There are many ways in which emergency stops are implemented in a machine. This topic discusses possible methods of halting the RMC in the event of a machine fault situation.
One option is, of course, to shut off power to the RMC, which may not be desirable. Aside from removing power, the RMC can only programmatically respond to an estop signal.
General Considerations
In a machine fault situation, the following actions are typically desired of the RMC:
Halt all the axes
The RMC has several levels of halts.
Turn off any Enable Outputs
If any Enable Outputs are wired to a motor drive, or other actuator, these are typically turned off in a fault situation. The Direct Output Halt will halt the axis and turn off the axis' Enable Output.
Stop User Programs
Any user programs that are running should be stopped to prevent commands from being issued to the axes.
Stop the Program Triggers
The Program Triggers should be stopped to prevent user programs from starting. To stop the Program Triggers, put the RMC in PROGRAM mode.
Turn off discrete outputs
Certain discrete outputs may need to be turned off.
Additional machine considerations:
Blocking Valve
If the RMC halts the hydraulic axis with an Open Loop or Direct Output Halt, the cylinder may drift. If drifting is unacceptable, install a blocking valve that will close when the machine faults.
Using the Fault Input to Halt Axes
If the Fault Input Auto Stop is set to a halt, then when the Fault Input becomes active, that axis will halt, and any new motion will be prevented as long as the Fault Input is active (except for the Direct Output (9) command). The polarity of the Fault Input can be set to Active High or Active Low.
Each Fault Input will only halt its corresponding axis. If you want to use the Fault Input on several axes on the RMC, you will need to wire them all. If you instead want to use only one discrete input to halt the axes, see the Using a Discrete Input to Halt Axes section below.
The modules listed below have a dedicated Fault Input.
|
RMC75 |
RMC150 |
RMC200 |
|
CA4 - dedicated CV8 - input can be configured as Fault Input |
For modules that do not have a Fault Input, you can use a general discrete input to halt the axes, as described in the Using a Discrete Input section below.
The Fault Input can also be used to put the RMC in PROGRAM mode, thereby stopping all user programs and the Program Triggers. See the RUN/PROGRAM Mode section below.
Using a Discrete Input to Halt Axes
There are several ways to use a single general discrete input to halt the axes:
Use a single discrete input to halt axes and enter PROGRAM mode
For any axis, you can assign the Positive Limit Input and Negative Limit Input (on any number of axes) to the same discrete input. If the AutoStops are set to halt on the Positive Limit Input and Negative Limit Input errors, this will cause the axis to halt when that discrete input is active. The polarity of the limit inputs can set with the Limit Input Polarity parameter.
In addition, the same discrete input can be used to put the RMC in PROGRAM mode, thereby stopping all user programs and the Program Triggers. See the RUN/PROGRAM Mode section below.
Use a single discrete input to trigger a shutdown user program.
You can make a user program that issues the Fault Controller (8) command, and configure the Program Triggers to start the program when a discrete input turns on. This will halt all the axes, and put the RMC in PROGRAM mode. The disadvantage of this method is that the discrete input is not forcing the RMC to remain in an error state, and therefore, any motion command issued to the RMC from another source—such as a PLC or RMCTools—can cause motion.
RUN/PROGRAM/Disabled Mode
A discrete input can be configured to put the RMC in RUN mode or PROGRAM mode (RUN or Disabled for the RMC200). When the input turns on, the RMC will enter RUN mode. When the input turns off, it will be in PROGRAM mode (Disabled mode for the RMC200). This input can be a general discrete input, or any axis' Fault Input, and can simultaneously function as described in the Using the Fault Input to Halt Axes and Using a Discrete Input to Halt Axes sections above.
To configure the RUN/PROGRAM/Disabled mode input:
In the Project Pane, right-click Programming and choose Properties.
On the RUN/PROGRAM or RUN/Disabled page, check Define a RUN/PROGRAM discrete input or Define a RUN/Disabled discrete input.
Choose the input you wish to use and click OK.
Notice that the state of the RUN/PROGRAM/Disabled mode input does not always reflect the RUN/PROGRAM state, because the RUN/PROGRAM mode can be changed by other methods.
Configuring Discrete Outputs
You may wish to set certain discrete outputs either on or off when the machine faults. The Discrete I/O Configuration has options for what states the discrete outputs should take on when the RMC enters PROGRAM mode or receives a Fault Controller command.
See Also
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