Control Applications
Power Systems
Our main contribution of this work is to apply the machinery of modern robust control to the stability problems of large scale power systems, to address the issues pertinent to the applications of these tools to power systems, and to demonstrate that the tools can be effective in controller analysis and design.
Conventional techniques for designing Power System Stabilizers (PSS) are based on one selected operating point together with extensive linear and nonlinear time-domain simulations. In contrast, we have developed a systematic approach for analyzing and designing Power System Stabilizers for large-scale power systems using the state of the art methods in robust control theory. These methods have been tested on realistic system with as many as 50 generators and were shown to provide significantly better stability margins that the conventional controllers.
Selected publications
- Wenzheng Qiu, Vijay Vittal, and Mustafa Khammash, “Decentralized Power System Stabilizer Design using Linear Parameter Varying Approach,” IEEE Transactions on Power Systems, 19:1951-1960, Nov. 2004.
- C. Zhu, M. Khammash, V. Vittal and W. Qiu, "Robust Power System Stabilizer Design using H-infinity Loop Shaping Approach,” IEEE Transactions on Power Systems, vol. 18, no. 2, pp.810-818.
- M. Djukanovic, M. Khammash, and V. Vittal, “Sensitivity Based Structured Singular Value Approach to Stability Robustness of Power Systems”, IEEE Transactions on Power Systems, vol. 15, No 2, pp. 825—830, May 2000.M. Djukanovic, M. Khammash, and V. Vittal, “Sequential Synthesis of Structured Singular Value Based Decentralized Controllers in Power Systems” IEEE Transactions on Power Systems, vol. 14, No. 2, pp. 635—641, May 1999.
- M. Djukanovic, M. Khammash, and V. Vittal, “Application of the Structured Singular Value Theory for Robust Stability and Control Analysis in Multi-Machine Power Systems, Part II: Numerical Simulations and Results”, IEEE Transactions on Power Systems, vol. 13, No. 4, November 1998, pp. 1317-1322.
- Djukanovic, M. Khammash, and V. Vittal, “Application of the Structured Singular Value Theory for Robust Stability and Control Analysis in Multi-Machine Power Systems, Part I: Framework Development,” IEEE Transactions on Power Systems, vol. 13, No. 4, November 1998, pp. 1311-1316.
Cooperative Control
Cooperative control involves multiple autonomous agents work together to perform a task. We have considered cooperative control problems where the task causes strong coupling between the agents (typically flying unmanned vehicles). In this context, we have obtained an analytic solution for locating a transmitter/radar based on time-differences of arrival and used this method to show that there are simple rules for vehicle configurations that maximize estimation accuracy. We have used this solution in conjunction with Kalman Filtering to design estimation schemes. For online cooperative control we have used optimal control theory to develop and apply practical methods for systems with state constraints. Finally, we have used coordination structures to design a partially decentralized one-step algorithm for guidance, which is superior to existing ones.
Selected publications:
- Keith Purvis, K. Astrom and Mustafa Khammash, “Estimation and Optimal Configurations for Localization using Cooperative UAVs,” IEEE Transactions on Control Systems Technology, in press.
- K. Purvis, K. Astrom, and M. Khammash, “Practical Methods for Highly Coupled Cooperative UAVs,” proceedings of the American Control Conference, 2007.
- Keith Purvis, K. Astrom, and M. Khammash, “Estimating Radar Positions Using Cooperative Unmanned Air Vehicle Teams,” proceedings of the American Control Conference, 2005.
Tunneling MEMS Accelerometer Controller Design
We have designed a robust feedback controller for an ultra-sensitive, high-bandwidth, tunneling accelerometer. The control design uses a loop-shaping technique to achieve high disturbance rejection, noise attenuation, and robustness to parameter variations. Nonlinear simulations of the device demonstrate that it can accurately and robustly sense forces over its control bandwidth even when its parameters have been perturbed away from their nominal values.
Selected publications:
- M. Khammash, L. Oropeza-Ramos, and K. Turner, “Robust Feedback Control Design of an Ultra-Sensitive, High Bandwidth Tunneling Accelerometer,” proceedings of the American Control Conference, 2005.