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This paper presents a new application of a vehicle on-board battery charger utilizing high frequency Silicon Carbide (SiC) power devices. SiC is one of the most promising alternatives to Silicon (Si) for power semiconductor devices due to its superior material characteristics such as lower on-state resistance, higher junction temperature, and higher switching frequency. An on-board charger prototype is developed demonstrating these advantages and a peak system efficiency of 95% is measured while operating with a switching frequency of 250 kHz. A maximum output power of 6.06 kW results in a gravimetric power density of 3.8 W/kg and a volumetric power density of 5.0 kW/L, which are about 10 times the densities compared with the current Prius Plug-In Si charger. SiC technology is indispensable to eco-friendly PHV/EV development.

A prototype power control unit (PCU) was manufactured using silicon carbide (SiC) power semiconductors (diodes and transistors), which have low power loss when switching on and off. This PCU was installed in a hybrid vehicle (HV) and driven on a test course and chassis dynamometer. The test results confirmed a fuel efficiency improvement of about 5 percent.

An obstacle recognition algorithm for the Pre-Crash Safety system has been newly developed with a stereo vision system and a millimeter wave radar with additional functions. This algorithm uses the merits of both the millimeter wave radar and the stereo vision system, and has two main features. One feature utilizes the merits of the stereo vision system detection with the detection results from the millimeter wave radar allowing for a more detailed horizontal position and width of the obstacle. This enables the equipment to operate at an earlier stage according to how well the relationship between the vehicle and the obstacle is understood. Another feature fuses detection from the millimeter wave radar and the stereo vision system. This system has succeeded in enhancing the detection performance of pedestrians who have been more difficult to detect than reflective objects such as cars.

Introducing effective technologies to reduce carbon emissions in the transport sector is a critical issue for automotive manufacturers to contribute to sustainable development. Unlike the plug-in electric vehicles (PEVs), whose effectiveness is dependent on the carbon intensity of grid electricity, the solar hybrid vehicle (SHV) can be an alternative electric vehicle because of its off-grid, zero-emission electric technology. Its usability is also advantageous because it does not require manual charging by the users. This study aims at evaluating the economic, environmental, and usability benefits of SHV by comparing it with other types of vehicles including PEVs. By setting cost and energy efficiency on the basis of the assumed technology level in 2030, annual cost and annual CO2 emissions of each vehicle are calculated using the daily mileage pattern obtained from a user survey of 5,000 people in Japan and the daily radiation data for each corresponding user.

In recent years, automakers have been developing various types of environmentally friendly vehicles such as hybrid (HV), plug-in hybrid (PHV), electric (EV), and fuel cell (FCV) vehicles to help reduce greenhouse gas (GHG) emissions. However, there are few commercial solar vehicles on the market. One of the reasons why automakers have not focused attention on this area is because the benefits of installing solar modules on vehicles under real conditions are unclear. There are two difficulties in measuring the benefits of installing solar modules on vehicles: (1) vehicles travel under various conditions of sunlight exposure and (2) sunlight exposure conditions differ in each region. To address these problems, an analysis was performed based on an internet survey of 5,000 people and publically available meteorological data from 48 observation stations in Japan.

In 2007, researchers at the Massachusetts Institute of Technology successfully completed a Wireless Power Transfer (WPT) experiment. Ever since, interest in WPT has been growing. At Toyota, we have been developing the underlying technology of a WPT system. Simultaneously we have been working with regulatory committees to create a standard for WPT. In particular, there are concerns that WPT’s radiated emissions could cause harm to humans and the neighboring electronic equipment. There are many challenges that need to be overcome, but a key concern is understanding WPT’s electromagnetic compatibility (EMI: Electro-Magnetic Interference and EMF: Electro-Magnetic Field). In this paper, we show the technical issues, the evaluation method, and the development status of EMI and EMF on PHVs/EVs when using WPT. For Electromagnetic interference (EMI) performance, we investigated both an open area test site and an electromagnetic anechoic chamber as evaluation environments.

There is ever increasing interest in the issues of fossil fuel depletion, global warming, due to increased atmospheric CO2, and air pollution, all of which are due in some extent to transportation, including automobiles. Hybrid Vehicles (HVs), whose performance and usage are equivalent to existing conventional vehicles, attract lots of attention and have started to come into wider use. Meanwhile, EVs have been considered by many as the best solution for the issues mentioned above. But the technical difficulty of battery energy density is an obstruction to successful implementation. Currently the Plug-in HV (PHEV), which combines the advantages of HV and EV, is being considered as one promising solution. PHEVs can be categorized into two types, according to operating modes. The first uses battery stored energy initially, only stating the internal combustion engine when the battery is depleted. This we call the All Electric Range (AER) system.

In this paper, we will introduce a stereo vision system developed as a sensor for a vehicle's front monitor. This system consists of three parts; namely, a stereo camera that collects video images of the forward view of the vehicle, a stereo ECU that processes its output image, and a near-infrared floodlight for illuminating the front at night. We were able to develop an obstacle detection function for the Pre-Crash Safety System and also a traffic lane detection function for a Lane-Keeping Assist System. Especially in regard to the obstacle detection function, we were able to achieve real-time processing of the disparity image calculations that had formerly required long processing times by using two types of recently developed LSIs.

Given a forecast of speed and load demands during a trip, a hybrid powertrain power-split Trajectory Optimization Problem (TOP) can be solved to optimize fuel consumption. This can be done on desktop to set performance benchmarks; however, it has been believed that the TOP could not be solved in real-time and is not a realizable controller. As such, several approximations of the TOP have been made in the interest of obtaining a real-time near-optimal controller, for example, Equivalent Consumption Minimization Strategies (ECMS) and their adaptive counterparts. These strategies decide on the power-split by, at each sampled time instant, minimizing a Horizon-0 (without predicting forward in time) composite function of fuel consumption and equivalent battery energy. The fuel economy that results from these strategies is highly sensitive to the calibration of the associated equivalence factor, and furthermore, must be chosen differently for different drive cycles.

Toyota Safety Sense is a safety system package developed to help drivers avoid accident types with a high frequency of occurrence. This paper deals with pre-collision system which forms the core of Toyota Safety Sense, especially Toyota Safety Sense P which uses a combined sensor configuration consisting of a monocular camera paired with millimeter wave radar, in order to achieve both high recognition performance and reliability. The use of a wide-angle monocular camera, millimeter wave radar integrated in the front grill emblem, and a collision determination algorithm for pedestrian targets enabled the development of a pre-collision system comprising detection capability of crossing pedestrians. Toyota has developed warning and pre-collision brake assist for driver to assist in avoiding a collision effectively; In addition, Pre-collision brake has achieved high level of performance for the drivers who cannot avoid a collision.

The increase in automobile accidents has heightened the awareness of safety in the general public, and serious safety measures have been pushed forward in various countries. Although those efforts have achieved a certain level of success, more effective methods are needed to cope with further increases of automobile ownership.Besides the collision safety, measures that prevent accidents or reduce the possibility of accidents will now be necessary to reduce the number of injuries.Here, we will present the current development status and issues for an obstacle recognition system that reduces the likelihood of accidents by utilizing radars and image sensors.

In recent years, attention is being given to 42V power supply technology for solving the problem of increased power demand in vehicles. Since 2001, Toyota Motor Corporation has been marketing a mild hybrid system (THS-M) in order to further improve fuel economy and reduce emissions; this system requires both 42V and 14V power sources. The THS-M system consists of a 42V motor generator (M/G) connected to the engine crankshaft with a belt; an inverter; a 36V battery; a DC/DC converter for stepping down the 42V power supply to a conventional 12V battery; and high-power related electrical components. These components require additional costs, which must be reduced in order to increase the sales volume of THS-M vehicles. We have devised a method to eliminate the conventional DC/DC converter from the THS-M, and as a result we have developed a new, revolutionary power conversion system (multi-function inverter).

Toyota has been introducing several hybrid vehicles (HV) since 1997 as a countermeasure to the concerns raised by automobile, like CO2 reduction, energy security, and pollutant emission reduction in urban areas. Plug in hybrid Vehicle (PHV) uses electric energy from grid rather than fuel for most short trips and therefore presents a next step forward towards an even more effective solution for these concerns. For longer trips, the PHV works as a conventional hybrid vehicle, providing all the benefits of Toyota full hybrid technology, such as low fuel consumption, user-friendliness and long cruising range. This paper describes a newly developed plug-in hybrid system and its vehicle performance. This system uses a Li-ion battery with high energy density and has an EV-range within usual trip length without sacrificing cabin space.

To adapt to Battery Electric Vehicle (BEV) integration, the significance of protective designs for battery packs against ground impact caused by road debris is very high, and there is also a keen interest in the feasibility assessment technique using Computer-Aided Engineering (CAE) tools for prototype-free evaluations. However, the challenge lies in obtaining real-world empirical data to verify the accuracy of the predictive CAE model. Collecting real-world data using actual battery pack can be time-consuming, costly, and accurately ascertaining the precise direction, magnitude, and location of the force applied from the road to the battery pack poses a challenging task. Therefore, in this study, we developed a methodology using machine learning, specifically Gaussian process regression (GPR), to perform inverse analysis of the direction, magnitude, and location of vehicle-road contact forces during rough road conditions.

Reducing the loss of the power control unit (PCU) in a hybrid vehicle (HV) is an important part of improving HV fuel efficiency. Furthermore the loss of power devices (insulated gate bipolar transistors (IGBTs) and diodes) used in the PCU must be reduced since this amounts to approximately 20% of the total electrical loss in an HV. One of the issues for reducing loss is the trade-off relationship with reducing voltage surge. To restrict voltage surge, it is necessary to slow down the switching speed of the IGBT. In contrast, the loss reduction requires the high speed switching. One widely known method to improve this trade-off relationship is to increase the gate voltage in two stages. However, accurate and high-speed operation of the IGBT gate control circuit is difficult to accomplish. This research clarifies a better condition of the two-stage control and designed a circuit that improves this trade-off relationship by increasing the speed of feedback control.

High-pressure metal hydride (MH) tank has been designed based on a 35 MPa cylinder vessel. The heat exchanger module is integrated into the tank. Its advantage over high-pressure cylinder vessels is its large hydrogen storage capacity, for example 9.5 kg with a tank volume of 180 L by Ti25Cr50V20Mo5 alloy. Cruising range is about 900 km, over 3 times longer than that of a 35 MPa cylinder vessel system with the same volume. The hydrogen-charging rate of this system is equal to the 35 MPa cylinders without any external cooling facility. And release of hydrogen at 243 K is enabled due to the use of hydrogen-absorbing alloy with high-dissociation pressure, for example Ti35Cr34Mn31 alloy.

Recently, the development of advanced automotive technology for excellent safety and convenience has become more active. Efforts have focused on the development of active safety technology. Pre-Crash Systems, such as passenger protection systems activated before a collision or collision speed reduction system, which are categorized between active safety systems and passive safety systems, have been a subject of focus. In such systems, surround sensing technology to predict a collision is the key issue. We developed an electronically scanning millimeter-wave (MMW) RADAR, which uses Digital Beam Forming (DBF) technology, as one of the first in the world for automotive applications.

It is necessary for us to reduce CO2 emissions in order to hold down global warming which is advancing year by year. Toyota Motor Corporation believes that not only the introduction of BEVs but also the sale of the hybrid vehicles must spread in order to achieve the necessary CO2 reduction. Therefore, we planned to improve the attractiveness of future hybrid vehicles. Prius has always made full use of hybrid technologies and leading to significant CO2 reduction. Toyota Motor Corporation has developed a 2.0L hybrid system for the new Prius. We built the system which could achieve a comfortable drive along following the customer’s intention while improving the fuel economy more than a conventional system. The engine improves on both output and thermal efficiency. The transaxle decreases mechanical loss by downsizing the differential, and adoption of low viscosity oil.

Toyota introduced the first generation Prius in 1997. The vehicle was conceived, designed and launched as a dedicated, mass-produced global hybrid vehicle platform, the first of its kind. The introduction of the 2nd and 3rd generation Prius (2003, 2009) saw vehicles with significantly improved performance, including fuel efficiency. The Prius Alpha (Japan/EU), launched in 2011, represented Toyota first foray with Li-ion battery in a strong hybrid configuration. For the Prius Alpha, the adoption of a compact Li-ion battery resulted in sufficient cabin space to allow a 3rd row of seats while maintaining high fuel efficiency. Before and after the launch of the Prius Alpha, an extensive list of tests was performed on the Li-ion battery pack, including electrical, electrochemical, mechanical, and safety. The evaluations were performed in the lab, in the field (demonstration fleets) and by acquiring vehicles used by customers.

For energy saving and global warming prevention, Toyota has developed Toyota Hybrid System (THS) for mass-produced passenger cars, which achieves drastic improvement in fuel efficiency and reduction in exhaust emissions compared to conventional gasoline engine cars. The THS has two motive power sources which engage depending on driving conditions. It's power is supplied either from an engine (controlled by the engine ECU) or an electric motor (controlled by the motor ECU) which is powered by a high-voltage battery (monitored by the battery ECU). These ECUs are controlled by a hybrid ECU. Each ECU has been developed with a fail-safe system in mind, to ensure driver safety in case of vehicle breakdowns. Among these ECUs, this paper reports particularly on the newly introduced ECUs: hybrid ECU and battery ECU. In the development of these ECUs, special attention was focused on fail-safe performance.