Abstract:
A global navigation satellite system (GNSS) based control system is provided for positioning a working component relative to a work surface. Inertial measurement unit (IMU) sensors, such as accelerometers and gyroscopes, are mounted on the working component and provide positioning signals to a control compute engine. A method of positioning a working component relative to a work surface using GNSS-based positioning signals is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority in U.S. Provisional Patent Application No. 61/783,973, filed Mar. 14, 2013, which is incorporated herein by reference. U.S. Pat. No. 6,539,303; No. 6,711,501; No. 8,214,111; No. 8,386,129; No. 8,548,649; No. 8,583,315; No. 8,583,326; and No. 8,594,879 are also incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to automated machine control and, in particular, to an agricultural spray boom height control system and method. 
         [0004]    2. Description of the Related Art 
         [0005]    Movable machinery, such as agricultural equipment, open-pit mining machines, airplane crop dusters, and the like all benefit from accurate global navigation satellite system (GNSS) high precision survey products, and others. However, in existing satellite positioning systems (SATPS) for guided parallel and contour swathing for precision farming, mining, and the like, the actual curvature of terrain may not be taken into account. This results in a less than precise production because of the less than precise parallel or contour swathing. Indeed, in order to provide swaths through a field (in farming, for example), the guidance system collects positions of the vehicle as it moves across the field. When the vehicle commences the next pass through the field, the guidance system offsets the collected positions for the previous pass by the width of the equipment (i.e. swath width). The next set of swath positions is used to provide guidance to the operator as he or she drives the vehicle through the field. The current vehicle location, as compared to the desired swath location, is provided to the vehicle&#39;s operator or to a vehicle&#39;s steering system. The SATPS provides the 3-D location of signal reception (for instance, the 3-D location of the antenna). 
         [0006]    Various navigation systems for ground-based vehicles have been employed but each includes particular disadvantages. Systems using Doppler radar will encounter errors with the radar and latency. Similarly, gyroscopes, which may provide heading, roll, or pitch measurements, may be deployed as part of an inertial navigation package, but tend to encounter drift errors and biases and still require some external attitude measurements for gyroscope initialization and drift compensation. Gyroscopes have good short-term characteristics but undesirable long-term characteristics, especially those gyroscopes of lower cost such as those based on a vibrating resonator. Similarly, inertial systems employing gyroscopes and accelerometers have good short-term characteristics but also suffer from drift. Various systems include navigating utilizing GNSS; however, these systems also exhibit disadvantages. Existing GNSS position computations may include lag times, which may be especially troublesome when, for example, GNSS velocity is used to derive vehicle heading. As a result, the position (or heading) solution provided by a GNSS receiver tells a user where the vehicle was a moment ago, but not in real time. Existing GNSS systems do not provide high quality heading information at slower vehicle speeds. Therefore, what is needed is a low cost sensor system to facilitate vehicle swath navigation that makes use of the desirable behavior of both GNSS and inertial units while eliminating or reducing non-desirable behavior. Specifically, what is needed is a means to employ low-cost gyroscopes (e.g., micro electromechanical (MEM) gyroscopes) which exhibit very good short-term low noise and high accuracy while removing their inherent long-term drift. 
         [0007]    Providing multiple antennas on a vehicle can provide additional benefits by determining an attitude of the vehicle from the GNSS ranging signals received by its antennas, which are constrained on the vehicle at a predetermined spacing. For example, high dynamic roll compensation signals can be output directly to the vehicle steering using GNSS-derived attitude information. Components such as gyroscopes and accelerometers can be eliminated using such techniques. Real-time kinematic (RTK) navigation can be accomplished using relatively economical single frequency L1-only receivers with inputs from at least two antennas mounted in fixed relation on a rover vehicle. Still further, moving baselines can be provided for positioning solutions involving tractors and implements and multi-vehicle GNSS control can be provided. 
         [0008]    Providing additional antennas in combination with standard SATPS and GNSS guidance, as mentioned above, along with optional gyroscopes is an effective method to increase GNSS positioning precision and accuracy, such as is described in U.S. Patent Publication No. 2009/0164067, which is assigned to a common assignee and is incorporated herein. However, accuracy and precision can only improve the efficiency of working vehicles, such as those in the agricultural field, to a limited extent. Although such systems are able to track and guide vehicles in three dimensions, including along ridges and sloped-regions, errors may appear in other aspects of a working vehicle. For example, in an agricultural field-working situation where a tractor is towing an implement, the implement may slide on a sloped-region, or the tractor may list to one side or another when entering softer soil or rocky areas. This can happen repeatedly when a vehicle is guided around the same field, regardless of the precision of the guidance system in pre-planning a path. Thus, a system that can detect such changes in uniformity of a field as the vehicle traverses a path and remember those changes can predict and re-route a more accurate and more economical path than a guidance system alone. Heretofore there has not been available a system and method with the advantages and features of the present invention. 
         [0009]    Conventional agricultural spraying operations are carried out over an entire field, everywhere the crop is planted. In contrast, environmental spraying allows the spraying of certain materials which require restrictions in the area of deposition due to potential toxicity or strength. The restrictions can include the distance from waterways and slope of the ground which can affect run-off and concentrations of deposits. 
       SUMMARY OF THE INVENTION 
       [0010]    In the practice of the present invention, position sensors (such as GNSS and IMU) are used to accurately locate the implement (such as a spray boom) with reference to the ground, standing crop, or other field features. Real time compute engine processes control algorithms to compare sensor data with spatial data logged from a previous operation, or terrain model, to make control decisions which maintain desired implement height. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The drawings constitute a part of this specification and include exemplary embodiments of the present invention illustrating various objects and features thereof. 
           [0012]      FIG. 1  is a schematic diagram of a boom height control system embodying an aspect of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     I. Introduction and Environment 
       [0013]    As required, detailed aspects of the present invention are disclosed herein, however, it is to be understood that the disclosed aspects 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 how to variously employ the present invention in virtually any appropriately detailed structure. 
         [0014]    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 orientated in the view being referred to. The words, “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the aspect being described and designated parts thereof. Forwardly and rearwardly are generally in reference to the direction of travel, if appropriate. Said terminology will include the words specifically mentioned, derivatives thereof and words of similar meaning 
       II. Preferred Embodiment 
       [0015]      FIG. 1  is a schematic diagram of a boom height control system  2 . Without limitation on the generality of useful applications of the present invention, the system  2  is shown for controlling the height of a spray boom  20 , which can be used for agricultural applications, such as spraying fertilizer, herbicides, pesticides, water, etc. The control system  2  includes a guidance system  4 , which can be global navigation satellite system (GNSS) based. A real-time control compute engine  6  is connected to the guidance system  4  and can be programmed with specific control instructions and applications, including variable-rate (VR), selective control, guidance, auto-steering, etc. A valve drive  8  can be connected to the compute engine  6  for connection to a steering system of a vehicle, such as a tractor or a self-propelled equipment piece. 
         [0016]    The guidance system is connected to a job set up and graphical user interface (GUI) component  10 , which can include suitable display monitor components. A field template file  12  is provided for specific fields and includes such information as GNSS-defined field coordinates, material prescription information, environmental conditions and equipment routing directions. Geodesic information system (GIS) and cloud (e.g., Internet)  14  data sources and connectivity are provided for communicating bi-directionally with the other components of the system  2 . 
         [0017]    Boom inertial measurement units  16  are connected to the control compute engine  6 , and can include such devices as accelerometers and gyroscopes for measuring inertia and positioning information in three axes (X, Y, Z). The boom  20  can include a GNSS receiver with an antenna  18 , or can be directly controlled via the implement motive component, such as a tractor. The boom  20  includes sections  22 ,  24 ,  26 ,  28 ,  30 , each equipped with its own inertial measurement unit (IMU)  16 . The boom sections can be articulated for conforming to field conditions. 
         [0018]    Use Case:
       1) Field is logged/mapped using highly accurate sensors (such as RTK GNSS) for measurement of field terrain elevations. This may be done as an independent step using an ATV or field truck or data may be used/collected from another farming operation such as harvesting, which covers the same terrain   2) Field log data may be stored in an office/cloud GIS and data management toolset.   3) File is loaded in guidance system on target machine (sprayer, for example).   4) User selects the job file in the guidance system which includes the processed elevation data.   5) The user chooses/sets up boom control options to use the field log including desired height above the target.   6) As the system works across the field, sensor data is compared to elevation data and performs real-time control through a mechanical control system (typically electro-hydraulic or mechanical in nature)       
 
         [0025]    It is to be understood that while certain embodiments and/or aspects of the invention have been shown and described, the invention is not limited thereto and encompasses various other embodiments and aspects.