The set point control strategy has low degree of freedom and bad robustness by the influence of outside interference. In order to resolve this problem and improve control quality

an improved algorithm

model predictive control algorithm based on triangular interval soft constraint

was presented. On the basis of set point control triangular interval soft constraints were added and system output reached the control objectives in stages

to reduce the influence of interference on the system and to improve degree of freedom and robustness. Finally

robustness of the algorithm was analyzed. Simulation experiment was done with the typical heavy oil fractionator model of Shell Company. Comparison with the results of set point control proved that the algorithm had better robustness and better control quality.