Adaptive Environment Simulation and Test Control

Introduction

An environmental simulation and test is used to determine a product's ability to perform during or after exposure to a specific environment. These tests are often used to prove product integrity, verify operational limits, determine warranty terms, and prepare procedures for safe operations.

CyboSoft, a NI Alliance Partner in Rancho Cordova, California offers an innovative Model-Free Adaptive (MFA) control solution for controlling environmental test equipment without having to tune controller parameters. Climatic chambers, rapid thermal processing (RTP) chambers, wind tunnels, dynamic simulation and testing apparatus all have critical control loops. The MFA controllers embedded inside the NI LabVIEW environment can tightly control these critical loops and can adapt to new test conditions so that tedious and costly manual tuning of controller parameters can be avoided.

Leveraging National Instruments LabVIEW Real-Time development environment, the embedded MFA controllers can run in a PC or be downloaded into NI's FieldPoint distributed I/O or PXI instruments. Using NI's MX-2 card, the system can also connect to VXI based systems to provide an integrated, adaptive environmental test control system.

Solution

Why is Environment Test Control Difficult?

Components and products may be used in different environments during their lifetime. To ensure their operability in severe conditions, simulation of environmental conditions ranging from high temperature and humidity to a cold and dry atmosphere might be required. Components and systems requiring environmental testing include engines, turbines, compressors, motion systems, vehicles, aircraft, aerospace materials, semiconductor equipment, mechanical systems, and robotics.

Since environmental tests require establishing certain stable test conditions, an automatic control system to control all critical process variables is important. However, when the environmental conditions vary from test to test, the process dynamics may vary significantly. If PID controllers are used, frequent manual tuning of controller parameters is required resulting in low efficiency and a waste of time and resources.

MFA Controller vs. PID Controller

The following trends shown in LabVIEW demonstrate MFA (top) and PID (bottom) controllers are controlling 2 identical second order processes. As we begin, both are controlling well. Then, we change the processes to second order plus delay processes. Due to the large delay time, both control systems start to oscillate, but the MFA is able to quickly adapt to provide good control, while the PID will continue to oscillate. When the setpoint is changed again, there is no oscillation with MFA, which continues to provide good control.

This demonstration shows the adaptive capability of a SISO (single-input-single-output) MFA controller that is ideal for environmental simulation and test control.



SISO MFA Controller Configuration in LabVIEW

A SISO MFA has only a few parameters to configure including Sample Interval, Controller Gain, Kc, and Process Time Constant as shown in the following bitmap.



NI PXI Based MFA Control System

National Instruments PXI products provide an ideal hardware platform to implement an environment simulation and test control system. The following table lists all the components and part numbers required. Both options can implement at least 2 MFA controllers. You may select NI's FieldPoint or Compact FieldPoint products to implement this system as well. See the "pH Control" solution and "Nonlinear Control" solution for detailed product info and part numbers.

Option 1. Remote I/O Option (MFA running in PC)

Option 2. Embedded Real-Time Option. (MFA running inside PXI)

CyboSoft's Embedded MFA Control Software in LabVIEW

The following table lists the required embedded MFA control software to be ordered from CyboSoft. A SISO (single-input-single-output) MFA controller can be configured as one of the following MFA controllers.

• SISO MFA to replace PID to eliminate manual tuning,
• Nonlinear MFA to control nonlinear processes,
• MFA pH controller to control pH processes,
• Feedforward MFA to deal with measurable disturbances,
• Anti-delay MFA to control processes with large time delays, and
• Robust MFA to protect the process variable from running outside certain boundaries.

Summary

MFA controllers are ideal for environmental simulation and test control. Avoiding process models means lower development costs and faster time to market, more robust and precise control means better lab test results, and no manual tuning means lower operating costs and longer up time.

This general-purpose, powerful solution can be easily implemented. No special knowledge or experience with advanced control or process modeling is required. Tedious manual tuning of controllers can be eliminated allowing the user to focus on R&D, design, proto-typing, and testing.