Motor startup and braking simulation in Simulink - Step-by-Step Execution

Concept Flow - Motor startup and braking simulation

Start Simulation

↓

Apply Voltage to Motor

↓

Motor Accelerates

↓

Check Speed Threshold

↓

Apply Braking

↓

Motor Decelerates

↓

Motor Stops

↓

End Simulation

The simulation starts by applying voltage to the motor, causing it to accelerate. When a speed threshold is reached, braking is applied to decelerate the motor until it stops, ending the simulation.

Execution Sample

Simulink

1. Apply voltage input to motor block
2. Motor speed increases over time
3. When speed > threshold, apply braking torque
4. Motor speed decreases until zero
5. Stop simulation

This code simulates motor startup by increasing speed, then braking to stop the motor.

Execution Table

Step	Motor Speed (rpm)	Voltage Applied (V)	Braking Torque (Nm)	Condition	Action
1	0	24	0	Speed < Threshold (1000 rpm)	Apply voltage, motor accelerates
2	400	24	0	Speed < Threshold	Continue acceleration
3	800	24	0	Speed < Threshold	Continue acceleration
4	1000	24	0	Speed = Threshold	Prepare to brake next step
5	1000	0	5	Speed >= Threshold	Apply braking torque, voltage off
6	700	0	5	Speed > 0	Motor decelerates
7	300	0	5	Speed > 0	Motor decelerates
8	0	0	0	Speed = 0	Motor stopped, end simulation

💡 Motor speed reaches zero, simulation ends

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7	Final
Motor Speed (rpm)	0	400	800	1000	1000	700	300	0	0
Voltage Applied (V)	24	24	24	24	0	0	0	0	0
Braking Torque (Nm)	0	0	0	0	5	5	5	0	0

Key Moments - 3 Insights

Why does the voltage drop to zero when braking starts?

Voltage is turned off at step 5 to stop accelerating the motor, allowing braking torque to slow it down, as shown in execution_table row 5.

Why is braking torque zero at the start and end?

Braking torque is zero initially because the motor is accelerating, and zero at the end because the motor has stopped, as seen in execution_table rows 1 and 8.

How do we know when to switch from acceleration to braking?

The condition 'Speed >= Threshold' at step 5 triggers braking, shown in execution_table row 4 and 5.

Visual Quiz - 3 Questions

Look at the execution table, what is the motor speed at step 3?

A 800 rpm

B 1000 rpm

C 400 rpm

D 0 rpm

💡 Hint

Check the 'Motor Speed (rpm)' column at step 3 in the execution_table.

At which step does the voltage applied drop to zero?

A Step 4

B Step 5

C Step 6

D Step 7

💡 Hint

Look at the 'Voltage Applied (V)' column in the execution_table to find when it changes from 24 to 0.

If braking torque was applied earlier at step 3, what would happen to motor speed at step 4?

A Motor speed would be higher than 1000 rpm

B Motor speed would stay at 1000 rpm

C Motor speed would be about 800 rpm or less

D Motor speed would instantly drop to zero

💡 Hint

Refer to the variable_tracker showing how braking torque slows motor speed over steps.

Concept Snapshot

Motor startup and braking simulation:
- Apply voltage to accelerate motor
- Monitor speed until threshold reached
- Turn off voltage and apply braking torque
- Motor decelerates until stop
- Simulation ends when speed is zero

Full Transcript

This simulation models a motor starting up by applying voltage, causing it to speed up. When the motor reaches a set speed threshold, the voltage is turned off and braking torque is applied to slow it down. The motor speed decreases step by step until it stops, ending the simulation. The execution table shows each step's motor speed, voltage, braking torque, and actions taken. Variables change over time, with speed increasing during acceleration and decreasing during braking. Key moments clarify why voltage drops when braking starts and how braking torque affects speed. The visual quiz tests understanding of these steps and variable changes.

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