The Implementation Of IMC Based On PLC And Its Application

Time-delay system as an important part of the complex control system exists widely inmodern industry.Due to the time-delay,the controlled variable cannot reflect the effect of controlsystem in time,resulting in a significant overshoot,settling time becomes longer and the stabilityof the system deteriorates.It has brought great difficulties to the design of control system.For big time-delay object,the conventional PID controller has no ability to achieve thedesire performance.The internal model control（IMC） is an effective method to improve theprocess quality of time-delay system control.The structure and algorithm of internal modelcontrol is simple.The online regulation parameters are less and easy to adjust.IMC also has stronganti-interference ability and good robustness,especially with a significant advantage when appliedto control the big time-delay object. Internal model control system must be reasonably design tomake its superiority into full play.First on this paper analyzing the model of the controlled object， two-tank plant， andestablishing the mathematical model with the method of experimental modeling. All controlschemes have been based on internal model control.Comparing the performance between basicIMC system and IMC with filters feedback system. Doing some improvement research, designedthree kinds of improved schemes based on IMC，like IMC-PID,IMC with fuzzy compensator andIMC with model reference adaptive control(MARS).Simulating the designed four controlschemes by using Matlab tools.The simulation results validated the superiority of the IMCsystem.And the several improved IMC schemes have more excellent performance when the model mismatch.The experimental part in this paper has been done in THJ-1Fieldbus process controlequipment.The controller was SIEMENS S7-300PLC.Programming was based on configurationsoftware STEP7. Using ladder language implement the designed basic IMC scheme and IMCwith filters feedback system in actual two-tank equipment for liquid level control.Designing themonitoring program by monitoring configuration software WinCC to complete real timemonitoring of the control process. The experimental results show that IMC with filters feedbacksystem based on its advantages has good control effect when the system model was inaccurate.