Delta RMC151 - Manual (Page 193)

3 Controller Features
3.9.6. Mean Squared Error
The Mean Squared Error (MSE) is a quantity that can be included in a plot. The MSE is a single
number that indicates how closely two other plot quantities are to each other during the entire
plot. The closer the quantities are, the smaller the MSE will be.
The Mean Squared Error is typically used during manual tuning as a measure of how close the
Actual Position, Velocity, Pressure or Force is tracking the Target. As the tuning progresses,
the MSE should become smaller, indicating that the actual value is tracking the target more
closely. The actual value of the MSE is not necessarily important. The importance is that the
MSE decreases.
Notice that the Mean Squared Error should not be used as the main guide for tuning. Tuning a
system solely to achieve the lowest MSE possible may result in a system that is tuned very
close to instability. Any change in the system, such as temperature or load, may cause the
system to begin oscillating.
Adding the MSE to a Plot
The Mean Squared Error is included in default plots for control axes. To add the MSE to a
custom plot, do the following:
1. In the Plot Template Editor, click New Quantity.
2. On the Advanced tab, in the Formula box, choose Mean Squared Error.
3. To choose the MSE for the position, velocity, pressure, or force, choose Standard
Error Quantity and select the axis and quantity.
To choose the MSE for any other values, choose Custom Error Quantity and select
the two registers.
4. Click Finish, then download the Plot Template to the RMC. The next plot captured for
that plot template will include the MSE.
Mathematical Definition
The Mean Squared Error is the average of the square of the difference. The difference between
each sample is squared, and the average of all the differences is the MSE.
3.10. Custom Feedback
3.10.1. Custom Feedback
Custom feedback gives the flexibility to use feedback from a source other than directly from a
hardware input. Custom feedback requires that the user create a user program that
continuously calculates some value to be used by the axis for feedback. Custom feedback
requires firmware 3.54.0 or newer.
Custom feedback has many uses, including the following applications:
• Controlling to the sum, difference, or average of feedback devices
Custom feedback makes it possible to control to the sum of the forces of multiple
hydraulic cylinders, control the difference between two actuators, or control the average
of actuator positions.
• Switching feedback
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