Electric Motor Torque Research Articles

Efficient Energy Conversion in Electrically Assisted Bicycles Using a Switched Reluctance Machine Under Torque Control

The prospect of physical exertion commonly acts as a deterrent to the adoption of cycling for everyday transport. A battery powered assistance torque electric motor could alleviate such physical exertion by reducing the effort required by the cyclist. This study investigates the potential effectiveness, efficiency, and energy saving of electrically-assisted cycling when assistance torque of a switched reluctance motor is designed to vary in accord to the cyclist instantaneous torque at the pedal cranks. Specifically, the modulated motor assistance torque is delivered at the least efficient human input torque points on the cycle. For a representative short distance cycling schedule modulating the instantaneous torque of the on-board electric motor causes the electric energy expenditure to not exceed that of the assisted cycling mode of an identical constant-torque motor. Furthermore, for the same speed profile cycling journey with added road gradient and head wind resistance, the energy expenditure of the modulated torque motor is equal to the constant torque motor. These findings indicate significant improvements in the cycling experience.

Formation mechanisms of maximal loads on cutters and cutting heads of coal mining machines

Purpose. To determine an influence exerted by the cutting mode and by geometry of cutters on the impact loads in various scenarios of cuttersolid inclusion interaction. Methodology. Mathematical simulation, statistical analysis Findings. Fracture of coal seams of a complex structure which contain solid discontinuities (solid inclusions and hard dirt bands) is associated with generation of impact loads on cutters and cutting heads of mining machines which cause a decrease in the productivity of the coal extraction process and premature failure of their components and elements. This impairs efficiency of coal cutting and causes premature failure of different components and parts. It is found that when a cutter cuts an inclusion or touches it, the size of the inclusion has no influence on the value of the peak load. On the contrary, in case of tear-out of an inclusion, the peak cutting force value essentially depends on the size and shape of the inclusion, as well as on the brittleness and plasticity of coal as these properties govern coal-inclusion cohesion. It is found that out of all modes of cutter-solid inclusion interaction, the highest loads arise in the mode of central cutting of inclusions. The mechanisms and behavior of occurrence of loads in short-term cutting of large (unbroken) solid inclusions by a group of cutters are discussed. The maximal loads on groups of cutters on cutting heads can also arise in gradual stalling when the average loading level approaches the tractive effort torque of electric motor when a group of cutters cuts many solid inclusions simultaneously, or in undermining of roof rocks, or in cutting hard dirt bands. Originality. The probabilities of solid inclusion cutting by a cutter are determined for different outputs of a cutting head, and the action times of the maximal peak load in cutting a coal strip 100 m long are assessed. The relations are proposed to calculate the levels and action times of maximal loads on a group of cutters in cutting solid inclusions, as well as the coefficients of variation in the loads and the loading inequality of a cutting head. Practical value. The results obtained by the authors should be taken as a basis in determination of the maximal instantaneous torque in the cutting head transmission to be used later on in calculation of the long-term strength of the transmission components.

A Moment-of-Inertia-Driven Engine Start-Up Method Based on Adaptive Model Predictive Control for Hybrid Electric Vehicles With Drivability Optimization

During the deceleration phase of a hybrid electric vehicle (HEV), a moment-of-inertia-driven (MoI-driven) engine start-up process can provide a potential economic benefit because it reduces the energy consumption of the starting device. During this start-up process, it is important to maintain drivability by enabling a quick start-up, low driveline vibration, and fast response to torque demand. The wheel rolling distance control should also be considered. This paper proposes electrical motor (EM) participation in an MoI-driven engine start-up process and studies an adaptive model-based predictive optimization method for the drivability control of P2 parallel hybrid vehicles. Based on a new triple mass-spring-system model, an adaptive model predictive controller (MPC) is designed with EM torque set points, clutch friction torque set points, and engine torque set points as manipulated inputs and engine speed, torsion speed, and wheel rolling distance as the measured outputs. A predicted torque demand is introduced to enhance the torque response performance. By considering the constraints of power source components, an optimization algorithm is developed. A simulation is conducted to verify the control strategy on the HEV powertrain and on vehicle dynamics models. The results show that under the same level of start-up, the torsion speed can be reduced by up to 50% with an improved wheel rolling distance and low torque demand error during a certain deceleration.

Performance comparison of electric-vehicle drivetrain architectures from a vehicle dynamics perspective

Recent electric vehicle studies in literature utilize electric motors within an anti-lock braking system, traction-control system, and/or vehicle-stability controller scheme. Electric motors are used as hub motors, on-board motors, or axle motors prior to the differential. This has led to the need for comparing these different drivetrain architectures with each other from a vehicle dynamics standpoint. With this background in place, using MATLAB simulations, these three drivetrain architectures are compared with each other in this study. In anti-lock braking system and vehicle-stability controller simulations, different control approaches are utilized to blend the electric motor torque with hydraulic brake torque; motor ABS, torque decomposition, and optimal slip-tracking control strategies. The results for the anti-lock braking system simulations can be summarized as follows: (1) Motor ABS strategy improves the stopping distance compared to the standard anti-lock braking system. (2) In case the motors are not solely capable of providing the required braking torque, torque decomposition strategy becomes a good solution. (3) Optimal slip-tracking control strategy improves the stopping distance remarkably compared to the standard anti-lock braking system, motor anti-lock braking system, and torque decomposition strategies for all architectures. The vehicle-stability controller simulation results can be summarized as follows: (1) higher affective wheel inertia of the on-board and hub motor architecture dictates a higher need of wheel torque in order to generate the tire force required for the desired yaw rate tracking. A higher level of torque causes a higher level of tire slip. (2) Optimal slip-tracking control strategy reduces the tire slip trends drastically and distributes the traction/braking action to each tire with the control-allocation algorithm specifying the reference slip values. This reduces reference tire slip-tracking error and reduces vehicle sideslip angle. (3) Tire slip trends are lower with the hub motor architecture, compared to the other architectures, due to more precise slip control.

Transparency of a Geographically Distributed Test Platform for Fuel Cell Electric Vehicle Powertrain Systems Based on X-in-the-Loop Approach

X-in-the-loop is a new vehicle development and validation method for increasingly complex vehicle systems, which integrates the driver and the environment. In view of recent developments in fuel cell electric vehicle powertrain systems, Tongji University and Karlsruhe Institute of Technology have jointly developed a set of distributed test platforms based on the X-in-the-loop approach. This platform contains models and test equipment for a fuel cell electric vehicle powertrain system. Due to the involvement of remote connection and the Internet, test with connected test benches will suffer great uncertainty cause of signal transfer delay. To figure out this uncertainty, the concept of transparency is introduced. Four parameters were selected as transparency parameters in this distributed test platform. These include vehicle speed, fuel cell output power, battery output power, and electric motor torque under several different configuration settings. With the help of transparency theory and statistical methodology, especially Analysis of Variance (ANOVA), the transparency of these four parameters was established, vehicle speed, electric motor torque, battery power, and fuel cell power are affected by network state, the degree of influence is enhanced in turn. Using new defined parametric and non-parametric methods, this paper identifies the statistical significance and the transparency limitations caused by Internet under these several configurations. These methods will generate inputs for developer setting the distributed test configuration. These results will contribute to optimize the process of geographically distributed validation and joint development.

MODEL OF THE TRACTION ASYNCHRONOUS ELECTRIC DRIVE IN THE MODE ELECTRODYNAMIC BRAKING WITH A SCALAR CONTROL SYSTEM

This article is devoted to the problem of traction asynchronous electric drive operation in normal and abnormal conditions in the mode of electrodynamic braking. The proposed simulation model allows us to study the dynamical processes that arise in a traction asynchronous electric drive while driving on sections with different coupling coefficient of wheel pairs with a rail. The simulation model is rather versatile, which allows us to analyze in detail the electromagnetic and electromechanical processes occurring in a frequency controlled driven asynchronous electric drive taking into account changing conditions of rolling stock operation in electrodynamic braking, to evaluate the energy and operational parameters, to investigate the influence of parameters of the frequency converter, traction engine, parameters links of direct current to the nature of the transition processes, using modern methods of mathematics some simulation. As an example, the results of the simulation of a traction asynchronous electric motor with a scalar control law in the mode of electrodynamic braking with stabilization of the voltage in the DC link and the control of the braking effort, depending on the coupling coefficient of the wheel coupling with the rail, are given. The proposed system of protection against excessive slipping and skid wheel pairs can prevent the occurrence of abnormal operating mode of the traction asynchronous electric drive in the mode of traction and electrodynamic braking with a sharp change in the coupling coefficient of the wheel coupling with a rail, to identify the restoration of a satisfactory coupling coefficient and to analyze the need for adjusting the traction and braking torque of the traction asynchronous electric motor depending on the condition of the surface of the rails.

Investigation of nonlinear characteristics of the motor-gear transmission system by trajectory-based stability preserving dimension reduction methodology

Gear-motor system is a typically nonlinear system because of many nonlinear factors, such as time-varying meshing stiffness, backlash, and the nonlinear relationship between the electric motor torque and speed. At present, the nonlinear analytical methods can only be used for simplified gear dynamic model. Though the numerical methods can be used for the complicated dynamic model, the quantitative analysis of stability is difficult and rarely conducted. Therefore, a kind of trajectory-based stability preserving dimension reduction (TSPDR) methodology is proposed to investigate nonlinear dynamic characteristics of the gear-motor system. In the TSPDR methodology herein, the complementary cluster center of inertia-relative motion (CCCOI-RM) transformation is chosen and the stability margins are specially defined for distinguishing the stable motion modes of the motor-gear system, to make the TSPDR methodology used in the nonlinear analysis of the gear-motor system. Furthermore, the critical values are obtained for alteration of different motion modes and the nonlinear characteristics of each motion modes are analyzed. At last, combined with modal analysis, the relationship between the stability and resonance of the gear-motor system is revealed.

Robust uncertainty modelling of energy variations in electric motors for efficient and reliable mechanical structural analysis

The mechanical power and rotational speed of electric motors have significantly uncertainties arising from energy variations such as the magnetic energy, the flux linkage variation of the winding, and the air gap due to the rotor position. The main aim of this work is to address the effect of the uncertain output power and rotational speed of an electric motor on mechanical structural analysis, especially on the torsional analysis, and accordingly to model the statistical characteristics of variations in torque of the motors in consideration of different powers and speeds for further efficient and reliable mechanical structural analysis under uncertainty. To perform these tasks, a case study that is the torsional loading of a shaft by an electric motor and generator, is carried out. The results show that the uncertainty of power and speed in electric motors considerably affects the probability of failure of the shaft in case of exceeding the maximum shear stress, and increasing the speed at a given power does not significantly change the COV value of the torque whereas increasing the power at a given speed can relatively change the COV value of the torque. The obtained average of the COV values (0.0023) of torque with normal distribution is fairly sufficient for indicating the variations in the torque of electric motors. Moreover, the obtained torque uncertainty can be easily and efficiently used in the mechanical structural analysis under both deterministic and stochastic cases.

Hierarchical control strategy with battery aging consideration for hybrid electric vehicle regenerative braking control

Regenerative braking is a key technology for hybrid electric vehicles (HEVs) to improve fuel economy, and it is a multi-objective control problem, which should ensure vehicle braking safety, recover more energy, and protect components from aging. As is known, battery is the most sensitive component in hybrid powertrain, so a large recover current can cause damage to the battery and reduce its life. However, the damage to is usually ignored in regenerative braking. Therefore, this paper proposed a hierarchical control strategy with battery aging consideration to solve the problem. In the up-level controller, the control targets are to recover more energy and minimize aging of the battery in general braking mode, and ensuring the vehicle braking safety in emergency braking mode at the same time. The low-level controller receives the commands of the up-level controller, and controls the pneumatic braking system and the electric motor (EM). The constraints of maximum EM torque and maximum battery charging power are set to protect the EM and the battery. Simulation tests are designed to indicate the effects of regenerative braking on battery aging and the control effectiveness of the proposed method, and controller-in-the-loop tests are carried out to verify the real-time calculation performance.

Fuel Cell Power Train System Simulation of a Car SAMAND SOREN

Due to increasing energy crisis and environmental problems because of air pollution, fuel cell hybrid vehicles are considered as an alternative for internal combustion (IC) vehicles. Proton exchange membrane fuel cells (PEMFC) are the most proper kind of fuel cells for portable usage due to high power density and low performance temperature. In this paper, power train system of a real car, SAMAND SOREN, is modeled and simulated using a dynamic model in MATLAB/SIMULINK software. Five important subsystems in the model are: cathode air supply system, anode fuel supply system, electric motor, battery, and power transmission system. Finally, parameters like power and voltage produced by fuel cell, electric motor torque and vehicle speed are demonstrated as results.

Dynamics characteristics analysis and control of FWID EV

Compared with internal combustion engine (ICE) vehicles, four-wheel-independently-drive electric vehicles (FWID EV) have significant advantages, such as more controlled degree of freedom (DOF), higher energy efficiency and faster torque response of an electric motor. The influence of these advantages and other characteristics on vehicle dynamics control need to be evaluated in detail. This paper firstly analyzed the dynamics characteristics of FWID EV, including the feasible region of vehicle global force, the improvement of powertrain energy efficiency and the time-delays of electric motor torque in the direct yaw moment feedback control system. In this way, the influence of electric motor output power limit, road friction coefficient and the wheel torque response on the stability control, as well as the impact of motor idle loss on the torque distribution method were illustrated clearly. Then a vehicle dynamics control method based on the vehicle stability state was proposed. In normal driving condition, the powertrain energy efficiency can be improved by torque distribution between front and rear wheels. In extreme driving condition, the electric motors combined with the electro-hydraulic braking system were employed as actuators for direct yaw moment control. Simulation results show that dynamics control which take full advantages of the more controlled freedom and the motor torque response characteristics improve the vehicle stability better than the control based on the hydraulic braking system of conventional vehicle. Furthermore, some road tests in a real vehicle were conducted to evaluate the performance of proposed control method.

Flywheel–infinitely variable transmissions for energy recovery capabilities in artificial knee joints

ABSTRACTIn this work, we present a novel architecture of the flywheel–infinitely variable transmission (F-IVT) actuator with increased energy saving performance. The F-IVT is an actuator for artificial knee joints with energy recovery capabilities. It uses a flywheel and an IVT with the purpose of storing and releasing energy and stabilizing the motor working point. The architecture proposed herein, named “linear F-IVT”, is compared with the rotating F-IVT and with the clutchable-series elastic actuator, through a model-based approach. By simulating the operation of these actuators in walking at different speed and stairs climbing of different inclination, the linear F-IVT results to be the most effective in reducing the peak of electric power and motor torque, also achieving a reduction of the electric energy demanded. These results suggest the possibility to achieve a significant motor downsizing, possibly leading to the development of a lightweight actuator to improve the portability and the operating range of wearable robots for lower limbs.Abbreviations: BS: ball screw; C-SEA: clutchable - series elastic actuator; CVT: continuously variable transmission; F-IVT: flywheel–infinitely variable transmission; HD: harmonic drive; IVT: infinitely variable transmission

Mode transition coordination control for parallel hybrid electric vehicle based on switched system

Hybrid electric vehicles equipped with several different power sources can change operation mode to deal with different operating conditions to improve fuel economy and reduce exhaust emissions. Due to the significant difference in the characteristics of the power sources and the discontinuity in the dynamics of the clutch, noticeable torque fluctuations occur during mode transition, which may result in system shock and an uncomfortable riding sensation. Based on the idea of a switched system, we proposed a three-stage control strategy to facilitate a smooth transition from electric mode to hybrid driving mode. In this coordination control strategy, a fuzzy-proportional–integral mixed controller was used to manipulate engine speed and an adaptive sliding mode controller was applied to control the electric motor torque for compensating for torque disturbances. Furthermore, the proposed control strategy was validated on hardware-in-the-loop simulation platform. The results demonstrate the effectiveness of t...

Electric motor-based crankshaft stop position control to suppress range extender start vibration in electric vehicle

Range-extended electric vehicles have the most complex noise and vibration problems since certain control strategies often make range extenders (REs) shut down or restart for the sake of better fuel consumption. This paper deals with this uncomfortable riding experience, especially during the range extender start phase. A control-oriented nonlinear model for the start–stop vibration analysis, including range extender mount system, engine–clutch–motor shaft system, engine inertia torque and force, engine friction torque, engine gas torque, engine manifold pressure, electric motor torque, and range extender controller, is thus built. In the developed model, a new estimation method for gas torque is proposed, where the initial crank angle is considered and the relevant equations are simplified. The method has proven to predict gas torque accurately without using a complex calculation process. According to the developed model, the active control method, crankshaft stop position control (CSPC) has been proposed. The crankshaft stop position is analyzed as well as the crankshaft movement with different speeds at top dead center is discussed, which lead to the design of the target curves for crankshaft movement during the stop phase. Based on the set-up model, CSPC is finally applied through the cascade control of the motor to evaluate the control effectiveness. The simulation outcomes demonstrate that CSPC can help the crankshaft to finally stop at the optimal initial crank angle, which effectively lessens the vibration in the next start phase.

Gas torque compensation control for range extender start-stop vibration reduction in electric vehicle

One of the key challenges with the development of range extended electric vehicles is the noise, vibration and harshness behavior, specifically the uncomfortable ride experience during the range extender starting and stopping. This article focuses on providing an active control method to address this critical noise, vibration and harshness issue. A control-oriented nonlinear model for the start-stop vibration analysis, including range extender mount system, engine-clutch-motor shaft system, engine inertia torque and force, engine friction torque, engine gas torque, engine manifold pressure, electric motor torque and range extender controller, is thus built. In the developed model, a new estimation method for gas torque is proposed, where the initial crank angle is considered as well as the relevant equations are simplified. The method is proved to predict gas torque accurately without the expense of complex calculation process. Based on the model, the mount system vibration response has been analyzed that the excitation of range extender block on vehicle body in x-direction is the most prominent. The concept of the active control method, gas torque compensation control, is thus introduced in detail to reduce such a system vibration during start-stop phase. According to the control principle, the torque compensation coefficient for gas torque compensation control is determined and the compensation speed range is analyzed. In order to evaluate the control effectiveness, gas torque compensation control is implemented in the set-up model. The simulation outcomes demonstrate that gas torque compensation control is effective in reducing the vibration generated during start-stop transitions.

Preventing Damage in Hydraulic Pumping Systems by using a Pressure Control Strategy

This paper presents an experimental study on the development, implementation, and tests of a control strategy applied to pressure control in hydraulic pumping systems. The strategy aims at avoiding severe damage on the hydraulic system due to Water Hammer effects. To accomplish this, it is proposed a suitable modulating control of the pump electric motor torque in order to keep the pressure values in a safe region, for all set of operating conditions. A rig system has been developed to perform experimental tests. From step response tests in the hydraulic rig system, a transfer function model relating the pipe pressure to the motor speed was identified and subsequently applied for PID controller design. The PID control synthesis was performed by using pole-placement techniques and its performance has been assessed in comparison to a PID controller adjusted by using Ziegler-Nichols rules. The obtained results show that the proposed control strategy was able to assure safe plant operation even in extreme operation conditions, as in case of Water Hammer effect.

CALCULATION OF A MECHANICAL CHARACTERISTIC OF ELECTRIC TRACTION MOTOR OF ELECTRIC VEHICLE

The traction characteristic of an electric vehicle is the main characteristic of mechanical system that reflects its key performance indicators. Implementation of the traction characteristic is based on controlling angular speed and torque of electric traction motor in an automatic control system. The static mechanical characteristic of an electric traction motor in an automatic control system is the most important characteristic that determines weight, size and operating characteristics of an electric traction motor and serves as the basis for design. The most common variants of constructive implementation of a traction electric drive are analyzed, and a scheme is chosen for further design. Lagrange’s equation for electric mechanical system with one degree of freedom is written in generalized coordinates. In order to determine the generalized forces, elementary operation of all moments influencing on a moving car has been calculated. The resulting equation of motion of the electric vehicle corresponding to the design scheme, as well as the expressions for calculation of characteristic points of static mechanical characteristics of traction motor (i.e. the maximum and minimum time, minimum power) are obtained. In order to determine the nominal values of the angular velocity and the power of electric traction motor, a method based on ensuring the movement of the vehicle in the standard cycle has been developed. The method makes it possible to calculate characteristic points of the mechanical characteristic with the lowest possible power rating. The algorithm for calculation of mechanical characteristics of the motor is presented. The method was applied to calculate static mechanical characteristic of an electric traction motor for a small urban electric truck.

Electric Vehicle Longitudinal Stability Control Based on a New Multimachine Nonlinear Model Predictive Direct Torque Control

In order to improve the driving performance and the stability of electric vehicles (EVs), a new multimachine robust control, which realizes the acceleration slip regulation (ASR) and antilock braking system (ABS) functions, based on nonlinear model predictive (NMP) direct torque control (DTC), is proposed for four permanent magnet synchronous in-wheel motors. The in-wheel motor provides more possibilities of wheel control. One of its advantages is that it has low response time and almost instantaneous torque generation. Moreover, it can be independently controlled, enhancing the limits of vehicular control. For an EV equipped with four in-wheel electric motors, an advanced control may be envisaged. Taking advantage of the fast and accurate torque of in-wheel electric motors which is directly transmitted to the wheels, a new approach for longitudinal control realized by ASR and ABS is presented in this paper. In order to achieve a high-performance torque control for EVs, the NMP-DTC strategy is proposed. It uses the fuzzy logic control technique that determines online the accurate values of the weighting factors and generates the optimal switching states that optimize the EV drives’ decision. The simulation results built in Matlab/Simulink indicate that the EV can achieve high-performance vehicle longitudinal stability control.

Metrological characteristics of the torque measurement of electric motors

This paper proposes a method of determination of the basic metrological characteristics of measurement means (MM) in order to measure the torque of electric motors (EM), such as sensitivity, nominal conversion functions, and additive and multiplicative errors. The nature of change of metrological characteristics was researched using the Measurand Model derived, in the conversion measuring range studied in this paper. Summarised values for additive and multiplicative errors were established for the MM of torque, under the conditions of deviation in terms of the impact value from its nominal value. In addition, the methodology was analysed to enable recalculation of additive and multiplicative errors related to the standard uncertainty of type B. This was undertaken to establish the quality of measurement according to international standards. The research was founded on Measurand Model obtained for multiplicative and additive components in the errors inherent in torque MM.

EFFICIENCY ANALYSIS OF ENERGY ACCUMULATING MECHANISM FOR TRACTOR WITH ELECTROMECHANICAL TRANSMISSION

Dependence of tractor wheel torque on theoretical tractor motion speed has been used for comparison of tractor operation with electromechanical transmission with installation of energy accumulating mechanism and without its installation. In this case a traction asynchronous electric motor is operating under nominal and limit conditions. The paper also considers dependence diagrams of actual input power for the traction asynchronous electric motor and its losses due to theoretical tractor motion speed. Tractor wheel torque is limited during the operation of the traction asynchronous electric motor with energy accumulating mechanisms by the following factors: maximum electric motor torque at the given frequency of supply voltage; maximum value of internal combustion motor output which can be transferred to the traction asynchronous electric motor; grip of the wheels. During the operation of the traction asynchronous electric motor with energy accumulating mechanisms there is a possibility for short power consumption without regard to the second limitation because it is possible to use power not only of internal combustion motor but also the power which is stored in the energy accumulating mechanisms. Comparison of characteristics has been made when a tractor is operating at high gear and when it is operating at all gears (that is two gears). Operation of the 5th class tractors has been analyzed for all possible cases (operation with energy accumulating mechanisms and without the mechanisms while being operated at all gears) and various types of work: tilling, sowing, cultivation, bulldozing work, transport mode. In this case equipment has been used which is aggregated with the 5th class tractor.