Exogenous input
High school
Consider a system that changes over time. An exogenous input is any signal that comes into the system from outside it, such as a control input or a disturbance.
Undergraduate (control systems)
Consider a control system. An exogenous input is any signal that enters the system from outside, rather than being determined by the system’s own state. This includes control inputs, reference signals, disturbances, and noise.
Examples
Examples
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A gust of wind hitting a quadcopter drone
High school
The gust is a disturbance, and so an exogenous input, because it changes the drone’s actual motion and is not chosen.
- Jitter in a quadcopter drone’s GPS position readings High school
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The motor commands of a quadcopter drone
High school
The motor commands are a control input, and so an exogenous input to the motors, because the flight controller chooses them.
Non-examples
Things that may be mistaken for examples.
Notes
In robust control (for example, in $H_{\infty}$ problems), “exogenous input” often means only the inputs that the controller does not choose, such as references, disturbances, and noise, as opposed to the control input $u$.
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.