ABB H&B Publication 60-0.15 EN

ABB H&B Publication

Certain industrial processes or applications necessitate controllers which satisfy safety engineering requirements. For instance, heat generating plant which is heated with fluid, gaseous or solid fuels requires controllers which meet the requirements of DIN 3440 [6]. This also holds for controllers used in heat-generating or heat-transfer plant which, irrespective of the type of heating energy, heat a thermal transfer medium such as water, steam, oil or air. Land-type boiler systems must use water-level controllers which meet the specifications of VdTÜV Data Sheet No. 100/1 [7] and thereby satisfy the requirements of the "Technical Guidelines for Steam Boilers" (TRD). Controllers with corresponding approval are also required for boiler plant with only limited or periodic monitoring. Controllers used on sea-going or inland waterway vessels, or in offshore facilities, have to satisfy the requirements of Germanischer Lloyds. Hartmann & Braun controllers satisfy these requirements.

Matching the controller to the controlled system Matching the control parameters Xp, Tn and Td to the control application and the controlled system is often referred to as optimization. However, optimization is a decision process which precedes parameterization. In the optimization phase a decision is made as to whether the controller should – adjust for a set point deviation as rapidly as possible, accepting that an overshoot may result – adjust for a set point deviation without any overshoot – compensate for disturbances in an optimal manner – reach the set point with the lowest power consumption – u. a. m. Once the target has been established, the control parameters can be determined and set on the controller. 3.1 Manual determination and setting of control parameters The parameters Xp, Tn and Td are established for controllers by – trial and error – experience – evaluation, for instance of transfer functions using a rule of thumb or – the use of mathematical methods. PC programmes are used here. These approaches are in general very time consuming and often too imprecise to achieve optimal results at the first attempt. Consequently, there has long been a need for controllers which find their own parameters and adapt themselves. 3.2 Adaptive controllers The term "adaptive controller" is inadequate to describe the function of such a controller. VDE/VDI Guideline 3685 gives more details on the classification of the various options:

"An adaptive control system is one in which characteristics which can be influenced are automatically set to variable or unknown process characteristics so as to elicit an improvement. The terms self-setting, self-adapting and self-optimizing in the sense of this definition are all synonyms for the term "adaptive" [8]. Such an adaptive system is described by reference to Fig. 12: "Identification in an adaptive control system serves to establish the characteristics of a system or part system." "In the decision process, that information received about the identification is compared to th

Realization in H & B controllers Start-up adaptation is realized in H&B controllers under the designation self-parameterization. This simplifies and speeds up the start-up process and leads to better control performance than the usual methods in which exact measurements are often omitted to save time and the parameters are only approximated. Control of the parameters through the set point, the controlled variable or other measured signals is a simple matter with Hartmann & Braun controllers. Since no general approach is possible for such tasks, a special configuration has to be drawn up for such applications by either Hartmann & Braun or the operator. Self-parameterization can be a valuable aid to establishing various parameters for different loading conditions. 

Two interfaces, of equal functional value, are available for different applications. A configuration interface which can be accessed from the front allows the functions parameterization, configuration and feedback documentation to be carried out. The controller itself is generally off line whilst they are being carried out. The computers used for this are mostly portable so that they can be used at different sites. They are connected to the controller via an adapter cable. The rear interface allows the control of one or more units via a bus. Although this interface can also be used for configuration and parameterization, the bus is best used for operational (on-line) functions. For these tasks the computers are generally stationary, with a fixed connection to the controller.

Computer applications Hartmann & Braun offers complete, powerful software programmes for the functions operation and monitoring as well as process visualization, parameterization, configuration and feedback documentation. The applications set point control and direct digital control are in most cases so closely bound to the controlled system that no generally-valid programmes can be written for them. The interfaces, however, are documented such that coupling programmes can be written