A vehicle braking system for automotive vehicles in which a circuit is provided for continually calculating a controllable deceleration figure which is related to the required vehicle velocity reduction over a measured headway spacing and for calculating a non-controllable deceleration constant representing maximum deceleration available for braking action. A signal is generated for effecting vehicle braking when the deceleration figure is equal to or greater than the deceleration constant. A new, safe value of deceleration constant is obtained with each vehicle acceleration and deceleration and the deceleration constant is decreased at a predetermined rate between vehicle accelerations and decelerations.
Apparatus provides a signal to an operator of a following vehicle when it is necessary to take appropriate action to avoid coming within a predetermined distance of a lead vehicle proceeding in the same direction. From initial predicted forward velocities and distances of the lead and following vehicles, the signal apparatus (1) derives subsequent predicted velocities and positions of the lead and following vehicles and a subsequent predicted distance D(t) between the lead vehicle and the following vehicle after a projected short time interval while assuming a predetermined braking action of the following vehicle (2), derives and compares the subsequent predicted distance D(t) between the lead vehicle and the following vehicle with a least distance D.sub.LEAST, and (3) sets the least distance D.sub.LEAST equal to the subsequent predicted distance D(t) between the lead vehicle and the following vehicle if the latter is smaller. The signal apparatus iteratively applies the calculating means, beginning with forward velocities and positions derived from sensor signals as the initial predicted forward velocities and distances in the first iteration and generates a signal if and when the least distance becomes smaller than a minimum allowable distance D.sub.MIN.
A method for measuring the speed (V) of a vehicle (1) relative to the ground, of the type using the deviation in frequency associated with the Doppler effect between a transmitted wave (3) sent by radar (2) solidly connected to the vehicle and a reflected wave (4) reflected by the ground, characterized in that radar of the type allowing simultaneous measurement of the relative distance (D) and the relative speed (V) between the vehicle and the ground is used, and that the distance measurement is used to validate the speed measurement.
A vehicle collision control system has a distance measuring sensor, a collision predictive device for outputting a collision predictive signal, a deceleration calculating device for calculating a first limit deceleration allowing the vehicle to run while braking without losing its stability and a second limit deceleration for making the collision speed lower than a survival space ensuring speed, an arithmetic processing device for outputting a braking start signal upon comparing the aforementioned limit decelerations which change according to the running of the vehicle after the collision predictive signal is outputted, a braking command device for commanding a predetermined braking force to a braking device upon receiving the braking start signal, an impact sensor for sensing, and a collision signal generating device for outputting a collision occurrence signal to the logic circuit when the impact sensor senses the collision, so that an ignition signal is outputted to the inflator of the air bag device according to a logical product between the collision predictive signal and collision occurrence signal.
A collision-prediction unit for a vehicle including a road condition detector, a maximum deceleration estimator, a forward vehicle detector, a forward vehicle deceleration calculator, and a collision examiner is provided. The road surface detector detects a condition of a road surface on which the vehicle travels. The maximum deceleration estimator calculates a maximum vehicle deceleration for the vehicle on the road surface having the detected condition. The forward vehicle detector detects a moving condition of a forward vehicle located ahead of the vehicle. The forward vehicle deceleration calculator calculates a forward vehicle deceleration based on the moving condition of the forward vehicle. The collision examiner determines whether a collision between the vehicle and the forward vehicle is imminent by comparing the forward vehicle deceleration to the maximum vehicle deceleration of the vehicle.
