We would like to introduce you to our newest robot. Her name is Alumini, which is pronounced Ah-lu-min-ee. She’s a 12-legged running creature. She’s made out of custom, CNC-machined aluminum components designed to be like vertebrae and bones in keeping with the idea that is a creature not just a machine. Our goal was to create a little beastie without any visible wires or electronics (other than her sonar eyes). She does not have a box filled with electronics like our other robots. We wanted her to look like she was all legs. This meant we needed to use very small electronic parts and we had to do some very tricky wiring. The soldering on this project proved to be quite a challenge, but we were happy with the end results. Alumini is ten inches wide and consists of over 500 parts. Like her much larger 16-legged predecessor, Aluminalis, she uses gear motors to drive two crankshafts, one for each side. Alumini uses a tiny Arduino Pro Mini 328 microcontroller. She can operate via remote control (using an on-board xbee radio) or autonomously using her sonar eyes.
We had good success with our 16-legged walking creature Aluminalis, so we decided to use what we learned and build a new walking creature. We plan for this to be a much smaller, faster, and more agile little beastie. We call her Alumini (Ah-lu-min-ee). Instead of 22″ wide, she’ll be just 10″ wide. Instead of using bulky rectangular segments, we’ve designed much finer segments, like bones in a spine, with built-in pockets for ball bearings to hold the all-important crankshafts. We’ve also designed a custom motor-and-gear mount for each end that holds everything together. Alumini will have twelve legs instead of sixteen. And instead of having a large visible thorax (body), all the electronics will be integrated within and beneath the legs of the robot, so she’ll appear to be nothing but legs. Here are some pictures of our work-in-progress. The crankshaft and legs are not shown. We’re just working on the skeleton and overall structure at this point.
PARTIALLY-CONSTRUCTED SKELETON
MOTOR AND GEARS MOUNTED ON CUSTOM END PIECE
SKELETON TOP VIEW
BONE-LIKE SPINE SEGMENTS MACHINED ON CNC
SPINE SEGMENT WITH BALL BEARINGS (TO HOLD CRANKSHAFT) INSTALLED IN SPINE
CLOSE-UP OF MOTOR-AND-GEAR MOUNT
CNC COVERED IN CHIPS AFTER MACHINING THE PARTS FROM A 12″ x 12″ SHEET OF 1/4″ THICK 6061 ALUMINUM
CNC-MACHINED CRANKSHAFT ARMS ALONG WITH BALL BEARINGS AND SHAFTS
We are happy to announce the birth of our latest creation, Aluminalis, a sixteen-legged walking creature. Along with her sixteen legs and feet, Aluminalis has a fast and lively brain (an Arduino Nano), strong muscles (gear motors), elegant bones (custom machined aluminum linkages), two multi-segmented spines (custom designed crankshafts), ears (Xbee Radio), forward and rear sight (ultrasonic sensors), and a voice (tone buzzer). If you communicate with her in the right way, she will respond to your requests, but she prefers operating on her own, and in some moods, she can be very shy.
Aluminalis is pronounced Ah-lumin-alis. Her full scientific species name is actually Animaris Aluminalis. We derived the name from the word aluminum. As far as we know, she is the only species of the Animaris genus that evolved entirely out of machined aluminum components. Be sure to watch the video. Read below for a species description, evolution, and behavior. At the end of this post, we discuss the original inspiration for Aluminalis.
INTERNAL ELECTRONICS
Species Description
Aluminalis is about 6″ tall and 22″ wide. She consists of a central thorax and two multi-legged sides. Each side is driven by a motor, which drives a pinion gear, which drives a main gear, which drives a four-section crankshaft, which drives a complex set of linkages, which drives the legs. The four crankshaft sections on each side are 90-degrees out of phase with each other so that at least one pair is always firmly on the ground. This is accomplished because the crankshaft is square rather than round. As the motor rotates the crankshaft, the legs loop through a tear-dropped-shaped stepping motion similar to a horse’s gait, causing Aluminalis to walk similar to other animals. Aluminalis changes direction by putting more or less power to the motor on each side. To go forward, she puts equal power to each motor. To go left, she gives the right motor more power than the left motor. And so on. Aluminalis can also go backwards and pivot in place.
Species Evolution
We sketched the original concept for Aluminalis on paper and then designed the various components in SolidWorks. Aluminalis consists of 846 individual components. We machined the segment bars, crankshaft components, thorax plates, and most of the other aluminum components on our CNC mill, vertical mill, table saw, band saw, and drill press. We also used an extensive amount of 1/8” aluminum bar, 1/8” set collars, #4-40 set screws, #6-32 set screws, washers, and ball bearings. There are two long 1/8” steel rods on each side that hold the segments together.
The electronics include an Xbee radio, the Explorer Regulated Board, two Maxbotix ultrasonic sensors, the tone buzzer, wires, resistors, LEDs, 20mm 73:1 gear motors, and main power switch.
Aluminalis uses an Arduino Nano as the main microcontroller, a 12V 3-cell Lithium-Polymer Battery, and a Sabertooth 2 x 5 amp motor controller.
Species Behavior
Aluminalis operates on command (i.e. remote control using the Xbee radio) or on her own. She is still learning and developing, but so far, she has two autonomous modes: The first is roaming. She roams around the workshop using her ultrasonic sensors to find the optimum path and avoid obstacles. The second mode is what we call “shy mode” where she scurries away from people. The only difficulty with this mode is that once you let her off the leash she’s very difficult to catch! 🙂
The Inspiration and Naming of Aluminalis
Aluminalis was inspired by the renown Dutch artist Theo Jansen and his wonderful Strandbeest creatures, which are large kinetic sculptures that he builds out of PVC plastic pipes on beaches in the Netherlands. His awesome sculptures are actually wind driven, rather than motor driven, which makes them even more impressive. Theo always refers to his creations as living animals, for in his heart and mind they are new forms of life. In honor of Theo’s amazing work, we have adopted Theo’s view on this issue, and we’ve also adopted his naming convention, which is to give each species of artificial animal a scientific name with the genus Animaris. So, the full name of our creature is Animaris Aluminalis. As far as we know, Animaris Aluminalis is the only aluminum strandbeest alive today, although we expect them to multiply over time like all living creatures.
Species Range & Habitat
Anamaris Aluminalis is exceedingly rare and highly elusive. This species is believed to favor mountainous regions in Western North Carolina. In particular, it likes living underneath workshop cabinets and usually comes out at night. It feeds on nuts, screws, and small robots.
Construction
Here are some photos of Aluminalis’s construction, followed by a link to our original work-in-progress posts with more details. The custom-designed machined-aluminum crankshaft.
One of the funnest, but most challenging parts of building Aluminalis (our 16-legged walking robot) has been the construction of the two crankshafts. Each side of the robot has a motor that rotates a 10” long, multi-link crankshaft, which drives 4 pairs of legs. The leg pairs need to be kept 90-degrees out of phase from each other in order to produce the walking gait. Our initial vision for the crankshaft was to build it out of 1/8” aluminum round shafts, custom crankshaft arms we made on our CNC, and tiny 4-40 set screws, but when we put it all together for real-life testing, the rotational forces were so high that the set screws couldn’t hold the round shafts, the crankshaft arms slipped out of place, and the entire crankshaft tore apart (not a good day). We went back to the drawing board. We needed a new design. We had the idea of using a square shaft to prevent slippage and guarantee that each of the pairs was 90-degrees out of phase with the others. At first I thought maybe it was a silly, impossible idea. The crankshaft ran through a series of round holes in the body of the robot, so how could a square shaft rotate smoothly in a round hole? Then I realized we could use ball bearings to do that. Our hope was that the square shaft would not only guarantee the 90-degree angle, but it would also give our set screws a flat area to take hold. So, in version two, we used a combination of square shafts, round shafts, larger 6-32 set screws, and bulkier crankshaft arms (that gave the set screws more thread length to take hold). The results were fantastic. The new crankshaft works great in all our real-life tests. Runs strong and smooth. Note that the square shafts are made out of high-strength copper rather than aluminum.
We have been working on Aluminalis, our mechanical sixteen-legged walking robot. We’ve completed the initial build of the left side, which includes eight of the legs. Aluminalis is made with a complex assembly of custom linkages, segments, and shafts that we have been making in our machine shop. A single motor drives all eight of the legs (on this side) via a crankshaft that drives each pair of legs 90-degree out of phase with the other three pairs. That way, one pair of legs will always be on the ground no matter how fast the robot is moving. In the video below, we are testing the kinetic motion and gait of the left side.
