Showing papers on "Damping torque published in 2016"

Electronic Stability Control Based on Motor Driving and Braking Torque Distribution for a Four In-Wheel Motor Drive Electric Vehicle

Abstract: An electronic stability control (ESC) algorithm is proposed for a four in-wheel motor independent-drive electric vehicle (4MIDEV) utilizing motor driving and regenerative braking torque distribution control to improve vehicle stability. A stability judgment controller, an upper level controller, and a torque distribution algorithm are designed for the ESC system. The stability judgment controller is designed to generate the desired yaw rate and sideslip angle for vehicle stability, and the control mode, which is normal driving mode or ESC mode, is set according to the driver inputs and measurement signal inputs. The upper level controller consists of a speed tracking controller, a yaw moment controller, and four wheel-slip controllers to calculate the desired value of traction force, the desired value of yaw moment, and the four respective net torque inputs of the four in-wheel motors. The torque distribution algorithm is designed to generate each motor driving torque or regenerative braking torque input for each wheel. An average torque distribution strategy, a tire-dynamic-load-based torque distribution strategy, and a minimum-objective-function-based optimal torque distribution strategy are used separately in the torque distribution algorithm to control the motor driving torque or regenerative braking torque for vehicle stability enhancement. The proposed ESC algorithm was implemented and evaluated in a CarSim vehicle model and a MATLAB/Simulink control model. The three proposed torque distribution strategies can be used to regulate the vehicle to perform the following tasks: “single lane change,” “double lane change,” and “snake lane change.” The simulation studies show that the yaw rate error root mean square [RMS $(\gamma-\gamma_\mathrm{-des})$ ] decreased, on average, by 75 percent using the proposed optimal torque distribution algorithm compared with that without using stability control.

A Simplified Finite-State Predictive Direct Torque Control for Induction Motor Drive

Abstract: Finite-state predictive torque control (FS-PTC) is computationally expensive, since it uses all voltage vectors (VVs) available from a power converter for prediction and actuation. The computational burden is rapidly increased with the number of VVs and objectives to be controlled. Moreover, designing a cost function with more than two control objectives is a complex task. This paper proposes a simplified algorithm based on a new direct torque control (DTC) switching table to reduce the number of VVs to be predicted and objectives to be controlled. The new switching table also assists to reduce average switching frequency and its variation range. As a result, the cost function is simplified by not requiring to include the frequency term. Experimental results show that the average execution time and the average switching frequency for the proposed algorithm are greatly reduced without affecting the torque and flux performances achieved in the conventional FS-PTC.

Analysis of Torque Capability and Quality in Vernier Permanent-Magnet Machines

Abstract: Vernier permanent-magnet (VPM) machines have been obtaining a lot of attention over the past few years due to several advantages, such as their high torque density and simple mechanical structures. Moreover, it is found that the torque ripple of VPM machines is ultralow, even without specific design measures such as a short pitch, skewing slots/poles, magnet shaping technology, etc. This paper presents theoretical analysis and comprehensive simulations on the torque ripple of VPM machines. First, a general instantaneous torque equation of VPM machines is proposed to analyze torque features and the effect of parameters on the torque performance of VPM machines. Subsequently, based on the general torque equation and a finite-element algorithm, it is verified that torque smoothness is the inherent characteristic of VPM machines, and the torque ripple of VPM machines can be below 0.2%. Furthermore, it is demonstrated that the torque density of a VPM machine is 40% larger than that of a regular permanent-magnet machine. All these advantages demonstrate that VPM machines can obtain much better steady and dynamic drive performance. Finally, all the theoretical analyses are verified by experiments on a VPM prototype.

A Fast and Parametric Torque Distribution Strategy for Four-Wheel-Drive Energy-Efficient Electric Vehicles

Abstract: Electric vehicles (EVs) with four individually controlled drivetrains are over-actuated systems, and therefore, the total wheel torque and yaw moment demands can be realized through an infinite number of feasible wheel torque combinations. Hence, an energy-efficient torque distribution among the four drivetrains is crucial for reducing the drivetrain power losses and extending driving range. In this paper, the optimal torque distribution is formulated as the solution of a parametric optimization problem, depending on the vehicle speed. An analytical solution is provided for the case of equal drivetrains, under the experimentally confirmed hypothesis that the drivetrain power losses are strictly monotonically increasing with the torque demand. The easily implementable and computationally fast wheel torque distribution algorithm is validated by simulations and experiments on an EV demonstrator, along driving cycles and cornering maneuvers. The results show considerable energy savings compared to alternative torque distribution strategies.

Feedback Linearization Direct Torque Control With Reduced Torque and Flux Ripples for IPMSM Drives

Abstract: This paper designs a feedback linearization direct torque control (FL-DTC) based on the space vector modulation (SVM) which can noticeably reduce the electromagnetic torque and stator flux ripples that affect the system efficiency on interior permanent magnet synchronous motor (IPMSM) drives. First, a decoupled linear IPMSM model with two state variables (i.e., the stator flux and electromagnetic torque) is derived to implement the proposed FL-DTC strategy that preserves some advantages such as fast torque control, high torque at low speed, and fast speed response. Also, the proposed technique greatly alleviates the torque and stator flux ripples which are the major concerns of the classical hysteresis-based DTC scheme and have an effect on the stator current distortion. The system stability with the designed FL-DTC method is mathematically analyzed using the Lyapunov stability theory. Finally, the effectiveness of the proposed control law is validated through simulation results with MATLAB/Simulink and experimental results obtained from a prototype 1-HP IPMSM drive with TI TMS320F28335 digital signal processor (DSP). The verification results demonstrate that the proposed FL-DTC scheme achieves faster torque response, smaller torque ripple, and lower stator flux ripple than the conventional SVM-based PI-DTC approach under parameter uncertainties and external disturbances.

Model Predictive Torque Control for Torque Ripple Compensation in Variable-Speed PMSMs

Abstract: This paper presents a new and simple finite-control set model predictive control strategy to reduce the torque ripple in permanent-magnet synchronous machines (PMSMs). The method is based on minimizing a cost function that considers the flux linkage torque harmonics obtained from a discrete-time model of the machine. The power converter switching state that minimizes this cost function is selected and applied during a whole sampling period. Additionally, it is proposed to mitigate the other source of torque ripple, known as cogging-torque, using a feed-forward signal applied to the torque control loop. A hybrid method that uses the output information from an observer and look-up table is presented to obtain a good cogging-torque estimation and thus an accurate mitigation of this disturbance torque at low rotational speed. Experimental results demonstrate the good performance of the torque ripple compensation methods presented in this paper.

A Method to Examine the Impact of Grid Connection of the DFIGs on Power System Electromechanical Oscillation Modes

Abstract: Grid connection of a DFIG for power generation changes the power system load flow and introduces dynamic interactions with the synchronous generators (SGs). A method is proposed in this paper for the separate examination of the impact of those two affecting factors, the change of load flow and dynamic interaction brought about by the DFIG, on the electromechanical oscillation modes of a power system. The method is developed on the establishment of a “closed-loop control system” type of state space model of the power system where the DFIG is treated as the feedback controller. The established model unambiguously indicates that the impact of the DFIG can be examined separately: (1) With the DFIG being modelled as a constant power injection into the system, the impact of the load flow change brought about by the DFIG on the oscillation modes is determined; (2) The impact of the dynamic interactions introduced by the DFIG is estimated by calculating the contribution of the damping torque from the DFIG with its full dynamics being considered. Thus a more detailed examination on and deeper insight into the impact of grid connection of the DFIGs on power system small-signal angular stability is obtained by using the proposed method.

Reduction of Cogging Torque and Torque Ripple in Interior PM Machines With Asymmetrical V-Type Rotor Design

Abstract: High cogging torque is a common drawback of the interior permanent magnet machine. In this paper, a novel technique is adopted to reduce cogging torque and torque ripple by using an asymmetrical V-type rotor configuration. First, the analysis modes are presented, and the proposed rotor is optimized by the hybrid design of experiment. A satisfactory set of parameters is determined. Next, the cogging torque and the torque ripple of the proposed model are compared with those of the basic model. The results demonstrate that the cogging torque and the torque ripple are reduced significantly by the adoption of the proposed rotor. Then, the performance of the proposed model rotating clockwise is compared that of the proposed model rotating counterclockwise to evaluate the effectiveness of the proposed rotor. Finally, the validity of the proposed method is confirmed by experiment.

Driver-mounted torque sensing mechanism

Abstract: A robotically-controlled drive unit includes a torque sensing mechanism to measure the torque applied to a rotatable body that is configured to tension an actuation tendon to operate robotic surgical tools and catheters. The drive unit includes a motor unit that generates an output torque in response to a robotic control signal. A beam element generates a reactive torque in response to the output torque generated by the rotor, and a force sensor detects the reactive torque and communicates the magnitude of the reactive torque to a robotic controller. The drive unit may further include a mechanism to perform bi-directional torque sensing, examples of which include additional force sensors and compression springs.

Constant Switching Frequency Based Direct Torque Control of Interior Permanent Magnet Synchronous Motors With Reduced Ripples and Fast Torque Dynamics

Abstract: The conventional direct torque control (DTC) features control structure simplicity, fast dynamic response, and parameter robustness. Nevertheless, it suffers from the problems of variable switching frequency and large torque ripples. This paper presents a modified DTC algorithm for interior permanent magnet synchronous motor drives with fast torque dynamics and constant switching frequency. The aforementioned problems are alleviated by adding a PI torque regulator to autonomously alter the effective duty cycle of the applied voltage vector. As a result, a constant switching frequency and also reduced torque ripples are obtained while retaining the benefits of the classical DTC. In addition, the torque dynamic response is further improved by introducing a modified switching table during transient conditions. By incorporating the modified switching table, the torque dynamic response is superior to that of the classical DTC. Simulation and experiment results included confirm the effectiveness of the proposed method.

Direct Torque Control for VSI–PMSMs Using Four-Dimensional Switching-Table

Abstract: In this paper, a direct torque control using a four-dimensional switching-table (4D-ST) is proposed for the voltage source inverter–permanent magnet synchronous motor drive system. The proposed strategy takes a number of virtual vectors, of which magnitude and angle can be configured freely, as candidate vectors. By taking advantage of the variety of the virtual vector, the proposed strategy can obtain superior steady-state and dynamic performance. To choose the optimal vector from all of virtual vectors, first quantify the change rule of the torque and stator flux generated by each different virtual vector, and then take the magnitude and angle of the virtual vector, stator flux angle, and the quantificational factor as four dimensions to establish 4D-ST; by analyzing the distributed laws of quantificational factors in 4D-ST, we can compress 4D-ST and propose a quarter selector to choose the optimal vector accurately and rapidly. By taking the step function instead of the hysteresis comparator as the torque and flux controller, the direct torque control using 4D-ST can be realized. Finally, numerical simulations and experiments with prototype are carried out to validate the feasibility and effectiveness of the proposed strategy.

Three-Level Inverter-Fed Direct Torque Control of IPMSM With Constant Switching Frequency and Torque Ripple Reduction

Abstract: The major drawbacks of classical direct torque control (DTC) are large torque ripples and variable switching frequency. Torque ripples in DTC drives can be attenuated if a three-level inverter is employed instead of a two-level inverter. Nevertheless, torque ripples can still be large if low switching frequencies are used. To alleviate these problems, a constant-switching-frequency-based three-level DTC (3L-DTC) algorithm is presented in this paper. Operating at low, constant switching frequency, the proposed algorithm is effective in reducing torque ripples under all operating conditions. Detailed analysis and design guidelines for the proposed 3L-DTC algorithm are presented. In addition, typical issues associated with the three-level inverter, such as neutral-point voltage fluctuations and smooth voltage vector switching, are addressed. Experimental results are presented to validate the effectiveness of the proposed method.

Design, Analysis, and Experimental Evaluation of a Double Coil Magnetorheological Fluid Damper

Abstract: A magnetorheological (MR) damper is one of the most advanced devices used in a semiactive control system to mitigate unwanted vibration because the damping force can be controlled by changing the viscosity of the internal magnetorheological (MR) fluids. This study proposes a typical double coil MR damper where the damping force and dynamic range were derived from a quasistatic model based on the Bingham model of MR fluid. A finite element model was built to study the performance of this double coil MR damper by investigating seven different piston configurations, including the numbers and shapes of their chamfered ends. The objective function of an optimization problem was proposed and then an optimization procedure was constructed using the ANSYS parametric design language (APDL) to obtain the optimal damping performance of a double coil MR damper. Furthermore, experimental tests were also carried out, and the effects of the same direction and reverse direction of the currents on the damping forces were also analyzed. The relevant results of this analysis can easily be extended to the design of other types of MR dampers.

Torque Density Improvement of Doubly Salient Electromagnetic Machine With Asymmetric Current Control

Abstract: Due to the introduction of field winding, the doubly salient electromagnetic (DSEM) machine is featured with good torque production capability. However, this capability is limited by the problems of the phase current reversal and excessive back- electromotive force with traditional control methods. In this paper, a new control method, namely asymmetric current control (ASCC), is proposed to further improve the output torque. Two control angles α and γ are introduced to implement the current-angle control. Simultaneously, the pulse width modulation control is utilized to shape the waveform of phase current. Consequently, the torque is increased drastically because of more effective phase current waveforms, which presents the asymmetry of positive and negative half period. Furthermore, the reluctance torque resulting from the interaction between self-inductance and asymmetric phase current exerts favorable effects on the torque output. By field-circuit-coupled analysis, the ASCC method for a 1.3 kW prototype is analyzed and compared with other traditional control methods. Laboratory testing of the 1.3 kW DSEM machine driven by the new control method confirms the validity of theoretical analysis and simulation improvement of torque. The simulation and experimental results show that the torque and power density can be improved to 1.5 times by the proposed control method.

Analytical Prediction of Torque Ripple in Surface-Mounted Permanent Magnet Motors Due to Manufacturing Variations

Abstract: In the production of surface-mounted permanent magnet machines, manufacturing tolerances also contribute to torque ripple. Additional harmonics of low electrical orders are created in the torque spectrum. Slight manufacturing variations develop asymmetry conditions in the rotor as well as in the stator. Finite element models can be used to analyze the magnitude of pulsating torque generated due to these asymmetries. However, due to its random nature, lack of periodicity, and symmetry, it is time consuming to study the problem with numerical methods for its uneven geometry that does not allow reduced geometrical models. Moreover, the experimental verification of all possible variations would be very challenging as it would require part dimensioning and part sorting a large quantity of motor builds and finally testing of all samples. Therefore, in this paper an analytical model is presented to study the effect of such imbalance on the torque ripple. The model shows an agreement against finite element models and also with experimental results when predicting torque harmonics that come from asymmetries.

OCTSF for torque ripple minimisation in SRMs

Abstract: In this study, a new online compensation of torque sharing function (OCTSF) method is proposed to minimise the torque ripple in switched reluctance motors (SRMs). For SRMs, the torque ripple is a serious issue which is mainly produced by the overlapped conduction phases in the commutation region. In conventional TSF-based direct instantaneous torque control system, the incoming phase torque cannot achieve its reference torque perfectly and the outgoing phase torque also cannot drop down to its torque reference quickly in the commutation region. Hence, in order to minimise the torque ripple, the TSF of the outgoing phase is proposed to realise the positive compensation at the start of the commutation and the TSF of the incoming phase is used to achieve the negative compensation at the end of the commutation. Moreover, compared with the hard-chopping mode in conventional TSF strategies, the hard-chopping and soft-chopping modes are both employed in the proposed scheme to reduce the switching actions and switching loss. The simulation and experiments based on a 750 W three-phase 12/8 SRM are carried out to verify the effectiveness of the proposed OCTSF method.

Prototype and test of a novel rotary magnetorheological damper based on helical flow

Abstract: To increase the output damping torque of a rotary magnetorheological (MR) damper with limited geometrical space, a novel rotary MR damper based on helical flow is proposed. A new working mode, helical flow mode, is discussed and applied to enlarge the flow path of MR fluids. The helical flow can improve the performance of the rotary damper by enlarging the length of the active region. Based on the idea, a rotary MR damper is designed. The rotary MR damper contains a spiral piston, dual-coil core, a rotating cylinder and a stator cylinder. Based on the Bingham model, the output damping torque of the damper is analytically derived. The finite element method (FEM) is applied to calculate the magnetic field of the active region. The multi-objective optimal design method is adopted to obtain the optimal geometric parameters. A prototype is fabricated based on the optimal results. To validate the proposed rotary MR damper, two types of experiments including the low rotation speed and the high rotation speed are investigated. The results show that the proposed rotary MR damper has high torque density and compact structure. The helical flow mode can increase the output damping torque with limited space.

Shaft Torque Limiting Control Using Shaft Torque Compensator for Two-Inertia Elastic System With Backlash

Abstract: This paper aims to present a solution for torsional vibration suppression and shaft torque limitation simultaneously in servo system with backlash The existence of backlash, which would make conventional notch filter invalid, will aggravate the mechanical vibration and bring the risk of unsafety to the system In order to solve that problem, a novel shaft torque compensator is proposed, which would make the system similar to a rigid system with one inertia What is more, this compensator can limit shaft torque as expected, making the system relatively safe under any situation with different load inertias and torques The limiting control is based on the adaptive online identification of load inertia in order to improve robustness of the system and ensure not only the accuracy, but also the arbitrariness of shaft torque limit Simulation and experimental results are presented to illustrate the favorable behavior of the drive with the robust shaft torque compensator

Design and experiments of a novel magneto-rheological damper featuring bifold flow mode

Abstract: This study presents design and fabrication of a novel magneto-rheological (MR) damper with bifold flow mode gap to improve damping performance. The proposed MR damper is featured by inner flow mode gap connected to the outer flow mode gap through the feedback hole. A mathematical model of the damping force is established for the proposed MR damper and the magnetic circuit has been analyzed with the finite element method, which is used to validate the principle of the proposed MR damper. A conventional MR damper is fabricated with the same dimensions (radius, length) of the piston and is experimentally compared to confirm advantages of the proposed MR damper. The mechanical performance of the proposed MR damper is experimentally investigated and compared with the results by mathematical model and finite element analysis. The research results show that the controllable damping force and equivalent damping of the MR damper with bifold flow mode gap are much larger than those of the conventional MR damper.

Robust ESS-Based Stabilizer Design for Damping Inter-Area Oscillations in Multimachine Power Systems

Abstract: In this paper, a robust approach to the energy storage system (ESS)-based stabilizer is proposed to select its installation location, feedback signals, and damping control loop, and to tune the stabilizer parameters. Based on the linearized model of the power system with ESS and application of damping torque analysis (DTA), the maximum of all minimum damping torque indices (DTIs) under multi-operational conditions is used as the index for selecting ESS installation locations, feedback signals and damping control loops. The operational condition for the minimum DTI provides the condition for tuning the ESS-based stabilizer parameters for robust operation. And a proper compensation angle is selected by a robust method to design the ESS-based stabilizer parameters. The eigenvalue analysis and non-linear simulation results of a four-machine power system and New England ten-machine power system with ESS show that power system oscillations are suppressed effectively and robustly by the ESS-based stabilizer.

Genetic algorithm based current optimization for torque ripple reduction of interior PMSMs

Abstract: This paper investigates the torque ripple modeling and minimization for interior permanent magnet synchronous machine (PMSM). At first, a novel torque ripple model is proposed. In this model, both spatial harmonics of magnet flux linkage and current time harmonics induced by machine drive are considered, which includes the torque ripples resulted from magnet torque, reluctance torque and cogging torque. Based on the proposed model, a novel genetic algorithm (GA) based dq-axis harmonic currents optimization approach is proposed for torque ripple minimization. In this approach, the GA is applied to optimize both the magnitude and phase of the harmonic currents to achieve the objectives of: 1) minimizing the peak-to-peak torque ripple; 2) minimizing the sum of squares of the harmonic currents; and 3) maximizing the average torque component produced by the injected harmonic currents. The results demonstrate that the magnitude of the harmonic current can be significantly reduced by considering the phase angles of these harmonic currents as the optimization parameters. This leads to further suppression of the torque ripple when compared to that of a case where phase angles are not considered in the optimization. Also, an increase of the average torque is achieved when the optimum harmonic currents are injected. The proposed model and approach are evaluated with both numerical and experimental investigations on a laboratory interior PMSM.

Simple Design Approach for Low Torque Ripple and High Output Torque Synchronous Reluctance Motors

Abstract: The rotor design of Synchronous Reluctance Motors (SynRMs) has a large effect on their efficiency, torque density and torque ripple. In order to achieve a good compromise between these three goals, an optimized rotor geometry is necessary. A finite element method (FEM) is a good tool for the optimization. However, the computation time is an obstacle as there are many geometrical parameters to be optimized. The flux-barrier widths and angles are the two most crucial parameters for the SynRM output torque and torque ripple. This paper proposes an easy-to-use set of parametrized equations to select appropriate values for these two rotor parameters. With these equations, the reader can design a SynRM of distributed windings with a low torque ripple and with a better average torque. The methodology is valid for a wide range of SynRMs. To check the validity of the proposed equations, the sensitivity analysis for the variation of these two parameters on the SynRM torque and torque ripple is carried out. In addition, the analysis in this paper gives insight into the behavior of the machine as a function of these two parameters. Furthermore, the torque and torque ripple of SynRMs having a rotor with three, four and five flux-barriers are compared with three literature approaches. The comparison shows that the proposed equations are effective in choosing the flux-barrier angles and widths for low torque ripple and better average torque. Experimental results have been obtained to confirm the FEM results and to validate the methodology for choosing the rotor parameters.

Analysis of Simplifications Applied in Vibration Damping Modelling for a Passive Car Shock Absorber

Abstract: The paper presents results of research on hydraulic automotive shock absorbers. The considerations provided in the paper indicate certain flaws and simplifications resulting from the fact that damping characteristics are assumed as the function of input velocity only, which is the case of simulation studies. An important aspect taken into account when determining parameters of damping performed by car shock absorbers at a testing station is the permissible range of characteristics of a shock absorber of the same type. The aim of this study was to determine the damping characteristics entailing the stroke value. The stroke and rotary velocities were selected in a manner enabling that, for different combinations, the same maximum linear velocity can be obtained. Thus the influence of excitation parameters, such as the stroke value, on force versus displacement and force versus velocity diagrams was determined. The 3D characteristics presented as the damping surface in the stoke and the linear velocity function were determined. An analysis of the results addressed in the paper highlights the impact of such factors on the profile of closed loop graphs of damping forces and point-type damping characteristics.

MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations

Abstract: This paper describes a semi-active vibration absorber (SVA) concept based on a real-time controlled magnetorheological damper (MR-SVA) for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD). Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.

Design of a permanent-magnet flux-modulated machine with a high torque density and high power factor

Abstract: This study presents a novel approach to the design process of a permanent-magnet flux-modulated machine by simultaneously focusing on the machine major advantage and disadvantage, that is, the high torque density and low power factor. The machine can be designed with a high power factor while retaining the high torque density. To do so, they both need to be described precisely. The torque equation is improved by considering the stator-winding leakage flux. It determines the relation between the geometric parameters and the torque more accurately. The power-factor equation is derived from the electric equivalent circuit representing the simplest description of the machine. The machine geometry optimised with the design of experiments via Taguchi methods assures the best possible performance within the set limitations. It is shown that using the proposed design process makes the permanent-magnet flux-modulated machine more appropriate than the classical synchronous machine for the direct drive applications requiring a high torque density, low weight and high efficiency.