JTEKT (Japan)

Over-reliance on the automation of transportation systems is understood to be the cause of new types of accidents. In this paper, the automated driving system is augmented with control methods enabling driver intervention without its full deactivation. The proposed control relies on three functions: interaction, arbitration, and inclusion. Following the description of the state-of-the-art and limitations of the available technology, the proposed control framework is introduced to provide continuous driving assistance or override-free operation. It is believed that this contributes to more intuitive steering and consequently improved trust building. Examples of applications for the development of advanced driver assistance system functions are then presented and discussed, supported by experimental data.

This article proposes a method to independently control the gain and the phase characteristics of the vehicle frequency response. In steer-by-wire vehicle, it is possible to design the characteristics of vehicle dynamics like the yaw response. However, the gain and phase of the frequency response of linear systems are coupled which limits the tunability. Therefore, when one characteristic is changed, the other is changed too. To deal with this issue, we propose a control method for enabling independent gain and phase characteristics of the yaw rate dynamics on a steer-by-wire system. The construction of a NARX model with a neural network enables generating the nonlinear characteristics. Furthermore, a LQR controller calculates the front wheel angle to track the nonlinear target yaw rate. The proposed control is validated on a steer-by-wire equipped vehicle. The control strategy is described and experimental data demonstrate the improvement on maneuverability and stability.KeywordsSteer-by-wireVehicle dynamicsMotion control

ADAS and AD are the two major topics for the current and next generations of vehicles. In this context, it is necessary to develop technical solutions to enable larger-size vehicles to follow the trend with an existing 12 V vehicle power supply. EPS can only replace HPS (Fig. 1) as long as this does not degrade performance during any steering maneuvers.

Advanced Driver Assistance System (ADAS) and Automated Driving (AD) are the two major topics for the current and next generations of vehicles. To realize them in full-size vehicles equipped with a 12 V power supply, the need for electric power steering (EPS) is increasing. Currently, the steering system of full-size vehicles is equipped with hydraulic power steering due to electric power shortage. An auxiliary power supply system using a lithium-ion capacitor was developed in order to solve the concern. In addition, to mount the system in the vehicle with no cooling–heating equipment, development of expanding the operating temperature range of the lithium-ion capacitor was conducted. Several improvements have made the capacitor operate stably in high-temperature environments above 100 °C.

The effects of friction are critical to the dynamics of electric power steering (EPS). On the one hand, friction contributes to the stability of the system and filters some of the disturbances (road vibration, etc.). On the other hand, it negatively affects the driving feel and refrains from accurate positioning of the steering wheel. In addition, for steering manufacturers, friction hinders the development and tuning of the assistance strategy. Therefore, controlling or eventually suppressing friction in EPS is a real challenge. In this paper, a control strategy for the active compensation of friction in a column-assist-type EPS is presented. The assist motor and the electronic control unit are used to cancel the friction effect in order to imitate the behavior of an ideal frictionless system. The feasibility of this strategy is demonstrated on the power column (the upper part of the steering system) using the same information (signals) as that available in an actual product. The proposed control is based on a model of the power column including slip-and load-dependent friction forces. For this purpose, a detailed simulation model, developed and validated in a previous work, is reduced to a lower order model to enable real-time computation. The LuGre model is used to compute both the static and dynamic friction forces with continuous formulation. The control architecture is composed of two cascaded feedback loops. The internal loop estimates the internal friction of the system and compensates for it through the motor input. The external loop contains a frictionless reference model used as a trajectory planner and a linear controller, which attempts to minimize the error between the plant and the reference responses. The stability and the robustness of the control strategy are formally analyzed. Specifically, it is shown that the limit error between the plant and the reference responses can be made arbitrarily small with appropriate values of the gains. Experimental results demonstrate that the control strategy is successful in tracking the frictionless reference trajectory, and confirm the robustness against inaccurate friction parameters.

The existing research of steering efficiency mainly focuses on the mechanism efficiency of steering system, aiming at designing and optimizing the mechanism of steering system. In the development of assist steering system especially the evaluation of its comfort, the steering efficiency of driver physiological output usually are not considered, because this physiological output is difficult to measure or to estimate, and the objective evaluation of steering comfort therefore cannot be conducted with movement efficiency perspective. In order to take a further step to the objective evaluation of steering comfort, an estimating method for the steering efficiency of the driver was developed based on the research of the relationship between the steering force and muscle activity. First, the steering forces in the steering wheel plane and the electromyography (EMG) signals of the primary muscles were measured. These primary muscles are the muscles in shoulder and upper arm which mainly produced the steering torque, and their functions in steering maneuver were identified previously. Next, based on the multiple regressions of the steering force and EMG signals, both the effective steering force and the total force capacity of driver in steering maneuver were calculated. Finally, the steering efficiency of driver was estimated by means of the estimated effective force and the total force capacity, which represented the information of driver physiological output of the primary muscles. This research develops a novel estimating method for driver steering efficiency of driver physiological output, including the estimation of both steering force and the force capacity of primary muscles with EMG signals, and will benefit to evaluate the steering comfort with an objective perspective.

This paper is concerned with developing a new method for measuring a driver’s steering efficiency during a steering manoeuvre, for investigating the driver’s steering performance and for evaluating the steering comfort. Electromyography was successfully used to measure the driver’s muscle activity and to reveal the function of the driver’s key muscles in the steering manoeuvre. A measurement of the driver’s steering efficiency during a dynamic steering manoeuvre with two hands is presented on the basis of a regression analysis of the electromyography and steering-force data. The proposed measurement procedure consists of two parts. First, a multiple-regression analysis of the steering-force and electromyography data is conducted, and the steering forces in the steering wheel plane are predicted using the electromyography data of the key muscles producing the steering torque. Second, by predicting the steering force, the force capacity of the driver in the steering manoeuvre is estimated, and then the steering efficiency of the driver is measured. The steering efficiency of the driver, which characterizes the inefficiency, is thought to be a significant movement control strategy employed by driver, and its application in investigating the driver’s steering strategy is the subject of further study.

People's awareness of disaster prevention has risen, after the Great East Japan Earthquake. In local communities, the decision of the disaster prevention plan is pushed forward. In the first step, the evacuation plan is considered, however there are various limitations on-the-job training with a lot of residents' participation. Especially, it is impossible to take account of disaster conditions such as the collapses of the liquefaction, the collapses of the block wall and the collapses of the wooden house etc. in normal circumstances.In this study, an evacuation simulation system with tsunami and high tide disaster prediction is developed, and using this developed simulation system damage situations in a local community are estimated. The data base system based on the simulation results is developed in order to make effective use for evacuation for a variety of disaster situations. A costal area in Takamatsu City is selected, and some evacuation plans reflecting the disasters situations obtained by the simulation data base are made and examined.