Area of research: Control Systems. The topics of interest are as follows:
1. Trying to overcome the robustness problems associated with Linear-Time-Invariant (LTI) controllers in compensating LTI plants having unstable zeros, both in continuous- and discrete-time domain, leading to the development of high-frequency-continuous-time and generalized-multirate-discerte-time controllers. The design philosophy is based on the fundamental point that while LTI controllers can not change the zeros (which decide what the closed-loop roots for high loop-gain would be), periodic controllers can relocate the loop-zeros at desired locations leading to much better loop loop robustness. Some of the difficulties involved are: (i) developing suitable mathematical tools for stability and performance analysis of such systems, (ii) devloping algorithms for evaluation of controller parametrs for achieving pole and zero-placement, (iii) ensuring ripple-free response and (iv) issues related with implementation of such controllers in practice. In fact the mettle of the periodic controllers developed have all been tested on physical, laboratory scale
2. Development of Periodic controllers for MIMO systems is being tried. One approach is to decouple the plant. A general decoupling result has been developed. The same is found to allow much superior control of MIMO systems via periodic control of its decoupled SISO units.
3. Single actuator but multiple sensor systems occur often in practice. The robustnes of such systems with respect to variations in the sensor characteristics is found not to be ensured in literature. LMI and H-infinity based optimal state feed-back controllers for the robustness of such systems is being investigated.
4. Decentralized stabilization of uncertain systems with time delays refer to a broad class of problems with practical interest. A broad LMI condition for this purpose has been developed based on a superior choice of the Lyapunov functional, leading to superior results.
Multi(2)-Rate Control From a 2-Periodic Perspective: Generalized 2-Rate Control by S. Chakraborty and S. K. Das IEEE Transactions on Automatic Control Volume 61 1631-1636 (2016)
Techniques of analysis and robust control via zero-placement of periodically compensated discrete-time plants by S. K. Das and P. K. Rajagopalan Control and Dynamic Systems - Volume 74: Techniques in Discrete and Continuous Robust Systems 133-170 (1996)
Periodic Compensation of Continuous-Time Plants by S. K. Das and J. Dey IEEE Transactions on Automatic Control Volume 52 898-904 (2007)
Robust compensation of a Cart-Inverted Pendulum System Using a Periodic Controller: Experimental Results by S. K. Das and K. K. Paul Automatica Volume 47 2543-2547 (2011)
Open-Loop Decoupling of MIMO Plants by A. Ghosh and S. K. Das IEEE Transactions on Automatic Control Volume 54 1977-1981 (2009)
Decentralized Stabilization of Uncertain Systems With Interconnection and Feedback Delays: An LMI Approach by S. Ghosh, S. K. Das and G. Ray IEEE Transactions on Automatic Control Volume 54 915-912 (2009)
Stability Analysis of Hill Systems by S. K. Das IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications Volume 43 794-797 (1996)
Simultaneous Pole Placement of M Discrete-Time Plants Using a M-Periodic Controller by S. K. Das and P. K. Kar IEEE Transactions on Automatic Control Volume 48 2045-2050 (2003)
Periodic Discrete-Time Systems: Stability Analysis and Robust Control Using Zero Placement by S. K. Das and P. K. Rajagopalan IEEE Transactions on Automatic Control Volume 37 374-378 (1992)
Periodic Compensation of a Class of Decentralized Systems with Fixed Modes by A. Ghosh and S. K. Das Automatica Volume 46 1563-1567 (2010)
Area of Research: Periodic control
Ankesh Kumar Agrawal
Area of Research: Periodic control of dynamical systems
Area of Research: Periodic/multi-rate control of discrete-time MIMO systems