The future pioneers
Nanotechnology Small is the next Big Thing !
The statement that ‘ Everything on Earth is made up of atoms ’ may raise several eyebrows but yes , that ’ s true ! Everything on earth , including the food we eat , the houses we live in , the clothes we wear , and our own bodies , is made up of atoms . Nanoscience and nanotechnology involve the capacity to observe and to manage individual atoms and molecules .
Nanotechnology to become key technology
Nanotechnology is supposed to become the key technology of 21st century . The field of nanotechnology is emerging and expanding and is applicable to diverse domain of physical systems . It is the understanding and control of matter at the nanoscale i . e . dimensions between 1 and 100 nanometers , where unique phenomenon enables novel applications . The engineering research in nanotechnology is expected to lead to breakthrough in the areas such as health care and medicine , advanced materials , electronics , manufacturing , biotechnology , defense etc . It is widely recognized that one of the key requirement of nanotechnology is the nanopositioning .
What is Nanopositioning ?
Nanopositioning is the precision control and manipulation of devices and materials at nanoscale with incredible accuracy . Nanopositioners are precise mechatronic systems designed not only to move or position a probe , part , tool , sample , or device at some desired position with nanometer accuracy and repeatability but also to resolve adjacent positions that are separated by less than a nanometer . The desired performance characteristics of a nanopositioner are precise positioning , long travel range , extremely high resolution , accuracy , wide bandwidth , stability , fast response with very small or no overshoot . To achieve all these characteristics , a large number of nanopositioning system geometries have been available .
Developments in the nanopositioning system
A nanopositioning system is an assembly of precise detection system , solid state smart actuators driven by the control systems and monolithic motion guide stage . In order to realize precise positioning at sub nanometer resolution , all these elements are to be carefully designed , analyzed and optimized . For highly accurate and high speed nanoscale positioning applications , recently , nanopositioning systems based on the piezoelectric stack actuators using flexure guided mechanism have been developed .
Some complexities in the system
Although the piezoelectric actuator based nanopositioning systems are designed to provide greatest possible accuracy and unlimited resolution , but in practice they exhibit inherent non ideal characteristics such as creep , hysteresis and vibration effects that severely degrade its performance . In addition to these nonlinearities , the performance characteristics of nanopositioning system are highly affected by mechanical dynamics / design of the motion stage , external disturbances and drift due to the temperature variation .
How to improve performance of the nanopositioning system ?
To reduce inherent nonlinearities of piezoelectric actuator and to improve nanopositioning system performance , control plays an important role . The performance analysis of control system focuses on time domain characteristics such as maximum overshoot , rise time , settling time and steady state error and frequency domain characteristics such
as phase and gain margins .
The article is intended to address the major issues of the modeling and control of nanopositioning system . Further , investigation and development of the feedback control schemes to achieve satisfactory system performance i . e . good time response and frequency response characteristics have also been done . Design and implementation of conventional controllers , state feedback controllers and robust controllers for nanopositioning system have been done to achieve better system performance . Simulated results of different controllers are compared and it has been analyzed that the performance characteristics of the nanopositioning system have been improved . It has been concluded that different type of controller works well for different conditions and applications . The simulated results are obtained in MATLAB environment . The present work can be further extended to investigate modeling and control of nanopositioning system including non-linearities , control of multi axes nanopositioning system and real time application of nanopositioning system in future .
About the Author
Dr . Sheilza Jain is an Assistant Professor at YMCA University of Science and Technology , Faridabad in the Department of Electronics Engineering .
JuNe-july 2018 | Global MDA Journal | 17