Disturbance
High school
Consider a system that is trying to follow a course, like a drone flying to a target. A disturbance is an outside influence that pushes the system off course.
Undergraduate (control systems)
Consider a control system $\dot{x} = f(x, u, d)$, with inputs from outside. A disturbance is an unwanted exogenous input, such as $d$, that affects the dynamics of the system. It changes the actual state of the system.
Examples
Examples
- A gust of wind hitting a quadcopter drone High school
Non-examples
Things that may be mistaken for examples.
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Jitter in a quadcopter drone’s GPS position readings
High school
The GPS jitter is not a disturbance because it does not directly change the state of the drone (its position or velocity).
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The motor commands of a quadcopter drone
High school
The motor commands of a quadcopter drone are not a disturbance, because they are chosen, not imposed.
Distinctions involving this term
- Types of exogenous inputs: A control system is affected by signals that it does not generate itself, and these signals have different names depending on their role. Exogenous inputs are any inputs from outside the system. A control input is chosen; a disturbance acts on the dynamics; measurement noise only corrupts what is measured. A perturbation is a change to the system itself, which may or may not be modeled as an input.