In mobile robots, servomotors are widely used. This kind of actuator is used to move sensors, wheels, and robotic arms. A low-cost solution is to use RC servomotors. It provides a movement range of 180 degrees and a high torque for the existing servomotors.
The servomotor that we will explain in this section is a new type of servomotor designed and used for robotics. This is the Dynamixel servomotor.
Dynamixel is a lineup, high-performance, networked actuator for robots developed by ROBOTIS, a Korean manufacturer. ROBOTIS is also the developer and manufacturer of OLLO, Bioloid, and DARwIn-OP DXL. These robots are used by numerous companies, universities, and hobbyists due to their versatile expansion capability, powerful feedback functions, position, speed, internal temperature, input voltage, and their simple daisy chain topology for simplified wiring connections.
In the following image, you can see Dynamixel AX-12 and the USB interface. Both are used in this example.
First, we are going to install the necessary packages and drivers. Type the following command line in a shell:
$ sudo apt-get install ros-kinetic-dynamixel-motor
$ rosstack profile && rospack profile
Once the necessary packages and drivers are installed, connect the dongle to the computer and check whether it is detected. Normally, it will create a new port with the name ttyUSBX inside your /dev/ folder. If you see this port, everything is OK, and now we can let the nodes play a little with the servomotor.
In a shell, start roscore, and in another shell, type the following command line:
$ roslaunch dynamixel_tutorials controller_manager.launch
If the motors are connected, you will see the motors detected by the driver. In our case, a motor with the ID 6 is detected and configured:
process[dynamixel_manager-1]: started with pid [3966]
[INFO] [WallTime: 1359377042.681841] pan_tilt_port: Pinging motor IDs 1 through 25...
[INFO] [WallTime: 1359377044.846779] pan_tilt_port: Found 1 motors - 1 AX-12 [6], initialization complete.