Not Cow Tipping - Car Tipping!

based on 41 ratings
Author: Lexie S.



Objective: This project was conducted to determine how different declines affect the tipping point and time of a vehicle. It was thought that as the angle increased, the tipping point would occur sooner and that it is possible to prevent a vehicle from tipping over through programming.

Materials and Methods:A robot was built using a LEGO MINDSTORMS NXT 2.0 kit and an additional accelerometer, and programmed to turn. It was run down a ramp at different declines while logging accelerometer measurements and being timed. By using the recorded tipping time, the logged measurements were analyzed to find the tipping point and the "tip-safe" range. The robot was programmed to slow down when out of this range and continue down the ramp.

Results: The robot consistently reached faster tipping times on the 12° angle of decline, while the 0° trials had the slowest times. The 3° trials seemed inaccurate since some were faster than the 6° trials. When compared together, all trials' accelerometer measurement graphs had the same trend of elevation leading up to the tip. The prevention program was proved only effective on the 0° decline but it reduced damages to the robot on all declines.

Conclusion: It is concluded that an increased angle of decline makes the tip occur sooner, though it did not seem to have much effect on the accelerometer measurements and tipping point. The prevention program has an inaccurate and ineffective "tip-safe" range and therefore only works on a 0° decline. If this "tip-safe" range was adjusted, however, the program could still be successful.

8th or 9th grade
Difficulty of the Project

$450 (covers LEGO MINDSTORMS NXT 2.0 kit, HiTechnic Acceleration/Tilt sensor, and LEGO MINDSTORMS NXT education resource kit)

Safety Issues

The only safety issue was avoiding splinters while adjusting plywood ramp.

Time Taken to Complete the Project
5-6 weeks


How does changing the degree of decline affect the time that a LEGO MINDSTORMS NXT 2.0 robotic vehicle tips in milliseconds (ms) and the tipping point in 1/200ths of a g-force (1/20ths meters/sec2) and how can this knowledge be applied to preventing vehicles from tipping?

This project investigates how centripetal force can override gravitational force to tip a vehicle over and how it changes on different slopes or grades. It also investigates whether an accelerometer-based electronic stability control system can be successful.

Materials and Equipment

  • LEGO MINDSTORMS NXT 2.0 (LEGO item #8547)
  • LEGO MINDSTORMS Education Resource set (product ID W979648)
  • HiTechnic Acceleration Sensor Block for MINDSTORMS NXT software
  • computer meeting the requirements for LEGO MINDSTORMS NXT-G software
  • HiTechnic Acceleration/Tilt Sensor for MINDSTORMS NXT (HiTechnic item #NAC1040)
  • open space of floor (at least 8 ft x 12 ft)
  • full sheet of plywood (4 ft x 8 ft x ¼ in)
  • goniometer
  • various household objects to prop ramp on
  • foamy padding (to pad robot with to avoid damage to NXT)*
  • a stopwatch or other timing device that goes to centiseconds
*optional but recommended

All materials except for the HiTechnic Acceleration Sensor Block for MINDSTORMS NXT software, the HiTechnic Acceleration/Tilt Sensor for MINDSTORMS NXT, and the LEGO MINDSTORMS NXT Education Resource Set were found at home already. The HiTechnic Acceleration Sensor Block was downloaded from http :// www . hitechnic . com / cgi - bin / commerce . cgi ? preadd = action & key = NAC 1040. The LEGO MINDSTORMS Education Resource Set was purchased from . The HiTechnic Acceleration/Tilt Sensor for MINDSTORMS NXT was purchased from

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