IAI RA Series, Инструкция по эксплуатации

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7. Details of Features
164
7.2. Transmission Cycle of MECHATROLINK Communication
The cycle of message sending and receiving between master and slaves in the MECHATROLINK
communication is called the transmission cycle.
The transmission cycle of the MECHATROLINK communication in the extension motion control
feature is 1ms or 2ms. When communication is performed in 1ms of transmission cycle,
improvement of operation performance could be expected in the ways of tracking accuracy and
response speed of an axis to the movement commands compared to 2ms of transmission cycle.
The transmission cycle can be fixed to 1ms or 2ms in Extension Motion Control Common
Parameter No. 52 “Fieldbus Transmission Cycle Select”.
However, in case there are too many connected slave axes or retries (set in Extension Motion
Control Common Parameter No. 7) to the set transmission cycle, the communication fails to be
established, which could cause such errors as Error No. 5B0 “Extension Motion Control Fieldbus
Initialization Error”.
Having T as the time spent for one time of communication between the master and slaves, the
possibility of communication establishment can be expressed roughly with following conditions.
T < Transmission Cycle … Can be Established
T > Transmission Cycle … Cannot be Established
In the MECHATROLINK communication in the range of use for the extension motion control, the
elements that give influences to the communication time T can be considered mainly as shown
below.
(1) Number of Slave Axes
As the number of slave axes increases, the subject for
handshaking also increases, which result in making the
communication time T longer.
(2) Slave Type
(multi-axis type or single-axis
type)
Because the multi-axis controller requires less number of
connection relay stations than the single-axis type controller
with the same number of axes, the communication time T will
be shorter. Also, when the multi-axis type controller is mixed
with the single-axis type controller for use, first connecting to
multi-axis type and then to single-axis type, viewing from the
XSEL, will shorten the communication time T because of the
same reason as above. (In the case of cascade connection)
(3) Way of Slave Connection
(Star or Cascade)
Rather than linking the slaves in a row (cascading connection),
the communication time T will be shorter with connection in
radial directions (star connection) using a MECHATROLINK
hub as it requires less number of communication relay
stations.
(4) Setting of Number of Retries
The communication time T will be longer with higher number of
retries.
(5) MECHATROLINK Cable
Length
Simply longer cables make the communication time T longer.
However, in case of cables with standard length (up to a few
meters), the influence is relatively small compared to (1) to (4).
ME0364-2B