Case Study: Term...
Transcript of Case Study: Term...
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Case Study: Term Project• Expectations for the term project• An example of a previous term project
1
© 2016 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
AAR Design Project Statement• Perform a detailed design of a small astronaut
assistance rover, emphasizing mobility systems– Chassis systems (e.g., wheels, steering, suspension…)– Support systems (e.g., energy storage)– Navigation and guidance system (e.g., sensors,
algorithms...)
• Design for Moon, then assess feasibility of systems for Mars, and conversion to Earth analogue rover
• This is not a hardware project - focus is on detailed design (but may be built later!)
2
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Objectives for Design Project (1)• UMd SSL is proposing to do month-long
simulations of lunar/Mars science exploration missions to examine impact of robotics
• Primary missions would be held at HI-SEAS in Hawaii
• Rover design should facilitate shipping to/from Hawaii– Minimal size and mass– Modular construction for packing (ideally each less than
50 lbs with packaging)
3
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Objectives for Design Project (2)• Multiple individual rovers
– One rover/crew– Rover can carry two crew in contingency mode– Both responsive and unresponsive transport
• Operation on volcanic soils and terrains• Capable of bring brought through airlock for
repair or servicing
4
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Level 1 Requirements (Performance)1. Rover shall have a maximum operating speed of
at least 15 km/hour on level, flat terrain2. Rover shall be designed to accommodate a 0.3
meter obstacle at minimal velocity3. Rover shall be designed to accommodate a 0.1 m
obstacle at a velocity of 7.5 km/hour4. Rover shall be designed to accommodate a 30°
slope in any direction at a speed of at least 5 km/hour with positive static and dynamic margins
5
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Level 1 Requirements (Payload)5. Rover shall be be designed for an instrument
payload with a mass of 50 kg and volume of 0.25 m3
6. Rover shall also accommodate a Ranger-classs sample-collection manipulator system with a mass of 50kg
7. Rover shall be designed to nominally transport a 95th percentile American male crew in full pressure suit
8. Rover shall be capable of carrying two 95th percentile crew in a contingency
6
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Level 1 Requirements (GN&C)9. Rover shall be be capable of being controlled
directly, remotely, or automated10.Rover shall be capable of following an astronaut,
following an astronaut’s path, or autonomous path planning between waypoints
11.Rover shall be capable of operating during any portion of the lunar day/night cycle and at any latitude
7
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Final Project Expectations• Final design of rover
– Solid models of design – Design evolution through as the analysis progressed– Details of mass, power, etc.
• Trade studies (NOT an exhaustive list!)– Number, size, configuration of wheels– Diameter and width of wheels– Size and number of grousers– Suspension design– Steering design– Alternate design approaches (e.g., tracks, legs, hybrid)
8
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Final Design Expectations (2)• Vehicle stability
– Slope (up, down, cross)– Acceleration/deceleration– Turning– Combinations of above
• Terrain ability (“terrainability”)– Weight transfer over obstacles– Climbing/descending vertical or inclined planes– Hang-up limit (e.g., high-centering, wheel capture)
9
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Final Design Expectations (3)• Suspension dynamics• Development of drive actuator requirements• Detailed wheel-motor design• Development of steering actuator requirements• Detailed steering mechanism design• Mass budget (with margin)• Power budget (with margin)• Other design aspects as included
10
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Final Project Presentations• Tuesday, Dec. 6 and Thursday, Dec. 8 (dates
corrected)• Each final project will be presented in class
– Single-person projects: 15 minutes– Double-person projects: 30 minutes
• Looking for volunteers to go on Tuesday• Otherwise, I’ll pick randomly on the day
11
Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics
U N I V E R S I T Y O FMARYLAND
Final Project Submissions• You should submit the slides you used for the
presentation on Tuesday, December 6 (whether or not you present on that day)
• You should submit a comprehensive set of slides documenting your design by the posted final exam day for this class, Tuesday, December 20.
• If you feel your presentation is comprehensive, just send me an e-mail saying that there will be no further report
• Not looking for spreadsheets or Matlab code
12
Terrestrial Lunar Rover(TLR)
ENAE788X Planetary Surface Robotics
Design Project
Team Members Cagatay Aymergen • Jignasha Patel
Syed Hasan • John Tritschler
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 14
Overview• Project Requirements and Objectives • Concepts Explored • TLR Design Overview • Terramechanics and Energetics • Stability and Breaking • Steering • Suspension system • Chassis • Motors and Gearing • Track Wheel Hybrid Mobility Unit Details • TLR Design Details • Operations • Sensors • Mapping • Command and Control • Mass Budget • Reliability and Fault Tolerance • Earth Analog Considerations • Possible Improvements to TLR
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 15
• Project Description • Perform a detailed design of the mobility systems for a small pressurized rover
– Chassis systems (e.g., wheels, steering, suspension...) – Navigation and guidance system (e.g., sensors, algorithms...)
• Design for moon, then assess feasibility of systems for Earth analogue rover
• The following are the level one requirements provided to impact our design: • L1-1: Rover shall have a maximum operating speed of at least 15 km/hour on level,
flat terrain • L1-2:Rover shall be designed to accommodate a 0.5 meter obstacle at minimal
velocity • L1-3: Rover shall be designed to accommodate a 0.1 meter obstacle at a velocity of
7.5 km/hour • L1-4: Rover shall be designed to accommodate a 20° slope in any direction at a speed
of at least 5 km/hour with positive static and dynamic margins
• The following are the specifications provided to impact our design: • L1-5: Rover shall be capable of supporting a mass (exclusive of chassis and mobility
system) of at least 1000 kg • L1-6: Rover shall be capable of accommodating a cylindrical pressurized cabin that is
1.80 meters in diameter and 1.83 meters long • L1-7: Target overall vehicle mass shall be less than 1800 kg with positive margin
Project Requirements & Specifications
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 16
Project Requirements & Specifications• The following are the Level 2 requirements derived to impact our design: • L2-1: The vehicle shall be designed to be operational on the surface of the moon with
the environmental constraints given in Table 1. • L2-2: An analog test vehicle shall be designed to be operational on the surface of the
earth with the environmental constraints given in Table 1.
• The following are the design goals derived to impact our design: • G-1: Safety factors - at least 1.5 to 2.0 (this might be driven by the earth analog
requirements) • G-2: Fault tolerance - Every subsystem should be single fault tolerant • G-3: Mobility - 360 degrees on the spot turns and movement • G-4: Adaptability - Don't be limited to only this size payload (mass, weight…etc)
Table 1
Earth Moon
Gravitational Acceleration 9.8 m/s2 (1g) 1.545 m/s2 (0.16g)
Atmospheric Density 101.350 pa (14.7 psi) -
Atmospheric Constituents 78% N2 – 21% O2 -
Temperature Range 120 F – -100 F 250 F – -250 F
Length of Day 24 Hr 28 Days
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 17
Concepts Explored
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 18
Concepts Explored
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 19
TLR Design Overview
Supported Payload Accommodates All
Sensors and Avionics
4 Track-Wheel Hybrid Mobility Unit
Large Wheel Driving Wheel
Houses the MotorsSmall Wheel Free Running
Aluminum Chassis
Wheel Connector BarTracks
Suspension System
Wheel to Chassis Connection
• Each mobility unit is capable of rotating about the center of the large wheel • Each large wheel houses two motors that are cross strapped to operate the wheel and the actuator to rotate the wheel connector bar
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 20
Terramechanics and Energetics• Trades
– Draw Bar Pull vs. Wheel Diameter vs. Wheel Width – Grousers vs. No-Grousers – Power vs. Wheel Diameter vs. Wheel Width – Number of wheels vs. Wheel Diameter vs. Wheel Width – Wheels vs. Tracks
• Wheels – Wheel diameter varying from 0.3 to 1.0 m – Wheel width varying from 0.1 to 0.6 m
• Tracks – Large wheel diameter varying from 0.3 to 1.0 m – Small wheel diameter 2/3 of the large wheel
• Study Cases (for each trade above) – Flat terrain with 15km/hr velocity – 20o slope with 5km/hr velocity – 10 cm obstacle with 7.5km/hr (assuming all wheels encounter the obstacle at the
same time) – 50 cm obstacle at minimum velocity (assuming all wheels encounter the obstacle
at the same time)
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 21
Wheeled System – Draw Bar Pull – No GrousersFlat Terrain
4 w
heel
s6
whe
els
-1000.00
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
No
Gra
user
s) -
DP
- (N
)
Wheel Diameter 0.30 m Wheel Diameter 0.40 mWheel Diameter 0.50 m Wheel Diameter 0.60 mWheel Diameter 0.70 m Wheel Diameter 0.80 mWheel Diameter 0.90 m Wheel Diameter 1.0 m
-1000.00
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
No
Gra
user
s) -
DP
- (N
)
Wheel Diameter 0.30 m Wheel Diameter 0.40 mWheel Diameter 0.50 m Wheel Diameter 0.60 mWheel Diameter 0.70 m Wheel Diameter 0.80 mWheel Diameter 0.90 m Wheel Diameter 1.0 m
-1800.00
-1600.00
-1400.00
-1200.00
-1000.00
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
No
Gra
user
s) -
DP
- (N
)
Wheel Diameter 0.30 mWheel Diameter 0.40 mWheel Diameter 0.50 mWheel Diameter 0.60 mWheel Diameter 0.70 mWheel Diameter 0.80 mWheel Diameter 0.90 mWheel Diameter 1.0 m
20o Slope
-1800.00
-1600.00
-1400.00
-1200.00
-1000.00
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
800.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
No
Gra
user
s) -
DP
- (N
)
Wheel Diameter 0.30 mWheel Diameter 0.40 mWheel Diameter 0.50 mWheel Diameter 0.60 mWheel Diameter 0.70 mWheel Diameter 0.80 mWheel Diameter 0.90 mWheel Diameter 1.0 m
Turtle Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 22
Wheeled System – Draw Bar Pull – With GrousersFlat Terrain
4 w
heel
s6
whe
els
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
2200.00
2400.00
2600.00
2800.00
3000.00
3200.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
2200.00
2400.00
2600.00
2800.00
3000.00
3200.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
-300.00
-100.00
100.00
300.00
500.00
700.00
900.00
1100.00
1300.00
1500.00
1700.00
1900.00
2100.00
2300.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 m Wheel Diameter 0.04 mWheel Diameter 0.05 m Wheel Diameter 0.06 mWheel Diameter 0.07 m Wheel Diameter 0.08 mWheel Diameter 0.09 m Wheel Diameter 0.10 m
-300.00
-100.00
100.00
300.00
500.00
700.00
900.00
1100.00
1300.00
1500.00
1700.00
1900.00
2100.00
2300.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 m Wheel Diameter 0.04 mWheel Diameter 0.05 m Wheel Diameter 0.06 mWheel Diameter 0.07 m Wheel Diameter 0.08 mWheel Diameter 0.09 m Wheel Diameter 0.10 m
20o SlopeTurtle Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 23
Wheeled System – Obstacles – Draw Bar Pull – With Grousers
10 cm Obstacle
4 w
heel
s6
whe
els
50 cm Obstacle
-1500.00
-1300.00
-1100.00
-900.00
-700.00
-500.00
-300.00
-100.00
100.00
300.00
500.00
700.00
900.00
1100.00
1300.00
1500.00
1700.00
1900.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
-1500.00
-1300.00
-1100.00
-900.00
-700.00
-500.00
-300.00
-100.00
100.00
300.00
500.00
700.00
900.00
1100.00
1300.00
1500.00
1700.00
1900.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
-1650.00
-1600.00
-1550.00
-1500.00
-1450.00
-1400.00
-1350.00
-1300.000.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
-1550.00
-1500.00
-1450.00
-1400.00
-1350.00
-1300.00
-1250.000.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
Turtle Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 24
Wheeled System – Obstacles – Draw Bar Pull – With Grousers
50 cm Obstacle On All Wheels
4 w
heel
s6
whe
els
50 cm Obstacle On Two wheels
-1800.00
-1600.00
-1400.00
-1200.00
-1000.00
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 1.0 mWheel Diameter 1.1 mWheel Diameter 1.2 mWheel Diameter 1.3 mWheel Diameter 1.4 mWheel Diameter 1.5 mWheel Diameter 1.6 mWheel Diameter 1.7 m
-1800.00
-1600.00
-1400.00
-1200.00
-1000.00
-800.00
-600.00
-400.00
-200.00
0.00
200.00
400.00
600.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 1.0 mWheel Diameter 1.1 mWheel Diameter 1.2 mWheel Diameter 1.3 mWheel Diameter 1.4 mWheel Diameter 1.5 mWheel Diameter 1.6 mWheel Diameter 1.7 m
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 1.0 mWheel Diameter 1.1 mWheel Diameter 1.2 mWheel Diameter 1.3 mWheel Diameter 1.4 mWheel Diameter 1.5 mWheel Diameter 1.6 mWheel Diameter 1.7 m
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
2200.00
2400.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 1.0 mWheel Diameter 1.1 mWheel Diameter 1.2 mWheel Diameter 1.3 mWheel Diameter 1.4 mWheel Diameter 1.5 mWheel Diameter 1.6 mWheel Diameter 1.7 m
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 25
Wheeled System – Power – With GrousersFlat Terrain
4 w
heel
s6
whe
els
0.00500.00
1000.001500.002000.002500.003000.003500.004000.004500.005000.005500.006000.006500.007000.007500.008000.008500.009000.009500.00
10000.0010500.0011000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel Diameter 0.30 mWheel Diameter 0.40 mWheel Diameter 0.50 mWheel Diameter 0.60 mWheel Diameter 0.70 mWheel Diameter 0.80 mWheel Diameter 0.90 mWheel Diameter 1.0 m
0.00500.00
1000.001500.002000.002500.003000.003500.004000.004500.005000.005500.006000.006500.007000.007500.008000.008500.009000.009500.00
10000.0010500.0011000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel Diameter 0.30 mWheel Diameter 0.40 mWheel Diameter 0.50 mWheel Diameter 0.60 mWheel Diameter 0.70 mWheel Diameter 0.80 mWheel Diameter 0.90 mWheel Diameter 1.0 m
20o Slope
1500.00
1700.00
1900.00
2100.00
2300.00
2500.00
2700.00
2900.00
3100.00
3300.00
3500.00
3700.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel Diameter 0.30mWheel Diameter 0.40mWheel Diameter 0.50mWheel Diameter 0.60mWheel Diameter 0.70mWheel Diameter 0.80mWheel Diameter 0.90mWheel Diameter 0.10m
1500.00
1700.00
1900.00
2100.00
2300.00
2500.00
2700.00
2900.00
3100.00
3300.00
3500.00
3700.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel Diameter 0.30mWheel Diameter 0.40mWheel Diameter 0.50mWheel Diameter 0.60mWheel Diameter 0.70mWheel Diameter 0.80mWheel Diameter 0.90mWheel Diameter 0.10m
Turtle Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 26
Wheeled System – Obstacles – Power10 cm Obstacle
4 w
heel
s
6 w
heel
s0.00
500.001000.001500.002000.002500.003000.003500.004000.004500.005000.005500.006000.006500.007000.007500.008000.008500.009000.009500.00
10000.0010500.0011000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel Diameter 0.30mWheel Diameter 0.40mWheel Diameter 0.50mWheel Diameter 0.60mWheel Diameter 0.70mWheel Diameter 0.80mWheel Diameter 0.90mWheel Diameter 1.0 m
0.00500.00
1000.001500.002000.002500.003000.003500.004000.004500.005000.005500.006000.006500.007000.007500.008000.008500.009000.009500.00
10000.0010500.0011000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel Diameter 0.30mWheel Diameter 0.40mWheel Diameter 0.50mWheel Diameter 0.60mWheel Diameter 0.70mWheel Diameter 0.80mWheel Diameter 0.90mWheel Diameter 1.0 m
Turtle Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 27
Wheeled Terramechanics and Energetics Conclusions
• There is substantial amount of gain from using grousers. • There is not a substantial difference between different grouser heights • It is possible to achieve a positive draw bar pull for all wheel sizes and diameters on
flat terrain, on a slope, and going over 10cm obstacle with all wheels. • A large amount of power is required to overcome the resistance from these cases • It is not possible to achieve enough drawbar pull to go over a 50 cm obstacle,
assuming all wheels will encounter the obstacle at the same time, for reasonable size wheels.
• A wheeled system is not a good option FOR THIS APPLICATION unless: – A Lunar Monster Truck is created or – A system with more than 4 wheels and the same number of actuators (increased
mass and complexity) is produced or – An inefficiency in mobility is accepted or – An inefficiency in power consumption, hence operation time is accepted
• Therefore; need to look at: – Tracked vehicles to achieve larger drawbar pull and lower resistance (less power
use) – Clever concepts that would help overcome 50cm obstacles instead of large
wheels
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 28
Track-Wheel Hybrid System Terramechanics and Energetics
• Four two-wheel track system • Large wheel is attached to chassis and drives the system • Small wheel is free running and is ran by tracks. It is connected to the large wheel by
two beams (one on each Side) • The small wheel can be rotated about the center of the large wheel. • Grouser height used = 0.01m for all calculations • 10% of the total resistance has been added to all calculations as internal resistance to
accommodate for possible unknowns
Wheel 1Wheel 20.2 m
Rotate 360o
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 29
Track-Wheel Hybrid System – Draw Bar Pull – With Grousers
Flat Terrain 20o Slope
1600.00
1800.00
2000.00
2200.00
2400.00
2600.00
2800.00
3000.00
3200.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel 1 Diameter 0.03 mWheel 1 Diameter 0.04 mWheel 1 Diameter 0.05 mWheel 1 Diameter 0.06 mWheel 1 Diameter 0.07 mWheel 1 Diameter 0.08 mWheel 1 Diameter 0.09 mWheel 1 Diameter 1.0 m
0.00
500.00
1000.00
1500.00
2000.00
2500.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel 1 Diameter 0.03 mWheel 1 Diameter 0.04 mWheel 1 Diameter 0.05 mWheel 1 Diameter 0.06 mWheel 1 Diameter 0.07 mWheel 1 Diameter 0.08 mWheel 1 Diameter 0.09 mWheel 1 Diameter 1.0 m
10 cm Obstacle
1600.00
1700.00
1800.00
1900.00
2000.00
2100.00
2200.00
2300.00
2400.00
2500.00
2600.00
2700.00
2800.00
2900.00
3000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
TLR Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 30
Track-Wheel Hybrid – Draw Bar Pull – With Grousers
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
2200.00
2400.00
2600.00
2800.00
3000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
Only the Small Wheel Acting on the Obstacle
1600.00
1700.00
1800.00
1900.00
2000.00
2100.00
2200.00
2300.00
2400.00
2500.00
2600.00
2700.00
2800.00
2900.00
3000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Dra
w B
ar P
ull (
With
Gro
user
s) -
DP
g - (
N)
Wheel Diameter 0.03 mWheel Diameter 0.04 mWheel Diameter 0.05 mWheel Diameter 0.06 mWheel Diameter 0.07 mWheel Diameter 0.08 mWheel Diameter 0.09 mWheel Diameter 1.0 m
Both Small and the Large Wheel Acting on the Obstacle
50 cm ObstacleThrust Capacity
Tc1
Resistance R1
R2
Tc2
Thrust Capacity
Resistance
TLR Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 31
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
2200.00
2400.00
2600.00
2800.00
3000.00
3200.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel Diameter 0.30 mWheel Diameter 0.40 mWheel Diameter 0.50 mWheel Diameter 0.60 mWheel Diameter 0.70 mWheel Diameter 0.80 mWheel Diameter 0.90 mWheel Diameter 1.0 m
Track-Wheel Hybrid System – Power – With Grousers
Flat Terrain 20o Slope
10 cm Obstacle
0.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
4000.00
4500.00
5000.00
5500.00
6000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel 1 Diameter 0.30 mWheel 1 Diameter 0.40 mWheel 1 Diameter 0.50 mWheel 1 Diameter 0.60 mWheel 1 Diameter 0.70 mWheel 1 Diameter 0.80 mWheel 1 Diameter 0.90 mWheel 1 Diameter 1.0 m
0.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
4000.00
4500.00
5000.00
5500.00
6000.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Pow
er R
equi
red
- P -
(W)
Wheel 1 Diameter 0.30 mWheel 1 Diameter 0.40 mWheel 1 Diameter 0.50 mWheel 1 Diameter 0.60 mWheel 1 Diameter 0.70 mWheel 1 Diameter 0.80 mWheel 1 Diameter 0.90 mWheel 1 Diameter 1.0 m
TLR Performance is Highlighted
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 32
Wheel-Track Hybrid Terramechanics and Energetics Conclusions
• Wheel-Track hybrid is superior in all cases to a wheeled system • Wheel-Track hybrid system provides positive drawbar pull for all four cases. • Wheel-Track hybrid system requires significantly less power. • Wheel-Track hybrid system power requirements meet the Turtle average and
maximum power draw requirements for all three cases • The 50 cm obstacle is overcome by the design choice and
implementation: – Rotating the small wheel at an optimum angle to place on the 50cm obstacle and
driving over it – Leveraging the vehicle on front wheel to go over the obstacle or – Riding on the small wheel and rolling over the obstacle with the large ones
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 33
Wheel-Track Hybrid – Power Use• Requirements:
– Average power for Turtle driving system is 0.821 kW – Defined as operations over 3 days
– Maximum power draw for Turtle driving system is 6.19 kW – Allocated power for the driving system is 0.86 kW – Allocated power for the avionics is 0.59 kW in use, 0.2 kW in standby mode
• Based on the power calculations for a 1m diameter, 0.30m width wheel: – Turtle could support only ~6 hours of drive time a day on average (driving
half the time over 10cm obstacles half the time on flat terrain). • Tack Wheel Hybrid System:
– Nominal power usage: for flat terrain ~0.9 kW – Maximum power usage: for 10 cm obstacle is ~1.6 kW – Power usage for 20o slope is ~1.7 kW
• Based on the power calculations: – Track-Wheel hybrid system can support ~16 hours of drive time a day on
average (driving half the time over 10cm obstacles half the time on flat terrain or half time on slope) and almost continuously on flat terrain.
– This would allow for more autonomous applications and a larger range of operations from a base.
• The avionics power use is well below the 0.59 kW • There is 10% margin on all calculations for drawbar pull & power to account for
internal resistance or other unknownns
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 34
Track-Wheel Hybrid Mobility Unit - Details• Wheel:
– The wheel well is made out of titanium – Houses the in-hub motor – Interior is protected by a flexible cover to avoid dust collection on critical components
• Tire: – Modified Lunar Rover wheel construction:
• Thicker woven flexible steel mesh tires with titanium track engagement threads.
• Track: – Same construction as the tires.
• Thicker woven flexible steel mash with titanium grousers on the outer surface and titanium wheel engagement threads on the inner surface
* No CTE mismatch between tracks, tires, wheel wells, and the wheel connector bar * Tire can operate without the track in place in emergencies * Easily maintained - installed/removed, replaced - tracks
Titanium wheels
Steel Woven Mash Tires
Titanium Grousers
Titanium Track Engagement Threads
Steel Woven Mesh Track
Flexible Cover on both wheels
http
://ca
rsco
op.b
logs
pot.c
om/2
008/
04/o
ut-o
f-thi
s-w
orld
-goo
dyea
rs-p
roto
type
.htm
l
Small supporting rollers to distribute pressure evenly on the tracks between the wheels (not shown)
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 35
• CG – Nominal CG (x, y, z): (1.2, 1.3, 0.73) meters – Fluctuation (x, y, z): (±0.2, ±0.1, ±0) meters – Critical slope: 48◦
• TRADES – Cg height versus length of vehicle (flat terrain and 20۫ slope) – Vehicle width versus cg height, turning radius, and velocity (flat terrain
and 20◦ slope)
Stability
cg
x
cgz
yy
x
z
z
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 36
Stability – Flat Terrain – CG Location vs. Vehicle Length
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50
Vehicle Length Needed for Stability for flat terrain
CG
Hei
ght o
ff o
f the
Gro
und
(m)
Vehicle Length
1.33
TLR Limit
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 37
Stability – Slope – CG Location vs. Vehicle Length
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
Vehicle Length Needed for Stability for a 20 Degree Slope (m)
CG
Hei
ght o
ff o
f the
Gro
und
(m)
Vehicle Length
2.11
TLR Limit
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 38
Stability – Flat Terrain – Vehicle Width vs. Turning Radius and CG Height
00.10.20.30.40.50.60.70.80.9
11.11.21.31.41.51.61.71.81.9
22.12.22.32.42.5
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.0
0
11.0
0
12.0
0
13.0
0
14.0
0
15.0
0
Vehicle Width Needed for Stability, Velocity = 4.167 m/s
CG
Hei
ght o
ff of
the
Gro
und
(m)
Turning Radius: 2 mTurning Radius: 4 mTurning Radius: 6 mTurning Radius: 8 m2.77
7m Vehicle Width = 2.37
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 39
Stability – Slope – Vehicle Width vs. Turning Radius and CG Height
00.10.20.30.40.50.60.70.80.9
11.11.21.31.41.51.61.71.81.9
22.12.22.32.42.50.
00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
2.20
2.40
2.60
2.80
3.00
3.20
Vehicle Width Needed for Stability, Velocity = 1.388 m/s
CG
Hei
ght o
ff o
f the
Gro
und
(m)
Turning Radius: 2 mTurning Radius: 4 mTurning Radius: 6 mTurning Radius: 8 m
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 40
Stability• Breaking
– Main breaks: Disk breaks within each wheel. – Back up:
• Slow or stop the motor to come to a gradual stop. • Stop the motor and lock the tracks to come to a halt.
• Max Deceleration rate – Flat Terrain: 2.66 m/s2
– 20 ۫ slope: 1.94 m/s2
• Stopping distance (flat terrain and 20◦ slope) – Flat Terrain: 3.3 m – 20 ۫ slope: 0.50 m
• Stopping time (flat terrain and 20◦ slope) – Flat Terrain: 1.57 s – 20 ۫ slope: 0.72 s
http
://st
ores
.bra
kepl
anet
.com
/Item
s/nl
0328
28?s
ck=2
6119
013
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 41
Stability – Going Over Obstacles
Low CG and wide base contribute to stability in handling obstacles.
Rover Overturn Due to Collision With Immovable Obstacle
* Solid lines assume 5% energy lost at impact* Dashed lines assume 25% energy lost at impact
5
6
7
8
9
10
11
12
13
14
15
0.05 0.1 0.15 0.2 0.25 0.3
Obstacle Height [m]
Rov
er S
peed
[km
/hr]
Level Terrain5 deg slope10 deg slope15 deg slope20 deg slopeLevel Terrain5 deg slope10 deg slope15 deg slope20 deg slope
* Solid line denotes 5% energy dissipated at impact; dashed line denotes 25%
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 42
SteeringFlat Terrain 20o Slope
Skid Steering • The larger the track width the better the performance • Extra mass and complexity for actuators to steer is avoided • Zero turning radius at rest Steerability Criteria: Fo ≤ c b l +(w tan(Φ))/2 Steerability = (c b l +(w tan(Φ))/2) - Fo
0.00
100.00
200.00
300.00
400.00
500.00
600.00
700.00
800.00
900.00
1000.00
1100.00
1200.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55Wheel Width - b - (m)
Stee
rabi
lity
Wheel 1 Diameter 0.03 mWheel 1 Diameter 0.04 mWheel 1 Diameter 0.05 mWheel 1 Diameter 0.06 mWheel 1 Diameter 0.07 mWheel 1 Diameter 0.08 mWheel 1 Diameter 0.09 mWheel 1 Diameter 1.0 m
-300.00
-250.00
-200.00
-150.00
-100.00
-50.00
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
400.00
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Wheel Width - b - (m)
Stee
rabi
lity
Wheel 1 Diameter 0.03 mWheel 1 Diameter 0.04 mWheel 1 Diameter 0.05 mWheel 1 Diameter 0.06 mWheel 1 Diameter 0.07 mWheel 1 Diameter 0.08 mWheel 1 Diameter 0.09 mWheel 1 Diameter 1.0 m
V1 V2V
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 43
Suspension – Human Factors
Frequency (Hz) Effect0.05 – 2 Motion sickness, peak incidence occurs at ~0.17 Hz
1 – 3 Side-to-side and fore-and-aft bending resonances of the unsupported spine
2.5 – 5 Strong Vertical resonance in the vertebra of the neck and lower lumbar spine
4 – 6 Resonances in the trunk20 – 30 Resonances between head and shoulders
Up to 80 Hz Localised resonances of tissues and smaller bones
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 44
Suspension – TradeType Description Examples Advantages Disadvantages
Dependant • Movement of wheel on one side of the vehicle affects the movement of wheel on the other side of the axle. •Commonly used on commercial and off road vehicles.
• Hotchkiss (leaf springs) • Trailing arms • Leaf spring • 4-bar
• Simple to design • Low cost • Low mass
• Negatively affects ride and handling compared to independent systems
Semi-dependant
• Beam that can bend and flex
• Trailing twist axle • Simple to design • Design flexibility
Independent • Widely used today in the commercial vehicle industry
• Macpherson Strut • Double Wishbone • A-arm • Multi-link
• Better drive and handling over independent passive suspensions. • Design flexibility • Better reliability than active/semi-active. • Better cost and mass over active/semi-active
Semi-Active • Suspension dynamics change continuously but is not electronically monitored
• Hydropneumatic • Hydrolastic • Hydragas
• Continuous improvements to road handling and ride
• Cost and design maturity
Active • Electronic monitoring of vehicle conditions, coupled with the means to impact vehicle suspension.
• Bose Suspension • Active body control
• Continuous monitoring of vehicle motion for improved bounce, roll, pitch and wrap modes.
• Increase in cost and mass, negative affects to reliability, and design maturity
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 45
Suspension AnalysisNatural Frequency of the Wheel versus Spring Diameter
1.81.85
1.91.95
22.05
2.12.15
2.22.25
2.32.35
2.42.45
2.52.55
2.62.65
2.72.75
2.82.85
2.9
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.011
Spring Diameter (m)
Nat
ural
Fre
quen
cy (H
z)
Coil Diameter = 0.06mCoil Diameter = 0.08mCoil Diameter = 0.10mCoil Diameter = 0.12mCoil Diameter = 0.14m
Critical Distance of the Wheel versus Spring Diameter
11.05
1.11.15
1.21.25
1.31.35
1.41.45
1.51.55
1.61.65
1.71.75
1.81.85
1.91.95
22.05
2.12.15
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.011
Spring Diameter (m)
Cri
tical
Dis
tanc
e (m
)
Coil Diameter = 0.06mCoil Diameter = 0.08mCoil Diameter = 0.10mCoil Diameter = 0.12mCoil Diameter = 0.14m
Natural Frequency of the Suspension versus Spring Diameter
0.0000.0500.1000.1500.2000.2500.3000.3500.4000.4500.5000.5500.6000.6500.7000.7500.8000.8500.9000.9501.0001.0501.1001.150
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.011
Spring Diameter (m)
Nat
ural
Fre
quen
cy (H
z)
Coil Diameter = 0.06mCoil Diameter = 0.08mCoil Diameter = 0.10mCoil Diameter = 0.12mCoil Diameter = 0.14m
Critical Distance of the Suspension versus Spring Diameter
050
100150200250300350400450500550600650700750800850900950
10001050
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.011
Spring Diameter (m)
Cri
tical
Dis
tanc
e (m
)
Coil Diameter = 0.06mCoil Diameter = 0.08mCoil Diameter = 0.10mCoil Diameter = 0.12mCoil Diameter = 0.14m
Mass of Body
Mass of Wheel
MODEL
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 46
Suspension – Macpherson Strut
• Material: 2014-T6 • Density = 2800 kg/m3
• Modulus of Elasticity = 72.4 GPa • Poisson's Ratio = 0.33 • Bulk Modulus = 27.2 GPa
• Number of Coils: 7 • Coil diameter = 0.003 m • Spring diameter = 0.1 m • Length = 0.24 m • Ks = 40 N/m
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 47
Chassis AnalysisMaterial: AL 6061-T6
Density: 2700 kg/m3
Yield Strength: 310 Mpa
Ultimate Strength: 27 Mpa
Youngs Modulus (E): 69 Gpa
Poisson’s Ratio: 0.33
Axial Launch Load 6 g
Area Moment of Inertia (m): 8.33E-7
Critical Axial Load (N/m2): 1.52E+5
Safety Factor: 2.88
Margin: 180401.05%
Static Loads: 1 g
Area Moment of Inertia: 8.33E-7
Maximum Deflection (m): 0.005
Stress in Beam (N/m2): 2.05E+7
Max Sheer Stress (N/m2): 1.42E+3
Safety Factor: 13.42
Margin: 1242.01%
Lateral Launch Load: 2 g
Area Moment of Inertia: 8.33E-7
Maximum Deflection (m): 0.055
Stress in Beam (N/m2): 2.46E+8
Max Sheer Stress (N/m2): 1.70E+4
Safety Factor: 1.12
Margin: 11.61%
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 48
Chassis Dimensions
1.9 m
1.93 m 0.08 m
0.08 m
0.08 m
0.02 m
Mass: 90 kg
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 49
Track-Wheel Hybrid Mobility Unit – Wheel Connector Beam
Length of beam (m)
Maximum Deflection - Y
(m)Mass of
Beam (kg)
Maximum Stress in
Beam (N/m2)Safety
Factor (SF)
Desirable Angle to the 50 cm
Obstacle
Optimum Angle to the 10 cm
Obstacle
0.70 0.026 ~ 0.5 4.11E+08 ~ 2 34.85o 0.00o
• Wheel 1 Diameter: 0.6 m • Wheel 2 Diameter: 0.4 m • Material: Titanium (6% Al, 4% V) • Yield Strength: 1.05x1011
• Beam Thickness: 0.004 m • Beam Width: 0.06 m • Load Applied: ~ 734 N
0.6 m0.4 m0.2 m
Rotate 360o
0o point
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 50
Motors and Gearing – Design Space
Planetary Gear Systems
Harmonic Drives
Multi-Staged/ Combinations
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 51
Motors and Gearing – Motors Trade Space
Type Advantages Disadvantages Typical Application Typical Drive
Brushless DC Electric Motor
• Long lifespan • Low maintenance • High efficiency
• High initial cost • Requires a controller
• Hard drives • CD/DVD players • Electric vehicles
• Multiphase DC
Brushed DC Electric Motor
• Low initial cost • Simple speed control (Dynamo)
•High maintenance (brushes) • Low lifespan
• Treadmill • Exercisers • Automotive starters
• Direct (PWM)
AC Induction(Shaded Pole)
• Least expensive • Long life • High power
• Rotation slips from frequency • Low starting torque
• Fans • Uni/Poly-phase AC
AC Induction(Split-Phase Capacitor)
• High power • High starting torque
• Rotation slips from frequency • Appliances • Uni/Poly-phase
AC
AC Synchronous
• Rotation in-sync with freq • Long-life (alternator)
• More expensive• Clocks • Audio turntables • Tape drives
• Uni/Poly-phase AC
Stepper DC • Precision positioning • High holding torque
• Slow speed • Requires a controller
• Positioning in printers and floppy drives
• Multiphase DC
Motor Comparison, Circuit Cellar Magazine, July 2008, Issue 216, Bachiochi, p.78
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 52
Motors and Gearing – Legacy and Future Rovers
Mars Exploration Rover (180 kg)
Apollo Lunar Roving Vehicle (210 kg)
Mars Science Laboratory (900 kg)
Motors• Independently driven wheels; 28 VDC brushed motors • Identical motors used for steering front and rear wheels.
• Independently driven wheels; 36 VDC brushed motors
• Selected brushless DC motor; low temperature/low-mass gearbox. •• A failure in testing of the proposed dry lubrication to support motor actuator operations at very cold temperatures is contributing to MSL project delays. Gearing
• Two-stage planetary gearbox powers a harmonic drive. (1500:1)
• Harmonic drive (80:1)
Motors/Gearing for TLR will likely require significant R&D. Legacy and Future rovers provide a starting point for design/analysis.
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 53
Motors and Gearing – TLR Motors• The design for the drive system consists of tracks independently driven by brushless DC motors. • BluWav Systems has a line of DC brushless motors that show promise, though further R&D would be necessary.
The brushless DC motors were chosen for: • Low maintenance • High efficiency (>95%) • High reliability • High controller TRL (SAE J1939; RS-232/485)
These areas would need further R&D: • Gearing options (planetary vs. harmonic) • Lower power requirements • Minimum operating temperature range*
BluWav In-Hub Motorhttp://www.bluwavsystems.com/whitepapers/46kWHubMotor.pdf
* Note: a low-temperature failure in testing of the brushless DC motors is contributing to MSL project delays
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 54
Motors – Lifting the Vehicle About Small Wheels
• Use the in-hub motor to raise the small wheel while driving and to pivot about the small wheel to lift the vehicle
Gearing ratio and Torque Required: • Assuming even distribution of the weight over the four tracks…
– Each motor has to lift ~734 kg of mass • Moment arm about the small wheel = 0.7m • Torque required to lift wheel about the small wheel = ~514 Nm • Main motor torque = ~85 Nm • Gear ratio used = 8:1 • Torque generated = 680 Nm to lift the vehicle
Rotate about small wheel to lift vehicle
W 4 W
4
W 4
W 4
Rotate small wheel about large wheel to
change angle of approach
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 55
Design Details – Dimensions
2.6 m
2.1 m
0.3 m
1.9 m1.93 m3.1 m
1.87 m
0.30 m
0.60 m
0.40 m
y
x
z
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 56
Design Details – Dimensions
3.67 m
2.7 m
2.47 m
0.9 m
0.07 m
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 57
Design Details – Mobility ConfigurationsNominal Driving Configuration
• All four tracks flat on ground • Front and rear tracks at same configuration: Large rear and small front wheel
• Drive on Flat Terrain • Drive on slope
• Easily avoid nosing in
Other possible Configurations• Rear wheels can be rotated 180 from nominal condition to increase foot print
• Front wheels can be rotated 180 from nominal condition to decrease foot print • This would be the launch configuration
• Jamming is easily avoided in every configuration
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 58
Design Details – Mobility Configuration
• Each track can be adjusted to take on a different size obstacle at optimum angle of attack • Can adjust wheels to provide a level chassis in all directions up to 18.7o slope
• Used mainly for obstacles. • Main configuration to overcome the 50cm obstacle.
• All tracks can be configured to drive on the small wheel only.
• This method can be used to approach 50cm obstacle. After the approach the vehicle can roll over it while rotating the small wheels in the –X direction.
• Easily avoid bottoming out on obstacles less than 0.9m tall
Other Possible Configurations
θ
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 59
Operations – Logic DiagramInitialize
OperationsUse Sensors and
Imaging to Generate Map
Calculate Path
Nominal Driving Condition Tracks are flat to ground
Detect Obstacles Detect Slopes
Every 15 seconds Compare to previous Categorize obstacle height Categorize slope angle
No Obstacle in Path No Slopes in Path
Increase Speed to 15 km/hr
Obstacle in Path Change Angle of ApproachObstacle ≤ 10cm
1 2 3 4 5 6
Lower Speed to 7.5 km/hr
7
1
3
4 Obstacle in Path 10 cm ≤ Obstacle < 30cm Change Angle of Approach
Lower Speed to 5 km/hr
Obstacle in Path Obstacle > 50cm2 Re-plan path to Avoid Obstacle
Operate on Flat Terrain
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 60
Operations – Logic DiagramOperating on Flat Terrain
Use Sensors and Imaging to
Generate MapCalculate Path
Nominal Driving Condition Tracks are flat to ground 15 km/hr velocity
Detect Obstacles Detect Slopes
Every 15 seconds Compare to previous
1 2 3 4 5 6 7
5 Obstacle in Path 30 cm ≤ Obstacle ≤ 50cm
Change Angle of Approach
Come to a Stop
A Climb and Drive Over the Obstacle
Lift Vehicle onto Small WheelsC Approach
Obstacle
Roll Large Wheels Onto the Obstacle
Rotate Small Wheels Back
Change Angle of ApproachB Place Small Wheels
Onto the ObstacleLift Vehicle, Level off,
and Drive Forward
Drive Over the Obstacle with Large Wheels
in Front Small Wheels in Back
A B C
Categorize obstacle height Categorize slope angle
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 61
Operations – Logic DiagramOperating on Flat Terrain
Use Sensors and Imaging to
Generate MapCalculate Path
Nominal Driving Condition Tracks are flat to ground 15 km/hr velocity
Detect Obstacles Detect Slopes
Every 15 seconds Compare to previous
1 2 3 4 5 6 7
6 Slope in Path Slope > 20o
Categorize obstacle height Categorize slope angle
Re-plan path to Avoid Slope
7 Slope in Path Slope ≤ 20o
Keep Nominal Driving Condition B Approach Slope
and Climb
Keep Nominal Driving Condition A Approach Slope
And Start ClimbLift Vehicle Onto
Small Wheels Partially to Keep Vehicle Level
A B
θ
θ
Lower Speed to 5 km/hr
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 62
Sensors – Obstacle Detection and Avoidance
• The scanning LIDAR (Light Detection And Ranging) will be the rover’s obstacle detection system.
• It is a rotating unit which utilized multiple LIDAR sensors. • All of the sensors measure the distance to surrounding objects and altitude of terrain while rotating. • This scan will be done once every 15 seconds so that the rover will stay updated on passable paths.
• TLR will also employ cameras for remote control applications
Some benefits of the scanning LIDAR are:
• 360 degree field of view (compared to RADAR and Stereo vision which have only 10 and 90 degrees field of view)
• Maps output to navigation computers which generate drive and steering commands to go around obstacles (necessary for rover requirements)
• Capable of operating at night and permanent shadowed regions (many on lunar surface) http://www.cowi.com/menu/services/society/mappingandgeodata/laserscanning/Pages/laserscanning.aspx
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 63
Sensors – Odometry SystemDead Reckoning • Deduce position after moving for a known time at a known direction with a known velocity
Forward Motion: ∆d(p) = fd(∆d1(p), …, ∆dn(p), ∆β1(p), …, ∆βn(p))
Angular Motion: ∆β(p) = fβ(∆d1(p), …, ∆dn(p), ∆β1(p), …, ∆βn(p))
where n = number of wheels
∆β(p)
∆d(p)
P P+1
We want to obtain position P+1 from the position at P
The difference ∆x(p) = x(p+1) – x(p) may be deduced from ∆d(p), ∆β(p)
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 64
Sensors – Angular Positioning Sensors
r
Forward motion may be measured by a sensor by multiplying wheel radius r by
angular motion
The transversal angle of angular motion may be measured with a sensor
(for wheels and robotic arm)
Sensor options for angular positioning are:Sensor Advantage Disadvantage
Potentiometer Low cost and simple interface Easily dirty and sensible to noise
Synchros/Resolvers Easily mounted, can withstand extreme environments Require AC signal source, heavy
Optical encoders Higher resolution, digital High cost, not very robust* Incremental optical encoders will be used for TLR’s angular positioning sensors
∆d(p)
∆β(p)
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 65
Sensors – Guidance Sensors• Odometry is not very reliable • TLR also is equipped with sensors:
• To detect heading • Orientation • Inclination.
• TLR will employ rate sensors, gyroscopes and accelerometers integrated into an Inertial Measurement Unit (IMU) will cover this.
IMU provides attitude and acceleration information during surface operations and convert to outputs used by vehicle control systems for guidance
Yaw
RollPitch
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 66
Mapping• Local map will be created using fixed decomposition with LIDAR
system. • Position and ranging will be updated with 75 meter range accuracy.
• Continuous representation method not preferred for lunar exploration due to 3D surface obstacle and slope concerns. (only good for 2D representation)
• Occupancy grid will be updated using Bayesian method.
• Since Lidar scan will occur every 15 seconds it is safe and effective to update map using this technique.
P(A| not B) =P(not B|A)P(A)
P(not B|A)P(A)+P(not B| not A)P(not A)
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 67
Command and Control3 RAD750 radiation hardened single board computers will be used
to:
• Format and process navigation data for output • Process path commands from the autonomous driving computer • Command the rover through passable paths • Build and output range maps to the autonomous driving computer.
http://www.corelis.com/images/BAE-RAD750-board.jpg
http://www.maxwell.com/images/me/_sbc/scs750d_press.jpg6
BAE Systems RAD750
Maxwell Technologies SCS750
* A maximum of 5 watts of power are required for each 133 mHz RAD750 computer
1 SCS750 high space-qualified super computers will be used to:
• Rover’s autonomous driving computer • Used to compute passable paths for rover to follow
* A maximum of 20 watts of power are required for each 800 mHz SCS750 computer
* Maximum of 35 watts processing for entire rover computer system
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 68
Command and Control
SCS750 RAD750Path Commands
Range Maps
COMPUTING
IMU
Attitude and Acceleration
Optical Encoders
Angular Position
Motor Commands based off possible paths
Motor Controllers
• IMU, optical encoders, and Lidar sensors will provide computers with position information. • Computing will be programmed based off rover surface requirements. • Motor controllers will be updated based off computer processing.
LIDAR
Obstacle Ranging
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 69
Mass Budget
Total Mass: ~723 kg (11% margin)
Mass [kg] Number Total [kg]
Wheel-Track System 152.6 1 152.6
Large wheels 13.93 4 55.72
Small wheels 9.29 4 37.16
Arm 0.5 8 4
Track 13.93 4 55.72
Suspension & Breaking Systems 50 1 50
Motors & Gears 360 1 360
Motors & Gearing - drive 45 4 180
Motors & Gearing - arm control 45 4 180
Structure 90 1 90
Sensors 29 2 58
Cameras 3 2 6
Data management hardware 3 2 6
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 70
ReliabilityReliability for Loss of Mission: 0.9930
Reliability for Loss of Crew: 0.9977Reliability Number Total [kg]
Wheel-Track System 0.9988 1 0.9988
Large wheels 0.9999 4 0.9996
Small wheels 0.9999 4 0.9996
Arm 0.9999 4 0.9996
Suspension & Breaking Systems 0.999 1 0.999
Structure 0.9999 1 0.9999
Reliability Number Total [kg]
Wheel-Track System 0.9960 1 0.9960
Track 0.999 4 0.9960
Motors & Gears* 0.9920 1 1.0000
Motors & Gearing - drive 0.999 4 0.9960
Motors & Gearing - arm control 0.999 4 0.9960
Sensors 0.999 2 0.999
Cameras 0.999 2 0.999
Data management hardware 0.999 2 0.999
Note that high reliability for extended periods requires performance of preventive maintenance and inspections between sorties
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 71
Fault Tolerance• Drive motors and arm control motors provide redundancy
– They are cross-strapped. If one fails the other can operate both.
• Contingency operation possible after track malfunction using wheels
• Significant safety margin (minimum of 12%) in structural calculations
• Manual controls available in the event of a failure of the autonomous control system
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 72
Earth Analog Considerations• Braking characteristics for 1-G trainer should be “tune”-able to emulate
braking conditions on moon… stopping distance on the moon is six times the stopping distance on Earth
• Turning radius of the 1-G trainer should be modified to emulate the turning radius of the TLR (you need a turn radius six times larger one the Moon than on Earth to maintain the same amount of lateral stability)
• Natural frequency for the suspension decreases… dcrit on the moon is ~5.5m as opposed to ~2m on Earth
• Rollover due to obstacle impact at velocity is lessened in 1-G… the 1-G trainer will have sensors to indicate if a driver’s technique would have resulted in rollover on the moon
• The 1-G trainer should be “equipped with removable seat pads which allow comfortable operation in a ‘shirt sleeve’ training session”
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 73
Possible Improvements to TLR – Future Expansion Possibilities for the Mobility Unit –
• Each two track segment can be designed to operate as a single system – Need redundancy on power, mobility controls, and sensor systems. – Critical systems mentioned above needs to be supported between the two wheels
and not the capsule – Easy to attach/detach docking to the capsules is needed – No need for stabilization for flat terrain and certain slopes
• Possible Utilization: – Each two track system can mobilize independently to support different tasks – Two systems can pick up and drop capsules autonomously to support a lunar
base (no need for multiple capsules with dedicated rover capabilities) – The system can be used independently by astronauts in case of an emergency
* If certain units can be separated from the capsule, with a clever design such a vehicle can be created with little mass, power, and budget impact to what has already been designed.
Tracks as designed in this system
Critical systems separated from the capsule and packaged on the wheels. (power, mobility controls, sensors…)Simple platform to support
manned transport
Suspension as designed in this system
View From Top
12/11/2008
ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 74
References• [Apollo] Lunar Roving Vehicle Operations Handbook. April 19,1971. • Traction Drive System Design Considerations for a Lunar Roving
Vehicles. November 25, 1969. • Digging and Pushing Lunar Regolith: Classical Soil Mechanics and
the Forces Needed for Excavation and Traction. Wilkinson and DeGennaro. September 7, 2006. • High Speed Craft Human Factors Engineering Design Guide. Human Sciences & Engineering Ltd. January 31, 2008. • Human Spaceflight: Mission Analysis and Design. Larson and
Pranke.
12/11/2008