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This paper provides an overview of automotive electronic systems put into products over the past decade, and describes automotive electronics which have been demonstrated in experimental cars. In addition, future electronic systems found to be promising for the practical use in coming years and the direction of development of electronics are also discussed, as an extention of the overview mentioned above.

This paper presents a technique to predict the suspension load in early design stage when a passenger car with low profile tires goes over a bump. The suspension load is simulated by using ADAHS (Automatic Dynamic Analysis of Mechanical Systems). The tire was modeled as a radial spring with non-linearity decided by test data. The simulated results of suspension load agreed with the test data. The effect of shock absorber characteristics and spring bumper stiffness on the suspension load was studied by using this simulation model. As a result, the optimum specification for suspension load reduction was taken.

The shock absorber of suspension has two important basic functions. One is to control vehicle attitude changes when steering and when accelerating and decelerating, and the other is to dampen forces transmitted from the road by its damping effect, thus softening shocks. The characteristics of these two demands in performance, driving stability and riding comfort, conflict with each other but are selected from the concept of a car and from coaching by users. Namely, someone puts stress on driving stability and the other puts stress on riding comfort. Electronics have advanced in recent years and the use of electronic absorber control systems in order to achieve both driving stability and riding comfort has become widespread first of all in Japanese vehicles and also in European and American vehicles. Toyota first developed its TEMS (TOYOTA ELECTRONIC MODULATED SUSPENSION) in 1983 (1) and since then many improvements have been added.

The hybrid system has the typical advantage that it can realize various types of system control, because the system has two power units, engine and motor. On the other hand, however, constraints are increasing due to the complexity of the vehicle system. Compared to the conventional HILS construction and application, there are mainly two typical characteristics or themes for HV-HILS (i.e. HILS for hybrid vehicle control development). Firstly, HV-HILS requires full vehicle simulation environment, because the plural ECU control logic is intricately intertwined. Secondly, recent HILS system needs to run with more accurate or complicated plant models which are necessary to develop more accurate vehicle control logic.

Electronic Control Units (ECUs) for automobiles are usually composed of a main single-chip microcomputer and peripheral circuits with some standard and/or custom ICs. The peripheral circuits vary with the kinds of control or models of automobiles. When the peripheral circuits are replaced with a single-chip microcomputer, the ECU becomes compact and low in cost. This is because the ECU is constructed with only two LSIs and can be used for various kinds of control and various models of automobiles only by changing the program of the microcomputer. The microcomputer, however, requires many I/O functions and high reliability. We have developed a new 4-bit microcomputer suitable for these requirements. The new microcomputer has two remarkable features. One is powerful I/O functions such as high speed I/O, serial I/O, parallel I/O, analog I/O, and default output that is generated in place of the calculated output by the main CPU when it fails.

A new ABS and Traction control system (TRAC system) has been developed and put into mass production in a new model LEXUS LS400. The TRAC system controls Sub-Throttle Valve and brake hydraulic pressure independently for left and right wheels. To realize the ABS and TRAC system,it is necessary for the Electronic Control Unit (ECU) to process complex algorithm and high speed calculation. The ABS and TRAC ECU for LEXUS LS400 is constructed by 3 TOYOTA custom 8-bit single chip microcomputers. Each CPU performs wheel speed calculation,ABS control and TRAC control,sharing the common data through high speed serial communication. This paper describes the function of each CPU,the method of CPU communication and fail safe function in the ECU.

A full vehicle multi-body dynamic (MBD) model with suspension control system is developed for fatigue life prediction under rough road condition. The model consists of tires, a trimmed body, heavy attached parts, powertrain, suspension, joints, and a driver model, and includes a suspension control system that varies characteristics of the suspension according to the rough road inputs. For tires, a commercial MBD tire model is employed with identifiable parameters. The models are simulated to run on the optically measured road surface of the proving ground. Apart from the trimmed body, several important heavy attached parts are modeled separately, that represent dynamic behavior that induces complex body input load. These parts, along with suspension and powertrain systems are connected to the body using nonlinear elements such as joints, springs, and dampers. Contact conditions are used to represent mount bushing, hood lock, stopper rubber, etc.

Toyota has developed a new continuously variable transmission (CVT) named “Super CVT”. The Super CVT has a wide ratio coverage and adopts a newly developed integrated control system with a direct injection gasoline engine (D-4) equipped with electronically controlled throttle. The combined package has achieved good fuel economy and a high overall level of performance. This paper shows the major features and performance of the Super CVT.

On board multiplexing communication system is regarded as a necessary technology for the future of electronic system in automobiles. Many companies are developing multiplexing systems and the ISO and SAE are active in establishing standards for communication protocols. The proposed communication protocol specifications have different specifications. Consequently, no compatible evaluation standards existed, and it was difficult to compare one protocol to another. Therefore, to assist the standardization activities of the IS0 and SAE, we have developed an evaluation method for distributed multiplexed communication systems and evaluated each of the proposed protocols using this method. These evaluations were performed from the point of view of the future users of these systems. In this paper we present the results of the experiments on distributed multiplexed communication systems each of which consists of communication IC and the proposed physical layer.

This paper analyzes the vibration of open-top cars known as lateral shake. The characteristics of the phenomenon were identified by means of road tests and a test method called the shake test was devised to reproduce these characteristics in order that the respective roles of the suspension, body and engine could be determined. On the basis of the analysis findings, a simple but practical simulation model was realized and used to investigate various methods of reducing lateral shake. The simulations indicated that although changing the natural frequency of the suspension has little effect, increasing the natural torsional frequency of the body and/or utilizing the engine as a dynamic damper results in a significant improvement. Further experiments conclusively demonstrated that by optimizing the body structure in accordance with FEM analysis results and optimizing the spring constant of the engine mounts, the level of lateral shake can be halved.

A smart analog integrated circuit (IC) is developed for use in an electronic control unit for an automotive variable power-steering system. This IC accepts a vehicle speed signal as its input, performs signal processings such as frequency to voltage conversion and function generation, and then as its output generates a pulse width modulated (PWM) signal whose duty corresponds precisely to a given piecewise linear function of the vehicle speed. The PWM output is used as a driving signal to a power MOSFET for the actuation and control of a linearly variable solenoid valve to vary the force needed for steering effort in a prescribed relation to the vehicle speed. The IC is fabricated by monolithic bipolar integrated circuit technology and has about 750 device elements in a chip size of 5.7 by 3.1 mm2. It is enveloped in a shrinked dual in-line package with 24 pins.

This paper describes the development of the electrical systems for the integrated control system which unified automobile electronic control systems and led to a dramatic improvement in vehicle dynamics. An outline of the system is presented first, followed by actual automobile application examples of electrical systems employing medium-speed multiplexing.

With the increasing use of electronic control systems to improve vehicle dynamics, there is an ever growing need to transfer control information among electronic control units(ECUs). To meet this need, a protocol was proposed for high-speed multiplex in the previous SAE paper 910463. Based on the paper, a prototype IC for high-speed multiplexing control was developed. First, a further analysis was made of the information which is transferred among ECUs. As a result, it was found that the information has certain distinctive characteristics. These characteristics are so distinctive that it may be relevant to devise a new protocol for communication. Based on the analysis, a new form of token passing method was implemented. By using this method, it is easy to calculate transmission latency time. So this method is suitable for a real time control application like vehicle dynamics control.

Several methods have been studied by using adaptive control in order to tune parameters of the cruise control automatically. But theoretical analysis has not been done by the reason of severe non-linearity. In this paper, a vehicle dynamics model is made with theoretical analysis, and two adaptive control methods to assist the conventional PID controller are proposed.

With an ever growing demand for the enhanced control of a vehicle and for the reduction of power and signal distributing wires in a vehicle, there is a pressing need for the development of Local Area Network (LAN) in a vehicle. LAN enables the exchange of various data among several electronic control units (ECUs), and results in the higher controlled performances of a vehicle and the reduction of the wires. In response to this need, two integrated circuits for vehicle multiplexing communication are developed. One is a communication control IC and the other is a bus driver/receiver IC, both based upon the standard of a PWM type of the J1850 for a communication protocol. The communication control IC is designed to have distinctive features such as a highly fail-safe operation and the reduction of the overhead for communication imposed on a central processing unit (CPU) of the ECU.

We have developed a new torsional damper spring which lowers the torsional rigidity of the clutch disc while retaining its conventional size. The following two items have been adopted in the newly developed spring: 1) A new steel wire which suppresses any core-softening of the element wire through nitriding. 2) A dual-stage shot peening method which uses harder steel shots (rather than conventional shots) in order to obtain an optimal residual stress profile. As a result of evaluating the fatigue characteristics of this spring, it was discovered that its fatigue strength is approximately 35% higher than that of the conventional spring. A clutch disc using this spring was able to absorb rattling noises which conventional clutch discs could not.

This paper describes the multiplex communication protocol, BEAN (Body Electronics Area Network), developed for body control system on passenger cars which in recent years has increased the scope of multiplex communication. BEAN is based on a protocol developed in 1992 (SAE920231) but expands upon the performance in areas, such as the suitability of the ID system for increase of ECUs, the variable data length enabling the transmission of diagnostic data, and the transmission rate, while keeping the cost and radiation noise level low. The software size of BEAN is compact enough to be implemented by general purpose 8bit MCUs which have recently seen improvements in performance. The BEAN communication devices are available corresponding to the scale of the application and configuration of the ECU taking into account the software capability. This protocol was evaluated using simulation with the body control system on luxury passenger cars.

In order to reduce the interior noise of a vehicle with a four-cylinder engine, investigations were made using finite element and vector methods, acoustic intensity testing and holography technique. The investigation resulted in inclination of the engine mounting, design changes to the front suspension member, a shock absorber engine mounting, structural modifications to reduce body panel vibration and a new engine mounting to insulate high frequency engine vibration.

Toyota succeeded in the fall of 1984 in manufacturing a complex engine and transmission control system using a newly developed single-chip microcomputer. This microcomputer, equipped with an 8K-byte ROM ( Read Only Memory) and a 256-byte RAM ( Random Access Memory), a powerful real time processing function, and a high-speed optimum instruction set, is better suited for automobiles. Application of the latest CMOS technology has enabled lower power consumption and improved noise immunity. The new system, which includes a new function; the electronic spark advance with knock control in addition to the conventional sophisticated system, has greatly improved the performance and driveability of vehicles.

Engine control systems were the precursor of scale automotive electronics systems using microcomputers. Toyota Motor Corporation introduced high - level, total control of the power train by applying system integration through introducing a multi - CPU system to the 1988 MY Toyota Camry. Integration in the ECU has been promoted to parallel with system integration. By adopting single - chip microcomputers, monolithic ICs, and hybrid ICs all designed and developed for car electronics, and semiconductor barometric pressure sensors for car electron into ECU's. etc. ever - expandable functions can be provided in a smaller and more lightweight ECU package with higher reliability.