Search

The camless valve system is able to provide flexible engine-valve profiles (timing, duration, lift, etc.) to optimize the performance of internal combustion engines. To provide a precise valve profile of an electro-hydraulic variable valve actuator and achieve the desired engine performance, an optimal tracking controller for the valve-rising duration, a key valve profile parameter, is presented in this paper. An event-by-event nonlinear model, connecting the system supply pressure dynamics to the valve-rising duration, is developed and linearized along the desired valve-rising trajectory. Based on the trajectory linearization, a receding horizon linear–quadratic tracking (LQT) controller is designed along with a Kalman optimal state estimation. The equilibrium control resulted from the model linearization is used as the LQT feedforward control. The control performance is compared with that of baseline controllers through both simulation study and bench tests. The transient and steady-state validation results confirm the effectiveness of proposed control scheme. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, the robust input covariance constraint (ICC) control problem with polytopic uncertainty is solved using convex optimization with linear matrix inequality (LMI) approach. The ICC control problem is an optimal control problem that optimizes the output performance subjected to multiple constraints on the input covariance matrices. This control problem has significant practical implications when hard constraints need to be satisfied on control actuators. The contribution of this paper is the characterization of the control synthesis LMIs used to solve the robust ICC control problem for polytopic uncertain systems. Both continuous- and discrete-time systems are considered. Parameter-dependent and independent Lyapunov functions have been used for robust ICC controller synthesis. Numerical design examples are presented to illustrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, a family of linear models previously obtained from a series of closed-loop system identification tests for a variable valve timing cam phaser system is used to design a dynamic gain-scheduling controller. Using engine speed and oil pressure as the scheduling parameters, the family of linear models was translated into a linear parameter varying (LPV) system. An observer-based gain-scheduling controller for the LPV system is then designed based on the linear matrix inequality technique. A discussion on weighting function selection for mixed \cal H2/\cal H\infty controller synthesis is presented, with an emphasis placed on examining various frequency responses of the system. Test bench results show the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Electro-pneumatic valve actuators are used to eliminate the cam shafts of a traditional internal combustion engine. They are used to control the opening timing, duration, and lift of both intake and exhaust valves. In order to develop model-based control strategies, a control oriented model was developed by piecewisely linearizing the physics-based nonlinear system model. In this paper, an adaptive valve lift control strategy was developed to improve the intake valve lift repeatability. The model reference adaptive system identification technique was employed to estimate system parameters needed for generating feedforward control signals for the closed-loop control scheme. The closed-loop lift control strategies, along with the model reference feedforward control, were developed and implemented in a prototype controller, and validated on a valve test bench with multiple reference valve lifts at both 1200 and 5000 r/min engine speeds. The experiment results showed that the actual valve lift reached the reference lift within 0.5 mm of lift error in one cycle at 1200 r/min and in two cycles at 5000 r/min. The maximum steady-state lift errors were less than 0.4 mm at high valve lift and less than 1.3 mm at low valve lift. Furthermore, the closed-loop valve lift control improved valve lift repeatability with more than 30% reduction of standard deviation over the open-loop control. [ABSTRACT FROM AUTHOR]

This paper applies integrated system modeling and control design process to a continuously variable valve timing (VVT) actuator system that has different control input and cam position feedback sample rates. Due to high cam shaft torque disturbance and high actuator open-loop gain, it is also difficult to maintain the cam phase at the desired constant level with an open-loop controller for system identification. As a result, multirate closed-loop system identification becomes necessary. For this study, a multirate closed-loop system identification method, pseudo-random binary signal q-Markov Cover, was used for obtaining linearized system models of the nonlinear physical system at different engine operational conditions: and output covariance constraint (OCC) controller, an H2 controller, was designed based upon the identified nominal model and evaluated on the WT test bench. Performance of" the designed OCC controller was compared with that of the well-tuned baseline proportional-integral (PI) controller on the test bench. Results show that the OCC controller uses less control effort and has significant lower overshoot than those of PI ones. [ABSTRACT FROM AUTHOR]

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 flow due to choking is carefully considered. Provision is made for the nonlinear motion of the mechanical components due to the physical constraints. Validation experiments were performed on a Ford 4.6 l four-valve V8 engine head with different air supply pressures and different solenoid pulse inputs. The simulation responses agreed with the experimental results at different engine speeds and supply air pressures. [ABSTRACT FROM AUTHOR]