The transmission code we wrote is broken up into two classes: one for driving and one for changing gears. In the drive class, we use a simple tank drive with four motors (two for each side) and two joysticks. To change gears, a pneumatic system opens and closes a solenoid when a button is pressed. "Open" represents one speed while "closed" signifies the other. If you would like to see a copy of the code feel free to leave a comment with an email for us to send it to you or you can email us at firstname.lastname@example.org
We decided to create a two-speed transmission as an off-season project this year. The transmission should allow us to drive at two different speeds (we aimed for around 7 and 15 ft/sec) with full power. With the drivetrains we used in the past, our robot could move at different speeds, but it involved reducing the power. Having a transmission means we can have a setting for high speed and low torque for times when speed is important, and another with low speed and high torque (torque and speed are inversely related) that would be easier to control and would be able to push more strongly. As the CAD drawings show, we calculated the gear ratios in the two situations (you can email or comment again for these specific values, but while writing this post I can't seem to find them). We also have a pneumatic actuator that slides the middle set of gears back and forth between the two sets of gears on the side to create the right gear ratios.
For this process we first started by determining the number of teeth that we would want on each of the gears. Then we modeled the system in SolidWorks. We were then able to use our new laser cutter to make a prototype out of acrylic. While this prototype was not especially sturdy and could not be useful for the final product, it was useful to see what the system would look like. If we continue to pursue a transmission during the season we will continue to refine this design.
Below are the pictures of the acrylic prototype.
The chassis that we modeled in the fall is slightly different from what we have used in previous years. We decided to narrow the chassis so that we could put supports for the bumpers. With this new design we could easily modify the height of the bumpers depending on the rules for the challenge.
The second modification was that we made was to have a piece of sheet metal (or potentially another material) for the base. We could store the electronics board here, and in the current CAD the location of the battery mount is included as well.
In this design the wheels would also be mounted so that they are visible from the outside, and supported on one side. This is a six-wheel drive set-up, and we have not yet figured out the details of the how the chassis would work with the transmission system.
Here is the CAD that we have made.
That is it for now. If you have any other questions or feedback feel free to comment! We are excited for kick-off tomorrow.
PS Make sure to check out the Five Awesome Robots project that we started at youtube.com/fiveawesomerobots