Local positioning system for automated lawn mowers

• US 8,027,761 B1
• Filed: 07/18/2008
• Issued: 09/27/2011
• Est. Priority Date: 09/04/2007
• Status: Expired due to Fees

• Current Assignee: Russell G. Nelson
• Original Assignee: Russell G. Nelson
• Inventors: Nelson, Russell G.
• Primary Examiner(s): Zanelli; Michael J.
• Application Number:
  US12/218,825
• Time in Patent Office: 1,166 Days
• Field of Search: None
• US Class Current: 701/23
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: G01S 1/805 the synchronised signals being pulses or equivalent modulations on carrier waves and the transit times being compared by measuring the difference in arrival time of a significant part of the modulations
• CPC Class Codes: G01S 11/14 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G05D 1/0255 using acoustic signals, e.g. ultra-sonic singals sonar systems designed for anti-collision purposes G01S15/93
• CPC Class Codes: G05D 1/0276 using signals provided by a source external to the vehicle involving a plurality of vehicles G05D1/0287; automatically controlling vehicle speed responsive to externally generated signals B60K31/0058

Abstract

An improved local positioning system (10) utilizing two fixed sonic transmitters (16A,16B) and an omni directional audio receptor (20) mounted on an automated lawn mower (12). Distance between each audio transmitter and the mower is measured by transmitting an RF trigger pulse (88) from the mower to each of the sonic transmitters. Upon being triggered, the first transmitter (16A) sends out an audio pulse which is received by an audio sensor, condenser microphone (22) and the time it takes is measured by a counter (62). Likewise the second transmitter (16B) is later triggered and the time it takes that pulse to be received is measured by the counter (62). The counts are converted to distances and the x-y coordinate which is the location of the mower is calculated by simple trigonometry. The location data which is relative to the sonic transmitters (16A,16B) is available to the microprocessor computer board (72) which utilizes the information to output control signals to a steering and control interface (74). A temperature sensor (76) is also read by the computer to adjust the distance calculation according to those conditions. With the location information, the computer (72) can be programmed to record a path as the mower (12) moves by manual remote control or operate in automatic mode to follow a previously recorded path.

Claims

1. A locating system for providing location data to an automated lawn mower comprising:

(a) a first sonic transmitter configured to generate a sonic pulse in response to receipt of a first characteristic of a radio frequency signal transmitted from said lawn mower;

(b) a second sonic transmitter configured to generate a sonic pulse in response to receipt of a second characteristic of said radio frequency signal transmitted from said lawn mower;

(c) a radio frequency transmitter on said lawn mower configured to produce a radio frequency signal to be received by said sonic transmitters;

(d) a sonic pulse sensor on said lawn mower capable of detecting a sonic pulse transmitted from each of said sonic transmitters;

(e) a counter coupled to said sonic pulse sensor to determine the time of travel of each of said sonic pulses;

(f) a temperature sensor for providing ambient temperature;

(g) a processor connected to said counter and said temperature sensor to calculate lawn mower x-y coordinates from input data provided by said counter and said temperature sensor; and

(h) a data output connected to said processor for providing temperature corrected location data to said lawn mower;

wherein said first sonic transmitter includes a positive edge detector of said radio frequency signal and said second sonic transmitter includes a negative edge detector of said radio frequency signal.

2. The locating system of claim 1 wherein said radio frequency signal transmitted from said lawn mower is modulated by an analog frequency-shift keyed signal.

3. A method of determining the location of an automated lawn mower comprising the steps of:

(a) providing a plurality of sonic transmitters placed a certain distance apart at an area of lawn to be mowed and configured to be triggered by different characteristics of a modulated radio frequency signal transmitted from said automated lawn mower;

(b) sequentially triggering said sonic transmitters with said modulated radio frequency signal transmitted from said automated lawn mower, wherein the first of said sonic transmitters is triggered by the rising edge of said modulated radio frequency signal and the second of said sonic transmitters is triggered by the falling edge of said modulated radio frequency signal;

(c) individually measuring the time of flight of sonic pulses between each said sonic transmitter and said automated lawn mower;

(d) measuring ambient temperature to determine accurate distances corresponding to time of flight of each sonic pulse; and

(e) calculating location coordinates relative to said sonic transmitters with values adjusted for ambient temperature;

whereby temperature corrected location coordinates are available at said automated lawn mower for recording or for automated operation.