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A hydraulic hybrid vehicle with the self-adaptive system is proposed. The mode-switching between the driving mode and the hydraulic regenerative braking mode is realised by the pressure cross-feedback control. Extensive simulated and tested results are presented. The control parameters are reduced and the energy efficiency can be increased by the self-adaptive system. The mode-switching response is fast. The response time can be adjusted by changing the controlling spool diameter of the hydraulic operated check valve in the self-adaptive system. The closing of the valve becomes faster with a smaller controlling spool diameter. The hydraulic regenerative braking mode can be achieved by changing the hydraulic transformer controlled angle. Compared with the convention electric-hydraulic system, the self-adaptive system for the hydraulic hybrid vehicle mode-switching has a higher reliability and a lower cost. The efficiency of the hydraulic regenerative braking is also increased. [ABSTRACT FROM AUTHOR]

Abstract: Along with the shortage of energy and the increasingly serious pollution of environment in cities, automobile industries all over the world are exploring and developing energy saving and clean automobile. Hydraulic hybrid vehicle has better potential in medium-size and large-size passenger vehicles than its electric counterparts. The key components’ sizes have remarkable influence on the vehicle performance and fuel economy, and an optimization process is needed to find the best design parameters for maximum fuel economy while satisfying the vehicle performance constraints. Multi-Objective optimization method based on adaptive simulated annealing genetic algorithm (ASAGA) is proposed to optimize the key components in HHV. In the objective function of the optimization, all the weighting factors can be set with different values according to different requirements. The optimal results show that the proposed method effectively distinguishes the key components’ optimal parameters’ position of HHV, enhances the performance and fuel consumption. [Copyright &y& Elsevier]

The development of fuel-efficient vehicles has increased along with the needs of consumers and the rise of environmental issues. Hybrid vehicles have become a popular alternative to conventional powertrains in the passenger vehicle market. Hydraulic hybrid vehicles have been applied to certain applications with clear benefits, such as high power density. To increase the base of academic knowledge, the energy characteristics of hydraulic hybrids were experimentally and theoretically studied for thermal management. First, measurement data for a series hydraulic hybrid system were collected by hardware in the loop test rig for different temperature conditions. The experimental results were compared for different thermal management conditions, thus showing the power consumption behaviors at different system temperatures. Also, a theoretical approach with thermodynamic properties was introduced for analyzing the energy characteristics of hydraulic hybrid systems. The theoretical results revealed possible explanations for the relationship between energy saving and thermal management for hydraulic hybrid systems. This study was worthy not only in that the experimental data itself worth as reference data for energy characteristics of hydraulic hybrid systems for thermal management, but also in that a novel theoretical approach for energy characteristics analysis was introduced, using energy and exergy analysis for the first time. • Energy characteristics of hydraulic hybrids were experimentally analyzed for different thermal management conditions. • A new method was suggested for system energy characteristics analysis by thermodynamic diagrams. • A method using energy and exergy analysis was introduced for hydraulic hybrids for the first time. [ABSTRACT FROM AUTHOR]

• Hydraulic driving unit designed for commercial vehicles with power analysis. • Braking control strategy considers braking safety needs and energy recovery. • Influence of working pressure and gas volume on energy recovery is analyzed. • Different vehicle load and load distributions are investigated. Hydraulic hybrid technologies improve the fuel economy of city-use medium duty vehicles by recovering braking energy and reusing it for driving, most notably vehicle launching. In this paper, a parametric design of hydraulic driving system for a medium duty truck is conducted based on its power demand in typical urban driving cycles. The braking control strategy is designed considering both the safety regulations and braking energy recovery rate. The proportional relationship of hydraulic pump/motor output torque and its working pressure is considered when designing the braking control strategy. The influence of the high pressure accumulator minimum working pressure and the corresponding gas volume at the minimum pressure on the braking energy recovery rate is analyzed. The simulation results show that the proposed hydraulic driving system and braking control strategy helps greatly increase the braking energy recovery rate. Besides, different vehicle mass and load distributions are investigated to analyze the regenerative braking effect on various loading conditions. [ABSTRACT FROM AUTHOR]