Torque Variations Research Articles

Experimental Investigation of the Effects of Gasoline-Methyl Ethyl Ketone Fuel Blends on Engine Performance and Exhaust Emissions

Gasoline engines have been widely used because of operating with stoichiometric ratio and lower exhaust emissions compared to compression ignition engines. However, thermal efficiency is less than diesel engines due to lower compression ratio. In the present study, the influences of methyl ethyl addition were researched on engine performance, CO, CO2 and HC emissions in a single cylinder spark ignition engine. For this purpose, the test engine was run at wide-open throttle, engine speeds of 2400, 2800, 3200, 3600, 4000 rpm and the variations of engine torque, effective power, specific fuel consumption (SFC), thermal efficiency, CO, CO2 and HC emissions were investigated. It has been observed that engine power and torque increase and SFC decreases as methyl ethyl ketone is added to gasoline. It was observed that the thermal efficiency at 2800 rpm increased by 6.47%, 13.81% and 19.51%, respectively, with MEK20, MEK30 and MEK40 test fuels compared to gasoline. As the methyl ethyl ketone ratio in the blended fuels increased, HC and CO emissions reduced compared to gasoline. As a result, it was seen that methyl ethyl ketone additive can be utilized easily in a spark ignition engine without making any modification.

The dynamic behaviour of ORC-based power units fed by exhaust gases of internal combustion engines in mobile applications

Exhaust gases Waste Heat Recovery (WHR) in Internal Combustion Engines (ICEs) performed through ORC-based Power Units (ORC-bPU) ensures a reduction of fuel consumption and consequently CO2 emissions. Nevertheless, high fluctuations of hot source push the ORC-bPU to work frequently in severe off-design conditions. Hence, a deep knowledge of the unit dynamic behaviour is fundamental to develop control and operating strategies allowing to achieve a successful recovery. Dynamic response assessment of ORC-bPUs has been treated in literature but making mainly reference to theoretical approaches or to variations of input variables without considering the matching to the engine and the necessary constraints which are present in a real mobile application. Moreover, Moving Boundary (MB) models are generally used as theoretical tools to support the dynamic analysis focusing the attention on Heat Recovery Vapor Generator (HRVG) which rules the plant dynamic response. In MB models, boundary conditions at the HRVG exit are mainly fixed by the expander and by the remaining circuit. To date, the attention was focused on the presence as expander of dynamic machines (turbine), deserving an evident lower attention to volumetric expanders nonetheless their higher suitability for low-medium scale ORC applications (few kWs). To fill these knowledge gaps, a novel approach is pursued in the present paper. The dynamic response of an ORC-bPU was experimentally observed for a step change of torque and revolution speed of an ICE directly connected to the recovery unit. The variation of engine operating conditions produced an unsteady variation of the temperature and flow rate of the exhaust gas feeding the unit. The dynamics of the engine and the connecting pipes is considered as well as all the typical constraints of a real situation. Results show HRVG and exhaust pipe ruling the dynamic behaviour of the unit, leading to long time constant and raising time of gas temperature of 150 s and 300 s respectively. These results show that the unit almost always works in transient conditions being engine torque and speed variations very fast. Nevertheless, thanks to the self-regulation capacity and the robustness of the scroll expander, the unit reacts in a satisfactory way. A further novelty of the present study concerns the integration of the widely used Moving Boundary (MB) approach with Permeability theory which considers the presence of a volumetric expander and all the ither downstream components, finding a match not available in literature between the HRVG and a volumetric expander and pump. The results of the new Permeability-Moving Boundary model (P-MB) was compared with those of a more comprehensive mathematical model. The comparisons show a comparable accuracy and a significantly lower computational time achieved with P-MB. Hence, P-MB could be implemented on board to set up control strategies enhancing the recovery tuned by a model-based approach.

Traction Properties of Aerospace Lubricant under Low-Temperature Micro-Oil Droplet Supply Conditions

Aerospace bearings need to withstand the low-temperature environment of space, which will cause changes in the internal lubrication state of the bearings. This article aims to assess the traction properties of aerospace lubricants under low-temperature micro-oil droplet (hereinafter referred to as ‘micro-oil’) supply conditions, and provide a lubrication theoretical basis for studying the motion characteristics of aerospace bearings in a low-temperature environment. An experimental study on the low-temperature micro-oil traction properties of high-speed bearing lubricants was conducted on a specially designed aerospace bearing lubricant traction characteristic tester. A modified Herschel–Bulkley model (modified H–B model) was presented based on test data analysis, and the fitting results were compared with the Tevaarwerk–Johnson model (T–J model). The findings demonstrated that the traction coefficient of this lubricant decreased at a higher load and entrainment velocity, and decreased with a decreasing inlet oil temperature from 0 °C to −50 °C. The modified H–B model accurately fitted the test data and was suitable for the engineering traction coefficient calculation of lubricants and high viscosities at low temperatures. This paper can provide fundamental information for analyzing aerospace bearing friction torque variation.

Trajectory tracking control of two-joint underwater manipulator in ocean-wave environment

In this study, a dynamic model of a two-joint manipulator used in underwater robots considering the influence of ocean waves was derived based on the Lagrange principle and Newton–Euler method. The Morison equation was employed to calculate the inertial force and water resistance of ocean waves acting on the manipulator. The ocean force terms in the new model vary with time, which makes trajectory tracking control more complicated than in models used in land and still-water environments. The ideal trajectory of the manipulator was tracked using proportional-derivative (PD) control and sliding mode control (SMC). The PD control proved weak in trajectory tracking, whereas the sliding mode control could quickly and accurately track the ideal trajectory. Three reaching laws were compared, and variable exponential reaching law 2 was the most suitable for trajectory tracking. To test the sliding mode control ability, an experiment was conducted in an ocean-wave environment with varying ocean wave heights, wave frequencies, and water depths. In addition, variations in input torque were observed. It was also found that the input torque required in an ocean-wave environment was higher than that required in land and still-water environments.

Electromechanical coupling characteristics analysis of vertical stirred mill based on ECS-MBD-DEM

This paper focuses on the start-up and steady-state operation stages of a vertical stirred mill, and the electromechanical coupling characteristics are thoroughly investigated based on the ECS-MBD-DEM coupling method. Firstly, according to the driving and working principles of the vertical stirred mill, the electrical control system (ECS) and multibody dynamics (MBD) model of the vertical stirred mill are separately established. Subsequently, a discrete element method (DEM) model is developed for the grinding media inside the mill. On this basis, the ECS-MBD-DEM coupling model of the vertical stirred mill is constructed, and its feasibility is validated through experiments. Then, the pitch, screw diameter, grinding media filling, and mill rotation speed of the helical agitator are considered as influential factors, with average value and coefficient of variation used as evaluation indicators for the level and fluctuation of changes. The load torque and current amplitude during the start-up and steady-state stages of the vertical stirred mill are analysed separately based on the ECS-MBD-DEM coupling method. The results indicate that the pitch, screw diameter, and grinding media filling have a significant effect on the average value of load torque. The screw diameter, grinding media filling, and mill rotation speed significantly influence the coefficient of variation of the load torque. The mill speed has a significant effect on the average value and coefficient of variation of the current amplitude. Finally, the cumulative volume velocity difference is proposed as an evaluation indicator for the grinding efficiency in the annular region, and the impact of influential factors on it is discussed, the results show that the grinding media filling and mill speed have a significant impact on the cumulative volume velocity difference.

Fuzzy Controller Implemented for Movement of a Tendon-Driven 3D Robotic Lumbar Spine Mechanism.

Notable efforts have been devoted to the development of biomechanical models of the spine, so the development of a motion system to control the spine becomes expressively relevant. This paper presents a fuzzy controller to manipulate the movement of a 3D robotic mechanism of the lumbar spine, which is driven by tendons. The controller was implemented in Matlab/Simulink R2023a software, MathWorks (Brazil), considering mathematical modeling based on the Lagrangian methodology for simulating the behavior of the lumbar spine dynamic movement. The fuzzy controller was implemented to perform movements of two joints of the 3D robotic mechanism, which consists of five vertebrae grouped into two sets, G1 and G2. The mechanism's movements are carried out by four servomotors which are driven by readings from two sensors. For control, the linguistic variables of position, velocity and acceleration were used as controller inputs and the torque variables were used for the controller output. The experimental tests were carried out by running the fuzzy controller directly on the 3D physical model (external to the simulation environment) to represent flexion and extension movements analogous to human movements.

Simulation-based uprighting of a capsized ship in wave-induced environments

The present study aimed to find the truth about the effect of ocean waves on the process of righting a capsized ship by employing common computational methods of marine salvage engineering. Mathematical models of ship stability and uprighting were developed to quantitatively evaluate the effects of wave encounter angle on the righting forces, bending moments and torques of the hull during the uprighting process. The results indicated that during the uprighting process, the maximum righting forces of the capsized ship were almost unchanged with a maximum difference of 1kN, when the ocean was calm or when the encounter angle of the waves varied. However, the righting force moment showed significant discrepancies under all conditions, with a maximum difference of 1177.5 kN m. When the wave encounter angle is at 0°, the shear force of some parts of the ship is 2–3 times that of the still water environment, and the shear force of some parts of the ship is 3–4 times that of the wave encounter angle at 300°. Remarkably, the bending moment varied by more than 200% at some particular locations under a particular wave encounter angle. Furthermore, the negative torque variation was relatively minor at a 300° wave encounter angle, and the uprighting process still needs relatively large righting forces.

A numerical study on the blade–vortex interaction of a two-dimensional Darrieus–Savonius combined vertical axis wind turbine

To investigate power losses of a Darrieus–Savonius combined vertical axis wind turbine (hybrid VAWT) associated with the interaction between blades and wake, it is crucial to understand the flow phenomena around the turbine. This study presents a two-dimensional numerical analysis of vortex dynamics for a hybrid VAWT. The integration of a Savonius rotor in the hybrid VAWT improves self-starting capability but introduces vortices that cause transient load fluctuations on the Darrieus blades. This study attempts to characterize the flow features around the hybrid VAWT and correlate them with the Darrieus blade force variation in one revolution. Results demonstrate the capability of numerical modeling in handling a wide range of operational conditions: the relevant position of Savonius and Darrieus blades (attachment angle γ=0°−90°) and Savonius' tip speed ratio λS (0.2–0.8, varied Savonius' rotational speed). The torque increase in the Darrieus blade in hybrid VAWT (compared to a single Darrieus rotor) due to the appearance of the vortex shedding from the advanced Savonius blade is independent of the attachment angle and tip speed ratio. Apart from start-up and power performances of the hybrid VAWT, the most rapid force fluctuation is identified when the Darrieus blade interacts with Savonius' wake at γ=0° and λS=0.8, which is considered undesirable. Furthermore, attachment angles of 60° and 90° exhibit better power coefficients compared to those of 0° and 30° for the hybrid VAWT. This study contributes to a comprehensive understanding of flow dynamics in hybrid VAWTs, revealing the correlation between torque variation and vortex development.

Load Torque Observer for BLDC Motors Based on a HOSM Differentiator

An observer is proposed for a trapezoidal brushless DC motor composed of a cascade connection of a reduced-order Luenberger observer and a high-order sliding mode (HOSM) differentiator. This configuration can estimate the angular velocity and reconstruct the load torque, key elements for the control of this type of motor, under the mild assumption that the variable load torque and its k-th time derivatives are bounded. The proposed observer was tested on an experimental test bench based on Texas Instruments (TI) High Voltage Digital Motor Control (HVMTR Kit) using a Delfino F28379D micro controller. The results show that the velocity and load torque can be properly estimated, despite the presence of noise in the current measurements.

Virtual Reference-Based Fuzzy Noncascade Speed Control for PMSM Systems With Unmatched Disturbances and Current Constraints

This paper aims to develop a non-cascade speed control approach for permanent magnet synchronous motor (PMSM) systems based on the Takagi–Sugeno (T–S) fuzzy model. In non-cascade control structures, the lack of firsthand current references imposes a tricky challenge in dealing with current constraints from the circuit and unmatched disturbances caused by load torques. To this end, a virtual reference-based fuzzy non-cascade speed control scheme is proposed for PMSM systems. First, unmatched load torques are estimated by a fuzzy disturbance observer. And then, a novel virtual reference planner is constructed to inject the estimated unmatched disturbance into the control channel as feedback compensation. This improves anti-disturbance performance, while keeping the current re-sponse within the feasible domain and reducing speed overshoot. Furthermore, the non-cascade speed regulation problem is con-verted into a system stabilization problem and addressed by the composite control strategy based on the non-parallel distributed compensation. Finally, closed-loop stability with reduced con-servatism is ensured through the fuzzy Lyapunov functions and improved slack variables. Simulations and experiments show that the proposed scheme achieves excellent speed response without overcurrent even under mismatched load torque variations.

Autodrillers, Rig-Control Systems, Driller Procedures Reduce BHA Failures

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 214997, “The Role of Autodrillers, Rig-Control Systems, and Driller Procedures in Reduction of Bottomhole Assembly Failures,” by Pablo E. Barajas, SPE, Paul Pastusek, SPE, and Aaron Lacey, ExxonMobil, et al. The paper has not been peer reviewed. _ Reducing bottomhole-assembly (BHA) failures has been this operator’s focus in US land intermediate and lateral sections to reduce cost per foot. BHA failures can be mitigated with better autodriller processes, improved rig-control-system technology, and drilling-mechanics-based procedures. The operator, rig contractor, and BHA service providers engaged in an intensive continuous improvement process for 18 months to help two rigs in Oklahoma reduce the number of BHAs used per well. The goal was to determine how to best tune the autodriller and standardize set-point practices. Introduction The operator has found that rig-control systems, particularly the autodriller, can be unstable in many drilling situations. The operator and contractor laid out the framework to measure autodriller dysfunction suspected to affect rate-of-penetration (ROP) and BHA integrity. The team engaged in a structured and intensive continuous improvement process with the following objectives: - Understand if end-user tuning and set-point practices from the contractor were being applied consistently at the rig floor level - Evaluate if the tuning practices were appropriate or effective in mitigating dysfunction in different formations - Increase subject-matter experts’ support and involvement in proactively identifying when rig-control systems were not behaving as designed to reduce impact on ROP and the BHA - Evaluate whether the operator’s drilling roadmaps and BHA safety-limit protections were being properly integrated into autodriller control loops - Use downhole sensors to understand how surface controls induced dysfunctions and confirm when they were mitigated - Propagate learnings across all rigs and crews in the basin to reduce the number of BHAs required to drill each well Observations Autodriller Dysfunction Identification. Standardizing the identification of dysfunction patterns to be avoided was a step based on physics of the system, bit-run performance and dulls (Fig. 1), directional tool damage, high-frequency (1,024 samples per second) downhole data, and high-frequency (six samples per second) surface data. Currently, the focus is to quickly identify and mitigate autodriller dysfunction by the rig teams, including the types of dysfunction described in this section. Stick/Slip. The operator developed a test to run the autodriller in different control loops to determine when stick/slip was initiated or intensified by the autodriller. Restarting drilling in ROP mode with the rig’s torsional dampening system active eliminated the autodriller as the source of stick/slip. It was determined that excessive weight on bit (WOB) used to pass the tool joint through the rotating head in the managed-pressure-drilling’s rotating control device (RCD), combined with low rotational speed, were key factors in initiating stick/slip. WOB Dysfunction. Any significant WOB variation can drive enough torque variation to drive stick/slip. This is particularly true if the WOB variation has a frequency close to the natural torsional frequency of the system.

Performa Motor Bakar Satu Silinder 4-Tak Dengan Ground Strap Kabel Koil Sistem Pengapian (Variasi Panjang Kawat)

The research aims to examine the relationship and comparison of motor performance when using a ground strap cable for the secondary circuit of the ignition system, as well as to determine the length of the ground strap wire which results in better engine performance. The ground strap is in the form of a coil of cable outside the spark plug cable, whose function is to catch stray frequencies. With this tool, the electric current to the spark plug is claimed to be more focused, and the flame automatically becomes more stable and optimal. The research variables used to answer the above objectives are: independent variable, ground strap wire length, dependent variable power, torque and specific fuel consumption for a single cylinder 4-stroke motorbike and control variables, working temperature of the Honda Blade 110 cc motorbike and room temperature. The results of the research show that the performance produced for the four coil cable treatments, namely without and with the use of ground with different lengths, is increasingly decreasing, while specific fuel consumption shows that the higher the motor rotation, the lower the KBBS produced. The longer the ground strap wire, the better the motorbike performance. Without the use of a ground strap, motorbike performance is still better, 1,891 hp/4000 rpm, 3,366 Nm/4000 rpm and 0.139 kg/h/hp/4,000 rpm higher than using a ground strap with a wire length of 28 cm, namely 1,722 hp; 3,066 Nm and 0.166 kg/h/hp at 4000 rpm. The conclusions obtained are as follows: maximum motor performance is best for spark plug cables without using a ground strap but is unstable with each increase in rotation, while for coil cables with a ground strap the maximum performance sequentially increases with variations in the length of the copper wire winding in the coil cable. Power and torque decreased by 11%, while fuel consumption increased by 13% compared to without the use of a ground strap.

Enhanced Output Tracking Control for Direct Current Electric Motor Systems Using Bio-Inspired Optimization

In this paper, an efficient output reference trajectory tracking control scheme for direct current electric motor systems based on bio-inspired optimization is proposed. The differential flatness structural property of the electric motor along with dynamic tracking error compensation is suitably exploited for the backstepping control design. Off-line optimal selection of control parameters, implementing bio-inspired ant colony and particle swarm optimization algorithms, is addressed by minimizing an objective function where the decision variables are the tracking error and control input effort. A novel adaptive version of the control approach based on B-spline artificial neural networks is provided as well. The introduced flat output feedback tracking control design approach can be further extended for other differentially flat dynamic systems. Considerably perturbed, diverse velocity and position reference trajectory tracking scenarios are developed for demonstrating the acceptable closed-loop system performance. The results prove the efficient and robust tracking of the position and velocity reference profiles planned for the operation of the controlled electric motor system under variable torque disturbances using bio-inspired optimization.

Incorporating the coupled effects of slot opening, armature reaction and saturation in the model of the airgap flux density distribution of permanent magnet synchronous machines

AbstractA new analytic model for calculating of the air‐gap flux density (AGFD) of surface‐mounted permanent magnet synchronous machines (SMPMSMs) is presented. This proposed model is capable to taking into account the effects of magnetic saturation, armature reaction and stator slots opening. Furthermore, the real form of air‐gap distribution and spatial distribution of flux density of the PM poles are considered. The armature reaction effect is modeled using phasor diagram analysis of the motor as a function of the load torque, the armature current amplitude, power factor and the inverse air gap length. Also, saturation phenomenon predicted using the new non‐linear proposed function in connection with the armature reaction effects and the properties of the lamination material. It is shown that the proposed model capable to predicting acceptably the air gap flux density waveform of the SMPMSMs at lagging and leading power factors and with the load torque variation. The presented analytical approach is verified by the two‐dimensional finite‐element analysis (FEA) results.

Department of Energy Motor and Drive Assessment Identifies Energy Savings for Power Drive Systems: A Paradigm Change

Petroleum and chemical refining, along with all other process industries, utilizes many electric motors to meet power demands. This article discusses results of an assessment survey of installed motors and drives performed by Lawrence Berkeley National Laboratory (LBNL) and funded by the U.S. Department of Energy (DOE) [1]. A key finding was that there are energy savings available with the addition of adjustable speed drives (ASDs). The National Electrical Manufacturers Association (NEMA) is collaborating with the Northwest Energy Efficiency Alliance (NEEA) and Cadeo Group to develop a prescriptive process to allow for rebates for power drive systems (PDSs) consisting of a premium efficiency electric motor and an ASD. Most efficiency standards, such as NEMA MG 1 [2] or International Electrotechnical Commission (IEC) 60034-30-1 [4], today focus on the efficiency of the components, with or without an ASD, rather than focusing on energy savings through optimized process management NEMA MG 10011 [3]. Organizations are now looking at the combined energy use of the PDS, especially on variable torque loads, such as pumps, fans, and compressors that are commonplace in process industries. This is a paradigm change from component efficiency to energy savings through a PDS system.

Use of a Novel Artificial Intelligence Tool for Evaluating Primary Stability and Immediate Loading Suitability of Dental Implants: An In Vitro Pilot Study.

To evaluate the correspondence between output from a new artificial intelligence tool (AIT) and clinician evaluation regarding the immediate loading suitability of dental implants based on insertion torque curves recorded during implant placement in an in vitro test. The secondary aim was to analyze peak insertion torque (PIT) and variable torque work (VTW) values of the implants. The study was performed with four different densities of artificial bone blocks of solid rigid polyurethane without a cortical layer. Five types of implants with different macrogeometries were used. A total of 140 implants (7 implants of each type in the four polyurethane blocks) were inserted. Immediately after implant placement, the insertion torque curves were classified by the operator as suitable (S) or nonsuitable (NS) for immediate loading. The same curves were then analyzed by the new AIT, which classified them as belonging to the 'YES' or 'NO' class. For each implant, PIT and VTW values were also recorded. The correspondence between clinician and AIT evaluation was 99.3%, with only one false negative reported by the algorithm analysis. The AIT was found to have a sensitivity of 98.95%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 97.8%. Mean PIT of the whole sample was 34.19 ± 19.43 Ncm, while mean VTW was 2,266.89 ± 1,993.73 Ncm. Statistically significant differences were found between implant systems in the whole sample and according to density of the polyurethane block. The AIT showed a high level of accuracy in the prediction of immediate loading suitability of dental implants based on the provided insertion torque curves. All the implants used in the in vitro test achieved good levels of primary stability, except when inserted in the least-dense polyurethane block. Clinical studies conducted with larger samples and more clinicians are necessary to confirm these results.

Optimal control of the electro-hydraulic actuator for variable pitch variable speed wind turbine: Performance enrichment

The wind energy generation system is complex because of varying wind speeds and its control systems to improve its ability of energy harvesting. This paper considers a hydraulic actuator-based variable-pitch angle control of a 1.5 MW wind turbine. The existing control systems of the pitch mechanism of the wind turbines are complex and bulky size. This study applied Genetic Algorithm based Proportional Integral Derivative Controller (GA-PID), Fractional Order Proportional Integral Derivative (FOPID), and Genetic Algorithm based Fractional Order Proportional Integral Derivative (GA-FOPID) controllers to adjust the pitch angle of the wind turbine blade. The performance of GA-FOPID, FOPID, and GA-PID controlled pitch angle is compared by considering different wind speeds. The GA-FOPID controller reduced the variation in mechanical power to 0.08% concerning the rated value and the variation in mechanical torque to 1.51% in comparison to the rated value. Therefore, the GA-FOPID controller shows better performance than the conventional PID.

Feedback between megathrust earthquake cycle and plate convergence

Over million years, convergence between the Nazca and South America tectonic plates results in Andean orogeny. Over decades/centuries, it fuels the earthquake cycle of the Andean megathrust. It is well recognised that, over the geologically-long term of million years, Andean orogeny feeds back onto plate convergence rates, generating temporal changes documented throughout the Neogene. In contrast, no feedback mechanism operated over the geologically-short term by the earthquake cycle is currently contemplated. In fact, it is commonly assumed that the rates of contemporary convergence, which are accurately measured via geodesy, remain steady during the megathrust earthquake cycle. Here we investigate whether the contemporary Nazca/South America plate motion varies over year-/decade-long periods in response to megathrust stress variations associated with the earthquake cycle. We focus on the decade preceding the three largest and most recent {varvec{M_w > 8}} earthquakes (2010 {varvec{M_w = 8.8}} Maule, 2014 {varvec{M_w = 8.1}} Iquique, 2015 {varvec{M_w = 8.3}} Illapel), and find slowdowns of both Nazca and South America whole-plate motions that exceed the impact of data uncertainty or noise. We show that the torque variations required upon Nazca and South America to generate the slowdowns are consistent with that arising from the buildup of interseismic stress preceding the earthquakes.

Study on the Pitch Angle Effect on the Power Coefficient and Blade Fatigue Load of a Vertical Axis Wind Turbine

For vertical axis wind turbines (VAWTs), the increase of the incoming wind speed higher than the rated value will make the tip speed ratio (TSR) lower and lower, resulting in the blade fatigue load becoming more and more severe and the power coefficient weakening gradually. This paper explores whether varying the pitch with the TSR decrease is necessary for improving the power coefficient and reducing the fatigue load. Specifically, the pitch angle effect on the power coefficient and fatigue load of a VAWT at different TSRs was studied by the computational fluid dynamics method. The results show that the optimal pitch angle in terms of the power coefficient varies with the TSR, which means that varying the pitch with the TSR decrease can improve the power coefficient. Meanwhile, the principle to guide the pitch variation is to avoid flow separation in the downwind zone and minimize the angles of attack (AoAs) in the upwind zone. At the lowest TSR of 1.7 in the present work, varying the pitch from the optimal one in terms of the power coefficient reduced the blade normal force amplitude significantly, which is mainly attributed to avoiding the vortex–blade encounter and minimizing the AoAs in the downwind zone. The vortex–blade encounter at the lowest TSR is an important phenomenon related to the variation of the blade torque and blade normal force and will weaken and disappear with the pitch angle increase.

Research on coupling control of multiple permanent magnet synchronous motors based on NAISMC and SMDO.

The synchronous control system of multi-permanent magnet motor has the characteristics of many parameter variables and mutual coupling. The use of sliding mode control to optimize the parameters in the multi-permanent magnet motor system not only ensures the stability of the system operation, but also improves the control accuracy of the system, which is of great importance in practical applications. Based on this background, the study combines the new adaptive integral sliding mode control (NAISMC) with the improved sliding-mode disturbance observer (SMDO) and uses it for the multi-permanent magnet synchronous motor (MPMSM). In NAISMC, the controller updates and adjusts the parameters of the controller using an adaptive algorithm according to the state of the system and the error signals, which further improves the stability and robustness of the system. SMDO utilizes the principle of the sliding-mode observer to estimate the disturbance of the system, and eliminates the effect of the disturbance on the system by introducing a compensation term. The sliding mode observer calculates the disturbance estimate by comparing the difference between the actual and the estimated outputs. The disturbance estimate is finally used to generate the corresponding compensation signal to eliminate or minimize the effect of the disturbance on the system. NAISMC is combined with SMDO and used in the deviation coupling control of MPMSM. The study established a simulation experiment environment in MATLAB, set the simulation time to 0.4s, and the rated speed of the motor to 1000r/min. The improved sliding mode control scheme is tested, and the results show that the motor output speed, tracking error and electromagnetic torque variation under the improved sliding mode control scheme are smaller than those under the traditional sliding mode control scheme. Under the same simulation conditions, the multi-motor speed synchronization error under the improved sliding mode control scheme is around 0r/min, and its error value is close to 0, so the control effect is higher. In conclusion, the optimization scheme proposed in this study can effectively improve the stability and control accuracy of the multi-motor system.