Albuquerque New Mexico is the real-life set of Breaking Bad. So, naturally our robot wanted to dress as the RV from Breaking Bad for Competition. 

30+ Days of collecting from our families and communities produced 3311 lbs and 16 pcs of furniture donated to Savers!

​When we began designing Hal 4.5, we had a few requirements that we needed to meet, namely the size and weight parameters set by Pi Wars. We also wanted to use as many parts from Hal 4K as possible, since he didn’t get to compete in Pi Wars 2020. We also wanted Hal 4.5 to be strong, light and use a majority of 3D printed parts.
 
In order to make sure we met those requirements; Hal was designed using AutoDesk Fusion and the 3D printed parts were made with a Raise 3D E2 printer using ASA filament. 

We explored a few concepts before we decided on the final design.
Concept 1: Direct drive with a 3D printed base plate. Simple, but not easy to modify and only as strong as the 3D printed plastic. 

Concept 2: A variation of concept 1 with gearing, which could allow us to change gear ratios depending on the challenges we were running. A more complicated design with less room on the base plate. The motors have plenty of torque for a direct drive application, so there was no need to deal with the added complexity of gearing.

Concept 3: Another direct drive setup, this time using 15mm x 15mm extruded aluminum which makes Hal super strong and rigid. It also makes it very easy to bolt attachments on with a t-nut and an M5 bolt. As you can see below, this was the winning concept.
 
This design also allowed us to give Hal some articulation. Both the front and rear axles and can pivot, which enables him to deal with obstacles with ease. 

WINNER WINNER

Each axle is attached to the center electronics bay with an M6 x 50mm bolt that is screwed directly into a piece of extruded aluminum. The articulation of the axle is provided by a 608 bearing on each axle.

​Hal’s brain is a Raspberry Pi 4 with a Red Board motor controller hat. The Red Board can only control 2 motors at a time, so Hal’s left motors are connected to one motor output and the right motors are connected to the other. The Red Board also has headers on it with GPIO passthroughs that allow us to control up to 16 servo motors or power accessories.

​We also put a lot of thought into ease of maintenance and repairs. The motor mounts are attached to the extruded aluminum via a pair of M5 bolts. Simply remove the bolts and the motor and wheel assembly slides off. Should we need to replace a motor, we just need to pull off that assembly and unplug that motor from the wiring harness. Then we attach the new motor to the wheel assembly and plug it into the wiring harness.

For the Escape Route challenge, we are using an ultrasonic sensor mounted to Hal’s front bumper. The sensor is an HC-SR04 that is triggered by the Pi. When the sensor hears the return echo, it sends a 5VDC signal back to the Pi which would blow up the GPIO pin since it’s expecting a 3V3 signal.
 
To fix this, we built a voltage divider to knock that 5V pulse down to 3V3. When we were planning out how to handle this challenge, we considered use 3 ultrasonic sensors, so the voltage divider circuit is configured for 3 sensors. After testing though, we decided to K.I.S.S. it (Keep It Simple, Stupid) and only use 1 sensor. (See Below)

Lava Palava and Minesweeper require a slightly different approach. A downwards looking Pixie Cam allows us to follow a line as well as find mines. 

The Eco-Disaster requires yet another strategy, this time we decided to assume direct control of Hal and drive this manually. We did outfit Hal with some mean looking forks that he can use to split up a group of barrels as well as herd them towards the correct endzone. 

Pi-Noon: The Pi-Noon connector is attached to Hal’s front bumper the same way as the ultrasonic sensor. Other robots better look out!

In the Temple of Doom Hal will be in his purest form, just the core robot with his trick articulating axles. He does have one trick up his sleeve for this challenge. The springs we’re using ride on Teflon tubes which allow Hal to flex his way over obstacles with ease. 

The Zombie Apocalypse challenge was by far that most challenging challenge to design. But if there’s one thing us Americans love more than apple pie and baseball, it’s our "Right to Bear Arms". We equipped Hal with a Nerf dart launcher, a top loading magazine and a laser targeting system in order to make sure he could protect us from the zombie hordes. We also made sure he could hit targets at different elevations by allowing him to pivot the blaster up or down.

The core robot has been surprisingly robust, though as with any engineering project iteration is the name of the game. The initial design for 3D printed straps over the battery pack where not that great and they required a redesign.
 
The 608 bearing housings are a core structural element of the design as they hold the center electronics bay together and allow the axles to pivot. And they had a habit of cracking under normal use. To solve this, we redesigned the housing to make it more robust and we took a lot of strain off the bearing by threading an M6 screw straight into one of the extruded aluminum bars.
 
The attachments for each challenge evolved quite a bit during testing, either to make broken parts more robust or to tweak the design to be more efficient. 

​As mentioned above, designing and building a robot is all about iteration: design something, test it, figure out why it doesn’t work (because it almost never works on the first try), fix that problem and try again. Rinse and repeat until you have a design that is good enough to do what you want it to do.
 
The CNM HackerSpace team is looking forward to our trip to Cambridge and competing against all the teams from around the world. See you on April 21st. 

​March has felt good, truly, at least in my eyes. While not perfect, the guts of Hal are completed, his upgrades are falling in line, and testing has finally become the focus.
But with that being said testing can bring anxiety and stress. But following the hedonic treadmill of life, testing also brings joy and excitement. (Did I use hedonic treadmill right, maybe not but you saw what I was going for right?)
Anyway, the flow of March has been such...
Test -> change -> test -> break -> revert -> fail -> change ->SUCCESS!
“Alright, heck yeah guys, let's call it a night. See everyone tomorrow!”
12 hours later...
Test -> smoke ensues (well not literally but... I mean you get it) -> FAIL!
Alright this is the frustrating part, but honestly, it’s also the fun part. How can the same code and the same hardware produce wildly different results. Well, it’s because the results aren’t wildly different, the margins are just beautifully exact. And the main culprit of this need for near perfect precision is the ultrasonic sensor and the Escape Route challenge. Who would have guessed obtaining a near 90-degree turn would have so much variation.
 So, the challenge requires eliminating as many variables as possible. Such as, ensuring start position is the same, that battery power is at 100 percent of 100 percent, and that the floor is level enough to prevent the ultrasonic from picking up changes in elevation. Reaching consistency takes trial and error. And after enough testing, we have achieved 3 flawless escapes, back-to-back-to-back. Now we just need to ensure that will also happen day-to-day-to-day.
In regards to the line following, *cough *cough, Lava Palava, my apologies... It feels like an overachieving child when compared to the Escape Route. Honestly the only thing was making sure we find the ideal angle to point the camera, and we even found a way to make it beautifully faster with an adjusted camera mount. The only snag we hit was when we added a makeshift bump out of cardboard to see how it would perform, and now that I bring it up... I worked hard on that bump!! I had to destroy my cat's favorite box just to gather up enough scraps! I mean I get it wasn’t ideal... and maybe the craftsmanship wasn’t great, but a little appreciation would be nice!!! Anyway, some Walmart card stock and one amazon package acting as a cardboard supply drop and...
Voilà, a beautiful bump that Hal can mosey over all on his own. (See bump down below) 

A HUGE thank you to our incredible sponsors who have made PiWars 2024 possible!

CNM ECOS serves to: Represent student issues to administration, faculty and staff; provide representation on CNM standing committees, Develop and improve internal policies that affect the student body, Network with other college/university student governments and organizations in order to share information and exchange ideas, Promote student community by gathering and disseminating information regarding student leadership opportunities, Executive Council of Students activities and projects, and other student-related issues, Support scholarships and funding through outreach to state and local legislative structures, New Mexico colleges and universities and other groups interested in funding student scholarships (CNM Scholarships and transfer scholarships). www.cnm.edu/depts/student-support/student-activities-office/student-government

Finally hitting an imaginary zombie is cause for a small robot celebration.

44 seconds!! Yet, still not our fastest time!

Have you ever heard 7 people collectively GASP at something they all KNEW was going to happen? If not, then please enjoy! Zombie Apocalypse: Take 1.

Check out the link at the top of our page! "Hackerspace goes to PiWars"! www.cnm.edu/news/cnm-hackerspace-club-wins-prestigious-spot-as-only-american-team-to-compete-in-upcoming-international-robotics-competition