Abstract:
An integrated dead reckoning (DR) and GNSS/INS control system and method are provided for guiding, navigating and controlling vehicles and equipment. A controller generally prioritizes GNSS navigation when satellite signals are available. Upon signal interruption, DR guidance can be integrated with INS to continue autosteering and other automated functions. Exemplary applications include logistics operations where ships, cranes and stacked containers can block satellite signals.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority in U.S. Provisional Application No. 60/016,451, filed Dec. 22, 2007, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to integrated dead reckoning and GNSS positioning, and in particular to applications on cargo-handling logistics equipment. 
         [0004]    2. Description of the Related Art 
         [0005]    Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS), have significantly advanced navigation, machine control and related fields. Accuracy can be significantly improved through the use of differential techniques, which encompass a wide variety of GPS accuracy enhancements, collectively referred to as differential GPS (DGPS). Such systems accurately locate points on a universal coordinate system, which facilitates vehicle and equipment operations. For example, the logistics field includes cargo-handling whereby cargo of various shapes and sizes is loaded, unloaded, stacked and otherwise positioned in and on vehicles and facilities. 
         [0006]    For several decades port operations have been converting to containerized cargo operations. The cargo containers have standardized lengths in different sizes, such as 20, 40 and 45 feet. Container ships account for a large portion of cargo shipping, and are accommodated by automated containerized ports with massive container-handling gantry cranes for loading and offloading operations. Ashore, the containers can be stacked five-high while awaiting ground transport or loading onto container ships. Such vertical storage at containerized ports can create problems with using conventional GNSS guidance because the ships, container stacks and equipment often block the satellite signals. For example, dockside forklifts and gantries often operate within stacks of containers, which can create relatively deep “valleys” from which satellite acquisition and signal lock are often compromised. GNSS navigation requires line-of-site access to the signals of at least four satellites in the constellation. An interruption of such access causes signal loss whereby accurate positioning can no longer be based on GNSS along. Previous systems have used gyroscope-based inertial guidance augmentation for “coasting” until enough GNSS signals are reacquired. However, cargo container handling and other logistics operations may require greater accuracy and more consistency than have previously been available. 
         [0007]    In order to accommodate the position locating needs of the logistics industry generally, and cargo container handling specifically, a relatively high degree of accuracy may be consistently needed. Continuous knowledge of the location of individual containers from being offloaded from the ship by crane, being translocated around the dock area in stacking locations and finally leaving the secured dock area by rail or truck is now a requirement, for security. Positioning input is thus needed from GNSS, inertial (gyroscopic) guidance and dead reckoning sources to match with the container ID at all times. 
         [0008]    Heretofore there has not been available an integrated dead reckoning and GNSS positioning system and method with the advantages and features of the present invention. 
       SUMMARY OF THE INVENTION 
       [0009]    In the practice of the present invention, positioning is accomplished by receiving GNSS location signals, calculating latitude and longitude scale factors, integrating with inertial input from gyroscopes and integrating with dead reckoning input from vehicle wheel sensors. Operating parameters, such as vehicle motion, direction and speed, are sensed and used for selecting and integrating the appropriate positioning input(s) for guidance and other operations. Optical recognition and RFID methods can be utilized in connection with storage and retrieval operations in logistics applications when coupled with this new extended positioning capability. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a block diagram of a dead reckoning, inertial and GNSS-based positioning system embodying an aspect of the present invention. 
           [0011]      FIG. 2  is a plan view of a cargo container port operation involving a container ship, a gantry crane and transport vehicles, which utilizes the positioning system of the present invention in loading and unloading operations.  FIG. 3  is an end elevational view of a gantry crane positioned over a stack of cargo containers. 
           [0012]      FIG. 4  is a side elevational view of a container forklift. 
           [0013]      FIG. 5  is a flow diagram of a positioning method embodying an aspect of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     I. Introduction and Environment 
       [0014]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
         [0015]    Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, up, down, front, back, right and left refer to the invention as oriented in the view being referred to. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Global navigation satellite systems (GNSS) are broadly defined to include GPS (U.S.), Galileo (proposed), GLONASS (Russia), Beidou (China), Compass (proposed), IRNSS (India, proposed), QZSS (Japan, proposed) and other current and future positioning technology using signals from satellites, with or without augmentation from terrestrial sources. Inertial navigation systems (INS) include gyroscopic (gyro) sensors, accelerometers and similar technologies for providing output corresponding to the inertia of moving components in all axes, i.e. through six degrees of freedom (positive and negative directions along transverse X, longitudinal Y and vertical Z axes). Yaw, pitch and roll refer to moving component rotation about the Z, X and Y axes respectively. Said terminology will include the words specifically mentioned, derivatives thereof and words of similar meaning. 
       II. Preferred Embodiment System  2 . 
       [0016]    Referring to the drawings in more detail, the reference numeral  2  generally designates a system embodying an aspect of the present invention, which generally includes a vehicle  4 , a controller  6 , a GNSS signal-receiving input subsystem  8 , a wheel position input subsystem  10  and a vehicle steering subsystem  12 . Without limitation on the generality of useful applications of the control system  2 , the vehicle  4  can be adapted for logistics operations such as storage, retrieval, loading and unloading in conjunction with transportation operations. The controller  6  includes a microprocessor  14 , a graphical user interface (GUI)  16  and data storage  18 , all of which can be provided by a general-purpose computer or a special-purpose programmable logic controller (PLC). A dead reckoning (DR) function is provided at  20  and an INS (gyroscopic) function is provided at  22 . 
         [0017]    The GNSS input subsystem  8  can be mounted remotely from the controller  6 , for example on an elevated mast or other structural component of the vehicle  4 . An example of a suitable GNSS input subsystem is a Crescent A100 Smart Antenna, which is available from Hemisphere GPS LLC of Calgary, Alberta, Canada. The GNSS input subsystem  8  includes one or more antennas  24  connected to a receiver  26  via a filter  28  and a correction function  30 . GNSS signals are received from satellites, an optional central control and an optional real-time kinematic (RTK) source, collectively referred to as a GNSS source or constellation  32 . GNSS positioning data is transmitted from the GNSS input subsystem  8  to the controller  6 , and commands from the controller  6  are received by the GNSS input subsystem  8 . 
         [0018]    The wheel positioning input subsystem  10  utilizes drive shaft encoders  34  for producing an output to the controller  6  corresponding to distance and direction of vehicle travel, providing the necessary inputs for a DR operating mode. The steering subsystem  12  includes autosteer logic  36 , hydraulics  38  and steering linkage  40 . Examples of autosteering systems are shown in U.S. Pat. No. 7,142,956, which is incorporated herein by reference. An hydraulic power source  42  drives the steering hydraulics  38  and a steering wheel  44  provides manual steering input. Electrical power from a source  46  is distributed to the system  2  components and signal distribution is provided via a controller area network (CAN)  45 , or via some other suitable hardwired or wireless (e.g. optical, RF, etc.) distribution. An optional optical character reader  46  provides input to the controller  6 , which can comprise data from barcode and other labels on containers  48 . 
         [0019]      FIG. 2  shows an application of the system  2  in a containerized cargo operation  52  wherein a container ship  54  configured for transporting stacks of cargo containers  48 . A gantry crane  56  is mounted dockside for loading and unloading an adjacent ship  54  from or onto land vehicles, such as tractor-trailer trucks  58 . The gantry crane  56  can be equipped with the system  2  for controlling its operation. For example, the GNSS input subsystem  8  can be mounted on the highest point of the crane structure for maximum satellite signal reception by permitting the antenna  24  to “see” as many satellites as possible. The ship  54  can also be equipped with GNSS capability, including antennas  24  located on either side of the bridge for determining ship attitude and location. 
         [0020]      FIG. 3  shows a mobile, self-propelled crane  62  with the system  2  mounted on an upper part of its structure for maximum antenna  24  exposure. A five-high stack  64  of containers  48  is located in position for the crane  62  to straddle for picking up and depositing containers  48 .  FIG. 4  shows a forklift  66  with the system  2  mounted thereon with antennas  24  and/or receivers mounted on a forklift cab  68  and/or at the top of its mast  70 , which is the highest point of the forklift  66 . The forklift  66  is designed to lift containers  48  sufficiently high to form stacks, such as  64 , of a desired height. 
       III. Integrated Dead Reckoning and GNSS/INS Positioning Method. 
       [0021]      FIG. 5  is a flowchart for a method embodying an aspect of the present invention, which commences at a start  100  and proceeds to an initialization step  102  whereat various operating parameters can be programmed and preset. GNSS (e.g., GPS) signals are acquired at the  106 , enabling calculation of latitude and longitude scale factors at  108 . With the system  2  in motion, the wheel sensors are calibrated one time and the values saved at  110 . A snap dead reckoning (DR) based latitude and longitude (lat/lon) to GPS (lat/lon) step occurs at  112 , i.e. during normal operation with the GNSS input subsystem  8  functional. GPS position, heading and speed are calculated at  114  and INS (gyroscopic) calibration for bias, gain and offset based on GPS heading and speed occurs at  116 . If the wheel sensor  10  detects motion, the gyro heading is updated based on bias and gain. Delta lat/lon values are generated based on wheel sensor and gyro heading inputs at  118 . DR is incremented based on lat/lon values at  120 . Filtered DR based lat/lon to GPS based lat/lon occurs at  122  if GPS is valid. At decision box  124  an affirmative decision indicating GNSS (GPS) mode operating leads to an output at  130  for input to an autosteer control center at  132 . The method then proceeds to the read GPS position, heading and speed step at  114 . As long as the GNSS mode is considered operational, it has an adequate number of tracked satellites and its standard deviation of the solution and geometric dilution of precision and age of differential is low, it can provide primary guidance until the procedure ends at  134 . A negative decision at  124  leads to a dead reckoning (DR) mode decision box  126 , with an affirmative decision leading to the output step  118  and the autosteer control center at  132 . If the DR input subsystem  10  is not functioning (negative decision at  126 ), determined by estimated age since last GPS based calibration, the system  2  determines if the vehicle has stopped at  128 , from which an affirmative decision leads to an end at  134 . 
         [0022]    The operation allows a continuous tracking of the position associated with a container  48 . Depending on the antenna location on the moving vehicle and its heading, an offset from the “new” position can be generated and assigned to the container  48 . On picking up or dropping off the container  48  the container ID information and the container location can be sent to the Central Control station where the data base of all container locations can continuously be updated. If the equipment is not stopped, the method loops back to step  114  for operation in an INS mode until GNSS or DR modes are reacquired. 
         [0023]    The DR mode can maintain relatively accurate guidance during interruptions of GNSS signals, for example when the equipment is located between container stacks or adjacent ships and dockside equipment blocking the satellite signals. Preferably GNSS signals will be reacquired after a short DR “coasting” mode of operation because DR accuracy tends to degrade until “corrected” by a GNSS location fix upon satellite signal reacquisition. The sequence of the method steps, and the steps themselves, can vary according to particular applications of the system  2  and the equipment on which it is mounted. 
       IV. Additional Features and Functionalities. 
       [0024]    The following include additional features and functionalities, which can be incorporated in the system  2  and its operation:
       Updating INS/gyro input subsystem  22 .   Calibrating wheel sensors/encoders  34  during a calibration test. Typically: start calibration; drive straight for approximately  100  meters; and stop calibration.   Calculating latitude (lat)/longitude (lon) scale factors soon after first valid GNSS acquisition.   Calculating internal DR lat/lon values. These are based on integrated average wheel sensor and gyro heading and biased towards valid GNSS lat/lon values when available.   Determine if need to stop updating gyro heading when stopped in DR mode (e.g., no pulses in specified time interval) or below speed cutoff when in GNSS mode, e.g. 1 mph.   Flips in and out of GPS and DR modes depending on criteria TBD, potentially GPS stdev&gt;1 m, sats&lt;6, displays age incremented since value in last GPS mode.   Outputs GGA with differential or DR flags (1 GPS, 2 DIF, 4 RTK, 6 DR) and VTG at 5 Hz   I/O requirements. 2 pulse streams, serial/power to A100, serial to SATTEL Messenger   Will operate with use of SBAS, beacon with the eDrive box, additionally L Dif, and RTK for the next generation product.   For LDif/RTK correctors can be accepted via the Messenger port and sent out to the A100.   Programmable GAP application, saving, loading, downloading of GAP parameters, output of debug data as required.       
 
         [0036]    It is to be understood that the invention can be embodied in various forms, and is not to be limited to the examples discussed above. Other components can be utilized with the present invention.