Development of collision avoidance support system with active steering

1. Outline

As a basic idea for “zero traffic accident casualties”, TOYOTA suggests the integrated safety concept shown in Fig.1. In this concept, we aim to realize a car that will prevent an accident by reducing the state of danger of the car state via linking the safety system. Collision avoidance or collision damage mitigation provided by the Pre-Collision System (PCS) is a key function of the “Zero Traffic Accident Casualties”. The system outline of PCS is shown in Fig. 2.

When the system judges the possibility of a collision, it urges the driver to react by an alarm, and the automatic brakes assistance engages in case the risk of collision increases. However, collision avoidance only by engaging automatic brakes is limited from the viewpoint of interference with driver maneuvering.

Therefore, we developed the “Active Steering Avoidance Support” which uses steering control combined with automatic braking in case when the system determines the possibility of collision avoidance is arduous only with automatic braking and steering control provides such capability.

2. Technical contents

One of the conditions for Active Steering Avoidance Support activation is the existence of a collision avoidance path with the associated pedestrian in front of the vehicle. It is necessary to avoid any collisions with other non-associated subjects when deploying the steering control. Hence, the system detects not only the pedestrian but also the road surface ahead of the vehicle and generates an avoidance route within an area excluding any subject of collision.

2-1. Road surface detection by stereo camera

A stereo image sensor(Fig.3) mounted on top of the windscreen of a new model vehicle uses an image processing technique called “dense stereo matching technology” to estimate a region considered to be a road surface by tone distribution obtained from a stereo image.

2-2. Avoidance route generation

As shown in Fig.4, in addition to “avoidance steering” for evading pedestrians in the avoidance space, an avoidance route is generated by “turning back control” in order to keep the vehicle within its original lane. Steering control is performed based on the avoidance route while engaging automatic braking.

3. Summary

In this paper, we described a collision avoidance support system using steering control in addition to conventional automatic braking. This technology was adopted as an advanced safety package (Lexus Safety System + A) on LEXUS LS (Fig. 5) (since October 2017). This is the world’s first commercialized collision avoidance support system which is capable of judging a collision risk and perform a steering control. In respect to recent years with highest records of accidents with pedestrian fatalities, automatic braking alone can reduce approximately 60% of accidents and automatic braking combined with steering control is expected to reduce accidents further by 16% (according to Toyota).

Enhancing the application scope to other vehicle models based on this technology is planned for the future.

Fig. 1 The integrated safety concept of TOYOTA

Fig.2 The system outline of PCS

Fig.3 Stereo camera

Fig.4 Generated an avoidance route

Fig. 5 Overview of Lexus LS

Kotaro Saiki*1

Takahiko Murano*1

Tsunekazu Yasoshima*2

Naohide Uchida*2

Motoki Nishimura*1

*1 Member,TOYOTA MOTOR CORPORATION(〒471-8571 Toyota-cho, Toyota City, Aichi Prefecture)

*2 TOYOTA MOTOR CORPORATION(〒471-8571 Toyota-cho, Toyota City, Aichi Prefecture)