Cyber Physical Systems Lecture 5

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What denotes a default transition in a state machine?

Dashed lines (correct)

Solid lines

Dotted lines

Colored lines

Which statement best defines a deterministic state machine?

It can get stuck in a specific state.

At most one transition is enabled by each input value. (correct)

At least one transition is enabled by each input value.

More than one transition can be enabled by the same input value.

What is the main characteristic of a receptive state machine?

It only reacts to specific unique inputs.

It can become inoperative based on certain inputs.

At least one transition is possible for each input symbol. (correct)

There is no transition possible on every input symbol.

Why are extended state machines used?

To manage variable states when the number of states becomes large. Signup and view all the answers

In the traffic light example, how long does the light stay green before transitioning to yellow?

60 seconds Signup and view all the answers

What is the role of the 'count' variable in the extended state machine of the traffic light?

It counts the time in seconds for state transitions. Signup and view all the answers

When does the traffic light transition to the yellow state?

If it has been green for at least 60 seconds. Signup and view all the answers

What ensures that all state machines in the graphical notation are receptive?

Implicit default transitions are utilized. Signup and view all the answers

What is a key characteristic of a default transition in a state machine?

It is activated only when no non-default transitions are enabled. Signup and view all the answers

Which statement accurately describes determinacy in state machines?

For each state, there is at most one transition enabled for each input value. Signup and view all the answers

What is meant by receptiveness in the context of state machines?

The assurance that at least one transition is possible for each state on any input symbol. Signup and view all the answers

Why might one use an extended state machine instead of a simple FSM?

To accommodate additional variables alongside state transitions. Signup and view all the answers

In the provided traffic light example, what condition must be met for the light to transition from green to yellow?

The light must have been green for at least 60 seconds. Signup and view all the answers

How does the default transition impact the behavior of a state machine?

It provides a safety net for transitions when no other options are available. Signup and view all the answers

What role does the 'count' variable play in the extended state machine for the traffic light?

It counts the elapsed seconds in the green state to facilitate transitions. Signup and view all the answers

What defines a possible transition in a state machine?

It must satisfy the guard condition and be enabled by the current state. Signup and view all the answers

Study Notes

Cyber Physical Systems (CPS)

CPS is a system combining computer systems and physical components.
Lecture 5 covers this topic.

Chapter 3: Discrete Dynamics, State Machines

This chapter focuses on discrete dynamics and state machines.
The structure is focused on transitions, determinacy and receptiveness.

Default Transitions

Default transitions follow dashed lines, and are enabled when no other transition is active and its guard condition is true.
The guard condition specifies the conditions for enabling a transition.

Determinacy and Receptiveness

Deterministic state machines have exactly one transition enabled for each input in every state.
Receptiveness guarantees at least one possible transition for each input in every state.
This prevents a state machine from getting stuck.

Receptiveness

A receptive state machine has at least one transition possible for each allowed input value in every state.
The update function ensures that every state and input value has a corresponding action.
Implicit default transitions, used in diagrams, also help machines stay receptive.

Extended State Machines

Complex state machines (with many states) require more manageable formal notation.
Extended state machines use variables that are updated during transitions to prevent awkward graphical representations.

Notation for General Extended State Machines

Variables, inputs, and outputs are explicitly declared.

Example - Traffic Light State Machine

An extended state machine manages a traffic light at a pedestrian crossing.
It is time-triggered, reacting once per second.
Counts 60 seconds in the red state, then transitions to green.
The light stays green until a pedestrian request is detected.
A variable called count helps manage the time.
Different actions (e.g., changing the light to yellow or red) are defined on encountering special states triggered by time and/or pedestrian input.

Behaviors and Traces

FSM behavior is a sequential record of inputs, states, and outputs.
Traces are precise records of this behaviour.
Computation trees visually represent all possible behavior traces.
FSMs help analyze behaviors, helping predict and/or avoid unsafe states.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers Lecture 5 of Cyber Physical Systems, focusing on discrete dynamics and state machines. It includes concepts like default transitions, determinacy, and receptiveness in state machines. Test your understanding of these fundamental topics in CPS.