Deadband
Deadband is the error range in which the controller gives no response at all: if the measured value deviates from the reference within this range, the output is not changed. In speed control, a deadband a few rpm wide prevents sensor noise and mechanical play from constantly moving the actuator.
Deadband is deliberate insensitivity. Its purpose is to prevent responses to small errors that are not real. If it is chosen too narrow, the actuator jitters constantly, the cable and joint wear out for nothing, and current consumption rises. If it is chosen too wide, control becomes lazy: when the load changes, a noticeable deviation builds up before the system notices the error.
- The typical approach is to keep the deadband slightly above the amplitude of the measurement noise.
- Trying to cover mechanical play (cable stretch, joint clearance) with deadband is wrong; play must be eliminated mechanically.
In the field this translates as follows: if nothing happens when you move the potentiometer by a very small amount, this is usually not a fault but the deadband in the design. The same concept also appears at the centre of a joystick; there the purpose is to prevent motion from starting when the lever trembles at centre.
Context in which this term is used: Electronic speed and throttle control on a diesel engine