1,721,058 research outputs found
New Tuning Rules for Fractional PI^alfa Controllers
No full textThis paper describes a new tuning method for fractional PI^α controllers. The main theoretical contribution of the paper is the analytical solution of a nonlinear function minimization problem, which plays a central role in deriving the tuning formulae. These formulae take advantage of the fractional order α to offer an excellent tradeoff between dynamic performances and stability robustness. Finally, a position control is implemented to compare laboratory experiments with computer simulations. The comparison results show the good performance of the tuning formulae
Near Optimum Control of a Full Car Active Suspension System
No full textIn this paper, a near-optimum control strategy applied to a full car model equipped with an active suspension system is presented. The control law is based on a reduced order model obtained by means of a modal aggregation method, achieving a compromise between computational effort in deriving the control law and system performances. To assess the controller performances, a virtual prototype of the suspension system is developed by using AMESim, an advanced fluid-mechanic developing tool. The virtual prototype could be assumed as a reliable model of the real system enabling to perform safer and cheaper tests than using the real system. Simulation results show the effectiveness of the approach
Loop-Shaping and Easy Tuning of Fractional-Order Proportional Integral Controllers for Position Servo Systems
No full textThis paper develops simple formulas directly relating performance specifications to control parameters of fractional-order proportional integral (PI) controllers for position servo systems. With the proposed controller settings, the open-loop frequency response achieves a good phase margin, that remains constant in a wide range around the crossover frequency. Consequently, the tuning results in high stability robustness to gain variations in the loop. Moreover, the fractional order integration also leads to limited overshoot and short settling time. Laboratory experiments confirm simulation results
Fuzzy Adaptive Control of a Variable Geometry Turbocharged Diesel Engine
No full textA fuzzy control approach for the adjustment of the boost pressure of a variable geometry, turbine (VGT) supercharged diesel engine is proposed. The VGT adapts the boost pressure to the target reference for different engine speeds by adjusting the turbine blades, resulting in a reduction of both fuel consumption and gas emissions, while preserving efficiency. We design an adaptive fuzzy control law according to the following steps: first, a standard PI controller is devised, then an equivalent fuzzy controller is built, finally the fuzzy controller is made nonlinear by tuning its input/output parameters using an optimization algorithm. Further, modification of the membership functions is investigated. A large number of simulations on a zero-dimensional model of the engine prove the effectiveness of the proposed control strategy with reference to stability and transient performance in comparison with standard PI techniques
Pressure Control of CNG Engines by Noninteger Order Controllers: a New Trend in Application of Fractional Calculus to Automotive Systems
No full textThe massive use of electronic control in automotive vehicles improved performance,comfort, safety and reduced pollutant emissions and consumption. In particular, the accurate control of the fuel injected into cylinders allowed the common rail fuel injection system to increase engine performance while reducing emissions, noise and fuel consumption. In this context, compressed natural gas (CNG) engine systems can further reduce emissions to adhere to environmental policy regulations. However, the injection process is strongly non linear, time variant and highly coupled, so suitable control systems must be designed to guarantee the desired performance. This chapter describes how to synthesize and realize non integer order controllers for pressure control in common rail injection systems of CNG engines. The realization is relatively simple and cheap, as required by the industrial application. Namely, not only low sensitivity to parameter variations and load disturbances mustbe achieved, but also a limited cost with respect to implementation by consolidated PID controllers.The CNG common rail injection system includes: a tank storing high pressure gas;a main chamber and a control chamber; a solenoid valve; an electronic control unit; a common rail and electro injectors. The tank feeds the downstreamcircuit. The main and control chambers are separated by a moving piston. Both chambers receive fuel from the tank and send it to the common rail, which is a constant volume accumulator connected to the electro injectors.The inlet flow to the main chamber is regulated by a shutter that is integral with the piston, whose position depends on the equilibrium of the pressures acting on its surfaces. Adjusting the pressure in the control circuit by the solenoid valve regulates the main chamber inflow. Moreover, as the main chamber and the common railhave almost equal pressures, accurate metering of the injected fuel is allowed by setting the injection timings at the same time.This work reports recent advancements in the design and simulation of switched fractional order PI controllers, in which the integral action is of non integer order.Performance, robustness and disturbance rejection are tested by simulation of virtual prototypes based on non linear models. The basic idea is to perform a loop shaping of the open-loop transfer function to obtain frequency domain performance specifications and achieve an optimal feedback system. To this aim, the fractional integrator is profitably used and robuststability of the closed loop system is guaranteed by a D decomposition method. There are several benefitsof the design approach. Closed formulas determine the controller gains by frequency domain specifications and can be used for an automatic synthesis of the controller. Moreover, the realization of the noninteger operator is by an efficient approximationmethod that prevents numerical problems and leads to a rational transfer function characterized by interlaced minimumphase zeros and stable poles, so that a reduced approximation error is obtained and easy implementation is possible. To conclude, the non integer order controllers allow higher accuracyin metering the injected fuel and promptness in setting the rail pressure to the desired reference values
A Control-Oriented Model of a Common Rail Injection System for Diesel Engines
No full textThis paper presents a model of a Common Rail injection system for diesel engines. The model is derived by considering the components of the system as control volumes and applying elementary fluid dynamics and mechanics laws. Suitable simplifications are introduced, to make the model adequate for control purposes, trading off between computational effort and accuracy. The model obtained is a fifth order nonlinear one, in state-space representation, and relies on simple, well defined, geometric parameters of the system. The results obtained are compared with data collected on an experimental setup, and with those obtained through the fluid dynamic simulation AMESI
A new IM vector control scheme with two fuzzy logic controllers
No full textThis paper deals with the design of two fuzzy logic controllers (FLCs) for vector-controlled induction motor (IM) drives. Industrial vector drives employ the cascade control scheme, with four PI controllers, to improve dynamic performances. A suitable design of two FLCs permits one to achieve the performances of the cascaded control without using subordinated control loops. FLCs can operate with non-homogeneous inputs therefore they can regulate more than one variable at the same time: the first FLC regulates both speed and stator current generating torque, the second FLC regulates both flux and stator current generating flux. Original criteria based on physical considerations, to determine the input and output gains instead of using the trial and error procedure, are presented. The simplicity of the new FLC-based scheme, together with the given design formulas, reduce the control system development time. The control scheme has been implemented on both a floating point 400MHz Motorola PPC and on a fixed point 20MHz Infineon C167 μcontroller. The computation power in the former case and the use of the fired-rules-hyper-cube (FRHC) approach in the latter one have allowed the μcontrollers to execute the code of two FLCs in a time comparable with that needed by four PI controllers. Details about the μcontroller implementation together with experimental results that prove the effectiveness of the novel IM vector control scheme are give
Modeling and Predictive Control of a New Injection System for Compressed Natural Gas Engines
No full textIn internal combustion engines equipped with the common rail injection system the accurate metering of the air/fuel mixture strictly depends on the pressure regulation. Accuracy in metering is difficult to be achieved especially for compressed natural gas (CNG) injection systems, as the gas compressibility makes the fuel delivery process more complex. Since the controller design requires a model of the injection system, this paper presents a physics-based state-space model of an innovative CNG injection system. The model parameters only depend on well defined geometrical data and fuel properties. Comparing simulation and experimental results in different operating conditions validates the model. Further, the proposed model is used for designing a generalized predictive controller for the injection pressure regulation, which is implemented in few steps. Experimental results show the effectiveness of the proposed approac
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