Modern tendencies in the development of control systems

2 Main terms and definitions

Automation

The control of a process by automatic means.

Closed-loop feedback control system

A system that uses a measurement of the output and compares it with the desired output.

Complexity of design

The intricate pattern of interwoven parts and knowledge required.

Control system

An interconnection of components forming a system configuration that will provide a desired

response.

Design

The process of conceiving or inventing the forms, parts, and details of a system to achieve a specified purpose.

Design gap A gap between the complex physical system and the design model intrinsic to the progression from the initial concept to the final product.

Engineering design

The process of designing a technical system.

Feedback signal

A measure of the output of the system used for feedback to control the system.

Flyball governor

A mechanical device for controlling the speed of a steam engine.

Multivariable control system

A system with more than one input variable or more than one output variable.

Negative feedback

The output signal is fed back so that it subtracts from the input signal.

Open-loop control system

A system that utilizes a device to control the process without using feedback. Thus

the output has no effect upon the signal to the process.

Optimization

The adjustment of the parameters to achieve the most favorable or advantageous design.

Plant

See Process.

Positive feedback

The output signal is fed back so that it adds to the input signal.

Process

The device, plant, or system under control.

Productivity

The ratio of physical output to physical input of an industrial process.

Risk

Uncertainties embodied in the unintended consequences of a design.

Robot

Programmable computers integrated with a manipulator. A reprogrammable, multifunctional manipulator used for a variety of tasks.

Specifications

Statements that explicitly state what the device or product is to be and to do. A set of prescribed

performance criteria.

Synthesis

The process by which new physical configurations are created. The combining of separate elements

or devices to form a coherent whole.

System

An interconnection of elements and devices for a desired purpose.

Trade-off

The result of making a judgment about how much compromise must be made between conflicting

criteria.

3 Fundamental control principles

Engineering is concerned with understanding and controlling the materials and forces of nature for the benefit of humankind. Control system engineers are concerned with understanding and controlling segments of their environment, often called systems, to provide useful economic products for society. The twin goals of understanding and controlling are complementary because effective systems control requires that the systems be understood and modeled. Furthermore, control engineering must often consider the control of poorly understood systems such as

chemical process systems. The present challenge to control engineers is the modeling and control of modern, complex, interrelated systems such as traffic control systems (for instance, O’Hare airport in Chicago, USA, which provides for more than 2000 flights a day!, about 900 000 flights a year!), chemical processes, and robotic systems. Simultaneously, the fortunate engineer has the opportunity to control many useful and interesting industrial automation systems. Perhaps the most characteristic quality of control engineering is the opportunity to control machines and industrial and economic processes for the benefit of society.

Control engineering is based on the foundations of feedback theory and linear system analysis, and it integrates the concepts of network theory and communication theory. Therefore control engineering is not limited to any engineering discipline but is equally applicable to aeronautical, chemical, mechanical, environmental, civil, and electrical engineering. For example, a control system often includes electrical, mechanical, and chemical components. Furthermore, as the understanding of the dynamics of business, social, and political systems increases, the ability to control these systems will also increase.