Abstract: An apparatus for detecting a wheel grip on a road has a wheel speed sensor for detecting a revolution speed of a wheel of a vehicle, a plurality of band-pass filters for filtering an output of the wheel speed sensor at a plurality of frequency bands, and a reference value memory device for storing in memory reference values dependent on the revolution speed of the wheel. The reference values are set for each of the frequency bands of the plurality of band-pass filters. The wheel grip on road is detected based on the correlation between that signal output for each of the frequency bands which is obtained through the band-pass filters and that reference value for each of the frequency bands which is stored in memory in the reference value memory device.

Abstract: A hydroplaning detecting system comprises wheel rotational speed detecting apparatus for detecting a wheel rotational speed of a wheel of a vehicle, reference pattern storage apparatus for previously storing a reference pattern of wheel rotational speed which varies over a period of time and is characteristic of hydroplaning generation, actual variation pattern extracting apparatus for extracting a actual variation in the wheel rotational speed over a period of time, and judgment apparatus for judging the matching between the reference pattern and the actual variation pattern. Thus, this hydroplaning detecting system is capable of accurately detecting the generation of hydroplaning.

Abstract: A pneumatic tire pressure determining system on a motor vehicle detects an actual rotational speed difference between rotational speeds of front or rear left and right road wheels of the motor vehicle, detects an operating condition of the motor vehicle, and calculates an adequate rotational speed difference between rotational speeds of the front or rear left and right road wheels based on the detected operating condition of the motor vehicle. The system compares the adequate rotational speed difference and the actual rotational speed difference, and when the difference between the compared actual and adequate rotational speed differences exceeds a predetermined value, the system determines a pneumatic tire pressure reduction.

Abstract: A physical quantity control device includes first and second control elements having different sensitivities from one another, the first and second control elements providing outputs to change at least one physical quantity in response to first and second operational quantities individually input to the first and second control elements. First and second computing circuits are provided for computing the first and second operational quantities in response to a deviation between a predetermined target value and the physical quantity, wherein the physical quantity is feedback controlled to converge with the predetermined target value.

Abstract: A system for correctively controlling the turning movement of a vehicle, including a device for correcting the turning movement of the vehicle, a sensor for detecting the steering angle of a steering wheel of the vehicle, a steering angle hysteresis storage device for storing the hysteresis of the steering angle, and a reference value arithmetic device for determining a reference value of a physical quantity generated during a turning movement of the vehicle, on the basis of the hysteresis of the steering angle. The system also includes a detector for detecting an actual value of the physical quantity during the turning movement, a calculator for determining a deviation between the reference value and actual value of the physical quantity and a polarity of the deviation, and a control-quantity determining device for determining a control-quantity for the turning movement correcting device on the basis of the deviation obtained in the calculator.