Model based control strategies for a class of nonlinear mechanical sub-systems

This paper presents a comparison between various control strategies for a class of mechanical actuators common in heavy-duty industry. Typical actuator components are hydraulic or pneumatic elements with static non-linearities, which are commonly referred to as Hammerstein systems. Such static non-linearities may vary in time as a function of the load and hence classical inverse-model based control strategies may deliver sub-optimal performance. This paper investigates the ability of advanced model based control strategies to satisfy a tolerance interval for position error values, overshoot and settling time specifications. Due to the presence of static non-linearity requiring changing direction of movement, control effort is also evaluated in terms of zero crossing frequency (up-down or left-right movement). Simulation and experimental data from a lab setup suggest that sliding mode control is able to improve global performance parameters

Fully variable valve actuation in large bore diesel engines

Diesel engine combustion process optimization has become increasingly important as environmental and economic issues are setting more strict conditions on engines. Best efficiency and lowest emission are not reached at the same time, and compromise between these is required. The more flexible the control of the combustion is, the more effective operation of the diesel engine is gained with required emission levels. Variable gas exchange valve actuation is one effective method of adjusting the combustion process, and it has already been successfully used for years in passenger cars. Variable actuation can be implemented either by a mechanical, electric or electro-hydraulic device. All constructions have pros and cons, and it depends on the application which is best suited for the case in question. The large bore diesel is a very challenging application where masses and forces are high, and required movement distances long. An electro-hydraulic actuation gives a benefit where almost full flexibility of the valve events is reached and full potential of the variable valve actuation can be used. Electro-hydraulic valve actuation is investigated in this study via simulations and measurements. The used hydraulic circuit and actuator construction has a strong effect on the performance of the valve actuation system. A 3-way controlled actuator gives the lowest energy consumption, and the control valve characteristic has a major role in overall performance. Right dimensioning of the gas exchange valve return spring is important. An energy consumption decrease of up to 20% could be achieved if the actuator was optimized. Because the actuation system is not mechanically linked on the engine piston position and the dynamics of the valve actuation system are challenging, a reliable and accurate control system is needed. Pure P-control is not good enough, and a state controller is too complex to use when environment variables change. An iterative learning feature can adapt automatically in different working points and it can also execute good tracking error through the whole gas exchange valve lift

Design and experimental investigation of rotational angle based tracking control

University of Minnesota Master of Science thesis. August 2014. Major: Mechanical Engineering. Advisor: Dr. Zongxuan Sun. 1 computer file (PDF); viii, 77 pages.This work investigates the tracking control in the rotational angle domain based on the time-varying internal model principle. The focus is to enable precise, reliable and computational efficient output tracking/disturbance rejection in the angle domain. To achieve better performance, existing approaches typically require more discrete samplings per revolution, which can drastically increase the controller order and also poses challenge for the stabilizer convergence. To address those issues, a varying sampling interval approach is proposed, where the control sampling rate is not fixed but optimized based on errors between sampling points, so that proper regulation performance can be achieved without significantly increasing the number of sampling points. Meanwhile, to improve the convergence rate of the tracking error, additional LMI constraints are added to the existing stabilizer synthesis. Through experimental study on a camless engine valve actuation system, the effectiveness of the proposed approaches is well demonstrated

Development of a New Fully Flexible Hydraulic Variable Valve Actuation System

The automotive industry has been in a marathon of advancement over the past decades. This is partly due to global environmental concerns about increasing amount of air pollutants such as NOx (oxides of nitrogen), CO (carbon monoxide) and particulate matters (PM) and decreasing fossil fuel resources. Recently due to stringent emission regulations such as US EPA (Environmental Protection Agency) and CARB (California Air Resource Board), improvement in fuel economy and reduction in the exhaust gas emissions have become the two major challenges for engine manufacturers. To fulfill the requirements of these regulations, the IC engines including gasoline and diesel engines have experienced significant modifications during the past decades. Incorporating the fully flexible valvetrains in production IC engines is one of the several ways to improve the performance of these engines. The ultimate goal of this PhD thesis is to conduct feasibility study on development of a reliable fully flexible hydraulic valvetrain for automotive engines. Camless valvetrains such as electro-hydraulic, electro-mechanical and electro-pneumatic valve actuators have been developed and extensively studied by several engine component manufacturers and researchers. Unlike conventional camshaft driven systems and cam-based variable valve timing (VVT) techniques, these systems offer valve timings and lift control that are fully independent of crankshaft position and engine speed. These systems are key technical enablers for HCCI, 2/4 stroke-switching gasoline and air hybrid technologies, each of which is a high fuel efficiency technology. Although the flexibility of the camless valvetrains is limitless, they are generally more complex and expensive than cam-based systems and require more study on areas of reliability, fail safety, durability, repeatability and robustness. On the contrary, the cam-based variable valve timing systems are more reliable, durable, repeatable and robust but much less flexible and much more complex in design. In this research work, a new hydraulic variable valve actuation system (VVA) is proposed, designed, prototyped and tested. The proposed system consists of a two rotary spool valves each of which actuated either by a combination of engine crankshaft and a phase shifter or by a variable speed servo-motor. The proposed actuation system offers the same level of flexibility as camless valvetrains while its reliability, repeatability and robustness are comparable with cam driven systems. In this system, the engine valve opening and closing events can be advanced or retarded without any constraint as well as the final valve lift. Transition from regenerative braking or air motor mode to conventional mode in air hybrid engines can be easily realized using the proposed valvetrain. The proposed VVA system, as a stand-alone unit, is modeled, designed, prototyped and successfully tested. The mathematical model of the system is verified by the experimental data and used as a numerical test bench for evaluating the performance of the designed control systems. The system test setup is equipped with valve timing and lift controllers and it is tested to measure repeatability, flexibility and control precision of the valve actuation system. For fast and accurate engine valve lift control, a simplified dynamic model of the system (average model) is derived based on the energy and mass conservation principles. A discrete time sliding mode controller is designed based on the system average model and it is implemented and tested on the experimental setup. To improve the energy efficiency and robustness of the proposed valve actuator, the system design parameters are subjected to an optimization using the genetic algorithm method. Finally, an energy recovery system is proposed, designed and tested to reduce the hydraulic valvetrain power consumption. The presented study is only a small portion of the growing research in this area, and it is hoped that the results obtained here will lead to the realization of a more reliable, repeatable, and flexible engine valve system

Comparison of linear control algorithms for a class of nonlinear mechanical actuators

This paper presents a comparison between various control strategies for a class of mechanical actuators common in heavy-duty industry. Typical actuator components are hydraulic or pneumatic elements with static nonlinearities, which are commonly referred to as Hammerstein systems. Such static nonlinearities may vary in time as a function of the load and hence classical inverse-model based control strategies may deliver sub-optimal performance. This paper investigates the ability of classical linear control strategies as lead, P, PI and PID control to satisfy tolerance interval for position error values, overshoot and settling time specifications. Due to the presence of static nonlinearity, control effort is also evaluated in terms of zero crossing frequency (up-down or left-right movement). Simulation and experimental data from a lab setup suggest that advanced control strategies may be needed to improve global performance parameters

Next generation automotive embedded systems-on-chip and their applications

It is a well known fact in the automotive industry that critical and costly delays in the development cycle of powertrain1 controllers are unavoidable due to the complex nature of the systems-on-chip used in them. The primary goal of this portfolio is to show the development of new methodologies for the fast and efficient implementation of next generation powertrain applications and the associated automotive qualified systems-on-chip. A general guideline for rapid automotive applications development, promoting the integration of state-of-the-art tools and techniques necessary, is presented. The methods developed in this portfolio demonstrate a new and better approach to co-design of automotive systems that also raises the level of design abstraction.An integrated business plan for the development of a camless engine controller platform is presented. The plan provides details for the marketing plan, management and financial data.A comprehensive real-time system level development methodology for the implementation of an electromagnetic actuator based camless internal combustion engine is developed. The proposed development platform enables developers to complete complex software and hardware development before moving to silicon, significantly shortening the development cycle and improving confidence in the design.A novel high performance internal combustion engine knock processing strategy using the next generation automotive system-on-chip, particularly highlighting the capabilities of the first-of-its-kind single-instruction-multiple-data micro-architecture is presented. A patent application has been filed for the methodology and the details of the invention are also presented.Enhancements required for the performance optimisation of several resource properties such as memory accesses, energy consumption and execution time of embedded powertrain applications running on the developed system-on-chip and its next generation of devices is proposed. The approach used allows the replacement of various software segments by hardware units to speed up processing.1 Powertrain: A name applied to the group of components used to transmit engine power to the driving wheels. It can consist of engine, clutch, transmission, universal joints, drive shaft, differential gear, and axle shafts

High-Compression-Ratio; Atkinson-Cycle Engine Using Low-Pressure Direct Injection and Pneumatic-Electronic Valve Actuation Enabled by Ionization Current and Foward-Backward Mass Air Flow Sensor Feedback

This report describes the work completed over a two and one half year effort sponsored by the US Department of Energy. The goal was to demonstrate the technology needed to produce a highly efficient engine enabled by several technologies which were to be developed in the course of the work. The technologies included: (1) A low-pressure direct injection system; (2) A mass air flow sensor which would measure the net airflow into the engine on a per cycle basis; (3) A feedback control system enabled by measuring ionization current signals from the spark plug gap; and (4) An infinitely variable cam actuation system based on a pneumatic-hydraulic valve actuation These developments were supplemented by the use of advanced large eddy simulations as well as evaluations of fuel air mixing using the KIVA and WAVE models. The simulations were accompanied by experimental verification when possible. In this effort a solid base has been established for continued development of the advanced engine concepts originally proposed. Due to problems with the valve actuation system a complete demonstration of the engine concept originally proposed was not possible. Some of the highlights that were accomplished during this effort are: (1) A forward-backward mass air flow sensor has been developed and a patent application for the device has been submitted. We are optimistic that this technology will have a particular application in variable valve timing direct injection systems for IC engines. (2) The biggest effort on this project has involved the development of the pneumatic-hydraulic valve actuation system. This system was originally purchased from Cargine, a Swedish supplier and is in the development stage. To date we have not been able to use the actuators to control the exhaust valves, although the actuators have been successfully employed to control the intake valves. The reason for this is the additional complication associated with variable back pressure on the exhaust valves when they are opened. As a result of this effort, we have devised a new design and have filed for a patent on a method of control which is believed to overcome this problem. The engine we have been working with originally had a single camshaft which controlled both the intake and exhaust valves. Single cycle lift and timing control was demonstrated with this system. (3) Large eddy simulations and KIVA based simulations were used in conjunction with flow visualizations in an optical engine to study fuel air mixing. During this effort we have devised a metric for quantifying fuel distribution and it is described in several of our papers. (4) A control system has been developed to enable us to test the benefits of the various technologies. This system used is based on Opal-RT hardware and is being used in a current DOE sponsored program

Discrete-time integral MRAC with minimal controller synthesis and parameter projection

Model reference adaptive controllers with Minimal Control Synthesis are effective control algorithms to guarantee asymptotic convergence of the tracking error to zero not only for disturbance-free uncertain linear systems, but also for highly nonlinear plants with unknown parameters, unmodeled dynamics and subject to perturbations. However, an apparent drift in adaptive gains may occasionally arise, which can eventually lead to closed-loop instability. In this paper, we address this key issue for discrete-time systems under L-2 disturbances using a parameter projection algorithm. A consistent proof of stability of all the closed-loop signals is provided, while tracking error is shown to asymptotically converge to zero. We also show the applicability of the adaptive algorithm for digitally controlled continuous-time plants. The proposed algorithm is numerically validated taking into account a discrete-time LTI system subject to parameter uncertainty, parameter variations and L-2 disturbances. Finally, as a possible engineering application of this novel adaptive strategy, the control of a highly nonlinear electromechanical actuator is considered. (C) 2015 The Franldin Institute. Published by Elsevier Ltd. All rights reserved.Postprint (author's final draft