Servosila-SC-25-Programming-Guide

Message Flows
Sending COMMANDS to devices
The control computer is expected to continuously send commands
2
to each of the Servosila SC25
Brushless Motor Controllers on the network. If such a continuous stream of commands suddenly
stops coming to a motor controller, the controller assumes that there is a network fault or a
failure in the parent control system. In such a case, the controller stops its motor as a safety
measure, and might enable a brake function depending on configuration settings.
How often the commands need to be sent depends on “heartbeat timeout” configuration
parameter of each of the controllers. The parameter is set using the “Servoscope” software. The
controller expects to receive at least one message from a control computer within the configured
time interval. Otherwise, the controller times out, and halts the motor as a safety measure.
Typically, a control computer would continuously send a “Servo” command with a target
position or an “Electronic Speed Control” command with a target speed, - or any other command
understood by the controller. If a target position or a target speed has not changed since the
previous time the command was sent, the control computer just re-transmits the previously sent
command with the same target value.
Note that CAN bus does not guarantee delivery of messages (frames), and the controllers do not
send back any acknowledgments confirming that a command has been received or executed. As
such, the control computer shall rely solely on the method of continuous streaming of commands
to ensure guaranteed delivery of the commands, assuming that most of the commands get
through to the controllers.
2 The commands are delivered as CANopen RPDO messages.
10 www.servosila.com
Control Computer / PLC Brushless Motor Controller
Continuous stream of
commands
command
command
command
...
The interval between
consecutive commands
should be less than the
controller’s heartbeat
timeout period, a
configurable parameter.
Otherwise, the controller
assumes that there is a
failure, and halts the motor
as a safety measure.