Yildiray Yildiz - Profile on Academia.edu (original) (raw)

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Papers by Yildiray Yildiz

IEEE Transactions on Control Systems Technology, 2011

The paper presents an application of a recently developed adaptive posicast controller (APC) for ... more The paper presents an application of a recently developed adaptive posicast controller (APC) for time-delay systems to the idle speed control (ISC) problem in spark ignition (SI) internal combustion (IC) engines. The objective is to regulate the engine speed to a prescribed set-point in the presence of accessory load torque disturbances such as those due to air conditioning and power steering. The adaptive controller, integrated with the existing proportional spark controller, is used to drive the electronic throttle actuator. We present both simulation and experimental results demonstrating the performance improvement by employing the adaptive controller. We also present the modifications and improvements to the controller structure which were developed during the course of experimentation to solve specific problems. In addition, the potential for the reduction in calibration time and effort which can be achieved with our approach is discussed.

This paper treats the control of engine air-to-fuel ratio from the perspective of adaptive contro... more This paper treats the control of engine air-to-fuel ratio from the perspective of adaptive control of time-delay systems. High accuracy of engine air-to-fuel ratio control is required to meet stringent emissions regulations. Two adaptive controller designs are considered. The first design is based on feed-forward adaptation while the second design is based on both feedback and feedforward adaptation incorporating the developed adaptive posicast controller. The two adaptive designs are compared with the baseline controller using simulations and vehicle experiments.

Control Engineering Practice, 2010

This paper presents the control of Spark Ignition (SI) Internal Combustion (IC) engine Fuel-to-Ai... more This paper presents the control of Spark Ignition (SI) Internal Combustion (IC) engine Fuel-to-Air Ratio (FAR) using an adaptive control method of time-delay systems. The objective is to maintain the in-cylinder FAR at a prescribed set point, determined primarily by the state of the Three-Way Catalyst (TWC), so that the pollutants in the exhaust are removed with the highest efficiency. The FAR controller must also reject disturbances due to canister vapor purge and inaccuracies in air charge estimation and wallwetting (WW) compensation. Two adaptive controller designs are considered. The first design is based on feedforward adaptation while the second design is based on both feedback and feedforward adaptation incorporating the recently developed Adaptive Posicast Controller (APC). Both simulation and experimental results are presented demonstrating the performance improvement by employing the APC. Modifications and improvements to the ¦ Corresponding author.

Automatica, 2010

In this paper, we present an Adaptive Posicast Controller that deals with parametric uncertaintie... more In this paper, we present an Adaptive Posicast Controller that deals with parametric uncertainties in linear systems with delays. It is assumed that the plant has no right half plane zeros and the delay is known. The adaptive controller is based on the Smith Predictor and Finite-Spectrum Assignment with time-varying parameters adjusted online. A novel Lyapunov-Krasovskii functional is used to show semi-global stability of the closed-loop error equations. The controller is applied to engine fuelto-air ratio control. The implementation results show that the Adaptive Posicast Controller dramatically improves the closed loop performance when compared to the case with the existing baseline controller.

Adaptive Idle Speed Control for Internal Combustion Engines

The paper presents an application of a recently developed adaptive posicast controller for time-d... more The paper presents an application of a recently developed adaptive posicast controller for time-delay systems to the idle speed control (ISC) problem in internal combustion (IC) engines. The objective is to regulate the engine speed at a prescribed set-point in the presence of accessory load torque disturbances such as air conditioning and power steering. The adaptive controller, integrated with the existing proportional spark controller, is used to drive the electronic throttle as an actuator. We present both simulation and experimental results which demonstrate the potential of the adaptive controller to improve the performance. In addition, the reduction in calibration time and effort which can be achieved with our approach is discussed.

This paper proposes a control allocation system that can detect and compensate the phase shift be... more This paper proposes a control allocation system that can detect and compensate the phase shift between the desired and the actual total control effort due to rate limiting of the actuators. Phase shifting is an important problem in control system applications since it effectively introduces a time delay which may destabilize the closed loop dynamics. A relevant example comes from flight control where aggressive pilot commands, high gain of the flight control system or some anomaly in the system may cause actuator rate limiting and effective time delay introduction. This time delay can instigate Pilot Induced Oscillations (PIO), which is an abnormal coupling between the pilot and the aircraft resulting in unintentional and undesired oscillations. The proposed control allocation system reduces the effective time delay by first detecting the phase shift and then minimizing it using constrained optimization techniques. Flight control simulation results for an unstable aircraft with inertial cross coupling are reported, which demonstrate phase shift minimization and recovery from a PIO event.

This paper proposes a control allocation technique that can help pilots recover from pilot induce... more This paper proposes a control allocation technique that can help pilots recover from pilot induced oscillations (PIO). When actuators are rate-saturated due to aggressive pilot commands, high gain flight control systems or some anomaly in the system, the effective delay in the control loop may increase depending on the nature of the cause. This effective delay increase manifests itself as a phase shift between the commanded and actual system signals and can instigate PIOs. The proposed control allocator reduces the effective time delay by minimizing the phase shift between the commanded and the actual attitude accelerations. Simulation results are reported, which demonstrate phase shift minimization and recovery from PIOs. Conversion of the objective function to be minimized and constraints to a form that is suitable for implementation is given.

Neuro sliding mode control of timing belt servo-system

ABSTRACT

IEEE Industrial Electronics Magazine, 2007

In this paper a method allowing to merge good features of the sliding mode control (SMC) and Neur... more In this paper a method allowing to merge good features of the sliding mode control (SMC) and Neural network (NN) design is presented. Design is performed by applying NN to minimize cost function selected to depend on the distance from sliding mode manifold thus providing that NN controller enforces sliding mode motion in a closed loop system. It has been proven that selected cost function has global minima and that selection of the NN weights guaranty that the global minima is reached and then the sliding mode conditions are satisfied, thus closed loop motion is robust against parameter changes and the disturbances. For the controller design the system states and the nominal value of the control input matrix are used. The design for both MIMO and SISO systems is discussed. Due to the structure of the (M)ADALINE network used in the control calculation the proposed algorithm can be also interpreted as a sliding mode based control parameters adaptation scheme The stability proofs are given and the controller performance is verified by experimental results.

Neuro-sliding mode controller for MIMO systems

In this paper, the previously proposed neuro-sliding mode controller for SISO systems by the auth... more In this paper, the previously proposed neuro-sliding mode controller for SISO systems by the authors is modified for MIMO case. The structure benefits from the power of sliding mode control and nonlinear function approximation ability of the neural networks. The controller is a two layer feed-forward neural network and weight updates are done using backpropagation algorithm. The error function that is introduced to the neural network is such that the states of the system are restricted to belong to a certain manifold in state space. Different from the works done until now, in this work the aim is not calculating the equivalent control but instead finding the control input by just minimizing a certain error function. Simulation results demonstrate the performance of the controller.