The positive and negative effects of the regulator used in a control loop are common knowledge of the self-control professionals, and nothing new. But the concept used by Fisher-Rosemount's PROV() XDCS product is different. It is important to be aware of the differences in that it is possible to form the correct control loop on the DCS. At the heart of this concept is the introduction of an IVP (Implied Valve Position) that implies the concept of a valve position. use this. The concept of IVP replaces the concept of the traditional regulator output signal, and the concept of its positive and negative regulators is different. The meaning of this IVP always represents the opening value of the regulating valve commanded by the output signal of the regulator, but it is not the valve opening measured by the real valve position transmitter of the regulating valve, but the output signal of the regulator is sent. The valve should have an opening value after adjusting the valve. Therefore, it is called the implied valve position.
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To understand the concept of this IVP, the new concept of the regulator's positive and negative effects is not difficult to understand. The positive effect is that when the deviation of the regulator (measured as positive, set to negative) increases, the opening of the regulating valve commanded by the regulator is also increased; otherwise, when the deviation of the regulator is increased, the requirement is The decrease in the opening of the regulating valve commanded by the regulator is a reaction. From this definition, this concept is simpler and clearer than the original traditional concept. It is convenient and quick to determine the positive and negative effects of the regulator in the control loop.
The outstanding feature of this concept is that when determining the positive and negative action of the regulator in the loop, the "additional opening" (FC, customary gas-opening) and "increasing off" (FO, customary gas-off type) of the regulating valve used. The performance is left out, which makes the idea simple. Of course, in the actual control process, the FC and FO performance of this regulating valve is not allowed to be thrown away. It only breaks down a complicated problem into two simple problems to deal with. Here, the FC and FO performance of the regulating valve is treated as a parameter of the regulator itself, that is, when the regulator is configured, it is necessary to fill in whether the regulating valve commanded by the regulator is "adding on" or "increasing off" ( Content of FC or FO type). After the regulator knows the FC or FO information, it processes the signal internally—inverse to FO and not to FC. This ensures the correctness of the command signal sent to the regulating valve, and also ensures that the operator's IVP signal seen on the screen always represents the opening of the regulating valve it commands - 100,6 valves On, the O% valve is fully closed. It is not necessary for the operator to keep in mind the FC and FO of each regulating valve, so that the self-control personnel can easily determine the positive and negative effects of the regulator by the control loop.
This concept is obvious for the control system that only commands one regulating valve (or the output signal is sent to only one successor unit - regulator, auxiliary unit, etc.); and when one regulator is commanding more than one regulating valve It may cause some troubles, such as FC or FO inconsistency of two (several) regulating valves, or inconsistent requirements of the positive and negative effects of two (several) valves on the regulator. For similar problems, the first must ensure the correct control function; the second pair of regulating valve FC and FO and the regulator's positive and negative effects, according to the characteristics of the control circuit, the operator's operating habits, with one of the regulating valves Precisely fill in the FC and FO contents of the positive and negative and regulator valves in the regulator configuration. For other regulating valves, although the FC and FO and the positive and negative effects can not be satisfied in the regulator configuration, other methods must be used to satisfy the correctness of the control function. The PROVOX system has many features to meet this requirement. If it is difficult, it can also be realized by the FST programming function of I.CP point.