# Hybrid Power System Design for Multifunctional Mini-Loader Vehicles
## 1 Introduction  
Climate change-related disasters caused by the greenhouse effect, in terms both of quantity and intensity, have been increasing year on year. Therefore, disaster relief has become an important issue. In order to operate conveniently in the disaster scene, existing mini machines are with few functions and need to be improved, mainly for detecting signs of life or surveying disaster sites. However, mini-loader vehicles, which are used in agricultural operations have the potential to be refitted as multi-purpose disaster relief machines [1]. For example, the mini-loader (C85 Series, CORMIDI, U.S.) can be used as a tool vehicle for disaster relief, transporting goods, and excavation operations by consuming gasoline as fuel. The small size design not only allows it to enter a narrow space for operation, but also meets the needs of excavation and transportation of goods. In addition, a multifunctional loader (HS1100, Hinowa SpA, Nogara, Italy) is developed which allows operators to replace operation equipment quickly and easily in a single vehicle, thus meeting the needs of diverse operation situations, such as digging, transportation, cargo lifting, and cement mixing. The power chassis uses the internal combustion engine (ICE). Replacement modules are provided as tools to meet the needs of users and expands the operation category and scope of mini vehicles. Another commercial loader (CINGO, MERLO, Italy) strives to satisfy consumers' requirements for a single vehicle with more suitable worktools, such as sweeping, watering, mowing, and snow removal. This vehicle divides the body into two parts: the power platform and tools. The power platform uses a 33 hp ICE system to allow the platform to withstand greater loads, and the tools can perform the four functions described above are also included in the tools. These conventional mini-loader vehicles are driven by ICE, and the concept of hybrid powers has not yet been introduced. However, hybrid vehicles can reduce greenhouse gas emissions and increase the total amount of available energy [2; 3; 4]. In addition, there are many advantages to electriying the loader vehicles of ICE. Several reports have revealed that improvements in the electro-hydraulic system have saved energy. [PERSON] et al. [5] have analyzed the possible energy saving of a hybrid hydraulic excavator under different operating conditions. [PERSON] et al. [6] constructed a new control mode with an excavator equipped with a load sensing hydraulic system, which saves 15% fuel. [PERSON] et al. [7] proposed an integrated drive and energy recuperation system based on a three-chamber hydraulic cylinder. This design can save 50% energy consumption and 64% of peak power. Furthermore, the more flexible control strategy for power strain systems has enhanced energy efficiency. For example, [PERSON] et al. [8] developed a novel electro-hydraulic control system to integrate into recovery and regeneration devices. [PERSON] et al. [9] discussed the boom energy regeneration technology for hydraulic construction machinery. [PERSON] et al. [10] investigated the control strategy of the power train system in the hybrid hydraulic excavators. In particular, the motor can also be served as a power generator that regenerated the potential energy and significantly enhanced energy efficiency [11; 12; 13; 14; 15]. At present, even though the designs of hybrid power machinery have been developed, which can be reviewed in academic papers [16; 17; 18; 19], in the market, only large-scale machines have products with gas-electric hybrid power systems. The large-scale dozer (D7E, Caterpillar, Peoria, IL, USA) is equipped with a diesel-electric hybrid power system. The output of the flywheel is 238 hp and the machine has a longer operating time than general dozers. The excavator (ZH200, Hitachi, Tokyo, Japan) is equipped with a diesel-electric hybrid power system. The output of the flywheel is 154 hp and can also provide a longer operating time.