A Micro Electro Mechanical Systems is a manufacturing technology of small devices and it is the combination of the mechanical elements, sensors, electronics and actuators on a substrate through micro technology. It is used to produce a system of miniature dimensions.MEMS are very attractive because of their weight and size which range from micrometers to millimeters. Therefore, MEMS are used in different applications such as optical networks, sensor systems and display technologies, etc.
MEMS can also be found in pressure sensors, flow sensors, deformable mirror devices, inkjet printers, gas sensors, micro motors, accelerometers, micro gears, and lab-on-a-chip systems. These products are all fabricated in high-profitable volumes. A MEMS sensor is usually assembled by similar etching or masking process as microchips. A common MEMS sensor is an accelerometer to measure acceleration.
Introduction to MEMS Sensors
A Sensor is a device that measures a physical quantity and changes it into an electrical signal. Sensor plays a major role in MEMS and can be used in arrangements with other sensors for multi-sensing applications. These sensors are classified into three types:
- MEMS Pressure Sensors
- MEMS Chemical Sensors
- MEMS Inertial Sensors (gyroscopes, accelerometers)
MEMS Pressure Sensors
A pressure sensor is a device that consists of electronic and mechanical components. MEMS pressure sensor uses a flexible diaphragm as the sensing device. One side of this diaphragm is uncovered to a seal and the other side is open to external pressure as it moves with a change in the external force. MEMS pressure sensors are very simple, cheap, and small; these factors allow these sensors to address applications in industrial process control, automobiles as well as the ones involved in handheld portable and medical products.
MEMS Chemical Sensors
MEMS chemical sensors contain chemically selective membrane, layer or a film that measures chemical nature of its environment. Generally, mechanical sensors provide high levels of accuracy and resolution, whereas the MEMS chemical sensors have more demand even if they may or may not be realizable. Indeed, these sensors provide stability, selectivity, high sensitivity, and high speed. Most chemical sensors are not stable, and that they are considerable with respect to the overall dynamic range. Nowadays several types of MEMS devices are being discovered as chemical sensors.
MEMS Inertial Sensors
MEMS inertial sensors are designed to sense a change in an object’s inertia, and then convert this inertial force into a measurable signal. They measure changes in vibration, acceleration, inclination and orientation. This is done by using micro devices called gyroscopes and accelerometers. MEMS Inertial Sensors find their applications in automobiles sectors, motion and shock detection equipment, vibration detection and measurement systems, anti-theft devices, home security systems, and so on.
An accelerometer is an electromechanical device that is used to measure acceleration forces. Accelerometers are being included into many electronic devices such as gaming devices, and the media players and smart phones like Apple phone, iPhone use accelerometers for a better user interface control and step counters. MEMS accelerometers are one of the simplest and most applicable systems.
MEMS Accelerometers have also become essential in audio-video technology, computers and automobile industry. These are now quickly replacing the predictable accelerometers for crash airbags deployment systems in automobiles. MEMS accelerometers are cheap, small and more efficient, and possess simplest sensors consisting of an inertial mass suspended by springs. The mass is redirected from its actual position as a result of acceleration. The deflection of the mass is changed to an electrical signal as the sensor’s output.
A gyroscope is usually a spinning wheel or a disk with a free axis allowing it to take any orientation. To determine orientation, some gyroscopes use a vibrating structure moderately than the traditional rotating disk.
MEMS based Hands Gesture Controlled Robot
The main intend of this project is to control a robot using MEMS. In this system, the MEMS is fixed to the hand. The block diagram of the MEMS based hands gesture controlled robot is shown below.
The required hardware tools include a microcontroller, an MEMS sensor, an RF transmitter and a receiver driver circuit and DC motors. In addition to this, the required software tools are Orcad, Proload and Keil compiler. The 7805 IC is a 9V voltage regulator, and it has some features like internal current limit, thermal and safe area protection.
In this set up, the transformer steps down the 230 voltage into 16 V, 1A, and the bridge rectifier rectifies and the capacitor filters it. Finally, to produce a steady 5V DC output, the 7805 regulator regulates it. The AT89S52 is a high-performance CMOS 8-bit microcontroller with 8K bytes of programmable flash memory; it provides a cost-effective and highly flexible solution to many embedded applications.
Top Features of AT89S52 Microcontroller
- Operating range is from 4V to 5.5V
- Static Operation: 0Hz to 33MHz
- Three level program memory lock
- 256×8-bit internal RAM
- 32 programmable I/O lines
- 16 bit Timers/Counters
- 8- Interrupt sources
- UART serial channel
A MEMS sensor is generally designed by a similar masking process as used in microchips. The MEMS sensor is an accelerometer used to measure acceleration.
Nowadays remote robots control is performed by using a cell phone or a remote or by a wired connection. If we think about hardware and cost for low-level applications, all such things increase the complexity. The robot that we have designed in this context is the one which is different from this. It doesn’t have the need of any remote or communication module.
This robot consists of three parts such as microcontroller, MEMS sensor and Motor driver. This is MEMS based hands gesture controlled robot which is self activated and controlled by hand gestures. In this project, the MEMS is set to the hand which includes an acceleration meter. Whenever the hand moves in any direction, the MEMS recognizes the mechanical movement of the hand and converts this movement into electrical signals and sends it to the microcontroller.
At the transmitter side, the microcontroller receives the electrical signals and sends equivalent signals to the receiver end through an RF transceiver. At the receiver end, the microcontroller receives the signals from the RF transceiver and finally a motor driver is used to control the motor.
In future, we will design a wireless robot capable of sensing hand gestures by using wireless technology. It can be used in military applications as a robotic vehicle. Please leave your comments about the MEMS based robot applications in the comments section below and your views for further advancement.
- MEMS Sensors by bosch
- MEMS Pressure Sensors by directindustry
- MEMS Chemical Sensors by typepad
- MEMS Inertial Sensors by eecatalog