Patent Application
20060114100
Not Applicable.
Not Applicable.
The present invention relates in general to remote convenience and security systems for automotive vehicles, and, more specifically, to a wireless communication system for integrating functions of a two-way remote keyless entry system and a passive entry system.
Remote keyless entry (RKE) systems for vehicles have been in use for many years. These systems provide safety and convenience for a user entering or exiting a vehicle. Some of the typical features offered by these systems allow the user to lock/unlock doors and arm/disarm auto theft systems in a remote manner. In addition, remote starting of the engine and remote control of the climate control temperature setting after starting are commercially available. Typical RKE systems utilize a key fob with a radiofrequency (RF) transmitter which transmits to a base station in the vehicle. When the user is within range, the user actuates a corresponding button on the key fob to send a lock, unlock, or engine start command, for example. Two-way communication is typically implemented in remote start systems so that the user carrying the portable fob can be informed of the status of the vehicle (e.g., engine running status, door lock status, and temperature status). Thus, a two-way fob includes a visual display (e.g., LED indicator lights or an LCD graphical display panel) to convey the information to the user.
One disadvantage of this type of system is that the user must manually actuate the key fob to achieve the desired result. In an attempt to eliminate this disadvantage, passive entry systems, which operate in a hands-free manner, are being introduced. In order to avoid excessive battery consumption by periodic radio transmission from the fob, the approach of the user to the vehicle is usually sensed by the vehicle, which then wakes up the fob to perform a security check before actuating a passive entry function. Is it known, for example, to sense the presence of a user who is attempting entry into a locked vehicle via a particular door by detecting the lifting of the door handle. Using a low frequency (LF) wireless signal, the vehicle then interrogates the area around the door for a key fob containing a valid security ID code.
Passive entry communication operates over a much shorter range than RKE communication (e.g., 1 meter as opposed to 30 meters). Therefore, an LF signal (e.g., 134 kHz) is used for passive entry while a much higher frequency RF signal (e.g., 315 MHz or 433 MHz) is used for RKE since the LF signal decays over a shorter range. In addition, transponders operative at LF frequencies are readily available. As used herein, LF frequencies range from about 30 kHz to about 300 kHz. RF signals used in RKE systems are typically in the UHF band from about 300 MHz to about 3 GHz.
Security ID codes for validating a particular fob for accessing a passive entry function typically include rolling code encryption in order to deter code grabbing and relay attacks by potential thieves. Due to the low frequency signals used by passive entry systems, the exchanging of challenge and response signals used by a rolling code system has transpired using a data rate which is lower than the data rate for performing similar exchanges by RKE systems using RF signals. A slow data rate can result in problems because it is necessary to quickly validate a fob carried by the user after beginning to lift a door handle so that a door unlock mechanism can be activated before the door handle moves beyond an appropriate position.
The present invention has advantages of added convenience, faster response times, and increased security as results of integrating functionality of a passive entry system with a two-way RKE system having an active display.
In one aspect of the invention, an integrated passive entry and remote keyless entry system is provided for a vehicle, wherein the system comprises a vehicle communication system mounted in the vehicle and a portable fob for carrying by a user. The vehicle communication system comprises a trigger generator, an LF transmitter responsive to the trigger generator for broadcasting an LF wakeup signal, and an RF transmitter for broadcasting a UHF status message including vehicle status data to the portable fob. The vehicle communication system broadcasts a challenge signal to the portable fob after the LF wakeup signal. The portable fob comprises an LF receiver responsive to the LF wakeup signal, a fob controller for determining response data according to the challenge signal, and an RF transmitter for broadcasting a UHF response signal incorporating the response data. The portable fob further comprises an RF receiver for receiving the vehicle status data, a visual display for visually reproducing the vehicle status data, and a manual input key for activating the fob controller to generate a remote control message. The RF transmitter in the portable fob broadcasts a UHF control signal incorporating the remote control message. The vehicle communication system further comprises an RF receiver responsive to the UHF control signal and a base controller for initiating a corresponding remote control function in response to the UHF control signal.
Referring to
An RF antenna 24 is coupled to RF receiver 15 as well as to RF transmitter 16 through a matching circuit 25. Microcontroller 13 in base station 11 is coupled to an engine controller 26 for controlling an engine 27. Door module 22 and engine controller 26 act as function actuators for implementing RKE commands received by base station microcontroller 13. Microcontroller 13 receives vehicle status data from engine controller 26 (e.g., to confirm that the engine has successfully started in response to a remote engine start command) and from door module 22 (e.g., to confirm locking of the vehicle doors). The vehicle status data can be sent to portable fob 12 within a vehicle status message as part of a confirmation following execution of particular RKE commands, for example.
Portable fob 12 includes a microcontroller 30 coupled to input buttons 31 typically including separate push buttons for activating RKE commands for locking and unlocking doors, remotely starting or stopping an engine, panic alarm, and others. An RF transmitter 32 is coupled to an antenna 33 through a matching network 34. RKE commands initiated by depressing a push button 31 are broadcast by RF transmitter 32 and antenna 33. An RF receiver 35 is coupled to antenna 33 and microcontroller 30 for receiving UHF status messages broadcast by base station 11, such as engine running status for a remote start function. A display 36 is coupled to microcontroller 30 for displaying vehicle status data from a status message to a user.
An LF receiver 37 is coupled to microcontroller 30 and to an LF antenna 38 for detecting wakeup signals broadcast from vehicle 10. A battery 39 in fob 12 supplies electrical power to all the other components of fob 12 during normal operation.
In operation, a typical passive entry sequence begins when a door handle switch in door module 22 generates a trigger pulse provided to microcontroller 13 resulting in executing a trigger generation function within microcontroller 13. In response to trigger generation, LF transmitter 14 is activated in order to generate an LF wakeup signal to activate LF receiver 37 in fob 12 via antennas 20 and 38. The LF wakeup signal is also used to localize the fob based on which LF transmitter antenna 20 or 21 generates the strongest received LF wakeup signal in fob 12. The LF wakeup signal has a known format including an operation code for identifying the signal as a wakeup signal and preferably also including an antenna identifier unique to the antenna being used to transmit each LF wake-up signal. Localization of the fob is necessary to ensure that a person carrying an authorized fob is properly located in the area where the passive function is being requested (e.g., located outside the door with the triggering door handle for a passive entry function and located in the passenger compartment for a passive engine start function).
LF receiver 37 preferably includes circuitry for measuring a received signal strength indicator (RSSI) at which the LF wakeup signal is received. The awakened microcontroller 30 stores the RSSI data as part of response data to be sent back to base station 11. Also after being awakened, RF receiver 35 is activated in order to receive an expected challenge signal from base station 11 as part of a conventional challenge/response validation sequence. For example, microcontroller 13 in base station 11 generates a random number to be used as a seed number in a secret mathematical transformation that is also known to microcontroller 30 in fob 12. RF transmitter 16 in base station 11 is used broadcast a UHF challenge signal including the random number. RF receiver 35 in fob 12 receives the UHF challenge signal and microcontroller 30 passes the random number through the known mathematical transformation. The resulting transformed number is included in response data together with the RSSI signal and a fob identifier for inclusion in a UHF response signal broadcast via RF transmitter 32 and antenna 33. The UHF challenge and response signals are sent with a much shorter time delay than if they were sent at the low frequency. The challenge and response may both be sent at 9.6 k baud, for example. The UHF response signal is received by RF receiver 15 via antenna 24 in base station 11 and is processed by microcontroller 13 in a known manner. For instance, microcontroller 13 checks the transformed number as received from fob 12 with its own results of the transformation and determines the UHF response signal to be valid if the transformed numbers match.
Fob 12 and base station 11 also function to provide remote keyless entry functions in a conventional manner. Thus, when a user presses a manual input key (i.e., push button) 31 for a desired remote control function, a UHF control signal incorporating a remote control message having a corresponding function identifier and a pre-assigned fob ID is broadcast. When base station 11 receives a UHF control signal, it validates the fob ID and any security codes and then initiates the remote control function via a vehicle message sent from base station controller 13 to an actuator such as door module 22 or engine controller 26. Typical remote control commands include locking all doors, unlocking a driver's door, unlocking all doors, unlocking a trunk, activating a panic alarm, remotely starting an engine, activating a climate control, deactivating an engine, deactivating a climate control, and requesting vehicle status data to be provided in a UHF status message.
Two-way RKE communication may be initiated by microcontroller 13 automatically after executing certain remote control actions to provide the status data (e.g., engine running status or door lock status) in a UHF status message. The status message is broadcast by RF receiver 15 via antenna 24 to antenna 33 and RF receiver 35 and preferably includes an identifier for properly addressing fob 12 so that information presented by display 36 corresponds to the correct vehicle. The UHF status message may also be prompted by sending a remote control request signal from fob 12.
A preferred method of the invention is shown in greater detail in
After storing response data in step 57 or detecting that no response was received in step 58, the base station sends a second LF wakeup signal with a corresponding antenna ID in step 60 from the second antenna. If the second LF wakeup signal is received by a fob in step 61 then the fob determines RSSI data and the antenna ID in step 62. A UHF challenge signal is sent as shown in step 63 and 64 (although only one challenge signal is sent). If a fob is present, then it determines response data in step 65 and sends a UHF response signal. The base station stores the response data in step 66 or detects the lack of a response in step 67.
A check is made in step 68 to determine whether any valid response was received by a fob. If not, then either the process ends or a batteryless backup procedure may be performed at step 69 as will be described in greater detail in connection with
If the only valid response did not correspond to the first LF wakeup signal, then a check is made in step 72 to determine whether the only valid response was in response to the LF wakeup signal sent from the second antenna in step 72. If so, then the person carrying the fob is known to be located in the region interrogated by the second antenna (i.e., region #2). If the requested passive entry function corresponds to region #2, then it is performed in step 73. If two valid responses were received then a comparison is made in step 74 between the received signal strengths shown by the two responses. If the received signal strength of the first LF wakeup signal is greater then 20 the second RSSI data, then a requested passive entry command for the first region may be performed in step 71, and otherwise a requested passive entry command for the second region may be performed in step 73.
In another alternative embodiment, a challenge and response sequence can be avoided in the event that a fob is not awakened by a particular LF wakeup signal. Thus, a first wakeup signal 84 is sent from a first LF transmitting antenna and if a fob is awakened then an acknowledgement signal 85 is sent by the fob RF transmitter. This acknowledgement message may also include the RSSI data. Thereafter, a UHF challenge signal 86 and a UHF response signal 87 are exchanged. Additional antenna locations may then be polled in a similar manner if desired. If no acknowledgement signal is received after the first wakeup signal, then a second wakeup signal for interrogating a second area can be broadcast immediately.
If no valid responses are received from any LF wakeup signal, it is possible that an authorized fob was in the correct location but that its battery was depleted and the fob was unable to awaken. In order to provide a batteryless backup procedure, a combined two-way RKE/passive entry system having supplemental components as shown in
In view of the foregoing description, the present invention has preserved the short operating range and wakeup capability of a LF system while taking advantage of the higher data rate and resistance to relay attacks of an RF system.
