Improving the Fuel Efficiency of Compact Wheel Loader With a Series Hydraulic Hybrid Powertrain

2020 ◽  
Vol 69 (10) ◽  
pp. 10700-10709
Author(s):  
Qunya Wen ◽  
Feng Wang ◽  
Bing Xu ◽  
Zongxuan Sun
Author(s):  
Qunya Wen ◽  
Feng Wang ◽  
Bing Xu ◽  
Zongxuan Sun

Abstract As an effective approach to improving the fuel economy of heavy duty vehicles, hydraulic hybrid has shown great potentials in off-road applications. Although the fuel economy improvement is achieved through different hybrid architectures (parallel, series and power split), the energy management strategy is still the key to hydraulic hybrid powertrain. Different optimization methods provide powerful tools for energy management strategy of hybrid powertrain. In this paper a power optimization method based on equivalent consumption minimization strategy has been proposed for a series hydraulic hybrid wheel loader. To show the fuel saving potential of the proposed strategy, the fuel consumption of the hydraulic hybrid wheel loader with equivalent consumption minimization strategy was investigated and compared with the system with a rule-based strategy. The parameter study of the equivalent consumption minimization strategy has also been conducted.


Author(s):  
Qi Zhang ◽  
Feng Wang ◽  
Bing Xu ◽  
Kim A. Stelson

Abstract Owing to its high power density, hydraulic hybrid is considered as an effective approach to reducing the fuel consumption of heavy duty vehicles. A gas-charged hydraulic accumulator serves as the power buffer, storing and releasing hydraulic power through gas. An accurate hydraulic accumulator model is crucial to predict its actual performance. There are two widely used accumulator models: isothermal and adiabatic models. Neither of these models are practical to reflect its real performance in the hydraulic hybrid system. Therefore, the influence of an accumulator model considering thermal hysteresis on a hydraulic hybrid wheel loader has been studied in this paper. The difference of three accumulator models (isothermal, adiabatic and energy balance) has been identified. A dynamic simulation model of the hydraulic hybrid wheel loader has been developed. The fuel consumptions of the hydraulic hybrid wheel loader with three accumulator models has been compared. The influence of heat transfer coefficient of the accumulator housing has also been studied.


Author(s):  
Qi Zhang ◽  
Feng Wang ◽  
Bing Xu ◽  
Zongxuan Sun

The hydraulic hybrid powertrain has great potential for reducing fuel consumption and emission of off-road vehicles. The energy management strategy is the key to hybrid powertrain and currently there are many well-developed strategies. Of which the Pontryagin’s minimum principle is of research interest since it is a global optimization method while less computational burden than dynamic programming. However, it requires full cycle information to calculate co-state value in the principle, making it not implementable. Therefore in this study an implementable Pontryagin’s minimum principle is proposed for a series hybrid wheel loader, where the optimal co-state value in the principle is trained through repetitive wheel loader duty cycle. The Pontryagin’s minimum principle formulations of hybrid wheel loader are developed. The online co-state training algorithm is presented. A dynamic simulation model of hybrid wheel loader is developed. The fuel consumption of hybrid wheel loader with proposed strategy is compared with dynamic programming strategy and rule-based strategy in wheel loader long and short loading cycles. Results show the fuel consumption with proposed strategy is close to dynamic programming result and is lower than rule-based strategy. Finally, the influence of pressure level of hybrid powertrain on vehicle fuel consumption is studied.


Author(s):  
Mikko Huova ◽  
Jyrki Tammisto ◽  
Matti Linjama ◽  
Jussi Tervonen

There is a potential for significant improvement on fuel efficiency of many mobile machines by using hybrid technology as the Diesel engines are often driven at very inefficient operating points in these applications. The load generated by the working hydraulics of a mobile machine is often rapidly changing and contains high peak powers compared to the mean power required. This paper studies three different hydraulic hybrids in a wheel loader application. The study is based on a measured sand-loading Y-cycle. In addition to the hybrid systems, a load sensing proportional valve based reference machine and a modified machine based on independent metering valves are analyzed. All five system alternatives are analyzed systematically to enable a comparison of their fuel efficiency. The study shows that the fuel consumption of the machine can be decreased up to 28 % in such load cycle by using a suitable hydraulic hybrid system.


Author(s):  
Qunya Wen ◽  
Feng Wang ◽  
Bing Xu

As an effective approach to improving the fuel economy of modern heavy-duty vehicles, hydraulic hybrids have shown great advantages in off-road vehicles. Wheel loader is one of the representative vehicles in off-road applications as they are usually designed for single and repetitive task such as loading material. In a typical short loading cycle, there are many accelerations and decelerations, showing great hybridization potentials. Therefore in this paper a series hydraulic hybrid powertrain has been proposed for compact wheel loader since its hydrostatic powertrain can be easily transformed to a series hydraulic hybrid with an additional hydraulic accumulator. The modeling and system design of the series hydraulic hybrid wheel loader have been presented. Three controllers have been designed for vehicle speed control, engine torque control and engine speed control respectively. A dynamic simulation model has been developed in MATLAB/Simulink. A rule-based energy management strategy (EMS) has been proposed for the series hydraulic hybrid wheel loader. Two different EMS schemes were investigated and compared through simulation studies.


Author(s):  
Timothy O. Deppen ◽  
Andrew G. Alleyne ◽  
Kim A. Stelson ◽  
Jonathan J. Meyer

In this paper, a model predictive control (MPC) approach is presented for solving the energy management problem in a parallel hydraulic hybrid vehicle. The hydraulic hybrid vehicle uses variable displacement pump/motors to transfer energy between the mechanical and hydraulic domains and a high pressure accumulator for energy storage. A model of the parallel hydraulic hybrid powertrain is presented which utilizes the Simscape/Simhydraulics toolboxes of Matlab. These toolboxes allow for a concise description of the relevant powertrain dynamics. The proposed MPC regulates the engine torque and pump/motor displacement in order to track a desired velocity profile while maintaining desired engine conditions. In addition, logic is applied to the MPC to prevent high frequency cycling of the engine. Simulation results demonstrate the capability of the proposed control strategy to track both a desired engine torque and vehicle velocity.


Author(s):  
Feng Wang ◽  
Mohd Azrin Mohd Zulkefli ◽  
Zongxuan Sun ◽  
Kim A. Stelson

Energy management strategies for a hydraulic hybrid wheel loader are studied in this paper. The architecture of the hydraulic hybrid wheel loader is first presented and the differences of the powertrain and the energy management system between on-road vehicles and wheel loaders are identified. Unlike the on-road vehicles where the engine only powers the drivetrain, the engine in a wheel loader powers both the drivetrain and the working hydraulic system. In a non-hybrid wheel loader, the two sub-systems interfere with each other since they share the same engine shaft. By using a power split drivetrain, it not only allows for optimal engine operation and regenerative braking, but also eliminates interferences between driving and working functions, which improve the productivity, fuel efficiency and operability of the wheel loader. An energy management strategy (EMS) based on dynamic programming (DP) is designed to optimize the operation of both the power split drivetrain and the working hydraulic system. A short loading cycle is selected as the duty cycle. The EMS based on DP is compared with a rule-based strategy through simulation.


Author(s):  
Fernando Tavares ◽  
Rajit Johri ◽  
Zoran Filipi

The simulation-based investigation of the variable displacement engine is motivated by a desire to enable unthrottled operation at part load, and hence eliminate pumping losses. The mechanism modeled in this work is derived from a Hefley engine concept. Other salient features of the proposed engine are turbocharging and cylinder deactivation. The cylinder deactivation combined with variable displacement further expands the range of unthrottled operation, while turbocharging increases the power density of the engine and allows downsizing without the loss of performance. While the proposed variable displacement turbocharged engine (VDTCE) concept enables operations in a very wide range, running near idle is impractical. Therefore, the VDTCE is integrated with a hybrid powertrain allowing flexibility in operating the engine, elimination of idling and mitigation of possible issues with engine transients and mode transitions. The engine model is developed in AMESim using physical principles and 1-D gas dynamics. A predictive model of the power-split hydraulic hybrid driveline is created in SIMULINK, thus facilitating integration with the engine. The integrated simulation tool is utilized to address design and control issues, before determining the fuel economy potential of the powertrain comprising a VDTCE engine and a hydraulic hybrid driveline.


Author(s):  
Katharina Baer ◽  
Liselott Ericson ◽  
Petter Krus

Amongst the hybrid vehicle propulsion solutions aiming to improve fuel efficiency, hybrid electric solutions currently receive most attention, especially on the market. However, hydraulic hybrids are an interesting alternative, especially for heavier vehicles due to higher power density which is beneficial if higher masses are moved. As a step towards a comprehensive design framework to compare several possible hydraulic hybrid architectures for a specified application and usage profile, the model of a series hydraulic hybrid vehicle was previously introduced and initially studied concerning component sizing for an exemplary light-duty vehicle in urban traffic. The vehicle is modeled in the Hopsan simulation tool. A comparably straight-forward engine management is used for the vehicle control; both pump and engine controls are based on the hydraulic accumulator’s state-of-charge. The model is developed further with respect to the accumulator component model. Based on that, the influence of several system and component parameters, such as maximum system pressure and engine characteristics, as well as controller parameters on the vehicle’s performance is analyzed. The goal is to allow for more understanding of the system’s characteristics to facilitate future optimization of the system.


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