Patent attributes
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.
