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Design of a printable caterpillar robot

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Discover how to design all the parts of a printable caterpillar robot in 3D, assembling and electronics also provided.

For this robot, all parts have been designed from scratch, but in the case of the link of the caterpillar chain, the ideas have been taken form Olalla’s work published on Thingiverse, and thus it has been taken as reference.

In addition to the plastic and a 3D printer, to mount of this robot, you will need:

  • 20 cm of threaded metal rod, ø 5 mm.
  • Screws metric 3, 40mm and 15mm in length.

1. DESIGN OF THE PIECES

The first element to design was the link in the chain, which must assemble with each other, as well as having a hole in the center so that the tooth of a gear enters into it. The link is designed in such a way that you can assemble many of them to form the complete chain of the caterpillar robot.

link

Once designed, the gear’s tooth separation is computed as:

  1. Number of teeth (z)
  2. Module (m)
  3. Pitch diameter (Dp) (1) Dp = z * m
  4. Outside diameter (De) (2) of = Dp + 2 * m
  5. Inside diameter (Di) (3) Di = Dp – 2.5 * m
  6. Circular passage (Pc) (4) Pc = π * m

 

For this work, it has been decided that the gear will have 12 teeth, we also know that the passage of the tooth should be 18 mm, which is the distance that is between the center of the links when they are assembled. So the module is computed as:

PC = 1.8 → 1.8 = π * m → m = 0.57458

Once we get module, we can also get the pitch diameter by means of formula 1

DP = z * m → Dp = 0.57458 * 12 → m = 6.87 cm

Now, we use the formulas 2 and 3 to obtain outer and inner diameters.

Of = Dp + 2 * → m = 2 * 6.87 + 0.57 → = 8 cm

Di = Dp – 2.5 * m → Di = 6.87 – 2.5 * 0.57 → = 5.45 cm

With all these data, now it is possible to design the gear.

gear

The size of the base has been set to 145 mm x 87.5mm, and a width of 5 mm with rounded edges.

Base

Brackets for the actuators have been also designed so that they are attached to the base. We have selected continuous rotation servomotors (size of 42 mm x 20.5 mm), so the bracket is designed as a rectangle of 45 mm x 23.5 mm, with 3 mm holes to screw them to the base.

soporte_servo

As front axle support is designed a cube which has a 5 mm hole for the own axis at the same height, which is the center of rotation actuator (10.25 mm), and it also has side as servo motors stand to be bolted to the base of the robot. It is important to remark that these clamps are different, left and right side, and thus two pieces have been designed.

Eje_izq

Eje_der

Here you can download all the parts designed in stl format.

2 ELECTRONICS

This robot electronics has basically two parts:

-5V voltage regulator

-Arduino Nano v3 and HC-06 bluetooth module

The voltage regulator has one capacitor at the input and another at the output to regulate the battery voltage.

The Arduino Nano v3 is the robot controller and its programming is included below, the module bluetooth HC05 allows to communicate the robot with a mobile device to control it.

The electronics scheme is as follows, and although we only use two servo motors, is prepared to connect up to 4 servomotors and one an ultrasound:

scheme

Here you can download the files for this printed circuit board:

Electronics

3. PROGRAMMING ARDUINO

The following code is an arduino code to remotely control the robot:

In the next image you can see as the robot once assembled:

robot

4 VIDEOS

YouTube Preview Image YouTube Preview Image YouTube Preview Image

5 REMOTE CONTROL APP

Take a look at this post to learn how to design an App on Android to remotely control the caterpillar robot.

 

 

 

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