Axis Communications AX-12 User Manual

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User’s Manual 2006-06-14

Closer to Real,

DynamixelAX-12

DYNAMIXEL AX-12

Contents

1.Summary

1-1.	Overview and Characteristics of AX-12	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 20
4-4. PING		Page 21
4-5. RESET		Page 22
4-6. SYNCWRITE		Page 23
5.	Example	Page 24
Appendix		Page 30

DYNAMIXEL AX-12

1. Dynamixel AX-12

1-1. Overview and Characteristics of AX-12

Dynamixel AX-12	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 series robot actuator 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 connection, and it support communication speeds up 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 included.

DYNAMIXEL		AX-12
1-2. Main Specifications

			AX-12

		Weight (g)		55

		Gear Reduction Ratio		1/254

		Input Voltage (V)	at 7V		at 10V

		Final Max Holding Torque(kgf.cm)	12		16.5

		Sec/60degree	0.269		0.196

Resolution	0.35°
Operating Angle		300°, Endless Turn
Voltage		7V~10V (Recommended voltage: 9.6V)
Max. Current		900mA
Operate Temperature		-5 ~ +85
Command Signal	Digital Packet
Protocol Type		Half duplex Asynchronous Serial Communication (8bit,1stop,No Parity)
Link (Physical)		TTL Level Multi Drop (daisy chain type Connector)
ID	254 ID (0~253)
Communication Speed	7343bps ~ 1 Mbps
Feedback		Position, Temperature, Load, Input Voltage, etc.
Material	Engineering Plastic

DYNAMIXEL AX-12

2. Dynamixel Operation

2-1. Mechanical Assembly

Frames Provided The two frames provided with AX-12 are shown below.

OF-12SH

OF-12S

OF-12SH Installation The OF-12SH (hinge frame) can be installed on the AX-12 as the following.

Exploded view

Assembled

OF-12S Installation The OF-12S (side mount frame) can be installed on the AX-12 as the following. The OF12S can be mounted on any of the three faces (left, right, or under side) of the AX-12 body as needed.

Horn2Body

Exploded view	Assembled

Body2Body

Exploded view

Assembled

DYNAMIXEL AX-12

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 AX-12

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 AX-12 can be operated with only one connector attached.

PIN1: GND

PIN2: VDD

PIN3: Data

PIN1: GND

PIN2: VDD

PIN3: Data

Wiring	Connect the AX-2 actuators pin to pin as shown below. Many AX-12 actuators can be
	controlled with a single bus in this manner.

Control Box “CM-5”

Main Controller To operate the Dynamixel actuators, the main controller must support TTL level half duplex UART. A proprietary controller can be used, but the use of the Dynamixel controller CM-5 is recommended.

PC LINK

A PC can be used to control the Dynamixel via the CM-5 controller.

TTL

RS232 Level

Level

CM-5

Dynamixels

DYNAMIXEL	AX-12
bioloid	A robot can be built using only the CM-5 controller and a number of AX-12 actuators. An
	edutainment robotic kit named “Bioloid” is available which is based on the CM-5
	controller and the AX-12 actuators.

An example of a robot built with Bioloid

For details, please refer to the Bioloid manual.

Connection to UART To control the Dynamixel actuators, the main controller needs to convert its UART signals to the half duplex type. The recommended circuit diagram for this is shown below.

DIRECTION_PORT

74HC126	10K
TXD	10K
TXD
74HC126	DATA	DATA(PIN3)
		DATA(PIN3)
RXD	9.6V	VDD(PIN2)
	9.6V	VDD(PIN2)
	GND	GND(PIN1)
		GND(PIN1)

74HC04

CM-5 internal circuit (HALF DUPLEX UART)

The power is supplied to the Dynamixel actuator from the main controller through Pin 1 and Pin 2 of the Molex3P connector. (The circuit shown above is presented only to explain the use of half duplex UART. The CM-5 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 DIRECTION_PORT level as the following.

DYNAMIXEL AX-12

•When the DIRECTION_PORT level is High: the signal TxD is output as Data

•When the DIRECTION_PORT level is Low: the signal Data is input as RxD

Half Duplex UART A multi-drop method of connecting multiple Dynamixel actuators to a single node is possible by using the half duplex UART. Thus a protocol that does not allow multiple transmissions at the same time should be maintained when controlling the Dynamixel actuators.

	Main
	Controller
	[Multi Drop Link]
Caution	Please ensure that the pin assignments are correct when connecting the Dynamixel
	actuators. Check the current consumption when powering on. The current consumption
	of a single Dynamixel actuator unit in standby mode should be no larger than 50mA

Connection Status Verification

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

Inspection	If the above operation was not successful, then check the connector pin assignment and
	the voltage/current limit of the power supply.

DYNAMIXEL AX-12

	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.)

		Instruction Packet
	Main	Instruction Packet
	Main
	Controller	Status Packet
		Status Packet

Communication For the system connection 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.

Instruction Packet(ID=N)

Main

Controller


ID=0		ID=1	ID=N
	Status Packet(ID=N)

Unique ID	If multiple Dynamixel units have the same ID value, multiple packets sent
	simultaneously collide, resulting in communication problems. Thus, it is imperative that
	no Dynamixel units share the same ID in a network node.
Protocol	The Dynamixel actuators communicate through asynchronous serial communication
	with 8 bit, 1 stop bit and no parity.

DYNAMIXEL AX-12

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

OXFF

0XFF

LENGTH

INSTRUCTION

PARAMETER1

…PARAMETER N

CHECK SUM

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

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

0XFF

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

0X00 to 0XFD.

Broadcasting ID

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

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.

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

LENGTH

The instruction for the Dynamixel actuator to perform.

INSTRUCTION

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

PARAMETER0…N

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

CHECK SUM

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.

OXFF0XFFIDLENGTHERRORPARAMETER1PARAMETER2…PARAMETER NCHECK SUM