deviation. The second step allowed comparison between variables with different units. Figure 22 illustrate the effects on the data.
Figure 22 The data is normalised by subtraction of the mean value and by scaling with the standard deviation. Treating the data like this allowed plotting of variables with very different units in the same figure while retaining the qualitative characteristics of the variation in the data. A consequence of this data treatment was that two variables that were directly proportional to one another would get the exact same shape if both were normalised. 5.2
TESTS OF CONTROLLER
Originally, a series of several tests had been planned. These would include a number of initial experiments used to decide suitable values of t, u and a suitable DO-range as well as tests with both a constant and a varying ASL. However, due to problems with the implementation the initial experiments had to be skipped and only three tests could be performed. A summary of the settings used during these tests is presented in table 4 below. Table 4 Summary of the settings used for the tests of the controller. Test No
Min DO [mg l −1]
Max DO [mg l −1]
u [mg l −1]