If you look back through history, far before we had even invented the humble vacuum tube, robots were almost always humanoid. These fictional — or in some cases, non-fictional hoax — automatons were usually some sort of bipedal effigy brought to life by magic or complex mechanical systems. It didn’t take long after we had the technology to build real robots for us to realize that humanoid robots are an overwhelming challenge and aren’t often necessary. It’s more practical to construct robots in other forms that are less anthropocentric. This modular inchworm robot, for example, can bemade for very little money using just a few servo motors.
This inchworm robot was designed by Jegatheesan Soundarapandian, who had been tossing around the idea since he was a teenager. He finally brought the robot to life and has written a tutorial on how you can create your own. It moves around just like a gigantic inchworm, by sliding its front half forward and then contracting to drag its rear half along. It is also capable of turning, though its movement is fairly slow. It does that using just five individual servo motors. Two on each side of the robot are used for vertical movement and the fifth servo motor pivots the body to change direction. The “feet” are equipped with small solenoids to lift the “toes” and reduce friction when a foot needs to slide.
All of those motors are small, affordable MG90S servos. Those are controlled directly by an Arduino Pro Mini, but receive power from a 12V source through a buck converter. The solenoids used to lift the toes are powered from the 12V source through an ULN2803 IC that contains multiple transistors. An HC-05 Bluetooth module is connected to the Arduino and lets the user control the robot through a smartphone app developed specifically for this project. The body of the robot, along with all of the mechanical joints, is 3D-printed. In total, there are 21 individual parts to print, but they’re all fairly small and can be fabricated on any common 3D printer. This robot isn’t capable of doing anything other than move around, but it’s a lot cheaper and easier to build than some sort of humanoid automaton.