Linear Parameter-Varying Model of an Electro-Hydraulic Variable Valve Actuator for Internal Combustion Engines (original) (raw)
Related papers
2017 13th IEEE International Conference on Control & Automation (ICCA), 2017
This paper presents detailed modeling of a novel electro-hydraulic variable valve actuator for internal combustion engines that is capable of continuously varying valve timing and dual-lift. First, nonlinear mathematical system model is developed component-by-component, considering electromagnetic, mechanical, and fluid dynamics, time delay and time-varying parameters. Second, in order to develop a control-oriented model, order of the full order nonlinear model is reduced. Calibration and validation experiments are conducted for the reduced order nonlinear model using a test bench. The key time-varying parameters are determined using the test data through the Least-Squares optimization. With the identified and calibrated model parameters, the simulation results are in good agreement with the experimental ones under different operational conditions. Recently, intensive research has been focused on camless VVA systems for internal combustion engines due to their fully flexible valve timing, duration and lift. The camless VVA system can be divided into three main groups: the electromagnetic , electro-hydraulic, and electro-pneumatic actuators. The electromagnetic VVA systems provide fully flexible valve timing and duration with relatively high efficiency, but its repeatability is highly sensitive to valve opening load with fairly high electric power demand [4]. Due to the nonlinear electromagnetic force, complicated real-time control algorithms are often required for soft-seating control and lift control [4]-[6].
A Dynamic Model of an Electropneumatic Valve Actuator for Internal Combustion Engines
Journal of Dynamic Systems, Measurement, and Control, 2010
This paper presents a detailed model of a novel electropneumatic valve actuator for both engine intake and exhaust valves. The valve actuator’s main function is to provide variable valve timing and variable lift capabilities in an internal combustion engine. The pneumatic actuation is used to open the valve and the hydraulic latch mechanism is used to hold the valve open and to reduce valve seating velocity. This combination of pneumatic and hydraulic mechanisms allows the system to operate under low pressure with an energy saving mode. It extracts the full pneumatic energy to open the valve and use the hydraulic latch that consumes almost no energy to hold the valve open. A system dynamics analysis is provided and followed by mathematical modeling. This dynamic model is based on Newton’s law, mass conservation, and thermodynamic principles. The air compressibility and liquid compressibility in the hydraulic latch are modeled, and the discontinuous nonlinearity of the compressible f...
Journal of Dynamic Systems, Measurement, and Control, 2017
This paper presents experimental investigation results of an electric variable valve timing (EVVT) actuator using linear parameter varying (LPV) system identification and control. For the LPV system identification, a number of local system identification tests were carried out to obtain a family of linear time-invariant (LTI) models at fixed engine speed and battery voltage. Using engine speed and battery voltage as time-varying scheduling parameters, the family of local LTI models is translated into a single LPV model. Then, a robust gain-scheduling (RGS) dynamic output-feedback (DOF) controller with guaranteed H∞ performance was synthesized and validated experimentally. In contrast to the vast majority of gain-scheduling literature, scheduling parameters are assumed to be polluted by measurement noises and the engine speed and battery voltage are modeled as noisy scheduling parameters. Experimental and simulation results show the effectiveness of the developed approach.
SAE International Journal of Engines, 2011
Significant improvement in fuel consumption, torque delivery and emission could be achieved through flexible control of the valve timings, duration and lift. In most existing electrohydraulic variable valve actuation systems, the desired valve lift within every engine cycle is achieved by accurately controlling of the solenoid-valve opening interval; however, due to slow response time, precision control of these valves is difficult particularly during higher engine speeds. In this paper a new lift control strategy is proposed based on the hydraulic supply pressure and flow control. In this method, in order to control the peak valve lift, the hydraulic pump speed is precisely controlled using a two-input gearbox mechanism. This eliminates the need for precision control of the solenoid valves opening interval within every cycle. To achieve a smooth control signal, it is worthwhile to control the maximum valve lift within few engine cycles rather than every cycle; therefore, instead of using the governing nonlinear differential equations of the mechanism, a novel average model of the system is developed based on energy conservation equations. A non-linear sliding mode controller (SMC) is also designed based on the developed average model and the boundary layer method is used to eliminate the chattering problem. The performance of the proposed controller is then examined through some simulations. Moreover, the new lift control technique is implemented experimentally by reconfiguration of the existing electro-hydraulic valve system prototype and empirical results are then compared with those obtained from the simulations.
2011
Significant improvement in fuel consumption, torque delivery and emission could be achieved through flexible control of the valve timings, duration and lift. In most existing electrohydraulic variable valve actuation systems, the desired valve lift within every engine cycle is achieved by accurately controlling of the solenoid-valve opening interval; however, due to slow response time, precision control of these valves is difficult particularly during higher engine speeds. In this paper a new lift control strategy is proposed based on the hydraulic supply pressure and flow control. In this method, in order to control the peak valve lift, the hydraulic pump speed is precisely controlled using a two-input gearbox mechanism. This eliminates the need for precision control of the solenoid valves opening interval within every cycle. To achieve a smooth control signal, it is worthwhile to control the maximum valve lift within few engine cycles rather than every cycle; therefore, instead of using the governing nonlinear differential equations of the mechanism, a novel average model of the system is developed based on energy conservation equations. A non-linear sliding mode controller (SMC) is also designed based on the developed average model and the boundary layer method is used to eliminate the chattering problem. The performance of the proposed controller is then examined through some simulations. Moreover, the new lift control technique is implemented experimentally by reconfiguration of the existing electro-hydraulic valve system prototype and empirical results are then compared with those obtained from the simulations.
Design and Development of a Mechanical Variable Valve Actuation System
Compromises inherent with fixed valve lift and event timing have prompted engine designers to consider Variable Valve Actuation (VVA) systems for many decades. In recent years, some relatively basic forms of VVA have been introduced into production engines. Greater performance and driveability expectations of customers, more stringent emission regulations set by government legislators, and the mutual desire for higher fuel economy are increasingly at odds. As a solution, many OEM companies are seriously considering large-scale application of higher function VVA mechanisms in their next generation vehicles.
Paper 01.Design and Optimization of 2-stage Variable Valve Actuation Mechanism for Diesel Engines
International Engineering Research Journal, 2015
The desire for higher fuel economy, improved performance and drivability expectations of customers from engines are gradually increasing along with stringent emission regulations set by the government. There is customer demand for 4-wheeler vehicle having good power, torque and better fuel economy throughout the speed range of vehicle and an implied environmental need of improved emission characteristics. Variable Valve Actuation (VVA) has been applied to many engines in order to enhance the engine performance. Many engine manufacturing companies have started the application of variable valve actuation mechanism in their next generation vehicles. The VVA is a generalized term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine.There are various ways to improve to the performance of engine some of which are; supercharging, turbocharging, variable compression ratio, variable intake system geometry, variable valve timing and lift etc.In this work we have concentrated on variable valve timing and lift for diesel engines. This work presents a novel two-step VVA mechanism to facilitate variation in valve timing and lift of base engine. Thus this mechanism helps to divide the operating speed range of engine into two zones i.e. low speed and high speed zone and setting a switch over point, thus helping the engine breath effectively. Keywords —Variable Valve Actuation, Valve Lift, Speed Zone, Valve Event.
Synthesis and analysis of a variable valve lift and timing mechanism
The paper is focused on the synthesis and analysis of a variable valve lift and timing (VVLT) mechanism, used to enhance the fuel consumption in the low part loads operation. This mechanism is self-regulated thanks to a hydro-mechanical system, which is the subject of a French patent and allows a continuously intake valve lift and opening variation. The synthesis, which consisted in finding out the required intake cam profile starting from an imposed intake valve law, is performed analytically. Then, by using the obtained cam profile, it has been checked out via Catia software whether the resulted intake valve law coincides with the imposed law used when performing the analytical synthesis. Once this validated, the analysis of the VVLT mechanism is done by using Catia software. Therefore, the envelope of the valve lifts for the entire engine’s operation is found and explained. This work is being developed thanks to the financial support of the Romanian Council for Scientific Researc...
Reduction of Valve Seating Velocity in Electro Hydraulic Valve Actuation System
The engine has two valves one in the inlet and other in the outlet. The valve timing is a significant thing of the engine. The valve actuation system is of two different types (1) Cam Based and (2) Camless Based actuation system. Initially valves were actuated by cam based system. Since these systems are mechanical, the performance diminishes overtime. To overcome this disadvantage and for accurate valve timing came the cam less actuation system. The electro hydraulic variable valve actuation system is one of the popular cams less actuation system in which the rotary spool valve is controlled by PI controller. The valve seating velocity is defined as the linear motion of the valve. The valve seating velocity is not optimized for good performance in the real engine. Hence we propose a system to optimize the valve seating velocity. The proposed system is modeled using bond graphs and the outputs are verified.
Modelling of Electromechanical Control of Camless Internal Combustion Engine Valve Actuator
2013
This paper presents the modeling and control of internal combustion engine valve actuator mechanism, using variable valve actuation system, like electromechanical valve actuation system to flexibly control the engine valve timing and lift profile. In this paper, the prospects and possibilities of an electromechanical control of internal combustion engine valve to eliminate choking and backflow has been theoretically and technically analyzed. In principle, optimality in every engine condition can be attained by Camless valve trains. Electromechanical valve actuators are very promising in this context. A mathematical model of the system is developed to evaluate the effect of each of the design parameters, starting from the modeling of a single stage pressure reducing valve, the concept of modeling a real three land three way solenoid valve actuator for the clutch system in the automatic transmission is presented and these were validated with data provided from experiments with the rea...