Zero-order hold in Simulink - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a zero-order hold block in Simulink.

Simulink

zoh_block = add_block('simulink/Discrete/Zero-Order Hold', '[1]');

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

A'myModel/ZeroOrderHold'

B'simulink/Continuous/Integrator'

C'myModel/Scope'

D'simulink/Sources/Sine Wave'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a block path from a different library.

Not specifying the model name in the block path.

The zero-order hold block is added to the model with a unique path name.

2fill in blank

medium

Complete the code to set the sample time of the zero-order hold block to 0.1 seconds.

Simulink

set_param('[1]', 'SampleTime', '0.1');

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

A'myModel/Sine Wave'

B'myModel/Integrator'

C'myModel/ZeroOrderHold'

D'myModel/Scope'

Attempts:

3 left

💡 Hint

Common Mistakes

Setting sample time on the wrong block.

Using incorrect block path syntax.

The sample time parameter of the zero-order hold block is set to 0.1 seconds.

3fill in blank

hard

Fix the error in the code to connect the zero-order hold block output to a scope block input.

Simulink

add_line('myModel', '[1]', 'myModel/Scope/1');

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

A'myModel/Scope/1'

B'myModel/ZeroOrderHold/1'

C'myModel/Sine Wave/1'

D'myModel/Integrator/1'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the scope block as the source port.

Incorrect port number or block path.

The output port of the zero-order hold block is connected to the input port of the scope block.

4fill in blank

hard

Fill both blanks to create a zero-order hold block and set its sample time to 0.05 seconds.

Simulink

add_block('[1]', '[2]');
set_param('[2]', 'SampleTime', '0.05');

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

A'simulink/Discrete/Zero-Order Hold'

B'myModel/Scope'

C'myModel/ZeroOrderHold'

D'simulink/Sources/Step'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing block library path and model path.

Setting sample time on the wrong block.

The zero-order hold block is added and its sample time is set correctly.

5fill in blank

hard

Fill all three blanks to add a zero-order hold block, set its sample time to 0.2, and connect it to a scope block.

Simulink

add_block('[1]', '[2]');
set_param('[2]', 'SampleTime', '0.2');
add_line('myModel', '[3]', 'myModel/Scope/1');

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

A'simulink/Discrete/Zero-Order Hold'

B'myModel/ZeroOrderHold'

C'myModel/ZeroOrderHold/1'

D'myModel/Sine Wave/1'

Attempts:

3 left

💡 Hint

Common Mistakes

Incorrect block paths.

Wrong port used for connection.

The zero-order hold block is added, configured, and connected to the scope correctly.

Practice

1.

What is the main function of a Zero-order hold block in Simulink?

easy

A. It converts continuous signals to discrete signals.

B. It differentiates the input signal continuously.

C. It integrates the input signal over time.

D. It holds the input value constant between sample times.

Solution

1. Step 1: Understand the role of Zero-order hold and compare options

   The Zero-order hold block keeps the input value constant during the sample period. It does not differentiate, integrate, or convert continuous to discrete signals.

2. Final Answer:

   It holds the input value constant between sample times. -> Option D

3. Quick Check:

   Zero-order hold = hold input constant [OK]

Hint: Remember: zero-order hold means 'hold value constant' [OK]

Common Mistakes:

• Confusing zero-order hold with differentiation or integration
• Thinking it converts continuous to discrete signals
• Assuming it changes the signal value continuously

2.

Which of the following is the correct way to set the fixed sample time parameter in a Zero-order hold block in Simulink?

easy

A. Set sample time to a positive number like 0.1 seconds.

B. Set sample time to -1 for inherited sample time.

C. Set sample time to 0 for continuous operation.

D. Set sample time to a negative number other than -1.

Solution

1. Step 1: Understand sample time settings and evaluate options

   Fixed sample time must be a positive number (e.g., 0.1s) to specify hold duration. -1 inherits from input; 0 means continuous (no hold); other negatives invalid.

2. Final Answer:

   Set sample time to a positive number like 0.1 seconds. -> Option A

3. Quick Check:

   Sample time positive number = correct setting [OK]

Hint: Sample time must be positive for zero-order hold [OK]

Common Mistakes:

• Using zero or negative sample times incorrectly
• Confusing inherited sample time (-1) with explicit sample time
• Setting sample time to continuous (0) for discrete hold

3.

Consider this Simulink model snippet using a Zero-order hold block with sample time 0.5 seconds. The input signal is a step that changes from 0 to 1 at time 0.3 seconds. What will be the output of the Zero-order hold block at time 0.7 seconds?

medium

A. 0.5

B. 0

C. 1

D. Undefined

Solution

1. Step 1: Analyze sample intervals and input timing

   With sample time 0.5s, samples at 0, 0.5, 1.0s. Step changes at 0.3s, so input(0)=0, input(0.5)=1. At 0.7s (in [0.5,1.0)), holds 1.

2. Final Answer:

   1 -> Option C

3. Quick Check:

   Output holds last sampled input = 1 [OK]

Hint: Output holds input at last sample time before current time [OK]

Common Mistakes:

• Thinking sample at 0.5s captures 0 despite change at 0.3s
• Ignoring sample time intervals
• Confusing step change time with sample time

4.

In a Simulink model, a Zero-order hold block is set with sample time 0.2 seconds. The output signal is not holding values as expected and changes continuously. What is the most likely cause?

medium

A. Sample time is set to 0 (continuous) instead of 0.2.

B. Input signal is discrete, so hold is unnecessary.

C. Zero-order hold block is connected incorrectly.

D. Sample time is set to a negative number other than -1.

Solution

1. Step 1: Identify cause of continuous output behavior

   If sample time=0, block operates continuously (follows input without holding). Other causes less likely to produce continuous change.

2. Final Answer:

   Sample time is set to 0 (continuous) instead of 0.2. -> Option A

3. Quick Check:

   Continuous sample time = no hold [OK]

Hint: Check sample time is positive, not zero [OK]

Common Mistakes:

• Ignoring sample time setting
• Assuming input signal type causes issue
• Misconnecting blocks without checking parameters

5.

You want to convert a discrete sensor signal sampled every 0.1 seconds into a continuous signal for further processing in Simulink. Which approach using a Zero-order hold block is correct?

Choose the best option.

hard

A. Do not use Zero-order hold; use a continuous integrator instead.

B. Set the Zero-order hold sample time to 0.1 seconds to hold each sample value constant until the next sample.

C. Set the Zero-order hold sample time to -1 to inherit sample time from input.

D. Set the Zero-order hold sample time to 0 to make the output continuous.

Solution

1. Step 1: Understand goal and evaluate ZOH configurations

   Goal: hold discrete samples constant between 0.1s intervals for continuous output. Set Ts=0.1s matches sensor rate. Ts=0 continuous (no hold); -1 inherits (risk mismatch); integrator changes values.

2. Final Answer:

   Set the Zero-order hold sample time to 0.1 seconds to hold each sample value constant until the next sample. -> Option B

3. Quick Check:

   Sample time = sensor rate for correct hold [OK]

Hint: Match hold sample time to sensor sample interval [OK]

Common Mistakes:

• Setting sample time to zero for hold
• Using inherited sample time without checking input
• Replacing hold with integrator incorrectly