A tire (100) rolls on a surface (105). A method (600) for providing maximum traction coefficient between the tire (100) and the surface (105) include steps for detecting a momentary slip of the tire (100) on the surface (105); detecting a momentary traction coefficient; forming a tuple (410, 510) from the slip and the current traction coefficient; choosing a characteristic curve (205, 305) from a number of predetermined characteristic curves (205, 305) on the basis of the tuple (410, 510), whereby each characteristic curve (205, 305) describes a traction behavior of the tire (100) or a corresponding characteristic pitch; determining the maximum traction coefficient on the basis of the selected characteristic curves (205, 305); and thus providing the maximum traction coefficient.

A four wheel steering vehicle (1), in which front wheels (2f) and rear wheels (2r) can be steered in response to a steering input from a steering wheel (11), includes a rear wheel steering control unit (50) that variably controls a rear wheel steering device such that the rear wheels are steered in a prescribed relation to a steered angle of the front wheels. When the steering input is determined while the front wheel brake and the rear wheel brake are engaged, the rear wheel steering control unit disengages the rear wheel brake and steers the rear wheels. When the fore and aft inclination angle detected by an inclination sensor (40) provided on the vehicle is greater than a threshold value, the rear wheel steering control unit prohibits a steering of the rear wheels and keeps the rear wheel brake engaged even if the steering input is determined.

An apparatus and a method for estimating a road surface friction coefficient relate to an apparatus of estimating a road surface friction coefficient including an additional power control module that arbitrarily adds a braking force, which causes a wheel speed difference, to an axle of the vehicle to which the braking force is applied, and together adds a driving force that cancels the braking force to an axle of the vehicle to which the driving force is applied, when it is determined that a driving state of the vehicle is an inertial driving state, and a road surface friction coefficient estimation module that estimates the road surface friction coefficient by the wheel speed difference caused by a newly added braking force.

The invention provides a road surface condition determining system with improved accuracy. In the system, a plurality of vehicles W.sub.i are used, each equipped with on-board sensors (11, 12) for acquiring vehicular information, which is information on the behavior of the vehicle during travel, a feature value calculating means (13) for calculating a plurality of feature values to be used in estimating the condition of the road surface on which the vehicle is traveling from the vehicular information acquired by the on-board sensors (11, 12), and a transmitter 16 for transmitting the feature values to the outside of the vehicle. A server (20) has a data storage means (22) for accumulating the plurality of feature values from the plurality of vehicles. A road surface condition determining unit (30) determines a road surface condition using the accumulated feature values. And the system determines the road surface condition at the location within a predetermined range within a predetermined space of time.

An apparatus of changing deceleration of a braking curve based on a variation in a coefficient of friction may include: a coefficient-of-friction calculating unit calculating a first coefficient of friction between a brake disk and a friction material at a first point in time, and calculating a second coefficient of friction between the brake disk and the friction material at a second point in time at which a preset driving distance has elapsed from the first point in time; a determination unit determining whether there is a change in coefficient of friction between the first coefficient of friction and the second coefficient of friction; and a deceleration changing unit changing deceleration by regenerative braking or deceleration by hydraulic braking from a preset braking curve by an amount of a variation in deceleration according to the variation in coefficient of friction, when there is a variation in coefficient of friction.

The invention relates to a control system for controlling a torque generator of a vehicle. The control system is configured to receive one or more electrical signals indicative of a surface indicator; receive one or more electrical signals indicative of a deceleration demand; select a surface type from a plurality of predetermined surface types based on said one or more electrical signals indicative of a surface indicator; determine a target vehicle deceleration in dependence on the selected surface type; determine, based on said one or more electrical signals indicative of a deceleration demand, a requirement to decelerate the vehicle; and in dependence on determining said requirement, output a control signal to the torque generator. The control signal is configured to cause the torque generator to provide the target vehicle deceleration.

A method of determining a surface condition of a path of travel. A plurality of images is captured of a surface of the path of travel by an image capture device. The image capture device captures images at varying scales. A feature extraction technique is applied by a feature extraction module to each of the scaled images. A fusion technique is applied, by the processor, to the extracted features for identifying the surface condition of the path of travel. A road surface condition signal provide to a control device. The control device applies the road surface condition signal to mitigate the wet road surface condition.

A method for determining a friction coefficient potential of a road surface. A total torque for operating a vehicle is unequally distributed among at least two wheel torques at wheels of the vehicle. The friction coefficient potential is ascertained using a detected slip between the road surface and at least one of the wheels and the wheel torque present at the wheel.

A method and system for estimating the potential friction between a tire and a rolling surface in which: a first and second engaged-friction/kinematic-quantity reference curve respectively corresponding to a first and to a second reference value μρ.sub.1, μ.sub.P2 of potential friction with μ.sub.P2>μ.sub.P1 are provided; a first and a second kinematic quantity threshold value or a first and a second engaged friction threshold value are provided; the engaged friction μ between the tire and the rolling surface is determined; a current value of a kinematic quantity between the tire and the rolling surface is determined; a current working point given by the engaged friction μ and the current value of the kinematic quantity is determined; and the current value of the kinematic quantity is compared with the first and the second kinematic quantity threshold value or, respectively, the engaged friction μ is compared with the first and the second engaged friction threshold value.

The invention provides a method for accurately predicting a road surface condition at a location within a predetermined range. To that end, the road surface conditions at the location within the predetermined range are predicted using road surface estimation decision values calculated using vehicular information, which is the information on the behavior of a vehicle W.sub.i during travel obtained by an on-board sensor mounted on the vehicle, or estimated road surface conditions estimated using the road surface estimation decision values. In doing so, the road surface condition at the location within the predetermined range is predicted based on the road surface estimation decision values calculated for the location within the predetermined range or the time-dependent changes in the estimated road surface conditions.