Electrical Variable Valve Timing Research Articles

Review of Advancement in Variable Valve Actuation of Internal Combustion Engines

The increasing concerns of air pollution and energy usage led to the electrification of the vehicle powertrain system in recent years. On the other hand, internal combustion engines were the dominant vehicle power source for more than a century, and they will continue to be used in most vehicles for decades to come; thus, it is necessary to employ advanced technologies to replace traditional mechanical systems with mechatronic systems to meet the ever-increasing demand of continuously improving engine efficiency with reduced emissions, where engine intake and the exhaust valve system represent key subsystems that affect the engine combustion efficiency and emissions. This paper reviews variable engine valve systems, including hydraulic and electrical variable valve timing systems, hydraulic multistep lift systems, continuously variable lift and timing valve systems, lost-motion systems, and electro-magnetic, electro-hydraulic, and electro-pneumatic variable valve actuation systems.

A study on the improvement of the cam phase control performance of an electric continuous variable valve timing system using a cycloid reducer and BLDC motor

This paper discusses the control performance improvement for an electric-continuous variable valve timing (E-CVVT) system using a brushless direct current (BLDC) motor and cycloid reducer. Each component of the E-CVVT system was implemented with mathematical analysis, and the response performance of the E-CVVT system was determined based on the mathematical model of the cam shaft motion, cam profile, cycloid reducer, BLDC motor, and controller. To control the intake valve timing of the engine, a cycloid speed reducer with a high reduction ratio capable of amplifying the output torque of a small BLDC motor was implemented. The change in valve speed due to the rotation of the cam shaft was represented by the curves described by the vertical movement of the valve using the cam profile. A control performance test apparatus was constructed and the torque of the intake cam shaft was measured and applied to the analysis so that the phase of the cam shaft could be changed using the E-CVVT system. To analyze the operating characteristics of the E-CVVT system, the BLDC motors were modeled using Simulink. The E-CVVT system controls the phase angle of the intake cam shaft. When the E-CVVT system sets the target phase angle, the motor controller generates the optimal motor speed command. The intake cam phase response speed depends on the setting of each PID parameter that changes the phase of the cam shaft. Through analysis and vehicle-based experiments, we confirmed the improvement of the E-CVVT system response performance according to the change of the PID parameter.

Optimum shape design of a BLDC motor for electric continuous variable valve timing system considering efficiency and torque characteristics

Recently, environmental problems caused by global warming and exhaust gas have been increasing, leading governments all over the world to implement strict environmental regulations. For this reason, the automotive industry has begun working to increase fuel efficiency and reduce emissions. In addition, in order to improve the performance of engines implemented in internal combustion engines (ICEs) and hybrid electric vehicles (HEVs), electronic control actuators are becoming increasingly preferred over conventional mechanical parts. In particular, engine intake and exhaust valve timing techniques are critical to improving fuel economy and reducing vehicle emissions. Previously, a hydraulic continuous variable valve timing (CVVT) system was used for valve timing control. However, a disadvantage of this type of system is that the response speed is slow at low and high engine temperatures; these conditions limit the extent of automobile fuel efficiency improvement. Therefore, an electric variable valve timing system (E-CVVT) is being studied to overcome this disadvantage. In this paper, we propose a shape optimum design method for brushless DC (BLDC) motors used in an electric continuous variable valve timing (E-CVVT) system, which is employed in ICEs and HEVs. The proposed design aims to maximize the maximum torque and rated efficiency of BLDC motors, and minimize cogging torque. To select the optimal design variables, we chose to implement Latin hypercube sampling (LHS) to avoid duplication of sampling points. The characteristics of the sampling points obtained via the LHS method were calculated by using finite element (FE) analysis. In order to consider the nonlinearity of properties, we have created an approximate modeling technique that uses a radial basis function. Finally, genetic algorithms were used to determine the design parameters of the optimum model. The effectiveness of the proposed BLDC motor design process is verified by comparing the FE analysis and experimental results. Simulation and experimental results confirmed that the proposed optimized design procedure yields improved operating characteristics. Specifically, testing the proposed optimized design yielded a 16.7% increase in the maximum torque, and a 66.2% reduction in the cogging torque. In addition, the vehicle test confirmed that the proposed design was suitable for an E-CVVT system equipped with a BLDC motor. In addition, the optimum model of the BLDC motor was applied to the E-CVVT system. The response characteristics of the conventional hydraulic CVVT system and E-CVVT were compared via vehicle testing. The response speed of the E-CVVT system was 0.65 s faster than that of the CVVT system during the retard angle phase. Therefore, it was a 39.4% improvement in the response performance.

Static output-feedback robust gain-scheduling control with guaranteed [formula omitted] performance

This paper develops synthesis conditions for Static Output-Feedback (SOF) Gain-Scheduling (GS) control with guaranteed upper bound of H2 performance for continuous-time Linear Parameter Varying (LPV) systems, where measurements of scheduling parameters are affected by uncertainties or measurement noise. The control problem is solved through an iterative two-stage design procedure. In the first stage, parameter-dependent state-feedback controller is obtained to minimize upper-bound of the H2 performance. Then, this controller is used as input to the second stage to synthesize Robust Gain-Scheduling (RGS) static output-feedback gain with minimal H2 performance. In both stages, the synthesis conditions are given in terms of Parametrized Linear Matrix Inequalities (PLMIs). Robust SOF (parameter-independent) controller can be synthesized as special case of the developed synthesis conditions. Two examples have been presented to illustrate the benefit of the proposed approach. One is an academic numerical example from literature and the other one is a realistic LPV model of Electric Variable Valve Timing (EVVT) actuator for automotive engines that utilizes engine speed and vehicle battery voltage as time-varying scheduling parameters.

Experimental Study on an Electric Variable Valve Timing Actuator: Linear Parameter Varying Modeling and Control

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.

Model-Based Control for Mode Transition Between Spark Ignition and HCCI Combustion

While the homogeneous charge compression ignition (HCCI) combustion has its advantages of high thermal efficiency with low emissions, its operational range is limited in both engine speed and load. To utilize the advantage of the HCCI combustion, an HCCI capable spark ignition (SI) engine is required. One of the key challenges of developing such an engine is to achieve smooth mode transition between SI and HCCI combustion, where the in-cylinder thermal and charge mixture properties are quite different due to the distinct combustion characteristics. In this paper, a control strategy for smooth mode transition between SI and HCCI combustion is developed and experimentally validated for an HCCI capable SI engine equipped with electrical variable valve timing (EVVT) systems, dual-lift valves, and electronic throttle control (ETC) system. During the mode transition, the intake manifold air pressure is controlled by tracking the desired throttle position updated cycle-by-cycle; and an iterative learning fuel mass controller, combined with sensitivity-based compensation, is used to manage the engine torque in terms of net mean effective pressure (NMEP) at the desired level for smooth mode transition. Note that the NMEP is directly correlated to the engine output torque. Experiment results show that the developed controller is able to achieve smooth combustion mode transition, where the NMEP fluctuation is kept below 3.8% during the mode transition.

Modeling and Control of an Electric Variable Valve Timing System

This paper presents a model of an electric variable valve timing (EVVT) system and its closed-loop control design with experimental validation. The studied EVVT uses a planetary gear system to control the engine cam timing. The main motivation of utilizing the EVVT system is its fast response time and the accurate timing control capability. This is critical for the combustion mode transition control between the spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustion, where the engine cam timing needs to follow a desired trajectory to accurately control the engine charge and recompression process. A physics-based model was developed to study the characteristics of the EVVT system, and a control oriented EVVT model, with the same structure as the physics-based one, was obtained using closed-loop system identification. The closed-loop control strategies were developed to control the EVVT to follow a desired trajectory. Both simulation and bench test results are included.

SI and HCCI Combustion Mode Transition Control of an HCCI Capable SI Engine

The combustion mode transition between spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustion of an internal combustion (IC) engine is challenging due to the distinct engine operating parameters over the two combustion modes and the cycle-to-cycle residue gas dynamics during the mode transition. The control problem becomes even more complicated for a multicylinder engine without camless variable valve actuators. This paper studies the combustion mode transition problem of a multicylinder IC engine equipped with dual-stage valve lift and electrical variable valve timing (VVT) systems. Hardware-in-the-loop (HIL) simulations were used as a tool to develop and validate the proposed control strategies. Based on the HIL simulation results, this paper shows that smooth combustion mode transition can be realized in a few engine cycles. During the mode transition, a model-based linear quadratic tracking strategy was used to track the desired engine manifold pressure through the engine throttle control to maintain the engine AFR in a desired range; the fuel quantity of individual cylinder was controlled via the iterative learning; and engine spark was maintained for the SI-HCCI (or spark assistant) hybrid combustions during the combustion mode transition. The HIL simulations demonstrated the effectiveness of the developed control strategies under both steady state and transient engine operating conditions. As a result, it is feasible to have a smooth combustion mode transition for an HCCI capable SI engine equipped with dual-stage valve lift and electrical VVT systems.

1005 過給機付小排気量ガソリン機関への電動可変バルブタイミングの適用(GS6-1 熱工学)

1005 過給機付小排気量ガソリン機関への電動可変バルブタイミングの適用(GS6-1 熱工学)