Dynamixel MX-28AR Actuator

The Dynamixel servomotors

• All-around assembling structure: you can make robots of various forms as using different option frames.
• Powerful feedback : It can read current position of Dynamixel or speed as well as various information such as internal temperature, supply voltage, target position.
• Simple connection structure: Wiring is simple because it is linked by Daisy Chain.
• Alarm function: When internal temperature, torque, supply voltage etc. escaped appointed range, it gives feedback about that situation. Also in such emergency situation, it flash LED or be Torque off.
• Compliance configuration: It can configure the compliance to control the position.
• Torque set up : Torque can be set up by 1023 steps from maximum Torque to free run state.
• Low-electric current/high voltagedrive : Its efficiency is high because it runs by high voltage and it improves stability of robot system that is formed by Dynamixel because current consumption is low.
• Status LED : It has LED that can check state of the Dynamixel.
• Drive by network: Dynamixels have unique ID and are controlled by Packet communication on a bus. It supports network of TTL, RS 485, and CAN etc. according to model.

This video illustrates the capabilities and the existing application for Dynamixel servomotors:

Programming the Dynamixel servomotors

The servomotors have to be linked to a main controller (CM-900 and CM-700) to be commanded. The progams are made with RoboPlus, which allow really easy programmation, without much previous knowledge.

The most recent main controllers support embedded C and there is a SDK for you to developp your own applications.

The Dynamixel MX-28AR actuator

The MX series differs from the other due to features such as a more advanced features on the PID control, 360° control et high speed communication. The MX-28 servomoteur has been splited into two models: the Dynamixel MX-28AT actuator that keeps the Half duplex Asynchronous Serial Communication protocol and the TTL Level Multi Drop physical link, when the MX-28AR uses RS485 communication protocol and multi drop bus.

The actuator MX-28AR Dynamixel is an upgrade of the MX-28R model, the two enhancements are:

 An aluminium body, providing an optimal heat distribution, which allows the actuator to stay cooler than the MX-28R.

The MX-28AR actuator also comes with a new fastening system, thread disks therefore eliminating the need for screws.

Technical specifications of the Dynamixel MX-28AR actuator

• MCU : ST CORTEX-M3 ( ST32F103C8 @ 72MHZ,32BIT)
• Position sensor : Contactless absolute encoder (12BIT,360 DEGREE)
• Baud rate: 8000 bps ~ 3 Mbps
• Control algorithm : PID CONTROL
• Resolution : 0.088°
• Running Degree
  • 0° ~ 360°
  • Endless Turn
• Weight : 72g
• Dimension : 35.6mm x 50.6mm x 35.5mm
• Gear Reduction Ratio : 193 : 1
• Stall Torque : 2.3N.m (at 11.1V, 1.3A), 2.5N.m (at 12V, 1.4A), 3.1N.m (at 14.8V, 1.7A)
• No load speed : 54rpm (at 12V)
• Running Temperature : -5A ~ +80A
• Voltage : 9 ~ 16.8V (Recommended Voltage 12V)
• Command Signal : Digital Packet
• Protocol Type : RS485 Asynchronous Serial Communication (8bit,1stop, No Parity)
• Link (Physical) : RS485 Multi Drop Bus
• ID : 254 ID (0~253)
• Feedback : Position, Temperature, Load, Input Voltage, etc.
• Material : Full Metal Gear, Engineering Plastic Body
• Standby current : 100 mA

Technical documentation of the Dynamixel MX-28R actuator

Dimensions of the Dynamixel MX-28R actuator

All the technical specifications of the Dynamixel MX-28AR actuator are available on the website of the manufacturer at http://support.robotis.com/en/product/dynamixel/mx_series/mx-28at_ar.htm.

Comparing the various Dynamixel actuators

This document offers an overview on the characteristics of all the Dynamixel servomotors.

Comparison between all Dynamixel servomotors

The chart below compare the Dynamixel actuators on their performance. Servomotors are differentiated by communication type (and the MX range proposes both protocols).

• Schematics (en)
• Software (en)
• Compatibility guide (en)
• Selection guide (en)
• Dynamixel SDK (en)