Nejila Parspour

Torque Ripple Minimization Using Online Estimation of the Stator Resistances With Consideration of Magnetic Saturation

The tolerances and limitations in design and manufacturing of both electrical motors and inverters lead to parasitic resistances in the phases. Therefore, the phase resistances are asymmetric, which causes an asymmetry among the phase currents and a resulting increase in torque ripple. This paper proposes a novel scheme for torque ripple minimization using online estimation of unbalanced stator resistances of a permanent-magnet synchronous motor. The identifiability of the stator resistances in a nonlinear model is investigated by employing a sensitivity analysis. The phase resistances are estimated by recursive least squares in the rotating reference frame in real time. Using the estimated resistances, torque ripple reduction is achieved by a compensation scheme in the stationary reference frame. The effectiveness of the proposed scheme is verified in both simulation and test-bench experiments. Results with and without consideration of magnetic saturation are compared.

Design of a 3 kW primary power supply unit for inductive charging systems optimized for the compatibility to receiving units with 20 kw rated power

This paper presents a power unit for use in the primary side of 3 kW rated inductive charging system. The objective is the design of 3 kW rated primary sides which are compatible to 20 kW rated secondary side receiving units inside electric vehicles. The motivation arises from the consideration that 3 kW and 20 kW charging stations should be kept compatible. Compatible especially in the way that vehicles with 20 kW rated receiving units should be able to use 3 kW charging stations. The basis for the design of the 3 kW system is a series-compensated secondary receiving coil without an additional DC/DC-converter stage between a B4 rectifier and battery with a rated power of 20 kW. The absence of a DC/DC stage allows lower weight and installation space in the vehicle, but the possibility for impedance matching is missing. The system behavior is investigated analytically, so that all currents and voltages, as well as the reactive power in both compensation networks can be calculated depending on the given systems parameter, such as the inductance of the secondary coil, the coupling factor, the operation frequency and the transferred power. It is shown that the operation point with the lowest reactive power, and thus least losses in the coils and compensation capacitors, strongly depends on the design of the receiving unit. Since the receiving unit is designed for a transferred power of 20 kW, an operation with 3 kW will result in a significantly lower efficiency. Therefore a solution is presented, to shift the ideal operation point of the secondary side system from 20 kW to a much lower value. That way, the 3 kW system is able to operate very close to the shifted ideal operation point.

Position control of a permanent magnet transverse flux machine with very high force density for industrial automation systems

This paper presents a new position control method for transverse flux machines. Since the torque ripple is one of the most important reasons for the low dispersal of transverse flux machines, a great importance has to be attached to subordinate torque control. Based on a look-up table, the torque is controlled by a time-discrete converter state changing. Speed and position are superordinately controlled by state regulators without steady state control deviation.

Analytical computation method of transverse flux permanent magnet excited machines via nodal analysis

This paper is about an analytical computation method for a transverse flux permanent magnet excited machine. The analytical computation method makes use of a magnetic equivalent circuit with lumped elements considering saturation. The magnetic values of the magnetic equivalent circuit are solved via nodal analysis. Having the entire magnetic equivalent circuit of one pole pair of the transverse flux permanent magnet excited machine electromagnetically solved, the resulting torque can be computed by applying virtual displacement. The calculation is based on the derivation of the air gaps permeance. Although the analytical calculation method includes the calculation for all positions of the rotor with different currents, it merely lasts few seconds. These results will be compared with the results of a finite element analysis simulation.

Contribution to the development of positioning tolerant inductive charging systems

In this paper a winding layout for use in inductive charging systems is introduced. The proposed layout leads to an extension of the positioning tolerance of the system. The layout of the winding and the inductive charging system is looked at before the background of use in electric vehicles. The necessary reactive power compensation and control technology will be discussed as far as they are related to the layout of the windings.

Hardware emulation of transverse flux machines based on an analytical model considering saturation effects

Transverse flux machines have advantages at high torque densities and low speed. On the other hand, the torque ripple of a transverse flux machine is complicated to control. For many control methods the precise knowledge of the machines behavior is essential. To describe this behavior and to get more detailed information about processes inside the machine, an analytical model is designed which uses the analogy between magnetic permeances and electric capacitors, coupled by a gyrator. At the input of the model are the phase voltages and the mechanical load. The outputs are the force and the rotor position. The model can be used for both verification of control methods and obtaining information of the machines behavior. The results of the new analytical model are compared with measurements on a linear prototype and emphasize the capability of the model.

Design of a transverse flux machine as joint drive for an articulated six-axis robot arm

This paper presents requirements on a articulated robot arm in service robotics and the derivation of requirements on a single joint of this arm. A modular concept with joint modules, each one realizing one axis of the robot arm connected by intermediate elements is proposed. Furthermore, the integration of a permanent magnet excited transverse flux machine as joint drive in this application is discussed. Transverse flux machines typically offer a high torque density at low speed. As torque demand increases from wrist to shoulder joint and speed demand decreases at the same time, this paper concentrates on the design of a shoulder joint module, where the integration of a transverse flux machine seems to be most promising. A design of a transverse flux machine as drive of an exemplary shoulder joint is proposed and results from a three dimensional finite element simulation are presented.

Torque-vectoring stability control of a four wheel drive electric vehicle

The electrification of the automotive powertrain provides completely new control options regarding the distribution of individual wheel moments. The integration of up to four independently controlled electrical engines in a vehicle allows individual adjustment of driving and braking torques to the current driving situation. Thus, electrical engines create a new kind of dynamic vehicle control. Unlike the Electronic Stability Control (ESC), Torque-Vectoring influences the vehicle dynamics not only through braking forces but also by setting up positive driving torques allowing for a new way of dynamic driving. In this paper two different control algorithms are developed in order to calculate a desired yaw moment to influence vehicle dynamics. The Torque-Vectoring algorithm distributes the yaw moment among the four wheels. The evaluation of the vehicle dynamic simulation has shown that the best results regarding the control quality can be reached by using the Fuzzy control algorithm to optimize the driving stability in extreme driving situations.

Analytical core loss models for electrical steel in power electronic applications

This paper shows different state of the art analytical iron loss models and a modified model, which combines the modified Bertotti model with the form factor of Grätzer. A loss comparison under sinusoidal and non-sinusoidal voltage excitation in the frequency range from 50Hz to 1000Hz without minor loops is shown. Measurements show that the accuracy of some models is high, independent from the shape of the voltage and easy to apply for engineers designing inductive components in power electronic applications.

Online estimation of the stator resistances of a PMSM with consideration of magnetic saturation

Precise knowledge of the resistance in each phase of a permanent magnet synchronous machine renders possible the performance optimization of a PMSM drive. It can be applied to torque ripple minimization, fault diagnosis for inverter, and high quality monitoring of e.g. temperature or the aging condition of electrical contacts. This paper provides a method to accurately estimate each individual stator phase resistance of a three-phase PMSM. The resistances are identified using recursive least squares minimization in real time. The estimation algorithm is based on a PMSM model in rotational reference frame. To achieve a high precision estimation in all points of operation the motor model takes account of magnetic saturation and cross-magnetization that are captured by offline estimation. The reliability of the proposed scheme is verified in simulations and test-bench experiments.