Masoud Vaezi

Multiple-model adaptive estimation of a hydraulic wind power system

Nonlinear model of hydraulic wind power system operates on a wide spectrum of operating points such as random wind speed disturbances and applied control commands. Thus, one way to linearize this model is to use multiple linear models representing the whole range of operating points. This paper introduces a minimal number of fixed linear models in a multiple model adaptive estimation (MMAE) framework to reduce the state estimation error. System parameters such as pressures of the pump and motors can be estimated while the overall error in entire operating points is reduced. The algorithm is composed of a bank of Kalman filters, each of which is modeled to match particular real world operating condition. Simulation results demonstrate that the adaptive approach can optimally estimate the state variables in a wide range of operating points.

Piecewise Affine System Identification of a Hydraulic Wind Power Transfer System

Hydraulic wind power transfer systems exhibit a highly nonlinear dynamic influenced by system actuator hysteresis and disturbances from wind speed and load torque. This paper presents a system identification approach to approximate such a nonlinear dynamic. Piecewise affine (PWA) models are obtained utilizing the averaged nonlinear models of hysteresis in a confined space. State-space representation of PWA models is obtained over the allocated operating point clusters. The experimental results demonstrate a close agreement with that of the simulated. The experimental results and simulation show more than 91% match.

A model linearization technique for hydraulic wind power systems

Hydraulic wind turbines are highly nonlinear and work severely under variable disturbances such as load on the generators and the wind speed. For further analysis control implementation on these types of systems a suitable linearized model is needed. Due to the disturbances, the system has a wide range of operating points. Therefore, linearized models on different operating regimes will be needed. Finding the best operating points, to linearize the nonlinear system at, can improve the accuracy of the linearization as well as the stability of the system. This paper propose a new automatic algorithm to indicate the suitable operating points and linearized models.

Modeling of a Hydraulic Wind Power Transfer Utilizing a Proportional Valve

Hydraulic circuits can transfer remarkable amounts of energy in the desired direction without taking large space. To implement this technology for harvesting the energy of wind appropriately, models of the system are required. Hydraulic wind power technology has the benefits of eliminating expensive and bulky variable ratio gearbox and its costly maintenance, while enabling the integration of multiple wind turbines in a single generation unit. In this paper, the dynamics of different hydraulic elements are studied, nonlinearities are taken into account, pressure dynamics in different parts of the system are studied, and the motor load effects are considered. Based on these considerations, a novel nonlinear state-space representation of the system is introduced. Results of the mathematical model and the experimental data are compared to verify the proposed model. The comparison demonstrated that the mathematical model captures all major characteristics of the hydraulic circuit and can model the system behavior under different operating conditions.

Control of a hydraulic wind power transfer system under disturbances

Hydraulic wind power transfer systems deliver the captured energy by the blades to the generators differently and through an intermediate medium i.e. hydraulic fluid. This paper develops a control system for a nonlinear model of hydraulic wind power transfer systems. To maintain a fixed frequency electrical voltage by the system, the generator should remain at a constant rotational speed. The fluctuating wind speed from the upstream applies considerable disturbances on the system. A controller is designed and implemented to regulate the flow in the proportional valve and as a consequence the generator maintains its constant speed compensating for low wind speed and high wind speed disturbances. The controller is applied to the system by utilizing MATLAB/Simulink.

Indirect adaptive control of droplet dispensing in digital microfluidic systems

Digital microfluidics systems require advanced controllers to operate accurately since their parameters are subjected to change in environment and over time. Due to imperfect manufacturing processes, their fabricated system parameters may become different from the destined values. Hence, estimation based controllers are required to identify the system parameters. The electrowetting on dielectric can be precisely controlled to dispense desirable and repeatable droplets. However, the system parameters and their variation over time makes the control system challenging. This paper describes the application of an indirect adaptive trajectory controller for digital Pico-Droplet dispensing system. Forgetting factor recursive least square estimator is used to estimate the system parameters including capacitance and resistance of the occupying droplet between electrodes. Indirect adaptive technique is used to measure and control the droplet volume on the dispensing electrodes. Simulations of the estimator, tracking performance of dispensed droplet volume and the controllers control effort are provided to demonstrate an accurate and high performance control approach.

Hydraulic Wind Power Plants: A Nonlinear Model of Low Wind Speed Operation

The structure of hydraulic wind power plants involves one or several high-pressure hydraulic pumps and a central power generation unit to combine the energy from wind turbines. As the wind speed drops, the energy generation may not be significant enough to run the main generator. Therefore, an auxiliary generator generates power for the storage devices. The system operation at low wind speed is highly nonlinear, as the power generation is not significant. This paper introduces a nonlinear model of hydraulic elements and offers the nonlinear dynamics of system operation at low speed. Nonlinear state-space representation of the hydraulic wind energy transfer is presented and validated by experimental implementations.

Optimum Adaptive Piecewise Linearization: An Estimation Approach in Wind Power

This paper introduces an effective piecewise linearization technique to obtain an estimation of nonlinear models when their input-output domains include multidimensional operating points. The algorithm of a forward adaptive approach is introduced to identify the effective operating points for model linearization and adjust their domains for the maximum coverage and the minimum model linearization error. The technique obtains a minimum number of linearized models and the continuity of their domains. The algorithm also yields global minimum model linearization error. The introduced algorithm is formulated for a wind power transfer system for a 2-D set of input domains. The linearization error can be arbitrarily minimized in exchange for a higher number of models. The results demonstrate a significant improvement in the linearization of nonlinear models.

Experimental control of a hydraulic wind power transfer system under wind and load disturbances

Hydraulic wind power transfer systems deliver the captured energy by the blades to the generators through an intermediate medium i.e. hydraulic fluid. This paper develops a control system for an experimental setup of hydraulic wind power transfer systems. To maintain a fixed frequency electrical voltage by the system, the generator should remain at a constant rotational speed regardless of the wind speed. The fluctuating wind speed from the upstream, and the load variations from the downstream apply considerable disturbances on the system. A controller is designed and implemented to regulate the flow in the proportional valve and as a consequence the generator maintains its constant speed compensating for load and wind turbine disturbances. The control system is applied to the experimental prototype by utilizing MATLAB/Simulink and dSPACE 1104 fast prototyping hardware.

IMC-PID traction control system for an automobile via engine torque control

Trends in the automotive control systems are toward more comprehensive and electronic control. The objective of this paper is to study the effectiveness of Internal Model Control PID (IMC-PID) method to develop a traction control system based on engine torque control for an automobile. A plant model is developed based on the governing equations and implemented in MATLAB. This is then captured in a Simulink model and simulated to evaluate performance of the open-loop system for both step and ramp inputs. A proportional-integral (PI)-type controller is then developed using IMC-PID tuning method to improve closed-loop system response. Finally, potential future applications and research opportunities are identified.