Nippondenso Co., Ltd.

Toyota Jidosha Kabushiki Kaisha

Teruyoshi Wakao

Noriyuki Nakashima

Kimio Tamura

Ken Asami

Kazunori Sakai

Syouichi Masaki

Nobuhiko Makino

Shouichi Masaki

Susumu Masutomi

A plurality of speed sensors sense rotational speeds of respective vehicle wheels including a right-hand vehicle wheel and a left-hand vehicle wheel. A speed of the right-hand vehicle wheel and a speed of the left-hand vehicle wheel are calculated on the basis of detection signals of the speed sensors. A judgment is made as to whether or not a vehicle wheel having a small tire is present in the vehicle wheels on the basis of the calculated speeds of the right-hand vehicle wheel and the left-hand vehicle wheel. In cases where a vehicle wheel having a small tire is judged to be absent, a control quantity is calculated by use of all the detection signals of the speed sensors. In cases where a vehicle wheel having a small tire is judged to be present, a control quantity is calculated by use of the detection signals of the speed sensors except the detection signal of the speed sensor of the vehicle wheel having the small tire. A controlled object is controlled in accordance with the calculated control quantity.

Vehicle control system

In an antiskid control system, the acceleration of a vehicle wheel is detected and compared with a predetermined value. A first count value is incremented in response to the detection of the wheel acceleration exceeding the predetermined value. When this first count value exceeds a reference count within a first preset period, the road is interpreted as having a rough surface and a second count value is similarly incremented in response to the detection of the wheel acceleration exceeding the predetermined count. If the second count value does not reach the reference count within a second preset period longer than the first preset period, the road is interpreted as having a smooth surface. The gradient of brake hydraulic pressure of the vehicle is controlled in response to the different interpretation of the road surface.

Antiskid control with surface roughness compensation

A pulse signal is generated by a wheel speed sensor with a frequency proportional to the speed of rotation of a vehicle wheel, the pulse signal comprising a plurality of frames each having a series of a predetermined number of pulses which are tended to be affected by noise and pulse mutilation. Pulses in each frame are counted and from the count is derived an instantaneous wheel speed value. The difference between the successively derived instantaneous speed values is taken and compared with a predetermined threshold. A first or a second indication is given in response to the difference being lower or higher than the threshold, respectively. If the first indication is given, output signals representing the average wheel speed and average wheel acceleration of the wheel are derived from the instantaneous speed values of successive frames. If the second indication is given, the instantaneous speed value of the previous frame is used instead of the instantaneous value of the subsequent frame which is disturbed by noise or pulse mutilation to derive the output signals.

Wheel speed and acceleration detection immune to disturbance

In an antiskid control system for the hydraulic braking system of a wheeled vehicle, the rotational speed of a vehicle wheel and the acceleration of the wheel are detected and levels of road surface friction are determined on the basis of the wheel speed and acceleration to give a first indication that the road has a high value of friction or a second indication that the road has a low value of friction. The wheel speed and acceleration are analyzed to detect a down-pressure mode to decrease the fluid pressure of the braking system and an up-pressure mode to increase the pressure. In response to the presence of the first indication, the down-pressure mode is effected at a lower rate and then at a higher rate. In response to the occurrence of the second indication, the down-pressure mode is effected at the higher rate.

Antiskid control with surface friction compensation

In an antiskid control system for a motor vehicle, the speed and acceleration of at least one vehicle wheel are detected, and from the detected wheel speed, the speed of the vehicle is estimated. First and second variable threshold values are derived from the vehicle speed. The wheel speed and acceleration are compared with the first and second thresholds, respectively, to estimate the level of road surface friction and to operate solenoid-operated hydraulic brake pressure decreasing means. The operating period of the pressure decreasing means is controlled in accordance with the estimated road surface friction to prevent excessive reduction of the brake pressure and premature locking of the wheels.

Antiskid control with surface friction compensation by prolonged

A shock absorber control system for controlling the damping force of a variable shock absorber comprises a speed sensor for generating a signal indicative of the wheel speed of at least one wheel of the vehicle and a control unit for controlling the damping force. The control unit derives the acceleration from the wheel speed signal and compares the derived acceleration with upper and lower references. The damping force control is effected when the acceleration varies successively so as to assume both values outside the range between the upper and lower references.

Vehicle shock absorber control system

In an antiskid control system the speed of a vehicle wheel is compared with a variable threshold which is a function of the speed of the vehicle and a first comparator output is generated when the speed is lower than the variable reference. The acceleration of the wheel is compared with a predetermined threshold for generating a second comparator output when the acceleration is lower than the threshold or a third comparator output when the acceleration is higher than the threshold. The fluid pressure of the braking system is lowered in response to there being a simultaneous presence of the first and second comparator outputs and raised in response to there being a simultaneous presence of the first and third comparator outputs.

Antiskid control with wheel-speed difference compensation

In an antiskid control system, first and second wheel speed values are derived from pulse signals supplied from wheel speed sensors to indicate respectively the rotational speeds of first and second wheels of the vehicle. A trimming value is derived from the difference between the first and second wheel speed values and used as a multiplier by which the first wheel speed value is multiplied to compensate for the deviation of the speed of the first wheel with respect to the speed of the second wheel. The compensated first wheel speed value compared with a variable threshold that is a function of the speed of the vehicle to determine the down pressure timing.

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Nagoya, Japan

Teruyoshi Wakao