Improved operational pattern-PID based control of ORP in cobalt removal process using arsenic salt

To solve the problem of stability control of Oxidation-Reduction Potential(ORP),which is caused by time variation,nonlinearity and time-delay in the process of cobalt removal using arsenic salt,an improved operational pattern based PID parameter tuning method is put forward.In order to improve the reliability and speed of operational pattern matching,first,an improved fuzzy C-mean clustering algorithm for operational pattern clustering is presented.Then,a two-step search method is used to match the similar operational patterns.Finally,since the system parameters of the cobalt removal process vary with time,to improve the reliability of the reused operational pattern solutions,which are PID parameters,different weighting values are assigned to the operational solutions indifferent times when the operational pattern is reused.A real industrial cobalt removal process control results show that the proposed method can effectively reduce the fluctuation of ORP degree and deal with complicated changing conditions.