Abstract:
A system and method for interrupting a Global Navigation Satellite System (GNSS)-based automatic steering mode of a hydraulic steering system on a vehicle. When a steering wheel is manually turned by an operator, pressurized hydraulic fluid from a steering directional control valve activates an interrupter having an interrupter valve. The interrupter valve blocks pressurized fluid flow to the automatic steering system, thus overriding automatic steering and giving the operator full manual steering control via the steering wheel. The hydraulic interrupt system is mechanical with no electronic elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority in U.S. Provisional Patent Application No. 61/919,366, filed Dec. 20, 2013, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to vehicle steering, and in particular to a hydraulic safety interrupter for automatic steering (“autosteer”) systems, which can use sensors including Global Navigation Satellite System (GNSS), and other guidance and navigation receivers and equipment. 
     2. Description of the Related Art 
     A. GNSS-Based Vehicle Guidance Background 
     The use of sensors for automating vehicle guidance and machine control has significantly advanced these fields and enabled a number of applications, including many in agriculture, transportation and other industries. For example and without limitation, GNSSs are commonly used for guidance, navigation and machine control. GNSSs include the Global Positioning System (GPS) and other satellite-based systems. Various GNSS receivers are available for aviation, marine and terrestrial vehicles. The GNSS information provided by such receivers can be processed and used for navigation. In more sophisticated systems, vehicle guidance can be automatically controlled using such information. For example, a predetermined travel or flight path can be programmed into an on-board computer. The vehicle guidance system can automatically maintain appropriate course parameters, such as course, heading, speed, altitude, end-of-row U-turns, etc. Control system, feedback theory, and signal filtering techniques can be used to interactively anticipate (with higher order systems) and compensate for course deviations and navigation errors. Such sophisticated autopilot and automatic steering systems tend to involve powerful computers and complex flight and steering controls integrated with manual controls. 
     Accurate vehicle guidance and equipment control are important objectives in agricultural operations generally and agricultural equipment specifically. For example, cultivating, tilling, planting, spraying, fertilizing, harvesting and other farming operations typically involve specialized equipment and materials, which are operated and applied by making multiple passes over cultivated fields. Ideally, the equipment is guided through accurately-spaced passes or swaths, the spacing of which is determined by the swath width of the equipment. 
     GNSS technology advanced the field of agricultural guidance by enabling reliable, accurate systems which are relatively easy to use. GNSS guidance systems are adapted for displaying directional guidance information to assist operators with manually steering the vehicles. For example, the Outback steering guidance product line was developed primarily for agricultural applications. Current GNSS-based products include the Outback S3, the eDrive TC and the eDrive X™ which are available from Outback Guidance (www.outbackguidance.com) and are manufactured by AgJunction, Inc. (www.agjunction.com) of Hiawatha, Kans. These products are covered by U.S. Pat. No. 6,539,303 and U.S. Pat. No. 6,711,501, which are incorporated herein by reference. They include on-board computers which can be programmed for steering vehicles through various straight-line and curved (“contour”) patterns. An advantage of this system is its ability to retain field-specific cultivating, planting, spraying, fertilizing, harvesting and other patterns in memory. This feature enables operators to accurately retrace such patterns. Another advantage relates to the ability to interrupt operations for subsequent resumption by referring to system-generated logs of previously treated areas. 
     The OUTBACK S™ GNSS guidance system provides the equipment operators with real-time visual indications of heading error with a steering guide display and crosstrack error with a current position display. They respectively provide steering correction information and an indication of the equipment position relative to a predetermined course. Operators can accurately drive patterns in various weather and light conditions, including nighttime, by concentrating primarily on such visual displays. Significant improvements in steering accuracy and complete field coverage are possible with this system. 
     Another type of GNSS vehicle guidance equipment automatically steers the vehicle along all or part of its travel path and can also control an agricultural procedure or operation, such as spraying, planting, tilling, harvesting, etc. Examples of such equipment are shown in U.S. Pat. No. 7,142,956, which is incorporated herein by reference. U.S. Pat. No. 7,437,230 shows satellite-based vehicle guidance control in straight and contour modes, and is also incorporated herein by reference. 
     GNSS guidance systems and equipment are distinguished by their vehicle path configuration capabilities. Initially, straight-line AB (i.e., between points A and B) guidance consists of multiple, parallel straight lines, which are separated by the swath widths of the vehicles. Straight line AB guidance is ideally suited for rectangular fields and continuously-repeating, parallel swathing. 
     Non-rectangular and terraced fields typically require curvilinear vehicle paths that follow the field perimeters and the terraced elevation contours. Contour guidance systems and methods were developed to accommodate such field conditions using GNSS coordinates to define curvilinear vehicle paths. See, for example, Korver U.S. Pat. No. 5,928,309. GNSS positions can be logged on-the-fly at intervals of, for example, 0.20 seconds. Contour guidance can be accomplished by computer-generating each subsequent pass from the GNSS-defined previous pass and a user-entered swath width. 
     Another type of GNSS contour guidance equipment outputs guidance signals relative to the edges of all previously logged swaths. Such logged swaths typically correspond to field areas where operations, e.g. spraying, have already been carried out. See, for example, U.S. Pat. No. 6,539,303 and U.S. Pat. No. 6,711,501, which are assigned to a common assignee herewith and are incorporated herein by reference. 
     Automatic steering accommodates “hands-off” operation, taking into account vehicle operating parameters, such as turning radii, speeds, swath widths, etc. Appropriate machine control functions, such as implement steering and spray boom control, can also be automated. 
     B. Manual-Automatic Steering Interface 
     Although agricultural operations have utilized robotic equipment without human operators on-board, standard practice is to provide an operator with the ability to override the automatic steering system. For example, some automatic steering systems will disengage when operator input, e.g., via steering wheel, is sensed. On-board computers can detect such manual turning inputs and issue appropriate output commands for disengaging auto-steering functions. GNSS-guided automatic steering can be accomplished with hydraulic valve blocks retrofit on existing vehicles, or installed as original equipment in new vehicles. GNSS receivers provide positioning and navigation data, which can be processed by on-board microprocessors for steering and other vehicle control functions. An advantage of the present invention is to provide a hydraulic steering interrupter which is manually-activated and is independent of the automated, computerized steering controls. Heretofore there has not been available a hydraulic steering interrupter with the advantages and features of the present invention. 
     SUMMARY OF THE INVENTION 
     In the practice of the present invention, an interrupter is provided for a hydraulic steering system on a vehicle, which can utilize GNSS-based auto steering. The interrupter is preferably positioned upstream of an auto-steering hydraulic valve block, and activates automatically when a steering wheel is manually turned by the operator. The interrupter senses a pressure signal from the vehicle manual steering and interrupts (i.e., blocks) pressurized hydraulic fluid flow to the automatic steering input valve, thus canceling the automatic steering command and giving the operator full manual steering control via the steering wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vehicle, such as a tractor, equipped with a hydraulic interrupter in a GNSS-based automatic steering system, embodying an aspect of the present invention. 
         FIG. 2  is a block diagram of a closed center steering system including a hydraulic interrupter embodying an aspect of the present invention. 
         FIG. 3  is a block diagram of an open center steering system including a hydraulic interrupter comprising an alternative aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     I. Introduction and Environment 
     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. 
     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. Said terminology will include the words specifically mentioned, derivatives thereof and words of similar meaning. 
     Without limitation on the generality of useful applications of the present invention, a hydraulic interrupter  21  is provided in a steering control system  2  on a vehicle  1 , which can comprise a tractor equipped with a Global Navigation Satellite System (GNSS)  13 . The GNSS system  13  includes a receiver  5  which can be connected to a pair of antennas  9  for vector directional guidance in a horizontal plane based on differencing the signals received at the respective antennas  9 . Such directional guidance techniques are used for obtaining a vehicle heading in an X-Y (horizontal) plane, even with the vehicle stationary. A guidance central processing unit (CPU)  7  is connected to the receiver  5  for processing the GNSS positioning signals and outputting guidance signals to the steering control system  2  for auto-steering the vehicle  1 . The vehicle  1  can also be equipped with a tow-behind implement, which can also be provided with GNSS-based control interfacing with the vehicle steering control system  2 . For example, implement-steering can provide advantages in certain agricultural and other operations. 
     II. Closed Center Embodiment Steering Control System  2   
     The steering control system  2  embodying the present invention can be installed in various vehicles with manual controls, such as a steering wheel  8 , and an electric-hydraulic power steering subsystem  4  for assisting manual steering and for primarily steering the vehicle in automatic guidance operating modes (i.e., “auto-steer”). The electric-hydraulic steering subsystem  4  is adapted for coupling to a guidance system, such as the GNSS-based guidance system  13  described above. The steering subsystem  4  includes a hydraulic interrupter  21  with an interrupter valve  22  adapted for manually overriding or interrupting the electric-hydraulic steering subsystem  4  and returning control to an operator via the steering wheel  8 . The power steering subsystem  4  can be hydraulic, electric-over-hydraulic, pneumatic, etc. 
     The steering control system  2  includes a steering directional control valve  6  connected to the steering wheel  8 . A steering priority valve  10  connects the steering directional control valve  6  to a pump  11  mounted on the vehicle  1 . In an embodiment of the present invention, the steering directional control valve  6  has a “closed center” configuration ( FIG. 2 ). A load sense line  15  extends from the steering directional control valve  6  to a load sense shuttle valve  24  and the steering priority valve  10  via a “T” connection  25 . The load sense line  15  activates the interrupter valve  22  by detecting or “sensing” greater hydraulic pressure from the steering directional control valve  6  signaling an operator turning a steering wheel  8  and thus manually taking over the vehicle steering. An “override” condition thus occurs, interrupting the automatic steering operation by interrupting the hydraulic fluid flow to the proportional flow control directional valve  18 . 
     Hydraulic lines  12  connect the steering directional control valve  6  to respective right and left load holding valves  14 R,  14 L, which are adapted for maintaining certain fluid pressure levels in the electric-hydraulic power steering subsystem  4 . The system  4  steers the vehicle  1  via a double-acting hydraulic cylinder  28 , which can link directly to the vehicle steering gear. A shuttle valve  16  is positioned between the load holding valves  14 R,  14 L. A proportional flow control directional valve  18  receives a constant flow of hydraulic fluid via a pressure compensating valve  20 . The pressure drop across the compensating valve  20  is maintained relatively constant. The interrupter valve  22  is located between the pressure compensating valve  20  and an enabling valve  26 , which is solenoid-activated by the GNSS-based steering subsystem  4 . The interrupter valve  22  is spring-loaded for maintaining an open position until an override closes it or blocks pressure flow to the auto-steering subsystem  4 . Such an override signal originates with the steering priority valve  10  at the T connect  25 , which acts on a load sense shuttle valve  24 . The load sense shuttle valve  24  provides an input to the pump  11  for varying the displacement as necessary to accommodate the steering system loads. For example, in the configuration shown, the load sense shuttle ball would move to the right ( FIG. 2 ) for manual steering. In an automatic steering mode (i.e., enable valve  26  open), the ball would be in the left position. Hydraulic fluid is pumped from and returned to a tank  17  having a check valve  29 . 
     III. Open-Center Alternative Embodiment Steering Control System  102  (FIG.  3 ) 
     An open-center steering control system  102  comprising an alternative embodiment of the present invention is shown in  FIG. 3 . The open center hydraulic circuit utilizes a continuous flow of hydraulic fluid, which is returned to the tank  117  through an “open center” of a steering directional control valve  106  connected to and controlled by a steering wheel  108 . The control system  102  includes an auto-steer subsystem  104 , a steering priority valve  110 , a pump  111 , and hydraulic lines  112 , which have similar functions to the corresponding components described above. An interrupter valve  122  is provided for interrupting the fluid flow like the interrupter valve  22  described above. A “T” connector  125  supplies fluid to a pressure compensating valve  120 . An enable valve  126  connects to the interrupter valve  122 . A hydraulic interrupter  121  comprises the interrupter valve  122  and other components connected thereto for interrupting pressure flow to the auto-steer subsystem  104  when the steering wheel  108  is moved. A check valve  129  extends between lines connecting a pressure side of the circuit and a return to the tank  117 . Excess flow EF from the hydraulic interrupter valve  122 , which occurs because of the open center configuration, can be returned to the tank  117 . 
     The system  102  also includes left and right load holding valves  114 L,  114 R, which connect to respective sides of the steering piston-and-cylinder unit  128 . A shuttle valve  116  connects the fluid inlet sides of the load holding valves  114 L,  114 R. A proportional flow control valve  118  is connected to the load holding valves  114 L,  114 R and to a directional valve  123 . 
     IV. Conclusion 
     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. For example, various other types of sensor systems can be utilized in conjunction with hydraulic systems with the advantages and features of the hydraulic interrupter valve discussed above.