Guidance System and Navigational Aid for Trenchless Construction

Abstract

A bore guidance system for a steerable head for boring or tunneling has an inertial measurement unit having a plurality of sensors which provide data to a controller which allows the controller, utilizing a variety of algorithms to calculate various positional values of the steerable head and pipe. One set of the sensors utilized in the bore guidance system are XYZ axes fiber optic gyroscopes. The bore guidance system may also utilize XYZ axes temperature compensated MEMS accelerometers which the controller utilizes, among other things, to calculate pitch and roll of the pipe. The bore guidance system may also utilize XYZ axes magnetometers to assist in stabilizing the random angle walk and drift of the fiber optic gyroscopes. The bore guidance system may also utilize a device for tracking linear distance traveled of the pipe such as a rotary encoder.

Having thus described the preferred embodiment of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following: 
     
         1 . A navigational guidance system for a steerable head for trenchless construction, the guidance system comprising:
 an inertial measurement unit comprising a plurality of fiber optic gyroscopes comprising a first fiber optic gyroscope configured to measure a rotational change about an x axis, a second fiber optic gyroscope configured to measure a rotational change about a y axis, and a third fiber optic gyroscope configured to measure a rotational change about a z axis;   a transmitter configured to receive data from the inertial measurement unit; and   a controller connected to the transmitter, the controller comprising an algorithm for calculating vertical and horizontal displacement of the steerable head from the data received from the transmitter.   
     
     
         2 . The guidance system of  claim 1  wherein the inertial measurement unit comprises a plurality of temperature compensated MEMS accelerometers comprising a first MEMS accelerometer configured to detect acceleration in the x axis direction, a second MEMS accelerometer configured to detect acceleration in the y axis direction, and a third MEMS accelerometer configured to detect acceleration in the z axis direction, wherein the controller is configured to calculate pitch and roll of the steerable head from the accelerations detected by the plurality of temperature compensated MEMS accelerometers. 
     
     
         3 . The guidance system of  claim 1  wherein the inertial measurement unit comprises a plurality of magnetometers configured to detect a change in magnetic field about the x axis, the y axis and the z axis, wherein the plurality of magnetometers stabilize a plurality of measurements made by the plurality of fiber optic gyroscopes. 
     
     
         4 . The guidance system of  claim 1  further comprising a rotary encoder configured to transmit a plurality of digital outputs to the controller, wherein the controller utilizes the plurality of digital outputs to determine a linear distance traveled by the steerable head. 
     
     
         5 . The guidance system of  claim 1  further comprising a human machine interface connected to the controller, the human machine interface configured to display a current vertical displacement and a current horizontal displacement of a bore. 
     
     
         6 . The guidance system of  claim 5  wherein the human machine interface is configured to display a design grade of the bore for comparison to the current vertical displacement and current horizontal displacement of the bore. 
     
     
         7 . The guidance system of  claim 5  wherein the human machine interface comprises a plurality of virtual buttons which are configured to input a value for a desired bore distance, a value for an intended start elevation, and a value for an intended start grade. 
     
     
         8 . The guidance system of  claim 1  wherein the controller is configured to calibrate the first fiber optic gyroscope, the second fiber optic gyroscope and the third fiber optic gyroscope. 
     
     
         9 . The guidance system of  claim 1  wherein the controller is configured to adjust a resolution value for the first fiber optic gyroscope, the second fiber optic gyroscope and the third fiber optic gyroscope. 
     
     
         10 . The guidance system of  claim 4  wherein the controller is configured to adjust a sensitivity value for the rotary encoder.