ME 521 Computer Aided Design. 3. CAD Input Devices

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3. CAD Input Devices

Yrd.Doç.Dr. Ahmet Zafer Şenalp

e‐mail: [email protected]

Makine Mühendisliği Bölümü

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Computer System

Mainframe Computer and Graphics Terminals

Powerful

Inconvenient

High cost

Turn‐key CAD System

Dedicated computer systems for CAD applications, consisting of a super‐

mini computer and several design work stations.

Following the "central control concept"

Inconvenient and not powerful enough for complex 3D modeling.

Workstations & High‐End Personal Computers

Supporting multiple tasks

Supporting network and file‐sharing – convenient

Low costs

Present and trend

Dr. Ahmet Zafer Şenalp

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Graphical Input

Alpha Numeric Input

Graphical Output

Alpha Numeric Output

Computer

(CAD Workstation, Computer Terminal,

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¾Keyboard ¾Tablet/digitizer ¾Mouse ¾Trackball ¾Light pen ¾Touchpad ¾Touchscreen ¾Kontrol dials or knobs ¾Function switches ¾Joystick ¾Voice input ¾3D Data Acquisition Systems

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computer applications. They are typically employed to create & edit programs or to perform word processing functions.

A typical keyboard is shown in the above figure. It is divided into four different areas • The first area " (A) " is for normal typewriting when entering text strings.

• The second one " (B) " is the function key area for simplified handling of common operations.

• The third area " (C) " is composed by seperate cursor and control keys. This area presents several different configurations depending on the supplier of the keyboard, including arrows, thumbwheels etc

• The fourth area " (D) " is the numeric keyboard for fast numerical digit input.

Working principals of keyboards are simple. A keyboard has typically two registers whose contents can be read by the computer, one to set a status bit when a key has been struck the other to identify the key by its character code.The value of the status bit is monitored in a continuous repetitive manner. When the user hits a key, the status bit is set and application program is consequently interrupted to clear the status bit,

followed by reading the corresponding code of the key character. The loop is repeated every time the user strikes a key.

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the way one draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures. It can also be used to trace an image from a piece of paper which is taped or otherwise secured to the surface. Capturing data in this way, either by tracing or entering the corners of linear poly‐lines or shapes is called digitizing.

A graphics tablet (also called pen pad or digitizer) consists of a flat surface upon which the user may "draw" or trace an image using an attached stylus, a pen‐like drawing apparatus. The image generally does not appear on the tablet itself but, rather, is displayed on the computer

monitor. Some tablets however, come as a functioning secondary computer screen that you can interact with directly using the stylus.

Some tablets are intended as a general replacement for a mouse as the primary pointing and navigation device for desktop computers.

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Some of them use magnetic field to determine x,y coordinates. Some of them use strain wave. Acoustic tablets use acoustic methods. Microphones are placed in x,y,z axis. Pointer will point to the end of a certain frequency ranges. Microphones recieve this sound and x,y,z coordinates are determined according to recieving and formation time of sound. 2 and 3 D applications are avalibale. Acoustic 3D tablet

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In computing, a mouse is a pointing device that functions by detecting two‐dimensional motion relative to its

supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons. It sometimes features other elements, such as "wheels", which allow the user to perform various

system‐dependent operations, or extra buttons or features that can add more control or dimensional input. The

mouse's motion typically translates into the motion of a

cursor on a display, which allows for fine control of a

graphical user interface.

First mousse of the world (1952)

The first computer mouse,

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Operating an opto-mechanical mouse: 1. moving the mouse turns the ball.

2. X and Y rollers grip the ball and transfer movement 3. Optical encoding disks include light holes.

4. Infrared LEDs shine through the disks.

5. Sensors gather light pulses to convert to X and Y vectors.

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Cable Mouse In early times of computers mouse work by connecting to serial port. Recently this connection is adopted to PS/2 port. Today, most cable mouse connects to the USB port of a computer mouse. In addition, by means of various adapters, USB ports can be converted to PS / 2 or vice versa. Cordless Mouse ¾ Infrared mouse: This mouse uses an infrared communication with the computer. System is connected to computer’s serial, PS/2 or USB port, and mouse connects to the system by means of infrared rays. If an object is present between the mouse and the system mouse movements won’t be detected. Today this type of mouse is no longer available in the market. ¾ Radio wave mouse: Different from infrared mouse this mouse use radio wave signals for communication. Coverage areas is generally measured in tens of meters. ¾ Bluetooth mouse: This mouse use Bluetooth cordless technology for communication. Has advantages compared to above two types: Can be used wiyh every device as uses a standard protocol (PC, Apple and even Pocket PC)

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Types according to motion detection methods: ¾ Mechanical mice

Mechanical mice detects motion by means of a ball which can rotate by the mouse movement. This ball is coated by rubber and inside core is metal. As dust can cover the movement ball by passing time maintenance should be performed.

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¾ LEDed Optical Mice

These types of mice enable motion by reflection of the LED emitted. Top version models has 1000‐2000 dpi resolution.

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¾ Laser Optical Mice

These types of mice enable motion by light emitted by laser light source. Bu tür Appropriate choice for those desire high resolution. Resolution can be 3000 dpi and more. If mice are categorized according to motion detection, most expensive is the laser optical mouse.

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consists of an “upside‐down” mouse, in which the ball on the bottom of the mouse has been turned up to the top. As the ball is rolled by the hand of user it moves and the cursor on the screen. It controls the position of the cursor on the screen with the direction of rotation controlling the direction of cursor movement and the distance the cursor travels controlled by the number of revolutions of the ball. Also some functional buttons can be added to the trackball similar to mouse. 9 In CAD applications large balled models are preferred for better precision. Before the invention of touchpad the usage of trackball was common in laptop computers. 9 With the end of 1990’s with the invention of scroll wheel that is used in mice the usage of trackball is decreased. 9 Still used in cartography and similar applications.

The world's first trackball

invented by Tom Cranston,(1952)

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¾A Lightpen is an input device which allows interaction with a display from a computer screen.

The lightpens can be used to input data as well as to draw as shown in the figure. The idea behind the lightpen is the familiarity of an ordinary writing. It is a direct and natural form of input.

¾A light pen can work with any CRT‐based display, but not with LCD screens.

¾A light pen is fairly simple to implement. A light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gunrefreshes that spot. By noting exactly where the scanning has reached at that

moment, the X,Y position of the pen can be resolved.

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First Light pen

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A touchpad (also trackpad) is a pointing device consisting of specialized surface that can translate the motion and position of a user's fingers to a relative position on screen. They are a common feature of laptop computers and also used as a substitute for a computer mouse where desk space is scarce. Touchpads vary in size but are rarely made larger than 40 square centimeters

Touch pads consist of single plastic mylar membrane silkscreened with a silver

conductive grid and two resistive strips and works in a similar way with touch screens except the fact that it works on a flat

pad. When a key is pressed, two electrical resistances are reflected between a common line and the x and y output lines.

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¾ The touch screen, namely touch‐sensitive‐screen, works by direct user‐interaction with the CRT. A screen overlay is capable of sensing the physical contact of the

operator's fingers or any other stylus on the screen.

¾ The screen overlay consists of transparent plates that fit over the screen and can convert the touch of the user, by optical, electrical or acoustical methods, into digital information consisting of several screen coordinates.

¾ The touch sensitive screen is utilised mainly to choose one out of a set of options presented in the panel. Just like on ATM machines, in industrial process control

applications.

¾ It can also be used for drawing some shapes on the screen but since its accuracy is not great compared to other input devices not used for this purpose much.

Disadvantages:

± Extended use causes tired arms, ± Smudges on screen,

± Insufficient accuracy for CAD applications based on pixel by pixel drawing.

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The dials, which are used as valuators, are graphical devices adequate to input scalar values to application programs. They are rotary potentiometers grouped in special

assemblies most commonly used to control rotation or linear movements of objects

displayed on a screen. When the user moves the dial, the voltage being output is changed. The translation from voltage to digital information is made by analog‐to‐digital converters. The dials can be programmed to input values into the graphics program. Beside this some dials have a user‐programmable label. The label can indicate the function of the dial. As the functions of the dials change in the program the labels can be changed interactively so the functions of the dials are always clear.

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Buttons and function switches are either toggle or push‐button switches. They may be either continuously closed, continuously open, or momentary‐contact switches. The most common convenient type of function switch incorporates both capabilities. Software controlled lights indicating which switches or buttons are active are usually provided.

Buttons and switches are frequently incorporated into other devices. Switches make the on/off settings for input or mode of operations.

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Clasical Joystick: Literally only 1 or 2 button + direction, functions as a control tool

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Input output functions: In old times control devices only reflect the choice of the player to the game but by improving technology joysticks are changed and joysticks that response to sense are developed. These respond according to the movement they sense and generally vibration property is presented by game devices such as PlayStation (dual shock) Example: A crash in a car race is responded by the vibration of the joystick. Second generation joysticks have more than two buttons and have perfect ergonomic structure, the routing function is analog and detects all kinds of precise orientation and most important is that it is a control device with input output function. analog controlled nintendo; first 64 then game cube applied

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The best example to the last generation joysticks: Nintendo wii control device ¾ Cordless control ¾ Input output function ¾ Sensing function: Sensing function enables the player’s the movements to be sensed and converted to the game. Example: In a tennis play the movement of player’s hand is simulated as a movement of tennis racket

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A voice entry system (VDE) consists of a microphone attached to a speech recognition device, which in turn transmits voice command information to a

computer. As it can be understood from its name VDE working principal is data entry through voice commands. When user sounds a command, the command is

interpreted according to a preprogrammed definition of its meaning.

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2D Image: (for each pixel: X and Y coordinates and light intensity).

The intensity could be gray (8 bits: 0 – 255) or color RGB (24 bits).

3D Range Image/Data from Range Sensing Devices and 3D Camera –

data points defined by their x, y, z coordinates (cloud point data).

• Mechanical probe (measurement and scanning)

• Laser scanning

¾ Triangulation‐based range sensing devices ¾ Time‐of‐flight based range sensing devices

Machine vision based CAD model generation for:

• reverse engineering

• machine vision and intelligent robot

• vehicle size measurement and traffic monitoring

• scanning of 3D object, human body, and art work

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Scanning of Clay Model to Obtain Surface Data

Design Details Using CAD System Dr. Ahmet Zafer Şenalp

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ME 521 Computer Aided Design. 3. CAD Input Devices

3. CAD Input Devices

Yrd.Doç.Dr. Ahmet Zafer Şenalp

Makine Mühendisliği Bölümü

Computer System

Mainframe Computer and Graphics Terminals

 Powerful

 Inconvenient

 High cost

Turn‐key CAD System

 Dedicated computer systems for CAD applications, consisting of a super‐

mini computer and several design work stations.

 Following the "central control concept"

 Inconvenient and not powerful enough for complex 3D modeling.

Workstations & High‐End Personal Computers

 Supporting multiple tasks

 Supporting network and file‐sharing – convenient

 Low costs

 Present and trend

 2D Image: (for each pixel: X and Y coordinates and light intensity).

The intensity could be gray (8 bits: 0 – 255) or color RGB (24 bits).

 3D Range Image/Data from Range Sensing Devices and 3D Camera –

data points defined by their x, y, z coordinates (cloud point data).

• Mechanical probe (measurement and scanning)

• Laser scanning

 Machine vision based CAD model generation for:

• reverse engineering

• machine vision and intelligent robot

• vehicle size measurement and traffic monitoring

• scanning of 3D object, human body, and art work

• 3D Range Sensors (3D Cameras): 3D Cloud Data Points

– Triangulation‐based: visible laser light,

short range, accurate

– Time‐of‐flight‐based: laser light & micro wave, long range, less accurate

• Processing of 3D Range Data

– 3D Cloud Data Points

Cross‐section‐based CAD Model

– Generation of a Complete Description for Objects and Workspace –

Sensor Fusion

• Forming a Surface Model and Carrying out Reverse Engineering

– Cross‐section ‐based CAD Model

Surface Model

CNC Machining;

RP; etc.

Implemented at BC Ferries Terminal

• Real‐time Vehicle Dimension Measurement

• Complex Vehicle Shapes

• Dimensions Measured at Speeds up to 120 km/hr

• Adverse Weather Conditions

• Height and Width Accuracy: 15 cm

• Length Accuracy: 30 cm

Geometric Modeling Based on 3D Scanning

• Challenges:

– Accuracy/Lighting/Range (Selecting Right 3D Sensing Tech)

– Occlusion (Obstruction)/Multiple View Fusion

– Multiple Level Modeling: Cloud Data Points/Crosssections/

Surfaces/Solid

• Applications:

– Reverse Engineering (e.g. Face Mask)

– Size Measurement (e.g. Moving Vehicle)

– Object Recognition (e.g. Moving Vehicle)

– 3D Log CAD Model Generation

– 3D Sculpture Documentation

– Shoe Making

– Character Modeling in Movies/Computer Games