Guidance System and Navigational Aid for Trenchless Construction

BACKGROUND OF THE INVENTION

The present invention generally relates to Jack and Bore and tunneling utilized in trenchless construction operations. As opposed to open cut construction, in trenchless construction line-of-sight locating of the boring or trenchless apparatus is a costly and time-consuming process. While trenchless construction methods are, by themselves, more expensive than open cut construction, trenchless construction provides a number of benefits because it avoids a number of costs associated with open cut construction. These costs include pavement removal and replacement, dewatering, surface restoration, right-of-way or utility acquisition, public inconvenience, lost business revenue arising from road closure or obstruction, reduction of noise and dust, tree removal, etc. In other cases, such as river crossings, lakes, wetlands, etc., trenchless construction provides the only available construction method.

Trenchless construction is employed for the installation of below ground systems for utility applications, including water pipelines, sewer lines, telecommunication cables, electrical cables, and oil/gas pipelines. Jack and Bore, and Tunnel construction may generally be divided into two types, with personnel entry required for the first type and not required for the second type. The type that requires personnel entry must large enough for a man to enter (greater than 24 inches in diameter). The second type is installed without personnel entry. The non-personnel entry can further be divided into 3 subcategories: (1) diameter is too small for human entry; (2) the tunnel has physical limitations to entry (hazardous atmospheres, rescue limitations, etc.), and (3) the construction methods are of the type that personnel entry is not required (hydraulic steerable heads, knuckle heads, microtunnel, etc.).

Hydraulic steerable heads allow the installation crew to adjust the grade (i.e., inclination) of a pipe being installed in a bore hole as well as steer the boring head along a desired line (i.e., azimuth). This ability to control the grade and line may be made from the launch pit by hydraulically activating a steering mechanism, such as external steering resistance pads or windows to change the grade and/or line of the boring head as desired.

A component of a remotely steerable trenchless head system is a type of guidance system which determines the horizontal and vertical positioning of the steerable head and provides that information to the operator on a real time basis. The guidance system may employ various sensors in the steerable head to detect various movements of the steerable head, which these movements are transmitted from the steerable head to a receiver. The receiver may be located either in the launch pit or other convenient location. Of particular importance in the accuracy of the guidance system is the ability of the sensors to detect small movements of the steerable head. If the sensors fail to accurately detect and transmit these movements to the receiver, the resulting error in ascertaining the position of the steerable head can lead to incorrect course corrections and a less than optimal installation.

SUMMARY OF THE INVENTION

The presently disclosed bore guidance system provides a navigational aid to assist an operator in determining the horizontal and vertical positioning of a steerable boring/tunneling head (herein after “steerable head”) as the steerable head is pushed forward below ground by adding lengths of pipe or tunnel segments behind the steerable head. The guidance system may comprise an inertial measurement unit (“IMU”) which contains a plurality of sensors. These sensors provide data to a controller which allows the controller to calculate various positional values of the steerable head and pipe.

An embodiment of the IMU may comprise 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. An embodiment of the bore guidance system may further comprise a transmitter which is configured to receive data from the IMU and transmit it to a controller. The controller compiles and executes an algorithm for calculating vertical and horizontal displacement of the steerable head from the data transmitted from the IMU.

The controller may further comprise a human machine interface (“HMI”) comprising a touch screen which allows an operator to view various operational parameters during the boring operation and make changes to user-configurable features of the controller's software.

One set of sensors available for utilization in an embodiment of the IMU are XYZ axes temperature compensated MEMS (micro-electro-mechanical system) accelerometers, which the controller uses to calculate the pitch and roll of pipe as well as sudden up/down/left/right/non-angular shifts. These accelerometers are mounted directly to the circuit board stack within the IMU.

Another set of sensors available for utilization in an embodiment of the IMU are XYZ axes fiber optic gyroscopes which detect angular rotation about their respective axes. The IMU may be configured to internally integrate the raw degrees per second since the last scan, which may occur at a baud rate of 9600, or about once every 0.08 seconds.

Another set of sensors available for utilization in an embodiment of the IMU are XYZ axes magnetometers, which are used internally by the IMU to assist in stabilizing the random angle walk and drift of the fiber optic gyros.

The IMU may also have a plurality of temperature sensors which are configured to provide a current temperature reading of the internal components of the IMU. Internal temperature sensors also assist in stabilizing the data from the MEMS Accelerometers.

The guidance system may also use a device to determine the linear distance of the steerable head from the launch pit as the steerable head is pushed forward by adding lengths of pipe or tunnel segments. An example of an acceptable device is a rotary encoder having a 5000-count push/push digital output shaft configured to send digital outputs to the controller. Half staggered high/low digital outputs may be utilized to indicate the amount of movement and related velocity. Another digital output may be utilized to indicate the direction of motion (clockwise or counterclockwise).

The encoder may be attached to two linked knurled anodized wheels which keep the encoder centered on the curved surface of the pipe and prevent slippage. The wheels may be 12 inches in circumference, which makes each incremental motion of the encoder equal to 1/5000 foot. An encoder arm may be attached to a two-axis pivot system and a spring arm to maintain positive pressure against the pipe during small lateral shifts of the pipe and self-correct for less than perfect perpendicular alignment between the encoder wheels and the pipe. The encoder and arm assembly may be encased in a box to protect them from falling dirt, sparks, and welding slag during the boring operation. The box may be attached to an adjustable jack which is attached to a stationary structure which does not move with the pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of an IMU disposed on a plate which sits below the top resistance pad/window of an annulus formed within a steerable head.

FIG. 2 shows the components of a rotary encoder which is configured to detect minute linear movements of the pipe.

FIG. 3 shows the rotary encoder of FIG. 2 with the components set within a protective case.

FIG. 4 shows the protective case of FIG. 3, with the wheel side disposed against an exterior side of a pipe with an attachment assembly attached on one end to the protective case and the other end of the attachment assembly attached to a shoring member of the bore pit.

FIG. 5 shows the front panel of an embodiment of a controller which may be utilized with embodiments of the present invention.

FIG. 6 shows the interior of an embodiment of the controller shown in FIG. 5.

FIG. 7 shows a close view of an automation controller which may be utilized in the control panel.

FIG. 8 shows an HMI start up screen.

FIG. 9 shows HMI Setup Screen 1: pipe parameters.

FIG. 10 shows HMI Setup Screen 2: design parameters.

FIG. 11 shows HMI Setup Screen 3: actual starting parameters.

FIG. 12 shows HMI Setup Screen 4: accelerometer calibration.

FIG. 13 shows an HMI lead joint screen.

FIG. 14 shows an HMI initial parameters screen.

FIG. 15 shows an HMI gyro calibration screen.

FIG. 16 shows an HMI home screen.

FIG. 17 shows an HMI working screen 2.

FIG. 18 shows an HMI window pressures screen.

FIG. 19 shows an HMI data log history screen.

FIG. 20 shows an HMI settings screen.

FIG. 21 shows an HMI line check data log screen.

FIG. 22 shows an HMI water level data log screen.

FIG. 23 shows an IMU with gyro and accelerometer axis orientation.

FIG. 24 shows the IMU Internals with 3 detached fiber optic gyros.

FIG. 25 shows another angle of the IMU Internals with 1 detached fiber optic gyro.

DETAILED DESCRIPTION

Referring now to the figures, FIG. 1 shows an embodiment of an inertial measurement unit (“IMU”) 100 of the presently disclosed guidance system installed to a steerable head 10. IMU 100 may be screwed to a plate 102 which sits beneath the top window 104 of the steerable head 10. The IMU 100 may be utilized on any steerable head 10 so long as there is sufficient room to house and protect it. The IMU 100 is user configurable through a developer's kit which accompanies the guidance system. The developer's kit allows a user to define the baud rate and data format.

FIGS. 24-25 show detailed views of the circuit boards 2401, 2501 which are contained within the protective housing of the IMU 100. Circuit boards 2401, 2501 may be in a stacked configuration and contain accelerometer chips and magnetometer chips. Digital circuitry within the IMU internally processes the data from the respective sensors and transmits it over a wired digital signal to control panel 1010 and ultimately to the controller 1012 where the inertial navigation algorithm is executed. The IMU may transmit multiple data points through different sensor configurations including the following:

One set of sensors available for utilization in an embodiment of the IMU 100 are XYZ axes temperature compensated MEMS accelerometers located on circuit board stacks 2401, 2501, data from which the controller 1012 may use to calculate the pitch and roll of pipe as well as sudden up/down/left/right/non-angular shifts. FIG. 23 shows accelerometer axes 2303. Under static conditions (i.e., the bore is not moving forward), pitch and roll may be calculated from data provided by the accelerometers. Pitch and roll may be calculated using a filtered average of their respective angles using an XYZ rotation matrix model as well as a YXZ rotation matrix model. The averaged values may then put through a low pass filter with a 0.25 sec. filtered average duration. Roll in a static state may be provided simply for user reference but it is not used in any part of the navigational positioning algorithm calculations. However, the roll measurement is calculated from data provided by the accelerometers.

Another set of sensors which may be utilized in an embodiment of the IMU 100 are XYZ axes fiber optic gyroscopes 2402, 2502 which detect angular rotation about their respective axes 2302. The IMU 100 may be configured to internally integrate the raw degrees per second, which may occur at a baud rate of 9600, or about once every 0.08 seconds. Under dynamic conditions (the bore moving linearly forward), embodiments of the present invention have the ability to save accelerometer pitch at the start of each linear movement. During dynamic linear movement conditions, the controller 1012 is able to add readings from the gyros 2402, 2502 to its saved accelerometer pitch values. At the conclusion of each moving condition, the controller 1012 performs a zero-velocity update, ignores the gyro input data, and resumes determining pitch strictly from the accelerometers. The gyro angular measurement is more stable under dynamic conditions because it is not susceptible to vibrations and/or linear accelerations which are detrimental to the stability of accelerometers.

Another set of sensors available for utilization in an embodiment of the IMU 100 are XYZ axes magnetometers, which are used internally by the IMU to assist in stabilizing the random angle walk and drift of the fiber optic gyros and located internally to the circuit board stack 2401, 2501 within the IMU 100. Changes in yaw are gravitationally neutral, which means accelerometers cannot be used to detect yaw angular shift. However, yaw may be detected with a Z-axis fiber optic gyro. Because gyros have an inherent angle random walk (drift), embodiments of the present invention may minimize the involvement of gyros in angular calculations. Non-manned entry trenchless excavations cannot change angular heading (yaw) when not moving linearly forward. Therefore, an embodiment of the system only sums changes in yaw if the algorithm detects linear movement. The fiber optic gyros of the IMU 100 may be stabilized from angle random walk by internally stabilizing the data with a magnetometer. In addition, the fiber optic gyros may be calibrated to further reduce angle random walk at the outset of the boring operation.

Embodiments of the invention may be configured so that calibration of the fiber optic gyros is performed immediately before the vertical and horizontal displacement portions of the algorithm become active and immediately after the user inputs initial vertical and horizontal displacement readings. Calibration takes place over a user-defined duration. The inventors herein have found that ten minutes provides a satisfactory calibration period. The IMU 100 should be maintained in a still state during calibration, with the IMU subjected to no linear or angular movement or vibrations. Calibration is a 3-stage process, where each stage lasts ⅓ of the total calibration time.

Calibration Stage 1: Records and totals every yaw change received by the IMU (approximately 2500 readings for stage 1 of a ten-minute test). At the end of stage 1, the total yaw/number of scans is calculated to determine an average yaw change.

Calibration Stage 2: Records and totals (yaw-stage 1 average yaw change) for approximately another 2500 readings. At the end of Stage 2, total corrected yaw/number of stage 2 scans is calculated to further refine the average yaw change reading.

Calibration Stage 3: Repeats Stage 2 using refined average yaw change. At the conclusion of Stage 3, the average yaw reading is refined a third time. The end of Stage 3 concludes the calibration process.

After calibration, every yaw change indicated by the Z-axis gyro will have the yaw calibration factor subtracted from it. This results in a near zero yaw change with every IMU scan in a stationary state.

The IMU 100 may also have a plurality of temperature sensors which are configured to provide a current temperature reading of the internal components of the IMU and assist in stabilization of the MEMS accelerometers.

The IMU 100 will typically communicate on an RS-422 full duplex serial communication protocol which ensures readable data is provided with each scan of the controller. Communication with the controller is asynchronous. Scan time of the controller is approximately 0.006-008 seconds. A Baud rate of 9600 provides a new packet of data every 0.08-0.10 seconds. The controller syncs its receipt of an IMU data packet with its calculation of vertical and horizontal displacement. The controller 1012 streams 36-byte serial data packets from the IMU 100, parses out what it intends to measure, and saves it as separate variables. At the conclusion of this process, the controller 1012 takes the variables it just imported and applies the algorithm to generate the calculated vertical and horizontal displacements.

FIGS. 2-4 show an embodiment of a linear motion sensor 200. The linear motion sensor 200 may utilize a rotary encoder 202. The rotary encoder 202 may be a 5000-count push/pull digital output shaft that sends three digital outputs to controller 1012. Two half-staggered high/low digital outputs may be utilized to indicate the amount of movement and the velocity of the movement. A digital output may be used to indicate the direction of motion (counterclockwise vs. clockwise).

The rotary encoder 202 may be attached to wheels 204. The wheels 204 may be two linked wheels having a knurled anodized configuration. The wheels 204 keep the encoder 202 centered on the curved surface of the pipe 12 and prevent slippage. The wheels 204 may be twelve inches in circumference which makes each incremental motion of the above-described encoder 202 equal to 1/5000 ft. The encoder 202 may be attached to a 2-axis pivot system 206 by encoder arm assembly 208. The 2-axis pivot system 206 and a spring arm maintain positive pressure of the wheels 204 against the pipe 12 during small lateral shifts of the pipe and self-correct for a less than perfect perpendicular alignment between the encoder wheels 204 and the pipe. The encoder 202 and arm assembly 208 may be encased in box 210 to protect them from falling dirt, sparks, and welding slag during bore construction. As shown in FIG. 4, the box 210 may be attached with an attachment assembly 212 which may be attached to a stationary point, such as a shoring member of the bore pit, that does not move with the pipe 12.

The controller 1012 may be configured to record scaled distance values from the encoder 202 and compares the value every scan for 0.25 seconds. A default value may be utilized to recognize a state of motion if any movement is detected during those 0.25 seconds which, for embodiments of the encoder 202, may be a minimum of 0.0002 ft. Vibrations, grinders, and impacts to the pipe with tools can fool the algorithm into detecting linear motion, so embodiments of the controller may have a user-defined sensitivity setting. The controller 1012 may be configured so that every time the encoder sensitivity is decreased, the threshold for what the algorithm defines as a state of motion increases by 0.0002 ft above the default. This means the encoder 202 will have to rotate slightly further before the algorithm triggers a state of motion. During a state of motion, vertical and horizontal displacement calculations are performed, and angular changes can be detected by the fiber optic gyros.

The controller 1012 may be configured such that during a state of motion, the controller continues to compare scaled distance values over 0.25 second intervals. If it detects no difference in scaled distance values (or if it detects a value less than the user-defined threshold), the algorithm will remove the controller from a state of motion and return it to a stopped state. At the beginning of a stopped state, pitch undergoes a zero-velocity update, and returns to being calculated only from the filtered accelerometer values as described above. Yaw changes are not totaled during a stopped state.

FIGS. 5-7 shows an embodiment of an enclosure comprising a control panel 1000 and internal components which may be utilized with embodiments of the guidance system. Control panel 1000 may have a human machine interface (HMI) 1002 which has a touch screen which allows a user to view key parameters of the system and to make changes to user-configurable features of the software of the controller 1012 housed within the enclosure. The HMI 1002 will typically be configured so that it does not provide any control logic or decision-making capacity to the operator. Each virtual button on the screen simply turns on/off a virtual digital output and the controller 1012 utilizes its stored algorithms to decide what to do with an observed condition. As shown in FIG. 6, HMI 1002 may connect to the circuitry of the controller 1012 by an ethernet connection 1008 and a Local Area Network contained within the enclosure.

Control panel 1000 may have an exterior power switch 1004. Control panel 1000 may also have exterior up/down/left/right indicator lights 1006 which are connected to digital outputs on the controller 1012 and illuminate when the bore deviates more than a specified amount from the intended design line and grade, such as 0.10 foot. The controller 1012 may further comprise a 120-volt power output to provide power to other electronic equipment in the bore pit. The controller 1012 may further comprise an RJ45 data port to allow a programmer or analyst to diagnose and make changes in the firmware of the controller 1012 and the HMI 1002.

As shown in FIGS. 5-7, the components of the control panel 1000 are housed within an enclosure 1010. Those components include controller 1012 which may be an Automation Direct BRX Bx-DM1E-18ED23-D processor or comparable. This device hosts firmware for running algorithms which calculate vertical and horizontal displacement based upon values provided by: (1) external HSIO Card (BX-HSIO-1) 1014 which processes data from the rotary encoder 202; and (2) external serial card (BX-SERIO-4) 1015 which processes asynchronous RS-422 Serial communication from received input from the IMU 100. Controller 1012 may also receive input from the HMI 1002 and process and apply user input settings. Controller 1012 may also send variable values to the HMI 1002 for display.

Enclosure 1010 may also house a DC power supply with 120 VAC input voltage which supplies power to the controller 1012, as well as the HMI 1002 and all sensors. The components may also include fused overcurrent protection for all electrical components and terminal blocks and wiring junction points. Enclosure 1010 may further contain an ethernet switch which allows Local Area Network ethernet communication between the controller 1012, the HMI 1002 and an external laptop or digital device for updating firmware.

HMI 1002 allows the operator to view the current vertical and horizontal displacement of a bore compared to a user-defined “Design Grade” (the desired slope of the bore). HMI 1002 further allows a user to define how often the horizontal and vertical offset data should be logged onto an SD card. This feature allows an operator to provide project management, owner, engineer and/or regulatory authorities with an as-built spreadsheet (.csv file) of exactly where the bore was positioned throughout its construction. HMI 1002 allows the user to define measurement thresholds for the sensors. For example, if linear measurements are fluctuating from welders vibrating the pipe by alignment and welding operations, the sensitivity of the encoder 202 can be turned down such that the algorithm uses a greater threshold of movement to define “linear motion”. For example, the default value may be set at 1/5000 ft, and the sensitivity can be turned down in 1/5000 ft increments. The user can also define what level of rotational detection defines an “angle change” for calculating horizontal and vertical displacement. The user can elect to ignore small angular changes which are determined to result from factors other than an actual angle change, such as electrical anomalies or sensor variation.

Control panel 1000 may be placed in the bore pit, such as in a hanging position or mounted to a power pack for the steerable head 10. The control panel 1000 may be situated in a manner which makes the HMI screen 1002 visible to the operator.

FIGS. 8-22 show a variety of screens for HMI 1002. FIG. 8 shows the HMI start up screen. Selecting the “start new bore” virtual button 812 erases saved variables and sends a user to the start-up sequence which is reflected in FIGS. 9-15. Selecting the “continue bore” virtual button 814 sends a user to the home screen shown in FIG. 16. HMI 1002 utilizes a plurality of virtual buttons, each having an accompanying display which shows the value of a particular variable.

FIG. 9 shows HMI Initial Job Setup Screen 1. This screen allows the user to set certain variables about the project that become integral to the known location calculations as well as the sensor-based position estimation that can be completed throughout the bore. The user can define the pipe outside diameter using virtual buttons on display 901. The distance from the front of the pipe to the target lights of the steering head 902 are later used for right/left alignment measurements. Virtual button 903 for (“Outside Edge of Pipe to Center of Lights”) 903 allows the user to define the radial offset distance of the target lights from the outside edge of the pipe in inches (or other user defined dimension). This variable is integral in determining roll correction, or amount of right or left alignment deviation resulting from circumferential rolling of the target lights when the measurement is taken using a theodolite. Virtual button 904 (“Wall Thickness” allows the user to define the wall thickness of the pipe in inches (or other desired dimension) which is used to calculate the pipe's bend radius. Virtual button 905 (“Continue”) saves the user defined variables and takes the user to the next screen.

FIG. 10 shows the HMI Design Parameters screen, which allows the user to define key parameters of the bore's design. These parameters may or may not reflect the actual starting parameters, as bore distances, grades, and start elevation can be altered due to conditions discovered in the field before the bore is launched. Virtual button 1050 (“Bore Distance”) allows the user to define the intended length of the bore in feet (or other desired dimension) as shown on the plans. Virtual button 1051 (“Intended Start Elevation”) allows the user to define the surveyed elevation at which the bore is designed to start, typically taken from a known survey hub elevation on the project reflecting feet (or meters) above sea level. Virtual button 1052 (“Intended Start Grade”) allows the user to define the design grade at which the bore is to be installed according to the plans and specifications of the project. This unit of measurement is in percentage of slope, a common industry standard unit of measure for grade. Virtual button 1053 (“Save”) saves the variables defined on this screen to a uniquely named .csv file on SD card 1016 and takes the user to the next screen. Virtual button 1054 (“Prev. Screen”) takes the user to the prior setup screen.

FIG. 11 shows the HMI Starting Parameters screen. These values default to the values defined in FIG. 10. Ideally, bores start out at the parameters at which they were designed; however, conditions in the field such as variations in pit depth, existing utilities conflicts, power lines, or traffic obstructions can alter the starting elevation, grade, and receiving pit location (length) of the bore. In the event variables differ from the design reflected, the screen shown in FIG. 11 allows the user to enter actual observed values. Virtual button 1101 (“Actual Distance”), virtual button 1102 (“Lead Joint Elevation”) and virtual button 103 (“Lead Joint Grade”) allows a user to change these variables in the event any of these values differ from what was designed on the plans. The actual start elevation inputted with virtual button 1102 and the actual start grade inputted with virtual button 1103 are obtained by the contractor's own measurements prior to starting the bore. The virtual “Save” button on FIG. 11 saves these variables to a uniquely named .csv file on SD card 1016 and takes the user to the next setup screen. The virtual “Prev Screen” button takes the user to the prior screen.

FIG. 12 shows the HMI Grade and Roll calibration screen. This screen calibrates the tilt values from the accelerometers to account for slight variations to the orientation of the sensors within the steerable head 10. Upon activation of this screen, virtual displays “Grade % (IMU)” 1201 and “Grade % (Rieker)” 1203 show the raw grade % reading from the accelerometers in the IMU 100 and a Rieker tilt sensor respectively.

After the “Calibrate Grade” virtual button 1206 is pressed, these values are calibrated to the “Actual Start Grade” displayed at virtual button 1103 as defined by the user for the screen depicted in FIG. 11. Virtual displays “Roll (IMU)” 1202 and “Roll (Rieker)” 1204 show the amount of circumferential right/left roll (in degrees) that the tilt sensors are experiencing. Initially, these values are raw values from the sensor with a calibration factor default value of 0. When the Calibrate Roll virtual button 1205 is pressed, these values will be calibrated to 0.0 degrees. Virtual displays Grade % (Rieker) 1203 and Roll (Rieker) 1204 show data from a redundant sensor. Pressing virtual button 1207 (“Save”) saves and logs these calibrated values and their respective calibration factors to a uniquely named .csv file on SD card 1016 and take the user to the next screen. Pressing virtual button 1208 (“Prev Screen”) will take the user to the prior screen.

FIG. 13 shows the “Lead Joint” HMI screen displayed during installation of the first/lead joint of bore pipe. During installation of the lead joint of pipe, there is typically vertical and horizontal variation which is significant enough to impact the accuracy of the algorithms utilized within the controller 1012. Therefore, during the installation of the lead joint of pipe and during the time this screen is displayed, the vertical and horizontal displacement calculations are not performed. After the first length of pipe has been inserted into the bore, the steerable head 10 and the IMU 100 are “locked in” by the surrounding soil and are not subject to potentially inconsistent and/or inaccurate readings.

The Lead Joint HMI screen has virtual display 1301 showing the current footage of pipe inserted into the bore as determined by linear motion sensor 200. This screen may also have virtual display 1302 which shows the calibrated grade based on the values established by virtual buttons 1206 and 1103 on the previous HMI job setup screens and derived from the IMU 100. Virtual button 1303 (“Enter Setup”) allows a user to progress to the next screen in the setup process. Virtual button 1304 (“Prev. Screen”) allows a user to return to the prior screen.

FIG. 14 shows an HMI Initial Vertical and Horizontal offset screen. Once sufficient lengths of pipe have been bored into the ground to lock in the steerable head 10 and produce stable data from the IMU 100, the user can input initial horizontal and vertical offset measurements. These two values can be input any time the user desires the positioning algorithm to start calculating the bore's elevation and alignment. This typically occurs after installation of the lead joint of pipe. The values defined on this screen serve as the starting “known reference point” for the positioning algorithm. After inputting these initial values, the algorithm will calculate subsequent vertical/horizontal offset changes based on angle changes detected by the IMU 100 and the linear distance measured by encoder 202.

Virtual button 1401 (“Up/Down”) is used by the user to indicate whether vertical displacement from the bore has increased or decreased from the starting value. Virtual button 1402 (“Left/Right”) is used by the user to indicate whether horizontal displacement is to the right or to the left of the centerline. Virtual display 1403 (“Water Level Reading”) provides the current offset elevation of the pipe as compared to the original elevation of the pipe as defined by a water level, measured in 0.01 foot increments. Virtual display 1404 (“Line Offset”) provides the lateral shift in the steerable head 10 from the intended bore line. The measurement is currently taken using a theodolite, plumb bob, and rearward facing target lights on the steerable head 10.

Virtual buttons 1405, 1406 are used to increase or decrease the observed offset measurements by increments of 0.01 foot. Virtual button 1407 (“Continue”) saves the initial vertical and horizontal offset values into a uniquely named .csv file on SD card 1016 and sends the user to the next screen. Virtual button 1408 (“Prev. Screen”) takes the user to the previous screen.

FIG. 15 shows HMI Gyro Calibration Screen. This screen is the last in the series of initial job setup screens. Within IMU 100 are three fiber optic gyroscopes, one for each orthogonal axis of rotation (XYZ) Such gyroscopes are subject to a phenomenon known as “angle random walk.” Angle random walk leads to a drift in the angular reading over time on a stationary gyroscope, which can result in loss of accuracy and reliability. The impact of angle random walk can be reduced by primarily two ways. The first way is by minimizing the time that gyroscope angular data is used to calculate rotational angle changes. The second way is by “calibrating” the gyroscopes. The HMI Gyro Calibration Screen allows a user to calibrate the gyroscopes before the devices start assisting in calculating angular orientation. The calibration process utilizes a simplified version of the Allen Variance method for Error Estimation in inertial sensors.

Virtual button 1501 starts the calibration process. Virtual button 1502 allows a user to stop calibration if the IMU 100 has been subjected to movement or vibration during calibration. Virtual button 1503 allows the user to define the length of the calibration time. The inventors herein have determined that a ten-minute motionless calibration time is appropriate. Virtual display 1504 displays the elapsed minutes since the calibration was initiated. Virtual button 1505 allows angle resetting. Virtual button 1506 takes the user to the prior screen in the series.

After calibration has been completed as described above, the user is taken to the HMI home screen as shown in FIG. 16. Once this screen is reached, the vertical and horizontal displacement algorithm in the controller 1012 is active. This screen includes up/down/left/right virtual displays 1601 which display the bore displacement in the respective directions as calculated by the algorithm. This screen further includes virtual status indicator 1602 which is only visible if the bore deviates more than 0.05 feet in any intended line and grade, at which point the red status indicator appears over the corresponding direction of deviance from design parameters. This screen further includes virtual display 1603 which shows the linear distance of pipe which has passed encoder 202 since the start of the bore. This screen further includes virtual display 1604 which shows the calibrated grade as calculated by the controller 1012 based upon data provided by IMU 100. At any point during the bore, the user can choose to take and record an actual elevation and/or line measurement. These measurements serve to re-establish and refresh the last known point in space for the navigational algorithm. After a revised Line Check and/or Water Level measurement, the navigational algorithm calculates and estimated point in space based on this most recent last known position. Virtual button 1607 takes the user to a line check screen. Virtual button 1608 takes the user to a water level measurement input screen. At the top of the HMI home screen depicted in FIG. 16 is a top navigational bar 1606 which allows a user to navigate to different screens.

FIG. 17 shows the second informational HMI screen available to users from the top navigational bar 1606, 1701. Virtual Display 1702 displays uncalibrated, “raw” grade from the Rieker tilt sensor in % grade. Virtual Display 1703 displays uncalibrated, “raw” roll (in degrees) from the Rieker tilt sensor. The Rieker 2-axis tilt sensor has been used in beta testing as a confidence test for the IMU 100 data. Virtual Display 1704 shows the last recorded Elevation Difference as determined by the last water level measurement. This number (in 0.01 ft increments) is the difference between the intended/design elevation at the current point in the bore and the last recorded elevation of the water level. Virtual Display 1705 displays the current linear footage of bore pipe installed as determined by the rotary encoder 202. Virtual button 1706 starts/stops a continuous data logging of pitch & roll changes onto the SD card 1016 inserted into the Controller 1012. When this virtual button is toggled “on,” pitch & roll data from the IMU 100 are saved on the controller 1012 SD card approximately every 0.08 seconds until the button is toggled “off.” Virtual display 1707 indicates how many data sets have been logged. Virtual display 1708 indicates how many of said data sets have contained a change in pitch & roll. Virtual display 1709 displays the temperature of the IMU 100 circuitry in degrees Fahrenheit.

FIG. 18 shows the HMI Window Pressures screen and is the third informational HMI screen available to users from the top navigational bar 1606, 1801. These 4 virtual displays (1802, 1803, 1804, 1805) show the current pressure (in psi) within each of the four hydraulic circuits controlling the corrective windows of the steerable head 10. Each virtual display is a scaled display of a 4-20 mA analog signal from a 0-5000 psi pressure transducer plumbed into each hydraulic circuit. The values of each of these virtual displays are periodically recorded on the controller's 1012 SD card 1016 throughout the bore and can be valuable to the operator in determining the effects of corrective measures to change the line and/or grade of the pipe.

FIG. 19 shows the Data Logging History HMI screen, and is the fourth informational HMI screen available to users from the top navigational bar 1606, 1901. The virtual displays in the first column 1902 show the linear bore distance recorded in the most recent (8) data logs on the SD card 1016 to the controller 1012. The virtual displays in the second column 1903 show the right/left line deviation estimation (in 0.01 ft increments) recorded in the eight most recent data logs on the SD card 1016 to the controller 1012. The virtual displays in the third column 1904 show the deviation from intended grade (in 0.01 ft increments) recorded in the eight most recent data logs on the SD card to 1016 the controller 1012. This number is the difference between the intended elevation change at the corresponding linear distance of bore installed and the actual elevation change based on the most recent water level reading and the calculated estimation of the positioning algorithm since the last recorded point of known elevation. Virtual button 1905 allows the user to define the linear distance interval at which data is logged and saved to the SD card on the controller 1012. The default value for data log interval is 0.10 ft, meaning that at every 0.10 ft of linear distance as recorded by the encoder 200, a series of data points including the ones displayed in FIG. 19 are recorded to a .csv file on the SD card on controller 1012. Virtual momentary button 1906 (“Manual Data Log”) allows the user to log this set of data points manually, and can be utilized at the point where the bore crosses a critical utility or any other important point on the project where bore conditions should be recorded.

FIG. 20 shows an HMI screen in which various miscellaneous parameters can be changed by the user and is the fifth available screen available to users from the top navigational bar 1606,2001. Virtual button 2002 allows users to set the time interval at which variables are updated on the HMI screen. Default value is 1 second, which reduces fluctuations in the data that can be faster than the user's brain can process. Virtual display 2003 contain information about yaw values obtained from IMU 100. Virtual momentary button 2004 resets the maximum and minimum yaw recorded by the Controller 1012 since the start of the bore. Virtual display 2005 shows the current yaw value stored in the controller 1012 and obtained by the z axis fiber optic gyroscope in the IMU 100. Virtual display 2006 displays the highest value for yaw compiled by the controller 1012 since the bore started. A positive yaw correlates to a left turn in the alignment of the pipe. Virtual display 2007 displays the lowest value for yaw compiled by the controller 1012 since the bore started. In practical application, a “negative” yaw correlates to a right turn in the alignment of the pipe.

Box 2008 contains user configurable variables related to bottom window pressure and its varying ability to correct the vertical angle of travel of the pipe. Each diameter of steerable head 10 has a unique low threshold pressure, indicated at virtual display 2009, at which the hydraulic pressure applied to the bottom window will “pick up” the head off the bottom of the bore hole in an amount equal to a relief band welded onto the leading edge of the steering head. Though this increases that grade angle recorded by the IMU 100, this increase in grade angle does not correlate to an upward trajectory of travel, which results in the pipe traveling at a grade angle that is less than what is recorded by the IMU 100. This phenomenon necessitates the use of a “grade correction factor”, indicated at virtual display 2011, that is unique to the size of the pipe and the hydraulic pressure applied to the bottom window. At a certain “High Threshold” bottom window pressure, indicated at virtual display 2010, the steering head 10 will begin cutting into the soil above it, allowing the pipe to travel at a grade angle that is consistent with the IMU reading. This “High Threshold” pressure 2010 is dependent in large part on the size of pipe and the wall thickness of the pipe. Within the controller 1200 is a database of “Low Threshold” values 2009, “High Threshold” values 2010, and “Grade Correction Factor” values 2011. The controller 1012 calls default values for these variables from the database based on user-defined pipe diameter 901 determined in FIG. 9. The values displayed in virtual display 2008 depict these default values. The user can override these default values by using virtual buttons 2009, 2010, and 2011. Overriding the default values may be necessary in changing soil conditions/hardnesses.

Box 2012 shows parameters for sensitivity of encoder 200. Virtual display 2013 shows the current sensitivity stored in controller 1012. A higher sensitivity correlates to a higher degree of motion from encoder 202 that defines a state of “motion” by the inertial navigation algorithm. Each increment of encoder 202 translates to 1/5000 ft (0.0002 ft) of linear movement. These increments can fluctuate with vibrations on, impacts to, or the effects of power tools being used on the pipe. The default value for encoder sensitivity as reflected in virtual display 2013 is 0.0004 ft (4 increments of the encoder). The user can utilize virtual buttons 2014 to change the sensitivity of what constitutes a condition of linear motion or restore to its default value using virtual button 2015.

Box 2016 contains parameters used to complete an “averaging” mathematical model for navigational positioning. In this model, grade and yaw numbers provided by the IMU 100 are averaged over a set distance, and the positioning algorithm executes once at the conclusion of that set distance. Virtual display 2017 shows the current interval upon which the averaging algorithm executes. Virtual buttons 2018 allow the user to increase/decrease the length of the averaging interval. Virtual display 2019 shows a count of how many times the averaging interval has been completed since the start of the bore.

Virtual display/virtual button 2020 allow the user to change the resolution of the data from the fiber optic gyroscopes in IMU 100. This number allows the navigational algorithm to ignore compiling miniscule changes to the angles provided by the gyroscopes. Angular changes below this resolution number are not compiled into the calculation of total angle. Virtual display 2021 shows the calibration factor that was determined by the controller 1012 when the gyroscopes were calibrated at the start of the job.

FIG. 21 is the screen visible when the user taps the virtual button 1607 (“Line Check”) on the Home Screen in FIG. 16. The line check screen of FIG. 21 is used to establish a new known point of right/left deviation from intended bore alignment. At the conclusion of the data provided by the user in the screen displayed in FIG. 21, the navigational algorithm will continue its estimate of right/left from this last known point. Steerable head 10 has rearward facing target lights that can be viewed from the bore pit by using a theodolite. During a line check, the user Zero's the theodolite on the intended line/azimuth of the bore. The user will then rotate the theodolite right or left and focus in on the rearward facing target lights of the steerable head at the leading edge of the bore. The theodolite will provide an angular measurement in degrees/minutes/seconds. It is up to the user to use this angle, combined with a known distance from the theodolite to the lights, and determine the amount of right/left movement from intended line.

The screen shown in FIG. 21 assists the user in making the calculation to determine right/left movement. In box 2101, the user uses virtual buttons 2103 to adjust the value of virtual display 2102, which corresponds to the distance from the theodolite instrument to the linear distance sensor 200. Box 2104 contains virtual displays 2105, 2107, and 2109 which display degrees, minutes, and seconds respectively. The degrees/minutes/seconds values displayed by the theodolite are input by the user into the controller 1012 by using virtual buttons 2106, 2108, and 2110 respectively.

A line measurement can either be magnified or minimized by the amount of roll experienced by the pipe at the point of measurement. For example, if a pipe is rolled to the right/clockwise when viewed from the bore pit, the target lights (which normally appear at top dead center of the pipe) will appear further to the right than the actual top dead center of the pipe. The calculations performed by controller 1012 account for this. Virtual display 2112 displays the amount of the right/left movement of the lights due to the roll being detected by the IMU 100. This value is also dependent on the pipe diameter 901 input by the user on the screen in FIG. 9. Virtual Lights 2114 appear to indicate to the user whether this roll is to the right or left.

Virtual display 2114 shows the results of the calculations performed by controller 1012. This calculation uses the user input angle measurement using virtual buttons 2106, 2108, and 2110. It also uses total bore distance 1705 as determined by the encoder 202, distance from front of the pipe to the target lights 902 as determined in FIG. 9, and the distance displayed in virtual display 2102. Virtual display 2115 is compensated by the amount of roll displayed in virtual display 2112. This figure is the new known right/left line deviation that the navigational algorithm uses as a basis for estimating subsequent right/left movements. Virtual lights 2117 appear to indicate whether the bore is right or left of the intended alignment. Virtual button 2113 (“Back”) takes the user back to the home screen displayed in FIG. 16. Virtual button 2116 (“Save”) saves all values input by the user during the current check to the SD card 1016 in controller 1012 and returns the user to the home screen displayed in FIG. 16.

FIG. 22 is the screen visible when the user taps virtual button 1608 (“Water Level”) on the HMI home screen in FIG. 16. It displays a water level screen used to establish a new known point of up/down elevation. The controller 1012 compares the new elevation to the elevation that the bore should be at given a known distance as determined by the linear motion sensor 200 and based on the intended bore grade as defined by the user in the Design Parameters Set Up Screen in FIG. 10. At the conclusion of the data provided by the user in the screen displayed in FIG. 22, the navigational algorithm will continue its estimate of up/down movement and compare that estimation to the intended elevation at a given linear distance of travel.

The Water Level measurement box 2201 contains virtual display 2202 and virtual buttons 2203. The user uses virtual buttons 2203 to input the current water level elevation compared to the initial water level elevation at the start of the bore. Current bore distance as determined by the linear motion sensor 200 is displayed on virtual display 2204. Virtual display 2207 shows the results of the calculations performed by the controller 1012 and is the difference between the current elevation of the lead edge of the bore and the elevation that it should be given a user defined “Intended Grade” 1052 and intended start elevation 1051. Virtual lights 2206 illuminate if the bore is higher or lower than its intended elevation at the current distance traveled. The virtual displays visible in column 2209 display the bore distance at which the eight most recent user input water level readings occurred. Virtual displays in column 2210 show the eight most recent elevation difference calculations that occurred at those distances. If the user taps virtual button 2205 (“Back”), the HMI reverts returns to the home screen shown in FIG. 16. If the user taps virtual button 2208 (“Save”), the results of the current water level determination and the current distance are saved into a .csv file in the controller 1012. The user is then taken back to the home screen FIG. 16.

FIG. 23 shows the embodiment of the IMU 100 in an illustration 2301. It shows the orientation of the fiber optic gyroscope axes 2302 as well as the accelerometer axes 2303.

FIGS. 24 and 25 show a disassembled IMU 100. The three fiber optic gyroscopes 2402 are connected to the circuit board stack 2401 via ribbon cables. While inside the IMU housing, the fiber optic gyroscope modules are mounted and oriented such that they match the rotational axes 2302 depicted in FIG. 23. On the circuit board stack 2401 are the accelerometer chips, magnetometer chips, temperature sensors, as well as all necessary components to process raw signals from the various sensors, stabilize the data, and transmit it as digital data packets to the control panel 1000 and ultimately the controller 1012. FIG. 25 shows a different angle of the same circuit board stack 2501 with (2) of the (3) Fiber Optic Gyroscope modules 2502 disconnected.

Guidance System and Navigational Aid for Trenchless Construction

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Provisional Applications (1)