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I made an Arduino quadruped robot by-hand, meaning without a kit or a 3D printer. It walks using a “long step” gait, which can be very smooth and natural looking. It didn’t quite come out the way I wanted though. However, to make my robot unique, I had the idea to create a skimming-type motion along the floor, similar to the way that boatman water beetles swim. In all my searches online, I have not come across a quadruped robot that has been programmed to move in this way, so this may be the first of its kind published online (?). The skimming motion is an awkward, jerky way to move, but is super fun and much faster than walking. Furthermore, it has allowed me to program a gripper mode with the front lets where the robot to be able to pick up small, light-weight objects. In the first video below, the robot walks then skims along the floor. In the second video the robot walks, then about halfway through the video it grips the garbage and disposes of it before skimming way.

This Instructable is not intended as a beginner project, so I assume you have some knowledge about using Arduino and uploading sketches, etc. That being said, I started this project when robotics was a new hobby, so the design and construction has been a trial-and-error process. If you have constructive feedback feel free to leave it in the comments at the end. Also, if you like the robot, please vote for it in the current Arduino contest!

The legs are numbered: 1) front left of the robot, 2) back left, 3) back right, and 4) front right. Each leg has three parts with a servo motor to move each part. The three motors are named: hip, femur and tibia, and are numbered for each leg. For example, in the programming for the motors of leg 1, they are called “hip1”, “fem1”, and “tib1”. At the bottom of each hip motor is a small ½ inch caster to roll in the skimming motion.

The robot uses two 9volt batteries. One powers the Arduino Nano, which in turn powers a servo motor driver, and a receiver for the remote control. The other battery is used for the motors, which was light but provided enough voltage.

I used an infrared (IR) remote to control the robot. These are easy to use with pre-programmed code available on the internet, and has many buttons which made it easy to run all the different functions of the robot.

Getting the Parts

- Servos motors SG90 (x12) – with servo horns (included with the servo motors: 4 cross-shaped, 8 single lever type), and the included screws
- Nano microcontroller (x1)
- Mini 170-hole breadboard (x1)
- Pulse Wave Modulation (PWM) servo driver (x1)
- ½” Casters (x4) (link)
- Polystyrene plastic sheet – 3.2 mm thick (See hobby store link below)
- Polystyrene plastic sheet (just a scrap piece will do) (See hobby store link below)
- Polystyrene “L” shape plastic angle (4.8mm) (See hobby store link below)
- IR receiver module and IR remote control (a part from Elegoo kit)
- 9V NiMh rechargeable batteries (x2) and charger
- Connectors for the 9v batteries (x2) (link)
- M2 screws 10mm (x38) (link)
- M2 nuts (x60) (link)
- M2 screws 6mm (x14) (link)
- M3 screws 14mm (x2) (link)
- M3 nuts (x4) (link)
- 5mm LED (x1)
- 1000 Ohm resistor (x1)
- Jumper wires, male-to-female (x7) (a part from Elegoo kit)
Optional: rubber Lego tires (x4) to add grip for the legs

Other Tools/Supplies:

- Arduino IDE (free software on the internet used to program the Nano)
- Mini USB cable (to program the Nano)
- Testors model glue (See hobby store link below)
- Hobby knife (x-acto knife)
- Set square
- Ruler
- Needle nose pliers
- Electric drill with 2mm drill bit and larger bits
- Twist hand drill - for holding small drill bits for drilling by hand
- Small screw driver for the M2 screws
- Sandpaper
- Soldering iron and solder (only if you have to solder the pins on the PWM/Servo driver, or on the Nano)

The body is made from 3.2 mm plastic polystyrene. I bought it from this store in Toronto, however you cannot search it on their website. A thinner sheet (e.g. 2mm) may be stiff enough without as much weight. In any case, polystyrene is easy to cut, drill and glue together so I recommend it for this project. The model glue melts pieces together which makes a strong bond.”

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