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A hybrid system that has been put on the market by Nissan Motor Company was configured by removing the torque convertor with a lockup clutch from a conventional 7-speed automatic transmission and installing a clutch and a motor in its place. This hybrid electric vehicle (HEV) has a simple structure and is expected to improve fuel economy and responsiveness because it eliminates the torque convertor. One issue for this system is that an abrupt change in the input torque could cause torsional vibration of the drive shaft, resulting in a severe degradation of ride comfort. To solve this problem, an original vibration control system that was adapted for the mass-produced LEAF electric vehicle was also adapted for use on this HEV fitted with an engine and a 7-speed automatic transmission. This control system enables the hybrid vehicle to generate maximum motor torque at launch and also provides significant advantages for vehicle design.

The one-motor, two-clutch hybrid system adopted by Nissan requires high control performance for the entire system, because the single motor provides the various functions of a drive motor, generator and engine starter depending on the driving situation. An especially challenging problem is to prevent the motor torque variation caused by engine start while transmitting driving torque to the drive wheels in a situation where the engine is started in response to the driver's demand for acceleration during motor-only operation. In this case, it is effective to let the clutch on the driving side slip until engine start is completed. For that purpose, we designed the slip control system described here. This system controls driving torque by the clutch while controlling the slip speed by means of the motor speed control. The slip speed can be controlled with high accuracy because the motor speed is controlled by the motor torque which is easily controllable.

It is difficult for a conventional robust control algorithm to assure the performance of a slip speed control system, because the plant (lockup system) includes the nonlinear characteristics of the hydraulic system and large changes in the parameters of the slip model at low vehicle speed. The purpose of this study is to reduce the fuel consumption and improve the drivability of vehicles at takeoff by using a slip speed control system. Providing a large feedback gain is effective in reducing the influence of nonlinearity. However, since the operating parameters of the lockup clutch change depending on the driving conditions, that is not possible. A feedback compensator with a gain-scheduled H∞ control method was used in this study to solve these problems. The effectiveness of the slip speed control system was demonstrated in driving tests. Using this control system, the slip speed can be controlled with high accuracy, thereby reducing unnecessary revving of the engine.

A new control system for the coasting range was designed with the μ-synthesis technique to achieve robust stability, based on the slip speed control system that was reported in our previous paper.(1) The results of driving tests conducted with the fuel supply cut off while coasting confirm that the new control system is able to avoid engine stall even under sudden hard braking on a low friction road (μ<0.1) at a vehicle speed of 20 km/h and a turbine speed of 1000 rpm. The system also allows the lock-up clutch to slip stably at a certain target slip speed at anytime while coasting and achieves robust performance against characteristic variations of the lock-up mechanism. This slip speed control system thus makes it possible to extend the fuel cut-off range to a lower engine speed of 800 rpm, down from 950 rpm, thereby improving fuel economy by about 1%.

This paper describes a design tool and a software platform for FlexRay systems that are investigated in Nagoya University and are proposed to JasPar. The design tool reads the specification of a system as a task graph that consists of a set of tasks and messages among them. The design tool, then, allocates the tasks to ECUs and schedules the messages on a FlexRay network. The software platform consists of a middleware called time-trigger module (TTM) which dispatches time-triggered tasks, a communication middleware for a time-triggered network (TT-COM), a network management middleware for FlexRay (FlexRay-NM), and a device driver for FlexRay controller.

Lock-up operation of an automatic transmission is known as one good method of improving fuel economy. However, locking up the transmission at low vehicle speeds can often cause undesirable vibration or booming noise. Slip control of the lock-up clutch can resolve these problems, but the speed difference of the lock-up clutch needs to be controlled at a certain value. This control system has to overcome large changes in the parameters of the lock-up system at low vehicle speeds and also changes with regard to the speed ratio in a continuously variable transmission (CVT). In this study, this complex non-linear system has been modeled as a first-order linear parameter varying (LPV) system. A robust control algorithm was applied taking various disturbances into account to design a new slip lock-up control system.

Automotive electronic control systems have tended to become more complex in recent years as a result of stronger requirements for environmental friendliness and higher levels of driveability. The first step in developing a control system is to study the required logic and system configuration at the initial stage of new vehicle development. The authors have incorporated an engine-vehicle model in a control system CAD program to simulate the logic needed for various control tasks. This paper presents a typical application in which a behavior of some outputs, such as engine torque and acceleration, was analyzed, and the electronic controls needed to assure driveability were identified. The construction and operation of a controller-in-the-loop system are also described.