AUTOMATION OF PLC PROGRAMMING WHEN IMPLEMENTING ALGORITHMS OF GUARANTEEING CONTROL

During developing programs for programmable logic controllers (PLCs) the concept of model-oriented design is increasingly used. In particular, usage of Simulink PLC Coder is giving the opportunity to get SCL program code from Simulink model which contains certain dynamic elements. Then, for example, this SCL code can be transformed to functional blocks of the Simatic S7-300 (VIPA 300) PLC. This significantly reduces the time required to develop code in the language of SCL and reduces requirements for specialists’ qualification when developing control systems. In this article we provide an example of PLC programming automation when implementing algorithms of guaranteeing control (AGC). For certain types of technological processes it is typical to contain monotonically increasing function of the effectiveness with fixed one-way restriction in regulations. For example, in the grinders, presses, extruders the load current of the drive is stabilized using the change of feed. Energy efficiency of these plants will increase with increasing of the set point (SP) to the controller of the drive load current stabilization loop. However, an increase in SP increases the probability of triggering appropriate protection, for example, as a result of random changes in the properties of raw materials. Therefore, to avoid this accident, the power of driving motors is often unreasonably overrated. And in this case they are used with currents equal to the half of rated.Systems of guaranteeing control (SGC) are used to solve the contradiction between the need to improve the efficiency and increasing probability of an accident. In [1] the SGC theory basics are represented. SGC ensure the maximum approach of the process value PV ? y(t) to the permissible value lim? y with preassigned probability ? ,T? lim lim P y of regulations violations absence, i.e. absence of “spikes” ? ? lim y(t) y in the T time interval. The article discusses: ? block diagram of a closed-loop SGC with a calculation of permissible set point value SP; ? violations of regulations math models; ? Simulink models of probability characteristic evaluation module (PCEM) on moving time interval and set point calculation module (SPCM). Is is described how to get Simatic S7-300 PLC functional blocks using Simulink PLC Coder. A LAD program of SGC implementation is shown.