In order to create more room for the electronics and the motors we decided to make the frame a bit wider than in the first version but by using a small aluminum bar as a tail we were able to make the robot lighter and make him look a bit more streamlined. The smaller part a t the back of the robot was designed to be just a bit larger than the arduino we were using to control the robot so that we would not waste any room or gain any unnecessary weight. There a holes in the top and bottom part of the robot so that the gears driving the wheels can pass through. This ensures that all side panels could be made significantly smaller, again preventing the addition of unnecessary weight. There are smaller holes throughout the entire frame so that cables can be run through the robot to access the electronics in the back.
Mechanical Design
Except for making the wheels a bit bigger the design remained the same. They were still designed to be able to open remotely. Sadly due to lack of time and other complications we were not able to finish this part of our robot. Though it doesn’t affect the robot’s performance on the stairs, it would have made him a lot more versatile and maneuverable while driving around on a flat floor. The wheels can still be opened and closed manually though.
The tail
The wheels
Since we realized that the robot would need to have a longer tail we decided to start experimenting with different shapes and sizes. Finally we discovered that the best shape was simply a long straight tail because this way the robot would always keep the right angle to climb the stairs because he was always leaning on at least two steps behind him. As mentioned before we were limited to certain dimensions (450x350x350 mm). In order to obtain this optimal angle we needed a tail that was at least 700mm long if not more. So we had to think of a way to keep our tail long while climbing the stairs but making it short enough to fit the given dimensions when stationary. We then decided to make the tail retractable. This was accomplished by using a second aluminum profile in which we fastened a jag gear. On the back of the tail we added a DC motor with a gear attached to it so that when to motor was turned on it would retract or deploy the tail.
For the second version of our robot we were forced to add a third DC motor on the tail so we could retract it. In order to drive this motor we needed to add another PCB plate.On our final product we mounted one arduino and 3 PCB plates. The arduino serves as the microcontroller to interpret the code written on the computer. One PCB plate is used to connect the Xbee to the arduino so that wireless communication with the computer is possible. The final two PCB plates are to driver the three DC motors on the robot. Two for steering the robot and one for retracting and deploying the tail.
Electronical Design
Controls
The robot had to be controllable wireless. We opted to use Xbee technology for this. We wrote a straight forward program in Arduino. The main reason we were able to keep this code so simple is that we only used 2 DC motors. We used the program X-ctu to send commands wireless to our robot’s xbee shield.
All in all our robot’s main forte is speed and simplicity. We opted from day one to not over complicate things and despite the difficult problems we encountered we always managed to solve them in a simple way. The robot’s speed is due to its light weight. He only weights 1,9 kg.
Conclusion
