By, Mitch Anderson
How I Started Building Robots with My Kids
When my son was 12 he told me how much he envies my childhood. I said “What? There was communism, shortages, no human rights…” “Yes, but you’d go to your dad’s shop and make things. In the summer you send me to those camps where boys only care about exchanging ringtones.”
His words really got to me and we started our garage workshop and led me to building a robot with my children.
We made a lots of WW2 1/6-scale vehicles, and even won a couple of modeling prizes. By then, my d
aughter Emma had also jumped in. We soon moved on to a bigger, more challenging project, restoring a sophisticated police robot we purchased from a seller on eBay, a bot that retails for $250K and arrived at our house with all of its accessories weighing close to half a ton.
I studied electrical engineering in my native Romania, and I took computer science in the US, where I arrived at the age of 23. My dad and hero, was a mechanical engineer, overseeing a machine shop of 60 workers, my favorite hangout as a kid. He was also an inventor; in 1965 he redesigned suspension parts for Tatra trucks. When his design was adopted by the factory in Czechoslovakia, that earned him a promotion and a bonus. Later he designed a rock drilling installation that would pump liquid cement inside the cracks in mountains. He worked for a hydroelectric dam company and stabilizing tectonic movements was essential to the safety of the dam.
I started my career at Xerox in the 90’s as a field support engineer. Having a lot of idle time between service calls, I decided to fix and re-sell PCs. When I got laid off in 1997, I turned that side job in a full-time business, “LaptopsForLess.com”. By 2004 we employed 16 people, but I was getting burned out. The business world is exciting, but is also a battlefield. I needed a change and wanted to explore other areas of life.
I sold the business and devoted my time to my family, especially to my twins. For a few years we travelled the world.
I also have a passion for geopolitics and world history so I made three documentaries. (see more at http://www.mitchanderson.com )
The Making of the Andros Robot
I was at the point where making toys was not fulfilling anymore, I wanted to put our skills to work for something useful to the world. I decided to design a police/military robot. I knew that they are very expensive, and I thought I could do a prototype that would be more affordable. I realized the complexity, especially of the arm assembly, so I was a bit hesitant. One evening I was browsing eBay and stumbled across a used, “AS IS” retired police robot. I thought it would be a great way to ease myself in this field by restoring a professional robot first and take those lessons to the next design.
So I made an offer of $10,000 on the Remotec Andros Mark 4. Quite a price, but not so bad considering a new one is over $250k! The list price on eBay was $20k, but they took my offer. Remotec is the name in this field, and they don’t sell to the public.
The Robot Restoration Process
A week later the machine came, weighing in at 900 pounds, including all accessories, such as a tether cable unit. Some rubber tracks were broken, no docs, and it seemed like it had not been fired up in a long time. I called the company; they did not support any docs or parts for this model anymore.
I decided to re-do all the electrical and remote control from scratch. I was facing 10 brushed DC motors and I felt pretty confident that I could handle that.
Parts and Architecture
For RC I decided to go with a traditional 12-channel radio with a built in Video screen, the DEVO F12 . I like things compact, and having the screen right there, on the commands was nice. On the receiver side I used the matching Devo RX1202, it is stable and reliable, and much cheaper than the fancy RC names like Futaba.
For the signal processing, I decided to use the Teensy 3.5 , since I heard that they are incredibly fast compared to my old time favorite the Arduino Mega.
I decided to use 2 processors, one for the traction wheels and the 4 “Legs” (total of 4 motors) and one for the arm. The “Traction Teensy” was the receiver of all 12 PWM channels using IRQ functions. The traditional “PulseIn” is very slow for the processor. This Teensy would also communicate eight of those values to the “Arm Teensy” through an I2C protocol. I don’t think that any Arduino model could deal with all this stuff in a timely manner, but the 2 Teensys did it, I am so impressed.
Next I realized that I didn’t have enough proportional controls on the transmitter radio to deal with wheels and arm commands at the same time. I contemplated adding a second TX, but that was going to be cumbersome. Carrying two radios for one robot?
So I decided make a “Mode” function in the software, connected to one of the RX binary switches. This way the same proportional sticks would deal with either the wheels or the arm based on the Mode selection. I realized that I wouldn’t ever drive and grab things with the claw at the same time.
We took apart all hubs, cleaned them and lubricated them. Andros does not run on wheel bearings, but on brass bearings in order to deal with heavy loads.
From pictures, I noticed the newer generations of this model have optional rubber wheels so the unit, (which weighs 280 pounds!) does not wear the tracks. This robot did not include that, but I wanted that option. Enter Home Depot’s wheelbarrow wheels at $25 apiece.
That was the easy part, attaching them to the hub was a challenge. As a spacer, we used a waterjet cut 2” thick piece of Acetal on each wheel. Then we made a connecting plate (1/4” aluminum) from the Andros’s hub to the wheel, each being screwed by 20, 10-24” stainless screws to the hub. Andros is supposed to be rainproof, so all parts we used are either aluminum, brass or stainless, nothing can rust. It all worked out, the wheels are solid, I can ride on the robot, and I’m 250lbs.
Powering and Controlling the Robot’s Arm
We found out that the arm is more complex than the traction. Since the arm weighs 65 lbs on its own, we decided that would be better to detach it from the robot and installed it on a separate table on wheels.
The first step was identifying the wires coming out at the bottom, about 45 of them. So Emma and I sat down patiently with the ohmmeter, finding pairs, of 2-3 ohms resistance between them (that is a motor). Then we applied 12V from a battery on each pair and observed the motion. Everything got documented, for example, “Base rotation, right-left”, “Shoulder rotation extend-withdraw”, etc. Luckily there was no interruption in the wires, everything powered fine.
Next I designed a circuit, taking each pair to an H Bridge controller, (nothing fancy, $16 on eBay) and I wrote the software on the Teensy that would take the RC signals and convert them to PWM and motor direction commands. Finally, we connected all the above mentioned pairs to the H Bridges and it all worked—after a few hiccups, (inverted wires, loose wires, minor stuff).
So there we were, with the remote on our knees, picking up a 30-pound lead bar from the floor with the arm fully extended. That is impressive, most arms are very limited in the weight they can hold.
While we were playing with it the shoulder motor quit working. It was turning but the arm was not lifting. We took it apart and found that the worm gear axle broke. We found the Engel motors distributor and he told me that would take 8 weeks to get me one. No way I was going to wait, so I went to a machine shop in my neighborhood. We took the motor apart, and they welded an even thicker axle instead, put back the worm gear and it works like a charm, stronger than before. The repair: $180, but worth it.
Finally we put the arm back on the base of the robot, reconnected the wires and it worked.
Cameras and Remote Video Receiving
Andros was designed with two cameras, one on the “hand unit” and a fancier one (zoom, high resolution) on the “periscope” assembly in the back. They were both feeding the signal in a switch that would take the video output and send it UHF to a receiver.
I didn’t like the idea of switching the video, and I decided to have two transmitters instead, one for each camcorder. I used the Boscam 2W RF model, the maximum power they make. Then I could monitor both cameras (on 2 monitors) or switch between them by toggling the power to each transmitter, front or back. The front was easy, a simple super wide FOV cam 600×400.
For the back I used an older Sony (HDR-SR10) camcorder with a HD and some image stabilization (nice to have when the robot is in motion). This camcorder came with an IR remote that would allow, zoom, rec, etc. I wanted to have these functions available from my radio controller.
I did some research on the net and found the infrared commands for the Zoom function for this model. Then I brought a couple of wires from one of the Teensys to an IR led that I parked in the camera box, right in front of the camcorder. I programmed one of the 3-position switches on the Radio TX to tell the Teensy to generate Zoom in and Zoom out IR commands to the LED. It worked.
And then came the unpredictable: the darn camcorder would go in the “demo mode” after 10 minutes of power on. Not acceptable, the Andros might survey suspects for hours at the time. Disabling the “Demo” from the Sony menus did not do it. After power reset, it would go back to “Demo” after 10 minutes. What to do?
I found the IR code for the “take a picture” camcorder function and I programmed the Teensy to tell the camcorder to take a picture every 7 minutes, or 500,000 milliseconds. It worked! it is kind of fun actually, as we play with Andros, a sudden big flash happens at the most unexpected times.
What Does the Andros Robot Do?
-Andros is mainly a bomb squad robot. The robotic hand can handle a package, open a door, go in a building, or drag a disabled person.
– Andros can also handle tools, cut a door down, drill holes, dig in the ground, sweep the earth with a mine detector, and punch holes in various materials.
– Andros also has a laser guided rifle unit. The rifle can be remotely aimed and fired.
– Andros has long-range remote video and audio capabilities. It can go into dangerous environments (hostage situation, toxic, radioactive…) and video broadcast with sound.
Rent a Robot
I would like to have a small “Robot for hire” business. Action TV shows often feature robots. In a Zoo, a similar robot was used to shoot a tranquilizer in a depressed feline that would not come out of the den. In mines, similar robots dismantle non-exploded charges, inspect abandoned shafts for safety and monitor toxic gas levels. In chemical plants they can turn off valves in places where humans would not do well. Many of these businesses would not invest in the acquisition of such a robot and for the personnel training. There we come in with Andros.
I would like to have a small “fleet” of three robots, Andros being the biggest. Next I am working on the smallest one “Polverson 1”. I am building it from scratch and I am designing an object recognition-retrieval capability. So it can roam a lawn for instance and identify and pick up a golf ball.
I am also discussing custom robotics projects with a couple of potential clients, but their products can’t be disclosed right now.
I’ve learned a lot from this restoration. The mechanical structure done by Remotec is very solid and it would have taken
me years to develop on my own. So far, from what I know, I am the only private citizen to have a functional robot of this size and capability.