Optimal Power Management of Hydraulic Hybrid Mobile Machines—Part I: Theoretical Studies, Modeling and Simulation
Optimal Power Management of Hydraulic Hybrid Mobile Machines—Part I: Theoretical Studies, Modeling and Simulation
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DOI：
10.1115/1.4032742
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发表时间：
2016-05
影响因子：
1.7
通讯作者：
R. Hippalgaonkar;M. Ivantysynova
中科院分区：
文献类型：
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作者：
R. Hippalgaonkar;M. Ivantysynova
最近对提高系统效率和减少系统排放的需求推动了液压系统结构的改进以及移动多执行器机械所采用的系统监控策略。阀控(VC)结构已经使用了几十年，在系统效率方面有了适度的改进。此外，最近提出了位移控制(DC)驱动等无油门概念，并成功地在许多不同尺寸的原型(轮式装载机、挖掘机和滑动转向装载机)上证明了效率的提高。原始设备制造商(OEM)最近也在一些型号的挖掘机上部署了用于能量回收的电动或液压混合系统(用于单个执行器)与用于其余执行器的VC驱动的组合。作为这项工作的一部分，以前已经提出并在微型挖掘机上实现了将直流驱动与串联液压混合执行器相结合的摆动驱动。这种高效的直流驱动与液压混合动力配置相结合，与现代的VC驱动系统相比，可以大幅缩小发动机尺寸，并将效率提高50%以上。对于5t挖掘机应用，采用保守的、次优的监督控制，先前已经证明，与标准负载传感(LS)架构相比，使用50%缩小尺寸的发动机可节省50%以上的能源。通过接近最优的监督控制(或系统功率管理)实现最大系统效率的问题是一个理论上具有挑战性的问题，这项工作首次通过两部分的出版解决了直流液压混合动力机的这项工作。在第一部分中，概述了这个问题的理论方面，并通过对理论上最优的监督控制以及可实施的、基于规则的近最优监督控制策略的仿真支持，其中包括直流混合动力挖掘机的详细系统模型。在第二部分中，详细介绍了世界上第一台直流液压混合动力挖掘机的原型，以及第一部分提出的新型监控策略在机器上的实施情况。采用动态规划(DP)方法求解最优监控问题，并对可实施策略进行基准检验。重要的是，分析和识别了不同工作周期下DP获得的最优状态轨迹和控制历史的模式，并找到了不同工作周期内发动机转速和直流单元位移的共同模式。采用基于规则的策略来获得接近最优的系统效率，该策略的设计以最优模式为指导。结果表明，对于不同的循环，该策略以相同的控制发动机转速的规则来复制最优系统行为，但对于不同循环的串联式混合动力摆动传动的主机组，其控制规则是不同的。因此，在基于规则的方法的实际实现方面，操作员将被提供一族控制器，从中可以选择一种，以便在所有类型的循环操作下具有接近最优的系统行为。
Recent demands on improved system efficiency and reduced system emissions have driven improvements in hydraulic system architectures as well as system supervisory control strategies employed in mobile multi-actuator machinery. Valve-controlled (VC) architectures have been in use for several decades and have seen moderate improvements in terms of system efficiency. Further, throttle-less concepts such as displacement-controlled (DC) actuation have been recently proposed and successfully demonstrated efficiency improvements in numerous prototypes (wheel-loaders, excavators, and skid-steer loaders) of different sizes. The combination of electric or hydraulic hybrid systems for energy recovery (for a single actuator) with VC actuation for the rest of the actuators has also been recently deployed by original equipment manufacturers (OEMs) on some excavator models. The combination of DC actuation together with a series hydraulic hybrid actuator for the swing drive has been previously proposed and implemented as part of this work, on a mini-excavator. This combination of highly efficient DC actuation with hydraulic hybrid configuration allows drastic engine downsizing and efficiency improvements of more than 50% compared to modern-day VC-actuated systems. With a conservative, suboptimal supervisory control, it was previously demonstrated that over 50% energy savings with a 50% downsized engine over the standard load-sensing (LS) architecture for a 5-t excavator application. The problem of achieving maximum system efficiency through near-optimal supervisory control (or system power management) is a theoretically challenging problem, and has been tackled for the first time in this work for DC hydraulic hybrid machines, through a two-part publication. In Part I, the theoretical aspects of this problem are outlined, supported by simulations of the theoretically optimal supervisory control as well as an implementable, near-optimal rule-based supervisory control strategy that included a detailed system model of the DC hybrid hydraulic excavator. In Part II, the world's first prototype DC hydraulic hybrid excavator is detailed, together with machine implementation of the novel supervisory control strategy proposed in Part I. The main contributions of Part I are summarized below. Dynamic programming (DP) was employed to solve the optimal supervisory problem, and benchmark implementable strategies. Importantly, the patterns in optimal state trajectories and control histories obtained from DP were analyzed and identified for different working cycles, and a common pattern was found for engine speed and DC unit displacements across different working cycles. A rule-based strategy was employed to achieve near-optimal system efficiency, with the design of the strategy guided by optimal patterns. It was found that the strategy replicates optimal system behavior with the same rule for controlling engine speed for different cycles, but different rules for the primary unit (of the series-hybrid swing drive) for different cycles. Thus, in terms of practical implementation of a rule-based approach, the operator is to be provided with a family of controllers from which one can be chosen so as to have near-optimal system behavior under all kinds of cyclical operation.