Robotic Skateboard

From left to right: Josh, Rachel, David, Ryan, and Jonny

Skateboard jumping down a ramp at the San Diego Science Festival

Successful Jump at the San Diego Science Festival over Rachel

Different View of the Jump over Rachel at the Science Festival

            Invented in the 1970's by Alan "Ollie" Gelfand, the ollie has become a fundamental trick in skateboarding which allows the rider to jump over gaps and obstacles. But what are the physics behind the ollie? Learning physics can prove to be difficult for high school students. Therefore, the objective of this project is to combat the declining interest in math and science among children by making the topics more fun and interactive. High school science can seem dull as students sit at their desks when they should be up and about, learning in a more hands-on manner. By designing a skateboard that demonstrates the basic scientific principles of energy and momentum conservation, we aim to help children see science in a more exciting light, ultimately increasing the number who will go on to become scientists and engineers. We have created a robotic skateboard that performs a basic jump, or otherwise named a "bunny hop," which beautifully demonstrates the fundamental principles of the conservation of energy and momentum. 

Let's first see how a human would perform an ollie: 

Next, lets break down the ollie into a few simple steps:

            So, as you can see, the skateboarder kicks the back of the board down toward the ground, the front of the board moves upward with a high angular momentum. Taking advantage of the front of the board whipping around, the skateboarder then slides his foot up the board while maintaining contact with the skateboards rough surface, dragging it even higher into the air. He then leans forward and levels the board in time to land safely on the ground. 

            Simplifying this notion of the ollie, we can cause a skateboard to jump through an inelastic collision of two bodies.

Design and Breakdown of the Simple Hopping Motion Using Working Model 2D Software

            Here, it can be seen that the hopping skateboard starts with a spring loaded mass located in the middle of two linear sliders. Once the springs are released, the mass shoots up toward the top plate causing the skateboard to jump into the air due to a high impact collision. After the system reaches its peak height, it falls back down and lands safely on the ground. Using the equations for the conservation of mass and energy, it can be found that the jump height of the skateboard is:

Where,        h = Jump height

                                           g = gravitational acceleration

                                               m1 = mass of the sliding object

                                            m2 = mass of the skateboard

                                                          k = spring compression rate constant

                                               x = compression of the springs

            From this equation, which is derived fully in the Final Report, the height of the skateboard can be predicted for any combination of parameters. For the robotic skateboard system, an optimal jump height was found to be 27 Inches. Here is a breakdown of the system that was built and a video of the results.

On March 18th, 2013, the skateboard team joined skateboard maker and visionary, Paul Schmitt, at the San Diego Science Festival to get the kids excited about science through the power of skateboarding. Below is a video of the jump executed by the robotic skateboard.

Video of the first take using a quick release latch

Another attempt at jumping a skateboard