Patent ID: 6364028
Filing Date: 2002-04-02
Classification: E02F,G01S

Abstract:
A control system for establishing grade and elevation control for a tool of a construction apparatus and for maintaining the vertical position of the tool relative to a reference, the tool being carried by the construction apparatus, and the construction apparatus including at least one positioning device that responds to signals from said control system to adjust the position of the tool, said control system comprising:a first ultrasonic transducer configured to be carried by the construction apparatus, said first transducer transmitting and receiving acoustic waves; at least one reflector; a second ultrasonic transducer configured to be carried by said construction apparatus and spaced a distance from said first ultrasonic transducer, said second transducer receiving acoustic waves, and said reflector spaced from said second transducer a distance less than said distance between said transducers whereby said reflector is at least in close proximity to said second transducer; a controller coupled to said first and second ultrasonic transducers, said controller driving said first and second transducers to produce an acoustic wave and monitoring the time reflections of the acoustic wave are respectively received by said first and second transducers; and said controller determining the local speed of sound based on a first in time reflection received by said second ultrasonic transducer from said reflector and determining the distance from the construction tool to a reference based on the local speed of sound and a second in time reflection received by both of said first and second ultrasonic transducers, said controller producing at least one electrical signal as a function of the distance of said ultrasonic transducers from the reference.