---
title: "PID tuning and computer control issues"
subject: "Embedded System"
chapter: 7
key: "semester_6/embedded_system:pid-tuning-practical-issues"
source: https://www.bctengineer.com/q/semester_6/embedded_system/pid-tuning-practical-issues
site: BCT Engineering
---

# PID tuning and computer control issues

Embedded System · Chapter 7: Control System

- Asked in: 2069 Bhadra, 8 marks
- Video: [Manual and Automatic PID Tuning Methods | Understanding PID Control, Part 6](https://www.youtube.com/watch?v=qj8vTO1eIHo) — MATLAB
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/embedded_system/pid-tuning-practical-issues
- Whole chapter: https://www.bctengineer.com/md/semester_6/embedded_system/chapter-7

## Question

What is PID tuning? Discuss the practical issues related with computer based control.

## Short answer

PID tuning selects Kp, Ki, Kd for fast, stable response with low overshoot and zero steady-state error. Practical issues include sampling delay, quantization noise, sensor noise amplified by derivative, integral wind-up, actuator limits, numerical issues, real-time jitter, nonlinearities, and derivative kick from set-point steps.

## Answer

**PID tuning** is the process of choosing the gains Kp, Ki and Kd so that the closed-loop system meets its requirements: fast rise time, small overshoot, short settling time and zero steady-state error, while remaining stable. Methods include manual tuning, Ziegler-Nichols and software auto-tuning.

#### Practical issues in computer based control

1. **Sampling and delay:** the loop is sampled every T; a long T or computation delay reduces the phase margin and can cause instability. T should be much smaller than the plant time constant.
2. **Quantisation:** the ADC and DAC have finite resolution, which causes errors and can produce limit cycles; the derivative term (especially with a large Kd or a short sampling period) amplifies this quantisation noise.
3. **Sensor noise:** the derivative term amplifies noise, so filtering (low-pass or averaging) is required.
4. **Integral wind-up:** when the actuator saturates, the integral keeps growing; use clamping or anti-wind-up.
5. **Actuator limits:** the output has minimum and maximum values (PWM 0-100 %, throttle limits), and also slew-rate limits.
6. **Numerical issues:** fixed-point arithmetic, overflow and rounding on small microcontrollers.
7. **Real-time scheduling:** the control task must run at a fixed rate with low jitter; interrupts and RTOS priorities affect timing.
8. **Model changes and non-linearity:** gains tuned at one operating point may not work at another (e.g. different loads).
9. **Set-point changes:** a sudden set-point step gives a derivative kick; apply D to the measurement instead of the error.

## Check yourself

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

1. What is PID tuning?
   A. Choosing the sensor type
   B. Selecting the microcontroller
   C. Choosing Kp, Ki, Kd to meet response requirements while stable
   D. Removing the plant
   Answer: C. Tuning sets the gains. (Key point: PID tuning)

2. How is derivative noise handled?
   A. Increase Kd
   B. Filter the sensor signal
   C. Remove the integral
   D. Raise T
   Answer: B. D amplifies noise. (Key point: Derivative noise)

3. What happens in integral wind-up?
   A. Integral keeps growing while the actuator is saturated
   B. Derivative becomes zero
   C. Sampling stops
   D. ADC overflows
   Answer: A. Use clamping. (Key point: Wind-up)

4. How is derivative kick on set-point change avoided?
   A. Remove P
   B. Increase Ki
   C. Reduce T to zero
   D. Apply D to the measurement instead of the error
   Answer: D. A step in r would give a spike in de/dt. (Key point: Derivative kick)

## Related in Embedded System

- [Purpose of PID tuning; computer control benefits](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Apid-tuning-purpose-benefits) — Embedded System, chapter 7
- [Benefits of computer based control](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Acomputer-based-control-benefits) — Embedded System, chapter 7
- [PID control operation with block diagram](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Apid-operation-block-diagram) — Embedded System, chapter 7, asked 4×

## Related in other subjects

- [PID control of speed and torque](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Apid-control-speed-torque-motor) — Utilization of Electrical Energy, chapter 3, asked 2×