---
title: "Steps to design closed loop control system"
subject: "Embedded System"
chapter: 7
key: "semester_6/embedded_system:closed-loop-design-steps"
source: https://www.bctengineer.com/q/semester_6/embedded_system/closed-loop-design-steps
site: BCT Engineering
---

# Steps to design closed loop control system

Embedded System · Chapter 7: Control System

- Asked in: 2072 Asoj, 5 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/embedded_system/closed-loop-design-steps
- Whole chapter: https://www.bctengineer.com/md/semester_6/embedded_system/chapter-7

## Question

With a neat diagram write the steps for designing a closed loop control system.

## Short answer

Design steps: 1) Define specifications (error, overshoot, timing). 2) Select sensor/actuator. 3) Model plant (e.g., m·dv/dt=-b·v+u+d). 4) Choose controller structure (P/PI/PD/PID). 5) Set sampling period T ≪ plant time constant. 6) Determine gains via stability analysis or tuning. 7) Simulate and verify. 8) Implement, test, and retune on hardware.

## Answer

Designing a closed-loop controller means choosing a controller and its parameters so that the measured output follows the reference with the required accuracy, speed and stability.

#### Block diagram

```text
 r -->(+)-e->[Controller]-u->[Actuator]->[Plant]--+--> y
       ^ -                          d --^           |
       |                                            |
       +----------------[Sensor]<-------------------+
```

#### Design steps

1. **State the objective and specifications:** the controlled variable, set-point range, allowed steady-state error, overshoot, rise and settling time.
2. **Choose sensor and actuator:** select a sensor to measure the output and an actuator to drive the plant; check range, resolution and speed.
3. **Model the plant:** write the differential (or difference) equation from physics or from a step-response test, e.g. m·dv/dt = -b·v + u + d.
4. **Choose the controller structure:** P, PI, PD or PID, depending on needed error, speed and damping.
5. **Choose the sampling period** (for a digital controller), much shorter than the plant's time constant.
6. **Find the gains** from the stability conditions (no unbounded output, no oscillation) using analysis or tuning rules.
7. **Simulate** the closed loop and check the specifications and disturbance rejection.
8. **Implement** in software (ISR at period T) or hardware, **test on the real plant**, and re-tune.

## Check yourself

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

1. What is the first step in designing a closed-loop controller?
   A. Implement on hardware
   B. Tune gains on the real plant
   C. State objectives and specifications
   D. Choose the sampling period
   Answer: C. Specs such as error, overshoot and settling time guide all later steps. (Key point: First step)

2. Why is the plant modelled?
   A. To avoid using a sensor
   B. To write its equation so gains can be found and simulated
   C. To eliminate the actuator
   D. To make the system open loop
   Answer: B. Model enables stability analysis and simulation. (Key point: Modelling)

3. How is the sampling period chosen for a digital controller?
   A. Much shorter than the plant's time constant
   B. Longer than the time constant
   C. Equal to the settling time
   D. Irrelevant
   Answer: A. A long T may cause instability. (Key point: Sampling period)

4. What follows simulation?
   A. Stop, as simulation is final
   B. Remove the sensor
   C. Redesign the plant
   D. Implement, test on the real plant and re-tune
   Answer: D. Real plants differ from models. (Key point: Final steps)

## Related in Embedded System

- [Closed loop speed control design conditions](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aclosed-loop-speed-control-conditions) — Embedded System, chapter 7
- [Closed loop diagram; P, PI, PD, PID](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aclosed-loop-block-diagram-pid-types) — Embedded System, chapter 7
- [Open loop versus closed loop control](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aopen-vs-closed-loop) — Embedded System, chapter 7, asked 6×
- [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
- [Closed loop better than open loop (cruise)](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aclosed-loop-better-cruise-integral) — Embedded System, chapter 7
- [Open-loop cruise control using P control](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aopen-loop-cruise-p-control) — Embedded System, chapter 7

## Related in other subjects

- [Closed loop control system block diagram explained](https://www.bctengineer.com/question.md?key=semester_3%2Fcontrol_systems%3Awhat-is-cs-bd-closed-loop) — Control Systems, chapter 1, asked 4×
- [Control system block diagram and closed loop advantages](https://www.bctengineer.com/question.md?key=semester_3%2Fcontrol_systems%3Awhat-is-cs-bd-cl-advantages) — Control Systems, chapter 1
- [Define control system and closed loop block roles](https://www.bctengineer.com/question.md?key=semester_3%2Fcontrol_systems%3Adefine-cs-bd-role) — Control Systems, chapter 1, asked 5×
- [Control system importance and closed loop components](https://www.bctengineer.com/question.md?key=semester_3%2Fcontrol_systems%3Adefine-cs-importance-components) — Control Systems, chapter 1