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Three stator cooling jacket concepts, including a new cooling jacket concept with parallel straight spiral channels, are evaluated for electric machine of mild hybrid electric car. Steady-state cooling jacket thermal flow analysis and transient-state full motor simulations with circumferential, axial, and spiral jacket concepts are carried out to predict their heat transfer performance and temperature distribution. A prototype motor has been made with the new jacket concept. Infrared thermography is performed to detect the transient temperature distribution of the motor stator windings and laminations for validation of the thermal flow analysis.

Through analytical equations followed by a systematic optimization study using high-fidelity finite-element (FE) models, the torque capability of three common synchronous machine technologies—namely, a permanent magnet (PM) synchronous machine (PMSM) with V-shaped rare-earth rotor magnets, a PMSM with deep V-shaped ferrite rotor magnets, and a synchronous reluctance machine (SynRM) with four layers of conforming flux barriers are compared for an application in a 48-V mild hybrid electric car. The optimization of the deep V-shaped ferrite PMSM automatically resulted in a spoke-type PM layout for maximum torque production. Yet, an optimized SynRM with conforming flux barriers was achieved that could produce a higher torque than ferrite PMSM. One machine technology is selected and six variants of it, with two rotor PM layouts each with three alternative pole-slot combinations, are subsequently subjected to a large-scale FE model-based drive-cycle design optimization. Various pole-slot combinations are methodically compared in terms of drive-cycle losses, active material cost, torque ripple, and PM demagnetization level. More than 20 000 designs were analyzed over ten energy-centric torque-speed points to identify an optimal design solution. The results of multiphysics analysis incorporating electromagnetics, computational fluid dynamics, and structural analyses are provided, including a study on three different water jacket concepts. A final design is prototyped and primary experimental results are provided.

The design and optimization procedure of two different types of PM-assisted synchronous reluctance machine (PMASynRM) made of different types of PMs: Ferrite and NdFeB will be proposed in the paper. The two different types of PMASynRM are designed for the traction application and will be compared to a two-layer V-type IPM with NdFeB magnets only, which is used as the baseline design. The proposed two different types of designs have the same stator geometry and winding configuration as the baseline design. The main purpose in the paper is to reduce NdFeB PM content by investigating and comparing two different types of blended design PMASynRM, namely, a parallel hybrid design and a series hybrid design. The key challenges when reducing the rare-earth content are: (1) Maintaining the same rated torque as the baseline (2) Reducing even eliminating the risk of demagnetization due to the lower coercivity of ferrites at both low and high temperature. In the paper, we will focus on the comparative analysis of two different types of PMASynRM by means of the presented optimization process with emphasis on assessing the level of permanent demagnetization risk. In order to assess the structural integrity of the rotor, a mechanical analysis was conducted in parallel design. The proposed parrel design can generate competitive torque as the baseline design with around 25% reduction of rare-earth material while eliminating the demagnetization risk at the extreme low operating temperature of -20°C and high temperature of 150°C. The paper includes details of the optimization process and corresponding sample results, evaluation of demagnetization risk of both types of PMASynRM designs, and analysis and optimization results of both types of designs.

A large-scale finite element model-based design optimization algorithm is developed for improving the drive-cycle efficiency of permanent magnet (PM) synchronous machines with wide operating ranges such as those used in traction propulsion motors. The load operating cycle is efficiently modeled by using a systematic k -means clustering method to identify the operating points representing the high-energy-throughput zones in the torque–speed plane. The machine performance is evaluated over these cyclic representative points using a recently introduced computationally efficient finite element analysis, which is upgraded to include both constant torque and field-weakening operations in the evaluation of the machine performance metrics. In contrast with the common practice, which aims at enhancing the rated performance, the entire range of operation is considered in the present design optimization method. Practical operational constraints imposed by the voltage and current limits of the motor-drive system, excessive PM demagnetization, and torque ripple are accounted for during the optimization process. The convergence to the optimal design solutions is expedited by utilizing a new stochastic optimizer. The developed design algorithm is applicable to any configuration of sinewave-drive PM and synchronous reluctance motors over any conceivable load profile. Its effectiveness is demonstrated by optimizing the well-established benchmark design represented by the Toyota Prius Gen. 2 interior PM motor configuration over a compound operating cycle consisting of common U.S. driving schedules. Multiphysics electromagnetic, thermal, and mechanical performance of the optimized design solutions is discussed in a postdesign optimization stage.

Performance improvement of permanent magnet (PM) motors through optimization techniques has been widely investigated in the literature. Oftentimes the practice of design optimization leads to derivation/interpretation of optimal scaling rules of PM motors for a particular loading condition. This paper demonstrates how these derivations vary with respect to the machine ampere loading and ferrous core saturation level. A parallel sensitivity analysis using a second-order response surface methodology followed by a large-scale design optimization based on evolutionary algorithms are pursued in order to establish the variation of the relationships between the main design parameters and the performance characteristics with respect to the ampere loading and magnetic core saturation levels prevalent in the naturally cooled, fan-cooled, and liquid-cooled machines. For this purpose, a finite-element-based platform with a full account of complex geometry, magnetic core nonlinearities, and stator and rotor losses is used. Four main performance metrics including active material cost, power losses, torque ripple, and rotor PM demagnetization are investigated for two generic industrial PM motors with distributed and concentrated windings with subsequent conclusions drawn based on the results.

Large-scale design optimization of electric machines is oftentimes practiced to achieve a set of objectives, such as the minimization of cost and power loss, under a set of constraints, such as maximum permissible torque ripple. Accordingly, the design optimization of electric machines can be regarded as a constrained optimization problem (COP). Evolutionary algorithms (EAs) used in the design optimization of electric machines including differential evolution (DE), which has received considerable attention during recent years, are unconstrained optimization methods that need additional mechanisms to handle COPs. In this paper, a new optimization algorithm that features combined multi-objective optimization with differential evolution (CMODE) has been developed and implemented in the design optimization of electric machines. A thorough comparison is conducted between the two counterpart optimization algorithms, CMODE and DE, to demonstrate CMODE’s superiority in terms of convergence rate, diversity and high definition of the resulting Pareto fronts, and its more effective constraint handling. More importantly, CMODE requires a lesser number of simultaneous processing units which makes its implementation best suited for state-of-the-art desktop computers reducing the need for high-performance computing systems and associated software licenses.

Through a systematic optimization study using high-fidelity finite-element (FE) models, torque capability of three common synchronous machine technologies, namely a permanent magnet (PM) synchronous machine (PMSM) with V-shaped rare-earth (RE) rotor magnets, a PMSM with deep V-shaped ferrite rotor magnets, and a synchronous reluctance machine (SynRM) with four layers of conforming flux barriers are compared for an application in a 48-V mild hybrid electric car. The optimization of the deep V-shaped ferrite PMSM automatically resulted in a spoke-type PM layout for maximum torque production. Yet, an optimized SynRM with conforming flux barriers was achieved that could produce a higher torque than ferrite PMSM. One machine technology is selected and is subsequently subjected to a large-scale FE model-based drive-cycle design optimization. Various pole-slot combinations are methodically compared in terms of drive-cycle losses, active material cost, torque ripple, and PM demagnetization level. More than 20,000 designs were analyzed over ten energy-centric torque-speed points to identify an optimal design solution. The results of multi-physics analysis incorporating electromagnetics, computational fluid dynamics (CFD), and structural analyses are provided, including a study on two different water jacket concepts. A final design is prototyped and initial experimental results are provided.

The demand for increased power and improved fuel economy are driving changes in alternator technology for automotive applications. To meet these demands requires a drive system with capabilities of torque assist, regenerative braking, and power generation to supply vehicle loads while keeping the battery charged. Furthermore, to minimize add-on cost, the system must be air-cooled and operate at 12V with the same or smaller packaging footprint of the current alternator. In this paper, a low cost 12V 4kW air-cooled IPM drive system for automotive electric power management is presented. The design and analysis in terms of machine, inverter, controller and control algorithm are discussed in detail. Thermal performance of system under different operating conditions are studied. Finally a prototype drive system was built and tested and found to meet the cost, performance and packaging requirements.

The fuel injection system strongly affects the engine combustion phenomena which determines pollutant emissions, combustion noise and fuel efficiency. Many studies have shown the advantages of using small quantity and closely-spaced multiple injections per combustion cycle for emission reduction and fuel efficiency improvement. However, closely-spaced multiple injections using electromagnetic fuel injectors, which predominate in almost all gasoline engines, are challenging, as there is residual energy (flux) in the injector coil when the injector is re-energized. The residual flux causes over-fueling in the subsequent injection event resulting in unacceptable injection instability. In this paper, we develop a simple and highly accurate dynamic model of a solenoid in electromagnetic fuel injectors to predict the residual energy/flux. Eddy current effect and magnetic saturation are considered to model the transient behavior of flux. The model parameters are derived from physical variables, which render the model easy to tune/calibrate. The predicted flux from the model showed very good agreement with experimental results over typical fuel injection profiles. The model is an enabler for model based fuel injector control to achieve accurate fuel metering in closely space multiple injection applications. The method is also applicable to solenoid in other applications, e.g., solenoid actuators in robotics, variable force solenoid in clutch systems, and so on.

The demand for increased power and improved fuel economy are driving changes in alternator technology for automotive applications. To meet these demands requires a machine with capabilities of torque assist, regenerative braking, and power generation to supply vehicle loads while keeping the battery charged. Furthermore, to minimize add-on cost, the system must be air-cooled and operate at 12V with the same or smaller packaging footprint of the current alternator. In this paper, two low cost 12V 4kW air-cooled PM-assisted synchronous reluctance machine designs for automotive electric power management are presented. The design and analysis in terms of electromagnetic, mechanical and thermal behaviors are discussed in detail. One of the machines was built and tested and found to meet the cost, performance and packaging requirements.

Future automobiles will be equipped with x-by-wire systems to improve reliability, safety, and performance. The fault-tolerant capability of these systems is crucial due to their safety critical nature. Three fault-tolerant inverter topologies for permanent magnet brushless direct current motor drives suitable for automotive x-by-wire systems are analyzed. A figure of merit taking into account both cost and postfault performance is developed for these drives. Simulation results of the two most promising topologies for various inverter faults are presented. The drive topology with the highest postfault performance and cost effectiveness is built and evaluated experimentally.

A novel automated design algorithm for application-based optimization of permanent magnet (PM) machines is presented in this paper. The proposed algorithm features precise performance evaluation of the potentially heavily saturated machines at high-energy-throughput operating zones using finite element (FE) techniques. First, the energy consumption function associated with the machine's operating cycle is efficiently modeled by a number of representative load points using a k-means clustering algorithm. Subsequently, a new approach is developed to assess the performance of the machine at each representative load point with proper control to conform to practical operational constraints imposed by voltage and current limits of the motor-drive system. The developed algorithm is applicable to the optimization of any configuration of PM and synchronous reluctance motors over any conceivable operating cycle. Its effectiveness is demonstrated by optimizing the well-established reference/benchmark design represented by the 2004 Toyota Prius IPM motor configuration over a compound operating cycle consisting of common US driving schedules.

Large-scale design optimization of electric machines is oftentimes practiced to achieve a set of objectives, such as the minimization of cost and power loss, under a set of constraints, such as maximum permissible torque ripple. Accordingly, the design optimization of electric machines can be regarded as a constrained optimization problem (COP). Evolutionary algorithms (EA) used in the design optimization of electric machines including the Differential Evolution, which has received considerable attention during recent years, are unconstrained optimization methods that need additional mechanisms to handle COPs. In this paper, a new optimization algorithm that features Combined Multi-objective Optimization with Differential Evolution (CMODE) has been developed and implemented in the design optimization of electric machines. A thorough comparison is conducted between the two counterpart optimization algorithms, CMODE and DE, to demonstrate the CMODEs superiority in terms of convergence rate and constraint handling. More importantly, CMODE requires a less number of simultaneous processing units which makes its implementation best suited for state-of-the-art desktop computers reducing the need for High Performance Computing systems and associated software licenses.

Future automobiles will be equipped with by-wire systems to improve reliability, safety and performance. The fault tolerant capability of these systems is crucial due to their safety critical nature. Three fault tolerant inverter topologies for permanent magnet brushless dc motor drives suitable for automotive x-by-wire systems are analyzed. A figure of merit taking into account both cost and post-fault performance is developed for these drives. Simulation results of the two most promising topologies for various inverter faults are presented. The drive topology with the highest post-fault performance and cost effectiveness is built and evaluated experimentally.

Semi-active suspension systems using real time damping (RTD) provide significant improvement in vehicle ride and handling without the high cost of fully active suspensions. RTD systems require a variable rate damper (shock absorber), a relative velocity sensor (RVS), and a controller. To reduce the cost of such systems, a method for integrating a moving magnet relative velocity sensor directly into the shock absorber is presented. This integrated relative velocity sensor (IRVS) uses existing hydraulic and mechanical components as part of its magnetic circuit to reduce part count and cost. Sensitivity to key design parameters is analyzed using a finite element model. The IRVS is self energizing, requires no signal processing electronics, and can be integrated into standard shock absorber configurations. Prototype sensors were tested on a vehicle and provided excellent performance under all testing conditions.

Capacitors consisting of oppositely charged inductor bars sandwiched between two parallel plates of glass are well suited for applications requiring the detection of water. The sensitivity to water on the glass surface is a complication function of both the geometry and dielectric properties of the sensor and its environment. A closed-form analytical model suitable for use in the optimization of such sensors is presented. The model is successfully applied to the design optimization of an example and is verified using a finite-different model and test results. >