---
title: "Why integral controller is needed"
subject: "Embedded System"
chapter: 7
key: "semester_6/embedded_system:integral-controller-need"
source: https://www.bctengineer.com/q/semester_6/embedded_system/integral-controller-need
site: BCT Engineering
---

# Why integral controller is needed

Embedded System · Chapter 7: Control System

- Asked in: 2079 Asoj, 2 marks
- Video: [PID Control - A brief introduction](https://www.youtube.com/watch?v=UR0hOmjaHp0) — Brian Douglas
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/embedded_system/integral-controller-need
- Whole chapter: https://www.bctengineer.com/md/semester_6/embedded_system/chapter-7

## Question

Why is an Integral controller needed in a control system?

## Short answer

Integral control eliminates steady-state error by accumulating error over time, driving output until error becomes zero. Unlike proportional-only control which needs non-zero error for non-zero output, the integrator holds the exact output to cancel constant disturbances. Drawbacks include slower response, potential overshoot, and need for anti-windup during actuator saturation.

## Answer

An integral controller is needed to remove the steady-state error. A P-only controller needs a non-zero error to produce a non-zero output, so a constant disturbance (for example a hill in cruise control) leaves a permanent offset between set-point and output.

The integral term accumulates the error over time, so the control output keeps changing until the error becomes exactly zero. At steady state the integrator holds the exact output needed to cancel the disturbance, so the output equals the set-point. The price is slower response and possible overshoot, and the integral must be limited (anti-wind-up) when the actuator saturates.

## Check yourself

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

1. Why is an integral controller needed?
   A. To reduce sensor noise
   B. To remove steady-state error
   C. To speed up the response
   D. To reduce the number of gains
   Answer: B. It drives the error to exactly zero. (Key point: Purpose)

2. Why does a P-only controller leave an offset under constant disturbance?
   A. It needs non-zero error to produce non-zero output
   B. Its gain is always zero
   C. It integrates the error
   D. It has no feedback
   Answer: A. A permanent error is required to hold the output cancelling the disturbance. (Key point: P-only offset)

3. Which is a drawback of the integral term?
   A. Amplified sensor noise only
   B. Permanent steady-state error
   C. Loss of feedback
   D. Slower response, possible overshoot and wind-up
   Answer: D. The price is slower response and overshoot; limit it for saturation. (Key point: Price)

## 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
- [Define controller, plant, actuator](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Adefine-controller-plant-actuator) — 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×
- [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×
- [Control unit sub-operations of GPP](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Acontrol-unit-sub-operations) — Embedded System, chapter 2, asked 4×

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- [AC voltage controller on-off cycle control numerical](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Aintegral-cycle-control-numerical) — Power Electronics, chapter 6
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