Description

This is an API for controlling a SCARA-type (3 degrees of freedom : RTR) robot arm using a raspberry pi and multiple servos.

Dependencies

• Adafruit PCA9685: The shield provides multiple PWM channels and a python library to control them (used for servo control).
• Scipy: This python library is mostly used for line interpolation and must be installed on the RPi in order to draw lines with the robot.

How to use

1. Clone the repository.
2. Install all the dependencies.
3. Modify robot.py accordingly to the robot configuraion:

• Channels used for every servo
• Min/Max pulse for every servo (see Adafruit_PCA9685 reference)
• Line increment

4. Write the main application. AppRobot.py gives a good idea on how to use the robot module. Depending on servos' power, delays must be introduced between move commands to get smooth trajectories.

Quickstart example:

from robot import *

first_joint = 15  # centimeters (all length/coordinates values must be in the same unit)
second_joint = 10  
debug = True  # debug ON

my_robot = Robot(first_joint, second_joint, debug)

# Go to point P using cartesian coordinates (x, y, z)  
my_robot.go_to_coordinates(8.0, 9.0, 4.0)

# Same thing using the Point class
p = Point(8.0, 9.0, 4.0)
my_robot.go_to_point(p)

# Draw line between two points
a = Point (8.0, 9.0, 4.0) 
b = Point (3.0, 9.0, 4.0)
my_robot.draw_line(a, b)

# Follow trajectory/given path
a = Point (8.0, 9.0, 4) 
b = Point (3.0, 9.0, 4.0)
c = Point (0.0, 5.0, 4.0)
d = Point (-2.5, 3.8, 4.0)

points_list = [a, b, c, d]
my_path = Path()

for point in points_list:
  my_path.add_point(point)
my_robot.follow_path(my_path)