Robotis RX-28 User Manual

Dynamixel

Closer to Real,

User’s Manual 2007-03-27

X-28

DYNAMIXEL

Contents

RX-28

1. Summary

1-1. Overview and Characteristics of RX-28 Page 2 1-2. Main Specifications Page 3

2. Dynamixel Operation

2-1. Mechanical Assembly Page 4 2-2. Connector Assembly Page 5 2-3. Dynamixel Wiring Page 6

3. Communication Protocol

3-1. Communication Overview Page 9 3-2. Instruction Packet Page 10 3-3. Status Packet Page 10 3-4. Control Table Page 12

4. Instruction Set and Examples

4-1. WRITE_DATA Page 19 4-2. READ_DATA Page 20 4-3. REG WRITE and ACTION Page 21 4-4. PING Page 22 4-5. RESET Page 22 4-6. SYNCWRITE Page 23

5. Example Page 25

Appendix Page 31

DYNAMIXEL

RX-28

1. Dynamixel RX-28

1-1. Overview and Characteristics of RX-28

Dynamixel RX-28 The Dynamixel series robot actuator is a smart, modular actuator that incorporates a

gear reducer, a precision DC motor and a control circuitry with networking functionality, all in a single package. Despite its compact size, it can produce high torque and is made with high quality materials to provide the necessary strength and structural resilience to withstand large external forces. It also has the ability to detect and act upon internal conditions such as changes in internal temperature or supply voltage. The Dynamixel RX-28 has many advantages over similar products.

Precision Control Position and speed can be controlled with a resolution of 1024 steps.

Compliance Driving The degree of compliance can be adjusted and specified in controlling position.

Feedback Feedback for angular position, angular velocity, and load torque are available.

Alarm System The Dynamixel series robot actuator can alert the user when parameters deviate from

user defined ranges (e.g. internal temperature, torque, voltage, etc) and can also handle the problem automatically (e.g. torque off)

Communication Wiring is easy with daisy chain connecti on, and it support communication speeds u p to

1M BPS.

Distributed Control Position, velocity, compliance, and torque can be set with a single command packet,

thus enabling the main processor to control many Dynamixel units even with very few resources.

Engineering Plastic The main body of the unit is made with high quality engineering plastic which enables it

to handle high torque loads.

Axis Bearing A bearing is used at the final axis to ensure no efficiency degradation with high external

loads.

Status LED The LED can indicate the error status to the user.

Frames A hinge frame and a side mount frame are supported by option.

DYNAMIXEL

RX-28

1-2. Main Specifications

RX-28 Weight (g) 72 Gear Reduction Ratio 1/193 Input Voltage (V) at 12V at 16V Final Max Holding Torque(kgf.cm) 28.3 37.7 Sec/60degree 0.167 0.126

Resolution 0.3° Operating Angle 300°, Endless Turn Voltage 12V~16V (Recommended voltage: 14.4V) Max. Current 1200mA Operate Temp erature -5 ~ +85℃℃ Command Signal Digital Packet Protocol Type RS485 Asynchronous Serial Communication (8bit,1stop,No Parity) Link (Physical) RS48 5 Multi Drop Bus ID 254 ID (0~253) Communication Speed 7343bps ~ 1 Mbps Feedback Position, Temperature, Load, Input Voltage, etc. Material Full Metal Gear, Engineering Plastic Motor Maxon RE-MAX

DYNAMIXEL

RX-28

2. Dynamixel Operation

2-1. Mechanical Assembly

Option Frames

OF-28B OF-28S

RXOF-28H Horn-28T

DYNAMIXEL

Assembly Sample assembly using option frames.

RX-28

2-2 . Connector Assembly

Assemble the connectors as shown below. Attach the wires to the terminals using the

correct crimping tool. If you do not have access to a crimping tool, solder the terminals to the wires to ensure that they do not become loose during operation.

DYNAMIXEL

RX-28

2-3. Dynamixel Wiring

Pin Assignment The connector pin assignments are as the following. The two connectors on the

Dynamixel are connected pin to pin, thus the RX-28 can be operated with only one connector attached.

( Note : The pin number of connector’s edge cut side is PIN1)

PIN4: DPIN3: D+ PIN2: VDD(12V~21V)

Wiring Connect the RX-28 actuators pin to pin as shown below. Many RX-28 actuators can be

Main Controller To operate the Dynamixel actuators, the main controller must support RS485 UART. A

PIN1: GND

controlled with a single bus in this manner.

Control Box “CM-2

proprietary controller can be used, but the use of the Dynamixel controller CM-2 PLUS is recommended.

PIN1: GND

PIN2: VDD(12V~21V) PIN3: D+ PIN4: D-

DYNAMIXEL

Connection to UART To control the Dynamixel actuators, the main controller needs to convert its UART

RS485 UART A multi-drop method of connecting multiple Dynamixel actuators to a single node is

RX-28

signals to the RS485 type. The recommended circuit diagram for this is shown below.\

VDD

The power is supplied to the Dynamixel actuator from the main controller through Pi n 1 and Pin 2 of the Molex3P connector. (The circuit shown above is presented only to explain the use of RS485 UART. The CM-2 PLUS controller already has the above circuitry built in, thus the Dynamixel actuators can be directly connected to it)

The direction of data signals on the TTL level TxD and RxD depends on the DIRECTION485 level as the following.

• When the DIRECTION485 level is High: the signal TxD is output as D+, D-

• When the DIRECTION485 level is Low: the signal D+, D- is input as RxD

possible by using the RS485 UART. Thus a protocol that does not allow multiple transmissions at the same time should be maintained when controlling the Dynamixel actuators.

Main

Controller

CCW

[Multi Drop Link]

DYNAMIXEL

Caution Please ensure that the pin assignments are correct when connecting the Dynamixel

Connection Status Verification

Inspection If the above operation was not successful, then check the conne ctor pin assign ment an d

RX-28

actuators. Check the current consumption when powering on. T he current consumption of a single Dynamixel actuator unit in standby mode should be no larger than 50mA

When power is applied to the Dynamixel actuator, the LED blinks twice to confirm its connection.

the voltage/current limit of the power supply.

DYNAMIXEL

RX-28

3. Communication Protocol

3-1. Communication Overview

Packet The main controller communicates with the Dynamixel units by sending and receiving

data packets. There are two types of packets; the “Instruction Packet” (sent from the main controller to the Dynamixel actuators) and the “Status Packet” (sent from the Dynamixel actuators to the main controller.)

Communication For the system connectio n below, if the main controller sends an instruction packet with

the ID set to N, only the Dynamixel unit with this ID value will return its respective status packet and perform the required instruction.

Unique ID If multiple Dynamixel units have the same ID value, multiple packets sent

Protocol The Dynamixel actuators communicate through asynchronous serial communication

Instruction Packet(ID=N)

Main

Controlle

simultaneously collide, resulting in communication problems. Thus, it is imperative that no Dynamixel units share the same ID in a network node.

with 8 bit, 1 stop bit and no parity.

Main

Controlle

Instruction Packet

Status Packet

ID=0 ID=1 ID=N

Status Packet(ID=N)

DYNAMIXEL

RX-28

3-2. Instruction Packet

The Instruction Packet is the packet sent by the main controller to the Dynamixel units to send commands. The structure of the Instruction Packet is as the following.

Instruction Packet

0XFF 0XFF The two 0XFF bytes indicate the start of an incoming packet.

ID The unique ID of a Dynamixel unit. There are 254 available ID values, ranging from

Broadcasting ID ID 0XFE is the Broadcasting ID which indicates all of the connected D ynamixel units.

LENGTH The length of the packet where its value is “Number of parameters (N) + 2”

INSTRUCTION The instruction for the Dynamixel actuator to perform.

PARAMETER0…N Used if there is additional information needed to be sent other than the instruction itself.

CHECK SUM The computation method for the ‘Check Sum’ is as the following.

OXFF 0XFF ID LENGTH INSTRUCTION PARAMETER1 …PARAMETER N CHECK SUM

The meanings of each packet byte definition are as the following.

0X00 to 0XFD.

Packets sent with this ID apply to all Dynamixel units on the network. Thus packets sent with a broadcasting ID will not return any status packets.

Check Sum = ~ (ID + Length + Instruction + Parameter1 + ... Parameter N) If the calculated value is larger than 255, the lower byte is defined as the checksum value. ~ represents the NOT logic operation.

3-3. Status Packet(Return Packet)

The Status Packet is the response packet from the Dynamixel units to the Main

Controller after receiving an instruction packet. The structure of the status packet is as the following.

OXFF 0XFF ID LENGTH ERROR PARAMETER1 PARAMETER2… PARAMETER N CHECK SUM

DYNAMIXEL

0XFF 0XFF The two 0XFF bytes indicate the start of the packet.

ID The unique ID of the Dynamixel unit returning the packet. The initial value is set to 1.

LENGTH The length of the packet where its value is “Number of parameters (N) + 2”

ERROR The byte repres enting errors sent from the Dynamixel unit. The meaning of each bit is

RX-28

The meanings of each packet byte definition are as the following.

as the following.

Bit Name Details

Bit 7 0 -

Set to 1 if an undefined instruction is sent or an action

Bit 6 Instruction Error

instruction is sent without a Reg_Write instruction. Set to 1 if the specified maximum torque can't control the

Bit 5 Overload Error

applied load.

Bit 4 Checksum Error Set to 1 if the checksum of the instruction packet is incorrect.

Bit 3 Range Error Set to 1 if the instruction sent is out of the defined range.

Bit 2

Overheating

Error

Angle Limit

Bit 1

Error

Input Voltage

Bit 0

Error

PARAMETER0…N Used if additional information is needed.

CHECK SUM The computation method for the ‘Check Sum’ is as the following.

Set to 1 if the internal temperature of the Dynamixel unit is above the operating temperature range as defined in the control table. Set as 1 if the Goal Position is set outside of the range between CW Angle Limit and CCW Angle Limit. Set to 1 if the voltage is out of the operating voltage range as defined in the control table.

+ 27 hidden pages

Robotis RX-28 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual