2/22/2018
XH430-W350
http://support.robotis.com/en/product/actuator/dynamixel_x/xh_series/xh430-w350_main.htm
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Note1) : In case of PWM Control Mode, both PID controller and Feedforward controller are deactivated while Goal PWM(100) value is directly controlling the motor through an Inverter. In this manner,
users can directly control the supplying voltage to the motor.
Note2) : Ka is an Anti-windup Gain that cannot be modified by users.
Below figure is a block diagram describing the current-based position controller in Current-based Position Control Mode. As Current-based Position Control Mode is quite similar to Position Control Mode,
differences will be focused in the following steps. The differences are highlighted with a green marker in the block diagram as well.
①
Feedforward and PID controller calculates target current based on target trajectory.
②
Goal Current(102) decides the final target current by setting a limit on the calculated target current.
③
Current controller calculates PWM output for the motor based on the final target current.
④
Goal PWM(100) sets a limit on the calculated PWM output and decides the final PWM value.
⑤
The final PWM value is applied to the motor through an Inverter, and the horn of Dynamixel is driven.
⑥
Results are stored at Present Position(132), Present Velocity(128), Present PWM(124) and Present Current(126).
Note : Ka is an Anti-windup Gain that cannot be modified by users. For more details about the PID controller and Feedforward controller, please refer to the below websites.
http://en.wikipedia.org/wiki/PID_controller
https://en.wikipedia.org/wiki/Feed_forward_(control)
Bus Watchdog (98, Available after Firmware version 38)
Bus Watchdog (98) is a safety device (Fail-safe) that stops the Dynamixel if the communication between the controller and Dynamixel communication (RS485, TTL) is disconnected due to an unspecified
error.
Communication is defined as all the Instruction Packet in the Dynamixel Protocol.
Values
Description
Unit
20[ms]
Range
0
Deactivate Bus Watchdog Function, Clear Bus Watchdog Erro
1 ~ 127
Activate Bus Watchdog
-1
Bus Watchdog Error Status
The Bus Watchdog function monitors the communication interval (time) between the controller and Dynamixel when Torque Enable (64) is '1'.
If the measured communication interval (time) is larger than Bus Watchdog (98), the Dynamixel will stop. Bus Watchdog (98) will be changed to '-1' (Bus Watchdog Error).
If the Bus Watchdog Error screen appears, the Goal Value (Goal PWM(100), Goal Current(102), Goal Velocity(104), Goal Position(116)) will be changed to read-only-access.
Therefore, when a new value is written to the Goal Value, a Range Error will be returned via the Status packet.
If the value of Bus Watchdog (98) is changed to '0', Bus Watchdog Error will be cleared.
Note: For details of Range Error, please refer to the protocol of the e-Manual.
The following are examples of the operation of the Bus Watchdog function.
①
After setting the operating mode (11) to speed control mode, change the Torque Enable (64) to '1'.
②
If '50' is written in the Goal Velocity (104), the Dynamixel will rotate in CCW direction.
③
Change the value of Bus Watchdog (98) to '100' (2,000 [ms]). (Activate Bus Watchdog Function)
