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Success Stories

March 24, 2016

TRW Using Gantner for Custom PID Controlled Equipment Testing

Overview                                                                                                                    

TRW is a world leader in foundation brake systems and a pioneer in electronic braking. As part of ZF, TRW develops innovative automotive braking systems that combine proven brake function with advanced functionality. With TRW looking to update and upgrade their brake test stands for product simulation and measurement with high accuracy, they turned to the hardware and software offered by Gantner Instruments.

 

The Problem

TRW Automotive needed a way to run a control loop feedback mechanism to control and monitor the servo and hydraulic (fluid) controls of 6 independent stations using the PID to control the servos and hydraulics.  Over the years, they have been looking for a way to remove erratic valve behavior and improve measurement quality and reliability. Some of the major obstacles that were:

  • How to provide closed loop PID control of a servo system with high accuracy and minimal overshoot, at a loop response rate of up to 2kHz (500 µs)
  • How to increase the response and accuracy of the PID controller
  • How to implement a superimposed ripple frequency to cause vibration and improve valve linearity and response.
  • How to archive, organize, and visualize live data, and present this data in a spreadsheet format for detailed analysis.
  • How to interface and integrate with a LabVIEW storage platform.

Time was of the essence as TRW needed to get this system up and running quickly, to facilitate test schedules in a high demand environment. Gantner provided off the shelf hardware with custom programming that could be integrated into their system at a competitive cost.

 

The Proposal

The speed and precision of the Q.series products allowed Gantner to meet the requirements of this project. The scalability of the Q.series provided the best solution for a high performance automation system with synchronization and the ability to connect to any host system, including:

 

  • Q.bloxx A106 Measurement Modules :

The module Q.bloxx A106 was selected to provide precise, galvanically isolated full bridge measurements at high dynamic acquisition rates, while also having an analog output to generate the voltage for the servo signal, and a digital output to generate a process out signal. It also has a configurable sensor excitation, allowing for the use of carrier frequency (CF) technology for high resolution, long-term stability, and immunity to noise at a frequency of up to 4.8 kHz.

 

  • Q.station Controller:

The power and performance of the Q.station provided the platform necessary to handle all of the synchronization, computation, interface screens and data management for the application – without the need the need of a connected PC.  The Q.station’s PAC functionality allows it to work independently of a PC. The Q.station also has a built in screen to display custom interface screens and live data.

 

  • test.commander Configuration Software:

The configuration and visualization capabilities of test.commander provided a very cost effective, off-the-shelf solution to easily configure the complete application – all with fill-in-the-blanks menus and not one line of programming code.  test.viewer (a component of test.commander) was also used to visualize real time and archived data using familiar trend chart and oscilloscope formats.

 

  • test.con Programming Software:

The programming capabilities of test.con provided a highly customizable solution to graphically program and display interface screens (HMI). Using drag and drop variables and macros, not a single line of code was needed to program the Q.station. Due to the controller’s PAC functionality, the custom program is downloaded onto the controller for a stand-alone embedded control solution.

An important goal of this project was to be able create a custom project that would reliably and quickly communicate with the test equipment using standard components with an easy to use interface.

The Gantner Solution

The approach was to use 1 Q.station connecting to 8 Q.bloxx A106 modules, with each connected to and monitoring independent stations. The off the shelf nature of the Q.series system allowed for the rapid deployment of the system solution. The PSI full bridge values from the test stations were measured through the A106 modules. The data was processed through the setpoint values and custom PID program on the Q.station, and then processed back to the test stations through the module’s analog and digital outputs. Through the controller, the parameters were run through its virtual variable setpoints for the program and the onboard digital outputs for the A106 modules, which provided the start/stop triggers.

Setup Overview

In test.con, macro programs were created using the library of built in function blocks to control the pumps and sends commands to the pump and injector. Input data from the pump was run through the PID controller to adjust the gain and was then sent back to the testing equipment. The controller minimized the error to adjust the control variable, which was the position of the control valve.

Custom PID Program
Pump Control Function Block

The system was designed to have a central station, the Q.station controller, to remotely control the independent stations through the Q.bloxx-A106 module via the RS485 port.

Test Stand Enclosure

Since TRW used LabVIEW previously as a company storage platform, it was imperative that the Gantner program communicate effectively. The software was able to interface with LabVIEW by creating variables in test.commander. Through the use of these setpoint variables, the software was able to output to LabVIEW to control that servos based on the feedback from the PID.

Author: Juergen Sutterlueti

Juergen Sutterlueti is Gantner Instrument's Vice President, Energy Segment and Marketing.

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