Customer Solutions

PACs Deliver Faster Response Times with NI PXI and LabVIEW Real-Time to Automate Cold Steel Rolling Process

Author(s):

Shekar Patil, Pitel Engineering

Industry:

Basic Materials - Steel/ Lumber/ Construction

Product:

Data Acquisition, LabVIEW Real-Time, PXI/CompactPCI, Programmable Automation Controllers (PACs)

The Challenge:

Implementing a compact, closed-loop control system for online gauge monitoring and control in cold rolling mills to deliver high-precision monitoring combined with faster response times than traditional PLCs and ensure continuous operation, 24 hours a day, seven days a week, with minimal human intervention.

The Solution:

Developing a National Instruments programmable automation controller (PAC)-based gauge monitoring and control system using NI LabVIEW Real-Time and PXI hardware.

Control System Implemented Using NI Products

NI PAC Platform with PXI and Real-Time Best Fit for High-Precision Monitoring

The ferrous and nonferrous metal industry uses a cold rolling mill to obtain metal strips (in the form of coils) with uniform thickness. These mills require a high-precision monitoring and control system. The PAC control system monitors the metal sheet thickness in real-time and controls the gauge with a fast and deterministic response time. The system has two rolls, one fixed and one moveable, connected to the hydraulic cylinder. The moveable roll applies the required pressure on the steel sheet based on the input signal to ensure correct gauge of the sheet.

After evaluating various platforms for this complex application, we selected the NI PAC platform and then chose LabVIEW Real-Time and PXI hardware. With the PAC products from NI, we decreased development time while reducing the cost for our clients.

The control system uses thickness gauges to measure the metal strip thickness and provide the deviation from the setpoint in microns as an analog input to the PXI hardware. The pressure provides the hydraulic cylinder pressure as an analog voltage.

The position transducers determine the hydraulic cylinder position and provide a digital input to the controller that correlates to the metal gauge (or the gap between the rolls). The encoder is attached to the rotating deflector roll and indicates the speed at which the strip is rolled out. With the data received from the various sensors, the PXI controller running in LabVIEW Real-Time responds to the inputs and generates an output to change the hydraulic pressure, thereby controlling the metal strip gauge.

PXI and LabVIEW Create Reliable System

We implemented the control system using a PXI controller running LabVIEW Real-Time. The PXI system uses three different modules. We used the NI PXI-6040 for analog input/output to assimilate the thickness and pressure data. In addition, we used the NI PXI-6602 counter card to measure signals from the encoder and determine the speed. We used the NI PXI-6711 analog output module to control servo valves used to change the hydraulic cylinder position that controls the gauge or thickness of the steel. Another challenge we encountered was to provide a regular push button control panel to be used in times of contingency, such as when the connection of the real-time system to the host fails. We overcame this challenge using the NI PXI-6527 industrial digital input/output module.

Single Development Environment Reduces System Development Time

Compared to traditional instruments and PLCs, we increased flexibility, reduced response time, and improved product quality using the NI PAC platform. In a typical PLC-based system, the control loop rate is 100 to 500 ms, but with the PXI-based control system, we reduced the loop rate for this system to 10 ms, increasing the quality of our output. We also used the PXI backplane to synchronize measurements. Finally, because we used a single development environment and flexible hardware, we reduced the system development time by a factor of one-sixth, reducing the total cost of project ownership.

For more information, contact:

Shekhar Patil

Pitel Engineering

#128 Vardhman Industrial Complex

LBS Marg Gokul Nagar

Thane, Maharashtra

Tel: (91) 222-537-5766

Fax: (91) 225-542-7371