High Torque Research Articles

A novel auxetic stator winding to improve the performance of permanent magnet synchronous electric motors

High efficiency and torque density in permanent magnet synchronous motors (PMSMs) have contributed to their increasing popularity. Nonetheless, these advantages are compromised by higher vibration levels resulting from the torque ripple issue and magnetic flux density in the stator, causing magnetic forces on the stator surface. In this study, a new smart shape for the stator winding is proposed which reduces unwanted torque vibration and the overall magnetic flux density while keeping the same motor efficiency. The proposed windings shape is designed based on the auxetic principle and a locally resonant mechanism (LRM). Afterward, the proposed and original PMSM models are compared by looking at the average torque, total losses, torque ripple, flux density, output power, and motor efficiency under different speed operating conditions. In addition, the sensitivity analyses of the proposed model reveal the influence of auxetic structural parameters and initial mechanical angle on the system’s performance, which can be utilized to control the physical and mechanical properties of the system. According to the results, the designed model reduces torque ripple and magnetic flux density in the stator region by 41.38% and 4.70%, respectively, while the motor efficiency remains unaffected. The present work offers a potentially robust and affordable solution for regulating the vibration behavior of electric motors without impacting power efficiency.

Open-Phase-Tolerant Online Current References for Maximum Torque Range and Minimum Loss With Current and Torque-Ripple Limits for n-Phase Nonsalient PMSMs With Nonsinusoidal Back EMF

Multiphase permanent-magnet synchronous machines (PMSMs) with nonsinusoidal back-electromotive force (back-EMF) offer high fault tolerance and torque density for electric vehicles. Most current-reference generation methods either minimize stator copper loss (SCL) or maximize achievable torque. Optimization of both goals is accomplished by full-torque-range minimum-loss (FRML) strategies, but so far just for sinusoidal back-EMF. Thus, FRML for nonsinusoidal back-EMF should be sought. Moreover, many methods are only suitable for healthy conditions or specific machines, harmonics, or open-phase-fault (OPF) scenarios. Additionally, the torque range may be extended by permitting torque ripple or (transiently) greater rms current, but this approach is not general nor FRML yet. This paper proposes online FRML current-reference generation for multiphase PMSMs with nonsinusoidal back-EMF: nonsinusoidal-back-EMF FRML (NSBE-FRML). When the torque reference is feasible, minimum SCL is attained while maximizing the achievable torque (i.e., FRML). For higher torque references, the instantaneous torque deviation is minimized, and the torque reference is saturated in consecutive samples limiting the torque ripple to a pre-specified threshold. Furthermore, the rms current is limited after transient overload by automatically decreasing the torque reference. The NSBE-FRML is suitable for any harmonics, healthy/OPF conditions, and multiphase PMSMs with negligible saliency ratio. Experiments are performed with a six-phase PMSM.

A C-Core Connected Two-Phase Switched Reluctance Motor With Embedded Permanent Magnets for Developed Torque Enhancement

Conventional switched reluctance motors (SRMs) face challenges like low torque density and high noise. To overcome these challenges, the structure of SRMs can be modified. This paper introduces a new hybrid-excited 16/18 two-phase SRM with a C-core structure. Each pole of the C-core has two teeth, which develop a positive torque during the rotor rotation; this enhances the torque and torque density of the motor. To show the merits of the proposed SRM with PMs, its static and dynamic characteristics, including flux density, flux-linkage, and torque, are obtained and compared with the SRM with no PMs, the 8/12 two-phase conventional SRM, and other motors with the same volume; a significant match was achieved. Finally, both proposed SRMs were prototyped and tested. Comparing the simulation and test results elucidates that the proposed SRM with PMs has unique high output power, torque, and efficiency.

Hybrid-excited magnetic gear topology for improved gear efficiency at increasing rotor speed

Concentric magnetic gear (CMG) and rotating pole piece magnetic gear (RPMG) are two topologies that produce high torque density in magnetic gear (MG) for electrical machine. However, due to the eddy current loss, both suffer high losses when operated in high speed condition. Thus, to overcome this matter, a second flux source is proposed to the RPMG stator. This approach will then transform it into hybrid excited magnetic gear (HMG) topology to achieve higher gear efficiency. Three tooth slot designs were considered, and the outcome of these designs are summarized and ranked. The proposed structures are assessed using JMAG designer 2D finite element software in high speed condition. It is found that partially closed slot structure achieved the highest gear efficiency of 95.34% and average outer rotor torque of 115.64 N.m.

Design of an Integrated Magnetorheological Fluid Brake Axial Flux Permanent Magnet Machine

This paper presents the design and performance of an integrated magnetorheological fluid brake axial flux permanent magnet (IMRFB-AFPM) machine with two switchable operation modes: rotation and brake modes while the machine has two kinds of windings: armature winding in axial stators and braking winding in radial stator. In rotation mode, this machine is equal to a conventional AFPM machine with high torque density. When switching to brake mode, MR fluid is excited by braking winding and applies large damping stress to the rotor to brake it. This paper illustrates the machine topology, operation principles, and design flow of the proposed machine. Then, this paper analyzes the torque generation mechanism in two modes and applies parameters optimization to improve the torque capability of each mode. Due to the independence of the magnetic flux path, the parameters optimization is divided into two parts: AFPM part and IMRFB part. After the optimization process, the electromagnetic performances of the optimal IMRFB-AFPM machine are analyzed by finite element (FE) analysis. Finally, a prototype machine with the optimal geometric parameters is manufactured and verified experimentally. The experiment results agree well with FE analysis results, validating the feasibility and practicability of the proposed design.

Modified switching control of SRM drives for electric vehicles application with torque ripple reduction

The switched reluctance motor (SRM) offers extensive prospects, particularly within the realm of electric vehicles (EVs). Its robust construction, wide speed range, high torque density, and efficiency provide significant advantages that surpass other motors. Nonetheless, controlling these motors is more intricate when compared to conventional DC brushed or AC motors. This complexity arises due to the non-linear inductance characteristics of SRMs, resulting in undesirable effects like torque ripple, vibrations, and noise. Using the conventional full-bridge inverter, three switching approaches are highlighted for various operating modes of an EV. This aims to reduce costs and the number of switching pulses, leading to a more compact system, elimination of dead time, and switching losses. The MATLAB/Simulink platform was utilized to examine the operational effectiveness of a three-phase 6/4 poles SRM drive. Additionally, this paper focuses on mitigating torque ripple concerns by employing an adaptive neuro-fuzzy inference system (ANFIS) controller that has better efficiency and superior responses compared to conventional controllers such as fuzzy logic control (FLC) and proportional integral (PI) control. The results of the simulation encourage the practical implementation of the system, which is the next step in the author’s research.

High Torque teno virus load and outcome of patients undergoing allogeneic hematopoietic cell transplantation.

Quantification of Torque teno virus (TTV) load emerged as a marker of immunosuppression. Associations of TTV load with complications and survival after allogeneic hematopoietic cell transplantation (allo-HCT) were controversial in published studies. In this prospective study, we aimed to identify factors influencing TTV load after allo-HCT and to determine whether the TTV load is associated with complications or outcomes. Seventy allo-HCT recipients were included. TTV DNA load was quantified in 469 plasma samples of 70 patients from Day (D) 15 before D120 after transplantation. The influence of transplant characteristics on TTV load and the associations of TTV load with viral infections, acute graft versus host disease, mortality, and relapse were analyzed. More than 80% of patients were TTV DNA positive from D30 after transplantation onwards. Median TTV load increased between D30 and D60 post-transplantation. Patients with lymphoid malignancies had higher TTV load than those with myeloid malignancies. Myeloablative conditioning was associated with higher TTV loads. Patients with no measurable residual disease at transplant had higher TTV loads. High TTV load at D90 post-transplantation was associated with lower overall survival and at D120 post-transplantation was associated with higher relapse rate. In conclusion, TTV load at time points later than D90 after allo-HCT may be useful to assess prognosis.

Topology Optimization of a Surface Permanent Magnet Motor With High Torque Density

Topology Optimization of a Surface Permanent Magnet Motor With High Torque Density

A Dual-Permanent-Magnet Machine With Asymmetric Stator Teeth-Tips

Dual-permanent-magnet machines (DPMMs) have attracted increasing attentions due to their merit of high torque density. Nevertheless, DPMMs suffer from low PM utilization ratio owing to large PM consumption. To improve the situation, this paper presents a DPMM with asymmetric stator teeth-tips, termed as AST-DPMM. The key of the proposed design is to arrange wide and narrow stator teeth-tips alternatively. By building an analytical model of the AST-DPMM, the impact of asymmetric stator teeth-tips is investigated. It is found the asymmetric stator teeth-tips can enhance the working harmonics by generating new magnetomotive force harmonics and permeance harmonics. Hence, it can achieve high torque density and improve PM utilization ratio simultaneously. The performance comparisons together with other machines are conducted to evaluate the investigated AST-DPMM. Finally, a prototype of the AST-DPMM is fabricated, and the experimental testing is conducted to verify the proposed ideas.

Design and Analysis of the High Torque Density Circumferentially Excited Permanent Magnet Motor Based on PSO

Design and Analysis of the High Torque Density Circumferentially Excited Permanent Magnet Motor Based on PSO

Design and feasibility analysis of magnetorheological flexible joint for upper limb rehabilitation

Traditional upper limb rehabilitation robots have several disadvantageous. For example, they can only conduct rehabilitation training along predetermined trajectories, their safety systems are unreliable, and they lack the ability to adjust or train the affected limb based on the expected torque of the human body. To overcome these limitations, this study proposes a flexible safety system for joint rehabilitation utilising magnetorheological (MR) fluid. MR damper inverters offer significant advantages, including high torque, rapid response, controllable flexibility, and safety assurance. The range of motion trajectories can be adjusted using a four-lever hinge mechanism. The necessary driving force is provided by the motor actuator, and the MR damper imparts flexibility and variable damping characteristics to the output torque. The system uses a force/position impedance safety-control method, and using an internal position closed-loop controller, the MR upper limb rehabilitation flexible joint guides the affected limb to a safe position. A simulation is performed to verify the accuracy of the system’s motion torque and position. Extensive research has been conducted on the safe rehabilitation outcomes of the upper limb rehabilitation system under three working conditions (step, incremental, and equation) involving the interaction moment of the affected limb. Simulation and experimental results demonstrate that the MR damper effectively controls the upper limb rehabilitation system to achieve the desired results, even when subjected to incremental and abrupt interaction forces from the patient. The tracking accuracy error remains within the range of 3%–7% for a certain period, confirming the safety and feasibility of the MR-based upper limb rehabilitation robot design.

Modeling of thrust force and torque in drilling aluminum 7050

Abstract The aluminum AA7050 alloy has high toughness and high strength. Despite the high machinability of the AA7050 alloy, hole quality can vary according to tool geometry and drilling parameters. This study investigated the effects of different cutting parameters and three different drill point angles on thrust force and torque. Numerical analyses for thrust force and torque were performed using the finite element method. The lowest thrust force and the highest torque were obtained with the drill at 130° drill point angle, while the highest cutting force and lowest torque were obtained with the drill at 118° drill point angle. There is an average difference of 5.37 and 6.9 % between the experimental and analysis values for thrust forces and torque, respectively, and the applicability of the finite element model has been proven. In the last part of the study, thrust force and torque are modeled with artificial neural networks. The statistical accuracy (R 2) values for the learning and testing values in the thrust force of the equation are 0.997797 and 0.995739, respectively. Torque’s learning and testing accuracy values are 0.987247 and 0.937909, respectively. The obtained equations have a high accuracy rate.

Modelling of Truck Tire–Rim Slip on Sandy Loam Using Advanced Computational Techniques

Vehicles often experience low tire pressures and high torques in off-road operations, making tire–rim slip likely. Tire–rim slip is undesirable relative rotation between the tire and rim, which, in this study, is measured by the relative tire–rim slip rate. There is little research on the effect of different terrains on tire–rim slip despite its significance for off-road driving; therefore, this topic was explored through Finite Element Analysis (FEA) simulations. An upland sandy loam soil was modelled and calibrated using Smoothed-Particle Hydrodynamics (SPH), and then a Regional Haul Drive (RHD) truck tire was simulated driving over this terrain, with a drawbar load added to increase drive torque. To examine their effects, five parameters were changed: tire–rim friction coefficient, longitudinal wheel speed, drawbar load, vertical load, and inflation pressure. The simulations showed that increasing the tire–rim friction coefficient and the inflation pressure decreased the tire–rim slip while increasing the vertical and drawbar loads increased the tire–rim slip. Varying the longitudinal wheel speed had no significant effect. Tire–rim slip was more likely to occur on the soil because it happened at lower drawbar loads on the soil than on the hard surface. These research results increased knowledge of tire–rim slip mechanics and provided a foundation for exploring tire–rim slip on other terrains, such as clays or sands.

Model and Property Analysis for a Ball-Hinged Three-Degree-of-Freedom Piezoelectric Spherical Motor.

Multi-degree-of-freedom piezoelectric motors have the advantages of high torque and resolution, simple structure, and direct drive, which are widely used in robot wrist joints, deep-sea mechanisms, medical equipment, and space mechanisms. To solve the problems of high force/torque coupling degree and ball low stator and rotor bonding strength of the traditional traveling wave type three-degree-of-freedom piezoelectric spherical motor, a new structure of ball-hinged piezoelectric spherical motor is proposed. Through coordinate transformation and force analysis, the driven mathematical model of the spherical motor is given. The model shows that the three degrees of freedom of the motor are coupled with each other. According to the mathematical model of the spherical motor, the mechanical properties of the motor are analyzed by the computer simulation. The results show that the stalling torque coefficient kt has a linear relationship with the friction coefficient ε and the stator preload Fc, has a nonlinear relationship with the stator radius R and the rotor radius r, and increases with the increase of R and decreases with the increase of r. The no-load speed of motor ωn is not related to the friction coefficient ε and the stator preload Fc, and increases with the increase of R and decreases with the increase of r. The anisotropic characteristics of torque and speed of a spherical motor are further analyzed, which lays a theoretical foundation for the drive control of a spherical motor.

Augmented Finite Control Set MPC Design Technique for Wide Speed Range Control of Permanent Magnet Synchronous Motor Drives

The effective motion control task is highly influencing the final drive performance in wide-range motor drives applications such as electric vehicles (EVs), washing machines, compressors, elevators and lathe machines. Recently, permanent magnet synchronous motor (PMSM) drive has been widely employed in these applications to achieve desired performances such as high efficiency, high torque requirements with minimum size “occupancy”. The PMSM drive features combining with these modern drive applications are highly nonlinear and the desired operation requirements demand high-performance control schemes with fast system response and robustness features. Linear control schemes are usually implemented to drive the PMSM that entail trade-offs between drive performance and simplicity in control implementation. Therefore, this paper presents the nonlinear control technique based on augmented finite control set (AFCS) model predictive control (MPC) scheme (AFCS-MPC). The proposed AFCS-MPC scheme enhances the standard MPC design by augmenting the nonlinear characteristics of the PMSM drive to achieve wide speed range drive performance under both steady-state and dynamic operating conditions. Comparative performance studies have been conducted and presented to confirm the efficacy of the proposed scheme.

Experimental Study on The Performance Characteristics of 4 Stroke CI Engine using Biodiesel Blend from Coconut Oil

To address the challenges faced by the government in the realm of petroleum imports, a promising strategy was adopted in the utilization of biodegradable and renewable sources of biodiesel, such as coconut oil. This research employed two distinct methodologies: Transesterification for biodiesel synthesis and a comprehensive assessment of fuel properties. Subsequently, an experimental phase assessed biodiesel within an engine environment to analysis performance metrics. Results showed that B30 (30% coconut oil, 70% diesel oil) has density of 0.850 g/cm³, B50 (50% coconut oil) at 0.861 g/cm³, and B100 (Pure coconut oil) at 0.893 g/cm³. The values differed from regional standards. As per ASTM D6751, B30 has a viscosity of 2.31 cSt, B50 3.22 cSt, and B100 is 7.02 cSt. Engine performance revealed B50 with the highest torque at 11.787 Nm, while B0 (pure hydrocarbon diesel) has a thermal efficiency of 38%. B0’s lowest SFC (Specific Fuel Consumption) is 261.12 g/kWh at 2000 watts load and 1000 rpm. Biodiesel coconut oil provided comparable power and torque (0.3% difference from B0) but consumed more fuel (21.6 % higher usage than B0). Keywords: Biodiesel, Coconut oil, Engine performance, Fuel properties, Transesterification.

Spinal axial torque assessment after surgical correction in adolescent idiopathic scoliosis: a new approach to 3D barycentremetry and mass distribution based on biplanar radiographs.

Barycentremetry in adolescent idiopathic scoliosis (AIS) allows the distribution of masses and their loading of the spine to be studied. In particular, the axial torque on the spine has been studied in AIS, but not after surgical correction. Spinal axial torque was studied in AIS before and after surgery. All AIS (Lenke 1 and 3) who underwent posterior spinal fusion surgery at our center in 2019 were included retrospectively. AIS underwent frontal and sagittal biplanar radiographs in the free-standing position before surgery, 4months after surgery, and at the last follow-up. Their spine and external envelope were reconstructed with validated methods. Spinal axial torque at the apex and the upper and lower end vertebra was calculated. Finally, the preoperative and postoperative values were compared to a previously published reference corridor for asymptomatic subjects. Twenty-nine patients were included (54 ± 11° Cobb angle, 15 ± 2years old at surgery). The surgical procedure decreased the Cobb angle by 36° ± 11° and decreased the spinal axial torque at the upper end vertebra by 2.5N/m (95% CI = [1.9; 3]; p < 0.001), at the apex by 0.6 N/m (95% CI = [0.4; 1]; p = 0.004), at the lower end vertebra by 2N/m (95% CI = [1.5; 2.8]; p < 0.001). Compared to 95th percentile of torque, which was previously evaluated in asymptomatic subjects, more than 90% of patients had higher values at the upper and lower end vertebrae before surgery. Postoperatively, 62% of patients still had higher torque at the upper end vertebra than asymptomatic subjects, while only 38% patients showed abnormal values at the lower junction. Results of this study confirm that AIS patients show abnormally high spinal axial torque, especially at the end vertebrae, and that this parameter is normalized postoperatively for only a small number of patients.

A Numerical Analysis on the Performance and Optimization of the Savonius Wind Turbine for Agricultural Use

Given the state of the world nowadays, renewable energy is becoming more and more essential rendering wind turbine electricity quite important. Its shape and the fact that the Savonius vertical axis wind turbine runs at relatively low wind speeds with high torque values makes it suitable for practical uses such as that of an irrigation system in agriculture industry. This paper utilizes numerical research with Computational Fluid Dynamics (CFD) to investigate the performance of a vertical-axis wind turbine. The ANSYS CFD program was engaged to construct the simulations during the pre- and post-processing stages. Wind speed remained constant while the angular velocity was altered to enable analysis of the flow through the wind turbine. Because of its mechanical simplicity, the primary profile of a semicircle has remained a typical option for turbines that generate high torque based on drag force. The effects of using elliptical curves and the fluctuation in thickness along the profile chord were both examined in this study. Equivalently, an attempt to optimize the rotor's design was made. After the performance of a numerical simulation, a geometry consisting of simple circle arcs was developed, with a 10.9% improvement in the power coefficient, analogous to prior optimizations with more complicated geometries. The numerical results derived include the torque coefficient evolution throughout a full rotation as well as the distribution of vorticity magnitude at different rotor points.

Soft Artificial Muscle Based on Pre-Detwinned Shape Memory Alloy Spring Actuator Achieving High Passive Assistive Torque for Wearable Robot.

For designing the assistive wearable rehabilitation robots, it is challenging to design the robot as energy efficient because the actuators have to be capable of overcoming human loads such as gravity of the body and spastic torque continuously during the assistance. To address these challenges, we propose a novel design of soft artificial muscle that utilizes shape memory alloy (SMA) spring actuators with pre-detwinning process. The SMA spring was fabricated through a process called pre-detwinning, which enhances the linearity of the SMA spring in martensite phase and unpowered restoring force, which is called passive force. The fabricated SMA spring can contract >60%. Finally, the soft wearable robot that can assist not only the gravitational torque exerted on the elbow by passive force, but also the elbow movements with active force was designed with a soft artificial muscle. A soft artificial muscle consists of the bundles of pre-detwinned SMA springs integrated with the stretchable coolant vessel. The stiffness of the muscle was measured as 1125 N/m in martensite phase and 1732 N/m in austenite phase. In addition, the muscle showed great actuation frequency performances, the bandwidth of which was measured as 0.5 Hz. The proposed wearable mechanism can fully compensate the gravitational torque for all the angles in passive mode. In addition, the proposed mechanism can produce high torque up to 3.5 Nm and movements in active mode.

Prior Computation of the Stator Current Dynamic Response for Torque Ripple Reduction in AC Motor Drives

In electric vehicles, the performance of the electric motor drive system depends on the characteristics of the control scheme applied. This paper discusses the torque ripple in an induction motor drive scheme exclusively and also proposes a new scheme to minimize it. The major cause of the torque ripple in induction motor drive is the presence of a high stator torque component (q-axis current) ripple. In the proposed scheme, the inverter is switched with the optimal duty ratio for the minimum q-axis current ripple. This leads to a decrease in q-axis current error and eventually torque ripple reduction. The distortion of the stator current waveform is also limited and gives rise to lower total harmonic distortion (THD). The feasibility of this proposed duty ratio modulated (DRM) improved torque and flux control scheme is studied using the MATLAB/Simulink computation tool and validated through appropriate experimentation.