ras_servo_control

This package allows you to control the angle of two servos through ROS using an Arduino Micro.

Requirements

Apart from a ROS installation including rospy, this package requires the pyserial module to be installed for Python 2.7. On Ubuntu you can simply install it using

sudo apt install python-serial

Installation

Clone this repository into your catkin workspace:

cd ~/catkin_ws/src
git clone https://github.com/KTH-RAS/ras_servo_control.git

Next, you need to build the message types:

catkin_make

Don't forget to source your workspace (You do not need to do this if it's already in your bashrc):

source ../devel/setup.bash

Setting up the Arduino Micro

The sketch (=Arduino program) in the folder arduino_servo_control is already installed on your Arduino Micro. If you want to know how to install the sketch, check the official resources: https://www.arduino.cc/

The pins for the servos are hardcoded in the sketch. You need to connect the data wire of your servos to pins 9 and 10, i.e. one pin for each servo. The black cable of each servo should be connected to the GND pin of the Arduino, and the red cable to the VCC pin. To connect the servos to the Arduino you need to use the jumper cables that are in your equipment box: Once everything is connected, it should look like this:

Lastly, connect your Arduino to your NUC/computer using a Micro-USB cable. Note: After the Arduino booted, it will send a signal to both attached servos to move to angle 0. If you want to change this behavior, you need to update the sketch. The initial angles are set here.

Running the node and commanding servo angles

Once everything is connected, run

rosrun arduino_servo_control servo_control

You can move the servos by calling the service /arduino_servo_control/set_servo_angles:

rosservice call /arduino_servo_control/set_servo_angles "angle_servo_0: 90  
angle_servo_1: 30"

The first servo, servo_0, is the servo attached to pin 9, and the second servo, servo_1, the one attached to pin 10. The angles are specified in degrees and can range from 0 to 180. The return value of the service is success: True if the message was forwarded to the Arduino, i.e. an Arduino is connected, else it is success: False.