Showing papers on "Damping torque published in 2014"

Extended-speed low-ripple torque control of switched reluctance motor drives

Abstract: Various embodiments are described herein for an extended-speed low-ripple torque control of a switched reluctance motor (SRM) using online torque sharing function (TSF). Two operational modes of an online TSF are defined during the commutation: In Mode I, absolute value of rate of change of flux linkage (ARCFL) of incoming phase is higher than outgoing phase; in Mode II, ARCFL of outgoing phase is higher than incoming phase. To compensate the torque error produced by imperfect tracking of phase current, a proportional and integral compensator with torque error is added to the torque reference of outgoing phase in Mode I and incoming phase in Mode II. Therefore, the total torque is determined by the phase with lower ARCFL rather than the phase with higher ARCFL as in conventional TSFs.

Wheel Torque Distribution Criteria for Electric Vehicles With Torque-Vectoring Differentials

Abstract: The continuous and precise modulation of the driving and braking torques of each wheel is considered the ultimate goal for controlling the performance of a vehicle in steady-state and transient conditions To do so, dedicated torque-vectoring (TV) controllers that allow optimal wheel torque distribution under all possible driving conditions have to be developed Commonly, vehicle TV controllers are based on a hierarchical approach, consisting of a high-level supervisory controller that evaluates a corrective yaw moment and a low-level controller that defines the individual wheel torque reference values The problem of the optimal individual wheel torque distribution for a particular driving condition can be solved through an optimization-based control-allocation (CA) algorithm, which must rely on the appropriate selection of the objective function With a newly developed offline optimization procedure, this paper assesses the performance of alternative objective functions for the optimal wheel torque distribution of a four-wheel-drive (4WD) fully electric vehicle Results show that objective functions based on the minimum tire slip criterion provide better control performance than functions based on energy efficiency

A Novel Direct Torque Control of Matrix Converter-Fed PMSM Drives Using Duty Cycle Control for Torque Ripple Reduction

Abstract: A novel direct torque control (DTC) strategy using duty cycle optimization is proposed for matrix converter (MC)-based permanent-magnet synchronous motor (PMSM) drive system, which is characterized by low torque ripples, no need for rotational coordinate transformation, and fixed switching frequency. Analytical expressions of change rates of torque and flux of PMSM as a function of MC voltage vectors are derived. An enhanced switching table is established by means of discretization and averaging, in which changes of torque and flux caused by voltage vectors are shown explicitly. Then, the proposed MC-fed DTC algorithm is implemented based on the table. Numerical simulation and experiments with a prototype are carried out. Both simulation and experimental results demonstrate that remarkable torque ripple reduction, more than 30%, has been achieved. As a result, the proposed strategy is proved to be effective in reducing torque ripples for MC-based PMSM drives.

Direct Torque Control of Permanent-Magnet Synchronous Machine Drives With a Simple Duty Ratio Regulator

Abstract: The conventional switching-table-based direct-torque-controlled (DTC) ac machine drive is usually afflicted by large torque ripple, as well as steady-state error of torque. The existing methods, which optimize the duty ratio of the active vector, are usually complicated and parameter dependent. Based on the analysis of instantaneous variation rates of stator flux and torque of each converter output voltage vector, a simple and effective method considering the effect of machine angular velocity is proposed to obtain the duty ratio. The experimental results carried on a dSPACE platform with a laboratory prototype of the permanent-magnet machine verify that the proposed duty-based DTC method can achieve excellent transient response, less torque ripple, and less steady-state error, without resorting to the complicated control method over a wide range of operating regions.

A Novel Method for Minimization of Cogging Torque and Torque Ripple for Interior Permanent Magnet Synchronous Motor

Abstract: This paper proposes a method to minimize the cogging torque and torque ripple of an interior permanent magnet synchronous motor by adopting asymmetric barrier design and inverting lamination method. The analysis method for cogging torque and torque ripple is suggested using finite-element method. An asymmetric barrier in a permanent magnet rotor is optimally designed without permanent magnet skew. This proposed design for low cogging torque and torque ripple has an advantage over skew design from a manufacturing point of view. The proposed model is compared with the skew model and nonskew model by calculating torque characteristics to determine the more effective method to reduce torque distortion.

Variable Switching Point Predictive Torque Control of Induction Machines

Abstract: This paper introduces an approach to include a variable switching time point into predictive torque control (PTC). In PTC, the switching frequency is limited by the sampling frequency; its theoretical maximum value is half the sampling frequency. However, in reality the switching frequency is lower than this value, and thus, high current and torque ripples occur compared with modulator-based control methods. In order to overcome this, an optimization problem is formulated and solved in real time. Thereby, apart from the regulation of the torque and the flux magnitude to their references, an additional control objective should be met: the minimization of the torque ripple. To do so, the time point at which the switches of the inverter should change state is calculated. Further advantages of the proposed method include the design flexibility and great performance during transients. Experimental results that verify the performance of the presented control strategy are included.

Optimal Design of a Novel V-Type Interior Permanent Magnet Motor with Assisted Barriers for the Improvement of Torque Characteristics

Abstract: This paper performs a study on the optimal design of V-type interior permanent magnet motors (VIPMMs), in which the rotor is equipped with assisted barriers for the improvement of average torque and torque ripple. The approach differs from the conventional interior permanent magnet motors, in which the reluctance torque due to saliency reaches a maximum value at a current phase angle located 45 electrical degrees with respect to the maximum value obtained from the magnetic torque produced by the rotor magnets. The adoption of assisted barriers is employed to improve the torque production by creating rotor asymmetry to allow the reluctance torque and the magnetic torque reach a maximum value near or at the same current phase angle. To evaluate the contribution, the frozen permeability method is utilized to segregate the torque into its reluctance and magnetic torque components. First, an iterative optimization is performed on a concept design of a 6/4 VIPMM for demonstrating the design principle based on finite element method. Then, the VIPMM is further optimized by algorithms, such as the kriging method and genetic algorithm for improving the torque characteristics and efficiency. As a result, the optimal VIPMM with assisted barriers shows the substantially improved performance compared with a conventional design.

Average Torque Improvement of Interior Permanent-Magnet Machine Using Third Harmonic in Rotor Shape

Abstract: A rotor shaping technique with optimal third harmonic is presented to enhance the average torque of interior permanent-magnet (IPM) machines in this paper. The optimal value of third harmonic injected into the rotor outer surface shape has been derived and further confirmed by both finite-element analyses and experiments. The impact of the optimal third harmonic to the rotor shape on the electromagnetic performance, including harmonics in the back electromotive forces, cogging torque, average torque, and torque ripple, is investigated. It is demonstrated that without any modification of the costly rare earth permanent magnet employed for the inverse-cosine-shaped rotor, the average torque of the machine of an inverse cosine injected with an optimal third-harmonic-shaped rotor can be improved by 6%. Simultaneously, the torque ripple remains almost unchanged, and the saliency ratio is also improved, further boosting the average torque. Finally, the machines with both conventional and optimal third harmonic rotors are prototyped and tested to validate the analysis.

Torque Enhancement of Surface-Mounted Permanent Magnet Machine Using Third-Order Harmonic

Abstract: This work presents a permanent magnet (PM) shaping technique with optimal third harmonic to improve the output torque without deteriorating the torque ripple in surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape for maximum torque improvement is analytically derived and confirmed by finite-element analysis. Further, the influence of magnet edge thickness on the airgap field distribution is investigated and utilized to compensate the inter-pole flux leakage and curvature effect. It is found that the optimal third harmonic is 1/6 of the fundamental one. For the SPM machines having rotors without shaping, Sine shaping, Sine shaping with third harmonic injected, the electromagnetic performance, including the back-EMF waveforms, cogging torque, average torque, and torque ripple are compared. It is demonstrated that the average torque in the machine of a Sine shaping with an optimal third harmonic injected can be improved by >9%, while the torque ripple remains similar to that of the one with Sine shaping. Finally, the machines with both conventional (without shaping) and optimal third harmonic PM rotors are prototyped and measured to validate the analyses.

Torque Analysis of Interior Permanent-Magnet Synchronous Motors by Considering Cross-Magnetization: Variation in Torque Components With Permanent-Magnet Configurations

Abstract: The variation in torque of interior permanent-magnet synchronous motors with driving conditions and magnet configurations is investigated by considering the cross-magnetization caused by magnetic saturation. The torque is decomposed into four components, i.e., the main magnet torque, main reluctance torque, cross-magnet torque, and cross-reluctance torque. It is revealed that the cross-magnet torque is always negative and this component reduces the total torque of the motor. This effect becomes large in the case of the V-type magnet configuration. The magnet configuration, which reduces the cross-magnetization effect, is also investigated by considering the mechanical strength against the centrifugal force caused by high-speed rotation. The validity of the calculation is confirmed by experiments.

Torque Improvement of Five-Phase Surface-Mounted Permanent Magnet Machine Using Third-Order Harmonic

Abstract: This paper presents optimal third harmonics in both permanent magnet (PM) shaping and current waveform to improve the output torque of five-phase surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape and current waveform for maximum torque improvement is analytically derived and validated by both finite element (FE) analyses and experiments. It is found that the optimal third harmonic is 1/6 of the fundamental one for both PM shape and current waveform. For the five-phase SPM machines having rotors without shaping, Sine shaping, or Sine shaping with third harmonic injected, the electromagnetic performance including the back EMF waveform, cogging torque, average torque, torque ripple, copper loss, iron loss, impact on power inverter, and demagnetization withstand capability are compared. It is demonstrated that, although the copper loss and iron loss increase due to additional third harmonic in the winding current and magnet shape, the average torque with optimal third harmonics injected in PM shaping and current waveform can be improved by >30% while the torque ripple and remains similar to that of the one with Sine shaping. In addition, this will reduce the dc bus voltage while maintaining the machine torque density. Furthermore, the machine with Sine and Sine+3rd rotors presents much better demagnetization withstand capability performance than conventional rotor.

Control of current-induced spin-orbit effects in a ferromagnetic heterostructure by electric field

Abstract: We study the effects of electrostatic gating on the current-induced phenomena in ultrathin ferromagnet/heavy metal heterostructures. We utilize heterodyne detection and analysis of symmetry with respect to the direction of the magnetic field to separate electric field contributions to the magnetic anisotropy, current-induced fieldlike torque, and damping torque. Analysis of the electric field effects allows us to estimate the Rashba and the spin Hall contributions to the current-induced phenomena. Electrostatic gating can provide insight into the spin-orbit phenomena, and enable new functionalities in spintronic devices.

Energy-harvesting linear MR damper: prototyping and testing

Abstract: The present study is concerned with an energy-harvesting linear MR (EH-LMR) damper which is able to recover energy from external excitations using an electromagnetic energy extractor, and to adjust itself to excitations by varying the damping characteristics. The device has three main components: an MR part having a damper piston assembly movable in relation to the damper cylinder under an external excitation, a power generator to produce electrical power according to the relative movement between the damper piston and the cylinder assembly, and a conditioning electronics unit to interface directly with the generator and the MR damper. The EH-LMR damper integrates energy harvesting, dynamic sensor and MR damping technologies in a single device.The objective of the study is to get a better insight into the structure of EH-LMR damper components, to investigate the performance of each component and a device as a whole, and to compare results of experimental study against numerical data obtained in simulations conducted at the design stage. The research work demonstrates that the proposed EH-LMR damper provides a smart and compact solution with the potential of application to vibration isolation. The advantage of the device is its adaptability to external excitations and the fact that it does not need any extra power supply unit or sensor on account of its self-powered and self-sensing capabilities.

Analysis of torque capability and quality in vernier permanent magnet machines

Abstract: This paper presents theoretical analysis and comprehensive simulations about average torque and pulsation torque of vernier permanent magnet (VPM) machine. A general torque equation is proposed which is used to analyze torque features and the parameters effect on torque performance of VPM machines in this paper. Based on the general torque equation and finite element algorithm, it is found that smooth torque is the inherent performance of VPM machines. Furthermore, It is demonstrated that the torque density of the VPM machine is larger than that of a regular commercial PM machine by almost 60%. All these advantages demonstrate that the VPM machines can obtain much better steady and dynamic drive performance. In order to validate theoretical analysis, a prototype is built, and more experiments will be available.

Variable-Flux Machine Torque Estimation and Pulsating Torque Mitigation During Magnetization State Manipulation

Abstract: This paper focuses on dynamic control, under loaded conditions, of the magnetization state of suitably designed variable-flux (VF) permanent-magnet (PM) machines. Such VF-PM machines have been shown to achieve low loss operation over a wide range of load and speed. For this type of machine, the PM flux linkage varies during the magnetization manipulation process. Published magnetization techniques have occurred at zero load conditions and thus did not generate torque pulsations. However, under loaded conditions, the existing methods would produce unwanted torque pulsation. This paper proposes a parameter insensitive method to solve this issue. This method generates a decoupling current command that is calculated from accurately estimated stator flux linkage. Accurate flux estimation, i.e., insensitive to inductance saturation and PM flux linkage variation (e.g., temperature or magnetization level) is achieved by using the voltage disturbance estimated by a closed-loop stator current vector observer. In both simulations and experiments, it is shown that even during magnetization processes under loaded conditions, the flux can be estimated correctly, and smooth torque output can be achieved.

Vibration control using ATMD and site measurements on the Shanghai World Financial Center Tower

Abstract: SUMMARY The Shanghai World Financial Center Tower is the tallest landmark building in mainland China, with a height of 492 m. In order to mitigate wind-induced vibration, a set of two identical damping devices was installed at the 90th floor. The damping devices are active tuned mass dampers: under wind loading, the active control feature is enabled, while the active control feature becomes disabled under earthquake conditions, and the damping devices function as passive tuned mass dampers. The dynamic parameters of the damping devices, structural analysis results and field measurement results under different vibration scenarios are presented in this paper. The analysis and field measurement results show that the damping devices performed well and had the following characteristics: they increased the damping ratio up to eight times in field measurements and reduced the wind acceleration response up to 60% when wind speed is below the designed value in the analysis. Copyright © 2012 John Wiley & Sons, Ltd.

An optimised tuned mass damper/harvester device

Abstract: SUMMARY Much work has been conducted on vibration absorbers, such as tuned mass dampers (TMD), where significant energy is extracted from a structure Traditionally, this energy is dissipated through the devices as heat In this paper, the concept of recovering some of this energy electrically and reuse it for structural control or health monitoring is investigated The energy-dissipating damper of a TMD is replaced with an electromagnetic device in order to transform mechanical vibration into electrical energy That gives the possibility of controlled damping force whilst generating useful electrical energy Both analytical and experimental results from an adaptive and a semi-active tuned mass damper/harvester are presented The obtained results suggest that sufficient energy might be harvested for the device to tune itself to optimise vibration suppression Copyright © 2014 John Wiley & Sons, Ltd

Magnet Shape Optimization to Reduce Pulsating Torque for a Five-Phase Permanent-Magnet Low-Speed Machine

Abstract: Five-phase surface-mounted permanent-magnet machines can inherently produce a smooth electromagnetic torque which can be increased when using third harmonic current injection. To really take advantage of these characteristics, the rotor magnets can be shaped to obtain a back electromotive force with large third harmonic term. This is the scope of this paper. For the design specifications of a low-speed marine propulsion machine, the following objective must be achieved: to significantly mitigate the pulsating torque without reducing the average torque bearing in mind the solution where the rotor is made with full pole-pitch magnets. An analytical field computation, called equivalent coil method, is developed to quickly explore the magnet geometries. Thus a procedure to optimize small trapezoid notches at the surface of the pole magnets is performed. Referring to the classical fully pole-pitch magnet shape, the solution found allows a substantial reduction of the pulsating torque without reducing the torque density. Furthermore, with regard to an equivalent three-phase machine, for the same copper losses, the average torque of the optimized five-phase machine can be potentially higher if the third harmonic current injection is implemented.

Evaluation of Generator Damping Using Oscillation Energy Dissipation and the Connection With Modal Analysis

Abstract: A newly proposed oscillation energy analysis method for power system low frequency oscillation is further developed. The oscillation energy flow in a generator and the energy dissipations of the field winding and the damper winding are studied. The oscillation energy flows into the field winding and the damper winding actually correspond to the electric energy transferred to the windings. The average powers of energy dissipation for oscillation modes with different frequencies are decoupled. For an individual mode, the energy dissipation of generator is computed using eigenvector and energy dissipation coefficient is obtained. The real-part of eigenvalue is negatively proportional to the sum of energy dissipation coefficients of all generators. It means the composite damping of the system comes from the energy dissipations of all generators. Especially in the single-machine system, the energy dissipation coefficient is equal to the damping torque coefficient. The consistency of oscillation energy analysis with damping torque analysis and modal analysis is verified. The energy dissipation leads to a new understanding of damping in power system and can be used for quantitative evaluation of generator damping in both offline and online applications.

A Seminumerical Finite-Element Postprocessing Torque Ripple Analysis Technique for Synchronous Electric Machines Utilizing the Air-Gap Maxwell Stress Tensor

Abstract: A novel method to calculate the harmonic torque components in synchronous machines is presented. Harmonic torque components create a torque ripple, which is undesirable in many applications. This torque ripple is a major cause of acoustic noise and vibration and can limit the machine's application range. A seminumerical method is developed to calculate and analyze harmonic torque components based on Maxwell stress tensor theory. Development of the Maxwell stress expressions leads to a simple algebraic expression for the calculation. Finite-element (FE) analysis is used to determine the equation variables. It is shown that postprocessing of the FE solution provides valuable information regarding the composition of the torque waveform, based upon field harmonics, which was previously unavailable. A deeper insight can be gained into more direct electromagnetic design changes to reduce torque ripple in synchronous machines, improving their torque quality. As an example, the developed method is applied to a synchronous reluctance machine with fractional slot concentrated windings that is known to exhibit high torque ripple.

Identification of Machining Process Damping Using Output-Only Modal Analysis

Abstract: The existing chatter stability prediction algorithms fail in low-speed machining of difficult to cut alloys, unless process damping contributed by the tool flank face–finish surface contact is considered. This paper presents a new method in predicting the material dependent process damping coefficient from chatter free orthogonal cutting tests. An equivalent process damping coefficient of the dynamic system is estimated from the frequency domain decomposition (FDD) of the vibration signals measured during stable cutting tests. Subsequently, the specific indentation force of the workpiece material is identified from the process damping coefficients obtained over a range of cutting speeds. The specific indentation force coefficient is used in an explicit formula of process damping which considers the radius and clearance angle of the cutting edge. It is experimentally shown that when the proposed process damping model is included, the accuracy of chatter stability predictions in turning and milling improves significantly at low cutting speeds.

Mitigation of Multimodal Subsynchronous Resonance Via Controlled Injection of Supersynchronous and Subsynchronous Currents

Abstract: This paper presents a novel approach to analyze the mechanism of torsional interaction (TI) and its solution for series-capacitor-compensated power systems. The relationship between the oscillation of the generator shaft and the consequent electromagnetic torque is deduced by a time-domain analysis. It is revealed that the subsynchronous currents caused by torsional oscillations provide negative damping electromagnetic torque and are the cause of TI. A family of subsynchronous dampers (SSDs) is proposed, which is based on the controlled injection of supersynchronous and subsynchronous damping currents into the generator stator. The design procedure of subsynchronous damping controller (SSDC) of series SSD is elaborated. Eigenvalue analysis and simulations for the IEEE first benchmark model (FBM) have verified the effectiveness of the proposed SSDs in solving the multimodal subsynchronous resonance problem.

Cogging Torque Reduction of Axial Field Flux-Switching Permanent Magnet Machine by Adding Magnetic Bridge in Stator Tooth

Abstract: Axial field flux-switching permanent magnet machine (AFFSPMM) is a novel stator PM machine with high torque density and efficiency. The cogging torque in AFFSPMM is larger than that in the traditional PM machine because of the double salient structure. In order to decrease the cogging torque, the analytical expression of the cogging torque is deduced and a cogging torque reduction method by adding magnetic bridge in adjacent stator tooth is proposed. Based on the 3-D finite-element (FE) method, the influence of the magnetic bridge thickness on the cogging torque and the output torque is analyzed and compared with the rotor skewing and notching methods. The influence of the stator tooth and rotor pole width on the output torque is studied. The 3-D FE analysis is compared with the experimental results. The research results show that the proposed method is effective in the reduction of cogging torque for all kinds of stator structures. Moreover, the cogging torque can decrease greatly and the average output torque decreases slightly when combined with the optimization of the stator tooth width and rotor pole width.

Time-Optimal and Loss-Minimizing Deadbeat-Direct Torque and Flux Control for Interior Permanent-Magnet Synchronous Machines

Abstract: This paper presents time-optimal control of an interior permanent-magnet synchronous machine (IPMSM) in voltage-limited and current-limited conditions using deadbeatdirect torque and flux control (DB-DTFC). A commanded air-gap torque and flux can be achieved by the end of each pulse width modulation (PWM) period using the DB-DTFC. However, it may take several PWM periods to achieve a desired torque that is physically infeasible in one step when operating near the voltage limit. The large torque command can be shaped as a feasible trajectory so that the deadbeat torque and flux is achieved for every sample time instant (switching period) along the trajectory. In this paper, the feasible trajectory is dynamically optimized to achieve a large torque command in the shortest time during the voltage-limited and current-limited operation. A loss-minimizing stator flux linkage is used during steady-state operation to reduce the computational complexity of the dynamic optimization and to operate the IPMSM at the loss-minimizing condition. The voltage-limited and current-limited operation of IPMSM drives is evaluated in both the simulation and experiment in this paper.

Damping of Full-Scale Stay Cable with Viscous Damper: Experiment and Analysis:

Abstract: A full-scale cable vibration mitigation experiment was conducted by means of a 215.58-meters-long stay cable attached with a pair of viscous dampers. Test results showed that the damping of the cable was greatly increased after the installation of viscous dampers. It was found that the obtained damping of the cable with viscous dampers depended on the amplitude, and the maximum damping was smaller than the maximum attainable damping. The viscous damper showed nonlinear behaviors regarding the mechanical performances, as well as the interior stiffness. Therefore, the effect of the interior stiffness of a damper on the cable damping was also studied by using an analytical formulation of the complex eigenvalue problem. An engineering approximation concerning the damping of a taut cable with a viscous damper was proposed, where the influence of the interior stiffness was taken into account. The analytical approximate formulations were further extended to nonlinear viscous damper based on the assumption of equ...

Engine bench system

Abstract: Provided is an engine bench system capable of performing a racing test with good precision. A test body is separated into an engine main body and intermediate coupling body for connecting a crankshaft and an output shaft of the dynamometer. The engine bench system is provided with: a shaft torque sensor for detecting torsional torque; a shaft torque command generation apparatus for calculating a dynamo-side shaft torque command value by summing an engine-side shaft torque command value, and a torque value proportional to the moment of inertia of the intermediate coupling body; and a shaft torque controller for generating a torque control signal on the basis of the dynamo-side shaft torque command value and the output value of the shaft torque sensor.

Improving Vehicle Lateral Stability Based on Variable Stiffness and Damping Suspension System via MR Damper

Abstract: The capability of a variable stiffness and damping (VSVD) suspension system via a magnetorheological (MR) damper on improving vehicle lateral stability is investigated in this paper. First, a type of the VSVD suspension system is briefly introduced with the application of variable damping to realize the capability of VSVD. Then, variable damping via the MR damper is extended, and the characteristics of damping force are presented with the Bouc-Wen model. Then, the proposed VSVD system is inserted into a full vehicle model as a front suspension system to control tire normal forces. A control strategy composed of a fuzzy controller that the output is wheel slip ratio and a simple on/off controller to model the application of VSVD is developed to illustrate its ability in improving vehicle stability. It is shown from simulation that VSVD can increase tire normal forces and make vehicles present better performance on lateral stability.