With the Parallax Robot and Microcontroller Expo coming up (4-13 and 4-14) we’ve been working on some product demos. We have three different BASIC Stamp 2 position control demos based on the Synaptron Micro. We’re also assembling a two axis solar tracker. For the tracker we’ve got the mechanics designed and assembled and the motors have been selected and tested (we have a linear actuator with analog feedback and a slew drive with an encoder feedback). Mechanics, movement, and motor control has been tested but we haven’t completed the overarching control scheme yet. We’re leaning toward using an Arduino Uno. In addition to that work I was trying to come up with something I could put together quick that would be a little more “hands-on” fun for people at the expo. I came up with the idea of robotic jousting. It’s kind of like robot combat, but without the saw blades and napalm.
The idea is to have two identical wheeled robots that can joust each other and score points with hits on specific areas. I decided to use momentary switches as the “shield”. When pressed these would score a hit, flash some LEDs, and sound a buzzer. At first I was going to put the “lance” and “shield” on the front of the robots. Then I realized that due to symmetry there would be a lot of mutual hits. instead I’m going to mount the “shield” on the back of the robot, and the “lance” on the front. I may have turned the joust into a game of tag, but hopefully it’ll be a little more fun than running headlong into each other.
With only a few days to assemble these I decided to go with the easiest drive system I could. That’s a skid steer system with the the control signals for each motor coming from a radio control transmitter (standard hobby car controller). The receiver will be mounted in the chassis and wired to the AN/RC input pins of the Motor Mind C dual motor controller. I’m also using the Motor Mind C – BASIC Stamp 2 carrier board which makes the electrical connections easier, but isn’t as awesome as a custom PCB. Skid steering means one RC channel controls one motor’s speed and direction, and the other controls the second motor. A third small wheel is placed to the front of the chassis to keep it from dragging on the ground. Skid steering is a little tricky to get the hang of, but once you do it creates a speedy system that can abruptly spin and change direction.
An image of the first mock-up of the system is included in this post. And the test of the drive system showed it was very maneuverable. I will try using friction wheels as opposed to the foam ones (friction wheels are plastic with an O-ring for a tire). They are only about 0.5” wide and that will cut about 3” off of overall width, making the robots easier to spin and reposition.
I believe I’m at the point today where I can paint the chassis. Throughout this week I should be able to assemble the two robots and give them a test drive. If the first attempt to build these works, I might see about coming up a next generation that have more custom bling. Yep I just said bling.