08-03-2011, 11:59 AM
[attachment=9758]
MEMS based accelerometer in robotic arm
What is MEMS
MEMS:
Micro Electro Mechanical Systems.
That are made using the techniques of micro fabrication.
Micron devices that perform the same function as larger mechanical systems.
Micro fabricated sensors, actuators, and electronics on a common substrate or in a single package.
Why MEMS?
MEMS – Microelectromechanical Systems
Typically made using silicon or SiO2 wafers
Fabricated using IC processing Techniques
Reduced Size
Reduced Cost
Reduced Mass
Reduced Power Consumption
Increased Natural Frequency
MEMS Accelerometer
Converts acceleration from motion (dynamic acceleration) or gravity (static acceleration) to either analog or digital electrical signals.
Polysilicon, surface micromachined sensor and signal conditioning circuitry for 3 axis acceleration
Polysilicon mass in center is held by polysilicon springs that create the resistance against acceleration forces which in turn converts this in to electrical signals
How Do MEM’s Accelerometers Work?
We use Silicon to make the spring and mass, and add fingers to make a variable differential capacitor
We measure change in displacement by measuring change in differential capacitance
MEM’s Accelerometer
Functional block diagram
FEATURES
3-axis sensing
Small, low profile package
Generally 4 mm × 4 mm × 1.45 mm in dimension
Low power : 350 to 600 μA (typical)
Single-supply operation
10,000 g shock survival
Excellent temperature stability
BW adjustment with a single capacitor per axis
Output Type: Analog
robotic arm
Computer-controlled machine that is programmed to move, manipulate objects, and accomplish work while interacting with its environment.
Robots are able to perform repetitive tasks more quickly, cheaply, and accurately than humans.
The aim is to program a robot using microcontroller , so that it will utilise electrical signals from accelerometer sensors and run its stepper motors based on tilt and motion from robotic arm .
Block diagram representation
Acceleration Measurements for programming
Motor system
Motion control
• Power the wheels
Power method 1: Mechanical relay
Power method 2: Single direction Power Transistor
Power method 3: Dual direction H-bridge circuits
Power method1: Direct Current DC Motors by mechanical relay
Power method 2: Direct Current DC motors by transistor (one direction)
Power method 3: Direct Current DC motors by H-bridge transistor circuit (Two-direction)
Applications
Human machine interface.
crash detector in airbag.
