Motor startup and braking simulation in Simulink - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the motor speed to start from zero.

Simulink

motor_speed = [1]

Drag options to blanks, or click blank then click option'

A1

B100

C0

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the initial speed to a non-zero value.

Using a negative speed at startup.

The motor speed should start at zero to simulate startup from rest.

2fill in blank

medium

Complete the code to apply braking torque to the motor.

Simulink

braking_torque = [1]

Drag options to blanks, or click blank then click option'

A100

B-10

C10

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using positive torque for braking.

Setting braking torque to zero.

Braking torque is applied as a negative value to slow down the motor.

3fill in blank

hard

Fix the error in the code to correctly calculate motor acceleration.

Simulink

acceleration = (torque [1] load_torque) / inertia

Drag options to blanks, or click blank then click option'

A-

B*

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Adding torques instead of subtracting.

Multiplying torques incorrectly.

Acceleration is proportional to the net torque, which is motor torque minus load torque.

4fill in blank

hard

Fill both blanks to create a dictionary of motor states with speed and torque.

Simulink

motor_states = {'speed': [1], 'torque': [2]

Drag options to blanks, or click blank then click option'

Amotor_speed

Bbraking_torque

Cacceleration

Dload_torque

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing acceleration with speed.

Using load torque instead of braking torque.

The dictionary should map 'speed' to motor_speed and 'torque' to braking_torque to represent current motor states.

5fill in blank

hard

Fill all three blanks to compute the motor speed after braking over a time step.

Simulink

motor_speed = motor_speed [1] acceleration [2] time_step [3] braking_effect

Drag options to blanks, or click blank then click option'

A+

B*

C-

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using division instead of multiplication for time step.

Adding braking effect instead of subtracting.

Motor speed updates by adding acceleration times time step, then subtracting braking effect.

Practice

1. What is the main purpose of using a Step input block in a motor startup simulation in Simulink?

easy

A. To apply braking force to the motor

B. To simulate the motor turning on at a specific time

C. To measure the motor speed

D. To display the motor speed graphically

Solution

1. Step 1: Understand the role of Step input block

   The Step input block provides a sudden change in input value at a specified time, simulating an event like turning the motor on.

2. Step 2: Relate Step input to motor startup

   In motor startup simulation, the Step input triggers the motor to start running at a chosen time.

3. Final Answer:

   To simulate the motor turning on at a specific time -> Option B

4. Quick Check:

   Step input = motor start trigger [OK]

Hint: Step input means sudden start signal for motor [OK]

Common Mistakes:

• Confusing Step input with braking action
• Thinking Step input measures speed
• Assuming Step input displays graphs

2. Which of the following is the correct way to connect a Brake block in Simulink to simulate motor braking?

easy

A. Connect Brake block input to motor speed output

B. Connect Brake block input to motor torque output

C. Connect Brake block output to motor speed input

D. Connect Brake block output to motor torque input

Solution

1. Step 1: Identify Brake block connections

   The Brake block takes motor speed as input to apply braking force based on speed.

2. Step 2: Match correct input-output connection

   Motor speed output should connect to Brake block input to simulate braking effect properly.

3. Final Answer:

   Connect Brake block input to motor speed output -> Option A

4. Quick Check:

   Brake input = motor speed output [OK]

Hint: Brake block input must receive motor speed [OK]

Common Mistakes:

• Connecting Brake output to motor speed input
• Using motor torque instead of speed as input
• Reversing input and output connections

3. Given this Simulink setup: a Step input turns the motor on at 1 second, and a Brake block applies braking at 5 seconds. What will the Scope block show for motor speed over 10 seconds?

medium

A. Speed rises at 1s, stays constant, then drops after 5s

B. Speed stays zero until 5s, then rises sharply

C. Speed rises at 1s and remains constant without change

D. Speed drops immediately at 1s and stays low

Solution

1. Step 1: Analyze Step input effect at 1 second

   The Step input causes motor speed to increase starting at 1 second, simulating startup.

2. Step 2: Analyze Brake block effect at 5 seconds

   At 5 seconds, the Brake block applies braking, causing speed to decrease after that time.

3. Final Answer:

   Speed rises at 1s, stays constant, then drops after 5s -> Option A

4. Quick Check:

   Step start then brake drop = Speed rises at 1s, stays constant, then drops after 5s [OK]

Hint: Motor speed rises at start, drops when brake applied [OK]

Common Mistakes:

• Thinking speed rises after brake time
• Assuming speed never changes after start
• Confusing timing of speed changes

4. You run a motor startup and braking simulation but the Scope shows motor speed never decreases after braking is applied. What is the most likely error?

medium

A. Step input time is set after braking time

B. Motor speed is set to zero initially

C. Scope block is not connected to motor speed

D. Brake block input is not connected to motor speed output

Solution

1. Step 1: Identify why braking has no effect

   If motor speed does not decrease after braking, the Brake block likely does not receive correct speed input.

2. Step 2: Check Brake block connections

   Brake block input must be connected to motor speed output to apply braking properly.

3. Final Answer:

   Brake block input is not connected to motor speed output -> Option D

4. Quick Check:

   Brake input missing = no speed drop [OK]

Hint: Check Brake input connection if speed doesn't drop [OK]

Common Mistakes:

• Ignoring Brake block wiring
• Mixing Step input and Brake timing
• Assuming Scope connection causes braking issue

5. You want to simulate a motor startup that ramps speed gradually over 3 seconds, then apply braking that stops the motor smoothly over 2 seconds. Which Simulink blocks and settings should you use?

hard

A. Use a Pulse Generator for startup and no Brake block

B. Use a Step block for startup and a Brake block with constant force

C. Use a Ramp block for startup and a Brake block with a time-based brake force

D. Use a Constant block for startup and a Step block for braking

Solution

1. Step 1: Choose startup block for gradual speed increase

   A Ramp block increases motor speed smoothly over a set time, perfect for gradual startup over 3 seconds.

2. Step 2: Choose braking method for smooth stop

   A Brake block with time-based brake force can apply braking gradually over 2 seconds to stop smoothly.

3. Final Answer:

   Use a Ramp block for startup and a Brake block with a time-based brake force -> Option C

4. Quick Check:

   Ramp for smooth start + timed brake = Use a Ramp block for startup and a Brake block with a time-based brake force [OK]

Hint: Ramp for smooth start, Brake with timed force for smooth stop [OK]

Common Mistakes:

• Using Step block for gradual startup
• Applying constant brake force for smooth stop
• Omitting Brake block for stopping