Sample time

Definition

Sample time refers to the discrete time intervals at which continuous signals are measured and converted into digital data. This concept is crucial for accurately modeling and simulating dynamic systems in tools like Simulink, where the choice of sample time can significantly affect the performance and accuracy of simulations. Properly selecting sample time ensures that system behaviors are captured effectively and allows for the correct analysis of system response over time.

5 Must Know Facts For Your Next Test

1. Sample time can be set to a fixed value or can vary depending on the requirements of the simulation model in Simulink.
2. Choosing an appropriate sample time is essential for achieving accurate results, as too long of a sample time can miss critical system dynamics while too short may lead to unnecessary computational load.
3. In Simulink, sample times can be specified individually for each block in a model, allowing for flexibility in mixed continuous and discrete systems.
4. The default sample time in Simulink may not always be optimal for every model, so users should consider adjusting it based on system characteristics and desired accuracy.
5. Simulation results can be significantly affected by the sample time, as it directly influences how well the system’s behavior is captured during analysis.

Review Questions

• How does selecting an appropriate sample time impact the accuracy of simulations in Simulink?
  • Selecting an appropriate sample time is critical because it directly influences the ability to accurately capture system dynamics. If the sample time is too long, key behaviors may be missed, leading to inaccurate results. Conversely, if the sample time is too short, it may increase computational load without providing significant benefits in accuracy. Thus, a balance must be achieved to optimize performance and accuracy.
• Discuss the implications of the sampling theorem on the choice of sample time when modeling systems in Simulink.
  • The sampling theorem highlights the importance of choosing a sample time that is sufficient to accurately represent the continuous signals being modeled. According to this theorem, to avoid aliasing and ensure that all relevant information is captured, the sample rate must exceed twice the highest frequency component present in the signal. This principle guides engineers to select appropriate sample times that allow for effective modeling of systems without losing vital information.
• Evaluate how varying sample times across different blocks in a Simulink model affects overall system performance and stability.
  • Varying sample times across different blocks can lead to complex interactions within a Simulink model that may affect overall system performance and stability. If some blocks operate at much shorter or longer sample times compared to others, it can create discrepancies in data processing and lead to unstable behaviors or inaccurate results. Therefore, careful consideration and testing are necessary when designing models with mixed sample times to ensure that all components work harmoniously together.

Related terms

Discrete-time signal: A signal that is defined only at discrete intervals of time, often resulting from the sampling of a continuous-time signal.

Sampling theorem: A principle stating that a continuous signal can be completely represented in its sampled version if it is sampled at a rate greater than twice its highest frequency component.

Time step: The increment of time between each sample in a simulation, which defines how frequently data is collected or updated.