Industrial Products for Advanced Control of Mineral Processing Plants - Advanced Control and Supervision of Mineral Processing Plants - page 302

data collected in December 1997 showed that control by SmartGrind rather than
operator supervision brought about an increase in throughput of 2% [55].

Figure 7.6 Block diagram of TotalPlant SmartGrind MPC

INVENSYS

Invensys offers a control system product known as Connoisseur that incorporates
two modules, one of them a model-based predictive controller and the other a static
optimizer that employs linear programming [56].
Key features of Connoisseur are the following:

• real time adaptive control, enabling the control system to be adapted to prevailing

process conditions on-line;

• constrained optimization that permits operation within the physical constraints

of the process, allowing the system to maximize process potential;

• application of MPC to processes that require multiple models. The product uses

on-line gain scheduling and can switch automatically between multiple model
sets without turning the controller off.

Connoisseur's modeling tools are cross-correlation, power spectral density and
statistical techniques such as OLS and PLS. Recursive least squares is also used
for on-line adaptable estimation and control with FIR and ARX models. The prod-
uct enables management of hard and soft constraints including variation limits and
speeds. Additionally, it offers gain scheduling functions for processes that require
multimodels, neural networks (multilayer perceptron and radial basis function) for
non-linear systems, and fuzzy ES to complement the MPC control.
Among other mining applications, Connoisseur has been used at Asarco Mines
to improve grinding and flotation circuit performance [57]. Grinding control objec-
tives include driving the line to its optimal operating point and maintaining control
through variations in ore characteristics. The product has increased the feed rate
without violating the mill's operating limits, such as maximum particle size, cy-
clone overflow density and cyclone pump current. It also has the ability to increase
recycle mass flow for minimizing particle sizes when the feed is limited. The re-
sult has been the dual benefit of increasing recovery while minimizing wear on the
ball mills. A separate Connoisseur multivariable controller is used to control each
of the eight grinding circuits. Each controller has access to a number of process