Chandra S. Namuduri

Controller-induced parasitic torque ripples in a PM synchronous motor

PM synchronous machines with a sinusoidal back EMF are ideally capable of torque-ripple-free operation. However, parasitic torque ripples can still be induced from motor design and controller implementation. This paper focuses on a systematic analysis of possible torque ripples in a PM synchronous machine drive resulting from limitations in the motor controller. It takes into account the effects of finite encoder resolution, controller CPU word length, current sensing errors and inverter PWM switching. Approaches for analyzing and calculating torque ripples from each of those sources have been developed. Characteristics of the various parasitic torque ripples are discussed. Experimental and simulation data to verify important results are also presented.

Load dump transient control of a 42 V automotive generator

This paper describes the concept, design, modeling, simulation and performance of an innovative fast field regulator developed for a high-power 42 V automotive generator, to minimize the load-dump energy and improve its reliability. In laboratory tests, a 3 kW 42 V Lundell generator, with conventional field regulator, failed the load-dump transient test. This research analyzed the root cause of the failure by analyzing the load-dump energy, using SABER modeling and simulation, which have been verified by tests. Various concept alternatives for minimizing the load-dump energy have been identified and an innovative and cost-effective solution based on fast field control was selected for development of the proof-of-concept hardware. The proposed technique reduced the load-dump transient duration by more than a factor of 5, resulting in a reduction of load-dump energy by more than 75%. This eliminated the need for paralleling multiple avalanche diodes in the alternator rectifier bridge to handle the transient energy, resulting in a smaller package and increased reliability at a lower cost. The proposed fast field control can be further applied to minimize the load-dump transients in all belted alternator starters (BAS) that use a wound-field machine.

Electromechanical Regenerative Actuator With Fault-Tolerance Capability for Automotive Chassis Applications

This paper investigates an electromechanical regenerative actuator (EMR) for automotive chassis applications. The actuator system comprises an electric machine, a ball screw and a controller. The designs of these three components are studied first. Control algorithms were then developed for both converter and inverter topologies. A prototype actuator was fabricated and tested in the lab. It was found that the regenerative system achieves the required performance, and also has the capability to regenerate power to improve real world fuel economy.

Onboard unidirectional automotive G2V battery charger using sine charging and its effect on li-ion batteries

On-board battery chargers are used in electric and plug-in-hybrid electric vehicles (EV/PHEV) for charging the battery from the utility power grid. Various cost-effective topologies with reduced mass are now being proposed for the on-board charger to charge the Li-ion batteries used these vehicles. This paper proposes two unidirectional battery charger topologies with a novel single stage control that provide rectified sinusoidal charging currents to the battery, thus eliminating the need for the bulky dc bus electrolytic capacitor of conventional systems. The advantages of eliminating the electrolytic capacitors include reduced size, mass and cost of the charger and improved reliability. Simulations of the voltage and current waveforms during normal operation are presented. An accelerated cycle charge/discharge testing of the battery cells with low frequency current ripple was conducted to determine the impact of the low frequency 120 Hz ripple on the Li-ion battery capacity and life. The test results are encouraging and show negligible impact of sine charging on Li-ion battery performance.

Impact of position sensor accuracy on the performance of IPM drives

In this paper, the influence of rotor position sensor accuracy on the performance of an Interior Permanent Magnet (IPM) motor drive for automotive propulsion is presented. Analytical equations describing the torque production in IPM machines show the need for rotor position feedback with high accuracy and resolution, especially for operation in the flux weakening region. Finite element analysis was performed to substantiate this conclusion and also to estimate the torque and power degradation due to the position sensor error. The dynamic angle error of various high resolution/accuracy sensors was measured on the test bench at various operating speeds and temperatures and the measured data was used for computing the impact of angle error on the torque ripple. The details of these results are presented in the paper.

Electromechanical regenerative actuator with fault tolerance capability for automotive chassis applications

This paper investigates an electromechanical regenerative actuator (EMR) for automotive chassis applications. The actuator system comprises an electric machine, a ball screw and a controller. The designs of these three components are studied first. Control algorithms were then developed for both converter and inverter topologies. A prototype actuator was fabricated and tested in the lab. It was found that the regenerative system achieves the required performance, and also has the capability to regenerate power to improve real world fuel economy.

Impact Performance of Magnetorheological Fluids

As part of an emerging effort in what is now termed the area of mechamatronics [1], an effort was begun to assess the suitability of MR (magnetorheological) material based devices for impact energy management applications. A fundamental property of MR materials is that their yield stress alters almost instantaneously (and proportionally) to changes in the strength of an applied magnetic field. Based on this property, MR based devices, if found suitable, would be desirable for impact energy management applications because of attendant response tailorability. However, it was identified that prior to adopting MR based devices for impact energy management applications several key issues needed to be addressed. The present study focused on one of the most significant of these, the verification of the tunability of the response of such devices at stroking velocities representative of vehicular crashes. Impact tests using a free-flight drop tower facility were conducted on an MR based energy absorber (shock absorber) for a range of impact velocities and magnetic field strengths. Results demonstrated that over the range of impact velocities tested — 1.0 to 10 m/s — the stroking force/energy absorption exhibited by the device remained dependent on and thus could be modified by changes in the strength of the applied magnetic field.Copyright

High speed performance of PM machine with reconfigurable winding

This paper examines high speed performance of a permanent magnet (PM) machine with a reconfigurable winding (RW). First, the variations of machine parameters due to winding reconfiguration are presented and their impacts on drive system performance are investigated. To further understand system behavior, the reconfigurable ratio is set as a variable, and its effect on saliency ratio, flux weakening range, torque, output power and losses are studied in detail. Saturation effect is also taken into account. To verify the simulation analysis, a PM machine with reconfigurable winding was built and tested in a lab. The test results show that RW system can achieve up to 84% power boost with 57% copper loss reduction in high speed.

Impact of position sensor accuracy on the performance of propulsion IPM drives

This paper addresses the influence of rotor position sensor accuracy on the performance of the Interior Permanent Magnet (IPM) motor drives used for automotive propulsion application. Analytical equations for the torque production in IPM machines show that the machine output torque drops sharply with angle error at high operating speeds. This also shows the need for rotor position feedback with high accuracy and resolution, especially for operation in the flux weakening region. Finite element analysis was performed to substantiate this conclusion and also to estimate the torque and power degradation due to the position sensor error. The torque/speed curves on an experimental drive system was measured on the dyno to corroborate the analytical and simulation results. The dynamic angle error of a typical high resolution/accuracy sensor was measured on the test bench at various operating speeds and temperatures and the measured data was used for computing the impact of angle error on the torque ripple. The details of these results are presented in the paper.

Comparison of the influence of PM drive system with voltage adaptation or machine winding reconfiguration on HEV/EV applications

This paper examines the performance benefits of four IPM drive system configurations for HEV/EV applications with the following features for controlling the machine voltage: 1) boosted inverter, 2) Y/Δ, 3) series/parallel (S/P) and 4) tapped reconfigurable windings. The four systems are modeled and their impact on drive system performance is investigated. Additionally, comparisons in terms of flux weakening capability, torque, output power, losses, number of machine winding leads and number of added components are studied in detail. Detailed set of simulation and experiments results were used for assessing the performance benefits. The trade-off study shows that the drive system with tapped reconfigurable winding results in the favorable cost/benefit ratio with similar inverter voltage/current limits.