Robot Modifications
Hi everyone and welcome back to the blog! Last time you read the blog I built the obstacle course and assembled the robot, now it’s time to unite these two and make the robot complete the obstacle course. However before I show you that I will show you some essential modifications I made to the robot so that it performs like Usain Bolt around that obstacle course!
The first modification was already mentioned before in a blog post, namely the stabilizer wheels. These were added instead of the balancing function. The balancing function was not suitable for our purpose as I needed the robot to stay perfectly still during the time of ball collection instead of rocking back and forth trying to keep balance. Furthermore now the robot can make tighter turns around an already narrow obstacle course as it can slowly maneuver without the need for constant forward and backward motion to balance.
The second modification made was the addition of the ball collection basket. The ideal place to mount this basket is the top plate of the robot. It is important to mention that the baskets surface area are cannot exceed 133 cm squared, therefore our launcher have to be fairly accurate! My first prototype of this design made use of a cardboard box measuring 13cm x 10cm. I tested this design on top of the robot with my launcher, however I found that the force of the ping pong balls falling down into the cardboard box was damaging it. Therefore I decided to use a material more durable than cardboard such as plastic. I then upcycled my plastic lunchbox as it had dimensions of 12cm x 11cm and to say I was lucky was an understatement because these dimensions were narrowly just below the area limit at 132 cm squared. This material was suitable for this application however it had a slight issue, namely the ping pong balls would bounce off the bottom of the lunchbox and fall out of the basket. This would not count as a ball has to stay in the basket. To aid the “cushioning” of the ping pong balls when they fall into the lunchbox I layed the bottom of the basket with soft kitchen cloths and the balls finally decided they were going nowhere when they fell in.
Finally the last modification was a stabilizer on the rear of the robot. The problem I came across was that the robot had a tendency to fall backwards with the force of multiple balls striking it at such a high position above its centre of gravity. My first design to combat this problem was the addition of another set of wheels identical to the ones I have on the front. However I deemed this highly impractical as it would decrease maneuverability and increase weight and rolling resistance. The extra dimension of the wheels added on the rear would mean that the robot would be extremely difficult to navigate the tightly spaced obstacle course. Therefore I decided that the solution was a “rear leg” attached to the back of the robot. I decided to upcycle another material in my room in the form of a plastic cocktail stick. This stick is highly flexible and deformable with a spherical ball at one end and a circular disk at the other end as seen from the picture above. This leg would be attached to the bottom plate, 3mm off the ground so that no rolling resistance would be incurred. This leg would also only increase the dimensions by 20mm in a plan view which was an acceptable amount to compromise for the steering. Instead of using tape, glue or screws to mount this leg in place I decided to use physics, or more specifically friction. I knew that the forces pushing against the leg would have to be balanced in all directions therefore I first made a free body diagram.
After the free body diagram was feasible I installed this part on the robot and tested it out. As can be seen from the video I put an immense amount of force on the top position of the robot and the problem of falling over backwards was solved. After further tests it became clear that only one leg on one side of the robot is sufficient.
I hope you enjoyed this weeks blog of the adjustments that had to be made to the robot in order to optimise it for the obstacle course. I would highly recommend checking back onto this channel in a few days where I’ll be posting the robot successfully completing the obstacle course. If you enjoyed the content here please consider following my channel.
