Mir's Blog: Robot Wars at PsiFi 2011

KMB

A picture of my team which went to PsiFi 2011 and our robot 'KMB'

(that's me on the far left)

In 2011 my team and I went to went to the Lahore University of Management Sciences to participate in PsiFi 2011. PsiFi is an annual science based event in students from across meet for 4 days to participate in a series of events which test and broaden their scientific skills. Our team participated in the 'Tour de Mind', an interactive game-show type quiz, 'Gear Up', a mouse-trap and battery powered car competition, and my favourite, possibly my only reason for participating, 'Robot-Wars', which will be the focus of this post.

My team started preparing for Robot wars two months in advance during which we planned the fundamentals of our robot. We first got down to the most important task, deciding what weapons our robot would have. We fantasized about using every weapon from a flame-thrower and hydraulic ram to a nuclear warhead. However, I must mention we also mapped out the basic structure, a minor detail. We finally decided we would have a saw/grinder blade in the front with a large body with which we could ram other bots out of the arena.

We only really started to build our robot only about 30 to 40 days before event, strapped for time we had to use the chassis of two used electric scooters which we found in Sher-shah (a local junk yard) and build on them. We brazed the two chassis together using 4 inch square tube. We then attached the bearings for the axles and blade weapon to the chassis, this was a painstaking process; because we couldn't weld the bearings directly, we had to individually fabricate mounts for the bearings out of washers and pipe. We then proceeded to build mounts for the three motors, one for the blade, one for rear wheels and one for steering. For the drive wheels and the blade we used the motors we salvaged out of the electric scooter chassis. After much adjustment the chains driving the blade and the axle adjusted to have just the right slack.

After that was dealt with we proceeded to making the body of the car. We first drew our designs on paper and then transferred them, panel wise, full size onto chart paper. We used the chart paper as templates for sheet metal and cut it to size using some tin shears and riveted them together.

The electronics were the part that gave me the most challenge. I read up on motor control and decided we needed to use an H-Bridge made from relays. I triggered the relays remotely using a normal RC receiver. (I had to gutted a servo and use the board inside to convert the PPM signals from receiver to PWM which I could use to trigger the relays.) Everything was working perfectly until the circuit powering the steering motor failed. I was out of servos to spare so I couldn’t dismantle another one. We decided to use the servo directly to steer the motor using a switch; we made the servo directly toggle a DPTP switch and make the motor go from CW to CCW to off. It wasn’t pretty but it worked!

When we got to Lahore I had to transfer the circuit from the breadboard to vero-board because breadboard circuit would never survive a battle bot competition. (I still can't remember why I thought that breadboard was sufficient.) I had to stay up till very late to solder the parts on, it got to a point where it was just the fear of burning myself with an the extremely soldering iron that kept me from falling asleep.

So I got the circuit ready, everything worked perfect. I still recall that feeling of exhilaration, that moment when something you’ve made just animates and works. I almost cried when I saw all those hours work being worth it, I couldn't believe we had made a battle bot!

So our team made it to the semifinals, we had to defeat several other bots by pushing them out of the arena. When the semi-final round started our robot didn’t move at all. Needless to say we were promptly set aside by the competitor. I later realized that the relays we were using had burned out, the PWM signals from the servo boards made the relays switch too fast. The batteries were also drained, they had never charged fully.

I learned a lot from this experience. Number one: Never leave a finalized project on breadboard. Number two: Don’t use relays for high speed switching, MOSFETS are the way to go. And most importantly, Number three: make sure you have proof that what you are carrying on the plane is not a bomb.

Before we started the project I had a very basic understanding of electronics and mechanics, all I knew was that we had to build this robot. I researched like crazy, reading things from Wikipedia, Instructables, letsmakerobots.com, societyofrobots.com etc. I built my own understanding of the subject at hand. What I realized after this experience was nothing is really impossible; all it takes is the willingness to do it. I found out I was really more capable than I thought I was. Its we who make ourselves believe we cant do something; The boundary between oneself and ones goal is his own mind.

{if anyone wants some of the circuit schematics, specific details or any additional information my email is: tuniomurtaza@gmail.com}

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