Topic: Process Automation Systems
AspenTech Breaking New Ground in Simulation, Model-Based Control
Resurgent Software Maker Showcases Innovations at OPTIMIZE 2013
Our Control Experts Deal with Process Dynamics
McMillan and Weiner Ask James Beall How He Approaches the Challenge of Intertwined Problems That Have Evaded Solution. See What He Had to Say
Killing Model-Based Control Dead Time
Dead Time Compensation Can Improve PID Controller Performance, but at the Cost of Robustness
Automation Could Have Prevented Fukushima, 2
Bela Liptak Discusses Automatic vs. Manual Operation of the Emergency Cooling Systems, and the Roles the Bad Designs of Control and Block Valves Played in this Nuclear Accident
White Papers: In Depth Research
I/O Solutions for Temperature Monitoring
Author: Opto 22
Sensors used for temperature monitoring and data acquisition can be quite varied. Applications ranging from simple room temperature monitoring to highly sophisticated batch process control can all be highly dependent on obtaining accurate temperature readings. The primary types of sensors used for this purpose are resistance temperature detectors (RTDs), thermocouples, integrated circuit temperature detectors (ICTDs), thermistors, and infrared sensors.
RTDs determine changes in the electrical resistance of materials in relation to temperature. RTDs deliver very precise readings (typically to 2–3 decimal places) and are manufactured in a variety of form factors. Though they are sometimes composed of nickel, copper, or other metals, historically, RTDs have been made of platinum--largely due to the fact that platinum's resistance-temperature relationship is maintained in a very linear fashion across very broad temperature ranges. RTDs' platinum composition also makes them somewhat expensive and unsuitable for applications involving temperatures above 660 °C, as temperatures above this range compromise the inertness of the platinum and may cause it to become contaminated and deliver inaccurate readings.
This white paper describes various temperature sensors such as RTDs, thermocouples, ICTDs, thermistors, and infrared sensors, and the Opto 22 solutions for using them.
Electronic Flow Control Valve (EFCV) with Pressure Compensation Capability
A new concept for an Electronic Flow Control Valve (EFCV) with pressure compensation capability is introduced. Based on its embedded sensors and micro controller, the EFCV can provide flow control without the need of load/displacement/speed information from the power elements, like hydraulic cylinders or hydraulic motors. The flow controller inside the EFCV estimates the actual flow rate by the quasi-steady flow rate equation. Experimental studies show that the analytical model is not accurate enough to cover all operating conditions. Therefore, an experiment-based calibration method is suggested so that the electronic flow controller can provide accurate flow control across the working pressure and flow range. Finally, an innovative application of the EFCV, a self-sensing cylinder, is also presented.
Flow control is one of the most critical functionalities in the hydraulic industry. Traditionally, flow control is implemented via a proportional or servo valve. The principle of proportional and servo valves is briefly reviewed in the following. When current is applied into the coil of a solenoid (proportional valve) or a torque motor (servo valve), a corresponding electromagnetic force is generated. These forces could either directly stroke the spool (single stage configuration) or indirectly move the main stage spool via regulating the hydraulic pressures on the each end of the main stage spool (multiple stage configuration). The motion of the main stage spool leads to the variation of the orifice area. With a given pressure drop, the orifice area is directly associated with the flow rate. Modeling and control of proportional and servo valves is very rich in literature /Mer67/Jel03/Eat99/. However, most proportional and servo valves on the market are incapable of providing accurate flow rate control without feedback from the power elements or without the addition of mechanical pressure compensators. For example, consider a double-ended hydraulic cylinder with the piston area equal to 1 [unit]. If the required speed is 1 [unit], then the required flow rate is actually 1 [unit]. Without knowing the displacement/speed information from the hydraulic cylinder, neither the servo valve nor the proportional valve can correctly provide the desired flow. The reason for this is because the flow rate is related not only to the spool displacement (orifice area) but also to the pressure drop across the orifice. Therefore, feedback from the power elements is often required to achieve accurate flow control.
10 Steps to Lean Electrical Controls
Globalization is forcing companies to constantly become more efficient. To drive efficiencies, many companies are implementing Lean Manufacturing to stay competitive in this ever shrinking world.
This paper will discuss how you can leverage lean operations, a lean supply chain and lean design of your electrical panels to meet the key goals from James P. Womack and Daniel T. Jones' book Lean Thinking:
- Determine what the customer is willing to pay for...this is value.
- Identify the processes required to provide value...this is the value stream.
- Physically arrange the required resources in a "flow."
- Implement "pull systems."
- Eliminate waste from the flow.
Indpendent Techniques for Ensuring Strong Security in Your Control System
Author: Thomas Burke, Eric J. Byres
This article describes two independent techniques for ensuring strong security in systems using OPC Classic technology
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