Robotis MX-12W User manual

MX-12W
1. Specifications
Item Specifications
MCU ARM CORTEX-M3 (72 [MHz], 32Bit)
Position Sensor Contactless absolute encoder (12Bit, 360 [°])
Maker : ams(www.ams.com), Part No : AS5045
Motor Cored
Baud Rate 8000 bps ~ 4.5 Mbps
Resolution 4096 [pulse/rev]
Running Degree 0° ~ 360°
Endless Turn
Weight 54.6g
Dimensions (W x H x D) 32 x 50 x 40 [mm]
Gear Ratio 32 : 1
No Load Speed 470 [rev/min] (at 12 [V])
Operating Temperature -5°C ~ +70°C
Input Voltage 10 ~ 14.8V (Recommended : 12V)
Standby Current 60mA
Command Signal Digital Packet
Protocol Type Half Duplex Asynchronous Serial Communication
(8bit, 1stop, No Parity)
Physical Connection TTL Level Multidrop Bus(Daisy Chain Type Connector)
ID 0 ~ 253
Feedback Position, Temperature, Load, Input Voltage, etc
Material Engineering Plastic

DANGER
(May cause serious injury or death)
Never place items containing water, flammables, and solvents near product.
Never place fingers, arms, toes, and other body parts near product during operation.
Cut power off if product emits strange odors or smoke.
Keep product out of reach of children.
Check the power polarity before wiring.
CAUTION
(May cause injury or damage to product)
Do not operate the product at a temperature exceeding -5 ~ +70 [°C] range.
Do not insert sharp blades nor pins during product operation.
ATTENTION
(May cause injury or damage to product)
Do not disassemble or modify product.
Do not drop or apply strong shock to product.
2. Control Table
The Control Table is a structure of data implemented in the device. Users can read a specific Data to
get status of the device with Read Instruction Packets, and modify Data as well to control the device
with WRITE Instruction Packets.
2. 1. Control Table, Data, Address
The Control Table is a structure that consists of multiple Data fields to store status or to control the
device. Users can check current status of the device by reading a specific Data from the Control
Table with Read Instruction Packets. WRITE Instruction Packets enable users to control the
device by changing specific Data in the Control Table. The Address is a unique value when
accessing a specific Data in the Control Table with Instruction Packets. In order to read or write
data, users must designate a specific Address in the Instruction Packet. Please refer to Protocol
1.0 for more details about Instruction Packets.
NOTE : Two’s complement is applied for the negative value. For more information, please refer to Two’s
complement from Wikipedia.

2. 1. 1. Area (EEPROM, RAM)
The Control Table is divided into 2 Areas. Data in the RAM Area is reset to initial values when
the power is reset(Volatile). On the other hand, data in the EEPROM Area is maintained even
when the device is powered off(Non-Volatile).
Data in the EEPROM Area can only be written to if Torque Enable(24) is cleared to ‘0’(Off).
2. 1. 2. Size
The Size of data varies from 1 ~ 2 bytes depend on their usage. Please check the size of data
when updating the data with an Instruction Packet. For data larger than 2 bytes will be saved
according to Little Endian.
2. 1. 3. Access
The Control Table has two different access properties. ‘RW’ property stands for read and write
access permission while ‘R’ stands for read only access permission. Data with the read only
property cannot be changed by the WRITE Instruction. Read only property(‘R’) is generally
used for measuring and monitoring purpose, and read write property(‘RW’) is used for
controlling device.
2. 1. 4. Initial Value
Each data in the Control Table is restored to initial values when the device is turned on. Default
values in the EEPROM area are initial values of the device (factory default settings). If any
values in the EEPROM area are modified by a user, modified values will be restored as initial
values when the device is turned on. Initial Values in the RAM area are restored when the
device is turned on.
2. 2. Control Table of EEPROM Area
Address Size
(Byte) Data Name Description Access Initial Value
0 2 Model Number Model Number R 360
2 1 Firmware Version Firmware Version R -
3 1 ID DYNAMIXEL ID RW 1
4 1 Baud Rate Communication Speed RW 1
5 1 Return Delay Time Response Delay Time RW 250
6 2 CW Angle Limit Clockwise Angle Limit RW 0
8 2 CCW Angle Limit Counter-Clockwise Angle Limit RW 4,095
11 1 Temperature Limit Maximum Internal Temperature Limit RW 70
12 1 Min Voltage Limit Minimum Input Voltage Limit RW 60
13 1 Max Voltage Limit Maximum Input Voltage Limit RW 160
14 2 Max Torque Maximun Torque RW 1023

Address Size
(Byte) Data Name Description Access Initial Value
16 1 Status Return Level Select Types of Status Return RW 2
17 1 Alarm LED LED for Alarm RW 36
18 1 Shutdown Shutdown Error Information RW 36
20 2 Multi Turn Offset Adjust Position with Offset RW 0
22 1 Resolution Divider Divider for Position Resolution RW 1
2. 3. Control Table of RAM Area
Address Size
(Byte) Data Name Description Access Initial Value
24 1 Torque Enable Motor Torque On/Off RW 0
25 1 LED Status LED On/Off RW 0
26 1 D Gain Derivative Gain RW 8
27 1 I Gain Integral Gain RW 0
28 1 P Gain Proportional Gain RW 8
30 2 Goal Position Desired Position RW -
32 2 Moving Speed Moving Speed(Moving Velocity) RW -
34 2 Torque Limit Torque Limit(Goal Torque) RW ADD 14&15
36 2 Present Position Present Position R -
38 2 Present Speed Present Speed R -
40 2 Present Load Present Load R -
42 1 Present Voltage Present Voltage R -
43 1 Present Temperature Present Temperature R -
44 1 Registered If Instruction is registered R 0
46 1 Moving Movement Status R 0
47 1 Lock Locking EEPROM RW 0
48 2 Punch Minimum Current Threshold RW 32
50 2 Realtime Tick Count Time in millisecond R 0
73 1 Goal Acceleration Goal Acceleration RW 0
2. 4. Control Table Description
2. 4. 1. Model Number (0)
This address stores model number of DYNAMIXEL.
2. 4. 2. Firmware Version (2)

This address stores firmware version of DYNAMIXEL.
2. 4. 3. ID (3)
The ID is a unique value in the network to identify each DYNAMIXEL with an Instruction
Packet. 0~252 (0xFC) values can be used as an ID, and 254(0xFE) is occupied as a broadcast
ID. The Broadcast ID(254, 0xFE) can send an Instruction Packet to all connected DYNAMIXEL
simultaneously.
NOTE : Please avoid using an identical ID for multiple DYNAMIXEL. You may face communication
failure or may not be able to detect DYNAMIXEL with an identical ID.
2. 4. 4. Baud Rate (4)
Baud Rate determines serial communication speed between a controller and DYNAMIXEL.
Available value range is 0 ~ 254(0xFE), and below is the equation for BPS calculation.
Baudrate(BPS) = 2,000,000 / (Value + 1)
Value Baud Rate(bps) Margin of Error
0 2M 0.000 [%]
1 1M 0.000 [%]
3 500,000 0.000 [%]
4 400,000 0.000 [%]
7 250,000 0.000 [%]
9 200,000 0.000 [%]
16 115200 -2.124 [%]
34(Default) 57600 0.794 [%]
103 19200 -0.160 [%]
207 9600 -0.160 [%]
NOTE : Less than 3% of the baud rate error margin will not affect to UART communication.
NOTE : For the stable communication with higher Baudrate, configure USB Latency value to the lower.
USB Latency Setting
For BPS over 250 values :
Value Baud Rate Margin of Error
250 2,250,000 0.000%
251 2,500,000 0.000%
252 3,000,000 0.000%

2. 4. 5. Return Delay Time (5)
After the DYNAMIXEL receives an Instruction Packet, it delays transmitting the Status Packet
for Return Delay Time(5). For instance, if the Return Delay Time(5) is set to ‘10’, the Status
Packet will be returned after 20[μsec] when the Instruction Packet is received.
Unit Value Range Description
2[μsec] 0 ~ 254 Default value ‘250’(500[μsec]), Maximum 508[μsec]
2. 4. 6. CW/CCW Angle Limit(6, 8)
The angle limit allows the motion to be restrained. The range and the unit of the value is the
same as Goal Position(30).
CW Angle Limit: the minimum value of Goal Position(30)
CCW Angle Limit: the maximum value of Goal Position(30) The following three modes can
be set pursuant to the value of CW and CCW.
Operation Type CW / CCW
Wheel Mode both are 0
Joint Mode neither are 0
Multi-turn Mode both are 4095
The wheel mode can be used to wheel-type operation robots since motors of the robots spin
infinitely. The joint mode can be used to multi-joints robot since the robots can be controlled
with specific angles. Multi-turn mode allows joint mode control over multiple rotations (Position
range : -28,672 ~ 28,672)
2. 4. 7. Temperature Limit (11)
Unit Value Range
About 1°C 0 ~ 100
CAUTION : Do not set the temperature higher than the default value. When the temperature alarm
shutdown occurs, wait 20 minutes to cool the temperature before re-use. Keep using the product when
the temperature is high can cause severe damage.
2. 4. 8. Min/Max Voltage Limit (12, 13)
It is the operation range of voltage.
Unit Value Range Description
About 0.1V 50 ~ 160 5.0 ~ 16.0V
For example, if the value is 80, the voltage is 8V. If Present Voltage(42) is out of the range,
Voltage Range Error Bit (Bit0) of Status Packet is returned as ‘1’ and Alarm is triggered as set
in the addresses 17 and 18.
2. 4. 9. Max Torque (14)

It is the torque value of maximum output. 0 to 1,023 (0x3FF) can be used, and the unit is about
0.1%.
For example, Data 1,023 (0x3FF) means that DYNAMIXEL will use 100% of the maximum
torque it can produce while Data 512 (0x200) means that DYNAMIXEL will use 50% of the
maximum torque.
When the power is turned on, Torque Limit(34) uses the value as the initial value.
2. 4. 10. Status Return Level (16)
This value decides how to return Status Packet when DYNAMIXEL receives an Instruction
Packet.
Value Responding Instructions Description
0 PING Instruction Status Packet will not be returned for all Instructions
1PING Instruction
READ Instruction Status Packet will be returned only for READ Instruction
2 All Instructions Status Packet will be returned for all Instructions
NOTE : If the ID of Instruction Packet is set to Broad Cast ID(0xFE), Status Packet will not be returned
for READ and WRITE Instructions regardless of Status Return Level. For more details, please refer to
the Status Packet section for Protocol 1.0 or Protocol 2.0.
2. 4. 11. Alarm LED(17), Shutdown(18)
The DYNAMIXEL can protect itself by detecting dangerous situations that could occur during
the operation.
Each Bit is inclusively processed with the ‘OR’ logic, therefore, multiple options can be
generated.
For instance, when ‘0x05’ (binary : 00000101) is defined in Shutdown(18), DYNAMIXEL can
detect both Input Voltage Error(binary : 00000001) and Overheating Error(binary : 00000100).
If those errors are detected, Torque Enable(24) is cleared to ‘0’ and the motor output becomes
0 [%].
REBOOT is the only method to reset Torque Enable(24) to ‘1’(Torque ON) after the shutdown.
The followings are detectable situations.
Bit Item Description
Bit
70 -
Bit
6
Instruction
Error
When undefined Instruction is transmitted or the Action command is delivered without the
reg_write command
Bit
5Overload Error When the current load cannot be controlled with the set maximum torque
Bit
4
CheckSum
Error When the Checksum of the transmitted Instruction Packet is invalid
Bit
3Range Error When the command is given beyond the range of usage

Bit Item Description
Bit
2
OverHeating
Error
When the internal temperature is out of the range of operating temperature set in the
Control Table
Bit
1
Angle Limit
Error
When Goal Position is written with the value that is not between CW Angle Limit and
CCW Angle Limit
Bit
0
Input Voltage
Error When the applied voltage is out of the range of operating voltage set in the Control Table
NOTE : If Shutdown occurs, LED will flicker every second.
2. 4. 12. Multi Turn Offset (20)
Adjusts offset position. This offset value is added to the Present Position(36).
Initial value is 0 and the range is from -24,576 to 24,576.
DYNAMIXEL with a Present position of 2,048 with an offset of 1,024 will return an adjusted
Present position of 3,072.
NOTE : This offset feature is only available in multi-turn mode.
2. 4. 13. Resolution Divider (22)
It allows the user to change DYNAMIXEL’s resolution.
The default Resolution Divider Value is set as 1. (1 ~ 4 available)
When resolution is lowered, revolutions (in both directions) can be increased (up to 28 turns in
each direction).
For example, a Real Position of 2048 with a Resolution Divider set as 2 will yield a Present
Position value of 1024 (2048/2 = 1024).
A DYNAMIXEL with Resolution Divider set as 2 will have a resolution 2048 for a single
revolution.
The Present Position can be obtained while Multi-turn Offset and Resolution Divider are taken
into account.
Present Position = Real Position / Resolution Divider
Present position = (Real Position / Resolution Divider) + Multi-turn Offset

For example, a DYNAMIXEL with a Real Position of 2048 with a Resolution Divider set as 4
and Multi-turn Offset as 1024 will yield a Present Position of 1535 ((2048/4) + 1024 = 1535).
NOTE : This feature is only applied in multi-turn mode and will be ignored in other modes.
2. 4. 14. Torque Enable (24)
Value Description
0(Default) Turn off the torque
1 Turn on the torque and lock EEPROM area
2. 4. 15. LED (25)
Turn on or turn off the LED on DYNAMIXEL.
Bit Description
0(Default) Turn OFF the LED
1 Turn ON the LED
NOTE : The LED indicates present status of the device.
Status LED Representation
Booting LED flickers once
Factory Reset LED flickers 4 times
Alarm LED flickers
Boot Mode LED On
2. 4. 16. PID Gains (26, 27, 28)
MX series will use the PID controller as a main control method.
P gain : value of proportional band.
I gain : value of integral action.
D Gain : value of derivative action. Gains values are in between 0 ~ 254.

Kp : P Gain / 8
Ki : I Gain * 1,000 / 2,048
Kd : D Gain * 4 / 1,000
The relationship between Compliance Slop and PID
Slope P Gain
8 128
16 64
32 32
64 16
128 8
The less the P gain, The larger the back lash, and the weaker the amount of output near goal
position.
At some extent, it is like a combined concept of margine and slope.
It does not exactly match the previous concept of compliance. So it is obvious if you see the
difference in terms of motion.
Explanation for PID required.
For the brief explanation about general PID, please refer to the website(link) below.
http://en.wikipedia.org/wiki/PID_controller
FYI, PID control theory is not only limited to the control of motor(actuator) but is a generic
theory that can be applied to all kinds of control.
2. 4. 17. Goal Position (30)
It is a position value of destination.
0 to 4,095 (0xFFF) is available. The unit is 0.088 [°].
If Goal Position is out of the range, Angle Limit Error Bit (Bit1) of Status Packet is returned as
‘1’ and Alarm is triggered as set in Alarm LED/Shutdown.