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It is widely known that pulp quality indicators are difficult to measure by on-line sensors. In this research special effort was devoted to investigating the disturbances which cause measurement errors in on-line drainage meters. The matter was studied theoretically as well as in practice. Estimators have been developed with which the influence of the worst disturbances was compensated. In this manner it was possible to increase the adaptability of on-line drainage meters in freeness control systems. The integrated control of a grinder room has been improved by using the experience gained from the AGMO (Automatic Groundwood Mill Operator) -system. It has been shown that the mathematical models predicting the operation of grinders can be simplified which in turn makes their on-line identification easier. The algorithm for computing the setpoint of the grinders has successfully been modified into a form which demands fairly small computer capacity. The freeness of the compound pulp produced by the stone group can be kept constant and simultaneously the production rate can be changed in a fairly wide range. The factors which affect the production rate of a grinder room and the specific energy consumption during a long period of time (such as freeness limits of one grinder and sharpening) were investigated by simulation. The simulation study indicated that better control of stone sharpness would raise the production capacity of a grinder room by 10-40% without degrading the pulp quality. The results of the project indicate clearly that by developing the automation of mechanical pulping processes the pulp quality variation can essentially the reduced and specific energy consumption can be decreased. To successfully use the results however the characteristics of the particular plant must be taken into account in planning and implementation. The grinder room control system developed in this project is ready to be utilized more widely. (ERA citation 12:008309)