multiple feedback closed loop


I am planning to use RMC150E controller for a position control application where I have four feedback signals and operator can select which input to select for loop control. How can I implement that?

Further, I also need to implement some “freeze” logic, like if the feedbacks differ each other by more than some values, it will actuates DO and freezes the actuator. For that, I need to access the analog inputs and compare them. Any suggestion?

In addition, the set point is calculated by a PLC which will provide the set point values on the analog input of the RMC150. How can I configure the RMC150 to read this analog input as the set point?

I am very new to this product so please provide detailed answer.



This is tricky, but can be done. First, a position control axis on the RMC150E can only control to a single physical input, and connot switch on the fly. There are methods of switching the axis feedback, but it requires programmatically restarting the RMC.

Therefore, other methods must be used. Here are a couple methods:

  1. Use an Analog Output to output the value to the controlled physical input
    With user programs, you can determine which feedback to use, then use the Direct Output command to output that feedback value as a scaled voltage from a Control Output. Connect that Control Output to an analog input, and use that analog input for your control axis.
    The drawbacks are:

    1. Uses an extra Control Output and an extra analog input.
    2. Adds a delay of one or two loop times in the signal. However, it is possible that this is not a problem, since many hydraulic control applications do not need such fast update rates. Also, if it is only one axis of control, you can set the Loop Time on the RMC150Eto 500 microseconds, which will minimize the effect of the delay.
    3. The analog signal can cause a loss of resolution. For example, several the RMC100 modules have 12-bit outputs. The RMC75 modules have 16-bit outputs.
  2. Use a U/IO output (RMC150 Only)
    With user programs, you can determine which feedback to use, then store that value in a variable. You can output that variable to an SSI output on the UI/O mdoule, then input it to the other channel on the same UI/O channel, and use that input as an axis input.
    The drawbacks are:

    1. Uses two high-speed channels on the UI/O module.
    2. Adds a delay of one or two loop times in the signal. However, this is often not a problem on many hydraulic systems.

We have actually used both of these methods, and they will work. If you need more assistance on how to set this up, we will be happy to help.

Thank you Jacob. This definatly helped me to move forward.

Well, I have four resolver feedbacks and was wondering how can I read them and send one of them, based on the operator choice, to the axis input. I was finding it difficult to even access the analog inputs. Based on your reply, I created one position control axis with second SSI input of the UI/O as the feedback, five position reference axis (four for the feedbacks and one for the set point) and configured UI/O’s first SSI channel to output one memory address. Now, I am planning to access all the feedback inputs and based on the operator selection (coming from Modbus TCP), copy the proper input value to the memory for the first SSI channel.

I have a question on the scanning of the program. Please follow the link: scanning of the program.

I really appreciate your help. Thanks again.

I liked this way but I am worried about the accuracy of the signal. The RMCTool’s help for analog H cards says, the output is only 12bit and tolerance at 10V is from 200mV to -100mV, ie 2% accuracy, that is not very accurate signal.

Yes, that is certainly a drawback. I edited the post above to include that drawback.