Concept of Smart Structures

The dictionary definition of the word “Smart” (brisk, spirited, mentally alert, bright, clever) is not quiet adequate for an engineer.

For an engineer “A Smart Structure” means a structure that can sense an external disturbance and respond to that with active control in real time to maintain the mission requirements. A Smart Structure typically consists of a host structure incorporated with sensors and actuators coordinated by a controller.

The integrated structured system is called Smart Structure because it has the ability to perform self diagnosis and adapt to environmental change. One promising application of such smart structure is the control and suppression of unwanted structural vibrations.

Smart Structure

Smart Structure comprise of host structure along with Sensors, Actuators & controller networks. Consider a simply supported beam as a smart structure.

Basic Elements of a Smart Structure

The major components are:

Sensor Patch
It is bonded to the host structure (Beam). It is generally made up of piezoelectric crystals (one of the smartest materials). It senses the disturbance of the beam and generates a charge which is directly proportional to its strain. Direct piezoelectric effect is used here.

Controller
The charge developed by the sensor is given to the controller. The controller lines the charge according to suitable control gain and then the charge is fed to the actuator. Controller also forms the feed back transfer function for this system.

Actuator Patch
The lined up charge from the controller is fed to the actuator. An actuator is a piezoelectric patch bonded to the host. Due to the input voltage, actuator causes pinching action (or generates shear force along the surface of the host which acts as the damping force and helps in the attenuating vibration motion of the beam. Converse piezoelectric effect is used here.