Design review (US Government) - Wikipedia

http://en.m.wikipedia.org/wiki/Design_review_(US_Government)#section_1

HideReview process

Design review is also required of medical device developers as part of a system of design controls described in the US Food and Drug Administration's governing regulations in 21CFR820. In 21CFR820.3(h), design review is described as " documented, comprehensive, systematic examination of the design to evaluate the adequacy of the design requirements, to evaluate the capability of the design to meet these requirements, and to identify problems." The FDA also specifies that a design review should include an independent reviewer.

Mission Concept Review (MCR)

The MCR affirms the mission need and examines the proposed mission's objectives and the concept for meeting those objectives.

System Requirements Review (SRR)

The SRR examines the functional and performance requirements defined for the system and the preliminary program or project plan and ensures that the requirements and the selected concept will satisfy the mission.

Mission Definition Review (MDR)

The MDR examines the proposed requirements, the mission architecture, and the flow down to all functional elements of the mission to ensure that the overall concept is complete, feasible, and consistent with available resources.

System Definition Review (SDR)

The SDR examines the proposed system architecture and design and the flow down to all functional elements of the system.

Preliminary Design Review (PDR)

The PDR demonstrates that the preliminary design meets all system requirements with acceptable risk and within the cost and schedule constraints and establishes the basis for proceeding with detailed design. It will show that the correct design options have been selected, interfaces have been identified, and verification methods have been described.^[2]

The following are typical objectives of a PDR:

• Ensure that all system requirements have been allocated, the requirements are complete, and the flowdown is adequate to verify system performance
• Show that the proposed design is expected to meet the functional and performance requirements
• Show sufficient maturity in the proposed design approach to proceed to final design
• Show that the design is verifiable and that the risks have been identified, characterized, and mitigated where appropriate

Critical Design Review (CDR)

The CDR demonstrates that the maturity of the design is appropriate to support proceeding with full-scale fabrication, assembly, integration, and test. CDR determines that the technical effort is on track to complete the flight and ground system development and mission operations, meeting mission performance requirements within the identified cost and schedule constraints.^[3]

The following are typical objectives of a CDR:

• Ensure that the "build-to" baseline contains detailed hardware and software specifications that can meet functional and performance requirements
• Ensure that the design has been satisfactorily audited by production, verification, operations, and other specialty engineering organizations
• Ensure that the production processes and controls are sufficient to proceed to the fabrication stage
• Establish that planned Quality Assurance (QA) activities will establish perceptive verification and screening processes for producing a quality product
• Verify that the final design fulfills the specifications established at PDR

Production Readiness Review (PRR)

A PRR is held for Flight System and Ground Support projects developing or acquiring multiple or similar systems greater than three or as determined by the project. The PRR determines the readiness of the system developers to efficiently produce the required number of systems. It ensures that the production plans; fabrication, assembly, and integration enabling products; and personnel are in place and ready to begin production.

Test Readiness Review (TRR)

A TRR ensures that the test article (hardware/software), test facility, support personnel, and test procedures are ready for testing and data acquisition, reduction, and control. This is not a prerequisite for KDP E.

System Acceptance Review (SAR)

The SAR verifies the completeness of the specific end products in relation to their expected maturity level and assesses compliance to stakeholder expectations. The SAR examines the system, its end products and documentation, and test data and analyses that support verification. It also ensures that the system has sufficient technical maturity to authorize its shipment to the designated operational facility or launch site.

Operational Readiness Review (ORR)

The ORR examines the actual system characteristics and the procedures used in the system or end product's operation and ensures that all system and support (flight and ground) hardware, software, personnel, procedures, and user documentation accurately reflect the deployed state of the system.

The following are typical objectives of an ORR:

• Establish that the system is ready to transition into an operational mode through examination of available ground and flight test results, analyses, and operational demonstrations
• Confirm that the system is operationally and logistically supported in a satisfactory manner considering all modes of operation and support (normal, contingency, and unplanned)
• Establish that operational documentation is complete and represents the system configuration and its planned modes of operation
• Establish that the training function is in place and has demonstrated capability to support all aspects of system maintenance, preparation, operation, and recovery.

Flight Readiness Review (FRR)

The FRR examines tests, demonstrations, analyses, and audits that determine the system's readiness for a safe and successful flight or launch and for subsequent flight operations. It also ensures that all flight and ground hardware, software, personnel, and procedures are operationally ready.

The following are typical objectives of a FRR:

• Receive certification that flight operations can safely proceed with acceptable risk.
• Confirm that the system and support elements are properly configured and ready for launch.
• Establish that all interfaces are compatible and function as expected.
• Establish that the system state supports a launch "go" decision based on go/no-go criteria.

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Aircon - Installation Materials

Copper Pipes

1/4 refer to pipe size, 22 SWG refer to the gauge, 15m is the length of the pipe

This is used to transfer the gas (Liquid form) from the outdoor to the indoor unit (blower units) and gas (Gas form) from the indoor to the outdoor.
This is the most important material for the installation as gas travels in it.
Copper pipe comes in different grades.
Lowest is SWG (Standard working guage) 24 or G (guage)24.
G24 refers to the thickness of the copper pipes. 
G23 is thicker then G24, G21 is the thickest among all.

Improper installation/handling of copper pipes may cause the following.
- Condensation of pipes at certain area. 
This will usually happen around the bend part. If the installer uses a proper tool known as the pipe bender to bend, the result will be a nicely bent pipe.
Gas flow will be smooth.
If they use their hand, it may have some acute angle. 
Gas might not flow smoothly and icing might occur, which will lead to condensation. Even with how thick a insulation, it will not stop the condensation. 

I will suggest HDB flat owners to use min G23.
For concealed pipings in condo/pte hse, you may want to upgrade to G22.



Insulation
This is the black rubber foam thing which is used to encase the copper piping.
During operation, the copper pipes are cold and some water droplets will form due to condensation.
The insulation will serve to absorb water droplets.
There are 2 classes of insulation. Class 0 and class 1.
The class refers to the fire rated properties of the insulation. In aircon, we are talking about absorbing water, so do you think its worth to pay for a upgrade from Class 1 to Class 0?

I will suggest to use 3/8 thickness insulation for piping in trunking.
For piping above false ceiling or concealed in wall, you may consider to upgrade to 1/2 thickness insulation.

Wire

3 Cord Wire

Wiring is used as a form of power supply for the aircon system and a form of communication between the indoor and the outdoor units.
For the wiring between the outdoor unit to the power point, usually 3C70 is used. For aircon system up to 36k btu capacity.
3C70 refers to 3 cord, (3 pieces of wire), one for live (brown), one for netural (blue), one for earth (green).
70 refers to the number of copper strand inside a single cord.
Between the indoor to the outdoor units, 3C40 is used.
Reason for a lower grade is because, the indoor unit does not consume a lot of amphere.
1 is for live power supply, another is netural power return. The 3rd is for communication purposes between the indoor and outdoor.


PVC pipe also known as drainage pipe
There are 2 sizes used in the market, 13mm and 16mm. It refers to the internal diameter of the pipe. 
16mm has a bigger diameter and might allow for better flow of drain water and prolong the time taken for the build up of jelly and cause the aircon to leak water.
Some companies also have the good practice of applying insulation 3/8 thickness to the horizontal Pvc pipes.
Vertical pipes do not need insulation as water will fall fast due to gravity.




Trunking

Trunking

This is the plastic casing that encase the copper, pvc pipes and wiring.
It is important that there are of the correct size as getting a size smaller will lead to the copper pipes insulation pressing against one another and increase the chances of condensation.




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Aircon - Copper Piping

For copper piping, the process of bending it is important.

Improper bending of pipe will increase chances of condensation or poor gas flow (not cold)

Improper bent piping

 Piping should not be bend with bare hands. It should be done using a pipe bender.

Pipe Bender

Pipe bend with proper tools, nice 90 degrees bend.

Aircon Copper Pipe Gauge sizes. G22 G23 etc

FYI for Aircon Copper Pipe Gauge sizes. G22 G23 etc

Here's a diagram explaining the aircon copper pipe gauge sizes.  =)

Took me some time to google this. Hope it'll help people doing new aircon.

Air Con Terms and Jargons 

Before I start, there are some technical terms or jargons used in air conditioning which u all should know a little beforehand.

BTU = British Thermal Units. This is a unit for cooling capacity. A higher value means higher cooling power. There are 9000btu(10000btu), 12000btu(13000btu), 15000btu(16000btu), 18000btu, 22000btu(20000btu), 24000btu(26000btu) and 30000btu.
* Some people like to use Hp to define the cooling capacity. Nothing wrong with that but try stick to BTU or kW as both use more commonly in Singapore.

Outdoor Unit = the big rectangular stuff u placed on air con ledge or mount on a stainless steel bracket. Some people call it 'compressor' but actually the compressor is part of the outdoor unit.

Indoor Unit or Fan Coil or FCU (fan coil unit) = this 'air con' inside your home.

Compressor = the main component for your air conditioner. It is mounted inside the outdoor unit.

Refrigerant = the working fluid for air con. There are R22 and R410A currently in use for residential. People always tends to say 'Gas'...Dun do that!!! Caused it is not always Gas...it is at times LIQUID..!
Use 'Refrigerant' instead.

Class 1 & Class O = Fire Propagation Test Standards for insulation. In simple terms, the insulation inability to burn.

Grade = Actually it should be Gauge. It is an industrial term to describe thickness of metal. In our case, thickness of the copper pipe. 'Grade 23' means 0.61mm thick.

Insulation = the foam or rubberly 'layer' covering the copper pipe. Its function is to prevent heat gain.

System 2 (or 3 or 4 or 5) = The figure means number of indoor units to 1 outdoor unit. For example, a System 4 will be 4 indoor units to 1 outdoor unit.

9+12+18 ( or any other number combinations ) = Using 9+12+18 as an example, it means a System 3 with one 9000btu indoor Unit, one 12000btu indoor Unit and one 18000btu indoor Unit.

Single Split = this also means System 1. Therefore it will have 1 indoor unit to 1 outdoor unit.

Non Inverter = the conventional air conditioner or 'fixed speed'.

Inverter = the more energy efficient and expensive air conditioner or 'variable speed'.

Manufacturer or Agent = the manufacturers like Daikin, Mitsubishi Electric, Panasonic, etc.

Dealer = the retailer or installer

**Learning this will not impress the salesman but at least u will not look 'blur blur'. **

Which air conditioner to buy? 

Ask yourself these questions first

1) Do you really need an air conditioner?
This should be the first question you should be asking yourself. Many new home owners probably feel that since they are renovating their new home, they might as well install the air conditioner together. But do you have a habit or tendency to use the air conditioner? If you are currently very satisfied with just a standing fan, why should you get an air conditioner?

2) Are you willing to pay the additional electrical cost of using the air conditioner?
Some home owners upon noticing the increase in their monthly electrical bills, decide to reduce or even stop using air conditioner all together.

If you have justified your need for an air conditioning system, u may began to select your air conditioner.

1) Which area of your home do you want to be air conditioned?
This will determine the system combination.
For example,
U want to air conditioned 3 bedrooms and the living. You are likely to either get a System 4 or a System 3 + Single Split.

2) Which brand of air conditioner do you prefer?
You can ask your friends and family for recommendation, look for reviews on the internet, read through the catalogue or visit a few retail shops.

3) What kind of features are most important to you?
Do you want the most energy efficient? Or do you prefer it to be the quietest in the market? Or you want your air conditioner to function as an air purifier? Or it must be 'Made in Japan'? Or you want to find an air conditioner design that will match your home deco? Or you just want an air conditioner?
Try to match your selected features to the available. After that, you will have to determine your TOP 3 models.

Now you can go 'shopping' for air conditioners.

1) Visit a few retail shops and listen to the salesperson's sales talk. Tell them that you are considering between these 3 models and request for their advice. You can also seek their advice on the system combination, inverter or non inverter, R410A or R22 and etc. You would probably prefer to keep this first visit to just selection of models.

2) When back home or having a break, determine which model you want. Decide and proceed for the return visit.

3) This time seek clarifications on prices, installation materials, installation procedures, after sales service, warranty and etc.

4) Finally decide which retail shop you are most comfortable with and make your sales confirmation. To be on the safe side, go through the details and have everything written clearly on the sales invoice.



Pointers when surveying retail shops 

When searching for retail shops to install your air con, please remember to ask the following

1) Price includes GST?

2) Price includes 2 times installations? First Installation for Piping only and Second Installation for Indoor Units / Outdoor Units. Some installers will install outdoor unit during first installation.

3) If u do need them to go to home to discuss with you and your contractor how the air con trunk will run, will there be additional cost?
( this is known as site survey or site view, it is done after the major hacking and before the first installation )

4) Make sure the retail shop uses BCA trained workers if you need a stainless steel bracket to support the outdoor unit outside your home. Request the installers to show u their certificate before installation.
** Though for those with air con ledge, it is not necessary. **

5) Go for 'Class 1' or 'Class O' PSB certified insulation though I would say it is not that important as the rating does not reflect the quality and insulation properties on the material.
Nevertheless get them to show u the sample. Ensure this will be use thru out the home and not half or part of it only.
Equally important is the thickness ranging from 1/4'', 3/8'', 1/2'' and 3/4'' (the usual thickness for residential) You have to ask them what thickness they are providing for the insulation. Using a thicker insulation also means better insulation properties but bigger trunk and higher cost.
** Insulation should have the brand, dimensions/thickness and 'Class Rating' printed on it. 

6) Go for 16mm diameter PVC water drainage pipe.
** I would recommend insulation (1/4'') for the drainage pipe also but as far as I know, most installers do not like to do that caused it is troublesome and will incur higher cost. Unless, u are willingly to pay.
** through out the home and not part of it. The smaller size will be 10/13mm.**

7) U should use the correct copper pipe diameter
( for the gas and liquid copper pipe ) according to the manufacturer's catalogue. Get the salesman to point out for you.

8) Copper pipe should be all brand new. The colour should be very shiny! If it looks dull means it has left lying around for sometime. But if you see that the 'dull' coil still has the 'coil' shaped, it will still acceptable as it means it has not been used before or partially used.

9) Copper pipe comes in coils of about 10m - 20m (usually 15m), depends on manufacturer. U should insist that they use one copper pipe when possible. This is to reduce the number of joints thus the chances of leakage of refrigerant. But you must understand that when the piping length is more than 15 meters, there will be joints.
**Nevertheless, brazing is a 'safe' method of joining copper pipes.

10) Copper pipe should be bended with a Level Type Hand Bender
(bending tool). This will give a smooth radius. It should not never be bend using bare hands.

11) The thickness of the copper pipe has always been an issue with most of the readers. The market goes something like R22 systems 0.56mm (24SWG), R410A systems 0.61mm (23SWG). U have to confirm with the retailer.
** I personally would prefer 0.71mm for R410A system but I do understand that with the ever increasing price of copper worldwide, this upgrade do not come cheap. Nevertheless, check with the manufacturer if you need any advice.

12) Insist that they do an Evacuation of the system (vacuum process) before they 'release' the refrigerant into the system. This is remove all the moisture in the copper piping. This is especially important in air-conditioners using R410A.
** Not doing this will not spoil your compressor immediately but it is one of the factors affecting the life span of compressor.

13) Check the installation warranty and what it covers like transportation and labour...terms and conditions like validity subjected to yearly service contracts etc

14) Check if they are having their own workers or sub contractors.
** There is no way to know but just ask. Or u can ask other shops about this shop. Basically everyone will say they are using their own workers. Nevertheless, it is always advisable to be there personally during the day of the installation.

15) Make sure it is unlimited piping length. As in no additional charges for installation using more than a certain length.

16) Lastly ask what might the case that u might have to pay additional during installation. If salesman, say no more, that get the salesman to make a note saying that there no more additional charges. If yes, get him to write down, what might be the situation u will have to pay additional.

**Remember whatever is promised to u by the salesman should be written down on the sales invoice.**

Five Ways to Improve Your Website

http://sg.finance.yahoo.com/news/Five-Ways-Improve-Your-entrepreneur-1151036451.html?x=0%22%3Ehttp://sg.finance.yahoo.com/news/Five-Ways-Improve-Your-entrepreneur-1151036451.html?x=0

Khoa Bui, On Friday 22 July 2011, 15:40 SGT

Have you ever visited a website and closed it within a few seconds? There are many reasons why people do this. A guest may want exit your website if it:

• Takes too long to load
• Doesn't look like it relates to what they're searching for
• Doesn't load correctly
• Is too cluttered
• Is too empty

As a small-business owner, why would you invest thousands of dollars in building a site if visitors just tune out?

Solving click-off is one of the biggest challenges I discovered while building thousands of websites for clients as a website designer. If a visitor comes to your website and leaves within eight seconds, you need to fix something. Here are five fast ways that I've used that dramatically minimize click-off by improving your website's performance, speed, search engine results and relevance for users.

1. Speed up your website.
When your site doesn't immediately grab visitors' attention and inspire them to take action, you're wasting leads who could have become long-term customers.

One culprit for visitors quickly leaving your site may be a slow-to-load home page, and one of the biggest contributors to a slow-loading website is large, high-resolution images. Large animated Flash files can also weigh down a site's loading time.

Related: Five Time-Saving Tips for Updating Web Content

To fix this issue, consider putting fewer images on your home page and no Flash at all. You can also ask your web designer or developer to optimize your current images by compressing them and lowering the resolution.
One easy way to test the speed of your website is to view it on a slow Internet connection. Don't have access to a slow connection? Search online for "website speed test" for free tools to test the speed of your site.

Another issue to consider is whether your web host is slowing you down. Before you pay for a host, research reputable companies known for fast, high-quality connections.

2. Bold keywords.
Search engines want to provide relevant results on websites with high-quality content. That makes it critical for you to provide the most relevant, high-quality information your target market will be searching for. One way to quickly connect visitors to that great information is to bold the most important keywords.

For example, if someone finds your site by searching "cycling in Perth," make sure your website has the keywords "cycling" and "Perth" in bold type. I'm not suggesting that you continually bold all your website keywords. Just bold one or two keywords close to the top of your web page.

3. Tag your graphics.
Another way to attract more traffic is to optimize your graphics so they become more visible to the search engines. Many entrepreneurs don't realize how much they can benefit from being listed in the Google Images database.

So how do people find you when they search for images? It's easy. When building your website, make sure your web designer includes the correct coding to hook your images with relevant keywords. Name your image files with relevant, descriptive words and include a title tag and an alt tag in your image code. These tags allow you to include more information and keywords related to your image. By including these elements, search engines will be able to understand the content of your images and it will make your site more accessible to visitors with visual disabilities.

Related: Making the Most of 'Contact Us' to Gather Leads

Make sure you don't keyword-stuff that code, though. Search engines will know you're trying to cheat the system, and you'll run the risk of becoming banned from their listings. Just describe the images in natural language without repeating words.

4. Update your website dates.
When your website has the current date, it's basically telling visitors that this website is up to date. It's fresh and current. Search engines know this and take it into consideration. After all, search engines want to provide the best possible results.

If you visit a website and scroll to the bottom and see "Copyright 2005," you might think that was the last time the site was updated. Outdated information makes the site look neglected and unprofessional.

5. Comply with online quality standards.
In a nutshell, W3C compliance is an online standard, or set of rules, that, when followed, ensures your website adheres to a strict quality standard. (W3C is short for the World Wide Web Consortium, the main international standards organization for the Web.) When you create your site according to these standards, it tells the world you care about quality and taking good care of your site.

Some of the coding differences can seem miniscule and tedious -- for example, remembering to include a slash at the end of a line of code -- but my own experience as a web designer showed me that when I make the extra effort to follow these standards, my site earns better rankings. If you are not building your own site, make sure that your web developer is applying W3C compliance to all of your website work.

Related: Five Things You Should Know About Web Analytics

 

This article originally posted on Entrepreneur.com

Tutorial - SPI interface

SPI Interface or Serial Peripheral Interface bus is as you might expect a serial interface meaning data is shifted out (and in) one bit at a time.


It is intended for transmission of data from a master device to/from one or more slave devices over short distances at high speeds (MHz).

It is simply based on an 8 bit shift register shifting data out on a single pin and shifting data in on another pin.

Note: some devices use more than 8 bits!



 
Its main use is to replace parallel interfaces so you don't have to route parallel buses around a pcb.  For example you can buy an SPI 12bit ADC and instead of 12 parallel wires to read the data you only need 4 SPI connections.  Actually you may only need three as you may not need to send data to the device!


 With the SPI interface you can communicate with a device transmitting and receiving 8 bits of data at the same time and it is suited to high speed streaming data transfers.

Note: The trade off between using a parallel interface and the SPI interface is speed e.g. if you read a parallel 12bit ADC at 200ksps then you could read the device at a 200kHz rate but if you want to get the same data rate using SPI then you need a serial speed of 200kHz x 12 = 2.4MHz.  So the actual trade off is speed and the consequential noise introduced into the circuit.


Unlike I²C there is no concept of transferring ownership of the bus i.e. changing bus master and there are no slave device addresses.  SPI is a much simpler protocol and because of this you can operate it at speeds greater than 10MHz (compared with the 3.4MHz maximum for I²C).

The best feature of SPI is that you can do full duplex data transfers (data in both directions at the same time) which you can not do with I²C and you can do it fast.

Note: The maximum rate for a PIC Micro using a 20MHz clock is 5MHz.

SPI Interface : Signals

SPI Interface Signals
PIC name	Master	Slave
SCK	Serial clock output from master [SCK]	Input to slave [SCK]
SDO	Serial data output from master [MOSI]	Input to slave [MOSI}
SDI	Serial data input from slave [MISO]	Output from slave [MISO]
SS	Optional slave (chip) select [SS]	Slave select [SS]

[] denotes SPI naming convention

Here is the setup for a single SPI device connection:

SPI Interface - single device

Note: The chip select signal SS is optional for a single device system as you could tie the SS input at the slave low if the other lines are dedicated to SPI use.

There are two ways to implement multiple slave operation:

• Use a separate chip select for each slave device.
• Wire all the slaves together DataOut to DataIn (daisy chain).

SIP Interface : Using chip selects

SPI Interface using separate chip selects

With this scheme you control each slave device using its chip select line (usually active low- red arrows show control lines).  When disabled the Data output from the slave goes into a high impedance state so it does not interfere with the currently selected slave and the data input is ignored (check datasheet).

The advantage of this scheme is that you can consider each device separately when you compare it with the daisy chain method.

SPI Interface : Daisy chaining

With this scheme all data sent by the master is shifted into all devices and all data sent from each device is shifted out to the next (shown by red dotted arrow).  For this scheme to work  you have to make sure that each slave uses the clock in the same way (see clock and data) and you have to get the right number of bits - so there is more work to do in software.

Compared to I²C these are very inelegant slave selection mechanisms and look like kludges to get round the fact that SPI was designed really as a simple single master to single slave protocol.  Having said that the above methods will work but for daisy chaining you will have to be careful of clock polarity and clock use as this is not defined in the SPI standard.

SPI Interface : Clock and Data

How a device reacts to clock input is undefined!!!

Data can be sampled at the rising or falling edge and data can be generated after the rising or falling edge!

This is why you can set the clock output from a master mode device in multiple ways just look at the diagram below - the first four signals are the four options you have to select the output clock.

SPI Interface PIC signals (extract from DS39582B)

You match the output clock to the clock that your device requires.

Note: This is why daisy chaining may not be a good idea (or you have to think very carefully about it!).

Note: For Master or Slave mode when using PICs you need to set the TRIS direction of the SCK pin appropriately.

Problems with the SPI interface

• The clock scheme may not be the same between devices.
• The data length can vary from device to device.

Advantages of the SPI interface 

• Very fast > 10Mhz.
• Simple protocol (easy to program in software if you have no SPI hardware module).
• Simple interface (no bidirectional pins c.f. I²C).
• Supports full duplex data streaming.

 
 
 
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Pan Tilt (possibility)

Compact Gimbal Mirror Mounts

STOCK# CCGM-1 CCGM-2
Optics Diameter: Ø mm( Inch ) 25.0(1”) 50.0(2”)
Optics Thickness: Min mm( Inch ) 3.0(0.12) 3.0(0.12)
Adjustable Axis θx , θy
Travel Range ( θx , θy) ± 4゜
Dive type 100 Pitch screw
Weight (kg) 0.16 0.25
Material (Treatment) Aluminum ( Black anodized )

Motor Control - What is Four Quadrant Control?

What is Four Quadrant Control?

Hardware: Motion Control

 
Problem: What are the four quadrants of operation of a motor drive? How does this apply to my motion control system?


Solution: To answer this question, we must understand a little about the purpose of servo motors and their function as an electromechanical conversion device. Servo motors are differentiated from other types of electric motors by the fact that they are typically designed with an emphasis on smooth, accurate position and/or velocity control, rather than ultimate power output. Servo systems are often bi-directional (CW or CCW), whereas many common industrial motor drives for pumps and fans and similar equipment only operate in one direction. Accurate control of acceleration and deceleration of a motor is another characteristic of servo systems, which is not always found in simple motor control systems. Many motors rely on the friction alone to decelerate the load when power is removed.

If we consider both directions of operation (CW and CCW) and both modes (acceleration and deceleration), we arrive at four distinct areas, or quadrants, of operation. This can be visualized by plotting the velocity of the motor on the X axis of a graph and the direction of applied torque on the Y axis as shown below. Quadrants 1 and 3 represent the motor applying torque in the direction of motion, while quadrants 2 and 4 represent applying torque opposite the direction of the motion. In quadrants 1 and 3 the flow of energy is from electrical to mechanical. The servo motor is converting electrical power from the drive into motion in the system. In quadrants 2 and 4, the motor is actually acting as a generator. The motion of the system is being converted into electrical power, which is then absorbed by the drive.

Some motor drives are capable of operating in only quadrant 1, while others will work in quadrants 1 and 3, quadrants 1 and 4, etc. Since most servo drives are designed for accurate control in both directions, many will operate, at least transiently, in all for quadrants. To do this the drive must be able to both source and sink electrical power from the motor.





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