Erhun Iyasere

Nonlinear robust control to maximize energy capture in a variable speed wind turbine

The emergence of wind turbine systems for electric power generation can help satisfy the growing global demand. To maximize wind energy captured in variable speed wind turbines at low to medium wind speeds, a robust control strategy is presented. The proposed strategy simultaneously controls the blade pitch and tip speed ratio, via the rotor angular speed, to an optimum point at which the efficiency constant (or power coefficient) is maximum. The control method allows for aerodynamic rotor power maximization without the restrictions of exact wind turbine model knowledge. A series of numerical results show that the wind turbine can be controlled to achieve maximum energy capture.

Backstepping PWM control for maximum power tracking in photovoltaic array systems

A power system consisting of a photovoltaic (PV) array panel, dc-to-dc switching converter and a battery is considered in this paper. A backstepping PWM controller is developed to maximize the power of the solar generating system. The controller tracks a desired array voltage, designed online using an incremental conductance extremum-seeking algorithm, by varying the duty cycle of the switching converter. The stability of the control algorithm is demonstrated by means of Lyapunov analysis.

Optimizing antiangiogenic therapy for tumor minimization

In this paper, optimization of antiangiogenic therapy for tumor management is considered as a nonlinear control problem. A new technique is developed to optimize antiangiogenic therapy which minimizes the volume of a tumor and prevents it from growing using an optimum drug dose. To this end, an optimum desired trajectory is designed to minimize a performance index. Two controllers are then presented that drive the tumor volume to its optimum value. The first controller is proven to yield exponential results given exact model knowledge. The second controller is developed under the assumption of parameteric uncertainties in the system model. A least-squares estimation strategy based on a prediction error formulation and a Lyapunov-type stability analysis is developed to estimate the unknown parameters of the performance index. An adaptive controller is then designed to track the desired optimum trajectory. The proposed tumor minimization scheme is shown to minimize the tumor volume with an optimum drug dose despite the lack of knowledge of system parameters.

A Real Time Re-Configurable Steering Simulator for System Design Studies

The automotive steering system plays an important role in determining the behavioral dynamics of the operator/vehicle interface. The systems primary function is to transmit the driver commanded steering wheel angle to the road wheels; The secondary function is to provide tire/road interface information back to the driver. The automotive chassis engineer needs a design tool to evaluate the effect of steering parameters on overall vehicle lateral behavior. In this paper, a real time steering simulator will be presented to emulate the behavior of automotive steering systems. The re-configurable steer- by-wire simulator allows for the emulation of steering systems ranging from hydraulic, electric and steer-by- wire in passenger, light duty, and commercial vehicles for pre-production and production models. To validate the simulators functionality, a case study has been performed with numerical and experimental data. Comparisons between the simulator results and field data demonstrate a high level of correspondence. The re-configurable simulator evaluation tool represents a contribution to the field of automotive design.

Creation of a driver preference objective metric to evaluate ground vehicle steering systems

The evaluation of vehicle steering systems has typically been performed by engineers and consumer focus groups using in-vehicle and automotive simulator studies. In the latter case, driver preferences have been extensively gathered using written questionnaires. However, this delays the testing procedure and may introduce outside influences that may skew the results. In this paper, an objective steering preference metric has been created to gather steering preferences without directly communicating with the driver. Streaming vehicle data has been recorded, processed, and correlated with subjective response data to create a global steering preference metric. A combination of the vehicles yaw rate, longitudinal acceleration, and lateral acceleration demonstrated an excellent correlation with survey responses regardless of the steering setting. Furthermore, changes in the steering ratio resulted in an even stronger correlation between the objective data (longitudinal acceleration, front tire angle, and throttle position) and test subject questionnaire responses. Overall, the proposed index offers a unique approach to evaluate steering system designs.

Evaluation of driver steering preferences using an automotive simulator

A high fidelity steering simulator was developed and validated to support driver steering preference studies. The steering simulator was validated using in-vehicle test data and two pilot studies before application to a demographics-based driver preference study with 43 subjects. This latter study reflected the following trends: drivers who used their vehicles for utility purposes preferred faster steering ratios and heavier steering torque in residential, country, and highway environments. In contrast, car enthusiasts preferred fast steering ratios in residential and country environments and light steering torque on the highway. These relationships may be used to set steering targets, during future vehicle developments, to accurately match vehicles to their intended market segments.

Nonlinear robust control to maximize energy capture in a variable speed wind turbine using an induction generator

The emergence of wind turbine systems for electric power generation can help satisfy the growing global demand. This paper proposes a control strategy to maximize the wind energy captured in a variable speed wind turbine, with an internal induction generator, at low to medium wind speeds. The proposed strategy controls the tip speed ratio, via the rotor angular speed, to an optimum point at which the efficiency constant (or power coefficient) is maximal for a particular blade pitch angle and wind speed. This control method allows for aerodynamic rotor power maximization without exact wind turbine model knowledge.