Raymond H. Byrne

Delayed Positive Feedback Can Stabilize Oscillatory Systems

This paper expands on a method proposed in [1] for stabilizing oscillatory system with positive, delayed feedback. The closed-loop system obtained is shown (using the Nyquist criterion) to be stable for a range of delays.

Experimental implementation of flocking algorithms in wheeled mobile robots

In this paper we present an experimental implementation of the flocking algorithm presented by H.G. Tanner et al., (2003) for the double integrator model, in the case of wheeled mobile robots (WMR). We use the look ahead concept to feedback linearize the WMR model and obtain its double integrator form in which we apply the control signals in the form of voltages in wheel motors. A virtual leader is used to steer the flock in the desired direction. Comparisons of the experimental results with simulation verify the robustness of this algorithm to model uncertainties and communication delays.

Experimental results in robust lateral control of highway vehicles

Vehicle lateral dynamics are affected by vehicle mass, longitudinal velocity, vehicle inertia, and the cornering stiffness of the tires. All of these parameters are subject to variation, even over the course of a single trip. Therefore, a practical lateral control system must guarantee stability, and hopefully ride comfort, over a wide range of parameter changes. This article describes a robust controller that theoretically guarantees stability over a wide range of parameter changes. The performance of the robust controller is then evaluated in simulation as well as on a test vehicle. Test results for experiments conducted on an instrumented track are presented, comparing the robust controller to a PID controller that was tuned on the vehicle.

Moving mass trim control system design

This paper describes the design of a moving mass trim control system for maneuvering axisymmetric reentry vehicles. The moving mass trim controller is composed of three equal masses that are independently positioned in order to deliver a desired center of mass position. For a slowly spinning reentry vehicle, the mass offset creates a trim angle-of-attack to generate modest flight path corrections. The control system must maintain the desired position of each mass in the face of large disturbances. A novel algorithm for determining the desired mass positions is developed in conjunction with a preliminary controller design. The controller design is based on classical frequency domain techniques where a bound on the disturbance magnitude is used to formulate the disturbance rejection problem. Simulation results for the controller are presented for a typical reentry vehicle.

A moving mass trim control system for reentry vehicle guidance

This paper describes the design of a movingmass, trim-control system for maneuvering antisymmetric reentry vehicles. The moving-mass trim controller is composed of three equal masses that are independently positioned in order to deliver a desired center of mass position. For a slowly spinning reentry vehicle, the mass offset creates a trim angle-of-at tack to generate modest flight path corrections. A proportional navigation guidance scheme is used to determine the desired lateral accelerations required to hit the target. Mass movements are calculated from the desired lateral accelerations. Simulation results for the integrated guidance and control system are presented for a typical reentry vehicle.

Design of a model reference adaptive controller for vehicle road following

The design of a model reference adaptive controller (MRAC) for vehicle road following is discussed. There are many factors which make automatic lateral control of vehicles difficult. These include changing vehicle parameters, changing road conditions, as well as disturbances caused by wind and other factors. Traditional controllers have difficulty guaranteeing performance and stability over a wide range of parameter changes. Model reference adaptive controllers on the other hand, can guarantee both stability and performance over a wide range of slowly varying parameter changes as long as several conditions are met. Difficulties with model reference adaptive controllers (as well as other controllers) arise when saturation appears on the input or states. For vehicle applications, the steering angle is limited. Therefore, the adaptation gains for the MRAC designed in this paper were chosen so that the steering command remained reasonable, even during adaptation. We finally show that there is a tradeoff regarding input amplitude and input frequency during adaptation.

Damping of inter-area oscillations using energy storage

Low frequency inter-area oscillations have been identified as a significant problem in utility systems due to the potential for system damage and the resulting restrictions on power transmission over select lines. Previous research has identified real power injection by energy storage based damping control nodes as a promising approach to mitigate inter-area oscillations. In this paper, a candidate energy storage system based on UltraCapacitor technology is evaluated for damping control applications in the Western Electric Coordinating Council (WECC), and an analytical method for ensuring proper stability margins is also presented for inclusion in a future supervisory control algorithm. Dynamic simulations of the WECC were performed to validate the expected system performance. Finally, the Nyquist stability criteria was employed to derive safe operating regions in the gain, time delay space for a simple two-area system to provide guaranteed margins of stability.

Potential revenue from electrical energy storage in the Electricity Reliability Council of Texas (ERCOT)

This paper outlines the calculations required to estimate the maximum potential revenue from participation in arbitrage and regulation in day-ahead markets using linear programming. Then, we use historical Electricity Reliability Council of Texas (ERCOT) data from 2011-2012 to evaluate the maximum potential revenue from a hypothetical 32 MWh, 8 MW system. We investigate the maximum potential revenue from two different scenarios: arbitrage only and arbitrage combined with regulation. Our analysis shows that, with perfect foresight, participation in the regulation market would have produced more than twice the revenue compared to arbitrage in the ERCOT market in 2011 and 2012. Three simple trading strategies that do not rely on perfect knowledge are then compared to the optimization results.

Estimating the maximum potential revenue for grid connected electricity storage

The valuation of an electricity storage device is based on the expected future cash ow generated by the device. Two potential sources of income for an electricity storage system are energy arbitrage and participation in the frequency regulation market. Energy arbitrage refers to purchasing (stor- ing) energy when electricity prices are low, and selling (discharging) energy when electricity prices are high. Frequency regulation is an ancillary service geared towards maintaining system frequency, and is typically procured by the independent system operator in some type of market. This paper outlines the calculations required to estimate the maximum potential revenue from participating in these two activities. First, a mathematical model is presented for the state of charge as a function of the storage device parameters and the quantities of electricity purchased/sold as well as the quantities oered into the regulation market. Using this mathematical model, we present a linear programming optimization approach to calculating the maximum potential revenue from an elec- tricity storage device. The calculation of the maximum potential revenue is critical in developing an upper bound on the value of storage, as a benchmark for evaluating potential trading strate- gies, and a tool for capital nance risk assessment. Then, we use historical California Independent System Operator (CAISO) data from 2010-2011 to evaluate the maximum potential revenue from the Tehachapi wind energy storage project, an American Recovery and Reinvestment Act of 2009 (ARRA) energy storage demonstration project. We investigate the maximum potential revenue from two dierent scenarios: arbitrage only and arbitrage combined with the regulation market. Our analysis shows that participation in the regulation market produces four times the revenue compared to arbitrage in the CAISO market using 2010 and 2011 data. Then we evaluate several trading strategies to illustrate how they compare to the maximum potential revenue benchmark. We conclude with a sensitivity analysis with respect to key parameters.

Wind generation controls for damping of inter-area oscillations

Inter-area oscillations are one of the factors that limit transmission capacity in large interconnected systems. In this paper we investigate the effects of increasing wind generation on inter-area modes and propose the use of additional control schemes for wind plants for mitigation of inter-area oscillations. Control schemes include droop control and inertial emulation, which are originally aimed at improving transient stability. The sensitivities of inter-area modes to droop control and inertial emulation gains are identified. Implementation of suggested controls schemes via collocated energy storage devices is also explored.