Page - 14 - in Hybrid Electric Vehicles

5. Architecture review of hybrid construction and agricultural machinery Manufacturers, governments, and researchers have been paying increasing attention to hybrid power train technology toward decreasing the high fuel consumption rate of con- struction machinery [17]. Hybrid wheel loaders, excavators, and telehandlers have particu- larly shown significant progress in this regard [88, 89]. With hybrid work vehicles attracting more attention, power train configurations, energy management strategies, and energy stor- age devices have also been increasingly reported in the literature [73, 90–92]. Both research- ers and manufacturers have approached studies of the hybrid power system applications, energy regeneration systems, and architectural challenges of construction machinery quali- tatively but not systematically and quantitatively. A first review of an electric hybrid HCM was presented in 2010 [107]. More recently, a specific review of a wheel loader and an excava- tor [108] was carried out, and another work in the field of high-voltage hybrid electric trac- tors [109] was published. Hitachi successfully launched the first hybrid loader in 2003 [90], and Komatsu developed the first commercial hybrid excavator in 2008 [93]. Komatsu devel- oped the HB205-1 and HB215LC-1 hybrid electric excavators, which are capable of recovering energy during the excavator slewing motion and of storing this energy in ultra-capacitors. Earth-moving machinery manufacturers have developed some diesel-electric or even hybrid- electric models . Johnson et al. [96] compared the emissions of a Caterpillar D7E diesel-electric bulldozer with its conventional counterpart [95]. Over the last years, there has been increas- ing interest in tractor and agricultural machinery electrification [96–99]. A number of trac- tor and agricultural machinery manufacturers have developed some diesel-electric or even hybrid-electric prototypes [20, 49, 100–102]. Recently, the Agricultural Industry Electronics Foundation started working on a standard for compatible electric power interfacing between agricultural tractors and implements [103], including, among others, the John Deere 7430/7530 E-Premium and 6210RE electric tractors [104] and the Belarus 3023 diesel-electric tractor [105]. Among telehandler vehicles, the TF 40.7 Hybrid telescopic handler proposed by Merlo [106]. Thus, it is necessary to study the various types of power train configurations of hybrid wheel loaders and excavators to better understand their construction features. The power require- ment has different working cycles depending on the applications. Many construction machin- ery manufacturers and researchers have studied hybrid wheel loaders to effectively use the braking energy and operate the engine within its high-efficiency range [110–113]. According to the classification of hybrid vehicles in the automotive field, there are three main design options for hybrid wheel loader power trains: series, parallel, and series-parallel. In the lit- erature review, the proposed architecture is mainly described, but no attempt at classification and comparison is made. It is not easy to find data sheets on the different vehicles because most of them are still at the prototype level. The comparison first outlines the architectures of the hybrid work vehicle solutions developed by the main manufacturers, as shown in Table 3. Figure 6 shows the series hybrid configuration of a wheel loader. As in the configuration of a hybrid vehicle, classic engine series ICE directly drives the electric generator, the electricity so generated is used to control the electric motor connected to the driveline. The advantage of a series hybrid wheel loader is the greater simplicity. In addition the engine ICE, being decou- pled from the wheels, it can be used at a fixed point in the conditions of greater efficiency. Hybrid Electric Vehicles14