---
title: "Define controller, plant, actuator"
subject: "Embedded System"
chapter: 7
key: "semester_6/embedded_system:define-controller-plant-actuator"
source: https://www.bctengineer.com/q/semester_6/embedded_system/define-controller-plant-actuator
site: BCT Engineering
---

# Define controller, plant, actuator

Embedded System · Chapter 7: Control System

- Asked in: 2070 Bhadra, 3 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/embedded_system/define-controller-plant-actuator
- Whole chapter: https://www.bctengineer.com/md/semester_6/embedded_system/chapter-7

## Question

Define the following terms used in control system: Controller, Plant, Actuator.

## Short answer

Controller: hardware/software computing control signal from error between set-point and measured output (e.g., microcontroller with PID). Plant: physical process (motor, oven) whose output is regulated. Actuator: converts controller signal into physical action (motor, valve, heater).

## Answer

- **Controller:** the part of the system (hardware or software, e.g. a microcontroller running a PID algorithm) that takes the error between the set-point and the measured output and computes the control signal.
- **Plant:** the physical process or system being controlled, such as the car, a motor, an oven or a tank, whose output (speed, temperature, level) is to be regulated.
- **Actuator:** the device that converts the controller's signal into a physical action on the plant, such as a motor, valve, heater or throttle servo.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does the controller do?
   A. Takes the error and computes the control signal
   B. Measures output
   C. Converts signal to force
   D. Is the physical process
   Answer: A. E.g. a microcontroller running PID. (Key point: Controller)

2. Which is a plant?
   A. The PID code
   B. The throttle servo
   C. The ADC
   D. The car, motor, oven or tank being controlled
   Answer: D. Process regulated. (Key point: Plant)

3. Which is an actuator?
   A. Oven
   B. PID algorithm
   C. Motor, valve, heater or throttle servo
   D. Temperature sensor
   Answer: C. Converts signal into action. (Key point: Actuator)

## Related in Embedded System

- [Steps to design closed loop control system](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aclosed-loop-design-steps) — Embedded System, chapter 7
- [GPP operation: datapath and controller](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Agpp-datapath-controller) — Embedded System, chapter 2, asked 4×
- [Why integral controller is needed](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aintegral-controller-need) — Embedded System, chapter 7
- [Control evaluation steps; PD and PI design](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Acontrol-evaluation-steps-pd-pi) — Embedded System, chapter 7
- [DMA controller and flow of actions](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Adma-controller-flow) — Embedded System, chapter 5, asked 3×
- [Open-loop automobile cruise controller design](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aopen-loop-cruise-controller) — Embedded System, chapter 7, asked 3×

## Related in other subjects

- [Control type for constant-speed actuator](https://www.bctengineer.com/question.md?key=semester_3%2Fcontrol_systems%3Aconstant-speed-actuator) — Control Systems, chapter 1
- [Digital PD controller design for plant 1/s²](https://www.bctengineer.com/question.md?key=semester_6%2Fdigital_control_system%3Apd-design-double-integrator) — Digital Control System, chapter 4, asked 2×
- [Terms used in a pitched roof](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aroof-terminology) — Building Technology, chapter 4, asked 4×
- [Pulse TF with PID controller, plant 1/(s+1)](https://www.bctengineer.com/question.md?key=semester_6%2Fdigital_control_system%3Apid-pulse-tf-first-order) — Digital Control System, chapter 3, asked 2×