Question 1

(a) The House of Quality functions as a living document and a source of ready reference for related products and future upgrades. While it is a great communication tool at each step in the process, the matrices are the means and not the end. Its purpose is to serve as a vehicle for dialogue to strengthen vertical and horizontal communications.

Through customer needs and competitive analysis, the House of Quality helps to identify the critical technical components that require change. Issues are addressed that may never have surfaced before. These critical issues are then driven through the other matrices to identify the critical parts, manufacturing operations, and quality control measures needed to produce a product that fulfils both customer needs and producer needs within a shorter period of development cycle time.

The net effect of all of this is that the items that drive the company’s action are driven by the customer’s requirements. There is an increase in focus on the customer and an increased awareness of their wants. Because of this focus, the process leads to improved customer understanding and the ultimate outcome- a satisfied customer.

The general format of the House of Quality consists of six components:

- Customer requirements (HOWs) listing the requirements derived from customer statements.
- Technical requirements (WHATs) comprising relevant and measurable product characteristics.
- Planning matrix illustrating customer perceptions observed in market surveys.
- Interrelationship matrix illustrating the QFD team’s perceptions of interrelationships between technical and customer requirements.
- Technical correlation (Roof) matrix identifying where technical requirements support or impede each other in the product design.
- Technical priorities, benchmarks and targets recording priorities assigned to technical requirements by the matrix, measures of technical performance achieved by competitive products and the degree of difficulty involved in developing each requirement.

b)

Total number of faults = Tack Switches + Motor Driver + Transducer +
Dip Switches + Ram + LCD driver +LED Array + EEPROM +Microcontroller
= 44 + 36 + 19 +16 + 7 + 7 + 2 + 1 =135

To reduce the failure rate by at least 80%,

Hence the engineer should focus on rectifying the Tack Switches, follow by Motor Driver, next will be Transducer, and lastly Dip Switches issues (85.2%).

c)

Sony Playstation 3 Microsoft Xbox 360
Functionality - graphics RSX (Reality Synthesizer)
256 MB Video memory Custom ATI Processor
512 MB UMA (Shared with GPU) Video memory
Functionality - game selection PS3 has less exclusive quality games and also poorer multiplatform game XBOX 360 has more exclusive quality games and also better multiplatform game
Functionality - Live 802.11B/G WI-FI, Bluetooth 2.0 802.11/A/B/G WI-FI ready, adapter not included
Product image Glossy black colour White colour with the ability of changing the Faceplate
Cost (basic 20GB models) US$485 US$275
Environment compatibility built-in (blu-ray) HD-DVD as add-on Regardless of comparing playback image quality, sound quality, and interface, there is one thing that gives the XBOX 360 an automatic “zero” in every category - it is the sickening screech of the 360’s DVD drive and fans, excruciatingly LOUD

With reference from http://www.hardcoreware.net/reviews/review-348-1.htm http://www.audioholics.com/buying-guides/how-to-shop/playstation-3-vs-xbox-360 http://www.winsupersite.com/showcase/xbox360_ps3_wii.asp Sony Playstation 3 Microsoft Xbox 360
Functionality 6 9
Product image 8 7
Cost 5 8
Environment compatibility 8 5
Total 28 29

Legend: 10 – Best, 5 – Ok, 0 – Poor

Overall the XBOX 360 has the upperhand and also the recommended choice.

Question 2

a) Physical product specification-
Material: Overmold body casing with a polymeric material
Colours: Black, blue and grey
Surface finish: matt
Dimension (H×W×D): 193.8mm×92.2mm×58.0mm
Weight: 400g without batteries, 450g with batteries Min Operating temperature: -10°C Max Operating temperature: 55°C
Relative Humidity: Full accuracy to 80% RH for temperature up to 30°C, decreasing linearly to 50% RH at 55°C
Shock and vibration: Tested to IEC/EN 60068-2

Environment:

The design attributes for environment can be separated into different factors, Physical user attributes, Transportation and storage, User abuse and Contamination.

Physical User Attributes
1. Aesthetic Design
Includes the positioning and size of user interfaces that governing the overall commercial appearance and ergonomics.
2. Cosmetic Finish
Finishes which makes the product attractive as well as durable.

3. Product Labeling
For the purpose of safety warning, product identification, labels and legends for user interface, calibration and inspection information.

4. Dimensions and weight
Constraints by the physical environment or requirements for portable products.

Climate:

The handheld digital multimeter is mainly for indoor and outdoor world wide over a wide range of weather conditions for both low temperature( around -10°C) and high temperature (50°C) regions. It must also be capable to withstand the humidity levels to maintain precise reading measurement and also preventing moist from damaging the internal components.

Reliability:

Reliability consideration is an essential part of the design and specification of a product. A successful product must not only be able to perform all the functions it is desired but must also be capable of staying in working condition as long as it is required according to its designed life span. The reasons for the essentiality of reliability are as follows:

• Failure of a product may endanger lives, damage property or cause great economic looses.
• Faulty products will bring inconvenience and economic looses to the customers.
• It will cost the manufacturer much more to repair or replace faulty products after their distribution compare to being able to rectify the fault or reject the product at the early stage of design and development.
• Customers will lose confidence on the product, the reputation of the company will be tarnished and business will be adversely affected.

b)

ii)
Compressor - One compressor is used to cool the heat exchanger of another compressor. This allows the second compressor to take the chamber to a lower temperature.

Fan - The fan is to provide a vertical-down recirculation to ensure that the air, and hence the temperature and humidity is evenly distributed in the chamber.

Alpha-numeric input console - A LCD display screen and an alpha-numeric key pad for the user to key in the settings such as temperature, humidity, number of cycles and cycle time.

Humidity - The humidity of the chamber is controlled by adding or removing water vapor. The chamber controller regulates the amount of steam from the boiler that is allowed into the chamber. Adding steam increases the humidity level in the chamber.

Temperature sensor – The temperature sensor measures the temperature in the chamber and feedback the data to the controller for control

Heater and Cooler unit - The heater comprises a heating element to provide high temperature and and cooler unit provide cooling for the chamber, in the operating range of -20°C to 100°C.

Humidity sensor - The humidity sensor measures the humidity in the chamber and feedback the data to the controller for control.

Question 3

a) (i) Sinusoidal Test

This is the simplest vibration test which simulates the transportation or mission profile experienced by a product under steady conditions. Examples of such vibration include instruments working on a rattling vehicle or aircraft traveling at cruising speed.
Industrial vibration testers are implemented with either electromagnetic or hydraulic mechanism. The latter is for vibration with larger g-force requirement. An industrial electrodynamics vibration system comprises an amplifier, vibration control system, as well as slip tables, head expanders, fixturing. The vibration factors such as displacement, velocity, acceleration, and force are programmed and controlled to create a sinusoidal vibration profile V=Asin(wt) for testing.

A vibrating platform is, in effect, a very powerful low frequency electromagnet with a moving core. The same principle as a loud speaker but without the sound amplifying cone. Below shows a sketch of the principle of a vibrating platform.

The controller produces a lower power signal at the desired vibration frequency, ω which is amplified by the drive amplifier to produce a voltage input to the vibrator. This input signal, Asinωt causes the vibrator to oscillate up and down frequency ω and with the amplitude a. The maximum acceleration of the platform is then , usually expressed in units of g, where 1g is the earth’s gravitational acceleration, . The controller will normally allow the frequency of vibration to be varied in a programmable way. The most common way of sinusoidal vibrating a product is to sweep the frequency across a test range of defined amplitude profile.

with reference from http://books.google.com.sg/books?id=8YCp5IGqQX0C&pg=PT121&lpg=PT121&dq=What+is+a+resonance+search+test&source=web&ots=ovpcuM3zD_&sig=47Ujyop-yyfGQJOifs2I2gFd0IQ&hl=en#PPT121,M1 (ii) Resonance Search Test

In resonance search test the equipment is vibrated whilst monitoring the vibration on its surface or on one of its internal components. The monitoring is achieved using an accelerometer which produces an output voltage proportional to the vibration level applied to it. The below sketch shows a typical arrangement and resulting frequency response.

A resonance search test will identify the frequencies at which the product absorbs the vibration energy. Such frequencies are bad for the product because the absorbed energy is internally dissipated in the form of vibration of parts relative to each other. Such relative movement can cause fractures and wear leading to longer term failures. A good illustration of the effect of resonance is that of a mounted printed circuit board as illustrated below.

The surface mount integrated circuit shown in the centre of the board will be subjected to significant forces as the board vibrates. At resonance the vibration will result in the largest deviation of the board and could, in extreme cases, cause cracking of the integrated circuit.

with reference from http://books.google.com.sg/books?id=8YCp5IGqQX0C&pg=PT121&lpg=PT121&dq=What+is+a+resonance+search+test&source=web&ots=ovpcuM3zD_&sig=47Ujyop-yyfGQJOifs2I2gFd0IQ&hl=en#PPT121,M1 (iii) Random Test

The alternative approach to sinusoidal vibration where each individual frequency within a given range is excited separately is random vibration. In random vibration the signal fed to the drive amplifier of the vibration platform is a shaped noise signal. As such it contains every component of frequency within a given range, each with constant peak amplitude. Shaping can be achieved using filters where necessary, to achieve a particular frequency spectral shape.

CSSM undergoing random vibration testing at Associated Test Labs

with reference from http://books.google.com.sg/books?id=8YCp5IGqQX0C&pg=PT121&lpg=PT121&dq=What+is+a+resonance+search+test&source=web&ots=ovpcuM3zD_&sig=47Ujyop-yyfGQJOifs2I2gFd0IQ&hl=en#PPT121,M1 (iv) Bump Test

Bump testing as another method of simulating the physical environment that is experienced during product transportation. Bump is the name given to the forces experienced by a product as it is bounced on a hard surface. To illustrate bump consider what a box would do if it was placed in the back of a hard floored lorry as it was driven along an unmade road. The box would bounce up and down in sympathy with lorry movement. Some bumps would be small, corresponding to small holes in the road, whereas others would be large bumps corresponding to larger holes.
A bump is characterised by its amplitude, duration and shape as illustrated in the below figure. The typical range of peak bump amplitude is 40g with common test values of 1, 5, 10, 25 and 40g. A typical duration is of the order of less than 10ms. A practical bump test might consist of subjecting the product to 4000 bumps of a given amplitude and shape in quick succession.

with reference from http://books.google.com.sg/books?id=8YCp5IGqQX0C&pg=PT121&lpg=PT121&dq=What+is+a+resonance+search+test&source=web&ots=ovpcuM3zD_&sig=47Ujyop-yyfGQJOifs2I2gFd0IQ&hl=en#PPT121,M1 (v) Shock and Drop Test

Products in normal use are regularly subjected to physical shock. A shock is experienced whenever something is knocked over or drops onto the floor. The g force experienced under such conditions can be very high and cause parts to break off or internal parts to break loose. A common test is to drop the product onto a hard surface from a height of one metre. For example the specification for a commercial bar –code reader was that it should survive being dropped from a height of one metre three times on each of its six faces (it being roughly rectangular in shape). The physical appearance was allowed to change and certain parts were allowed to break or break-off. The product was required to correctly read and decode bar-codes after all the drops. When designing or specifying a drop test it is particularly important to define accurately what constitutes a failure before the test is started.

Drop, Shock testing equipment

b)

i) Acceleration required is 9.81 m/s2

Mass = 600grams = 0.6kg
External acceleration = 15g = 15(9.81) = 147.15 m/s
Force = mass x acceleration
External force = 0.6(147.15) = 88.29N

ii) iii) v = u + at = 0 + (9.81)(0.495) = 4.85595 m/s

Mechanical energy dissipated = kinetic energy converted
= 1/2mv2
= ½ ×0.600×(4.85595) 2
= 7.074 J

iv) Kinetic energy

v)
The Model PDT-56 is Lansmont's entry level Precision Drop Tester. The PDT-56 consists of a drop leaf assembly housed in a cast aluminum structure that supports the precision guides and the pneumatic cylinder. This support structure is mounted on a 3 inch (76 mm) diameter chrome-plated steel column that is rigidly fixed to the ½ inch (13mm) thick steel base plate with a heavy-duty collar.
The weight of the drop tester is counterbalanced, changing drop heights is easy; simply remove the lock pin on the rear of the machine, move the assembly up or down as required, and reinsert the pin. The steel column is pre-drilled to give 1 inch (25mm) drop height increments up to 36 inches (914 mm) and 6 inch (152 mm) increments up to 72 inches (1829 mm).
Positioning: Manual height positioning with guide rod locking pin. Weight of the unit is counter balanced for easy height positioning.
Controls: Foot switch operation.
Capacity: 175LBPS. (79Kg)
Features: High-velocity pneumatic cylinder and unique brake system allow extremely accurate flat drop testing that exceeds industry standards.
The drop test is initiated through the use of a foot switch, allowing safe, efficient cycling of the Precision Drop Tester. The On / Off switch and power indicator lamp are located on the side of the drop leaf housing, easily accessible to the operator. with reference from http://www.lansmont.com/testequipment/Drop/PDT56.htm Question 4

a) Reliability consideration is an essential part of the design and specification of a product. A successful product must not only be able to perform all the functions it is desired but must also be capable of staying in working condition as long as it is required according to its designed life span. The reasons for the essentiality of reliability are as follows:
 Failure of a product may endanger lives, damage property or cause great economic losses.
 Faulty products will bring inconvenience and economic losses to the customers.
 It will cost the manufacturer much more to repair or replace faulty products after their distribution compare to being able to rectify the fault or reject the product at the early stage of design and development.
 Customers will lose confidence on the product, the reputation of the company will be tarnished and the business will be adversely affected.

b)
Failure rate of failures per hour
Flight from Singapore to London is 12.5hrs

ii)

Hence the single system has a lower reliability compared to the duplicate system.

c)

i)

Fault tree analysis

ii)

Probability that the Graphics Card overheating = 1 – (1-0.0007) (1- 0.002) (1-0.15) = 0.15229381

Question 5

a) i) Electromagnetic interference ( or EMI also known as radio frequency interference or RFI) is a usually undesirable disturbance that affects an electrical circuit due to electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit. The source may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit. The source may be any object, artificial or natural, that carries rapidly changing electrical currents, such as an electrical circuit, the Sun or the Northern Lights.
EMI can be induced intentionally for radio jamming, as in some forms of electronic warfare, or unintentionally, as a result of spurious and responses, intermodulation products, and the like. It frequently affects the reception of AM radio in urban areas. It can also affect cell phone, FM radio and television reception, although to a lesser extent. Electromagnetic compatibility (EMC) is the branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy with reference to the unwanted effects (Electromagnetic Interference, or EMI) that such energy may induce. The goal of EMC is the correct operation, in the same electromagnetic environment, of different equipment which use electromagnetic phenomena, and the avoidance of any interference effects.
In order to achieve this, EMC pursues two different kinds of issues. Emission issues are related to the unwanted generation of electromagnetic energy, and to the countermeasures which should be taken in order to reduce such generation and to avoid the escape of any remaining energies into the external environment. Susceptibility or immunity issues, in contrast, refer to the correct operation of electrical equipment in the presence of unplanned electromagnetic disturbances.
Interference, or noise, mitigation and hence electromagnetic compatibility is achieved by addressing both emission and susceptibility issues, i.e., quieting the sources of interference, making the coupling path between source and victim less efficient, and making the potential victim systems less vulnerable. with reference from http://en.wikipedia.org/wiki/Electromagnetic_interference http://en.wikipedia.org/wiki/Electromagnetic_compatibility

ii) The interference bandwidth of EMI is between 133MHz and 500MHz

The two possible sources of EMI are electrostatic discharge and conducted emission generated in electronic systems.

b) Failure Mode and Effects Analysis (FMEA) is performed through the following seven steps:
1. Define boundaries and detailed requirements of the system or product.
2. List all components / subsystems associated with the system / product.
3. Identify all possible failure modes of each component and related information.
4. Assign failure rate / probability to each component failure mode.
5. Determine each failure mode’s effects on surrounding parts / subsystems / plant / humans.
6. Enter remarks for each identified failure mode.
7. Review each crucial failure mode and initiate appropriate measures.

The usefulness of FMEA are:
• Help identifying weak spots in design.
• Ensure the understanding of all possible failure modes and their anticipated effects.
• Help to choose design alternatives during the early stages of design.
• Serve as a basis for design improvement actions.
• Establish corrective action priorities.
• Recommending test programs.
• Providing assistance in troubleshooting of operational problems in existing systems. Example of a FMEA Document for evaluating Electronic Receiver Card

c) i) Yield at board assembly: min(y1, y2) = min(0.99, 0.80) = 0.80 Yield at board functional test: yb x y3 x y4 = 0.80 x 0.90 x 0.95 = 0.684 Yield at system assembly: min(0.684, 0.85) = 0.684 Yield at system functional test: yf x y6 = 0.684 x 0.95 = 0.6498 (64.98%)

ii) Yield at board assembly: min(0.99, 0.95) = 0.95
Yield at board functional test: 0.95 x 0.90 x 0.95 = 0.81225
Yield at system assembly: min(0.81225, 0.85) = 0.81225
Yield at system functional test: 0.81225 x 0.95 = 0.77163 (77.16%)

(iii)

Procure quality components from reliable made or sources.