1. Xtreme Robot Olympiad Adventure Racing
Peter Laz
Associate Professor
Department of Engineering
University of Denver
Thank you!

2. Gray, Yellow, Orange, Teacher
Current Standings
Team
Points
Green, Aqua 50
Gold, Blue 47
Gray, Yellow, Orange, Teacher 44
Red, Purple 41

3. Robot Adventure Racing
Develop your own original design
Choose a new body structure
Change the gears and wheels
Additional materials will be available for “purchase”
Each team has a “virtual budget” of $25
All team members will drive
Score is the average time for your team members
Additional time bonus for a hanging robot
Teams will have 1 minute to get their robot to hang from the pull-up bar

4. Outline Design tradeoffs Vehicle configurations Forces and Torques
Gears
Speed and torque
Wheels

5. Vehicle Configurations
Subsystems
Structure
Steering
Drive train
Considerations
Stability
Maneuverability
Power transmission – torque versus speed
Implementation
Responsiveness (steering/oversteering)
Programming
Weight distribution
Cost

6. Vehicle Configurations
Many Questions:
How many wheels? 2, 3, 4
Two wheel or four wheel drive?
Front wheel drive or rear wheel drive?
How many motors?
How will you turn?

7. Vehicle Configurations
All wheel drive and all wheel steering may be too complicated.

8. 2-Wheel Configurations
Front Wheel Drive
Rear Steer
Rear Wheel Drive
Front Steer
Front Wheel Drive
Front Steer
= Driven
= Steering
Two wheel configurations may be unstable

9. 3-Wheel Configurations
Front Wheel Drive
Rear Steer
Rear Wheel Drive
Front Steer
Front Wheel Drive
Front Steer
= Driven
= Steering

10. 4-Wheel Configurations
Front Wheel Drive
Rear Steer
Rear Wheel Drive
Front Steer
Front Wheel Drive
Front Steer
All Wheel Drive
Need for differentials and/or steering linkages
Tank drive has difficulties going straight as motors are not identical.
= Driven
= Steering

11. Engineering Fundamentals

12. Force Units of force Force = mass * acceleration Weight = mass*g
Newtons (N = kg*m/s2) SI system
Pounds (lb = lb*ft/s2) US system
Force = mass * acceleration
Weight = mass*g
Mass (kg), g = 9.81 m/s2 SI system
Mass (slugs), g = 32.2 ft/s2 US system

13. Torque
A torque or moment is equal to a force x distance at which it acts
= perpendicular distance

14. Torque
The direction a torque acts is determined by the right hand rule.
Point your hand in the direction of r
Then bend your fingers in the direction of F
Your thumb points to the direction of the torque
For your unit vectors: but note:

15. Exercise
Find the magnitude and direction of the torque for each of the conditions a. b. c.

16. Sir Isaac Newton (1642-1727) Three Laws of Mechanics
1. A body continues in its state
of rest or motion until a force
is applied
2. The change of motion is proportional to the force applied
3. For every action there is an equal and opposite reaction

17. Static Equilibrium Newton’s First Law
The sum of the forces and moments acting on a body are zero (0)

18. Levers Consist of 3 parts Effort Resistance Fulcrum (pivot point)
Effort Force W

19. Levers First class lever – fulcrum between the weight and the effort
What happens to the effort
if the fulcrum moves to the left?
if the fulcrum moves to the right?
Effort Force W

20. Levers Second class lever Third class lever W Effort Force W

21. Static Equilibrium
Moments caused by effort and resistance are equal

22. Mechanical Advantage
Measure of the ability of a machine to amplify force
Resistance (Force)
M.A. =
Effort (Force)
Effort Arm
M.A. =
Resistance Arm

23. Gears Some examples include Gears are used to
Can opener
Cork screw
Transmission on your car
Bicycle
Gears are used to
Change the direction of motion
Increase or decrease speed
Increase or decrease torque
Gears are commonly used in power transmission applications because of their high efficiency (~98%)

24. Gears Configurations Spur gears Rack and pinion gears Worm gears
Wheels with mating teeth
Rack and pinion gears
Changes rotational motion to linear motion
Worm gears
Bevel gears
Connects shafts lying at angles

25. Gear Ratio
A gear will rotate with an angular velocity (w) with units of radians/second
Gears have teeth that must mesh
Same pitch = same distance between teeth
There is a fixed ratio between the teeth and the gear radius
N = Number of teeth, r = radius

26. Gear Ratio - Velocity
Velocity of pitch point C on both bodies must be equal w1 w2 C
Driver or Pinion
Driven
= angular velocity

27. Gear Ratio - Torque
Force of gear 1 on gear 2 is equal and opposite to force of gear 2 on gear 1 T2 w1 T1 w2 C
Driver or Pinion
Driven
w = angular velocity

28. Gear Problems Master Equation Small gear to large gear
Slower angular velocity, increased torque
Large gear to small gear
Faster angular velocity, reduced torque

29. Exercise w2 w1 w1 What are the gear ratios? Let: rgreen = 6 inches
rblue = 10 inches
rred = 15 inches
wgreen = 10 rad/sec
What is wred?
Is Tred < or > Tgreen? w1 w1

30. Exercise What is the gear ratio for the squarebot?
Does it increase or decrease the speed of the motor?
Does it increase or decrease the torque of the motor

31. Motor Specification Free speed Stall Torque 100 rpm @ 7.5 volts
6.5 in-lbs

32. Gear Design Decisions Which gears will you choose for your design?
What is the best ratio?
Be careful not to overload your motor.

34. Wheel Size? Large wheels Small wheels
Faster top speed, slower acceleration
Small wheels
Slower top speed, faster acceleration
Which wheel will do better for rough terrain?

35. This workforce solution was funded by a grant awarded under the Workforce Innovation in Regional Development (WIRED) as implemented by the U.S. Department of Labor’s Employment and Training Administration working in partnership with the Colorado Department of Labor and Employment, the Metro Denver Economic Development Corporation, and the City and County of Denver's Office of Economic Development.  The solution was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor.  The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership.  This solution is copyrighted by the institution that created it. Internal use by an organization and/or personal use by an individual for non-commercial purposes is permissible.  All other uses require the prior authorization of the copyright owner.