Jun
25
To ease operator transition from panel-based systems to monitor-based systems, the manner in which first generation Distributed Control Systems (DCS) displayed information often mimicked the way this information had earlier appeared on the control panel. Since the control interface provided by the control panel was familiar and had proven to be effective, a similar presentation …
Jun
11
The SC65E WG7 committee met May 28-June1, 2012 in Meisdorf, Germany. In this meeting the committee addressed work that is part of the maintenance cycle for IEC61804 – Function blocks (FB) for process control. Also, much of the meeting discussion focused on work related to the development of IEC 62769 Field device integration (FDI) standard. …
May
28
I was honored to be one of the three plenary speakers at the IFAC PID’12 conference. My presentation was scheduled on the last day of the conference, Friday, March 30, 2012. The topic of my talk was PID Advances in Industrial Control. In this presentation I address the fact that major advances have been made …
Jan
02
In June, 2100 the International Electrotechnical Commission (IEC) distributed a new project proposal 65E/199/NP, Devices and integration in enterprise systems; Field Device Integration (FDI) – Part 1 to 7. Voting on this proposal was completed in October, 2011 and the new project was approved. Within IEC the SC65E WG7 committee will address converting the draft FDI …
Oct
03
The analog output block action on loss of power, that is, fail open or fail closed, is defined in Foundation Fieldbus devices through the configuration of the IO_OPTS parameter. Also, as addressed in Control Loop Foundation – Batch and Continuous Processes, this parameter is also used in DCS systems that have adopted the function blocks …
Sep
26
The process gain may be negative or positive depending on the process design. To provide the correct response a feedback control block must take into account the process gain direction—whether to increase or decrease the manipulated input to correct for a control error. For example, the inlet flow to a tank may be manipulated to …
Jan
24
One of the fundamental limitations of single-loop control is the fact that all control action is based on the error between the setpoint and the controlled parameter. If there is no error, then the control output will remain at its last value. To correct for process disturbance input using single-loop control, the disturbance input must …
Dec
13
As noted in a previous post, when work on Foundation Fieldbus specification was completed in 1994, there were very few fieldbus products on the market and even fewer control systems that supported these devices. The Fieldbus Foundation function block team discussed the need to communicate the advantages of fieldbus to inform the industry of this …
Feb
28
Many control systems have traditionally provided some capability to limit the rate of change in a setpoint value used in control. When a setpoint change exceeds this rate of change limit, then the rate limited value is use in control. Thus, the full setpoint change is not immediately seen in control until the rate limited …
Jan
26
With the introduction of digital field devices, manufactures of control systems and maintenance tools were faced with the challenge of how to access and display information in devices that were produced by different companies. Over the years, a number of approaches have been developed. However, the Electronic Device Description Language (EDDL) is the dominant technology …
