Patent Application
20100304690
The present invention generally relates to a system for sensing a user's approach to a vehicle and more particularly relates to activating vehicle features prior to the user's arrival at the vehicle.
Key fobs, or remote keyless entry devices, that unlock, for example, the driver's door, passenger doors, or the trunk lid are well known. Some key fobs control other user preferred features such as seat position, radio station, and air control temperature settings. Many key fobs are manually activated by the user (active approach) as the vehicle is approached. Other key fobs transmit a signal in response to a low frequency query from the vehicle (passive approach), with the key fob signal being detected by the vehicle for activating the desired features.
However, these known low frequency passive systems require continuous (periodic) transmission and typically have a limited range of less than two meters. However, the low frequency transmission must be sufficiently long to reduce the current consumption of the transmission, while being short enough to allow a noticeable approach to activate the feature before the user arrives at the vehicle. These low frequency systems provide less time than desired for the activation of, for example, approach lighting. The user is already at or very near the vehicle when approach lighting would activate.
Furthermore, these low frequency passive systems cause unintentional actuations when the user is near the vehicle but does not desire to activate the functions. These unintentional activations cause an undesired drain on the vehicle and fob batteries and may create a security issue if the unintentional actuation leaves the vehicle accessible. These low frequency passive systems may include provisions to deactivate the approach sensing after extended continuous activation; however, this has the undesired result of not providing the vehicle user the expected operation when they return to the vehicle.
Accordingly, it is desirable to provide a system that triggers passive approach features with greater range and low power consumption, while minimizing false approach notification. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
A method for activating vehicle features when approaching a vehicle includes receiving a message by a vehicle system from a key fob, determining if the key fob is approaching the vehicle, activating selected vehicle features if approaching the vehicle, and instructing the key fob, if not approaching the vehicle, to reduce power until the message is no longer received by the vehicle system.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
The method disclosed herein provides for the activation of features of a vehicle, for example approach lighting of an automobile, as the user approaches the vehicle from a distance sufficient to light the approach. A key fob periodically transmits an RF presence signal at a rate which allows for two or more detection periods during a normal approach to the vehicle. The transmit rate is determined with consideration of an approach speed, for example fast walking, and a minimum range, for example 200 meters. For each signal received, the vehicle system measures the relative signal strength and determines if the key fob is approaching the vehicle and if the signal strength is sufficient to indicate close proximity. Upon detection of close proximity, the vehicle actuates welcome features such as approach lighting and additional sensors. Close proximity, for example, could be 100 feet. However, when the vehicle is parked and the key fob stays in proximity to the vehicle, false actuations are avoided. The key fob will initially continue to periodically transmit a presence signal at the pre-established rate. If the vehicle system detects the continued presence of the key fob at a signal strength indicative of close proximity, the vehicle instructs the key fob to decrease power in increments until the key fob is no longer detected. Additionally, the key fob may halt transmissions upon extended periods without motion; transmissions would resume upon detection of new motion. Upon subsequent movement of the key fob closer to the vehicle, the vehicle system will receive the periodic signal from the key fob, activate the approach features, and instruct the key fob to assume normal power levels until a user initiated interaction, such as opening a door. For example, the vehicle may instruct the key fob to halt transmissions upon the opening of a vehicle door or ignition, which signals a drive cycle is in process.
More particularly, the method determines whether a periodically transmitted RF message from a key fob is valid and either increases or decreases the RF message signal strength depending on the validity. If a valid RF message signal exceeds a defined strength, the vehicle features are activated, a message counter is set to zero, and the key fob is instructed to increase transmitting power to its predetermined maximum level. When the vehicle receives a predetermined number of RF messages above a defined signal strength, the fob is instructed to transmit at a lower power level. This step is repeated until the key fob transmits at a power level low enough that the vehicle no longer receives the RF messages, thereby saving energy by allowing the vehicle to maintain a low-power, sleep state.
Referring to
A key fob 202 shown in
Referring to
Unintended activation of the welcome features is prevented by the following steps. If the received RF data is a valid message 322, the message counter is incremented 324 and if the message counter exceeds a third threshold 326, for example 10 counts, an instruction is sent 328 to the key fob to reduce its power. With an exemplary range of 200 meters, then periodic transmission from the fob is likely to be greater than 30 seconds. Utilizing 10 counts would require continued presence of at least 5 minutes. These steps 322, 324, 326, 328 are repeated until either the determination 322 that an approach message is not received 322 and a determined time period (fourth threshold) is surpassed 330 (wherein step 302 is commenced), or if the message counter does not exceed the third threshold, step 328 is bypassed. An example of the fourth threshold would be 65 seconds. This threshold would be set based upon the value of the fifth threshold. To allow for potential interference with any single transmission from the key fob, the value would preferably be set higher than twice the period on which the fob transmits.
Referring to
A method has been described for passively detecting a key fob approaching a vehicle and enabling welcome (approach) features or functions. The key fob power is minimized when not approaching the vehicle in order to increase battery life. An approach is detected even when the key fob has been in proximity with the vehicle for an extended period of time. The use of RF signals to trigger passive approach features accommodates greater range with lower power consumption
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.
