Intrusion detection system

• US 4,991,146 A
• Filed: 11/30/1989
• Issued: 02/05/1991
• Est. Priority Date: 11/30/1989
• Status: Expired due to Fees

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Ransdell, Bill J., Phelan, James J.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Pihulic, Daniel T.
• Application Number:
  US07/443,684
• Time in Patent Office: 432 Days
• Field of Search: 367/909, 367/93, 367/98, 340/903, 364/461
• US Class Current: 367/98
• CPC Class Codes: G01S 15/04 Systems determining presence of a target
• CPC Class Codes: G01S 15/526 by comparing echos in different sonar periods
• CPC Class Codes: G01S 7/523 Details of pulse systems short-range imaging G01S7/52017; methods or devices for transmitting, conducting or directing sound G10K11/18
• CPC Class Codes: G08B 13/1618 using ultrasonic detection means
• CPC Class Codes: Y10S 367/909 Collision avoidance

Abstract

A microprocessor-based ultrasonic intrusion detection system includes an initialization mode wherein a plurality of echoes are cumulatively processed to produce a reference or signature data set representing the area to be monitored without intruding objects. Later received echoes are compared to this signature so that an intruding object will cause generation of an alarm signal. Time varying thresholds are utilized to compensate for attenuation caused by increased distance.

Claims

1. A system for detecting intrusions into an area to be monitored, the system comprising:

means for periodically directing a transmit signal into the area so that a plurality of echo signals will be reflected from objects intruding into the area;

means for receiving echo signals reflected by an object or objects in the area;

means for generating a signature data array derived by cumulatively processing an initial set of signature echo signals, the means for generating a signature data array comprising means for generating and storing an initial signature data array having a plurality of data bits corresponding to segments of the echo signals, and means for comparing each signature echo signal segment to a signature threshold value and for replacing a corresponding initial data bit value with a flag value if said segment exceeds the threshold value; and

means for comparing non-signature data representing non-signature echoes received after reception of said signature echo signals to the signature data array and for generating an alarm signal when the non-signature data differs from signature data.

2. The invention of claim 1, further comprising:

means for reducing the signature threshold value as a function of time.

3. A system for detecting intrusions into an area to be monitored, the system comprising:

means for periodically directing a transmit signal into the area so that a plurality of echo signals will be reflected from objects intruding into the area;

means for receiving echo signals reflected by an object or objects in the area;

means for generating a signature data array derived by cumulatively processing an initial set of signature echo signals;

means for comparing non-signature data representing non-signature echoes received after reception of said signature echo signals to the signature data array and for generating an alarm signal when the non-signature data differs from signature data; and

means for comparing non-signature echo signal segments to a non-signature threshold value and ignoring segments which do not exceed said non-signature threshold.

4. The invention of claim 3, further comprising:

means for comparing each signature echo signal segment to a signature threshold value and for replacing a corresponding initial data bit value with a flag value if said segment exceeds the threshold value; and

means for generating an alarm signal each time a non-signature echo signal segment exceeds the non-signature threshold value and no flag value is present in an corresponding portion of the signature data array.

5. The invention of claim 3, further comprising:

means for reducing the non-signature threshold value as a function of time.