Our group is always working on many different projects at the time, the following list contains some of our current research interests. For a complete list you are welcome to contact our team and request our annual report.

Active Composite Wheel

Active-composite wheel vehicles extend the concept of the wheel to climb and jump over large obstacles, and provide active suspension capabilities. Current vehicle systems are very fast and comparatively efficient on flat, paved surfaces. However, both speed and efficiency decrease greatly in off-road or variable terrain applications. To offset these disadvantages, larger wheels would have to be installed. Unfortunately, the larger wheels will be under-utilized in paved road applications, and their extra weight will considerably reduce the average fuel efficiency.
The active composite wheel accommodates a wide variety of terrains, and is able to negotiate both positive and negative obstacles in its path. Essentially, the effective wheel sizes are variable, allowing higher speed while traveling on wheels of smaller radius, and increased maneuverability while traveling on wheels of larger radius. Such a vehicle would be much lighter than a vehicle
with equivalent capabilities using larger wheels. The issues to be investigated include the control system of the vehicle. The increased flexibility of the vehicle requires controls of a high degree of complexity. Even defining the user inputs so as to minimize them yet retain maximum capabilities requires significant research. In addition to forward drive control, steering systems are also researched, as the simple axles of conventional vehicles do not exist on composite-wheel vehicles.

Active Suspension

Most road vehicles still rely on passive suspensions composed of a spring and damper combination. While passive suspensions are simple and cost effective, they do not provide optimal ride comfort and road handling under all circumstance. Their characteristics are fixed by design and favor either performance or comfort. Semi-active suspensions in which damping and springing parameters are electronically adjusted have been introduced during the last decade to remedy to these shortcomings but they still do not provide ideal ride characteristics. Active suspensions provide great comfort and perfect road handling without any compromise. Active suspensions are either hydraulically or electrically actuated. Existing systems typically require large power supplies and consume very significant amounts of energy, which increases the fuel consumption of the vehicle.

Our approach is based on oscillating electric machines, which allows tuning in real time the parameters of the suspension over a seemingly infinite range of frequencies and adjusting the ride height electronically. The use of oscillating electric machines reduces very significantly the energy consumption of the suspension, which is now limited to compensating the losses of the system.

Active Vibration Control by Electric Machines

In industrial systems such as robotic manipulators, automotive transmissions, engines, and high-performance electric motor drives, the load torque often rapidly fluctuates and induces vibrations. Such vibrations degrade dynamic control performance, fatigue the motor shaft as well as other system components, and result in audible noise. It is therefore desirable or necessary to suppress the vibration to achieve the required dynamic performance. The objective of this research is to improve the system robustness against load torque fluctuation and system parameter drift.

The conventional approach consists in introducing a disturbance rejection controller that uses a load torque observer. The load torque observer is essentially a differentiator for low-frequency signals. The drawback of this method is the need for accurate motor acceleration information, which is difficult to obtain in practical applications. A novel approach is being developed that uses a feed-forward compensation voltage or current command to reduce the vibration. This approach has the advantage of reducing vibrations during bother steady state and transient operation. The key to this approach is the generation of the compensation signals. They are derived through the analysis of system parameters and operational variables.

Advanced 4-Quadrant Brushless DC Motor-Generator Drives

Proper brushless DC machines operation requires firing the inverter’s switches at the appropriate time. In order to determine this appropriate time, knowledge of the rotor position is required. This may be achieved with a shaft position sensor but their reliability is questionable. In many applications, should the sensor fail the drive should still be operable. Sensorless control techniques allow replacing the sensor in case it fails. Conventional sensorless control techniques have two major weaknesses: they do not work well at low speed and during transients. We have developed a control technique that remedies to these problems and allows accurate and robust operation from near zero speed to high speed. It uses a physically insightful, speed-independent function based on a new flux linkage function.

Some applications of brushless DC generators require maximizing the power throughput (mechanical to electrical) for a given size, weight and amount of copper losses. This is particularly true for aerospace, ground vehicle or portable applications. A novel control technique has been developed that maximizes the power throughput of a brushless DC generator by controlling the profile of the current waveforms by the means of an inverter. Improvements over 20% in power throughput have been obtained compared to a brushless DC generator coupled to a diode rectifier. This technique is currently being investigated for motoring operation.

Applications of the Inductor Converter Bridge

The Inductor Converter Bridge (ICB) has been thoroughly studied by our group in the past, specially for Superconductive Magnetic Energy Storage (SMES). Currently we are studying the application of this circuit and some of it’s topological variations to motor drives systems, power systems, renewable energy systems among others.

Articulate Power Systems

Today’s power systems are designed in such a manner that changes in the load affect the system performance. Our group has developed the concept of articulate power systems, where the system characteristics “change” dynamically in order to always give the best possible performance of the system. Currently we are working on the design of such a system, with the help of power electronics.

Cellular Power Systems & the Power Selectivity Problem

New architectural and technological alternatives are being studied in order to develop a interconnected multi-terminal power system that can selectively transfer power between it’s nodes. Currently the Cellular Power System topology is being considered and the power electronic converters necessary for its operation are being selected.

Computer Modeling and Dynamics of Vehicular Power Systems

This research decomposes into two projects: modeling and simulation of advanced electrical power systems for military applications and simulation of multi converter power electronic systems for practical constant power loads. The purpose of the first project is to develop a configurable power system capable of handling electrical power requirements of modern multifunction military vehicles. The initial phase involves the development of models for the different subsystems of the aircraft: engines, alternator, integrated starter generator, fuel cell, rectifier, CAN, load and energy storage devices. The strategy is to individually develop and test the different subsystems in Matlab/Simulink, then to proceed to the integration of the overall system. The second project involves the analysis of interactions, dynamics and stability problems caused by the interconnection of power electronics converters in modern power systems.

Crop-to-Wheel Initiative

Widely available and inexpensive fossil fuels have been the key to the development of the modern civilization by providing cost-effective and convenient transportation, electricity, heating, etc… However, they suffer two major flaws that result from their fossil nature. The amount of fossilized carbon is finite and will eventually be exhausted. The combustion of fossil fuels is an open-cycle process that accumulates carbon dioxide in the atmosphere, which results in global warming due to increased greenhouse effect.

The crop-to-wheel initiative is an integrated approach to the automobile that focuses both on fuel production and vehicle power train technologies. The result is a new automobile industry with the following properties: sustainable fuel supply, no net carbon dioxide emissions and higher efficiency. This approach presents many advantages over hydrogen economy schemes.

The crop-to-wheel initiative is based on biofuels, derived from biomass. Although the combustion of biofuels does release carbon dioxide, photosynthesis removes an equivalent amount from the atmosphere. Carbon dioxide thus follows a closed cycle driven by solar energy, which ensures sustainability. While biomass is an inexpensive feedstock, the conversion process was traditionally where the excessive cost was added. The novel MixAlco process is a cost-effective process that converts the biomass into ketones through lime pre-treatment, digestion by micro-organisms and thermal treatment. The ketones may be converted to alcohols by hydrogenation. The selling price for the alcohol fuel is estimated between $0.40 to $1 per gallon depending on feedstock costs and scale.

The StarRotor engine and StarRotor-based hybrid electric vehicles based are key technologies for the crop-to-wheel initiative. The resulting fuel efficient transportation is beneficial because it limits the requirements for land area. This latter is also reduced by the use of municipal and other biological wastes, which in turn provides a convenient and cost-effective solution to their disposal.

This initiative is based on 20 patents from our group, with many more to follow.

Development of a Standard Form Power Equation for Magnetic Circuits

The traditional Electromagnetic Theory is being thoroughly revised under the scope of new mathematical tools. The purpose of this is to increase the level of understanding of the electromagnetic phenomena up to the point that more accurate and faster calculations can be made on those quantities that are important, for example, in the design of electric machines.

Development of the Wireless Car

Advances in wireless communication offer the possibility of completely reworking automotive power systems, controls, and communications. The architecture of the power system for instance is no longer constrained by the necessity to run power-carrying cables from the battery to a distant load via the dashboard. A single power bus may run across the length of the vehicle, easily reaching all electrical loads, with a minimum expense of copper. Controls and data are then provided and collected by wireless means, which greatly simplifies the wiring in the vehicle and offers the possibility of adding components to the vehicle without concerns of routing wires. New vehicle power system topologies are rendered possible as well as new control methods, operational modes, dynamic responses and integration of novel components.

Eddy Current Brakes

Conventional automotive friction brakes suffer from reduced reliability and safety under varying conditions, such as wear, water, and high temperature. They are also an unsatisfactory tool for anti skid and vehicle dynamic stability enhancement, due to their long hydraulic or pneumatic system time delay. Eddy-current brakes integrated with existing friction disk brakes solve the above problems, in a safe and cost effective way. Eddy current braking is already being used in drilling rigs and some large buses.

Braking is obtained by the rotation of the disc in front of magnetic poles, which results in induced eddy-currents in the disc. The interaction of the currents with the magnetic flux of the poles creates the braking torque. The novelty is the use of rare earth permanent magnets instead of electromagnets to induce the magnetic flux in the disc. The flux is controlled by shunting the magnet using a specially designed magnetic circuit. Shunting is achieved by mechanical or electrical means. The magnetic circuit is designed to preserve the magnets from the heat dissipated in the disc. Eddy-current brakes provide many advantages such as reduced actuation power, immunity to wheel-lock, failure safety, fast response, and compatibility with regenerative braking in hybrid vehicles. While friction brakes are not replaced, they are rendered smaller, cheaper, and safer.

Further refinements of the concept of eddy current braking include a technique for obtaining a constant braking force from critical speed to maximum speed and a novel concept of self-powered wireless-control brake.

Hardware-in-the-Loop Development of Motor Drives

This research focuses on the use of commercially available off-line and real-time simulation packages for the hardware-in-the-loop development of motor drives. The objective is to provide a fully adjustable development tool that allows developing the controls for a motor drive before the drive or a specific load is available. This technique is particularly useful for the fast and low-cost development of short-development cycle drives, high-cost drives, critical mission motor drives, drives and loads not yet developed, such as in automotive traction, manufacturing, military, aerospace, and in research and education. The various aspects of this research include the modeling of DC, induction, brushless DC, and switched reluctance motor drives in Matlab-Simulink TM , and the conversion of these models to real-time simulation models using RT-LAB TM with a focus on the issues of real-time samplingrate and high-fidelity.

Hybrid Energy Storage

Chemical batteries, ultracapacitors and flywheels have different operating characteristics. Chemical battery and flywheel are more like energy sources, which deliver energies with medium power in relative long time period, whereas, ultracapacitor is more like a power source, which delivers large power in a short time period. It is feasible by combining two of these basic energy storages together to constitute a high energy and high power energy storage system-hybrid energy storage system.

The most straightforward approach is to directly connect ultracapacitors to batteries. This configuration has the simplest structure and no control unit needed. The behavior of the ultracapacitors is more like a current filter, so that, high battery peak current is leveled. The first responding for this step current is the ultracapacitors, and then the load current gradually transfers from the ultracapacitors to the batteries due to the voltage drop caused by the storage energy decrease in the ultracapacitors. When the load disappears, the ultracapacitors is charged by the batteries automatically.

In a passively connected pack of ultracapacitors and batteries, the power flows (output and between the components) cannot be managed. A passive combination makes poor use of the high-power density of ultracapacitors. This remedied to by the use of power electronics converters to interconnect the two. Basically, the power conditioning operation can be divided into three different modes, (1) Ultracapacitor peaking operation for high power demand (positive and negative, (2) ultracapacitor charging from batteries, and (3) batteries alone operation. These operation modes are implemented by a central control unit. The central control unit commands the power electronics and receives signals through sensors. The control objectives are: (1) to meet the power requirement, (2) to keep the battery current in a preset region, and (3) to keep the battery SOC in its middle region (0.4 to 0.6 for example), in which the battery efficiency are usually optimized. This system can potentially fully use the high power property of the ultracapacitors, and therefore resulting in a small battery pack. The actively controlled battery current can potentially lead to more efficient battery operation and easier thermal management, stable operation and high efficiency. Compared with battery/ultracapacitor hybrid system, flywheel/ultracapacitor system would bear the advantage of extended service life, wide temperature adaptability and less maintenance needed. These advantages are very important to military vehicles.

Induction Motors for Regenerative Dissipative Braking

This project is an evolution of the eddy-current brake project. An eddy-current brake and an induction motor are similar machines with very few differences. While an eddy-current brake has a plain rotor and a DC excitation flux, an induction motor has a squirrel cage rotor and AC excitation.

A properly designed induction motor can therefore be operated as a motor-generator, as an eddy-current brake or both at the same time. The application of this machine is in hybrid vehicles, where it would be used for traction, regenerative or dissipative braking. The vehicle’s kinetic energy can simultaneously be regenerated or dissipated in proportions that can be varied to optimize the operation of the hybrid drive train. For instance, if the batteries are not fully charged regenerative braking may be used at rated power and while dissipative braking provides additional braking torque to meet the driver’s demand. When the batteries are fully charged, dissipative braking alone is used.

Omni-Directional Design Tool

The parametric design of a vehicle drive train involves determining the power/energy ratings, sizes, weights, etc…. of all major functional components in the drive train. These components are sized in order to meet performance requirements such as acceleration performance, grade ability, gas mileage, while simultaneously satisfying constraints like pollution norms, weight and volume restrictions. The conventional design procedure starts with performance requirements and works its way towards the sizing of the components, using the laws of physics relating them.

Omni-directional design is a new approach towards parametric design wherein the designer may start from any and as many of the design parameters of his choice and calculate the possible values for the remaining variables. When this design approach is applied to a complex system like hybrid electric vehicles, scenarios arise such that there are many possible values (ranges of values) for a particular output given the set input parameters as singular values. This interesting phenomenon can be harnessed for better design using multiple iterations with either the designer choosing the inputs following each iteration or having an optimization algorithm in the design algorithm.

Oscillating Electric Machines

Oscillations have been shown to occur naturally in electric machines because of the interaction between the rotor inertia and the armature inductance. While these oscillations are usually unwanted, this research is aimed at obtaining machines that oscillate naturally within a useful range of stroke and frequency. The objective is to develop an oscillating machine that can be fully controlled by its inverter and field winding. The parameters controlled include oscillating frequency, stroke, and nonlinear oscillation profiles. Their applications are in internal combustion engine valve actuation, piston pumps, printing heads, etc…

Real-Time Simulation

Laboratory experiments are an indispensable part of undergraduate teaching especially in motor drives, where students run motors in the lab and verify their behavior under different conditions as predicted by the theory taught in class. Hardware experiments are important for the students because they provide them with a “feel” of the machine. However, hardware-based experiments suffer inherent disadvantages: cost concerns limit the number and variety of experiments, safety concerns limit the nature and extent of experiments, and there is a limited access to motor parameters. Overall, hardware-based laboratories suffer a lack of flexibility. While offering maximum flexibility, conventional simulation packages do not offer any practical “feel” or sense of time.

The “Actual-Virtual Lab” has been developed to remedy to these shortcomings. It uses real-time simulation techniques and implements the concept of “virtual machine”. Students initially perform the experiment on the hardware, and then do the same on a virtual replica of the hardware. The parameters of the virtual machine are adjustable at any time through a graphic interface. The real-time simulation provides the students with a feel for electromechanical time constants and with the possibility to change design parameters such as inertia, friction coefficients, etc… Experiments that would be dangerous or impossible to conduct with hardware are now possible, thus greatly expanding the scope and reach of the laboratory. The possibility to remotely access the virtual laboratory through the internet further enhances the convenience and the quality of the teaching.

Series-Parallel Hybrid Drive Trains

While series and parallel hybrid drive trains are easy to understand and conceptualize, series-parallel hybrid drive trains provide the most opportunities for the optimization of the operation of each component, the minimization of overall drive train losses and the maximization of kinetic energy recovery during regenerative braking.

Series-parallel hybrid drive trains are a hybrid drive train architecture class that combines structural features of series and parallel drive trains. They are sometimes referred to as “power-split” architectures because the power flow is split between a mechanical path and an electrical path by the means of gears and planetary gears. The drive train performs the functions of an electric port for energy input and output and of an electromechanical continuously variable transmission. This later allows operating the engine on a locus of minimum specific fuel consumption.

This research project aims at inventorying all possible configurations for series-parallel hybrid drive trains, conceptualizing them, analyzing their fundamental characteristics and modeling them. Then we will devise design rules and control strategies for these architectures and apply them to a broad variety of vehicles, duties, and drive cycles.

Simulation and Design Studies of Hybrid Electric Vehicles

Very high speed flywheel systems are promising energy storage means for hybrid vehicles. They posses many advantages over chemical batteries, including high specific energy, high specific power, long cycle life, high energy efficiency, low maintenance requirements, reduced environmental contamination, reduced sensitivity to temperature and cost effectiveness.

Flywheels store kinetic energy in its high-speed rotor. However, current technology makes it difficult to propel the vehicle directly from the flywheel. The most commonly use approach is to couple the flywheel to an electric machine, a combination often referred to as a mechanical battery. While the amount of energy stored depends solely on the characteristics of the rotor (moment of inertia and speed), the peak power depends only on the electric machine. It is thus critical to design the electric machine so that it matches the characteristics of the flywheel and is capable of delivering rated power all across the operational speed range of the flywheel. This requirement primarily determines the maximum speed to base speed ratio and efficiency contour. It results that the choice of electric machines for flywheel drives is heavily influenced by these characteristics, and that the switched reluctance machine is strongly favored because of its ability to operate at constant power over a broad speed range and at very high speed.

Stability of the Inverse Dual Converter

The Inverse Dual Converter has shown to be useful under steady state conditions, but in order to find use for this circuit on more common applications, it’s stability must be studied. This is done with the use of computational models and mathematical circuit analysis tools, like the gyrator theory.

Star Rotor Engine

Internal combustion engines are inefficient in converting fuel into mechanical energy. While the theoretical maximum efficiency is about 40%, practical engines reach at most 20 to 25%. Furthermore, this peak efficiency is achieved only for one point and rapidly decreases for changing speed and torque output.

The StarRotor engine is a novel embodiment of the Brayton thermodynamic cycle, otherwise used in gas turbines and jet engines. Axial or centrifugal compressors and expanders are replaced by a novel positive displacement device called a “gerotor”, which compresses large volumes of air efficiently at low speed. The other features of the StarRotor engine include quasi-isothermal compression by spraying a fluid in the compressor, the use of a heat exchanger to recuperate the thermal energy of exhaust gases and a variable compression ratio obtained by non-restrictive means. The result is an engine that is very efficient (45-65%) over a broad range of speed and torque output, clean, quiet, vibration-free, low-maintenance, and capable of burning a wide variety of fuels.

The particular design of the gerotor compressor permits the integration of an electric generator within its outer rotor structure. This approach reduces the size and complexity of connecting the engine to a generator, while it allows an intimate integration of the StarRotor engine with hybrid electric drive trains. Hybrid vehicles based on the StarRotor engine and the integrated StarRotor engine-generator are being investigated.

Star Rotor Engine Based Hybrid Vehicles

In this project, we are investigating the integration of the StarRotor engine in hybrid vehicles. The objectives are to achieve minimum fuel consumption with minimum component weight, size and cost.

Rather than optimizing each component separately, the integration study seeks the optimization of the whole system. Two approaches are combined to achieve this goal: system level design and control strategy. In system level design, the parameters investigated include the power rating, operational speed range of the StarRotor engine, drive train gear ratios, energy storage system energy and power ratings, and electric motor rating and extended speed range width. Our previous research work has shown that proper system level design can significantly decrease the size and weight of the components and reduce the overall system losses while allowing maximum recovery of energy during regenerative braking.

The control strategy seeks the harmonious optimization of the overall system. Its design is tightly intertwined with that of the system. The control strategy decides the power flows within the system while taking into account the efficiency maps of each component and system level operational rules.

Survivability and Vulnerability of Hybrid Electric Drive Trains

Hybrid drivetrains are more complex than conventional drivetrains powered by a single engine. This complexity increases the probability of failures at system and component levels, which theoretically lowers the reliability and survivability of the vehicles. However, the presence of two power sources within the drivetrain confers hybrid vehicles a relative immunity to single point failure, i.e. the complete loss of functionality due to the failure of a single component. In most cases, it only results in a degradation of vehicle performance.

The analysis of survivability and performance degradation is based on two levels: system and component (or subsystem). The system level analysis includes control failure, signal transfer failure, energy transfer failure. The component level failure analysis is focused on the insides of the component and the analysis of failure causes and their immediate effects to this components and extended effects to overall drivetrain and vehicle performance.

Survivability is especially crucial to military vehicles. A proper analysis of the drivetrain reveals possible failure points and critical components that influence survivability. The results of this analysis allow the designer to implement specific technical measures to prevent total failure and reduce the degradation of performance in case of partial failure. The prediction of the level of performance degradation may also be used to generate warn the future users of the vehicle, thus allowing them to reach safety or repair. The benefits of this research carryover to civilian vehicles, enhancing their reliability for greater user satisfaction and safety.

Switched Reluctance Motor-Generator Drives

Regenerative breaking is a critical issue in propulsion applications such as electric and hybrid electric vehicles. Switched reluctance machines have been previously shown to provide decisive advantages for traction and regenerative braking, as well as rugged construction, and fault tolerance.

The power output of the switched reluctance generator is controlled by the phase current, which is challenging because of the dominant back-emf that causes the stator currents to increase even after the phase is turned off. This results in incontrollable torque on the shaft and requires an oversized inverter. The inverter rating should be further increased to withstand a worst case scenario due to speed variations in the prime mover. A current control technique has been developed that relies on turning off the phase at a safe angle determined using an online estimation of back-emf variations. At high speed, where the switched reluctance machine is the most efficient, the only control variables are the turn-on and turn-off angles. More power can be obtained from a switched reluctance generator if the phase is turned off in two steps. A control technique is being developed to take advantage of this technique and maximize both efficiency and power output.

System Level Control for H2 Fueled Engines

Hydrogen is being evaluated as an alternative fuel for internal combustion engines. Hydrogen engines have two major obstacles when competing with gasoline/diesel engines: a poor volumetric efficiency and high NOx emissions under stochiometric conditions. Supercharging, direct injection, and turbo charging lean mixtures, and exhaust after-treatment at stochiometric conditions are the most commonly adopted methods to solve these problems.

The hybridization of the hydrogen engine power train offers a unique alternative to solve these problems. It can result in better fuel economy, lesser intake boost requirement, and low emissions without exhaust after-treatment. The objective of this research, in cooperation with Argonne National Lab is to evaluate the optimum degree of hybridization, along with proper system and engine control, to achieve minimal pollution and maximal performance.

The Center for transportation research at Argonne National Laboratory is building a Mobile Advanced Technology Tested (MATT), which has the capability of hybridizing a hydrogen engine by emulating different sizes and types of motor and battery combinations through a torque source and a voltage source respectively, using hardware in the loop principle. Different degrees of hybridization and system controls will be tested with MATT on a 4 wheel chassis dynamometer to determine an effective degree of hybridization and control strategy.

Wireless Power Management

In electric circuit design, board space is becoming increasingly valuable. On this respect, our group is working on the development of a wireless power management bus. Both the hardware and protocol issues are being taken into account for this project. Many advantages have been identified that justify considering this technology.