Case Study: Term Project

Case Study: Term Project • Expectations for the term project • An example of a previous term project • Quickie assignment – one person from each team go on Zoom chat right now and list the names of the members of your team, and also your team name if you’ve selected it

© 2020 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 1 2020 Design Project Statement • Perform a detailed design of a BioBot 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 for this class - but it will be built during the Spring term!

U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 2 Level 1 Requirements (Performance) 1. Rover shall have a maximum operating speed of at least 4 m/sec on level, ﬂat terrain. 2. Rover shall be designed to accommodate a 0.3 meter obstacle at minimal velocity. 3. Rover shall be designed to accommodate a 0.1 m obstacle at a velocity of 2.5 m/sec. 4. Rover shall be designed to safely accommodate a 20° slope in any direction at a speed of at least 1 m/sec and including the ability to start and stop. 5. The rover shall have a nominal sortie range of 54 km at an average speed of 2.5 m/sec. U N I V E R S I T Y O F Course Overview ENAE 788X - Planetary Surface Robotics MARYLAND 3 Level 1 Requirements (Payload) 6. Rover shall be capable of carrying one 170 kg EVA crew and 80 kg of assorted payload in nominal conditions. 7. Payload may be modeled as a 0.25 m3 box 8. Rover shall be capable of also carrying a second 170 kg EVA crew in a contingency situation. Payload may be jettisoned if design permits. 9. Rover design shall incorporate roll-over protection for the crew and all required ingress/egress aids and crew restraints.

U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 4 Level 1 Requirements (Operations) 10.A nominal sortie shall be at least eight hours long. 11.Two rovers must be launched on a single CLPS lander. 12.A single rover shall mass ≤250 kg. 13.Rovers shall be developed in time to be used on the ﬁrst Artemis landing mission. 14.Rover shall be capable of operating indeﬁnitely without crew present.

U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 5 Level 1 Requirements (GN&C) 15.Rover shall be be capable of being controlled directly, remotely, or automated. 16.Rover shall be capable of following an astronaut, following an astronaut’s path, or autonomous path planning between waypoints. 17.Rover shall be capable of operating during any portion of the lunar day/night cycle and at any latitude.

U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 6 Final Project Expectations • Final design of rover – Solid models of design – Design evolution throughout 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) U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 7 Final Design Expectations (2) • Vehicle stability – Slope (up, down, cross) – Acceleration/deceleration – Turning – Combinations of above • Terrain ability (“trafﬁcability”) – Weight transfer over obstacles – Climbing/descending vertical or inclined planes – Hang-up limit (e.g., high-centering, wheel capture)

U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 8 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

U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 9 Final Project Presentations • Monday, Dec. 7, and Wednesday, Dec. 9 • Each final project will have 25 minutes for a class presentation • All teams should submit their slides prior to class on Dec. 7 (submit as both powerpoint and pdf) • Slide deck should be comprehensive and reflect all of your work - slides which can’t be presented in the time allotted should be included as backup • Would also like to collect model files created during the course – details TBD U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 10 Interim Project Progress Report • Due Wednesday, Oct. 28 • Format: presentation slides showing work to date • Submitted electronically and presented in class (10 minutes/group) • Would like to see solid progress and use of concepts from lectures to date • Certainly expect to see basic rover concept, trade studies leading to configuration choices (number and sizes of wheels, general configuration) • Opportunity to see other designs and interact U N I V E R S I T Y O F Case Study: Final Design Project ENAE 788X - Planetary Surface Robotics MARYLAND 11 Terrestrial Lunar Rover (TLR)

ENAE788X Planetary Surface Robotics Design Project

Team Members Cagatay Aymergen • Jignasha Patel Syed Hasan • John Tritschler 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 13 Project Requirements & Specifications

• 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

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 14 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 15 Concepts Explored

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 16 Concepts Explored

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 17 TLR Design Overview • 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

Supported Payload Accommodates All Sensors and Avionics

Aluminum Chassis

Suspension System 4 Track-Wheel Hybrid Mobility Unit Wheel to Chassis Connection

Large Wheel Driving Wheel Small Wheel Houses the Motors Tracks Wheel Connector Bar Free Running

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 18 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 19 Wheeled System – Draw Bar Pull – No Grousers

Flat Terrain Turtle Performance is Highlighted 20o Slope 2000.00 800.00

1800.00 600.00 1600.00 400.00 1400.00 200.00 1200.00 - ( N )

P - ( N ) 0.00 1000.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55

) - D P -200.00 800.00 r s ) - D e e r s

600.00 -400.00 r a u s

400.00 -600.00 ( N o G r a u s

200.00 -800.00 r P u l ( N o G Wheel Diameter 0.30 m 0.00 4 wheels -1000.00 Wheel Diameter 0.40 m w B a 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 -200.00 Wheel Diameter 0.50 m D r a w B P u l D r a -1200.00 Wheel Diameter 0.60 m -400.00 Wheel Diameter 0.70 m Wheel Diameter 0.30 m Wheel Diameter 0.40 m -1400.00 -600.00 Wheel Diameter 0.50 m Wheel Diameter 0.60 m Wheel Diameter 0.80 m Wheel Diameter 0.70 m Wheel Diameter 0.80 m Wheel Diameter 0.90 m Wheel Diameter 0.90 m Wheel Diameter 1.0 m -1600.00 -800.00 Wheel Diameter 1.0 m -1000.00 -1800.00 Wheel Width - b - (m) Wheel Width - b - (m)

2000.00 800.00

1800.00 600.00

1600.00 400.00 1400.00 200.00 1200.00 - ( N )

P - ( N ) 0.00 1000.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55

) - D P -200.00 800.00 r s ) - D e e r s 600.00 -400.00 r a u s

400.00 -600.00 ( N o G r a u s

200.00 -800.00

r P u l ( N o G Wheel Diameter 0.30 m

6 wheels 0.00 -1000.00 Wheel Diameter 0.40 m w B a 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 -200.00 Wheel Diameter 0.50 m D r a w B P u l D r a -1200.00 Wheel Diameter 0.60 m -400.00 Wheel Diameter 0.70 m Wheel Diameter 0.30 m Wheel Diameter 0.40 m -1400.00 -600.00 Wheel Diameter 0.50 m Wheel Diameter 0.60 m Wheel Diameter 0.80 m Wheel Diameter 0.70 m Wheel Diameter 0.80 m -1600.00 Wheel Diameter 0.90 m Wheel Diameter 0.90 m Wheel Diameter 1.0 m -800.00 Wheel Diameter 1.0 m -1000.00 -1800.00 Wheel Width - b - (m) Wheel Width - b - (m)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 20 Wheeled System – Draw Bar Pull – With Grousers

Flat Terrain Turtle Performance is Highlighted 20o Slope 3200.00 2300.00

3000.00 2100.00

2800.00 1900.00 2600.00 1700.00

g - ( N ) 2400.00 1500.00 2200.00 ) - D P g ( N

r s ) - D P 1300.00 r s e

2000.00 e 1100.00 1800.00 900.00 1600.00 ( W i t h G r o u s

1400.00 Wheel Diameter 0.03 m 700.00 Wheel Diameter 0.04 m P u l ( W i t h G r o s

4 wheels 1200.00 500.00 Wheel Diameter 0.03 m Wheel Diameter 0.04 m Wheel Diameter 0.05 m Wheel Diameter 0.05 m Wheel Diameter 0.06 m Wheel Diameter 0.06 m D r a w B P u l 1000.00 300.00 Wheel Diameter 0.07 m Wheel Diameter 0.08 m Wheel Diameter 0.07 m D r a w B Wheel Diameter 0.09 m Wheel Diameter 0.10 m 800.00 Wheel Diameter 0.08 m 100.00 Wheel Diameter 0.09 m 600.00 Wheel Diameter 1.0 m -100.000.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 400.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 -300.00 Wheel Width - b - (m) Wheel Width - b - (m)

3200.00 2300.00

3000.00 2100.00

2800.00 1900.00 2600.00 1700.00

g - ( N ) 2400.00 1500.00 2200.00 ) - D P g ( N r s ) - D P s 1300.00 e r

2000.00 e 1100.00 1800.00

1600.00 900.00 ( W i t h G r o u s

1400.00 Wheel Diameter 0.03 m 700.00 P u l ( W i t h G r o s Wheel Diameter 0.04 m 6 wheels 1200.00 500.00 Wheel Diameter 0.03 m Wheel Diameter 0.04 m Wheel Diameter 0.05 m Wheel Diameter 0.05 m Wheel Diameter 0.06 m Wheel Diameter 0.06 m D r a w B P u l 1000.00 300.00 Wheel Diameter 0.07 m Wheel Diameter 0.08 m Wheel Diameter 0.07 m D r a w B Wheel Diameter 0.09 m Wheel Diameter 0.10 m 800.00 Wheel Diameter 0.08 m 100.00 Wheel Diameter 0.09 m 600.00 Wheel Diameter 1.0 m -100.000.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 400.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 -300.00 Wheel Width - b - (m) Wheel Width - b - (m)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 21 Wheeled System – Obstacles – Draw Bar Pull – With Grousers

10 cm Obstacle Turtle Performance is Highlighted 50 cm Obstacle -1300.00 1900.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 1700.00 1500.00 -1350.00 1300.00 1100.00

g - ( N ) g - ( N ) -1400.00 900.00 700.00 r s ) - D P r s ) - D P e 500.00 e -1450.00 300.00 100.00 -1500.00 ( W i t h G r o u s -100.00 ( W i t h G r o u s 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 -300.00 Wheel Diameter 0.03 m Wheel Diameter 0.03 m 4 wheels -500.00 Wheel Diameter 0.04 m -1550.00 Wheel Diameter 0.04 m Wheel Diameter 0.05 m Wheel Diameter 0.05 m -700.00 D r a w B P u l Wheel Diameter 0.06 m D r a w B P u l Wheel Diameter 0.06 m -900.00 Wheel Diameter 0.07 m Wheel Diameter 0.07 m -1600.00 -1100.00 Wheel Diameter 0.08 m Wheel Diameter 0.08 m Wheel Diameter 0.09 m Wheel Diameter 0.09 m -1300.00 Wheel Diameter 1.0 m Wheel Diameter 1.0 m -1500.00 -1650.00 Wheel Width - b - (m) Wheel Width - b - (m)

-1250.00 1900.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 1700.00 1500.00 -1300.00 1300.00 1100.00 g - ( N ) g - ( N ) 900.00 -1350.00 700.00 r s ) - D P r s ) - D P e e 500.00

300.00 -1400.00 100.00 ( W i t h G r o u s ( W i t h G r o u s -100.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 -300.00 Wheel Diameter 0.03 m -1450.00 Wheel Diameter 0.03 m 6 wheels -500.00 Wheel Diameter 0.04 m Wheel Diameter 0.04 m Wheel Diameter 0.05 m Wheel Diameter 0.05 m

-700.00 D r a w B P u l D r a w B P u l Wheel Diameter 0.06 m Wheel Diameter 0.06 m -900.00 Wheel Diameter 0.07 m -1500.00 Wheel Diameter 0.07 m -1100.00 Wheel Diameter 0.08 m Wheel Diameter 0.08 m Wheel Diameter 0.09 m Wheel Diameter 0.09 m -1300.00 Wheel Diameter 1.0 m Wheel Diameter 1.0 m -1500.00 -1550.00 Wheel Width - b - (m) Wheel Width - b - (m)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 22 Wheeled System – Obstacles – Draw Bar Pull – With Grousers

50 cm Obstacle On All Wheels 50 cm Obstacle On Two wheels 600.00 1800.00

400.00 1600.00

200.00 1400.00 0.00 g - ( N )

g - ( N ) 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 1200.00 -200.00 r s ) - D P e r s ) - D P e -400.00 1000.00

-600.00 800.00 ( W i t h G r o u s

( W i t h G r o u s -800.00 600.00 -1000.00 Wheel Diameter 1.0 m Wheel Diameter 1.0 m 4 wheels Wheel Diameter 1.1 m Wheel Diameter 1.1 m 400.00 Wheel Diameter 1.2 m

-1200.00 Wheel Diameter 1.2 m D r a w B P u l

D r a w B P u l Wheel Diameter 1.3 m Wheel Diameter 1.3 m -1400.00 Wheel Diameter 1.4 m Wheel Diameter 1.4 m 200.00 Wheel Diameter 1.5 m Wheel Diameter 1.5 m -1600.00 Wheel Diameter 1.6 m Wheel Diameter 1.6 m Wheel Diameter 1.7 m 0.00 Wheel Diameter 1.7 m -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) Wheel Width - b - (m)

600.00 2400.00

400.00 2200.00

200.00 2000.00

0.00 1800.00 g - ( N )

g - ( N ) 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 1600.00 -200.00 r s ) - D P e r s ) - D P 1400.00 e -400.00

1200.00 -600.00

( W i t h G r o u s 1000.00

( W i t h G r o u s -800.00 800.00 -1000.00 Wheel Diameter 1.0 m Wheel Diameter 1.0 m 6 wheels Wheel Diameter 1.1 m 600.00 Wheel Diameter 1.1 m Wheel Diameter 1.2 m Wheel Diameter 1.2 m

-1200.00 D r a w B P u l

D r a w B P u l Wheel Diameter 1.3 m 400.00 Wheel Diameter 1.3 m -1400.00 Wheel Diameter 1.4 m Wheel Diameter 1.4 m Wheel Diameter 1.5 m 200.00 Wheel Diameter 1.5 m -1600.00 Wheel Diameter 1.6 m Wheel Diameter 1.6 m Wheel Diameter 1.7 m 0.00 Wheel Diameter 1.7 m -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) Wheel Width - b - (m)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 23 Wheeled System – Power – With Grousers

Flat Terrain Turtle Performance is Highlighted 20o Slope 11000.00 3700.00 10500.00 Wheel Diameter 0.30 m Wheel Diameter 0.30m 10000.00 Wheel Diameter 0.40 m 3500.00 Wheel Diameter 0.40m 9500.00 Wheel Diameter 0.50 m Wheel Diameter 0.50m 9000.00 Wheel Diameter 0.60 m 3300.00 Wheel Diameter 0.60m 8500.00 Wheel Diameter 0.70 m Wheel Diameter 0.70m 8000.00 Wheel Diameter 0.80 m 3100.00 Wheel Diameter 0.80m 7500.00 Wheel Diameter 0.90 m Wheel Diameter 0.90m 7000.00 Wheel Diameter 1.0 m 2900.00 Wheel Diameter 0.10m - ( W ) 6500.00 - ( W ) d - P 6000.00 d - P 2700.00 5500.00 q u i r e 5000.00 q u i r e 2500.00 4500.00 e r R e r R 4000.00 2300.00 P o w 3500.00 P o w 4 wheels 3000.00 2100.00 2500.00 2000.00 1900.00 1500.00 1000.00 1700.00 500.00 0.00 1500.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 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) Wheel Width - b - (m)

11000.00 3700.00 10500.00 Wheel Diameter 0.30 m Wheel Diameter 0.30m 10000.00 Wheel Diameter 0.40 m 3500.00 Wheel Diameter 0.40m 9500.00 Wheel Diameter 0.50 m Wheel Diameter 0.50m 9000.00 Wheel Diameter 0.60 m 3300.00 Wheel Diameter 0.60m 8500.00 Wheel Diameter 0.70 m Wheel Diameter 0.70m 8000.00 Wheel Diameter 0.80 m 3100.00 Wheel Diameter 0.80m 7500.00 Wheel Diameter 0.90 m Wheel Diameter 0.90m 7000.00 Wheel Diameter 1.0 m 2900.00 Wheel Diameter 0.10m - ( W ) - ( W ) 6500.00 d - P d - P 6000.00 2700.00 5500.00 q u i r e q u i r e 5000.00 2500.00 4500.00 e r R e r R 4000.00 2300.00 P o w P o w 3500.00 6 wheels 3000.00 2100.00 2500.00 2000.00 1900.00 1500.00 1000.00 1700.00 500.00 0.00 1500.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 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) Wheel Width - b - (m)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 24 Wheeled System – Obstacles – Power 10 cm Obstacle 11000.00 Wheel Diameter 0.30m 10500.00 Wheel Diameter 0.40m 10000.00 Wheel Diameter 0.50m 9500.00 Wheel Diameter 0.60m 9000.00 Wheel Diameter 0.70m 8500.00 Wheel Diameter 0.80m Turtle Performance is Highlighted 8000.00 Wheel Diameter 0.90m 7500.00 Wheel Diameter 1.0 m 7000.00 - ( W ) 6500.00

d - P 6000.00 5500.00 q u i r e

4 wheels 5000.00 4500.00 e r R 4000.00

P o w 3500.00 11000.00 3000.00 Wheel Diameter 0.30m 10500.00 2500.00 Wheel Diameter 0.40m 10000.00 2000.00 Wheel Diameter 0.50m 9500.00 1500.00 Wheel Diameter 0.60m 9000.00 1000.00 Wheel Diameter 0.70m 8500.00 500.00 Wheel Diameter 0.80m 8000.00 0.00 Wheel Diameter 0.90m 7500.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 Wheel Diameter 1.0 m 7000.00 Wheel Width - b - (m) - ( W ) 6500.00

d - P 6000.00 5500.00 q u i r e 5000.00 4500.00 e r R 4000.00

P o w 3500.00 3000.00 2500.00 2000.00 1500.00 1000.00 6 wheels 500.00 0.00 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)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 25 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 26 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

Rotate 360o

Wheel 2 Wheel 1 0.2 m

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 27 Track-Wheel Hybrid System – Draw Bar Pull – With Grousers

Flat Terrain TLR Performance is Highlighted 20o Slope 3200.00 2500.00

3000.00

2000.00 2800.00 g - ( N ) g - ( N )

2600.00 r s ) - D P r s ) - D P 1500.00 e e

2400.00 ( W i t h G r o u s ( W i t h G r o u s 1000.00 2200.00 Wheel 1 Diameter 0.03 m Wheel 1 Diameter 0.03 m Wheel 1 Diameter 0.04 m Wheel 1 Diameter 0.04 m Wheel 1 Diameter 0.05 m Wheel 1 Diameter 0.05 m 2000.00 Wheel 1 Diameter 0.06 m Wheel 1 Diameter 0.06 m D r a w B P u l D r a w B P u l 500.00 Wheel 1 Diameter 0.07 m Wheel 1 Diameter 0.07 m Wheel 1 Diameter 0.08 m 1800.00 Wheel 1 Diameter 0.08 m Wheel 1 Diameter 0.09 m Wheel 1 Diameter 0.09 m Wheel 1 Diameter 1.0 m Wheel 1 Diameter 1.0 m 1600.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 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) Wheel Width - b - (m)

3000.00

2900.00

2800.00

2700.00

g - ( N ) 2600.00

2500.00 r s ) - D P 10 cm Obstacle e 2400.00 2300.00

2200.00 ( W i t h G r o u s

2100.00 Wheel Diameter 0.03 m Wheel Diameter 0.04 m 2000.00 Wheel Diameter 0.05 m Wheel Diameter 0.06 m

D r a w B P u l 1900.00 Wheel Diameter 0.07 m 1800.00 Wheel Diameter 0.08 m Wheel Diameter 0.09 m 1700.00 Wheel Diameter 1.0 m 1600.00 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)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 28 Track-Wheel Hybrid – Draw Bar Pull – With Grousers

TLR Performance is Highlighted 50 cm Obstacle 3000.00 Thrust Capacity 2800.00 Tc1 2600.00

2400.00 Resistance

2200.00 Tc2 R1 g - ( N ) 2000.00

r s ) - D P 1800.00 R2 e Both Small and the Large Wheel 1600.00 Acting on the Obstacle 1400.00 3000.00

( W i t h G r o u s 1200.00 2900.00 Wheel Diameter 0.03 m 1000.00 2800.00 Wheel Diameter 0.04 m 800.00 2700.00 Wheel Diameter 0.05 m Wheel Diameter 0.06 m D r a w B P u l

600.00 g - ( N ) 2600.00 Wheel Diameter 0.07 m 400.00 2500.00 Wheel Diameter 0.08 m

r s ) - D P Wheel Diameter 0.09 m 200.00 e 2400.00 Wheel Diameter 1.0 m 0.00 2300.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 2200.00 Wheel Width - b - (m( W i t h G r o u s )

2100.00 Wheel Diameter 0.03 m Only the Small Wheel Acting on Wheel Diameter 0.04 m 2000.00 the Obstacle Wheel Diameter 0.05 m Wheel Diameter 0.06 m

D r a w B P u l 1900.00 Wheel Diameter 0.07 m Thrust Capacity 1800.00 Wheel Diameter 0.08 m Wheel Diameter 0.09 m 1700.00 Resistance Wheel Diameter 1.0 m 1600.00 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)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 29 Track-Wheel Hybrid System – Power – With Grousers

Flat Terrain TLR Performance is Highlighted 20o Slope 6000.00 6000.00 Wheel 1 Diameter 0.30 m Wheel 1 Diameter 0.30 m 5500.00 Wheel 1 Diameter 0.40 m 5500.00 Wheel 1 Diameter 0.40 m Wheel 1 Diameter 0.50 m Wheel 1 Diameter 0.50 m 5000.00 Wheel 1 Diameter 0.60 m 5000.00 Wheel 1 Diameter 0.60 m Wheel 1 Diameter 0.70 m Wheel 1 Diameter 0.70 m 4500.00 Wheel 1 Diameter 0.80 m 4500.00 Wheel 1 Diameter 0.80 m Wheel 1 Diameter 0.90 m Wheel 1 Diameter 0.90 m 4000.00 4000.00 Wheel 1 Diameter 1.0 m Wheel 1 Diameter 1.0 m - ( W ) - ( W ) 3500.00 3500.00 d - P d - P 3000.00 3000.00 q u i r e q u i r e

2500.00 2500.00 e r R e r R P o w 2000.00 P o w 2000.00

1500.00 1500.00

1000.00 1000.00

500.00 500.00

0.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 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) Wheel Width - b - (m)

3200.00 Wheel Diameter 0.30 m 3000.00 Wheel Diameter 0.40 m 2800.00 Wheel Diameter 0.50 m Wheel Diameter 0.60 m 2600.00 Wheel Diameter 0.70 m 2400.00 Wheel Diameter 0.80 m 2200.00 Wheel Diameter 0.90 m Wheel Diameter 1.0 m 2000.00 - ( W ) 1800.00 10 cm Obstacle d - P 1600.00 q u i r e 1400.00

e r R 1200.00

P o w 1000.00

800.00

600.00

400.00

200.00

0.00 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)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 30 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 31 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 32 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 http://carscoop.blogspot.com/2008/04/out-of-this-world-goodyears-prototype.html * 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

Small supporting rollers to distribute pressure evenly on the tracks between the wheels (not shown)

Steel Woven Mesh Track Titanium wheels Titanium Grousers Flexible Cover on both wheels Steel Woven Mash Tires Titanium Track Engagement Threads

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 33 Stability

• 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◦

cg cg x z z

y z x y • 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)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 34 Stability – Flat Terrain – CG Location vs. Vehicle Length

2.6

2.4

2.2

1.8 ) m (

n 1.6 TLR Limit u o r G

e 1.4 h t

f o

f 1.2 o

t h g i

e 1 H

C 0.8

0.6

0.4 Vehicle Length 0.2

0 0.00 0.50 1.00 1.33 1.50 2.00 2.50 3.00 3.50 4.00 4.50 Vehicle Length Needed for Stability for flat terrain

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 35 Stability – Slope – CG Location vs. Vehicle Length

2.6

2.4

2.2

1.8 ) m (

n 1.6 u o r G

e 1.4 h t

f o

f 1.2 o

t h g i TLR Limit

e 1 H

C 0.8

0.6

0.4 Vehicle Length 0.2

0 0.00 1.00 2.00 2.11 3.00 4.00 5.00 6.00 7.00 8.00 Vehicle Length Needed for Stability for a 20 Degree Slope (m)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 36 Stability – Flat Terrain – Vehicle Width vs. Turning Radius and CG Height

2.5 2.4 2.3 2.2 2.1 2 ) 1.9 m ( 1.8 d

n 1.7 u

o 1.6 r 1.5 G

e 1.4 h t

1.3 f

o 1.2

f 1.1 o

t 1 h 0.9 g i

e 0.8 H

0.7

G 0.6 C 0.5 Turning Radius: 2 m 0.4 Turning Radius: 4 m 0.3 7m 0.2 Vehicle Width = 2.37 Turning Radius: 6 m 0.1 2.77 Turning Radius: 8 m 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ...... 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 1 1 1 1 1 1 Vehicle Width Needed for Stability, Velocity = 4.167 m/s

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 37 Stability – Slope – Vehicle Width vs. Turning Radius and CG Height

2.5 2.4 2.3 2.2 2.1 2 ) 1.9 m ( 1.8 d

n 1.7 u 1.6 o r 1.5 G

e 1.4 h

t 1.3

o 1.2

f 1.1 o

t 1 h 0.9 g i

e 0.8 H

0.7 G 0.6 C 0.5 Turning Radius: 2 m 0.4 Turning Radius: 4 m 0.3 0.2 Turning Radius: 6 m 0.1 Turning Radius: 8 m 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 6 4 2 4 6 0 2 4 8 0 2 6 8 0 2 ...... 0 0 0 0 0 1 1 1 1 1 2 2 2 2 2 3 3 Vehicle Width Needed for Stability, Velocity = 1.388 m/s

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 38 Stability

• Braking – Main brakes: Disk brakes 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 slope: 1.94 m/s2 20۫ – • Stopping distance (flat terrain and 20◦ slope) – Flat Terrain: 3.3 m http://stores.brakeplanet.com/Items/nl032828?sck=26119013 slope: 0.50 m 20۫ – • Stopping time (flat terrain and 20◦ slope) – Flat Terrain: 1.57 s slope: 0.72 s 20۫ –

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 39 Stability – Going Over Obstacles

Rover Overturn Due to Collision With Immovable Obstacle

15 14 13 ] r h

/ 12

m Level Terrain

[ k 11 5 deg slope d

e 10 10 deg slope e 15 deg slope S p

9 r 20 deg slope e

v 8 Level Terrain o

R 5 deg slope 7 10 deg slope 6 15 deg slope 20 deg slope 5 0.05 0.1 0.15 0.2 0.25 0.3 Obstacle Height [m] * Solid lines assume 5% energy lost at impact * Solid line denotes 5% *energy Dashed l indissipatedes assume 25 at% eimpact;nergy lost dashedat impact line denotes 25% Low CG and wide base contribute to stability in handling obstacles.

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 40 Steering

Flat Terrain 20o Slope 1200.00 400.00

1100.00 350.00

300.00 1000.00 250.00 900.00 200.00 800.00 150.00 700.00 t y i l t y 100.00 i i l b i a 600.00 b r

a 50.00 e r e

S t e 500.00 0.00 Wheel 1 Diameter 0.03 m S t e 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 400.00 Wheel 1 Diameter 0.04 m -50.00 Wheel 1 Diameter 0.05 m Wheel 1 Diameter 0.03 m 300.00 Wheel 1 Diameter 0.06 m -100.00 Wheel 1 Diameter 0.04 m Wheel 1 Diameter 0.07 m Wheel 1 Diameter 0.05 m -150.00 200.00 Wheel 1 Diameter 0.08 m Wheel 1 Diameter 0.06 m Wheel 1 Diameter 0.07 m Wheel 1 Diameter 0.09 m -200.00 100.00 Wheel 1 Diameter 1.0 m Wheel 1 Diameter 0.08 m -250.00 Wheel 1 Diameter 0.09 m 0.00 Wheel 1 Diameter 1.0 m 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 -300.00 Wheel Width - b - (m) Wheel Width - b - (m)

Skid Steering • The larger the track width the better the performance • Extra mass and complexity for actuators to steer is avoided V1 V2 V • Zero turning radius at rest Steerability Criteria:

Fo ≤ c b l +(w tan(Φ))/2

Steerability = (c b l +(w tan(Φ))/2) - Fo

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 41 Suspension – Human Factors

Frequency (Hz) Effect 0.05 – 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 trunk 20 – 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 42 Suspension – Trade

Type Description Examples Advantages Disadvantages Dependent • Movement of wheel on one • Hotchkiss (leaf • Simple to design • Negatively affects ride side of the vehicle affects the springs) • Low cost and handling compared to movement of wheel on the • Trailing arms • Low mass independent systems other side of the axle. • Leaf spring •Commonly used on • 4-bar commercial and off road vehicles.

Semi- • Beam that can bend and • Trailing twist axle • Simple to design • Design flexibility dependent flex Independent • Widely used today in the • Macpherson Strut • Better drive and handling commercial vehicle industry • Double Wishbone over independent passive • A-arm suspensions. • Multi-link • Design flexibility • Better reliability than active/ semi-active. • Better cost and mass over active/semi-active Semi-Active • Suspension dynamics • Hydropneumatic • Continuous improvements to • Cost and design maturity change continuously but is • Hydrolastic road handling and ride not electronically monitored • Hydragas Active • Electronic monitoring of • Bose Suspension • Continuous monitoring of • Increase in cost and vehicle conditions, coupled • Active body control vehicle motion for improved mass, negative affects to with the means to impact bounce, roll, pitch and wrap reliability, and design vehicle suspension. modes. maturity

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 43 Suspension Analysis

Natural Frequency of the Wheel versus Spring Diameter Natural Frequency of the Suspension versus Spring Diameter

2.9 1.150 2.85 1.100 2.8 1.050 Coil Diameter = 0.06m 2.75 Coil Diameter = 0.06m 1.000 Coil Diameter = 0.08m 2.7 Coil Diameter = 0.08m 0.950 Coil Diameter = 0.10m 2.65 Coil Diameter = 0.10m 0.900 Coil Diameter = 0.12m 2.6 Coil Diameter = 0.12m 0.850 Coil Diameter = 0.14m z ) z ) 0.800

H 2.55 Coil Diameter = 0.14m H ( (

2.5 0.750 y y c 2.45 c 0.700 n n

e 0.650 2.4 e u u 0.600

MODEL q 2.35 q e e 0.550 r 2.3 r F F

0.500 l 2.25 l a a 0.450 r 2.2 r u u

t 0.400 t

a 2.15 Mass of a 0.350 N 2.1 N 0.300 Body 2.05 0.250 2 0.200 1.95 0.150 1.9 0.100 1.85 0.050 1.8 0.000 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.011 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) Spring Diameter (m) Mass of Wheel Critical Distance of the Suspension versus Spring Diameter Critical Distance of the Wheel versus Spring Diameter

1050 2.15 1000 2.1 Coil Diameter = 0.06m 950 2.05 Coil Diameter = 0.08m 900 2 Coil Diameter = 0.10m 1.95 850 Coil Diameter = 0.12m 1.9 800 Coil Diameter = 0.14m 1.85 750 ) ) 1.8 m

m 700 (

( 1.75

e e 650 1.7 c c n

n 600 1.65 a a t t 550 1.6 s s i i 500 1.55 D D

l l 1.5

450 a a c

c 1.45 i i 400 t t i i 1.4 r r 350 C C 1.35 300 1.3 Coil Diameter = 0.06m 250 1.25 Coil Diameter = 0.08m 200 1.2 Coil Diameter = 0.10m 150 1.15 Coil Diameter = 0.12m 100 1.1 Coil Diameter = 0.14m 50 1.05 0 1 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.011 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) Spring Diameter (m)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 44 Suspension – Macpherson Strut

• Material: 2014-T6 • Number of Coils: 7 • Density = 2800 kg/m3 • Coil diameter = 0.003 m • Modulus of Elasticity = 72.4 GPa • Spring diameter = 0.1 m • Poisson's Ratio = 0.33 • Length = 0.24 m • Bulk Modulus = 27.2 GPa • Ks = 40 N/m

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 45 Chassis Analysis

Material: 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 Lateral Launch Load: 2 g Area Moment of Inertia: 8.33E-7 Area Moment of Inertia: 8.33E-7 Maximum Deflection (m): 0.005 Maximum Deflection (m): 0.055 Stress in Beam (N/m2): 2.05E+7 Stress in Beam (N/m2): 2.46E+8 Max Sheer Stress (N/m2): 1.42E+3 Max Sheer Stress (N/m2): 1.70E+4 Safety Factor: 13.42 Safety Factor: 1.12 Margin: 1242.01% Margin: 11.61%

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 46 Chassis Dimensions

Mass: 90 kg

0.02 m

1.93 m 0.08 m 0.08 m

0.08 m

1.9 m

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 47 Track-Wheel Hybrid Mobility Unit – Wheel Connector Beam

Rotate 360o • Wheel 1 Diameter: 0.6 m • Wheel 2 Diameter: 0.4 m • Material: Titanium (6% Al, 4% V) • Yield Strength: 1.05x1011 0o point • Beam Thickness: 0.004 m • Beam Width: 0.06 m • Load Applied: ~ 734 N

0.4 m 0.6 m 0.2 m

Maximum Maximum Desirable Angle Optimum Angle Length of Deflection - Y Mass of Stress in Safety to the 50 cm to the 10 cm beam (m) (m) Beam (kg) Beam (N/m2) Factor (SF) Obstacle Obstacle 0.70 0.026 ~ 0.5 4.11E+08 ~ 2 34.85o 0.00o

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 48 Motors and Gearing – Design Space

Multi-Staged/ Combinations

Harmonic Drives

Planetary Gear Systems

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 49 Motors and Gearing – Motors Trade Space

Typical Type Advantages Disadvantages Typical Drive Application • Long lifespan • Hard drives Brushless DC • High initial cost • Low maintenance • CD/DVD players • Multiphase DC Electric Motor • Requires a controller • High efficiency • Electric vehicles • Low initial cost •High maintenance • Treadmill Brushed DC • Simple speed control (brushes) • Exercisers • Direct (PWM) Electric Motor (Dynamo) • Low lifespan • Automotive starters • Least expensive • Rotation slips from AC Induction • Uni/Poly-phase • Long life frequency • Fans (Shaded Pole) AC • High power • Low starting torque AC Induction • High power • Rotation slips from • Uni/Poly-phase (Split-Phase • Appliances • High starting torque frequency AC Capacitor) • Rotation in-sync with • Clocks AC • Uni/Poly-phase freq • More expensive • Audio turntables Synchronous AC • Long-life (alternator) • Tape drives • Positioning in • Precision positioning • Slow speed Stepper DC printers and floppy • Multiphase DC • High holding torque • Requires a controller drives

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 50 Motors and Gearing – Legacy and Future Rovers

Mars Exploration Rover Apollo Lunar Roving Mars Science Laboratory (180 kg) Vehicle (210 kg) (900 kg)

• Independently driven wheels; 28 • Independently driven wheels; 36 • Selected brushless DC motor; low VDC brushed motors VDC brushed motors temperature/low-mass gearbox. Motors • Identical motors used for steering • front and rear wheels. • A failure in testing of the proposed dry lubrication to support motor actuator • Two-stage planetary gearbox • Harmonic drive (80:1) operations at very cold temperatures is Gearing powers a harmonic drive. (1500:1) contributing to MSL project delays.

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 51 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*

* Note: a low-temperature failure in testing of the brushless DC motors is contributing to MSL project delays BluWav In-Hub Motor http://www.bluwavsystems.com/whitepapers/46kWHubMotor.pdf

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 52 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 small wheel about large wheel to change angle of W approach W 4 W Rotate about small 4 W 4 4 wheel to lift vehicle

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 53 Design Details – Dimensions

0.30 m 2.1 m

0.40 m 0.60 m 0.3 m 1.87 m 1.9 m 1.93 m 2.6 m 3.1 m y z x

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 54 Design Details – Dimensions

2.7 m

0.9 m

2.47 m

3.67 m 0.07 m

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 55 Design Details – Mobility Configurations

Nominal 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 56 Design Details – Mobility Configuration

Other Possible Configurations

• 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. θ

• 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

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 57 Operations – Logic Diagram

Initialize Use Sensors and Detect Obstacles Calculate Path Operations Imaging to Detect Slopes Generate Map Nominal Driving Condition Every 15 seconds Compare to previous Categorize obstacle height Tracks are flat to ground Categorize slope angle

1 2 3 4 5 6 7

No Obstacle in Path Increase Speed Operate on 1 No Slopes in Path to 15 km/hr Flat Terrain

Re-plan path to Obstacle in Path Obstacle > 50cm 2 Avoid Obstacle

Lower Speed Change Angle Obstacle in Path Obstacle ≤ 10cm 3 to 7.5 km/hr of Approach

Lower Speed to Change Angle Obstacle in Path 10 cm ≤ Obstacle < 30cm 4 5 km/hr of Approach

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 58 Operations – Logic Diagram

Operating on Use Sensors and Detect Obstacles Calculate Path Flat Terrain Imaging to Detect Slopes Generate Map Nominal Driving Condition Every 15 seconds Compare to previous Categorize obstacle height Tracks are flat to ground Categorize slope angle 15 km/hr velocity

1 2 3 4 5 6 7

5 Obstacle in Path 30 cm ≤ Obstacle ≤ 50cm Come to a Stop A B C

Change Angle Climb and Drive Over A of Approach the Obstacle

Change Angle Place Small Wheels Lift Vehicle, Level off, B of Approach Onto the Obstacle and Drive Forward

Roll Large Wheels Drive Over the Obstacle Lift Vehicle onto Approach Onto the Obstacle with Large Wheels C Small Wheels Obstacle Rotate Small in Front Small Wheels Back Wheels in Back

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 59 Operations – Logic Diagram

1 2 3 4 5 6 7

Re-plan path to Slope in Path Slope > 20o 6 Avoid Slope

7 Slope in Path Slope ≤ 20o A B

Lift Vehicle Onto Keep Nominal Lower Speed Approach Slope Small Wheels Partially A Driving Condition to 5 km/hr And Start Climb to Keep Vehicle Level θ

Keep Nominal Approach Slope B Driving Condition and Climb θ

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 60 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 61 Sensors – Odometry System

Dead Reckoning • Deduce position after moving for a known time at a known direction with a known velocity

∆β(p) We want to obtain position P+1 from the position at P ∆d(p) The difference ∆x(p) = x(p+1) – x(p) may be deduced from ∆d(p), ∆β(p)

P+1 P

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

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 62 Sensors – Angular Positioning Sensors

∆β(p)

∆d(p) Forward motion may be measured by a The transversal angle of angular motion sensor by multiplying wheel radius r by may be measured with a sensor angular motion (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 Easily mounted, can withstand Synchros/Resolvers Require AC signal source, heavy extreme environments Optical encoders Higher resolution, digital High cost, not very robust * Incremental optical encoders will be used for TLR’s angular positioning sensors

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 63 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.

Yaw

IMU provides attitude and acceleration information during surface operations and convert to outputs used by vehicle control systems for guidance

Roll Pitch

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 64 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.

P(not B|A)P(A) P(A| not B) = P(not B|A)P(A)+P(not B| not A)P(not A)

• Since Lidar scan will occur every 15 seconds it is safe and effective to update map using this technique.

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 65 Command and Control

3 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.

* A maximum of 5 watts of power are required for each 133 mHz BAE Systems RAD750 http://www.corelis.com/images/BAE-RAD750-board.jpg 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 Maxwell Technologies SCS750 http://www.maxwell.com/images/me/_sbc/scs750d_press.jpg6

* Maximum of 35 watts processing for entire rover computer system

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 66 Command and Control

Optical IMU LIDAR Encoders

Attitude and Acceleration Obstacle Ranging Angular Position

COMPUTING

Path Commands SCS750 RAD750 Range Maps

Motor Commands Motor based off possible paths 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.

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 67 Mass Budget

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 Total Mass: ~723 kg (11% margin)

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 68 Reliability Reliability for Loss of Mission: 0.9930 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 Reliability for Loss of Crew: 0.9977

Reliability 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 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 69 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 70 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 71 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.

Critical systems separated from the capsule and packaged View From Top on the wheels. (power, mobility controls, sensors…) Simple platform to support manned transport Tracks as designed in this system

Suspension as designed in this system

12/11/2008 ENAE-788X • Cagatay Aymergen • Jignasha Patel • Syed Hasan • John Tritschler 72 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.

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