Method to increase accuracy of locating unit in wireless vehicle system

• US 8,896,418 B2
• Filed: 09/16/2011
• Issued: 11/25/2014
• Est. Priority Date: 09/16/2011
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Lickfelt, Brian K.
• Primary Examiner(s): SYED, NABIL H
• Application Number:
  US13/234,548
• Publication Number:
  US 20130069760A1
• Time in Patent Office: 1,166 Days
• Field of Search: 340/5.61, 340/5.62, 340/5.63, 340/5.64, 340/5.7, 340/5.72, 340/5.32, 340/5.33, 340/5.65, 340/539.11, 340/10.1, 340/10.34, 340/10.4, 340/10.41, 340/10.5
• US Class Current: 340/5.61
• CPC Class Codes: H04B 17/29 Performance testing
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: Y10T 29/49004 including measuring or testing of device or component part

Abstract

A wireless unit for a wireless vehicle system includes a receiver for receiving a vehicle-originating signal, a transmitter for transmitting a reply signal, a received signal strength indicator (RSSI) for determining a received signal strength of the vehicle-originating signal, a memory for storing sensitivity data, and a control unit in electrical communication with the receiver, the transmitter, the RSSI and the memory. The receiver has a sensitivity, and the memory is for storing sensitivity data corresponding to the sensitivity of the receiver. The control unit is configured to communicate with the transmitter to direct the transmitter to transmit the reply signal. The reply signal includes received signal strength data used for determining a distance between the wireless unit and an associated vehicle-side transmitter on an associated vehicle. The received signal strength data is based on the received signal strength and the sensitivity data.

Claims

1. A vehicle passive entry system comprising:

a key fob including

a receiver for receiving a vehicle-originating signal, the receiver having a sensitivity, wherein the sensitivity is based on comparing an expected received signal strength from an LF antenna in a factory controlled environment and a measured received signal strength from the LF antenna in the factory controlled environment;

a transmitter for transmitting a reply signal;

a received signal strength indicator (RSSI) for measuring a received signal strength of the vehicle-originating signal;

a memory storing sensitivity data corresponding to the sensitivity;

a control unit in electrical communication with the receiver, the transmitter, the RSSI and the memory, wherein the control unit is configured to communicate with the transmitter to direct the transmitter to transmit the reply signal, wherein the reply signal includes the measured received signal strength data from the RSSI and the sensitivity data from the memory,

wherein the receiver includes antennas for detecting the vehicle-originating signals in three mutually perpendicular axes, wherein the sensitivity corresponds to an x-axis sensitivity, a y-axis sensitivity and a z-axis sensitivity, and the sensitivity data includes x-axis sensitivity data, y-axis sensitivity data and z-axis sensitivity data; and

a vehicle-side transmitter for transmitting the vehicle-originating signal;

a vehicle-side receiver for receiving the reply signal; and

a vehicle-side control unit in electrical communication with the vehicle-side transmitter and the vehicle-side receiver, wherein the vehicle-side control unit is configured to compensate for the sensitivity unique to the key fob and to determine a distance between the vehicle-side receiver and the key fob based on the measured received signal strength and the sensitivity data in the reply signal.

2. A method for operating a wireless vehicle system comprising:

transmitting a vehicle-originating signal from a vehicle-side transmitter;

receiving the vehicle-originating signal via a receiver on a key fob;

measuring a received signal strength of the vehicle-originating signal;

retrieving sensitivity data from a memory on the key fob;

transmitting a reply signal from the key fob, wherein the reply signal includes the measured signal strength data and the sensitivity data;

receiving the reply signal in a vehicle—

side receiver;

determining in a vehicle—

side control unit a correction factor based on the sensitivity data, wherein the correction factor is a value that compensates for a respective sensitivity of the key fob as compared to a benchmark sensitivity; and

calculating in the vehicle—

side control unit a distance that the key fob is spaced from the vehicle—

side transmitter based on the determined correction factor and the measured signal strength data that was received in the reply signal.

3. A vehicle passive entry system comprising:

a key fob including

a receiver for receiving a vehicle-originating signal, the receiver having a sensitivity based on comparing an expected received signal strength from an LF antenna in a factory controlled environment and a measured received signal strength from the LF antenna in the factory controlled environment;

a transmitter for transmitting a reply signal;

a received signal strength indicator (RSSI) for measuring a received signal strength of the vehicle-originating signal;

a memory storing sensitivity data corresponding to the sensitivity; and

a control unit in electrical communication with the receiver, the transmitter, the RSSI and the memory, wherein the control unit is configured to communicate with the transmitter to direct the transmitter to transmit the reply signal, wherein the reply signal includes the measured received signal strength data and the sensitivity data; and

a vehicle-side transmitter for transmitting the vehicle-originating signal;

a vehicle-side receiver for receiving the reply signal; and

a vehicle-side control unit in electrical communication with the vehicle-side transmitter and the vehicle-side receiver, wherein the vehicle-side control unit is configured to compensate for the sensitivity unique to the key fob and to calculate distance between the fob and the vehicle-side transmitter based on the sensitivity data and the measured received signal strength in the reply signal.