As shown in the following figure, all four wheels of a four-wheel steering vehicle are equipped with independent hub motors, so that the maximum rotation angle of a single wheel can reach 90 degrees, and the wheels are driven by the hub motors to move back and forth. The vehicle controller can control the four hub motors independently and freely, and then realize the independent and free control of the forward direction and forward speed of the four wheels. Through different control combinations, that is, front, rear, left and right wheel angles and steering combinations, three movement modes of the vehicle are realized: lateral, oblique, in-situ rotation and steering. The following describes the basic control methods for realizing various operation modes in this patent.
As shown in the following figure, the front and rear wheels of the vehicle rotate 45 degrees to the inner sides in two directions respectively, and then the rotation direction and speed of the four wheels are controlled by the hub motor. Even if one wheel drives forward and the other wheel drives backward and keeps the same speed, the vehicle can be guaranteed to rotate around the vehicle center L0 in situ, so that the vehicle can turn around in situ. The in-situ rotation and steering movement mode of the vehicle can be comparable to the universal wheel rotation operation mode on the office chair. This function is very practical when turning around on a narrow road.
It is easy to understand the lateral steering function. As shown in the following figure, when all four wheels rotate 90, the vehicle can move laterally from left to right. When reversing in a narrow space, as long as there is enough space before and after the parking space, the vehicle can be laterally translated to the parking space through "four-wheel steering". The vehicle equipped with this patent can simply and effortlessly dump the vehicle into the parking space without the driver using various reversing skills.
As shown in the following figure, when the front and rear wheels all turn in the same direction by the same angle, that is, when turning in the same phase, the vehicle can move obliquely, which can be considered as a compound movement of longitudinal straight line operation and lateral operation. When the vehicle is driving at high speed, adopting in-phase steering can reduce the yaw rate of the vehicle body, effectively restrain the dynamic cornering tendency of the vehicle body and improve the handling stability.
Because the motion mode of "four-wheel steering" vehicle is different from that of traditional vehicles, the patent puts forward the function of prompting motion signals. This function includes a sensor. When the wheel enters the 45 or 90 motion mode, a "sound or light" prompt signal will be used to let drivers and pedestrians near the vehicle know the next operation of the vehicle, so as to ensure the safety of drivers and pedestrians.
Toyota's "four-wheel steering" patent provides more vehicle movement and steering modes, which is more applicable in some special road conditions and parking scenes, and is a great boon for novice drivers. Although the patent is currently in the application stage, with the rapid development of automobile technology, it is not impossible to act like a science fiction movie in the future.