Speed control with PID in Simulink - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the role of the integral term in PID control

In a PID controller used for speed control, what is the primary role of the integral term?

A It eliminates steady-state error by accumulating past errors over time.

B It reduces the noise in the speed measurement signal.

C It directly controls the speed setpoint without considering error.

D It predicts future errors based on the current rate of change.

💡 Hint

Think about how the controller deals with errors that persist over time.

The integral term sums past errors to remove any steady-state offset, ensuring the speed reaches the desired setpoint.

❓ Predict Output

intermediate

Simulink PID block output behavior

Given a Simulink PID Controller block configured with P=2, I=1, D=0, and a step input error signal of 1 starting at time 0, what is the output of the PID block at time t=1 second assuming zero initial conditions?

Simulink

P = 2
I = 1
D = 0
error = 1  # constant from t=0 to t=1
output = P*error + I*integral(error) + D*derivative(error)

A 2

B 3

C 1

D 0

💡 Hint

Calculate each term separately: proportional, integral, and derivative.

Proportional term = 2 * 1 = 2
Integral term = 1 * (1 second * 1 error) = 1
Derivative term = 0
Total output = 2 + 1 + 0 = 3

❓ data_output

advanced

Analyzing PID tuning effect on speed response

You run a Simulink simulation of a motor speed controlled by a PID controller. You try two different tuning sets:

• Set 1: P=5, I=0.5, D=0
• Set 2: P=5, I=0.5, D=1

Which of the following best describes the expected difference in the speed response plots?

A Set 2 will have less overshoot and faster settling time than Set 1.

B Set 1 will have less overshoot and faster settling time than Set 2.

C Both sets will have identical speed responses.

D Set 2 will have more steady-state error than Set 1.

💡 Hint

Consider the effect of the derivative term on system damping.

The derivative term adds damping, reducing overshoot and improving settling time without affecting steady-state error.

🔧 Debug

advanced

Identifying error in Simulink PID speed control model

A Simulink model uses a PID Controller block to control motor speed. The motor speed never reaches the setpoint and stays below it. Which of the following is the most likely cause?

A The derivative gain is too large, causing slow response.

B The proportional gain is too high, causing oscillations.

C The setpoint signal is not connected to the PID block.

D The integral gain is set to zero, causing steady-state error.

💡 Hint

Think about what causes steady-state error in PID control.

Without integral action, the controller cannot eliminate steady-state error, so the speed stays below the setpoint.

🚀 Application

expert

Designing a PID controller for a speed control system with noise

You are designing a PID controller in Simulink for a motor speed system. The speed sensor signal has high-frequency noise. Which PID tuning approach is best to minimize noise impact while maintaining good speed control?

A Set proportional gain to zero and rely only on integral and derivative terms.

B Increase integral gain to quickly correct errors caused by noise.

C Use low derivative gain and add a low-pass filter on the derivative term output.

D Remove the integral term to avoid accumulation of noise.

💡 Hint

Consider how derivative action reacts to noise and how filtering helps.

Derivative action amplifies noise; using low derivative gain and filtering reduces noise impact while keeping control performance.