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Grinding rate [t/h]
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
1
2
3
4
5
6
Rate of change of mass fraction x1, (solid: system);
(dashed: observer)
Figure 12: Observer convergence for unknown input
7 DISCUSSION
As a case study of mineral processing, the wet
grinding ball mill operated in continuous or fed-
batched mode has been studied. Simulation results
showed that significant part of the steady state error
is due to the model part and thus independent of the
observer design methodology. The robustness
against parametric and structural uncertainty can be
increased, although this will increase the noise
sensitivity. Since we herein want to track only the
truly time-varying features of the process dynamics,
the state observer designed strategy is satisfactory.
The load within the mill should be controlled at a
well chosen level because too high levels of the load
in the mill create process disturbances. The output
product fineness depends on the solids rate flow. In
view of the approximations involved in this
treatment, the agreement between the observer and
the model is remarkable. The estimation of the
observer converges to zero exponentially.
8 CONCLUSION
We have described symbolic computations for
reducing a nonlinear system to observable forms.
These tools can be applied to systems that are
linearly observable, locally observable with zero
input or merely locally observable.
The key impact of this development lies in the
system ability, to reduce material residence time, to
flow information and material in a much-improved
manner with the appropriate control strategy.
Additional elements to be considered in the
evaluation of the performance of the observer are
distributed parameters effects due to the large
sampling intervals often encountered in mineral
applications.
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