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To reduce carbon dioxide emissions, the use of vehicles operating on electrification technology, such as plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs) is rapidly increasing. A similar trend also exists in the field of heavy-duty vehicles, such as trucks and buses. When evaluating—via the certification test method—the fuel efficiency, electricity efficiency, and exhaust gas emission of heavy-duty vehicles that have many batteries, the powertrain, including the batteries, is modeled and investigated. However, such modeling is difficult because batteries deteriorate, and the ambient temperature fluctuates during vehicle operation. To resolve this issue, we developed a new evaluation method that enables real-time cooperative control of actual batteries and hardware-in-the-loop simulation (HILS).

Fuel consumption and exhaust gas emission regulations are being tightened around the world year by year. Electric vehicles are needed to reduce carbon dioxide emissions. Especially, Plug-in hybrid heavy-duty vehicles (PHEVs) are expected to become widespread. PHEVs enable all-electric modes, as well as hybrid modes, using both engines and electric motors, but the control system significantly affects the characteristics of fuel consumption and gas emission. In this study, we used new testing machine (we call extended HILS) to analyze the fuel consumption and gas emission for different plug-in hybrid control systems and investigated the optimal control method for PHEVs.

At interurban transportation, improvement of fuel economy of hybrid electric heavy-duty diesel vehicles, which assist drive-axle by using regeneration energy, is minimum, compared to heavy-duty diesel vehicles. One of the factors is that hybrid electric heavy-duty vehicles are not able to balance regeneration energy (input) and power energy (output) at high speed driving. One reason is not opportunity to operate of braking at high speed driving for the heavy-duty vehicle. In this research, we focus on the method used for the battery energy, and propose a new concept of hybrid electric system to efficiently utilize battery energy. That system consists of electrical booster for supercharging intake air into engine cylinder. We have confirmed the feasibility of the electric system of a new HEV concept by using the simulation I created.

Next-generation vehicles which include Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) are researched and expected to reduce CO2 emissions in the future. Generally, the main factor to support high efficiency of EV and HEV is the idle stop, motor assistance and regenerative braking. The vehicle mechanism of HEV is complex, compared with conventional internal combustion engine vehicle. Certification test method of gas emissions and fuel consumption is used driving mode, which is currently reflecting the typical driving conditions in the market. And driving mode of certification test is established focusing on the reproducibility of driving by conventional internal combustion engine vehicles. It is necessary to consider that the driving mode for the vehicle used regenerative energy is reflected correctly. And high accuracy certification test method for next generation HEVs is necessary in order to evaluate exhaust gas and fuel economy.

Around the world, fuel economy and emission regulations for vehicles have become increasingly stringent year by year. In Europe, the real driving emission (RDE) testing was introduced for evaluating the emission at driving the road-going vehicles after September 2017. In order to effiency produce the actual vehicles, Each automobile manufacturer introduce the “Hardware In the Loop Simulator” (HILS) and “Engine In the Loop Simulator” (which is called the EILS or the extended HILS [1, 2]), which is combined with HILS and an actual engine. However, if the driver model used in the vehicle simulation (HILS, extended HILS) does not correctly simulate actual human driving behaviors, the model vehicle performances will differ from the actual vehicle performance. The fuel economy and emission characteristics are affected by the differences of the driver model control logic during the execution of vehicle simulation.

Next-generation vehicles which include Electric Vehicles and Hybrid Electric Vehicles are studied and expected to reduce carbon dioxide emissions. The number of small delivery hybrid trucks has increased in the commercial vehicle class. The engine load of a commercial hybrid truck is reduced by using an electric motor. Fuel economy of the hybrid truck is improved with the assist. On the other hand, exhaust-gas temperature is decreased, and it has a negative effect on the purification performance of aftertreatment system. In this report, the fuel performance and emission gas characteristics of marketed small hybrid trucks were surveyed using the chassis dynamometer test system.

Next-generation vehicles which include Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) are researched and expected to reduce carbon dioxide (CO2) emissions in the future. In the national new-car sales in 2012 of Japan, the total sales of hybrid vehicles kept 26.5% share. In the field of passenger cars, this share was 29.7%. And, this share rose about four times compared to that of 2008 [1]. Also, small delivery hybrid trucks are increased in the commercial vehicle class. Fuel economy of hybrid trucks in the catalog specifications is relatively better than that of the diesel tracks which have no hybrid systems. Nevertheless, hybrid trucks' users report that advantages of fuel economy of hybrid trucks at the real traffic driving conditions are small.

From the perspective of improving the atmospheric environment, evaluating the fuel efficiency and exhaust gas emissions when using actual vehicles on real roads is necessary. Passenger vehicles apply RDE (real driving emission) test. However, unlike passenger vehicles, there are many types and models of heavy-duty vehicles; thus, evaluating all of these types using real driving emission tests is difficult. Therefore, we investigated the possibility of an alternative evaluation of heavy-duty vehicle based on a simulation method that uses a vehicle model for part of the evaluation. This alternative evaluation method is a combination of the “engine HILS (hardware-in-the-loop simulation)” method, developed in previous studies and can perform tests based on vehicle speed and driving wind that is reproduced in the engine bench to appropriately cool the engine and various devices.

Fuel consumption rate (fuel economy) and exhaust gas emission regulations are being tightened around the world year by year. In Europe, the real driving emission (RDE) method for evaluating exhaust gas emitted from road-going vehicles was introduced after September 2017 for new types of light/medium-duty vehicles, in addition to the chassis dynamometer test using the worldwide harmonized light vehicles test procedure (WLTP). Further, the worldwide harmonized heavy-duty certification (WHDC) method was introduced after 2016 as an exhaust gas emission test method for heavy-duty vehicles. In each evaluation, the tests of vehicles and engines are initiated from cold states. Heavy-duty hybrid vehicles are evaluated using the vehicle simulation method. For example, the power characteristics of a engine model is obtained during engine warm operation. Therefore, various performances during cold start cannot be precisely evaluated by using simulator.

In order to improve the fuel economy of the heavy duty trucks at a highway driving condition, the heavy duty hybrid trucks with new type of hybrid electric assist engine system were proposed at the previous report. The new system consists of a downsizing diesel engine with a two-stage charging structure, which has an electric supercharger with bypass circuit and a conventional turbocharger, the hybrid electric motor and the small-capacity battery. The electric power consumption of an electric supercharger is equivalent to the amount of the regeneration power produced during high-speed driving where the opportunity of the regeneration is small. In this report, an electric supercharger for the heavy duty hybrid truck was produced experimentally. First, the engine performance and exhaust emissions were investigated using the 4 cylinder diesel engine equipped with an electric supercharger.