ACS133 Physical Systems - Key Vocabulary

Flashcards covering key definitions and concepts from the introductory lectures on Physical Systems.

Systems Engineering

The art of designing and optimising systems, starting with an expressed need and ending with specifications for all system elements. An integrative approach to enable the successful realization, use, and retirement of engineered systems, using systems principles, concepts, and scientific, technological, and management methods.

Systems Engineering Approach

Utilizes techniques across many disciplines to engineer a system; involves developing a mathematical model to represent the system, applying inputs, and analyzing outputs against specifications.

System Abstraction

Identifying necessary components and interconnections to create a model that represents required system characteristics with sufficient accuracy for the desired purposes or engineering task.

Complexity-Generalisation

The trade-off between a highly complex model (low level of abstraction) and a more general model (high level of abstraction).

Mathematical Model

A set of equations describing the relationship between input and output variables for a system, approximating to a required degree of accuracy.

First-Principles Approach

Uses physical laws (e.g., Newton’s law) to develop a model of a system or its components, based purely on understanding relevant processes.

Data-Driven Approach

Uses actual measurements of a system's inputs and outputs to create data, fitting a model that best represents the relationships observed in the measurements.

System

A group of entities that act together to achieve a desired purpose, with characteristics that cannot be entirely achieved by single elements alone.

Block Diagram

An abstract representation of a system, representing the input-output relationship in terms of individual processes or sub-systems and their relationships.

Plant

The main system under investigation.

Reference Input

The desired output response of the system.

Control Output

The measured output and subject of any control strategy implemented.

Disturbance

An input to the system not produced by the user, often undesired and unmeasured.

SISO

Single-Input Single-Output system, having one input and one output.

MISO

Multiple-Input Single-Output system, having multiple inputs and one output.

Lumped Parameter System

A system where a particular property is concentrated at discrete locations in space.

Distributed Parameter System

A system where a particular property is distributed continuously in space.

Static System

A system where the output at a certain time depends only on the input at that time.

Dynamic System

A system where the output at a certain time depends on the input at that and previous points in time.

Time Invariant System

A system where all parameters are fixed and do not change over time.

Time Varying System

A system where at least one parameter changes over time.

Linear System

A system that meets the properties of additivity and homogeneity, following the principle of superposition.

Non-Linear System

A system that does not adhere to the principle of superposition.

Quantised Variable

A variable that can only take a discrete number of values within a range.

Non-Quantised Variable

A variable that can take any value within a range.

Discrete Time Variable

A variable defined at fixed points in a time interval.

Continuous Time Variable

A variable defined at all points in a time interval.

Deterministic System

A system where the output at any time is known exactly from the inputs up to that point in time.

Stochastic System

A system where the output is unpredictable from past behavior, exhibiting some level of randomness.

Analogue System

A system in which all of the variables are continuous (analogue).

Digital System

A system in which all of the variables are discrete.

Hybrid System

A system that shows both continuous and discrete time behavior.

Linearization

Approximating a non-linear system using a linear system around a defined range of operation.

LTI System

A Linear Time-Invariant system; has a linear input-output relationship and its parameters do not change.

Unit Impulse Function

A function that has a value of 1 at t = 0 and a value of 0 at all other times.

Unit Impulse Response

The output response of a system when the input is a unit impulse.

Unit Step Function

A function that has a value of 1 for t > 0 and a value of 0 at all other times.

Unit Step Response

The output response of a system when the input is a unit step.

Saturation

Inside limits, the output changes with the input. Outside limits, the output is constant.

Deadzone

Inside limits, the output is constant with input changes. Outside limits, output changes with input.

Rise Time

The time it takes for a signal to go from 10% to 90% of its final value.

Overshoot Percentage

The amount by which a system's response exceeds its final value, expressed as a percentage.

Settling Time

The time it takes for a system's response to settle within a certain percentage (e.g., 5%) of its final value.

Steady State Error

The difference between the final value of a system's response and the reference input.

What is a thermal system?

A thermal system is a system in which the storage and transfer of heat are invloved

What are the three mechanisms of heat transfer?

The three mechanisms of heat transfer are conduction, convection, and radiation.

What is a fluid system?

A system that involves the flow of a fluid, such as gas or liquid. The property of a fluid, such as its density or viscosity, can affect its behaviour in a fluid system.

What is a fluid?

Any substance that can flow and change the shape of the volume that it occupies. We use 'fluid' for both gases and liquid.

What does it mean when an object is in thermal equilibrium?

When two objects are in thermal contact, the hotter object cools and the cooler object warms until no further changes take place.

What is conduction?

Heat transfer by means of contact of two bodies as higher speed particles (hotter) collide with slower ones (cooler) and therefore energy is transferred to the slower ones, making them heat up.

What is convection?

Heat transfer by motion of a fluid such as air or water.

What is the first law of thermal dynamics?

The total change in internal energy of a system is the sum of the heat added to it and the work done on it (conservation of energy)

What is the equation for thermal system with pure heat transfer and no work involved?

(rate of energy stored within system) = (heat flow into system) - (heat flow out of system)