Over the past few weeks, Tachyon robotics has been working hard to complete our ROV for the upcoming MATE regional competition in April. Meeting 2-4 times a week, we've completed almost every system on the robot and designed ideas for sensors, samplers, and tools to complete the mission tasks provided to us last December. As of today, the main electrical system (excluding sensor bays, which are still in the prototyping phase) is ready to control our ROV, "Tachyon Mk. III." Over the past few weeks, my job has been that of debugging and troubleshooting the three circuit boards that translate the signal put out from our microcontroller into movement for our motors. This process has taken a lot of soldering, desoldering, fabricating and redesigning, but I am incredibly happy with our result.
In a meeting today, I was able to troubleshoot a bug in our circuitry that had caused some minor problems (such as a time limit on our runs due to excess power dissipation by our transistors) that we faced last year using a new tool we were able to purchase with money I had saved up: an oscilloscope. Apart from giving me the opportunity to nerdily plot parametric equations in x-y mode, this new oscilloscope allows us to see the waveforms that potentiate our motors on a scale perfect for troubleshooting and optimizing. Today I was able to use our O-scope to optimize both the frequency of our pulse with modulation and the values of certain pulldown resistors to increase the efficiency and maneuverability of this year's ROV. Below is a picture taken from that process which shows two different waveforms on our oscilloscope's CRT. The upper waveform was taken before I adjusted the values, and the bottom is taken at the end of today's meeting. Note that the lower wave is far more square than the upper. This change will ensure that each movement our pilot makes on the joystick will correspond directly to a change in speed of the ROV. In short, instead of not being able to throttle below 40% before the motors stop turning, as was the case last year, our pilot will be able to have more potentiation between full forward and full stop speeds (from 0% to 1.1% to 100%) on this year's ROV, which will shorten our mission time and lengthen the life of our components.
-Michael Ikegami
A few months ago, we designed some nozzles based on the Rice profile to mazimize the thrust produced by our thrusters. We finally got those nozzles printed (courtesy of Nikolai at the University of Alabama), and, although we haven't done any quantitative tests of them yet, they seem to have given Tachyon III a significant boost in power and performance.
