There is no direct way to command a Dynamixel to stop. And there is no way to set the speed to 0, since the value 0 is specially interpreted to mean 'as fast as possibly'. The best we can do is command it to move to its current position and set the speed to 1 to slow it down as much as possible. If there is any significant lag between receiving the CurrentPosition and setting it and the speed, there will be some residual movement as the Dynamixel moves to its observed but stale CurrentPosition. If the Dynamixel is in Sychronized mode, a call to 'DynamixelNextwork.Synchronize' will be required to complete the operation.