Of control design, motor measurement, and trains

Control systems are a major part of the control engineer's day-to-day activities and there are many challenges when it comes to equipment as well as execution.
By Jack Smith July 31, 2014

In an extremely centralized design, a single process controller operates all aspects of the process. Courtesy: TriCore Inc.The cover story in this issue of AppliedAutomation covers an issue that control engineers have had to deal with for as long as there have been automatically controlled systems. How much to centralize or distribute a system actually pertains to both the control and I/O aspects of the system. As the author states, "Centralized or distributed control is a core design aspect of your system, which defines on a very basic level the degree to which your controlled objects and operations are intertwined with the control system itself. This degree of comingling is reflected in all the physical and logical components of your system. It should not be confused with the selection of a control system platform."

This issue also includes the second part of the three-part series on motor measurement from Yokogawa’s Bill Gatheridge. In this article, Gatheridge examines a three-step process for making precision electrical measurements and mechanical power measurements on a variety of motors and variable frequency drives (VFDs). He also discusses motor and VFD efficiency in systems with complex and distorted waveforms.

The third article is a case study about how the City of Milpitas, Calif., integrated its new light-rail system with traffic light controls at selected four-way intersections. According to the authors, the city wanted the trains to pass through each intersection safely without slowing or stopping for vehicular traffic in normal operation; to be able to stop the trains for certain traffic signal and pedestrian conditions; and to sense the approach of a train, change the traffic signals to stop cross traffic, and allow the light-rail train to pass through without slowing.

This article appears in the Applied Automation supplement for Control Engineering and Plant Engineering

– See the other stories in the Applied Automation supplement below.