الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 137 |  |  |
| | | from | 137 | | |
Abstract
Microelectromechanical systems (MEMS) are very small integrated devices and/or systems that combine electrical and mechanical components. They range in size from the sub micrometer (or sub micron) level to the millimeter level, and there can be any number, from a few to millions, in a particular system. MEMS extend the fabrication techniques developed for the integrated circuit industry to add mechanical elements such as beams, gears, diaphragms, and springs to devices.
MEMS accelerometers are being incorporated into more and more personal electronic devices such as media players and gaming devices. In particular, more and more smartphones (such as Apple’s iPhone) are incorporating accelerometers for step counters, user interface control, and switching between portrait and landscape modes. They use accelerometers as a tilt sensor for tagging the orientation to photos taken with the built-in camera. Camcorders use accelerometers for image stabilization. Still cameras use accelerometers for anti-blur capturing.
Accelerometers are also being used in new contactless game controller or mouse. IBM and Apple have recently started using accelerometers in their laptops to protect hard drives from damage. If you accidentally DROP the laptop, the accelerometer detects the sudden freefall, and switches the hard drive off so the heads don’t crash on the platters.
In a similar fashion, high g accelerometers are the industry standard way of detecting car crashes and deploying airbags at just the right time. They are used to detect the rapid negative acceleration of the vehicle to determine when a collision has occurred. They also have a built-in self-test feature, where a micro-actuator will simulate the effect of deceleration and allow checking the integrity of the system every time you start up the engine. Recently the gyroscopes (they rely on a mechanical structure that is driven into resonance and excites a secondary oscillation in either the same structure or in a second one, due to the Coriolis force made their apparition for anti-skidding system and also for navigation unit. The widespread use of accelerometers in the automotive industry has pushed their cost down dramatically.
Accelerometers have also found real•time applications in controlling and monitoring military and aerospace systems. Smart weapon systems (direct and indirect fire; aviation-launched and ship-launched missiles, rockets, projectiles and sub munitions) are among these applications. Some MEMS sensors have already been used in satellite. The development of micro (less than lOOkg) and nano (about lOkg) satellites is bringing the mass and volume advantage of MEMS to good use.
MEMS augments this decision-making capability with ”eyes” and ”arms”, to allow Microsystems to sense and control the environment. Sensors gather information from the environment through measuring mechanical, thermal, biological, chemical, optical, and magnetic phenomena. The electronics then process the information derived from the sensors and through some decision making capability direct the actuators to respond by moving, positioning, regulating, pumping, and filtering, thereby controlling the environment for some desired outcome or purpose. Because MEMS devices are manufactured using batch fabrication techniques similar to those used for integrated circuits, unprecedented levels of functionality, reliability, and sophistication can be placed on a small silicon chip at a relatively low cost.