Drivetrain Losses Research Articles

Optimizing electric vehicle routing under traffic congestion: A comprehensive energy consumption model considering drivetrain losses

Energy consumption is a critical concern within the electric vehicle (EV) industry. Despite its substantial impact, drivetrain losses have been inadequately addressed in some studies. This paper introduces drivetrain losses as a nonlinear function of velocity, incorporating them into the comprehensive energy consumption model. Considering the influence of traffic congestion on vehicle speed, our proposed model integrates drivetrain losses, aerodynamic losses, tire losses, kinetic energy losses, and potential energy losses. The objective is to optimize routing with the aim of minimizing energy consumption. To tackle this problem, we present a dedicated adaptive large neighborhood search algorithm. Our numerical experiments reveal key findings: (1) Drivetrain losses represent a higher percentage of total energy consumption compared to aerodynamic and tire losses; (2) Drivetrain losses influenced by traffic congestion constitute a significant share, ranging between 63.82% and 72.08% of total energy consumption; (3) Energy consumption experiences notable increases under the impact of traffic congestion.

Hybrid Output Voltage Modulation (PWM-FSHE) for a Modular Battery System Based on a Cascaded H-Bridge Inverter for Electric Vehicles Reducing Drivetrain Losses and Current Ripple

This paper shows a preliminary study about the output voltage modulation of a modular battery system based on a seven-level cascaded H-bridge inverter used for vehicle propulsion. Two generally known modulation techniques, pulse width modulation (PWM) and fundamental selective harmonic elimination (FSHE), are extensively compared for such an innovative modular battery system inverter considering EVs’ broad torque-speed range. The inverter and the battery losses, as well as the inverter-induced current THD, are modeled and quantified using simulations. At low speeds, if the modulation index M is below 0.3, FSHE induces a high current THD (>>5%) and, thus, cannot be used. At medium speeds, FSHE reduces the drivetrain losses (including the battery losses), while operating at higher speeds, it even reduces the current THD. Thus, an individual boundary between multilevel PWM and FSHE can be determined using weightings for efficiency and current quality. Based on this, a simple hybrid modulation technique is suggested for modular battery system inverters, improving the simulated drive cycle efficiency by a maximum of 0.29% to 0.42% for a modeled small passenger vehicle. Furthermore, FSHE’s high speed dominance is demonstrated using a simple experimental setup with an inductive load.

Improved Variable DC Approach to Minimize Drivetrain Losses in Fuel Cell Marine Power Systems

This article proposes a novel approach for operating hybrid fuel cell and battery power systems in marine vessels. The target of the approach is to reduce energy losses in drivetrain devices. In the proposed approach, the dc bus voltage of the hybrid power system is adjusted according to fuel cell operating points, which enables operation in freewheel mode, and thus significantly reducing power conversion losses. Feasibility of the proposed approach is verified using a real-time hardware-in-loop simulation setup consisting of prevalidated virtual models and real industrial power converter controllers. The results presented in the work illustrate that the variable dc approach enables significant improvements in drivetrain efficiencies, and thus providing significant savings for vessel operators. Additionally, variable dc approach is shown to eliminate high-frequency current ripple at the fuel cell terminals, which can further improve the efficiency and the lifetime of the fuel cells.

Using Transmission Data to Isolate Individual Losses in Coastdown Road Load Coefficients.

As part of the U.S. Environmental Protection Agency's (EPA's) continuing assessment of advanced light-duty automotive technologies in support of regulatory and compliance programs, the National Vehicle Fuels and Emissions Laboratory has benchmarked multiple transmissions to determine their efficiency during operation. The benchmarking included a modified "coastdown test," which measures transmission output drag as a function of speed while in neutral. The transmission drag data can be represented as a second-order expression, like that used for vehicle coastdown test results, as F 0 + F 1 V + F 2 V 2, where V is the vehicle velocity. When represented in this fashion, the relationships among the three coefficients were found to be highly predictable. The magnitude of these coefficients can be quite large, and for some tested transmissions the deviation between the quadratic regression and the measured drag at individual velocities can be significant. To evaluate the effect of transmission losses in vehicle coastdown tests, the coastdown target and dynamometer set coefficients were pulled from the EPA's published "Data on Cars used for Testing Fuel Economy" for an entire model year. The same relationships seen among transmission coefficients were observed in the vehicle coefficients contained in these data. Therefore, the vehicle coefficients can be used directly to estimate the transmission and drivetrain losses and eliminate them from the coastdown values. With transmission losses eliminated, the remaining losses can be divided to extract more accurate estimations of aerodynamic losses and rolling losses. This process can be applied fleet-wide, using only the reported coastdown and dynamometer test coefficients to estimate the losses from individual sources. The resulting data can then be used to independently evaluate the effects of reducing each separate loss, without the need for detailed information on each vehicle in the fleet.

Separation of Rolling Resistance and Drivetrain Losses at the Flat Belt Dynamometer

Separation of Rolling Resistance and Drivetrain Losses at the Flat Belt Dynamometer

A Study on the Fuel Economy Potential of Parallel and Power Split Type Hybrid Electric Vehicles

What is the best number of gear steps for parallel type hybrid electric vehicles (HEVs) and what are the pros and cons of the power split type HEV compared to the parallel type have been interesting issues in the development of HEVs. In this study, a comparative analysis was performed to evaluate the fuel economy potential of a parallel HEV and a power split type HEV. First, the fuel economy potential of the parallel HEV was investigated for the number of gear steps. Four-speed, six-speed, and eight-speed automatic transmissions (ATs) and a continuously variable transmission (CVT) were selected, and their drivetrain losses were considered in the dynamic programming (DP). It was found from DP results that the power electronics system (PE) loss decreased because the magnitude of the motor load leveling power decreased as the number of gear steps increased. On the other hand, the drivetrain losses including the electric oil pump (EOP) loss increased with increasing gear step. The improvement rate from the 4-speed to the 6-speed was the greatest, while it decreased for the higher gear step. The fuel economy of the CVT HEV was rather low due to the large EOP loss in spite of the reduced PE loss. In addition, the powertrain characteristics of the parallel HEV were compared with the power split type HEV. In the power split type HEV, the PE loss was almost double compared to that of the parallel HEV because two large capacity motor-generators were used. However, the drivetrain loss and EOP loss of the power split type HEV were found to be much smaller due to its relatively simple architecture. It is expected that the power characteristics of the parallel and power split type HEVs obtained from the DP results can be used in the development of HEV systems.

Wind turbine Cp,max and drivetrain-losses estimation using Gaussian process machine learning

In this paper it is shown that measured data in a wind turbine, available to the controller, can be formulated into a polynomial regression problem in order to estimate the turbine’s maximum efficiency power coefficient, Cp,max, and drivetrain losses, assuming the latter can be well approximated as being linear. Gaussian process (GP) machine learning is used for the regression problem. These formulations are tested on data generated using the Supergen Exemplar 5 MW wind turbine model, with results indicating that this is a potential low cost method for detecting changes in aerodynamic efficiency and drivetrain losses. The GP approach is benchmarked against standard least-squares (LS) regression, with the GP shown to be the superior method in this case.

Design Methodology of a Power Split Type Plug-In Hybrid Electric Vehicle Considering Drivetrain Losses

This paper proposes a design methodology for a power split type plug-in hybrid electric vehicle (PHEV) by considering drivetrain losses. Selecting the input split type PHEV with a single planetary gear as the reference topology, the locations of the engine, motor and generators (MGs), on the speed lever were determined by using the mechanical point considering the system efficiency. Based on the reference topology, feasible candidates were selected by considering the operation conditions of the engine, MG1, and a redundant element. To evaluate the fuel economy of the selected candidates, the loss models of the power electronic system and drivetrain components were obtained from the mathematical governing equation and the experimental results. Based on the component loss model, a comparative analysis was performed using a dynamic programming approach under the presence or absence of the drivetrain losses. It was found that the selection of the operating mode and the operation time of each mode vary since the drivetrain loss affects the system efficiency. In addition, even if the additional modes provide the flexibility of selecting the operating mode that results in a higher system efficiency for the given driving condition, additional drivetrain elements for realizing the modes can deteriorate the fuel economy due to their various losses.

Fuel economy and emissions testing of an RCCI series hybrid vehicle

In the current work, a series hybrid vehicle has been constructed that utilises a dual-fuel, reactivity controlled compression ignition (RCCI) engine. Full vehicle testing was conducted on chassis dynamometers over the US Environmental Protection Agency Federal Test Procedure, Highway Fuel Economy Test and US06 using RCCI combustion with commercially available gasoline and ultra-low sulphur diesel. Fuel economy and emissions data were recorded over the specified test cycles. Testing revealed that engine-out emissions were similar to steady-state dynamometer engine testing. However, tailpipe-out emissions saw a reduction of HC and CO during the HWFET of 98.5%. Fuel economy was lower than expected due to the higher drivetrain losses of the series hybrid drivetrain. Finally, simulated changes to the drivetrain showed that it may be possible to increase fuel economy significantly, while meeting EPA emissions standards.

Development of Near Optimal Rule-Based Control for Plug-In Hybrid Electric Vehicles Taking into Account Drivetrain Component Losses

A near-optimal rule-based mode control (RBC) strategy was proposed for a target plug-in hybrid electric vehicle (PHEV) taking into account the drivetrain losses. Individual loss models were developed for drivetrain components including the gears, planetary gear (PG), bearings, and oil pump, based on experimental data and mathematical governing equations. Also, a loss model for the power electronic system was constructed, including loss from the motor-generator while rotating in the unloaded state. To evaluate the effect of the drivetrain losses on the operating mode control strategy, backward simulations were performed using dynamic programming (DP). DP selects the operating mode, which provides the highest efficiency for given driving conditions. It was found that the operating mode selection changes when drivetrain losses are included, depending on driving conditions. An operating mode schedule was developed with respect to the wheel power and vehicle speed, and based on the operating mode schedule, a RBC was obtained, which can be implemented in an on-line application. To evaluate the performance of the RBC, a forward simulator was constructed for the target PHEV. The simulation results show near-optimal performance of the RBC compared with dynamic-programming-based mode control in terms of the mode operation time and fuel economy. The RBC developed with drivetrain losses taken into account showed a 4%–5% improvement of the fuel economy over a similar RBC, which neglected the drivetrain losses.

Reliability of power meter calibration by mathematical modelling of treadmill cycling

New power meters that are installed on various parts of the bike entered the market recently. Calibration of power meters is essential to ensure correct power output readings for testing and training. The use of a dynamic calibration rig was proposed as the preferred method to calibrate cycle ergometers (Woods et al., 1994: International Journal of Sports Medicine, 15(4), 168-171). While this works for power meters that measure power output after its transmission through the crank axle, it is not suitable for systems installed on the pedals or the crank arm (e.g. Garmin Vector, KA©o Power, Stages, Rotor Power). Therefore, we want to propose a new method to dynamically calibrate all available power meters. The purpose of our study was to quantify the typical error of this method used to assess load characteristics of power meters. Thirty power meters (14 SRM, 8 Powertap, 5 Quarq, 3 Garmin Vector) mainly used by cyclists of the Swiss national mountain bike team were analysed. Each cyclist rode his own bike equipped with his power meter on a motorized treadmill (Poma, DA¼rrrA¶hrsdorf-Dittersbach, Germany), after executing all calibration procedures according to the manufacturer. Cyclists rode with a velocity v = 3.5 m s-1 at an inclination of I±1 = 1° and I±2 = 7°. These corresponded to power demands of approximately 1 W kg-1 and 5 W kg-1, respectively. Power output measurements were averaged over 1 min for both inclinations. The total mass m of the cyclist, his equipment and bike was measured on a calibrated scale (Model 861, Seca, Reinach, Switzerland). To eliminate any contribution of rolling or aerodynamic resistance, the difference in power output between the two inclinations was calculated as I”P = m ∙ g ∙ v ∙ (sinI±2 – sinI±1). The ratio between the measured difference and that calculated by the mathematical model was defined as the load characteristic of the power meter. A value of 1 indicates perfect agreement between the measurement and the model. The procedure was performed twice. The typical error of measurement and its 95% confidence interval for the load characteristic was calculated from the 30 repeated trials (Hopkins, 2000: Sports Medicine, 30(1), 1-15). The typical error for the load characteristic was 1.5% with a 95% confidence interval of 1.1% to 1.9%. The change in the mean from trial 1 to trial 2 was 0.1% with a 95% confidence interval of -0.7% to 0.9%. The typical error of 1.5% demonstrates a high reliability of the method used to assess the load characteristic of a power meter, which can easily be enhanced by performing multiple trials. The value for a convenient triple measurement follows as 1.5% / 31/2 = 0.9% (Hopkins, 2000). The typical error presented here is comparable to the reliability reported for the calibration with a dynamic calibration rig (Woods et al., 1994). Our calibration method is easy to administer, time efficient and independent of the power meter system, rolling resistance or cyclist riding style. Even though the method does not assess absolute power output readings, it detects systematic measurement error. To further evaluate the load characteristic, an assumption concerning the drivetrain loss is necessary. After personal communication with J. Smith (www.friction-facts.com, December 6, 2013), we assume a drivetrain loss of 2% in power output difference scores. A valid system located on the crank would therefore measure a 2% higher difference in power output than predicted by the mathematical model. We conclude, that calibrating power meters by mathematical modelling of treadmill cycling is highly reliable and convenient.

Drivetrain Energy Distribution and Losses from Fuel to Wheel

Drivetrain Energy Distribution and Losses from Fuel to Wheel

Lower carbon cars by reducing dissipation in hydrogen hybrids

Fossil fuel is the major source of energy for all forms of motor vehicle, with gasoline and diesel fuels dominating our personal transport. Although biofuels have been used to inject some renewable energy into the transport system, imports of oil and gas to Europe, the USA and Japan continue to rise. A move to reduce energy consumption and carbon emissions by driving more efficient vehicles is therefore necessary. This paper considers a shift to reduced friction hydrogen electric vehicles that give three major benefits: (i) sourcing hydrogen from low carbon sources like wind, biomass, nuclear and solar; (ii) using an electric drivetrain to minimize energy conversion to heat; and (iii) reducing resistances to motion to give lower energy requirements for traction. This energy dissipation due to friction proves to be a complex mixture of tyre losses, brake adhesion, wind resistance, fuel conversion inefficiency, motor resistance, drivetrain losses, auxiliary power consumption and so on. By considering the addition of many loss terms, it is shown that the energy dissipation in fuel cell-powered vehicles resolves into a linear function of vehicle weight. Copyright , Oxford University Press.

CVT ratio control with consideration of CVT system loss

A modified CVT ratio map is proposed to obtain the improved fuel economy for a metal belt CVT. Since the CVT system loss, which occupies most of the drivetrain loss, depends on the engine speed, input torque, primary and secondary actuator pressure, a modified CVT ratio map is produced to realize the highest engine-CVT overall efficiency through the consideration of CVT system loss. The modified CVT ratio map is constructed with respect to the demanded vehicle power and present vehicle speed based on the steady state CVT system loss. Using the modified CVT ratio map, performance simulations are carried out using the dynamic models of the CVT powertrain. The simulation results indicate that the modified CVT ratio control provides improved engine-CVT overall system efficiency, and improves the fuel economy of the federal urban driving schedule by 4.9 percent.

Set values for a power-split hybrid electric vehicle through numerical optimisation

This paper deals with the determination of set values for the real-time control of a power-split Hybrid Electric Vehicle (HEV). Different programming problems are formulated for the operating modes 'hybrid propulsion', 'electrical propulsion' and 'regenerative braking'. Numerically robust solution procedures are developed and applied to these problems. The resulting set values for the power plants are stored in look up tables and embedded into the vehicle controller. It is shown that the model of the drivetrain losses inherent in the programming problems influences the fuel consumption a great deal. Numerical computations reveal which of the losses influence the fuel consumption most. Furthermore, a way of circumventing a detailed description of the mechanical gearbox losses is derived from a physical understanding of the energy flow through the transmission. The considerations are not restricted to a specific drivetrain, but are to a great extent generally applicable to hybrid electric vehicles of the power-split type.

Design Study of a 375 kW Helicopter Transmission with Split-Torque Epicyclic and Bevel Drive Stages

A novel drive train based on a simple epicyclic gear that drives a bevel combining gear through counter-rotating pinions is developed into a main gearbox for a helicopter powered by a single engine. A design with an overall speed ratio of 17.6 : 1 is compared with an advanced technology version of a production transmission. The new design, based on an integral main shaft and bevel gear, has a dry weight of 46 kg and offers a 24 per cent reduction in weight while remaining competitive in respect of drive train losses and totals of gears and bearings.

A Lightweight Split-Torque Transmission for a 330 KW Helicopter

A simple split-torque gear train is used as the main rotor transmission of a single-engine helicopter. Overall speed reduction ratio achieved is 103:1 between the engine at a nominal 36 000 rev/min and the main rotor at 350 rev/min. This ratio is generated from three stages of fixed-axis gear trains containing only eight gears. Alternative configurations are outlined and discussed. Comparison with a current production design shows the split torque arrangement offers reductions in weight, height, and drive train losses. A low total of gears and bearings offers the potential for improved reliability.