Motor Efficiency Map Research Articles

Simulation of BLDC Motor Drive Systems for Electric Vehicles Using Matlab Simulink

The defining scientific developments of our time would not have been possible without the use of simulations. The aim of the research is to create a simulation of a BLDC motor. When creating a simulation, great emphasis must be placed on defining the purpose of the simulation. This basically determines the structure and complexity of the model. The model discussed here was created so that an optimization task could be defined more precisely by inserting it as a sub-model into a vehicle dynamics model. Scalability was another aspect, that is, to be able to increase the accuracy of the model with measured data in the future, as well as to be able to validate it. During the research, a BLDC motor efficiency map generation program was created, as well as an environment for testing the generated data. The created system gives researchers the opportunity to use a shape-correct efficiency model when simulating a BLDC motor even without measured data. This makes it possible to discover real relationships between model parameters when performing optimization.

An energy-saving regulation approach based on economic rotational speed and power split feature for more electric turboshaft engine

More electric turboshaft engine is comprised of turboshaft engine and electric machines which are connected to each shaft of the engine. More electric turboshaft engine has great development potential in hybrid electric power systems in automobile and aircraft due to their high power-to-weight ratio. To reduce fuel consumption and environmental pollution, it is essential to design an energy-saving control method that can improve the fuel economy of more electric turboshaft engines within the full range of output power. In this paper, an economic rotational speed and power split feature (E-RSPSF) based compound energy-saving regulation approach is proposed for improving the fuel economy of more electric turboshaft engines. First, based on the configuration of more electric turboshaft engine, considering the power transfer balance constraint of shaft motors, augmented co-working balance equations of more electric turboshaft engine are derived by integrating a motor efficiency map. Second, a hierarchical optimization approach utilizing an improved particle swarm optimization method is presented for solving E-RSPSF based on the augmented co-working balance equations, and an E-RSPSF based regulation approach is formulated for better fuel economy of more electric turboshaft engine. Finally, the reason for the improvement in fuel economy by the E-RSPSF is discussed, and the importance of the actual motor efficiency map in the proposed E-RSPSF based regulation approach is presented. The comparison results show that the proposed energy-saving regulation approach with E-RSPSF considering both the economic rotational speed and power split can achieve a maximum 12.5% decrease in fuel consumption, which is higher than that with either rotational speed regulation or power split regulation.

Power Consumption Simulation of Servo Motors Focusing on the Influence of Mechanical Vibration on Motor Efficiency

This paper presents a simulation method for the power consumption of servo motors, focusing on the influence of vibrations on the motor efficiency. An apparatus consisting of two servo motors connected through a coupling was specifically designed for this study. The efficiency of the servo motor was experimentally investigated for several torque vibration levels imposed through the selection of the control parameters, and the torque vibration level was quantified through the standard deviation of the torque signal. The efficiency map characteristics for each torque oscillating level were determined. A numerical model of the apparatus clarifying the dependency of the coupling characteristics on the oscillating torque was developed, and the torque oscillation of the system was simulated. A model based on the measured motor efficiency maps and the torque oscillation level was developed to simulate the motor efficiency under several torque vibrating conditions. Finally, the power consumption of the motor was simulated based on the simulated efficiency and mechanical power. A balance of input, output, and loss powers was presented, and the experimental measurements were compared with the simulation results. The power consumption of the motor increased when the torque oscillated owing to vibrations, and the loss of power due to both oscillations and the loss of motor efficiency was quantified.

Coupled Finite Element and Extended-QD Circuit Induction Machine Model, Part I: Formulation

The design of squirrel-cage induction motors (IMs) entails the capability to predict the motor efficiency map with high accuracy over an operating range. In particular, modeling harmonic rotor bar currents becomes important for loss analysis. In theory, it is possible to analyze an induction motor using time-stepping finite element analysis (TS-FEA); however, this is not viable due to computational limitations. To bridge this gap, we set forth a computationally efficient method that couples magnetostatic FEA with a qd-circuit model of the cage. The proposed IM model includes the effects of saturation, winding and slot harmonics, as well as nonuniform current density distribution in the rotor bars. The model is presented in two parts. Part I focuses on the formulation of a qd cage circuit model with segmented bars. Part II is a companion paper that proposes an FEA-based parameter estimation and a solution method.

Evaluating the influence of mechanical system vibration characteristics on servo motor efficiency

In this study, the influence of mechanical vibration characteristics on the efficiency of a servo motor was experimentally investigated. For this purpose, a dedicated apparatus comprising two servo motors connected to a coupling was used. The efficiency of the motor was investigated by first considering the signals of voltage and current; then, the mechanical power was calculated from the acquired torque and angular velocity supplied by the motor. Subsequently, working conditions involving different angular velocities and loading torques were investigated to generate a motor efficiency map. To clarify the influence of the vibration characteristics on the motor efficiency, two types of couplings differing in torsional stiffness and damping characteristics were considered—Type A and Type B. The efficiency was calculated for eight vibration conditions imposed via the selection of the velocity control gain settings for both types. Resultantly, the manner in which the efficiency is affected by the vibration conditions was clarified. Moreover, coupling in the case of better vibration damping characteristics was confirmed to yield a higher motor efficiency for all gain settings. Furthermore, motor working conditions corresponding to high and low motor efficiencies were evaluated, and the motor thermal behavior was investigated. Overall, a lower motor efficiency was confirmed to be associated with increasing temperatures. These results suggest the importance of the vibration characteristics of mechanical systems for achieving high efficiency.

Optimal Cooperative Brake Distribution Strategy for IWM Vehicle Accounting for Electric and Friction Braking Torques

Electric vehicles are spreading in automotive industry pushed by the need of reducing greenhouse gas. However, the use of multiple electric motors, i.e., one per wheel, allows to redefine the vehicle powertrain layout with great benefits on vehicle dynamics. Electric motors braking torque is in general not enough to produce high decelerations. Hydraulic friction brakes are still necessary for safety reasons and to avoid oversized motors. This paper presents a control strategy for distributed electric motors (EM), one per wheel, to maximize the regenerative braking. The controller handles cooperative braking among EMs and hydraulic brakes, which are still necessary to guarantee top braking performance of the car. The proposed algorithm considers the driver requested braking torque as well as the required yaw moment by stability control system. Motor efficiency map and wheel normal load are considered to optimally distribute the torques. With respect to conventional distribution strategies, the presented algorithm improves performance, maximizing the regenerative braking power.

Optimization and coordinated control of gear shift and mode transition for a dual-motor electric vehicle

The electric vehicle equipped with dual motors and four-speed automated manual transmission has demonstrated its superiority in improving energy efficiency and dynamic performance. To exploit this configuration effectively, optimal shift schedules and corresponding mode selection maps are proposed separately for accelerating and braking conditions. Hysteresis zones between upshift and downshift lines are created by properly integrating a priority factor into the equivalent motor efficiency. Interestingly, the proposed shift schedules depend not only on the motor efficiency map, motor torque allocation, but also on the current working gear pair. Besides, the intersections of the shift schedules and mode selection borders show that gear shift and mode transition need to be implemented at the same time. Therefore, a coordinated control strategy is developed to handle these requirements. Finally, simulation results show that the case of without hysteresis zones achieves minimum electricity consumption but with many undesired and unnecessary gear changes. Conversely, with comparable energy economy, the introduced priority factor of 0.02 avoids the shift hunting effectively. Moreover, taking the advantages of the powertrain configuration, the proposed coordinated control strategy eliminates all torque gaps under the gearshift and mode transition, so great shift quality is achieved.

A Novel Electric Dual Motor Transmission for Heavy Commercial Vehicles

As a vital vehicle part, the powertrain system is undergoing a fast transition towards electrification. The new integrated electric drive system has been widely used, especially for passenger cars. In this work, a novel electric dual motor transmission is proposed for heavy commercial vehicles. The transmission scheme is firstly introduced, which can achieve 9 different operating modes including 5 single motor modes and 4 dual motor modes. Then, the mode shift map with minimum energy consumption is designed based on the motor efficiency map and the proposed energy management strategy. The driving power is appropriately distributed between the two motors in dual motor modes under the condition of minimum power consumption. In addition, a coordinated control strategy is developed for mode shift control without power interruption. The results show that the electric dual motor transmission has advantages in power consumption and power shift ability compared with the conventional single motor automated manual transmission.

Drivetrain modelling and parameter calculation for an electric bus with fixed or 2-speed gearbox

This paper presents drivetrain calculations for an electric bus. Parameters of motor, gears and motor efficiency map are used. The goal is to select the suitable motor and gearbox. Driving cycle SORT2 and real life driving cycles measured on bus lines are used. Based on the bus manufacturer assignment, only permanent magnet synchronous machines are considered. The motor output power is considered in the range of 120-160 kW. The selection of axle gear ratios was limited to 6.19, 6.5 and 7.35, as those are readily available. The gearbox was either a fixed one, with gear ratio of 1.8, or a 2-speed gearbox with a gear ratio of 1 and 1.8. The calculations have shown, that a 2-speed gearbox can decrease the energy consumption. The improvement is in the range of 1-3% dependent on the motor option and driving cycle.

An Optimal Torque Distribution Strategy for Four-Motorized-Wheel Electric Vehicle Considering Energy Conversation

In this paper, an optimal torque distribution strategy (OTDS) for four-motorized-wheel electric vehicle (4MWEV) is proposed aiming at improving the tractive efficiency and braking energy recovery performance. Based on the motor efficiency map, the objective functions of tractive efficiency and braking energy recycling are established first. Under driving conditions, genetic algorithm (GA) is proposed to obtain the optimal torque distribution ratio of front and rear axles considering the constraints of motor characteristics and desired torque. During braking conditions, an exhaustive search method (ESM) is proposed to improve the energy recovery performance considering the constraints of motor characteristics, battery, braking theory and ECE Regulations. For the realization of efficient and accurate computation, a control scheme of off-line optimization and on-line allocation based on the optimal torque distribution ratio map is presented, which stores the optimal ratios in all available motor operating regions into two-dimensional lookup tables. Finally, co-simulation experiments based on MATLAB/Simulink and Carsim are conducted to verify the effectiveness of the proposed OTDS under NEDC and UDDS driving cycles. Comparing to the typical torque distribution strategy (TTDS), the simulation results demonstrate that the proposed OTDS can enhance the energy-saving performance by 7.01% under NEDC and 6.69% under UDDS.

A stability-guaranteed and energy-conserving torque distribution strategy for electric vehicles under extreme conditions

For electric vehicles with in-wheel motors, the torque distribution strategy is used to manipulate their dynamics to reduce energy consumption and ensure safety. Under critical conditions, it is difficult to meet the necessary requirements with a simple torque distribution due to the coupled nonlinear characteristics and corresponding safety constraints. To address these problems, a stability-guaranteed and energy-conserving torque distribution strategy is proposed for the vehicles in an innovative master-slave control framework. Considering the dynamic characteristics of tires on a low-friction-coefficient road, a nonlinear controller is designed to regulate the steering angle of the front wheel and an additional yaw moment in the active safety control layer. According to the driver’s dynamic demand and actuator constraints, a torque distribution controller based on model predictive control theory is designed in the energy-efficiency control layer. The motor efficiency map is used in the objective function to reduce energy consumption while improving and balancing motor efficiency. The proposed torque distribution strategy managed to show an increment of 4.50%, 0.80% with previous in energy saving under double lane change and straight acceleration maneuvers respectively, while the power loss does not exceed 0.08%.

A direct multiple shooting method to improve vehicle handling and stability for four hub-wheel-drive electric vehicle during regenerative braking

Regenerative braking is an important technology to improve fuel economy for electric vehicles. Apart from improving energy recovery efficiency and vehicle stability, the arithmetic speed of the algorithm is also essential for an automotive-qualified micro control units. This paper presents a direct multiple shooting method–based algorithm to achieve multiple objectives for four hub-wheel-drive electric vehicle during mild braking situations. Mathematical models of the system are generated for numerical simulations in MATLAB, including a vehicle dynamics model, a modified tire model, a single-point preview driver model, and a regenerative braking motor efficiency map. With the limitation of hard constraint and minimization of adjustment rate in cost function, optimization tends to be accomplished by distribution of braking torque in front and rear wheels. Furthermore, the control strategy has been realized using a direct multiple shooting method to convert the nonlinear optimal control problem to a nonlinear programming problem, which will be settled by adopting a sequential quadratic programming method in each subintervals. The effectiveness and adaptation of the control strategy for four hub-wheel-drive electric vehicle has been evaluated by conducting many simulations during mild braking situations, and the simulation results also demonstrated that the direct multiple shooting–based strategy exhibits a better performance than that of proportional-integral-based or nonlinear model predictive control–based controller.

Hierarchical Coordinated Control Method of In-Wheel Motor Drive Electric Vehicle Based on Energy Optimization

In order to improve the endurance mileage and stability of an electric vehicle at the same time, a hierarchical coordinated control method of an in-wheel motor drive electric vehicle based on energy optimization is presented in this paper. The driving architecture of an in-wheel motor drive electric vehicle is developed, and a corresponding simulation model is established in CarSim software; then, the bicycle model of an electric vehicle is derived from vehicle dynamic equations. The energy-saving feasibility of an in-wheel motor drive electric vehicle is analyzed by a motor efficiency map, and on the basis of this, the hierarchical coordinated control method is proposed to achieve the simultaneous energy optimization control and stability control of the electric vehicle. The results show that the energy consumption is decreased by 32.41%, 45.92%, and 4.07% in different simulation manoeuver cases, and the vehicle stability can be ensured by the proposed control method.

Energy management and shifting stability control for a novel dual input clutchless transmission system

A dual input clutchless transmission system based on automated manual transmission (AMT) structure is developed for pure electric vehicles. An energy management strategy (EMS) is proposed to determine the power distribution between two motors and the optimal gear state. A mathematical model is built to minimize the energy consumption of the motors at each instant based on the motor efficiency maps. However, the proposed EMS in line with other energy-oriented strategies often result in excessive gear shifts and compromised drivability. To avoid the undesired gear shift, a shifting stabilizer is built in the EMS objective function to improve the shift quality. Accordingly, to achieve a balance between the energy consumption and the drivability, a multi-objective optimization method is adopted to reduce the unnecessary shift events while minimizing energy consumption. Two driving cycles representing typical daily driving conditions are used to demonstrate the effectiveness of the proposed system in terms of energy efficiency and shifting stability.

A Dual-motor Coupling Propulsion System Design and Control Strategy Optimization for an Electric Coach

Conventional electric coach bus calls for high-performance drive motor with its single-motor driveline system, especially in areas with harsh road environment. A dual-motor coupling propulsion system with multi-speed transmission offers the possibility of comprehensive improvement of the whole vehicle. This paper takes a high-performance electric coach as research object to design a matching dual-motor propulsion system with two-speed transmission. Firstly, the dual-motor parameters are matched according to the performance requirements of the coach, then the motor efficiency map is analyzed and matched for higher energy efficiency. Secondly, a coach model with system above is built, on which an energy-optimized online control strategy is proposed, which gives gearshift schedule and torque-allocation proportion. At last, with back propagation (BP) artificial neural network, the control rule is extracted, which can be easily used in practice. The simulation results show that， compared with the preliminary dual-motor system with a rule-based strategy， the energy economy based on the proposed design decrease by 15.6 % with the new strategy. It indicates that the proposed design and control strategy provides a significant improvement of energy efficiency and dynamic performance for electric coach.

Comprehensive chassis control strategy of FWIC‐EV based on sliding mode control

Four-wheel independent control electric vehicle has possessed tremendous potentials because the enhancement of driving performance and energy savings can be simultaneously carried out by independent and precise driving/braking/steering control. The study has proposed a comprehensive control strategy aiming at all normal conditions, which employs hierarchical architecture to reach the above-mentioned control. In the high-level controller, sliding mode control scheme is developed to figure out total force and yaw moment. In the low-level controller, energy-efficiency optimisation allocation is presented to reduce motor power losses and obtain energy recovery based on motor efficiency map, and then steering angle allocation is conducted to decrease the lateral force so as to reduce power losses caused by the tyre sideslip. Considering insufficient motor braking torque during large deceleration or even larger, the blended brake control strategy with the motor brake and electric hydraulic brake and further anti-skid brake system control via adopting fuzzy logic method are carried out. The torque and pressure are gained to deliver the corresponding actuators model established according to their physical characteristics. Through CarSim-MATLAB/Simulink-AMEsim co-simulation, results suggest that the developed strategy can boost the vehicle manoeuvrability and reduce energy consumption generated by motors and tyre sideslip under all the conventional occasions.

Energy saving control based on motor efficiency map for electric vehicleswith four-wheel independently driven in-wheel motors

For four-wheel independently driven in-wheel motor electric vehicles, the four-wheel drive/braking torque can be controlled independently. Therefore, it has an advantage that energy saving control can be applied effectively. This article studies several energy saving control methods from two levels of driving and braking for four-wheel independently driven in-wheel motor electric vehicles under urban conditions based on the motor efficiency map. First, the energy saving control logic and the evaluation index were proposed in the article. The four-wheel drive torque was online optimized in real time through drive energy saving control, in order to improve the driving efficiency in the driving process of electric vehicles. According to the theory of ideal braking force distribution and Economic Commission of Europe braking regulations, the parallel regenerative braking control method based on the motor efficiency map was then studied. The parallel regenerative braking control method was applied to four-wheel independently driven in-wheel motor electric vehicles. The simulation analysis under typical urban driving cycle conditions was carried out to determine the braking intensity of the parallel brake front axle separate regenerative braking, and finally the braking energy recovery rate of electric vehicle can be improved in the low speed and low braking torque. Finally, simulation experiments have been carried out to verify the researched method under the NEDC, UDDS, and J1015 urban driving cycles. The simulation results show that the energy saving control methods have an obvious effect on energy saving under the urban driving cycle conditions.

Gear Ratio Optimization of a Multi-Speed Transmission for Electric Dump Truck Operating on the Structure Route

Research demonstrated that the application of a multi-speed transmission could improve the dynamic and economic performance of electric vehicles. This paper deals with a novel multi-speed transmission for the electric dump truck (EDT) operating on the structure route (SR), which has a definite starting point and end point without complex traffic conditions. To optimize the gear ratio and shift schedule to reduce energy consumption in such conditions, the mathematical model of the transmission and the dynamic model of the EDT are initially required. Following this, the shift schedule is presented according to the motor efficiency map. After that, the gear ratio optimization is carried out by a particle swarm optimization (PSO) algorithm. Moreover, the proposed EDT is compared with an EDT with a single-speed transmission. The simulation results show that the energy consumption is reduced by 6.1%.

A hierarchical energy efficiency optimization control strategy for distributed drive electric vehicles

Distributed drive electric vehicle with four in-wheel motors is widespread with various characteristics, such as performance potentials for independent wheel drive control and energy efficiency. However, in future, one of the biggest obstacles for its success in the automotive industry would be its limited energy storage. This paper proposes a hierarchical control method that involves a high-level motion controller that uses sliding mode control to calculate the total desired force and yaw moment and a low-level allocation controller in which an optimal energy-efficient control allocation scheme is presented to provide optimally distributed torques of four in-wheel motors in all the normal cases. A practicable motor energy efficiency model as a motor actuator is proposed by incorporating the electric motor efficiency map based on measured data into the motor efficiency experiment and a current closed-loop motor model. Moreover, both tracking performance and energy-saving are carried out in this research and evaluated via a co-simulation approach using MATLAB/Simulink and CarSim. A ramp maneuver at a constant speed and New European Driving Cycle and Urban Dynamometer Driving Schedule maneuvers have been conducted. To conclude, it is demonstrated that distributed drive electric vehicle with four in-wheel motors can reduce total power consumption and enhance tracking performance compared with a simple control allocation in which the torques are the fixed ratio distribution.

Energy Management of a Hybrid-Power Gas Engine-Driven Heat Pump

The hybrid-power gas engine-driven heat pump (HPGHP) combines hybrid power technology with a gas engine heat pump. The engine in the power system is capable of operating constantly with high thermal efficiency and low emissions during different operating modes. In this paper, the mathematical models of various components is established, including the engine thermal efficiency map and the motor efficiency map. The comprehensive charging/discharging efficiency model and energy management optimization strategy model which is proposed to maximize the efficiency of instantaneous HPGHP system are established. Then, different charging/discharging torque limits are obtained. Finally, a novel gas engine economical zone control strategy which combined with the SOC of battery in real time is put forward. The main operating parameters of HPGHP system under energy management are simulated by Matlab/Simulink and validated by experimental data, such as engine and motor operating torque, fuel consumption rate and comprehensive efficiency, etc. The results show that during 3600 s’ run-time, the SOC value of battery packs varies between 0.58 and 0.705, the fuel consumption rate reaches minimum values of approximately 291.3 g/(kW h) when the compressor speed is nearly 1550 rpm in mode D, the engine thermal efficiency and comprehensive efficiency reach maximum values of approximately 0.2727 and 0.2648 when the compressor speed is 1575 rpm and 1475 rpm, respectively, in mode D. In general, the motor efficiency can be maintained above 0.85 in either mode.