Exam Prep Flashcards
What is fixed precision?
A tool used by microprocessors or computing systems to limit the numbers to a fixed number of bits
What is overflow?
When two numbers are added or subtracted and the correct result is a number that is outside of the range of allowable numbers for that precision
What is signed magnitude representation?
A way to sign integers. Put a 1 in front of a binary number to make it negative, a 0 to make it positive
What is ones complement representation?
A way to sign integers. Invert (replace 0s with 1s, vice versa) a binary number to it’s negative form
What is twos complement representation?
A way to sign integers. Use ones complement, but add 1 to its least significant bit
N bits can represent ___ different values
2^N
Define system clock
A component of a microcontroller. Provides a stable and consistent beat for the embedded control system
Define the central processing unit (CPU)
A component of a microcontroller. A multifunction math engine that takes commands stored in memory and uses them as an instruction list to accomplish tasks
Define the register
A component of a microcontroller. A digital location for holding temporary data, instructions or addresses
Define memory
A component of a microcontroller. Used to hold instructions and data
Define Line I/O
A component of a microcontroller. Standard input/output functions. Allows data to be transferred to and from the microcontroller
Define timer
A digital memory location that is updated or counted (incremented or decremented) at predetermined times
Define the accumulator (A) (a.k.a. working register)
A register type. This is where data for an input to the ALU is temporarily stored.
Describe how an accumulator system operates in steps
Example: Sum
- One number is fetched from memory and placed in the accumulator
- Second number is fetched from memory and placed in accumulator
- Result is placed into accumulator
Define status (a.k.a. condition code or flag register)
A register type. Contains information related to the result of the latest process carried out in the ALU. Each bit, called a flag, has a special significance. After an operation, each flag (bit) is set (1) or reset (0) to indicate a specific status
Define program counter (PC) (a.k.a. instruction pointer)
A register type. Used by the CPU to keep track of its position in a program. Contains the address of the memory location that contains the next program instruction. Updated after each instruction is executed. Program is executed sequentially unless an instruction alters the program counter
Define memory address register (MAR)
A register type. Contains the address of data. Example: Sum
- MAR loaded with address of first number
- Data at that address is then moved to the accumulator
- Memory address of second number loaded
- Data at the address is then added to data in the accumulator
- The result is then stored in a memory location addressed by the MAR
Define instruction register (IR)
A register type. Stores an instruction. Used by CPU to store an instruction after fetching it from memory, prior to decoding and execution
Define stack pointer register (SP)
A register type. Contents form an address which defines the top of the stack in RAM. The stack is a special area of the memory in which program counter values can be stored when a subroutine is being executed
Define general-purpose registers
A register type. May serve as temporary storage for data and addresses. May also be used in operations involving transfers from various other registers
Define buses
The bus is a shared set of communication lines that serves as the central nervous system of the computer. Data, address, and control signals are shared by all system components via the bus
Define data bus
Used to communicate words to and from data registers in the various system components
Define address bus
Used to select devices on the bus or specific data locations within memory
Define control bus
Transmits read and write signals, the system clock signal, and other control signals such as system interrupts
What is ROM?
Read Only Memory. Used for permanent storage of data, programmed at time of manufacture, don’t lose memory when power is removed
What is PROM?
Programmable ROM. ROM chips that can be programmed by the user. Cannot be reprogrammed
What is EPROM?
Erasable and Programmable ROM. Programmable and contents can be altered, cells store charges, programmed by producing a pattern of charged and uncharged cells, memory erasedb by shining ultraviolet light through quartz window
What is EEPROM?
Electrically Erasable PROM. Memory erased by applying a relatively high voltage
What is FLASH?
Similar to EEPROM with much larger capacities. Generally addressed by blocks rather than words
What is RAM?
Random Access Memory. Can be read or written to, holds data temporarily. Once power is removed, data in memory is lost
What is firmware?
Refers to programs stored in ROM
What is software?
Refers to programs stored in RAM. Must be loaded into memory each time system is powered up
What does the following assembly language program do?
LOAD 04 ADD 03 STORE 00 09
This program adds the numbers 4 and 3 together and stores the result in address 9. “LOAD 04” loads the accumulator with data 04. “ADD 03” takes data 03 into the ALU and adds the accumulator contents to it, result is copied to accumulator. “STORE 0009” stores accumulator content at address 0009.
Note: Addresses in this program are 16-bits long, so each address is split into high and low bytes
This is probably not super necessary to know anyways
Binary numbers presented to the microprocessor are called ________________
Machine language
Define mnemonics
Because programming in machine language is nearly impossible, every manufacturer of microcontrollers defines a three or four-letter code that describes the function of each instruction. These are called mnemonics, and programs written in mnemonics are referred to as assembly language
Define pipelining
Makes programs run faster. Since most microcontrollers fetch and execute instructions sequentially, pipelining is used to allow fetch and execution actions to overlap
Define an input/output (I/O) operation
A way for the CPU and external world to transfer data
Define peripheral device
The pieces of equipment that are interfaced to the I/O ports of a microcontroller
Define polling
A way to verify that the data retrieved from an I/O device is valid. Status bit is continually checked, CPU must wait for desired condition
Define interrupt
A way to verify that the data retrieved from an I/O device is valid. Interface chip sends interrupt to CPU when it has valid data; operation of CPU is suspended to handle interrupt
Define digital I/O
Digital input consists of reading the state on a given pin or line (bit) or group of pins (word). Digital output involves setting the output condition of a pin (or pins) to GND (0) or VCC (1)
Define multiplexers (MUX)
Essentially an electronic switch. Expands the number of available I/O lines. Could introduce errors such as crosstalk (adjacent channels interfere with channel being read), or transfer (output voltage not exactly the same as input)
Define serial I/O
Allows communication of data between devices one bit at a time. Utilize two or more digital I/O pins (TX and RX usually at minimum). Popular methods include:
USB (Universal Serial Bus)
CAN (Controller Area Network)
SPI (Serial Peripheral Interface)
I^2C Bus (Inter-IC Bus)
What are a few Arduino commands?
pinmode(pin, mode): configures specified pin as input or output
digitalRead(pin): reads value from specified pin, returned as HIGH or LOW
digitalWrite(pin, value): sets pin to value (HIGH or LOW)
Define Analog-to-Digital Converter (ADC)
Hybrid device with both an analog and digital side. Converts an analog voltage into a binary number through a process called quantization
Define resolution
The smallest increment of voltage that can be resolved by the ADC. The resolution per bit, Q, depends on the full-scale voltage range and the number of bits of the converter:
Q=E/(2^M)
E: full-scale voltage range
M: number of bits of the ADC
Note: Also a static characteristic in sensors (discussed later)
Define saturation error
Result from finite upper and lower limits of voltage response for an ADC. If the voltage exceeds upper or lower limits, the converter saturates (recorded signal does not vary with input)
Define conversion error
ADC converters may suffer from slight nonlinearity, zero offset errors, scale errors, or hysteresis. Errors are a direct consequence of the input quantization method
What are the most common ADC types?
Successive approximation converters, ramp converters, dual-ramp converters, and parallel or flash converters
Define successive approximation ADC
Most common type of ADC. Uses a trial-and-error approach for estimating the input voltage to be converted. This process requires one clock tick per bit. Increasing the number of bits to lower quantization error results in a direct increase in conversion time. Noise is the principle weakness of this type of ADC, particularly at the decision point for higher-order bits
Define ramp converters
Use the voltage level of a linear reference ramp signal to discern the voltage level of an analog input signal. Good for high accuracy, low level (<1 mV) measurements. Reference signal starts at zero and is increased at set time steps. At each time step, the ramp level is compared with the input voltage level
Define dual ramp converters
Similar to ramp converter, uses both a charge cycle and discharge cycle. Most accurate ADC type. Conversion times are relatively slow (4-8 ms), often used for digital voltmeters
Define parallel or flash converters
Fastest type of ADC (1 clock cycle). Typically used in oscilloscopes and spectral analyzers. Also expensive
What are some common Arduino commands for analog I/O
analogReference(type): configures the reference voltage used for analog input. type = DEFAULT, INTERNAL or EXTERNAL. DEFAULT: supply voltage, INTERNAL: built-in reference, EXTERNAL: defined by the voltage applied to the AREF pin
analogRead(pin): reads value from specified analog pin. returns int ranging from 0 to 1023 or 0 to 4095
analogWrite(pin, value): Approximates analog voltage on pin by writing a PWM square wave (f = 490 Hz). value sets the duty cycle (0 = always off; 255 = always on)
dacWrite(pin, value): value is the digital value to be converted, ranging from 0 to 255
Define duty cycle
How long the output is high during one period, varying the duty cycles will vary the output voltage in PWM
Define version control
Refers to the management of changes to documents, programs, and other information stored in computer files. Typically only stores differences between file versions “diffs”, rather than entire copy of file
Define a version control system (VCS)
Stores all revisions made to files, along with timestamps
What are the advantages of using version control?
Backup and Restore: Files are saved as hey are edited, and you can jump to any moment in time
Synchronization: Allows people to share files and stay up-to-date with the latest version
Short-Term Undo: Trying something out with a file and messed it up? Throw away your changes and go back to “last known good” version in the database
Long-Term Undo: Really bad screw up, you can go back to the very beginning of the screw up
Track Changes: Can leave messages explaining why certain changes were made, makes it easy to see how file has changed over time
Track Ownership: A VCS tags every change with the name of the person who made it
Sandboxing: If you’re making a big change, you can make temporary changes in an isolated area, test and work out the kinks before “checking in” your changes
Branching and Merging: Larger sandbox, can branch a copy of your code into a separate area and modify it in isolation (tracking changes separately), can merge back later
Define centralized version control
Traditional version control system; server with database maintains repository, clients have a working version. Challenges include multi-developer conflicts, client/server communication
Define distributed version control
Authoritative server by convention only, every working checkout is a repository, get version control even when detached, backups are trivial
What are some version control terms and their definitions?
Repository (repo): The database storing the files in VC
Add: Put a file into the repo for the first time (i.e. begin tracking with version control)
Revision: What version a file is on
Check out: Set the current version of the file from the repo
Commit: Write changes to repository
Head: The latest revision in the repo
Branch: Establishes a “fork” of the code that may be developed independently
Merge: Combining changes from multiple branches
Define git
Open source, multiplatform, very fast, distributed VCS
Define transducer
A device that converts variations of one quantity into those of another (same or different form). Transducer encompass both sensors and actuators
Define sensor
A device that detects a change in a physical stimulus and turns it into a signal that can be measured or recorded
Define actuator
A device that produces an observable output
What are the six signal types? (Hint: they’re all based on types of energy)
- Radiant: Radio waves, visible light, infrared
- Mechanical: Motion and forces (displacement, velocity, acceleration, etc.)
- Thermal: Kinetic energy of atoms and molecules
- Electrical: Current, voltage, resistance, etc.
- Magnetic: Magnetic flux, field strength, etc.
6: Chemical: Chemical composition, pH value, etc.
What are the three main types of transducer signals?
- Analog: Signal is a proportional representation, or analogy, of the original parameter
- Digital: A function is used to represent the original parameter value
- Coded digital: A parallel digital signal represents the original parameter signal
Define static charactersistics
Relate to performance, given a steady-state input condition
Define dynamic charactersistics
Describe behaviour between the time that the input value changes and the time at which the steady-state condition is achieved
Define range and span
A static characteristic. Range defines the limits between which the input can vary (ideal would be from negative infinity to positive infinity), in general, a wide range implies low resolution and low accuracy. Span is just maximum value minus minimum value (i.e. -3 to 3, span = 6)
Define error
A static characteristic. Difference between the result of the measurement and the true value of the quantity being measured (error = measured value - true value)
What are the two types of errors and their definitions?
- Bias error: Consistent and repeatable. Could be calibration issues, loading (intrusive sensor, alters measurand), and variables other than the measurand. Bias error = average of readings - true value
- Precision error: Random. Precision errors originate from the sensor itself, caused by uncontrolled variables in the sensing process
Define accuracy
A static characteristic. Measure of how closely a measured value agrees with the true value. Accuracy (%) = 100 - (reference value - measured value)/(reference value) * 100
Define precision
A static characteristic. Clarity or sharpness of a measurement, closely related to accuracy
Define sensitivity (scale factor)
A static characteristic. Ratio of the change in input to the change in output. Often a key factor in sensor selection
Define hysteresis
A static characteristic. Providing a different output value for the same input, depending on whether that value was reached by a continuously increasing change or a continually decreasing change
Define threshold
A static characteristic. Smallest input change from zero that makes an output change discernable. Note: Dead zone is the total range of input over which the output remains zero
Define stability
A static characteristic. The ability of a sensor to give the same output when used to measure a constant input over a period of time. Expressed as a percentage of the full output range. Described by drift (shifts in measured reading while physical variable remains unchanged) and zero drift (drift at the zero value of the variable). Caused by sensitivity to factors other than the measurand and internal sensor changes
Define repeatability
A static characteristic. Ability to produce the same output for repeated applications of the input value. Includes measurement process and environment, same physical variable and conditions, every time
Define linearity
A static characteristic. A measure of the “steadiness” of sensitivity throughout the active range (dx/dy constant over entire range)
Define input/output impedances
A static characteristic. Minimize loading effects: Changing behaviour of the system that device is attached to, changing process
Define response time
A dynamic characteristic. Time that elapses before 95% of actual value is reached after a step input is applied
Define time constant
A dynamic characteristic. 63.2% of response time, measure of inertia, how fast sensor responds to changes in input, the bigger this value = slower the response
Define rise time
A dynamic characteristic. Time taken for output to rise to some specified percentage of steady-state output
Define settling time
A dynamic characteristic. Time to settle within a specified percentage of the steady-state value
Describe the process of sensor selection
- Identify the nature of the measurement required:
Variable to be measured Nominal range Range of value Accuracy required Required speed of measurement Reliability required Environmental conditions
- Identify the nature of the output required from the sensor
Needed to determine signal conditioning requirements
- Identify possible solutions, should consider:
Range Accuracy Linearity Speed of response Reliability Maintainability Life Power supply requirements Ruggedness Availability Cost
What are the categories of electronic sensors
- Go/No Go sensors - On/Off sensors
2. Analog sensors - output proportional to stimulus
Define microswitch
Commonly used, small electric switch that requires physical contact and a small operating force to close the contacts
Define sensing resistors
Resistance proportional to target measurement (angular/linear position, force/pressure, temperature, light intensity, sound intensity)
Define potentiometer
Converts mechanical input (position of wiper terminal) into electrical signal by potential/voltage divider principle
Define force sensing resistors (FSR)
Polymer thick film (PTF) devices which exhibit a decrease in resistance with an increase in applied force. In general, FSR response approximately follows an inverse power-law characteristic
Define thermistor
Temperature sensitive resistors. Resistance of a thermistor decreases with increasing temperature
Define photoresistors
Resistance varies with light intensity
Define electromagnetic spectrum
The distribution of electromagnetic radiation according to energy, frequency, or wavelength
Define PN junction light detectors
All PN junctions are light sensitive, largest family of photonic semiconductors, most are made from silicon and can detect both visible light and near-infrared, photodiodes are PN junctions specifically designed for light detection
Define photodiodes
Essentially reverse-biased diodes with a transparent envelope. Photodiodes generally have a fast response, have a peak response in the near infrared region, response in the visible spectrum is often significantly weaker
Define phototransistors
Photo-conductive detector that allows current from an external power supply to flow in response to light. A series resistor is necessary to ensure that current flows through the phototransistor
Define digital optical encoders
Optical rotary encoders use geometric masking which allows light to pass through unmasked slits and be detected by photodetectors on the other side of the disk. Designed to produce a digital word that distinguishes 2^N distinct positions of the shaft, where N is the number of tracks
Define gray code
One track (bit) changes state for each count transition
Define binary code
multiple tracks (bits) can change during count transitions
Define incremental (relative) encoders
Uses only two tracks and two sensors. Tracks A and B are a 1/4 cycle out of phase with one another yielding quadrature signals
Define IR distance measuring sensors
Sharm analog output distance measuring sensor. There are three models with different ranges (4-15 cm, 10-80 cm, 20-150 cm)
Define sharp IR distance sensors
Uses a lens and a position sensitive detector (PSD) to accurately determine distance to object
What is the process for selecting a photodetector?
A few considerations when selecting a photodetector include:
- Is the device sensitive enough for the application?
- Do the wavelength characteristics of the detector match the source?
- Is the device cost effective?
- Is there a clear path between the light source(s) and detector?
- Is the device electrically compatible with the rest of the circuit
Define ultrasonic sensors
Noncontact measurement of distance to nearby objects. A single transducer may operate as a source/sensor pair. Transducer generates a short burst of high frequency sound, travels as a narrow cone, objects in path of sound are reflected back to sensor, same transducer acts as a microphone and converts to an electrical signal, time between pulse and echo are measured
Define the hall effect
The phenomenon of current flowing through a conductor being deflected from a straight-line path by a magnetic field
Define hall effect sensors
Sensors that detect the hall effect lol. If a sensor is supplied by a constant current, the hall voltage is a measure of the magnetic flux density. Generally supplied as an integrated circuit, complete with necessary signal processing circuitry. Able to operate as switches at rates up to 100 kHz, cost less than electromechanical switches, immune to environmental contaminants, can be used as position/displacement/proximity sensors if object being sensed is fit with a small permanent magnet
Define design
The quest for simplicity and order, the process of inventing artifacts that display a new physical order, organization, and/or form in response to function
What are five types of engineering design?
- Selection design: Choose item(s) from a catalog
- Configuration design: Organize the packaging of components
- Parametric design: Finding variables or parameters
- Redesign, alternative design: Modifying and existing product
- Original design: Develop a totally new product
What factors must be considered in configuration design?
Spatial limitations, product interactions with other physical objects/the user(s), maintenance, wear, desired customization by the user, need to include standard parts and assemblies, need to conform to industrial standards, need to replace consumable materials
Define analysis problem
A well-defined problem with one correct solution
Define design problem
An ill-defined problem with numerous satisfactory solutions
Describe the engineering design process
- Specification Development/Planning Phase: Determine need, customer and engineering requirements, develop a project plan
- Conceptual Design Phase: generate and evaluate concepts select best solution
- Detail Design Phase: CAD models, engineering drawings, design documentation, part specification, software development, prototype evaluation
- Production Phase: Component manufacture and assembly, plant facilities/capabilities
- Service phase: Installation, use, maintenance and safety
- Product retirement phase: Length of use, disposal, and recycle
Note: Steps 1-3 are the MSE 2202 design project. Steps 4-6 are the consideration of production, service, and retirement phases will have an impact on the MSE 2202 design project, especially in the detailed design phase
Describe the importance of customer research
Customer research is essential to developing any new product or service. Without a complete understanding of your customers’ wants and needs, you may be developing a product that is out of sync with your market and ultimately doomed to failure
What methods could be used to determine customer wants and needs?
Use existing feedback, surveys, customer interviews, focus groups, competitive analysis, or just ask them
What do we mean when we say “customer requirements must be discriminatory” when talking about customer wants and needs?
Requirements must reveal the differences between alternatives, requirements should serve to distinguish alternatives from one another during evaluation
What do we mean when we say “customer requirements must be measurable” when talking about customer wants and needs?
Ideally, all identified requirements are measurable, should be quantifiable
What do we mean when we say “customer requirements must be orthogonal” when talking about customer wants and needs?
Each requirement should identify a unique feature of the alternative
What do we mean when we say “customer requirements must be universal” when talking about customer wants and needs?
A universal requirement characterizes an important attribute of all of the proposed alternatives, applicable to all alternatives under consideration
What do we mean when we say “customer requirements must be external to the problem” when talking about customer wants and needs?
Must not impose design choices
Define product design specification (PDS) list
A detailed summary of the design requirements to be met in order to produce a successful product or process, write a separate specification for each element of the PDS list. If possible, the specification should be expressed in quantitative terms (give limits within which acceptable performance lies if appropriate). Performance attributes may be divided into attributes that must be satisfied or would be nice to satisfy
In the context of PDS lists, define performance
List the functions to be performed by the product and the desired level of performance (engineering requirements, targets, etc.)
In the context of PDS lists, define operating environment
Specify the operating environment for the product (range of temperature, pressure range, etc.)
In the context of PDS lists, define standards
List relevant standards that must be adhered to (ANSI, ASTM, etc.)
In the context of PDS lists, define materials
Poorly chosen materials can lead to product failure or unnecessary costs (material performance characteristics, key material properties)
In the context of PDS lists, define customer
List an information on customer likes, dislikes, preferences, and prejudices
In the context of PDS lists, define ergonomics
Identify any man-machine interface (need for handles, buttons, displays, etc.)
In the context of PDS lists, define aesthetics, appearance, and finish
Consider colour, shape, texture, and form at the onset of design (this is what the customer sees first)
In the context of PDS lists, define competition benchmarking
Perform a thorough analysis of existing and future competitors (determine how the customer perceives the competition’s ability to meet each design requirement)
In the context of PDS lists, define quality and reliability
High risk areas of the product should be identified, and the risks minimized using formal trade-off techniques in the design process (product must meet or exceed customer’s expectations)
In the context of PDS lists, define testing and inspection
Specify the tests required to demonstrate that the product meets the desired specifications, and any quality requirements
In the context of PDS lists, define maintenance and logistics
Specify ease of access to the components likely to require maintenance (speed and ease of repair can influence customer’s acceptance of the product)
In the context of PDS lists, define service life
Establish the expected service life and operation duty cycle for the product (how long is it expected to last while in operation)
In the context of PDS lists, define market constraints
List any feedback from the marketplace
In the context of PDS lists, define target product cost
Establish selling cost at the onset of the design process (retail price is often 3x manufacturing cost for mass produced items)
In the context of PDS lists, define quantity
Estimate the number of products to be produced (cost/unit to fabricate is influenced by production method)
In the context of PDS lists, define product life span
Predict how long the product is to remain on the market (influences investment decisions, potential sales)
In the context of PDS lists, define shelf life in storage
Consideration must be made for protecting parts from the natural elements wile not in use (some products must be stored on hazardous sites for prolonged periods of time)
In the context of PDS lists, define size
This is an important constraint for shipping, storage, and marketing
In the context of PDS lists, define weight
An important factor in handling a product on the manufacturing floor, transportation and installation (related to size and cost)
In the context of PDS lists, define shipping
Determine how the product will be delivered (size of box cars, weight on trucks)
In the context of PDS lists, define packaging
Specify the type of packaging required for shipping and storage (protection during transportation, display)
In the context of PDS lists, define in-house processes
Identify any specified treatment of parts (heat treatment, water resistant coating)
In the context of PDS lists, define manufacturing facilities
Determine whether the product is to be produced in an existing facility or a new plant must be built (affects design choices, directly affects cost)
In the context of PDS lists, define patents
Consult all areas of useful information prior to launching the design (prevent costly lawsuits)
In the context of PDS lists, define design schedule
List definite milestones that the design team is required to meet (schedule adequate time to due design activity, testing)
In the context of PDS lists, define company constraints
Any constraints imposed by company must be listed (limits on new plant investments, preferred vendors/suppliers)
In the context of PDS lists, define social and political factors
List any constraints arising from government regulation (pollution laws, seatbelt legislation, sustainability)
In the context of PDS lists, define safety
Critical parts whose failure will cause injury must be identified and documented (warning labels should be devised and operating manuals should clearly spell out what is abusive use of the product)
How can customer and design needs be balanced?
Customer requirements are linked with product design specifications by a QFD
Describe the steps in the QFD process
- Identify the customers
- Determine the customers’ requirements
- Determine relative importance of the requirements
- Generate engineering specifications
- Relate customers requirements to engineering specifications
- Identify relationships between engineering requirements
- Identify and evaluate the competition
- Set engineering targets
Describe the “Identify Customers” step in the QFD process
Listen to the voice of the customer, but the customer must be identified first. In most cases, there is more than one customer (consumer, regulatory agencies, manufacturing, etc.)
Describe the “Determine Customer Requirements” step in the QFD process
What do the customers need and want? Example:
Consumer: Product works as it should, lasts long, easy to maintain, etc.
Manufacturing: Easy to produce, uses available resources, etc.
Marketing/Sales: Meets customer requirements, easy to package, etc.
Describe the “Determine Importance” step in the QFD process
Consider relative importance of customers’ requirements. Use a weighting factor for each requirement. For rank ordering, assign “1” to the requirement with lowest priority, then increase from there
Describe the “Generate Engineering Specifications” step in the QFD process
How will the customers’ requirements be met? The goal is to develop a set of engineering specifications from the customers’ requirements
Describe the “Relate Requirements” step in the QFD process
Relate customer requirements to engineering specifications. Each cell represents how an engineering parameter relates to a customer requirement. Each customer requirement should have at least one specification with a strong relationship (9=strong relationship, 3=medium relationship, 1=weak relationship, blank=no relationship)
Describe the “Identify Relationships” step in the QFD process
Identify relationships between engineering specifications, may be dependent on one another (9=strong relationship, 3=medium relationship, 1=weak relationship, -1=weak negative relationship, -3=medium negative relationship, -9=strong negative relationship, blank=no relationship)
Describe the “Identify and Evaluate Competition” step in the QFD process
How satisfied are customers now? The goal is to determine how the customer perceives the competition’s ability to meet each of the requirements. The ranking system goes as follows:
- Does not meet the requirement at all
- Meets the requirement slightly
- Meets the requirement somewhat
- Meets the requirement mostly
- Fulfills the requirement completely
Describe the “Set Engineering Targets” step in the QFD process
How much is good enough? Determine target value for each engineering specification: Evaluate competing products with respect to engineering specification, look at set customer targets, use the above two pieces of information to set targets
Define concept
An idea that can be represented in a rough sketch or with notes of what might someday be a product
What are some sources for concept ideas
Ideation, brainstorming, patents, reverse engineering, reference books and trade journals, experts to help generate concepts, functional decomposition and morphological analysis
Describe ideation in the context of concept ideas
- Get a general idea of the design problem ad develop different ways to tackle it
- Find feasible ideas
- Pick, choose, and recombine ideas
- Refine
Describe brainstorming in the context of concept ideas
Organized approach for producing creative ideas by letting the mind think without interruption
What are the fundamental principles of brainstorming
- Criticism is not allowed
- All ideas brought forth should be picked up by the other people
- Participants should divulge all ideas that enter their mind
- Provide as many ideas as possible within a relatively short time
Describe the functional decomposition technique and how it coincides with morphological analysis
- Find the overall function that needs to be accomplished
- Decompose the function into sub-functions (perform functional decomposition). Goal is to refine the overall function statement as much as possible
Functional decomposition is used to identify the necessary product functionality. Morphological analysis is used to explore alternative means and combinations of achieving that functionality
Describe the process for developing concepts for each function
- List product functions (functional decomposition)
- List the possible “means” for each function (morphological analysis)
- Chart functions and means and explore combinations
What are the steps in concept evaluation?
- Feasibility Judgement
- Technological Readiness Assessment
- Go/No-Go Screening
- Decision Tree
- Decision Matrix
Describe the “Feasibility Judgement” step in concept evaluation
Eliminating unfeasible concepts based on engineering judgement, supported by simple mathematical models, estimates and rough calculations if possible
Describe the “Technological Readiness Assessment” step in concept evaluation
Determining the readiness of the technology incorporated in the design concepts. Selecting immature technology may lead to excessive costs, delays, unexpected problems, and customer dissatisfaction. Selecting new technology can additionally provide competitive advantage
What are some guidelines for the technology readiness assessment
- Has the technology been demonstrated to work?
- Can the technology be manufactured with known processes?
- Is the cost of the technology competitive with existing technology?
- Do the benefits justify the risk and uncertainty associated with the new technology?
- Can the technology be safely controlled?
- Have the failure modes been identified?
- Is the technology controllable throughout the product’s life cycle?
Describe the “Go/No-Go Screening” step in concept evaluation
Compare each alternative with the customer requirements in an absolute fashion. Each customer requirement must be transformed into a question and should be answerable as either yes (go), maybe (go), or no (no-go)
Describe how the decision matrix works
Identifies the strongest concepts, and helps foster new concepts. Provides a means of scoring each concept relative to another
Describe Pugh concept selection
The simple version of the decision matrix. Used for rough comparison of concepts at the early stage of design
Describe how to use the Pugh concept selection method
- Identify criteria for evaluation
- Choose one concept to be a datum
- For each criterion, decide if a candidate is:
Better than the datum (+)
The same (S)
Worse than the datum (-)
- Pick the best concepts based on the total score, then attack their weaknesses (minuses) or combine the best aspects of different concepts if possible (combine pluses)
Describe how to go from Pugh to decision matrices
Include the relative importance or weights of the criteria, use a multi-valued numeric scale to rate concepts (e.g. 1 - 10), multiply ratings with weights, and sum to get relative total scores
Describe how to assign relative importance weight factor (WF)
- Decide upon the range of values (e.g. 1 - 100)
- Separate the range into general categories of significance, e.g. critical, important, optional
- Assign a weighing factor for each goal, considering all available information
Might be helpful to look at the slides for this week for the visual examples
Define finite state machines (FSM)
Very common in mechatronic systems for us to do different things in response to the same input, FSMs are an attempt to capture the idea that the response of the system depends NOT ONLY on the input, BUT ALSO on the history of the system
Identify and define the two building blocks of FSMs
Bubbles: A state. States have names (best to use a name that somehow represents the history that got there, can also be associated with activities or outputs)
Arcs: Directed lines that join states. Always associated with input conditions. An arc means we go from source state to destination state in response to input condition. Putting an output on an arc is a way to capture that we do the activity during the transition
Might be helpful to look at the slides for this
Define event driven programming
Requires significant software infrastructure. Basically, it requires associating input changes with triggered events or messages or callbacks. In most cases, this implies the presence of a modern, real-time operating system, though it doesn’t need it
Define polled, synchronous programming
“Pretend” the system is a synchronous circuit with a clock. These operations work as a team. The goal is that one path through the loop always takes exactly the same time.
Might be helpful to look at the slides for this
With physical inputs, bouncing becomes an issue (think of a button, when you press it down, it physically bounces and messes up the state that is trying to be communicated). What are some solutions to this?
- Look once, then look again later (most common)
- Sample often (1111 means on, 0000 means off)
- Hardware debouncing (requires analog filter and Schmitt trigger)
What are the roles of this step when processing states during the polled approach?
- State transition, this is where we encode the arc. In each state, you go through a set of questions of the form: If the input is like this, then we are going to that state next. There must always be a no change transition in polled approach
- Action, these can be condition dependent (we do THIS if THAT happens) or state based (we ALWAYS do this in this state) or both
This entire week might be best to look at the slides for. It’s short so it’s fine
What are the parts of a typical drawing?
Sheet, views, notes, title block (TOC), and revision block
Describe form in the context of engineering drawings
Shown with pictures, orthographic projection/views
Define orthogonal (projected) views
Primary vies on a drawing set at 90 degrees to each other. Created by placing part in a virtual box and looking through each side
Define first angle projection
A projection standard symbolized with a circle followed by a right-pointing trapezoid. This is the ISO/European standard, like rolling the part on a table. Seeing the diagrams in the slides may help
Define third angle projection
A projection standard symbolized with a right-pointing trapezoid followed by a circle. North American standard, like walking around the part. Seeing the diagrams in the slides may help
Describe a few things that are deemed as orthographic standard practice
Choose the front view as the most descriptive. Determine views to best represent object. Use minimum number of views to completely describe the object. Views must be aligned. Views should not be labeled
Define auxiliary view
An extra view of an object when the 6 principal views don’t describe an object (or some of its features) clearly or completely
Define isometric view
3D view of part to help visualization. Used only for a visual reference, should not be dimensioned, common for assembly drawings
Define section view
Useful to show interior features without using hidden lines. Must show section line in another view that indicates the cutting plane and the direction of the view. Does not need to be aligned but often is shown aligned to enhance clarity. Must have unique letter label
Define cut-away view
Shows part form behind front face
Define detail views
Presents an enlargement of another view to enhance the clarity of small features. Must show detail area in parent view with label. is not aligned with parent view. Must have unique letter label and scale must be indicated since it is different from the parent view
Define break view
For long parts. Some important features of the break view are instance numbers (indicate number of spaces and holes) and break line in overall length dimension (indicates the presence of a break view)
Describe how visible (solid) lines describe the features of a drawing
Illustrate external features and outlines, as if looking at the part
Describe how hidden (dashed) lines describe the features of a drawing
Illustrate anything behind the front face of the view, as if looking through the part
Describe how phantom (dotted or short/long dash) lines describe the features of a drawing
Used to represent a feature or component that is not part of the specified part or assembly, also used to indicate alternative configurations. Slide 35 shows a good example
Describe how centre (long/short alternating dash) lines describe the features of a drawing
Indicates the centre of geometry
Describe how section (short dash) lines describe the features of a drawing
Indicate views
What are the general rules for dimensions in engineering drawings?
- Text height is typically either .12” or 3 mm
- Text is always uppercase
- Units are usually either inches or millimeters
- If using inches:
No zero precedes decimal (.250)
Dimensions expressed to same number of decimals as its tolerance (.250 ± .002)
- If using millimeters:
Zero precedes the decimal (0.5)
No trailing zeros are required (3.25 ± 0.1)
- Dimension text is always horizontal
- Do not dimension to hidden lines
Identify and define the dimension types
- Standard (incremental)
- Base line (absolute)
- Ordinate (absolute)
Slides are helpful to visualize different types
What is meant by absolute vs. incremental types of dimensions
Incremental: Point to point; one position to the next
Absolute: Reference one single point (DATUM)
What are some radial dimension conventions?
Small radii are called fillets. The preference is to use unlocated centres (easier to measure), see slide for visual. Never dimension to radii tangent points
What are some hole dimension conventions?
Use a depth symbol with the depth of the full diameter when it is not a through hole (including counterbores/countersinks, but use an additional counterbore/countersinks symbol)
What are some thread dimension conventions?
Dimension the pitch, major, and minor diameter. Usually show section for blind threaded holes. Note that the hole must be at least 4 threads deeper. Use the metric or American thread standard:
Metric: M24X2
M = Metric standard 24 = Major diameter 2 = Pitch
minor diameter is shown as hidden
American: .50-13 UNC
UNC = American standard .50 = Major diameter 13 = Threads/inch (1/pitch)
Identify a few dimensioning techniques
- Must give position and size of each feature but only once on the drawing (don’t dimension the same feature again in a different view unless dimension is for reference only)
- Dimension based on the function of the feature
- Dimension to reduce tolerance stack-up for critical features
- Always dimension position of holes to their centre not their edge
Describe tolerances
All real-world parts have variation in their features so every dimensions on the drawing must indicate the allowable variation. Use of title block general tolerance note reduces clutter in the drawing. Note: Tight tolerances = $$$, should aim to use generous tolerances
Identify and define the tolerance types
Basic: Standard tolerance from title block
Symmetric: Shows allowable deviation from nominal - above or below
Bilateral: Shows allowable deviation from nominal - above or below
Unilateral: Only allows deviation from nominal in one direction
Limit: Gives two dimensions - anything in between is acceptable
Min/Max (Single Limit): Anything over/under
Fits: Alone, with, or without tolerance - references standard engineering fits
See slide for visual examples
Identify and define the different types of fit
Clearance fit: Limits of size defined such that a clearance always results when mating parts are assembled
Interference fit: Limits of size are prescribed such that interference always results when mating parts are assembled
Transition fit: Limits of size are prescribed such that either clearance or an interference may result when mating parts are assembled
Line fit: Limits of size are prescribed such that surface contact or clearance may result when mating parts are assembled
Describe the basic hole system
In the basic hole system, the minimum (lower limit) hole size is taken as the basic size. Stock hole is made “first” and then shaft is made to particular type of fit to suit the hole
Describe the basic shaft system
In the basic shaft system, the maximum (upper limit) shaft size is taken as the basic size. Stock shaft is created “first” and then the hole is made to particular type of fit to suit the shaft
Define geometric dimensioning and tolerancing (GD&T)
The allowable deviation from nominal form. GD&T uses symbols to communicate geometric specifications, see slide for visuals. GD&T is the only way to guarantee correct form, dimensions only guarantee size. Basically IRL constraints in solidworks
What are the uses of GD&T?
- Datum - Point of reference (face, edge, or hole)
- Symbol - Type of deviation
- Tolerance - Allowable variation (given as distance)
Define surface finish
Quality/smoothness of finish
Define roughness average (R_a)
Expressed in microinches, micrometres, or roughness grade numbers N1 to N12. The “N” series of roughness grade numbers is often used in lieu of the roughness average values to avoid misinterpretation when drawings are exchanged internationally
Try your best to describe the symbols used for basic surface finishes
- Check mark: Surface may be produce by any method
- Check mark with horizontal line: Material removal required
- Check mark with circle: Material removal prohibited
- Check mark with one number or N value: Roughness average values specified in microinches, micrometers, or roughness grade numbers
- Check mark with two numbers or N values: Maximum and minimum roughness average values specified in microinches, micrometers, or roughness grade numbers
Describe the lay symbols
- Two parallel lines: Lay parallel to the line representing the surface to which the symbol is applied
- Perpendicular lines: Lay perpendicular to the line representing the surface to which the symbol is applied
- “X”: Lay angular in both directions to line representing the surface to which the symbol is applied
- “M”: Lay multidirectional
- “C”: Lay approximately circular relative to the centre of the surface to which the symbol is applied
- “R”: Lay approximately radial relative to the centre of the surface to which the symbol is applied
- “P”: Lay nondirectional, pitted, or protuberant
Name five things all drawings contain
- Drawing templates or borders
- Drawing views
- Title block
- Revision block
- Notes - special or standard
Name five things that a drawing view could contain
- Dimensions
- Tolerances
- Geometric tolerancing
- Surface finish information
- Allowable tool mark information
Define title block
Contains any information that cannot be communicated through orthographic views and dimensions. A few examples include:
Part materials Part quantities Authors, supervisors, inspectors Inspection information/standard Finishing information: painting, anodizing, heat treating Customer information Company information 3rd angle projection symbol is important if drawing is used internationally
Describe drawing scale
The title block indicates the scale predominantly used for views on the drawing. If a view uses a different scale, it must be indicated under that view. Scales are given as whole number ratios (must have 1 in the ratio):
For scaling up - 2:1, 4:1, 10:1
For scaling down - 1:2, 1:5, 1:20
Define revision block
Used to track changes to the drawing. Normally contains revision, description, date, and approval
Describe special notes on drawings
For nonstandard information. Can be located anywhere on the drawing or title block. Provides useful information not covered by dimensions, symbols or in the title block, can also be used with arrows to indicate features of importance. Try to limit the number of notes because they may be misinterpreted
Define design for assembly (DFA)
A product designed to simplify the product so that the cost of assembly is reduced. Usually this improves quality and reliability and a reduction in cost/equipment
What does DFA achieve?
Reduced part count, reduced labour content, shortened product design time
Define DFA evaluation
A technique used to measure the ease with which a product can be assembled
Define assembly efficiency score
A relative measure used to compare alternative designs of the same or similar products through 13 guidelines (score has no real meaning). Can range from 0 to 104 (8 x 13). The higher the score, the better the assembly
Describe the “overall component count should be minimized” guideline for DFA evaluation
Find the theoretical minimum number of components. Examine each pair of adjacent components in the design to determine if they really need to be separate. Bolts, nuts, and clips should be included in the part count. The components must be separate if:
- The design is to operate mechanically
- The components must be made of different materials
- If assembly or disassembly is impossible
After this, find the improvement potential (I.P.)
I.P. = (actual number of components - theoretical minimum)/(actual number of components)
Note: Part reduction should not add costs by making the remaining parts too heavy or too complex
Lastly, rate the product on the worksheet:
I.P. < 10% = outstanding 10% < I.P. < 20% = very good 20% < I.P. < 40% = good 40% < I.P. < 60% = fair I.P. > 60% = poor
Describe the “make minimum use of separate fasteners” guideline for DFA evaluation
Every fastener adds costs and reduces strength. If more than 1/3 of the product components are fasteners, then the assembly logic should be questioned
Describe the “design the product with a base component for locating other components” guideline for DFA evaluation
The ideal design is built like a layer cake
Describe the “don’t require the base to be repositioned during assembly” guideline for DFA evaluation
Repositioning is time consuming and costly. If it has to be repositioned more than twice during assembly, it is considered a poor design. Ideally, there is no repositioning of the base
Describe the “make the assembly sequence efficient” guideline for DFA evaluation
Uses the fewest possible steps, avoids the risk of damaging components, avoids awkward or unstable positions for product/assembly personnel/machinery, avoids creating many disconnected subassemblies to be joined later
Describe the “avoid component characteristics that complicate retrieval” guideline for DFA evaluation
Three component characteristics that make retrieval difficult:
- Tangling (problem for some components when stored in boxes/trays)
- Nesting (components jam inside each other)
- Flexibility (gaskets, tubing, and wiring harnesses; make components as few, as short and as stiff as possible)
Describe the “design components for a specific type of retrieval, handling and insertion” guideline for DFA evaluation
Three types of assembly systems:
- Manual assembly (low volume, less than 250,000 units annually)
- Robotic assembly (mid-high volume, between 250,000-2,000,000 units annually)
- Special-purpose transfer machine assembly (very high volume, more than 2,000,000 units annually)
Describe the “design all components for end-to-end symmetry” guideline for DFA evaluation
End-to-end symmetry (symmetry about an axis perpendicular to the axis of insertion) allows a component to be inserted into an assembly with either end first. If a component can only be installed in the assembly in one way, the it must be oriented and inserted in just that way. This requires time and either worker dexterity or assembly machine complexity
Describe the “design all components for symmetry about their axes of insertion” guideline for DFA evaluation
The designer should strive for rotational symmetry, faster assembly
Describe the “design components that are not symmetric about their axes of insertion to be clearly asymmetric” guideline for DFA evaluation
The goal for this guideline is to make components that can be inserted only in the way intended. Components that are clearly asymmetric avoid ambiguities in the process or handling
Describe the “design components to mate through straight-line assembly, all from the same direction” guideline for DFA evaluation
This guideline is intended to minimize the motions of assembly. If the components mate through straight-line motion and the motion is always from the same direction, the assembly will fall together from above. Downward motion is preferred as it can take advantage of gravity
Describe the “design use of chamfers, leads and compliance to facilitate insertion and alignment” guideline for DFA evaluation
To make the actual insertion or mating of a component as easy as possible, each component should guide itself into place. Three features may be incorporated in the component design to facilitate insertion and alignment:
- Chamfers - rounded corners
- Leads - making the front end of the component smaller
- Compliance - making the component “elastic”
Describe the “maximize component accessibility” guideline for DFA evaluation
Assembly can be difficult if components have no clearance for grasping, efficiency is negatively impacted if a component must be inserted in an awkward spot. If both assembly and maintenance are required, then additional room must be allowed for the repair tools to mate with the component
Describe a few additional DFA guidelines
Parts that are too thin or have beveled edges may shingle during feeding, try designing flat parts with adequate thickness or add a flat to the leading edge of the beveled parts. Design parts with ends that are “flat”
Define ergonomics (a.k.a. human factors)
Used to describe abilities, limitations and other physiological or behavioural characteristics of humans that affect the design of tools, machines, consumer products, systems, tasks, jobs, and environments
Describe characteristics of display effectiveness
Conspicuity: Prominently located, attention getting
Emphasis: Important items/words visually emphasized
Legibility: Character fonts, size, and contrast
Intelligibility: Succinctly communicate information
Visibility: Visible in all lighting conditions
Maintainability: Resist aging, wear, vandalism
Standardization: Use standard words and symbols whenever possible
Define anthropometric data
Used to describe the range of capabilities for human populations with data collected by governments, military, and large corporations (usually expressed in terms of percentiles)
Describe how ergonomics data may exist as
Expert judgements, experience/common sense, design standards, established design principles, graphic representations, quantitative data tables, mathematical functions and expressions
Define, explain, and list the possible causes for the categories of human error
- Operation error - attributed to operating personnel. Causes: Improper procedures, poor environment, task complexity, overload conditions, operator carelessness, inadequate personnel training or selection, and incorrect operating procedures
- Maintenance error - occur in the field and are attributable to maintenance personnel. Causes: Use the wrong grease to lubricate equipment, incorrect calibration of equipment, etc.
- Design error - reflect inadequate designs. Causes: Inadequate analysis of the system requirements, designer’s bias toward a specific design, insufficient time spent on the design
- Inspection error - the purpose of inspection is to uncover all items with defects, however, inspection effectiveness often averages around 85%
- Fabrication error - result from poor workmanship during product assembly. Causes: poor blueprints, inadequate illumination, poor workstation layout, excessive noise, etc.
- Installation error - attributed to incorrect or incomplete installation of the product. Causes: Failure to follow the instructions or blueprints
- Handling error - due to the inappropriate or improper storage or transport of a product, and can result in damage to the product. Causes: Improper packaging for shipment, etc.
- Contributory error - this classification covers those errors that are difficult to identify as either human or hardware related
This probably should have been multiple flash cards
Identify and define the three labels and warnings
- Caution - used under conditions where hazards or unsafe practices may lead to minor personal injury, and/or minor damage to the product or to property
- Danger - used where immediate hazards (if they occur) would lead to severe personal injury or death
- Warning - used where hazards or unsafe acts (if they occur) could lead to severe personal injury or death
Identify and define four manufacturing processes
- Machining - process of removing or separating pieces of material from a workpiece
- Forming - process of giving shape to a workpiece without adding material to, or removing material from, the workpiece
- Joining - process of fastening workpieces together, permanently or semi-permanently
- Finishing - process of modifying a workpiece surface for the purposes of protection and/or appearance
List a few guidelines for machining
Allow run-out for tool, avoid completely spherical surfaces, use through holes wherever possible, provide boss to avoid drilling an inclined surface, do not design very difficult or impossible to machine hollows or overhangs, design for reasonable internal pockets radii, use standard dimensions, avoid long narrow holes, avoid thin walls (often break), place holes away from edges, provide access for holes, design parts that are easy to hold, avoid deep pockets that require long tools and cause tool vibration, avoid long thin sections that cause vibration when machined, remember that holes cannot change directions, and avoid external rounds (difficult, use chamfers)
See slides for graphics
List a few guidelines for casting and molding
Avoid sharp corners, maintain uniform section thickness, stagger ribs to avoid hot spots, facilitate flow of molten material, provide draft angle to be able to remove part from mold, avoid abrupt changes in section thickness, design bosses with uniform thickness, avoid deep narrow ribs, design with mold flow considerations in mind, avoid staggered split lines, avoid using sliders to mold design, use uniform wall thickness, do not design sharp corners (stress concentrations) but don’t use too large of radii, keep section thickness uniform around bosses, attach bosses to wall with ribs, and keep rib thickness less than 60% of the part thickness to prevent voids and sinks (space out ribs)
See slides for graphics
List a few guidelines for sheet metal
Provide an ear in a blank or include hole as notch (narrow web will cause bulging), offset bends, a cut-out is needed to bend flange, use separated flanges when possible, avoid sharp internals and external corners
Define sustainability
The ability to sustain something for an indefinite period of time without depleting the resources used to sustain it, and such that it does not damage the surroundings in which it resides
Define two sustainable engineering design activities
- Product design - the resources used to make a product should not be depleted, and the disposal of the product should not damage the environment in which it operates
- Process design - the input resources processed should not be deleted, and the output materials should not damage the environment into which they go
Define product life cycle
The life cycle of a product from conception to disposal. Resources and waste are managed in a closed-loop cycle, with products being reused, recycled and remanufactured in an ideal product life cycle.
Define life cycle design
Life cycle design is an activity whereby the designer recognizes and takes into account the various phases of a product’s life cycle during its design. Objectives considered are generally transportation, usage, energy consumption, safety, recyclability, etc.
Define life cycle assessment (LCA)
The investigation and evaluation of the environmental impacts of a given product or service caused or necessitated by its existence. The purpose of LCA is to assess the full range of environmental and social impacts assignable to products or services, to be able to choose the one with the most beneficial outcome, or least impact
Where can LCA be used?
Help regulators/government to formulate legislation, assist manufacturers to analyze and improve their process or products, enable consumers to make informed choices
What are a few issues with LCA?
No “accepted standards” (conductor of the LCA may be biased). Due to this, the accuracy could be questioned and cannot compare LCAs conducted by two different parties. Because of this, LCA should be performed by the particular organization/individual for their own analysis
What are the four phases of LCA
- Goals and scope
- Life cycle inventory (data collection, modeling of system)
- Life cycle impact assessment (characterization, normalization, weighting)
- Interpretation
Define the “goals and scope” phase of LCA
- Define the goal of the project
- Determine what type of information is needed to inform the decision-makers
- Determine the required specificity
- Determine how the data should be organized and the results displayed
- Define the scope of the study
- Determine the ground rules for performing the work
Define the “life cycle inventory” phase of LCA
Data collection and modeling of system
Define the “life cycle impact assessment” phase of LCA
Characterization, normalization, and weighting
Define the “interpretation” phase of LCA
“What do all the numbers mean?”, consider a sensitivity/uncertainty analysis to validate your model against variations in results, ask yourself “has the goal and scope been met?”
Define energy/resource budget
Can be within the scope of an LCA. To create one, consider material usage and source, transportation, renewability, manufacturing, use of product, and disposal
