Key Concepts
Stiction
Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact. [ 1 ] The term is a portmanteau of the term "static friction ", [ 2 ] perhaps also influenced by the verb " stick ". Any solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static cohesion. Stiction is a threshold , not a continuous force. In situations where two surfaces with areas below the micrometer range come into close proximity (as in an accelerometer ), they may adhere together.Deadband
A deadband (sometimes called a neutral zone ) is an area of a signal range or band where no action occurs (the system is dead ). Deadband is used in voltage regulators and other controllers. The purpose is common, to prevent oscillation or repeated activation-deactivation cycles (called 'hunting' in proportional control systems).
A proportional-integral-derivative controller ( PID controller ) is a generic control loop feedback mechanism ( controller ) widely used in industrial control systems .
PID controller
Control theory
The concept of the feedback loop to control the dynamic behavior of the system: this is negative feedback, because the sensed value is subtracted from the desired value to create the error signal, which is amplified by the controller. Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems with inputs.
In control theory , gain scheduling is an approach to control of non-linear systems that uses a family of linear controllers , each of which provides satisfactory control for a different operating point of the system. One or more observable variables, called the scheduling variables , are used to determine what operating region the system is currently in and to enable the appropriate linear controller. For example in an aircraft flight control system , the altitude and Mach number might be the scheduling variables, with different linear controller parameters available (and automatically plugged into the controller) for various combinations of these two variables. A relatively large scope state of the art about gain scheduling has been published in (Survey of Gain-Scheduling Analysis & Design, D.J.Leith, WE.Leithead). [ 1 ] <p style="text-align:right;color:#A8A8A8"></p>