Final Robot

Head Module

                The head module is one of the most if not the most important modules on our robot. It is the single mechanism that our robot uses to collect the balls. The head module was based on the design for the popular children’s game “hungry hippos,” where the plastic hippo’s head moves over the ball in the center and swallows them in order to deposit the balls. We modified this design by using a front plate instead of a hippo head, bottom lip, and two arms to move over the balls before collecting them. The clearance was carefully calculated in Solidworks prior to the module’s manufacturing. The lip was added to help dislodge the balls out of the holes. Since our robot only maneuvers on top of the table, we designed our robot to collect 2 to 3 balls in each swipe. As for the arms, they are connected to four connectors that use bushings to allow smooth rotational movement. They also serve as linkages that connect the head module to the body of the robot. To power the head module, we used a 6 speed gear box that created enough velocity and torque for the head module to collect efficiently.

Robot Movement

                It can be seen from the photos that front drive is free spinning whereas the back drive is powered by a double gearbox with both 114:1 gear ratios. The advantage of a double gearbox is that each of them can be driven independent of the other. The double gearbox is connected to the control box and then controlled by a remote control. With this, our robot is able to turn e.g. to turn right, the left back wheel moves forward, the right back wheel moves backwards and the front wheels slides across the table. The back wheels are covered with rubber bands whereas the front is just left the way it is. The friction from the rubber bands enhances the ability of the robot to turn. To move forward, both of the back wheels move forward. That is basically how we maneuver our robot.

                Given our robot’s good maneuverability, we are able to move swiftly across the table. We can collect a few balls at a time.

Scoring Strategy (changes from beginning to final)

From the beginning we were faced with a choice, we could either try to score by pursuing balls on top of the table, the balls in the slot, or both. We decided that pursuing both the top of the table and slot would be too time-consuming and after some calculations, we came to the realization that the top of the table held more points by far than what was inside the slot. By deciding to go after the points on the tabletop, we knew that our robot would have to move fast to cross the table and score. Our plan was to simply grab a few balls worth a lot of points with a scooping head module and then turn our attention to the other bot.

We wanted to keep everything about this robot as simple as possible to eliminate any complications in the future, so when it came to deciding how we would run our defense we naturally wanted to use as many functions of our robot as both offense and defense. The most obvious result of these decisions was to use our robot to push the other bot around after we snagged our points. This meant that the motors we used to drive would need to have a lot of power to push. We decided to use the planetary motors geared down, even though we would move a little slower.  As an afterthought, we wanted to try to incorporate an oddly shaped object that we could easily drop in either the slot or the other bot’s funnel to gum up their operations. 

When it came down to making these strategies into an actual product, we ran into a few problems. Due to complications in manufacturing we had to sit down two days prior to our deadline and completely rethink our designs based on the materials we had available and the time we had left. We salvaged what we could from our original plan. We still had our head module that could scoop balls to score and we still wanted to try to push the other bot around. We realized that we didn’t have enough room to put two planetary motors in our robot so we had to make do with the double gearbox geared down. It was also out of the question to make an oddly shaped object that we could release because it was far too complicated for the time we had left. With these changes, we had all of Tuesday and Wednesday morning to completely rebuild our robot.

The Competition

                Prior to the competition, we were faced with several major problems. The day before, we discovered that our drive shafts in the head module were slipping once the motor was powered. This essentially made our head module useless and severely hindered our scoring ability. Since we were only allotted about an hour before the competition to make minor changes, we weren’t allowed to fix the problem with the head module. Also, we were facing the second best team (according to scoring) which meant we needed everything to function smoothly in order for us to win. To add to the problems, our turning mechanism was not functioning during the competition. All of these last minute difficulties added up and lead to our loss in the first round of the competition. Even though we lost, we did come close to scoring and almost defeating our opponent. In retrospect, we should have discarded our strategy and should have played more defensively than initially planned.