Tooran Emami

Discrete time robust stability design of PID controllers autonomous sailing vessel application

This paper presents a successful graphical technique for finding all discrete-time proportional integral derivative (PID) controllers that satisfy a robust stability constraint for heading control of a 2 meter autonomous sailing vessel. This problem is solved by finding all achievable discrete time PID controllers that simultaneously stabilize the closed-loop characteristic polynomial and satisfy constraints defined by a set of related complex polynomials. The bilinear transformation is used to describe the discrete time PID controllers. The discrete-time model of the vessel is identified from a sampled data system with uncertain communication delay. Experimental data taken from this vessel at the U. S. Coast Guard Academy is used to demonstrate the application of this methodology.

Determination of all stabilizing analog and digital PID controllers

In this paper, a unified approach is introduced for finding the stability boundary and the number of unstable poles in the integral derivative (ID) plane for continuous-time or discrete-time PID controllers. The ID plane is particularly important because in this plane it is easier than in the PI or PD planes to determine the entire stability region. These problems can be solved by finding all achievable PID controllers that stabilize the closed-loop polynomial of a single-input single-output (SISO) linear time invariant (LTI) system. This method is used to predict the number of unstable poles of the closed-loop system in any region of the parameter space of a PID controller. The delta operator is used to describe the controllers because it provides not only numerical properties superior to the discrete-time shift operator, but also converges to the continuous-time case as the sampling period approaches zero. A key advantage of this approach is that the stability boundary can be found when only the frequency response and not the parameters of the plant transfer function are known. A unified approach allows us to use the same procedure for finding the continuous-time or discrete-time stability region and the number of unstable poles of the closed-loop system.

Adaptive Control of a Nonlinear Fuel Cell-Gas Turbine Balance of Plant Simulation Facility

A 300kW Solid Oxide Fuel Cell Gas Turbine (SOFC-GT) power plant simulator is evaluated with the use of a Model Reference Adaptive Control scheme, implemented for a set of nonlinear empirical Transfer Functions. The SOFC-GT simulator allows testing of various fuel cell models under a Hardware-in-the-Loop configuration that incorporates a 120kW Auxiliary Power Unit, and Balance-of-Plant components in hardware, and a fuel cell model in software. The adaptation technique is beneficial to plants having a wide range of operation, and strong coupling interaction. The practical implementation of the adaptive methodology is presented through simulation in the MATLAB/SIMULINK environment.© 2014 ASME

Robust stabilization of time-delay systems using PID controller with a Smith predictor

Time delays in the feedback complicate the analysis and design of the closed-loop system. The use of a Smith predictor in combination with a Proportional Integral Derivative (PID) controller is a well-known technique for dealing with these delays in stable systems. However, many authors have questioned the robustness of this approach when the model of the plant is not known exactly. In this paper, the authors tackle this problem directly by determining all PID controllers working in combination with a Smith predictor that robustly stabilize the closed-loop system. The use of a Smith predictor tends to increase the size of the set of all robustly stable PID controllers in the controller parameter space. A numerical example is used to compare the set of robustly stabilizing PID controllers with and without a Smith predictor.

Determination of All Stabilizing PID Controllers for Time Delay Systems With Smith Predictors

Time delays in the control loop complicate the analysis and design of controllers. The use of a Smith predictor is a well-known technique for dealing with delays in stable systems. This paper presents a method for finding all stabilizing Proportional Integral Derivative (PID) controllers when the Smith predictor is used. This paper introduces a general method to determine all achievable PID controllers even when there is a mismatch between the plant and Smith predictor model. A key advantage of this approach is that it requires only the frequency response of the plant.Copyright

Noncooperative Distributed MMSE Schemes for AF SIMO Wireless Relay Networks

This paper presents a noncooperative distributed amplify-and-forward (AF) single-input multiple-output (SIMO) wireless relay networks under two adverse wireless communication environments: (1) node geometry and a jamming environment, and (2) channel uncertainty and a jamming environment. All relay nodes in wireless relay networks cannot exchange their received signals from source nodes for relay noncooperation. The main contribution of this paper is the derivation of an optimal diagonal amplifying relay matrix in AF SIMO wireless relay system using the minimum mean square error (MMSE) criterion. To evaluate the effects of two adverse wireless communication environments on the AF SIMO relay scheme, simulation results are presented for a system using the derived optimal diagonal amplifying relay matrix with bit error rate (BER). In addition, performance comparisons under no node geometry, no-jamming environment, and no channel uncertainty were also considered.

Estimate of discrete-time PID controller parameters for H-infinity complementary sensitivity design: Autonomous sailboat application

This paper presents some of the successful design methodologies used to predict the robustness of a heading controller for a 2 meter autonomous sailing vessel. A graphical technique is introduced to estimate the discrete-time proportional integral derivative (PID) controller coefficients to satisfy H-infinity complementary sensitivity constraints for vessel control. We show that this problem can be solved by finding all achievable PID controllers that simultaneously stabilize the closed-loop characteristic polynomial and satisfy constraints defined by a set of related complex polynomials. Experimental data taken from this vessel at the U. S. Coast Guard Academy is used to demonstrate the application of this methodology.

Cooperative Distributed MISO Wireless Relay Networks Under Jamming Environments with Power Constraints

This paper introduces a cooperative distributed wireless relay network under a jamming environment at three different locations. An amplify-and-forward (AF) multiple-input single-output (MISO) system is considered with N-relay nodes. For full relay cooperation, all relay nodes in wireless relay networks exchange their received signals from source nodes with no errors. An optimal non-diagonal amplifying relay matrix is derived using the minimum mean square error (MMSE) criterion under power constraints at the relay nodes. The performance of the system by implementing the derived optimal non-diagonal amplifying relay matrix is evaluated using the bit error rate (BER). For performance comparison, no-jamming environment and the other three special cases corresponding to different locations of the broadband noise jamming (BNJ) are also considered.

Computer support for teaching the Routh-Hurwitz criterion

This paper presents a method of computer support for teaching the Routh-Hurwitz criterion in two different undergraduate junior level Electrical Engineering courses at the United States Coast Guard Academy. Software Engineering (SWE) and Computer Control Systems (CCS) are two courses that students use C# programming and MATLAB® software to learn about the Routh-Hurwitz principle and its applications. In SWE the objectives are to apply the Routh-Hurwitz criterion to the procedural and object-oriented C# programming skills in order to implement code with a user-friendly Graphical User Interface (GUI). In this laboratory the GUI allows the user to enter the values that represent the coefficients of a polynomial. The results of the GUI return whether the polynomial represents a stable or unstable system. In CCS the objectives are modeling the physical system and applying the Routh-Hurwitz criterion to analyze the closed loop system performance. In this lab students determine the mathematical model for an antenna azimuth position control system. They then apply the Routh-Hurwitz criterion to find all proportional gains for the controllers that meet certain performance requirements for the antenna position control system. The modeling and system performance are achieved via calculation by hand, programming, and simulation using MATLAB® and its Control System Toolbox. Students in these two particular labs demonstrate achievement of numerous a-k ABET criteria.