Hi all, I’m a student in aerospace engineering who just weeks ago heard the word arduino for the first time ever. Obviously, I’m very new to the whole “building robots” thing. I was designated as rover design team leader for our competition team at my university. The objective is to build a rover that will fit inside a rocket and will take telemetry data on ascent to roughly 1000 feet, be deployed from the rocket, parachute down at less than 15 ft/s, eject its parachute, drop a marker, travel 10 feet in a straight line, drop another marker, turn 90 degrees, travel another 10 feet in a straight line, and drop a third marker. It must do all this while fitting inside a rocket, of diameter 7.5", or 11.4" if absolutely necessary. It can be smaller, but that’s just not very feasible with the task at hand. It must also weigh no more than 2kg and do the tasks entirely autonomously. It cannot use pyrotechnics in any way. The field where it must make its maneuvers is farmland, so the wheels/treads must be fairly aggressive and allow a fair amount of space between the body of the rover and the ground. Our team had a design initially with a cylindrical body with wheels on either end using a counter-rotation arm protruding from the side. The problem was that all we had was a 3-3/4"IDx 9" long polycarbonate tube to house all the electronics. These include an arduino mega, 2 gear motors, a slew of servos, an altimeter, an ultrasonic sensor, a LiPo, 3 dice, a 4" metal rod, 3 small, dice-sized tubes, an accelerometer/gyro, and all the wires. What I’m having trouble with is that I’m pretty sure those electronics would not have fit. So I’d like to redesign. It will still include the same electronics, but I’d like to make the body a little bigger. I think this may necessitate a rectangular body with either four wheels or tank style treads. Two would be ideal for clearance, but I don’t think it would work well. My questions for you are these: what electronics do I need other than what I’ve got? How can I ensure it travels 10 feet exactly and makes exactly 90 degree turns? Can I realistically guarantee that the markers deploy; if so, how? How much space do I need to fit all these things? Any ideas on how I could do the wheels so that I have enough clearance? Ideas for body material? Thanks everyone!
Cool project!
You’ll need DC gear motors with encoders mounted to the rear shaft, a compatible motor controller, and for a “perfectly straight line and 90 degree turn”, a good magnetic compass.
Encoders and a compass should work well. GPS is nice, but likely won’t be accurate enough.
When NASA and JPL sometimes have issues, nothing is a “guarantee”. Choosing high quality parts helps, and the more sure you are of the design the better.
The electronics should not take up much room. Your issue will be a reliable propulsion system for the terrain.
Take a look on Google images for rover designs and get some inspiration. If you’re stuck with a cylinder, perhaps a two wheeled design?
Your prototypes can be 3D printed, and then it will be up to you if you want to stick with 3Dprinted plastic or opt for something machined.
Be sure to optimized the frame to minimize weight.
Thanks! Will I need to somehow shield the other electronics from the compass? Also, can you recommend a compass IC? I’ve also been advised that I should have something called an H Bridge inside for the motors; can you tell me a little about that?
“H-bridge” = “Motor Controller” (in this context). The microcontroller cannot provide the current needed to power motors, so you need an intermediate circuit to take commands from the microcontroller and provide the appropriate voltage to the motors. They allow control over speed and direction. robotshop.com/en/motor-controllers.html
Take a look at this tutorial series to get an idea of terminology: robotshop.com/blog/en/robots … ke-a-robot