1. Nature of industrial processes. Modeling

1.1 Notion of system

A system is an isolated device, subject to the laws of physics, chemistry, biology, economics, etc., characterized by certain quantities and placed in an environment. An industrial system is often referred to as a process. Characteristic quantities are variables and parameters, the latter being considered constant or slowly varying in relation to the former, which evolve over time. Process inputs characterize the effect of the environment on the system. Outputs characterize the effect of the system on the environment. Inputs are often raw products or energy. Inputs are of two types: actions and disturbances. Actions are controllable by the user; they serve as a control or regulating variable; disturbances are not controllable by the user, but can sometimes be measured....