Greg Shaver

• PhD
• Professor (Associate) at Purdue University West Lafayette

In Indiana, roadside mowing operations span over 11,000 miles and are performed by contracted crews using tractors and hand-held trimmers, exposing workers to significant safety risks, including reported casualties. Autonomous mowers offer a promising solution to enhance safety, but large-scale deployment requires rigorous testing to ensure reliabi...

Roadside mowing is a necessary, high-risk occupation to ensure visibility for on-road traffic. In Indiana, contractors are hired by the Indiana Department of Transportation (INDOT) to mow over 11,000 miles of roadsides using tractors with flex-wing mowers and hand-held string trimmers. Operations have significant risks to all crew members. Autonomo...

Off-road vehicles are emphasizing brake thermal efficiency improvements to meet upcoming diesel emission standards set by the California Air Resources Board (CARB), aiming for enhanced engine and vehicle component efficiency. CARB is implementing regulations demanding a 90% reduction in oxides of nitrogen (NO x ) emissions compared to current EPA T...

Accurate estimation and prediction of engine gas exchange system and in-cylinder conditions are critical for spark-ignited engine control and diagnostic algorithm development. In this paper, a physically-based, control-oriented model for a 2.8 l turbocharged, variable valve timing (VVT) and low pressure (LP) exhaust gas recirculation (EGR)-utilizin...

This paper describes the development and experimental validation of a novel grain unloading-on-the-go automation system (automatic offloading) for agricultural combine harvesters. Unloading-on-the-go is desirable during harvest, but it requires highly-skilled and exhausting labor because the combine operator must fulfill multiple tasks simultaneous...

This paper describes the development, simulation, and experimental validation of a novel grain unloading-on-the-go automation system (automatic offloading) for agricultural combine harvesters. Unloading-on-the-go is desirable during harvest, but it requires highly-skilled and exhausting labor because the combine operator must fulfill multiple tasks...

Since the introduction of diesel urea SCR technology, aftertreatment thermal management has become critical for maintaining SCR catalyst light-off and thereby low cumulative cycle NOx emissions. A novel diesel engine aftertreatment thermal management strategy is proposed which utilizes a 2-stroke breathing variable value actuation strategy to incre...

This paper outlines a novel sensor selection and observer design algorithm for linear time-invariant systems with both process and measurement noise based on H 2 optimization to optimize the tradeoff between the observer error and the number of required sensors. The optimization problem is relaxed to a sequence of convex optimization problems that...

Rapid warm-up of a diesel engine aftertreatment system (ATS) is a challenge at low loads. Modulating exhaust manifold pressure (EMP) to increase engine pumping work, fuel consumption, and as a result, engine-outlet temperature, is a commonly used technique for ATS thermal management at low loads. This paper introduces exhaust valve profile modulati...

Diesel engine cylinder deactivation (CDA) has been demonstrated to provide significant efficiency and aftertreatment thermal management benefits, enabling fuel-efficient emissions reduction from modern diesel engines at low load engine operation. Dynamic cylinder activation (DCA), a variant of CDA where the set of deactivated cylinders varies on a...

Low air-flow diesel engine strategies are advantageous during low load operation to maintain temperatures of a warmed-up aftertreatment system (ATS) while reducing fuel consumption and engine-out emissions. This paper presents results at curb idle for internal EGR (iEGR) that demonstrate low airflow and reduced engine-out emissions during fuel-effi...

From the design space explored for series architecture plug-in hybrid electric vehicle transit buses by the authors, one powertrain and control design is selected to provide maximum benefit to investment ratio. Sensitivity analysis is performed for this powertrain configuration. Vehicle parameters (including vehicle mass, coefficient of drag, coeff...

This article performs a novel comparison of the life-cycle costs of the series and parallel architectures for plug-in hybrid electric vehicles. Economic viability is defined as having a payback period less than 2 years and number of battery replacements less than or equal to three over a vehicle life of 12 years along-with drivability and gradabili...

Cylinder deactivation is an efficient strategy for diesel engine exhaust aftertreatment thermal management. Temperatures in excess of 200 °C are necessary for peak NO x conversion efficiency of the aftertreatment system. However, during non-fired engine operation, known as motoring, conventional diesel engines pump low-temperature air through the a...

At low-to-moderate loads, modern diesel engines manipulate exhaust manifold pressure to drive exhaust gas recirculation and thermally manage the aftertreatment. In these engines, exhaust manifold pressure control is typically achieved via either a valve after the turbine, a variable geometry turbine, or wastegating. The study described here demonst...

Aftertreatment thermal management is critical for regulating emissions in modern diesel engines. Elevated engine-out temperatures and mass flows are effective at increasing the temperature of an aftertreatment system to enable efficient emission reduction. In this effort, experiments and analysis demonstrated that increasing the idle speed, while m...

Cylinder deactivation (CDA) and cylinder cutout are different operating strategies for diesel engines. CDA includes the deactivation of both the valve motions and the fuel injection of select cylinders, while cylinder cutout incorporates only fuel injection deactivation in select cylinders. This study compares diesel engine aftertreatment thermal m...

Modern diesel engine aftertreatment systems require elevated temperatures for effective reduction of engine-out emissions. Maintaining elevated aftertreatment temperatures in a fuel-efficient manner is a challenge, especially at low-load engine operation where engine-outlet temperatures are low; therefore, higher engine-outlet temperatures are typi...

Fuel-efficient aftertreatment thermal management in modern diesel engines is a difficult challenge, especially during low-load operation. This study explores the performance of cylinder deactivation in a diesel engine during low-load operation following highway cruise through experimental evaluation of two drive cycles, specifically extended idle a...

Prior design optimization efforts do not capture the impact of battery degradation and replacement on the total cost of ownership, even though the battery is the most expensive and least robust powertrain component. A novel, comprehensive framework is presented for model-based parametric optimization of hybrid electric vehicle powertrains, while ac...

Approximately 40% of typical heavy-duty vehicle operation occurs at loaded idle during which time conventional diesel engines are unable to maintain aftertreatment component temperatures in a fuel-efficient manner. Fuel economy and thermal management at this condition can be improved via reverse breathing, a novel method in which exhaust gases are...

The U.S. freight transportation system is a complex agglomeration of interacting systems that includes line-haul and urban delivery vehicles, inter and intra-city highways, and support infrastructure. In order to project the evolution of the system and the market penetration of emerging freight vehicle technologies, it is important to model the afo...

Cylinder deactivation has been recently demonstrated to have fuel savings and aftertreatment thermal management benefits at low to moderate loads compared to conventional operation in diesel engines. This study discusses dynamic cylinder activation as an effective variant to fixed diesel engine cylinder deactivation. The set of inactive and active...

Cylinder deactivation is an effective strategy to improve diesel engine fuel efficiency and aftertreatment thermal management when implemented through deactivation of both fueling and valve motion for a set of cylinders. Brake power is maintained by injecting additional fuel into the remaining activated cylinders. The initial deactivation of cylind...

Within electrified vehicle powertrains, lithium-ion battery performance degrades with aging and usage, resulting in a loss in both energy and power capacity. As a result, models used for system design and control algorithm development would ideally capture the impact of those efforts on battery capacity degradation, be computationally efficient, an...

Valvetrain flexibility enables the optimization of the engine’s ability to breathe across the operating range, resulting in more efficient operation. The authors have shown the merit of improving volumetric efficiency via valvetrain flexibility to improve fuel efficiency at elevated engine speeds in the previous work. This study focuses on producti...

Electric machine performance (peak torque vs. speed) and efficiency characteristics are frequently estimated using magnetic finite element analysis (FEA). In this paper, it is shown that the governing mathematical relationships that are solved in such an analysis allow for the implementation of straightforward scaling laws. Instead of re-running th...

Valve train flexibility enables optimization of the cylinder-manifold gas exchange process across an engine’s torque/speed operating space. This study focuses on the diesel engine fuel economy improvements possible through delayed intake valve closure timing as a means to improve volumetric efficiency at elevated engine speeds via dynamic charging....

A large fraction of diesel engine tailpipe NOx emissions are emitted before the aftertreatment components reach effective operating temperatures. As a result, it is essential to develop technologies to accelerate initial aftertreatment system warm-up. This study investigates the use of early exhaust valve opening (EEVO) and its combination with neg...

The light-duty vehicle market has seen some adoption of hybrid electric vehicles that is not reflected in the heavy-duty market. The major challenges associated with the heavy-duty segment are: (i) greater emphasis on economic viability, (ii) reluctance to take on risk associated with new technologies, and (iii) numerous diverse applications that p...

Modern on-road diesel engine systems incorporate flexible fuel injection, variable geometry turbocharging, high pressure exhaust gas recirculation, oxidation catalysts, particulate filters, and selective catalytic reduction systems in order to comply with strict tailpipe-out NOx and soot limits. Fuel consuming strategies, including late injections...

Within electrified vehicle powertrains, lithium-ion battery performance degrades with aging and usage, resulting in a loss in both energy and power capacity. As a result, models used for system design and control algorithm development would ideally capture the impact of those efforts on battery capacity degradation, be computationally efficient, an...

Physically-based Li-ion electrochemical cell models have been shown capable of predicting cell performance and degradation, but are computationally expensive for optimization-oriented design applications. Faster empirical models have been developed from experimental data, but are not generalizable to operating conditions outside of the range establ...

Approximately 30% of the fuel consumed during typical heavy-duty vehicle operation occurs at elevated speeds with low-to-moderate loads below 6.5 bar brake mean effective pressure. The fuel economy and aftertreatment thermal management of the engine at these conditions can be improved using conventional means as well as cylinder deactivation and in...

Physically-based Li-ion electrochemical cell models have been shown capable of predicting cell performance and degradation, but are computationally expensive for optimization-oriented design applications. Faster empirical models have been developed from experimental data, but are not generalizable to operating conditions outside of the range establ...

Electric vehicles (EVs) are a promising alternative to conventional vehicles. Several commercial EVs have already been in the market for a few years. However, greater adoption of EVs still faces several challenges. The concern about lifespan of EV batteries due to degradation is one of them. Lifespan information of populations of EV batteries is st...

Premixed charge compression ignition (PCCI) is a promising combustion strategy for reducing in-cylinder NOx and particulate matter formation in diesel engines without incurring fuel penalty. However, one of the challenges in PCCI implementation is that the process does not allow direct control of the combustion timing. The crank angle of 50% heat r...

The optimal design of hybrid electric vehicle powertrains from a systems perspective is critical to realize the maximum benefits of hybridization for a given application, especially in the heavy-duty vehicle space due to the large number of unique applications. This paper proposes a novel framework that enables parametric design optimization of hyb...

Abstract—Heavy-duty over-the-road trucks require periodic active diesel particulate filter regeneration to clean the filter of stored particulate matter. These events require sustained temperatures between 500 and 600□C to complete the regeneration process. Engine operation during typical 65 mile/hour highway cruise conditions (1200 rpm/7.6 bar) re...

Fuel efficient thermal management of diesel engine aftertreatment is a significant challenge, particularly during cold start, extended idle, urban driving, and vehicle operation in cold ambient conditions. Aftertreatment systems incorporating NOx-mitigating selective catalytic reduction and diesel oxidation catalysts must reach ∼250 °C to be effect...

Most diesel engines meet today’s strict NOx and particulate matter emission regulations using after-treatment systems. A major drawback of these after-treatment systems is that they are efficient in reducing emissions only when their catalyst temperature is within a certain range (typically between 250 °C and 450 °C). At lower engine loads this is...

A diode-laser-absorption-spectroscopy-based sensor system was used to perform high-speed (100 Hz to 5 kHz) measurements of gas properties (temperature, pressure, and vapor concentration) at the turbocharger inlet and at the exhaust gas recirculation (EGR) cooler exit of a diesel engine. An earlier version of this system was previously used for high...

Modeling and control of the gas exchange process in modern diesel engines is critical for the promotion and control of advanced combustion strategies. However, most modeling efforts to date use complex stand-alone simulation packages that are not easily integrated into, or amenable for the synthesis of, engine control systems. Simpler control-orien...

In response to strict emissions regulations, engine manufacturers have implemented aftertreatment technologies to reduce the tailpipe emissions from diesel engines. The effectiveness of most of these systems is limited when exhaust temperatures are below 250°C. This is problematic during cold start and at low-load engine operation when the exhaust...

Fuel injection rate shaping is a strategy to improve fuel efficiency and reduce harmful emissions in diesel engines. Due to their fast response, piezoelectric fuel injectors are capable of rate shaping operation. This paper describes a model-based closed-loop controller of injection flow rate for a piezoelectric fuel injector. This within-an-engine...

A diode laser-based sensor system, utilizing absorption spectroscopy, has been developed to provide high-speed (5 kHz) simultaneous measurements of temperature and water vapor concentration in the intake manifold of a diesel engine. A fiber-coupled 1.38 mm diode laser was used to probe absorption transitions of water vapor for the high-speed gas te...

In-cylinder oxygen fraction serves as a critical control input to advanced combustion strategies, but is extremely difficult to measure on production engines. Fortunately, the in-cylinder oxygen levels can be estimated based on accurate estimates or measurements of the oxygen fraction in the intake and exhaust manifolds, the in-cylinder charge mass...

One of the major challenges in the control of advanced combustion modes, such as premixed charge compression ignition, is controlling the timing of the combustion event. A nonlinear model-based controller is outlined and experimentally shown to be capable of controlling the engine combustion timing during diesel premixed charge compression ignition...

Fuel injection rate shaping is one path towards cleaner and more efficient diesel engines. Piezoelectrically actuated fuel injectors meet this requirement, but can exhibit improved model-based estimation performance when their internal parameters are estimated on line. To this end, this paper presents an online parameter estimation strategy for a p...

Piezoelectric fuel injectors provide a means to reduce fuel consumption, noise and emissions in modern IC engines. This paper summarizes an effort resulting in within-a-cycle estimation of injected fuel flow rate for “rate shaped” injection profiles. A reduced order model is derived by simplifying a physically based, experimentally validated simula...

Recently, there has been a push within engineering curricula to adopt more learner-centered pedagogies, such as case-based instruction. Case-based instruction has been hypothesized to make the curriculum more relevant and motivating for students by pushing them to integrate the concepts they have learned with other experiences. The current study ex...

The use of biodiesel blends has the potential to result in many benefits including decreased reliance on imported petroleum, increased sustainability, decreased net carbon dioxide emissions, and decreased particulate matter emissions. There are, however, two major combustion-related challenges to the use of biodiesel blends: (1) decreased torque/po...

Energy needs in the transportation sector and strict emissions regulations have caused a growing focus on increasing engine efficiency while simultaneously minimizing engine out emissions. One method for accomplishing this is to leverage advanced combustion strategies which are efficient yet very clean. One such combustion mode is premixed charge c...

Fuel injection rate shaping is one way to improve fuel efficiency and reduce harmful emissions in IC engines. Piezoelectrically actuated fuel injectors have a particularly fast response, which makes them capable of rate shaping operation. In this paper, a model-based closed-loop controller is designed to control the fuel injection rate passing thro...

Stringent emissions and fuel economy regulations motivate the investigation of advanced combustion strategies such as premixed charge compression ignition. However, controlling premixed charge compression ignition is challenging as there is no direct trigger for the combustion event. In addition, fuel-flexible applications must account for the impa...

This paper describes a simple, analytical, control-oriented model for prediction of combustion timing during premixed charge compression ignition combustion with early fuel injection. The model includes direct dependence on in-cylinder temperature, in-cylinder pressure, and the total in-cylinder O2 mass fraction, including the contribution of recir...

Advanced combustion modes, such as PCCI, operate near the system stability limits. In PCCI, the combustion event begins without a direct combustion trigger in contrast to traditional spark-ignited gasoline engines and direct-injected diesel engines. The lack of a direct combustion trigger necessitates the usage of model-based controls to provide ro...

Piezoelectric fuel injectors provide a means to lower emissions, noise and fuel consumption in advanced IC engines by enabling complex injection rate profiles - referred to a “rate shaping”. However, consideration of the flow rate non-linearity, piezostack hysteresis, and hydro-mechanical dynamics is required to achieve precise control of rate shap...

Piezoelectric fuel injectors provide a means to lower emissions, noise, and fuel consumption in advanced internal combustion engines by enabling complex injection rate profiles-referred to as "rate shaping.'' Consideration of flow rate nonlinearities, piezostack hysteresis, and hydromechanical dynamics is required to achieve precise control of rate...

The focus of this paper is the analysis of a high-gain observer for estimating un-steady inputs, including guarantees for: (1) robustness to measurement uncertainty, and (2) transient upper bound on estimator error. A method for selecting the observer gain based on measurement uncertainty, acceptable steady-state errors, and desired estimation erro...

Biodiesel is a diesel fuel alternative which is produced from renewable and domestically available sources. The use of biodiesel generally lowers carbon dioxide, carbon monoxide and particulate matter emissions. However, there are certain challenges associated with the use of biodiesel, mainly (1) lower fuel energy density, (2) increased nitrogen o...

Piezoelectric fuel injectors will require closed-loop control to realize tightly spaced injections. This paper describes an estimation algorithm for cycle-to-cycle determination of an injection flow profile for use as feedback for closed-loop control. A control design-amenable, 2-pulse approximate model is outlined to represent the dynamics of simu...

Strict emissions constraints and interest in increasing engine efficiency are causing growing attention on advanced combustion strategies such as premixed charge compression ignition (PCCI) which can drastically lower particulate matter, and nitrogen oxide emissions. Control of PCCI requires an understanding of the underlying dynamics that govern t...

In an effort to reduce dependence on petroleum-based fuels and increase engine efficiency, fuel-flexible engines with advanced technologies, including variable valve timing, are being developed. Fuel-flexible spark-ignition engines permit the increased use of ethanol–gasoline blends. Ethanol, an alternative to petroleum-based gasoline, is a renewab...

The Purdue University EcoMakers team has completed its first year of the EcoCAR 2 Competition, in which the team has designed a Parallel-Through-the-Road Plug-in Hybrid Electric Vehicle that meets the performance requirements of a mid-size sedan for the US market, maintaining capability, utility and consumer satisfaction while minimizing emissions,...

Modulation of the effective compression ratio, a measure of the amount of compression of in-cylinder gases above intake manifold conditions, is a key enabler of advanced combustion strategies aimed at reducing emissions while maintaining efficiency, and is directly influenced by modulation of intake valve closing time. To date, the effective compre...

The ability to modulate the effective compression ratio (ECR) of an engine is a key enabler of advanced combustion strategies. ECR is a measure of the effective in-cylinder compression of gases above intake manifold conditions. An engine's ECR is usually computed from in-cylinder pressure data, requiring reliable in-cylinder pressure sensors that a...

Advanced diesel engine architectures employing flexible valve trains enable emissions reductions and fuel economy improvements through advanced combustion strategies. These combustion strategies, such as pre-mixed charge compression ignition (PCCI), homogenous charge compression ignition (HCCI) and low temperature combustion (LTC), are controlled a...

This paper describes a simple, analytical, control-oriented and physically-based model for prediction of combustion timing during PCCI combustion. The model includes direct dependence on in-cylinder temperature, in-cylinder pressure, and the total in-cylinder O2 mass fraction. It is extensively validated with experimental PCCI data from a multi-cyl...

Concern over the availability of fossil fuels and energy usage have produced an interest in both alternative fuels and new engine technologies such as variable valve timing to improve engine efficiency. Fuel-flexible engines permit the increased use of ethanol-gasoline blends. Ethanol is a renewable fuel which has the added advantage of improving p...

Advanced diesel engine architectures employing flexible valve trains enable emissions reductions and fuel economy improvements. Flexibility in the valve train allows engine designers to optimize the gas exchange process in a manner similar to how common rail fuel injection systems enable optimization of the fuel injection process. Modulating valve...

Advanced combustion strategies including premixed charge compression ignition, homogeneous charge compression ignition, and lifted flame combustion are promising approaches for meeting increasingly stringent emissions regulations and improving fuel efficiency in next generation powertrains. Variable valve actuation and closed-loop control promise t...

This paper introduces, and presents experimental validation for, an on-engine applicable control framework for fuel-flexible combustion of diesel–biodiesel blends. The approach is based on changing two of the closed-loop targeted control variables used by the engine control module (ECM): (1) replacing exhaust gas recirculation (EGR) fraction with c...

Improving tradeoffs between noise, fuel consumption, and emissions in future internal combustion engines will require the development of increasingly flexible fuel injection systems, which can deliver more complex injection profiles. Piezoelectric injectors have the ability to deliver multiple, tightly spaced injections in each cycle, but are highl...

As engine designers look for ways to improve efficiency and reduce emissions, piezoelectric actuated fuel injectors for common rail diesel engines have shown to have improved response characteristics over solenoid actuated injectors and may allow for enhanced control of combustion through multipulse, closely spaced injections or rate shaping. This...

As global petroleum demand continues to increase, alternative fuel vehicles are becoming the focus of increasing attention. Biodiesel has emerged as an attractive alternative fuel option due to its domestic availability from renewable sources, its relative physical and chemical similarities to conventional diesel fuel, and its miscibility with conv...

Modeling and control of the gas exchange process in modern diesel engines is critical for the promotion and control of advanced combustion strategies. However, most modeling efforts to date use complex stand-alone simulation packages that are not easily integrated into, or amenable for the synthesis of, engine control systems. Simpler control-orien...

While common-rail diesel fuel injection systems utilizing solenoid-actuated injectors have drastically improved the ability to lower emissions, noise, and fuel consumption, their limited bandwidth does not allow for tightly spaced injections or rate shaping. Piezoelectric injectors have that capability, but introduce multiple control challenges tha...

Piezo electric injectors provide a means to lower emissions, noise and fuel consumption in advanced IC engines, by providing the capability to allow for tightly spaced injections and rate shaping. With a focus on generating a control design amenable model capturing the injector needle dynamics, the effort described here includes a model simplificat...

The gas exchange process in a modern diesel engine is generally modeled using manufacturer-provided performance maps that describe mass flows through, and efficiencies of, the turbine and compressor. These maps are typically implemented as look-up tables requiring multiple interpolations based on pressure ratios across the turbine and compressor, a...

Accurate calculation of the conditions (i.e., temperature, pressure, and enthalpy) of internal combustion engine cylinder exhaust is critical to the modeling of, and control design development for, gas exchange in modern and future diesel engine systems. In this paper, a physically-based model for cylinder exhaust temperature, pressure, and enthalp...

Premixed charge compression ignition (PCCI), an advanced mode combustion strategy, promises to simultaneously deliver the fuel efficiency of diesel combustion and the ultralow NO(x) emissions that usually require advanced exhaust aftertreatment. A flexible, computationally efficient, and whole engine simulation model for a 2007 6.7 l diesel engine...

Biodiesel, an alternative fuel for diesel engines, has the potential to reduce dependence on foreign sources of petroleum, reduce harmful particulate matter (soot), carbon monoxide, and unburned hydrocarbon emissions, and net carbon dioxide emissions. Despite these benefits, biodiesel utilization has the combustion-related challenges of increased f...

“Fuel-flexible combustion control” strategies require accurate fuel composition information. A physics-based fuel blend fraction estimator for lean-burn combustion is used to assess the impact of uncertain variables on the estimator accuracy. For biodiesel blends in a diesel engine, the strategy is shown to be minimally affected by biodiesel feedst...

This paper describes an accurate, flexible, and computationally efficient whole engine model incorporating a multizone, quasidimension combustion submodel for a 6.7-l sixcylinder turbocharged diesel engine with cooled exhaust gas recirculation (EGR), cooled air, and multiple fuel injections. The engine performance and NOx emissions predicative capa...

B ackground Case studies have been found to increase students' critical thinking and problem‐solving skills, higher‐order thinking skills, conceptual change, and their motivation to learn. Despite the popularity of the case study approach within engineering, the empirical research on the effectiveness of case studies is limited and the research tha...

As the world is faced with continued petroleum demand, the need for alternative fuels which are renewable and domestically available is becoming apparent. Biodiesel is one such attractive alternative fuel which has physical and chemical properties similar to, and miscible with conventional diesel. While biodiesel does have many advantages, due to f...