Speed Mode Research Articles

Sensorless direct torque control based on nonlinear integral sliding mode controllers for an induction motor drive: Experimental verification

In this article, a novel sliding mode adaptation mechanism of a model reference adaptive system speed estimator and a modified sliding mode speed controller are proposed to replace the proportional-integral controller used in the adaptation mechanism of the model reference adaptive system and the proportional-integral speed controller, respectively. The suggested control strategy is designed by sensorless direct torque control with space vector modulation based on a sliding mode speed controller and a model reference adaptive system sliding mode speed estimator. The contribution of this work is the development of one control law based on a modified nonlinear component to overcome the first-order sliding mode control limitations, such as the chattering phenomenon. The performance of the suggested controller-based direct torque control with space vector modulation is verified by digital simulation with different operation conditions, like the abrupt variations in the load torque and the reference speed, using the MATLAB/SIMULINK environment. In fact, such simulation results are experimentally checked utilizing a dSPACE-1104.

Shear Stress and Hemolysis Analysis of Blood Pump under Constant and Pulsation Speed Based on a Multiscale Coupling Model

Current researches show that the constant speed mode adopted by the existing commercial blood pump may cause damage to the body. The way to solve this problem is to produce pulsating flow by changing the speed of the blood pump’s impeller. But at present, the flow field of the blood pump is not clear, when it changes speed, and the coupling between blood pump and body has not been considered in the simulation of the flow field. A multiscale coupling model combining hemodynamics (0D) and Computational Fluid Dynamics (3D) was established in this paper to solve the problem, and a speed change curve consistent with the ventricular motion was selected. The hemodynamics, shear stress, and hemolysis changes of 6000 rpm at different amplitude (2000, 3000, and 4000 rpm) were simulated, analyzed, and compared with the constant speed (7000 rpm). The results show that the pressure difference obtained by simulation is consistent with the experimental results, and the flow generated by the natural heart still flows through the blood pump, thus changing the working point of the blood pump. When the blood pump works at the changing speed, it could produce more pulsation, and the shear stress and hemolysis in the blood pump increase with the rising of speed and flow. But according to the hemolysis score of a single cardiac cycle, the hemolysis value of the changing speed model at an amplitude of 4000 rpm is only 11.71% higher than that of constant speed at 7000 rpm.

OPTIMAL CONTROL OF A STEP-BY-STEP TRANSMISSION OF VEHICLES

The actual problem of optimal selection of means of transport (MT) gear ratios, equipped with internal combustion engines (ICE) with a step-by-step gearbox according to the criterion of minimum fuel consumption is considered in the article. An analysis of the scientific and technical literature has showed the absence of simple and sufficiently justified algorithms for controlling the vehicle’s power plant, which is a system that consists of an ICE and an adjustable transmission. The aim of this work is the theoretical justification of the law of gear ratios shifting of a step-by-step transmission, ensuring maximum fuel efficiency for any power and speed mode of MT. The proposed method is based on set of linear transformations that connect the engine moment and engine speed with a traction force and a speed of MT. The set of gear ratios correspond to the set of one-extremal functions of specific fuel consumptions. The set of points of equal levels lines corresponding to two neighboring values of the gear ratios of the transmission forms a gear shift line. An appropriate algorithm for switching gear ratios is proposed, which ensures the most efficient operation of a power plant of MT in conditions of variable power and speed modes.

Gravitational waves in modified Gauss–Bonnet gravity

We study the gravitational waves (GWs) in modified Gauss–Bonnet gravity. Applying the metric perturbation around a cosmological background, we obtain explicit expressions for the wave equations. It is shown that the speed of the traceless mode is equal to the speed of light. An additional massive scalar mode appears in the propagation of the GWs. To find phenomena beyond the general relativity, the scalar mode mass is calculated as a function of the background curvature in some typical models.

Problem of Safely Tracking an Object Avoiding Observation in $${{\mathbb{R}}^{2}}$$

For the problem of an autonomous object moving under hostile observation, the observer’s positions are characterized in which the object following any route can choose a speed mode that allows observation evasion, and positions guaranteeing that the observer is able to track the object on the initial part of the trajectory and only on it are described.

Design of Wear-Resistant UHMWPE-Based Composites Loaded with Wollastonite Microfibers Treated with Various Silane Coupling Agents

The tribomechanical properties of the wear-resistant ultrahigh molecular weight polyethylene (UHMWPE)-based composites loaded with wollastonite microfibres silanized with various coupling agents (“KH-550”, “Penta-1006”, and “OTS”) were investigated. It was demonstrated that the mechanical properties of UHMWPE-based composites filled with various amounts of wollastonite (7–23 wt. %) increased by 1.3 times (yield strength) and by 1.8 times (elastic modulus), while the wollastonite silanization further improved yield strength by 9% in some cases. It was demonstrated that the composite loaded with 23 wt. % wollastonite silanized with the “KH-550” coupling agent possessed the maximum wear resistance under “moderate” conditions of tribological loading. Under “severe” conditions, the composites containing 23 wt. % wollastonite silanized with the less efficient “OTS” and “Penta-1006” agents showed the greatest wear resistance during dry sliding friction. Wear resistance significantly depended on filler weight fraction and the load–speed mode of the tribological tests. Based on the obtained experimental data on the mechanical (including impact toughness) and tribological properties of the UHMWPE-based composites loaded with wollastonite, the optimal compositions (the filler content and the type of the coupling agent) for two load–speed modes were designed using the developed computer algorithm. The composites provided the predefined high tribomechanical properties for operation in the metal-polymer friction units compared to neat polymer.

Numerical simulation of wave mode transition in rotating detonation engine with OpenFOAM

Two-dimensional numerical simulations of rotating detonation engine are carried out with detailed chemical kinetic mechanism using detoFoam, a custom solver based on OpenFOAM 7. The results show the transition process from single wave with counter-rotating components mode to two counter-rotating waves at equal speed mode. Counter-rotating components are weak waves propagating in the opposite direction against the primary detonation wave. The mechanism behind the transition process is that the counter-rotating components gain energy from collisions with detonation waves and the fresh gas region. When counter-rotating components gain more energy than they lose in one cycle, they become stronger until the peak pressure reaches a threshold value. When a counter-rotating component is strong enough, its collision with fresh gas region will ignite a detonation wave, breaking the steady state. The new detonation wave propagates in the opposite direction against the original detonation wave, leading to the formation of two counter-rotating detonation waves.

Dehumidification performance of a variable speed heat pump and a single speed heat pump with and without dehumidification capabilities in a warm and humid climate

Conventional air conditioning systems in houses respond to thermal loads by means of controlling dry-bulb temperature through the thermostat. As part of the process to control temperature, dehumidification is also provided. However, as houses are becoming more efficient, supplemental dehumidification is often necessary for homes located in hot and humid climates to control relative humidity intentionally. This study compared the dehumidification performance of a residential air conditioning system working in three operations modes to emulate three different systems: a system with a variable speed mode, a single-speed system with an enhanced dehumidification mode, and a single-speed system operating in a traditional or normal cooling mode. With operation mode changes achieved through software, this study constituted a novelty in the topic of humidity control by using a single machine, with the same exact physical set-up to directly compare the dehumidification performance of three types of systems.Two types of days were of interest in the study, hot and humid days (summer season) and mild and humid days (Fall shoulder season). After assessment of the dehumidification performance, the variable speed mode was able to maintain relative humidity between 50% to 52% on summer days. In the single-speed with enhanced dehumidification, a slightly less effective humidity control was achieved on summer days with the mode keeping the relative humidity between 53% to 55%. In the normal cooling mode, which resembles a conventional system, the humidity levels were controlled between 55% to 60%. In the shoulder season, the variable speed and enhanced dehumidification modes maintained the relative humidity between 55% to 58% and 53% to 56% respectively. In the shoulder season, the normal cooling mode kept the indoor relative humidity near or above 60%. In terms of dehumidification efficiency expressed as a function of the amount of water condensate per unit of energy, the variable speed was determined to be more efficient than the other modes.

Results of Experimental Studies of the Seed Drill for Row Sowing SZD­4.0

Sowing units are considered to be the most complex agricultural machines, as they perform many operations - both sequentially and simultaneously. At the same time, agricultural producers are interested in the high-quality operation of the units. For the high-quality execution of technological operations and the improvement of energy indicators, seeders it is important to know and improve their design. ( Research purpose ) To determine the main agrotechnical and energy indicators of the seed drill for row sowing of SZD-4.0. ( Materials and methods ) Experimental studies of the SZD-4.0 seed drill were carried out on winter wheat sowing at a soil moisture content of 8.4-29.7 percent in a layer of 5-10 centimeters, a soil hardness of 0.8-2.0 megapascals, the depth of a loosened layer fractions of 0-10 centimeters amounted to 48.0-53.2 percent. Energy assessment was carried out at three speed modes in an aggregate with an MTZ-80 tractor equipped with a dynamometer and a measuring recording system. ( Results and discussion ) The main agrotechnical indicators of the seeder were revealed: the average depth of seed placement at the maximum, minimum and optimal depth of the coulters, the quantitative proportion of seeds planted at a specified depth, the height of the ridges after the passage of the unit, the number of seedlings and relative field germination. The authors studied the main energy indicators: the traction resistance of the seeder, the power consumption of the unit, the power spent on overcoming the traction resistance of the machine, the specific energy consumption of the unit, the specific fuel consumption during the main operation, the specific traction resistance. ( Conclusions ) It was confirmed that when the speed of the unit was 9.5-13.5 kilometers per hour, the working bodies of the seeder provided the depth of seed placement, the actual seeding rate, and the quantitative proportion of seeds planted in the layer corresponding to agricultural requirements. They determined the optimal mode of operation: at a speed of 12.04 kilometers per hour, with a coulter depth of 54.6 millimeters and when loading the engine of an energy facility by 76 percent.

Nested High Order Sliding Mode Controller with Back-EMF Sliding Mode Observer for a Brushless Direct Current Motor

This work presents a nested super-twisting second-order sliding mode speed controller for a brushless direct current motor with a high order sliding mode observer used for back electromotive force (back-EMF) estimation. Due to the trapezoidal nature of the back-EMF, a modified Park transformation is used in order to achieve proper field orientation. Such transformation requires information from the back-EMF that is not accessible. A second-order sliding mode observer is used to estimate the back electromotive forces needed in the modified transformation. Sliding mode control is known to be robust to matched uncertain disturbances and parametric variations but it is prone to unmatched perturbations that affect the performance of the system. A nested scheme is used to improve the response of the controller in presence of unmatched disturbances. Simulations performed under similar conditions to real-time experimentation show a good regulation of the rotor speed in terms of transient and steady-state responses along with a reduced torque ripple.

Impact of n-butanol-gasoline-hydrogen blends on combustion reactivity, performance and tailpipe emissions using TGDI engine parameters variation

Butanol and hydrogen both have unique thermodynamic properties and their combustion reactivity might be significant to energy sustainability. This work examined the effects of n-butanol-hydrogen-gasoline blends on turbocharged gasoline direct injection (TGDI) engine performance, combustion and gaseous emissions at different spark timing (ST), brake mean effective pressure (BMEP) and loads. Experiments are carried out at city transport speed mode under stoichiometric with Air-fuel mixture of 1.0. Results indicate that the brake specific fuel consumption (BSFC) of all blend fractions gradually decreased by 3.79% averagely, which improve the 50% combustion rate and lessen the ignition delay period (IDp) with the increase in rate of heat release (HRR), in-cylinder pressure and injection timing. Moreover, the brake thermal efficiency (BTE) constantly increased as the additives energy ratio increases at all testing modes. With increase in fuel additives, the optimum combustion pressure and HRR rise, and their ignitions come earlier at all modes due to advanced combustion which shortened the IDp as the operating mode was adjusted, and hence, exhibit high maximum pressure rise (MPR) and faster burning speed in the early combustion. When the coefficient of variation in IMEP (COVIMEP) is <5%, both ST and valve are basically suitable, unaffected by ignition timing and moderate SFC and NOx emissions to low condition. Retarding the ignition timing contributes to lower NOx in most cases and HC at 8° CA, and the CO increases by 3.24% on average with an increase in BMEP and load. Finally, effective output work was obtained, as less heat released passing through the cylinder wall is reduced with constant volume of combustion reactivity.

Physical human–robot interaction force control method based on adaptive variable impedance

This study presents a method for extracting the actual interaction force from a force sensor signal by measuring the gravity of the end-effector. The variable impedance control problem of commercial industrial robots is studied, to investigate the uncertain contact impedance characteristics between the human palm and a robot end-effector in the physical human-robot interaction process. A speed-based variable impedance adaptive interaction control method is proposed. The damping parameters of the admittance controller are adaptively adjusted according to the interactive force tracking error. The desired speed of the robot is also given, which is tracked in the Cartesian space speed mode of a Stäubli TX-90 robot to achieve interactive force control. An experimental comparison is made between the control strategies of the constant impedance and adaptive variable impedance. The experimental results show that the proposed method is effective.

Direct torque control of permanent magnet synchronous motor for electric vehicles

Permanent magnet synchronous motors (PMSM) are highly preferred in electric vehicles due to their high efficiency, good torque-speed characteristics, simple structure and long life. In this paper, the simulation study of direct torque controlled PMSM for electric vehicles was performed in MATLAB by direct torque control (DTC) method using different speed control and speed estimation methods, because output parameters of DTC method such as torque and current, have high ripple, and this ripple should be reduced for electric vehicle. Due to the simple structure of the DTC and its low dependence on the system parameters, it is widely used in alternative current motors. When DTC is used in PMSM drive, it is known that although it has fast dynamic response when it is compared to other vector control methods, the ripple in the torque and flux increases. In this study, direct torque controlled PMSM is tried to be minimized by using different speed control methods and speed estimation methods. For this purpose, proportional-integral (PI), fuzzy logic and sliding mode speed controller are used as speed controllers and their performances are compared. In addition, speed sensor less direct torque control of PMSM was performed by using sliding mode observer and model reference adaptive system (MRAS) observer. As a result of the simulation studies, it was found that sliding mode speed control method provides less ripples in the torque, better speed control and less energy consumption. Furthermore, as a speed observer, the sliding observer gives better results in speed estimation and provides less energy consumption.

Sliding mode approach applied to sensorless direct torque control of cage asynchronous motor via multi-level inverter

To improve the robustness and performance of the dynamic response of a cage asynchronous motor, a direct torque control (DTC) based on sliding mode control (SMC) is adopted to replace traditional proportional-integral (PI) and hysteresis comparators. The combination of the proposed strategy with sinusoidal pulse width modulation (SPWM) applied to a three-level neutral point clamped (NPC) inverter brings many advantages such as a reduction in harmonics, and precise and rapid tracking of the references. Simulations are performed for a three-level inverter with SM-DTC, a two-level inverter with SM-DTC and the three-level inverter with PI-DTC-SPWM. The results show that the SM-DTC method achieves better performance in terms of reference tracking, while adoption of the three-level inverter topology can effectively reduce the ripples. Applying the SM-DTC to the three-level inverter presents the best solution for achieving efficient and robust control. In addition, the use of a sliding mode speed estimator eliminates the mechanical sensor and this increases the reliability of the system.

The Design and Implementation of a Sensorless Power Tool Based on a Microcontroller

Power tools are basic working tools used for production and manufacturing in the machinery and mechanical industries. The motor drive plays an important role in power tool applications. The performance of the motor drive will then directly or indirectly affect the quality and precision of the processing metal components. Most of the traditional motor drive control of a brushless direct current (BLDC) motor employs the Hall-effect position sensors to detect the rotor position. However, the installing sensors are prone to degrading the performance due to variations in temperature and the harsh environment. This disadvantage can be overcome with sensorless solutions. Among these sensorless solutions, the zero-crossing point detection of the back electromotive force (BEMF) is popular. Nevertheless, for the 180-degree conduction mode, it is impossible to directly detect the BEMF because of the three terminals of the motor which are conducted at any time for an electrical cycle. Therefore, a novel sensorless circuit approach based on the terminal line to line voltage is proposed in this paper. Moreover, an improved circuit scheme with a Schmitt trigger for sensing the BEMF is also proposed and implemented to obtain the precisely resembling Hall-effect signals. Finally, a prototype of a sensorless BLDC motor drive with a 180-degree conduction mode speed control for power tools is designed and implemented in this paper. The experimental results show that the proposed circuit works properly and validates the feasibility and fidelity of the motor drive system.

THE STABILIZATION ACCURACY OF THE PHASE POSITION OF THE WORKING BODY OF THE ROBOTICS COMPLEX

To stabilize the phase position of the working body of the robotics complex a single-circuit precision electric drive system was developed based on the principle of phase-locked loop. The direct-driven electric drive is made on the basis of brushless direct current motor, which is switched to synchronous mode with minimal discrepancy between the phases of the reference signals and the pulse speed sensor. The phase error signal is fed to the input of the PID controller, which controls the pulse width modulation of the impulses controlling the operation of the power transistors of the autonomous voltage inverter. In a static mode, the control system of the autonomous voltage inverter implements a sinusoidal law of the pulse width modulation of the output pulses. The PID controller and the control system of the autonomous voltage inverter are programmatically implemented on the basis of the controller.&#x0D; In the process of analysing of the stabilization accuracy, the synchronous motor is represented by a second-order linear link, which establishes a relation between the phase deviations of the motor rotor and the stator magnetic field. The autonomous voltage inverter is represented by a zero-order hold whose coefficient of amplification on amplitude is found by the results of the approximation of its output voltage using the Walsh-Fourier series.&#x0D; The analysis of the phase stabilization process is performed on the basis of the state variables method taking into account the perturbations at the moment of load using the program which implements the recurrent procedure.&#x0D; The settings of the PID controller are determined by the variation results when the moment of load changes. Their initial values ​​are determined as a result of optimizing the system in terms of operation speed considering the condition of finite duration processes. It is assumed that there is no moment of load perturbation.&#x0D; The procedure for setting the PID controller parameters to the optimal operation speed mode can also be performed on the basis of neural networks.&#x0D; As a result of the calculations, it was found that with an increase of the load moment by 5%, the maximum deviation of the rotor phase was 0.22 us and 0.03 us of minimum deviation respectively.

Correlation between Mechanical Properties and Processing Conditions in Rubber-Toughened Wood Polymer Composites.

The use of wood fibers is a deeply investigated topic in current scientific research and one of their most common applications is as filler for thermoplastic polymers. The resulting material is a biocomposite, known as a Wood Polymer Composite (WPC). For increasing the sustainability and reducing the cost, it is convenient to increase the wood fiber content as much as possible, so that the polymeric fraction within the composite is thereby reduced. On the other hand, this is often thwarted by a sharp decrease in toughness and processability—a disadvantage that could be overcome by compounding the material with a toughening agent. This work deals with the mechanical properties in tension and impact of polypropylene filled with 50 wt.% wood flour, toughened with different amounts (0%, 10%, and 20%) of a polypropylene-based thermoplastic vulcanizate (TPV). Such properties are also investigated as a function of extrusion processing variables, such as the feeding mode (i.e., starve vs. flood feeding) and screw speed. It is found that the mechanical properties do depend on the processing conditions: the best properties are obtained either in starve feeding conditions, or in flood feeding conditions, but at a low screw speed. The toughening effect of TPV is significant when its content reaches 20 wt.%. For this percentage, the processing conditions are less relevant in governing the final properties of the composites in terms of the stiffness and strength.

Optimal Speed Plan for the Overtaking of Autonomous Vehicles on Two-Lane Highways

In passing maneuvers on two-lane highways, assessing the needed distance and the potential power reserve to ensure the required speed mode of the passing vehicle is a critical task of speed planning. This task must meet several mutually exclusive conditions that lead to successful maneuvers. This paper addresses three main aspects. First, the issues associated with a rational distribution of the speed of the passing vehicle for overtaking a long commercial vehicle on two-lane highways are discussed. The factors that affect the maneuver effectiveness are analyzed, considering the safety and cost. Second, a heuristic algorithm is proposed based on the rationale for choosing the necessary space and time for overtaking. The initial prediction’s sensitivity to fluctuations of the current measurements of the position and speed of the overtaking participants is examined. Third, an optimization technique for the passing vehicle speed distribution during the overtaking time using the finite element method is presented. Adaptive model predictive control is applied for tracking the references being generated. The presented model is illustrated using a simulation.

Experimental analysis of the thermal unbalance effect of a flexible rotor supported by a flexure pivot tilting pad bearing

The Morton effect is a thermally induced increase of synchronous vibrations amplitudes of rotors. The shearing of the fluid film in a journal bearing produces an asymmetric heating of the rotor which causes its thermal bending and increases the unbalance. The vector of synchronous vibrations describes a spiral with slowly increasing amplitude and phase change. The thermal bending is also enlightened by a hysteresis effect of the synchronous vibrations during start-up and coast-down. The purpose of this study is to highlight experimentally the signature of Morton effect in a flexible rotor supported by a flexure pivot tilting pad journal bearing. A dedicated test rig has been built. It consists of a flexible rotor guided at one end by a ball bearing and at the other end by a flexure pivot tilting pad bearing. The tests consist of controlled start-ups to a speed close to the critical speed of the first rotor flexible mode, followed by controlled coast-downs. They show a hysteresis of the amplitudes and phases of the synchronous vibrations. Other tests performed at constant speeds show amplitude and phase variations corresponding to spiral vibrations. The results are explained by the non-uniform distribution of the rotor temperature.

Synchronization and stability control of dual-motor intelligent steer-by-wire vehicle

In order to improve the safety of steer-by-wire (SBW) system, a dual-motor SBW system is proposed to enhance the fault tolerance and reliability of the system. However, the dual-motor SBW vehicle often loses its stability due to the external interference, and the asynchronous response between the dual-motor will further deteriorate the stability of the vehicle. Aiming at the existing problems, this paper proposes a hierarchical control strategy, in which the upper layer controls the vehicle stability and the lower layer controls the synchronization of the dual-motor. Firstly, the models of dual-motor SBW system and the vehicle are established. Secondly, considering the interference of lateral wind, sensor noise and the limitation of control output, a yaw rate controller is designed in the upper layer based on the mixed H2/H∞ robust control theory to improve the stability and tracking performance of the vehicle. Thirdly, a sliding mode speed synchronization control strategy is proposed in the lower layer based on the cross-coupling control structure and the sliding mode control algorithm to enhance the synchronization performance between the dual-motor. Finally, the simulation is carried out by using Carsim/Simulink and the hardware-in-the-loop experiment is conducted based on the dual-motor SBW experimental station. The simulation and experimental results verify the effectiveness of the control strategy proposed in this paper.