Hz
Ps
F2
F1
Load Cells
Pressure Regulator
Pressure Regulator
U2
U1
P1
P2
Tj,θ
0.4 0.6 0.8 1 1.2 1.4 1.60
0.5
1
1.5
2
2.5
3
3.5
4
Time [ sec ]
Posi
tion
[ de
g ]
Desired Pos it ion
M acro
DM 2
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Time [ sec ]
Tor
que
[ N
m ]
D esired T orque
M acro
D M 2
Stanford Human-Safe Robot
43 44
45 46
47 48
9
Virtual Wall (macro only/macro-mini)
1.52s : New Design 1.52s : New Design
Safety Comparison
Effective Mass: 1.2Kg
DM2
Effective Mass: 3.5Kg
Human
Effective Mass: 2.1Kg
PUMA560
Effective Mass: 25Kg
2s
: Stanford Human-Safe Robot 2s
49 50
51 52
53 54
10
: Stanford Human-Safe Robot 2s
Impact-reducingproximity andpressure sensingSkin using SDM
𝑆2𝜌 : Stanford Safety Robot
𝑆2𝜌 2.0 : New Design 𝑆2𝜌 Testbed
+
Pneumatic Muscle(low frequency)
Electrical Motor(high frequency)
𝑆2𝜌 Experimental ResultsMacro Macro + Mini
Position
Force
6Hz 26Hz
Safety Comparison
55 56
57 58
59 60
11
Safety Comparison 𝑆2𝜌: Motion Range(sine wave)
𝑆2𝜌 : Contact Force Control
61 62
63 64
Top Related