Development of Audio System for TOYOTA "i-unit" Akira Motojima Masanobu Maeda Masami Ando Yoichi Yamaguchi Tadashi Imamura Shohei Yoshii Shigeki Kato Abstract At the EXPO 2005 AICHI, JAPAN, the single seater "i-unit," a future concept vehicle, was submitted to the Toyota Group Pavilion for display. This i-unit is loaded with a driving support system which utilizes various types of IT technology geared towards future societies. In this project, with the aim of a fusion of humans and vehicles, a human interface has been developed which, using sound, light and vibration, provides the driver with easy-to- understand information regarding driving support. FUJITSU TEN also cooperated in this audio system develop- ment. This document introduces i-unit audio system hardware. This introduction includes an outline of "audio con- tents" created with the aim of human interface enhancement, as well as an introduction regarding sound image control methods which are used to localize sound within a 360-degree circumference around the driver with two loudspeakers. 11 FUJITSU TEN TECHNICHAL JOURNAL 1. Introduction 3. Audio system 1 Introduction 3 Audio system At the EXPO 2005 AICHI, JAPAN, which began The following describes the aim for sound for the pur- being held as of March 25th of this year, TOYOTA pose of realizing IT technologies, as mentioned in chapter 2. GROUP submitted to the TOYOTA GROUP PAVILION ①Creation of pleasant audio space its developed "i-unit", a single seater concept vehicle for ・i-unit provides you with your own private, relaxing the future. space. i-unit is a vehicle which includes various types of tech- ②Information provision through situation-oriented nology for realizing concrete efforts directed toward sound future societies, and its audio system was developed with ・Perception is enhanced by providing information cooperation from FUJITSU TEN. This paper introduces i- through voice and operational sounds with a sense of unit's audio system and "audio contents" created in con- direction. junction with it. ・In a vehicle in which warning alarms sound for courses of direction that require attention, caution and advice is 2 Outline2. Outline of of i-unit provided which makes it difficult to miss important sounds. i-unit is a "Personal Mobility" that seeks to attain a In order to realize the target IT technology with pre- greater balance of meeting individuals' wishes to enjoy sent technology, as well as to realize the i-unit character- freedom of movement and excitement of driving, harmo- istic of "minimum size mobility", the least amount of hard- ny with society, and harmony with the Earth's natural ware was used in conducting software signal processing. environment. With the speaker system, 2 miniature speakers are set near the driver's ears, with signal processing helping to 2.1 Outline realize audio imaging control for the driver's surround- The outline of i-unit's concept, etc., is shown in Table 1 (1). ings and optional positioning. The audio system's hardware consists of "USB unit", 2.2 Major functions and features "power amp" and "speaker unit", which show the hard- Table 2 shows a list of major functions and features. ware configuration (system block) used in Figure 2. The following shows acoustic specifications for the purpose of 2.3 Vehicle development theme and IT technology realizing the aimed-after sound. The 3 development themes of i-unit are: Acoustic specifications "Meeting the needs of individuals" "Harmony with ・Frequency property: 300Hz to 20kHz society" "Harmony with the Earth's natural environment" ・Maximum acoustic pressure: 110dB (dummy head near Figure 1 summarizes IT technologies for the purpose of the ears) realizing each of those themes. ・Difference of left/right output: within ±3dB (dummy head, 1kHz) ・Degree of separation: 70dB or more (amp, USB) Table 1 Outline of i-unit Concept “Expanding Human Abilities” This union of driver and vehicle is intended to expand human abilities and possibilities. “Inspire the Individual” Movement expands our world by creating possibilities and encounters among Making a better world with mobility nature, society, people and culture. Movement brings us new sensations, Theme leading the way to a greater bond discoveries and acquaintances, enabling individuals to lead fuller lives and between people and the planet. cultivating a sense of belonging with the planet. The design, inspired by the leaf that converts sunlight into life energy, seeks to express the power Design Theme “The Leaf” of the unknown, the logic of living things and the simple beauty of waste-free functionality. Table 2 Characteristics and outline of i-unit Mobility with an The “i-unit” creates a seamless transformation between vehicle and human movement, minimizing Ultra Compact Size occupied space and energy consumption with its lightweight and ultra compact size. The i-unit has a compact size enabling the passenger to move among other people in an upright position in low Variable Positioning speed mode, and a low center of gravity that ensures stable handling when the vehicles reclines in high speed mode. Ease of Operation ①Drive Controller Drive-by-wire technology and intuitive handling enable the passenger to maneuver on-the-spot turns and drive at high speed at will. ②IT Controller A driver support information system uses sound, light and vibration to facilitate interactive communication. The driver support system features Intelligent Transport System (ITS) technology, which Toyota hopes to utilize Driver Support System for an accident-free society. The system permits efficient and safe autopilot driving in specially equipped lanes. A personalized recognition system can provide information and music, and body color can be “My-unit” customized, according to the individual’s preferences and emotions. Environmentally The body is built using environmentally friendly plant-based materials such as kenaf. Friendly Body Materials FUJITSU TEN TECH. J. NO.25(2005) 12 Development of Audio System for TOYOTA "i-unit" Making a better world with mobility Harmony with the Meeting the Harmony with Earth's natural needs of society individuals environment Environmentally Friendly Body Materials Freedom of Excitement of movement driving Mobility with an Open body Ultra Compact Size Variable Positioning Drive-by-wire The desire to move comfortably Harmony of transportation society “My-unit” Driver Support System Communication system Personal “My-unit” recognition system Driver monitor system Communication system IT Controller Customized body color Voice and sound system allow for intuitive Driver Support System Autopilot driving Observation surroundings Car-to-car communication system Fig.1 Outline of IT technology size, focus was put on both size and weight reduction. While conducting miniaturization at the parts level, the connector portion was eliminated through the use of a fly Imaging ECU Rear camera Left hand operation lead connector, enabling maximum lowering of overall Mike equipment Main height. As a result, it became possible to make installation Vehicle LED ECU Right hand ECU into a unique and compact vehicle. operation equipment controller 4.1.3 Reliability Audio contents USB unit FUJITSU TEN-coordinated audlo system Fig.2 System block diagram 4 Hardware4. Hardware outlineoutline This chapter explains about hardware units in the Fig.3 USB unit external features audio system. This unit shows the following efforts that were made 4.1 USB unit to secure reliability, which admittedly were unique in This section gives explanation regarding the USB both objects of development and conditions of use. unit, which converts digital signal to analog conversion ①Use within the EXPO venue (indoors) and outputs of audio contents in the main ECU. Evaluation is performed In response to wireless com- 4.1.1 Aim and outline munications used in the venue Development was made in aspiration for compactness ②Dealing with fluctuations in battery power (response and energy conservation. Digital voice sound output from to the electric automobile) the main ECU is input via the USB cable to the main Should audio circuits lock due to a major fluctuation unit, which converts that voice sound data to analog sig- in power supply from the main ECU, a mechanism is set nals and transmits it to the AMP unit. in place which restores audio output circuits by way of 4.1.2 Form unit internal reset circuits without having to reset the As the i-unit vehicle itself is a concept of ultra small entire system. FUJITSU TEN TECH. J. NO.25(2005) 13 FUJITSU TEN TECHNICHAL JOURNAL V5 V33 ①Output: 12 W or more compatible with 2 channel 5V stereo USBI/F REG GND (3V) 6MHz ②Size: 90 mm×80 mm×20 mm or less (50% of con- V33 V33 8P ventional models) CN USB-CODEC DAC I2S ③Noise reduction (S/N ratio, separation 70 dB or more) USB(+/-) (TAS1020) Analog L/R In order to realize the above size, it is necessary to V33 have high efficiency and miniaturization, and explanation will start from that point. I2C REG EEPROM (3V) 4.2.3 Miniaturization Due to the fact that this vehicle is unique and com- pact, there was a demand for all of the installed units to Fig.4 System block diagram of the USB unit be miniaturized as well. There were restrictions in partic- ular on unit height, and so the slim units were designed, 4.1.4 Performance with a height of no more than 20 mm. The main unit deals with sampling rate 96kHz resolu- 1) Content of implementation of slim dimension tion up to 24bit signal, and is able to authentically recre- ①Basic concept ate digital sounds from the main ECU. One characteristic Structure: made slim without changing material, with of the main unit is that it has achieved actual values further consideration given to clearance. which satisfy the performance target values for realizing Parts: parts selected with focus on slim chips.