hexapod/README.md

Hexapod

A Hexapod Robot using Raspberry Pi Zero W

Introduction

This is a hexapod robot based on Smallp Tsai's hexapod-v2-7697 project. This project reused most of the mechanical design in the original project, but with a full redesign of the circuits and software. The table below shows the difference between this project and the original one.

	Original hexapod-v2-7697	This project
Controller	Linkit 7697	Raspberry Pi Zero W or Raspberry Pi Zero W 2
PWM control	Custom circuit board	2 x PCA9685 motor driver boards
DC-DC	7 x mini360 modules	2 x XL4005 5A Max DC-DC modules and 1 x mini360
Power	2S Lipo battery	2 x 18650 batteries
Remote	BLE	WiFi
Remote software	Android and iOS	PC, Android

https://user-images.githubusercontent.com/471808/148647807-02e3e901-6181-4473-8ac4-3b5998fa8d17.mp4

Mechanism

Bill of Materials (BOM)

Servos

18 TowerPro MG92B are required.

The dimension of 3d printed part is highly dependent on the servo's size. Modification is required if you want to use alternative servos.

3D-Printed Parts

Body x 1

Filename	Thumbnail	Required
body_top		1
body_bottom		1
body_side_wall		2
body_back_wall		1
battery_box		1
battery_holder		2

Leg x 6

Filename	Thumbnail	Required
thigh_top		1 (x6)
thigh_bottom		1 (x6)
joint_cross		1 (x6)
joint_top		2 (x6)
joint_bottom		2 (x6)
leg_top		1 (x6)
let_bottom		1 (x6)
foot_top		1 (x6)
foot_bottom		1 (x6)
foot_ground		1 (x6)
foot_tip		1 (x6)
servo_horn_j1j2		2 (x6)
servo_horn_j3		1 (x6)

Others

Name	Spec	Thumbnail	Required	Note
Screw	M2 6mm		54	Servo Arm: 1 x 18 Joint: 4 x 6 Thigh: 2 x 6
Screw	M2 10mm		24	Thigh: 1 x 6 Pin lock: 1 x 18
Screw	M2 30mm		36	Servo: 2 x 18
Nuts	M2		36	Servo: 2 x 18
Pin (304)	M4 6mm		18	Servo: 1 x 18

Leg Assemble

Assembly video

Exploded view

Detailed steps

• Step 1 - Combine thigh_top, MG92B and thigh_bottom, use M2x30mm screw and nut to secure them together.

• Step 2 - Grab one joint_cross, joint_top and joint_bottom and combine them

• Step 3 - First put 2 x MG92B, leg_top and leg_bottom together with M2x30mm screw and nut. Then attach joint_top and joint_bottom altogether

• Step 4 - Grab foot_top, foot_bottom and foot_ground (and foot_top) and assemble them.

• Finish - Great, you got 1 leg done, 5 more to go :)

Electronics

Bill of Materials (BOM)

Name	Thumbnail	Required
Raspberry Pi Zero W or W 2		1
PCA9685 motor driver		2
XL4005 DC-DC step down		2
Mini 360 DC-DC step down		1
Toggle switch		1

Connection Diagram

Software

Raspberry Pi

Requirements

Raspberry Pi is running Raspberry Pi OS.

• Enable I2C through raspi-config

sudo raspi-config

• Install required packages

sudo apt-get install python3-numpy python3-pip

• Install required Python modules

pip3 install adafruit-circuitpython-servokit

Tips: It is convenient to debug code on Raspberry Pi through VSCode's remote feature.

Running

The hexapod program, located under ./software/raspberry pi/, is written in Python. Use the following command to start it manually.

python3 hexapod.py

PC

PC program source files are located under ./software/pc/. The compiled program can be downloaded under the release page.

• Find the correct IP address of the Raspberry Pi on the hexapod
• Connect to the hexapod using the IP address
• Use the buttons on the panel to control the hexapod

Android