A tire position determination system includes a position determination unit that determines a tire position by obtaining axle rotation information when each of tire pressure transmitters reaches a specific position on a tire rotation path of a corresponding tire and specifying a tire that rotates in synchronism with the axle rotation information of each axle. A cycle calculator calculates a rotation cycle of each axle based on the axle rotation information. A validity determination unit determines validity of accuracy of gravity sampling based on the rotation cycle, a gravity sampling interval time of a gravitational component acting on each tire pressure transmitter, and a gravity sampling frequency in the rotation cycle. The position determination unit determines the tire position based on a determination result of the validity determination unit.

A wheel assembly position identifying apparatus includes transmitters, each of which is provided in one of wheel assemblies and includes a transmission section and a control section, and a receiver, which includes a receiving section, a measuring section, and a wheel assembly position identifying section. The wheel assembly position identifying section is configured to detect, more than once, a rotational position of each wheel assembly at which the RSSI has an extreme value, for each position detecting signal received during one rotation of the wheel assembly, and identify the position of the wheel assembly in which the corresponding transmitter is provided based on variation of the rotational position of the wheel assembly at which the RSSI has the extreme value.

A tire condition detecting apparatus includes a condition detecting section, a transmission section, and a transmission-side control section. The transmission section is configured to transmit a signal that contains information related to the condition of the tire to a receiver, which includes a reception-side control section. The reception-side control section identifies the position of the wheel assembly in which the tire condition detecting apparatus is provided based on the received signal strength indication (RSSI) of the signal. The transmission-side control section is configured to cause a position detecting signal and an instruction signal to be transmitted from the transmission section to the receiver. The position detecting signal is configured to cause the reception-side control section to identify the position of the tire condition detecting apparatus. The instruction signal is transmitted before the position detecting signal is transmitted and instructs the reception-side control section to start obtaining the RSSI.

A wheel assembly position identifying apparatus includes transmitters, each of which is provided in one of wheel assemblies, and a receiver, which is provided in a body of a vehicle. Each transmitter includes a transmission section, an acceleration sensor, and a transmission-side control section. The receiver includes a reception section, which is configured to receive the signals, and a reception-side control section, which is configured to execute a first identifying process and a second identifying process. In the first identifying process, the positions of the wheel assemblies, in which the corresponding transmitters are provided, are identified based on variations of the rotational positions of the wheel assemblies at the time when the constant position signals are received. In the second identifying process, the positions of the wheel assemblies, in which the corresponding transmitters are provided, are identified based on the received signal strength indications (RSSIs).

An angular position is determined for an electronic module fixed to the inner face of the tread of a tire fitted to a wheel of a vehicle. A sensor for measuring the radial acceleration of the wheel is integrated into the electronic module, and a variation of the radial acceleration is detected that corresponds to a position of the electronic module when it contacts the ground. This variation is used to determine a frame of reference defined by an origin and a reference unit corresponding to an angular sector of the tire having a length is shorter than a mean length of the footprint of the grounded tire, in order to determine angular positions of the electronic module in the frame of reference.

In a wheel position detecting device, a receiver acquires gear information indicating a tooth position of a gear rotating in association with a corresponding wheel at a predetermined interval. In a wheel position detection, the receiver sets a variation allowance range based on the tooth position at a reception timing of a frame transmitted from a transmitter integrated to each wheel. When the tooth position of the gear at a subsequent reception timing of the frame is not within the variation allowance range, the receiver excludes the wheel corresponding to the gear from a candidate wheel. The receiver registers the wheel remaining last as the wheel to which the transmitter is integrated. The receiver performs the wheel position detection only when a wheel speed is higher than a predetermined threshold, so that the wheel position detection is performed based on an accurate tooth position.

A tire position registration system includes a receiver that estimates, from a data group of axle rotation information of each of axles obtained for each valve ID, a parent population of the axle rotation information of each of the axles. The receiver sets a synchronized wheel tolerance region, which functions as an index for determining validity of the corresponding axle rotation information, for each parent population based on a population mean that is a mean of the parent population. The receiver specifies the tire position by determining whether or not the axle rotation information obtained for each valve ID is included in the synchronized wheel tolerance region of the corresponding parent population and specifying the axle rotating in synchronization with the tire corresponding to the valve ID.

A road surface state determination device includes a tire-side device and a vehicle-body-side system. The tire-side device is attached to each of a plurality of tires included in a vehicle. The vehicle-body-side system is included in a body of the vehicle. The tire-side device may output a detection signal corresponding to a magnitude of vibration of the tire. The tire-side device may sense the detection signal and generate road surface data indicative of a road surface state appearing in a waveform of the detection signal. The tire-side device may transmit the road surface data. The vehicle-body-side system may perform bidirectional communication with the tire-side device and receive the road surface data. The vehicle-body-side system may determine the road surface state of a road surface on which the vehicle is traveling based on the road surface data.

A method for determining position of a tire pressure monitor equipped on a tire of a vehicle. The method is performed by a controller and comprises: detecting a radial acceleration and a tangential acceleration of the tire; computing a radial-versus-gravity value and a tangent-versus-gravity value based on the radial acceleration, the tangential acceleration and a gravity acceleration; determining an operating state according to variations of the radial-versus-gravity value and the tangent-versus-gravity value; determining whether the operating state is changed to another operating state; and when the operating state is changed, determining a position of the tire pressure monitor according to a change sequence of the operating states.

A tire-pressure information device should receive wheel information within a demanded detection time. A transmission controller of a sensor unit transmits wheel information as a radio signal at the timing when the turning position of the sensor unit detected by an acceleration sensor arrives at the transmission setting location after 1 minute has passed since the last transmission of the wheel information. This transmission setting location is set to a turning position which is advanced or retarded a setting adjustment angle (for instance, 146 degree) set to a value which is not a divisor of 360, with respect to the turning position when the last wheel information is transmitted last time.