Abstract:
An automatic leveling system for a vehicle supporting an articulable boom system. The automatic leveling system uses a microprocessor to monitor various inputs indicative of the current position of the vehicle and generates electrical drive signals to control the amount of extension of various outriggers extending from the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     None. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a device for leveling a base of a boom and conveying pipeline of a fire truck. More particularly, it relates to a device for deploying outriggers and extending them an appropriate distance such that the boom and pipeline is gravitationally level. 
     One type of fire-fighting device utilizes an articulable boom and conveying pipeline to manipulate the dispensing point of a quenching agent strategically with respect to the source of a fire. An example of such a fire-fighting system is disclosed in U.S. patent application Ser. No. 09/393,464 filed Sep. 10, 1999 by Burch, et al. entitled “Fire-fighting System Having Improved Flow,” which is assigned to Schwing America, Inc., the assignee of the present application and is hereby incorporated by reference. Concrete pumping trucks also often operate using an articulable boom for placement of the concrete dispensing point. For safe operation of these types devices, it is important that the vehicle be level. More specifically, the turret or base supporting the maneuverable booms must be gravitationally level. If the turret is not gravitationally level, the boom sections may experience slew (i.e., rotation about a vertical axis) and may undesirably move into an unsafe position or cause damage to the boom or conveying pipeline. 
     Systems known in the prior art performed gravitational leveling of the turret by manually adjusting the position and force supplied by the outriggers extending from the fire truck. This method, however, was difficult and inefficient as it required an operator to manually move to the site of the outrigger and adjust its position and then return to the fire truck to check level. Manual leveling is an iterative process that can be difficult and time consuming. There is a need in the art for an automatic leveling system for leveling the base of a boom of a fire-fighting vehicle to ensure safe operation. 
     BRIEF SUMMARY OF THE INVENTION 
     An automatic leveling system for a vehicle used to support an articulable boom and pipeline is disclosed. The automatic leveling system includes outriggers extending out from the vehicle and having a foot that is vertically adjustable with respect to the vehicle. It also includes components for individually adjusting the vertical position of the feet. A tilt sensor is used to sense the position of the vehicle with respect to gravitational level along two coplanar orthogonal axis. A microprocessor is used for receiving signals and calculating the slope of the vehicle with respect to level. The microprocessor also generates a drive signal to drive the components for individually adjusting the vertical position of the feet to level the vehicle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a fire-fighting vehicle in accordance with the present invention. 
     FIG. 2 is a perspective view of one of the outriggers according to the present invention. 
     FIG. 3 is a top plan view of the fire-fighting vehicle as shown in FIG.  1 . 
     FIG. 4 is a block schematic of the components of the auto leveling system of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a perspective view of a fire-fighting system  10  according to the present invention. The fire-fighting system  10  includes a truck  12 , a boom  14 , a conveying pipeline  16 , and a nozzle  18 . The truck  12  acts as a support or a base for the boom  14 . The boom  14  supports and articulates the conveying pipeline  16 . The truck  12  provides the ability for the fire-fighting system  10  to be mobile and transported to a location near the vicinity of the fire. The boom  14  and the conveying pipeline  16  function to allow the dispensing point of a quenching agent (such as water or a fire retardant chemical foam) to be located near the fire source. The quenching agent is dispensed through the nozzle  18 , which is mounted at the outermost end of the boom  14 . Although the preferred embodiment, as shown in FIG. 1, shows the fire-fighting system  10  having a boom  14  and conveying pipeline  16  mounted on the truck  12 , in other embodiments the boom  14  and conveying pipeline  16  may be mounted on a stationary support structure. 
     The truck  12 , as best shown in FIGS. 1 and 3, includes a chassis  20 , front outriggers  22   l ,  22   r , rear outriggers  23   l ,  23   r , a tank  24 , a pump  26 , and a boom base  28 . The chassis  20  of the truck  12  provides the main structural support for supporting the boom  14  and the conveying pipeline  16 . The front outriggers  22   l ,  22   r  and rear outriggers  23   l ,  23   r  extend laterally from the chassis  20  and impose a downward force on the surrounding ground. The front outriggers  22   l ,  22   r  and rear outriggers  23   l ,  23   r  function to stabilize the truck  12  and prevent it from tipping during deployment of the boom  14  and conveying pipeline  16 . The tank  24  holds a supply of the quenching agent used to suppress or quench the fire. The quenching agent may also be supplied by a source external to the truck  12 . The pump  26  acts to move quenching agent from the tank  24  or external source through the conveying pipeline  16  and out the nozzle  18 . The base  28  provides a surface for mounting the boom  14 . The boom  14  includes a turret  30 , a first boom section  32 , a second boom section  34 , a third boom section  36 , a first actuator assembly  38 , a second actuator assembly  40 , and a third actuator assembly  42 . 
     The turret  30  of the boom  14  is mounted to the base  28  of the truck  12 . The turret  30  allows rotatable motion, about a vertical axis, of the boom  14  with respect to the truck  12 . As shown in FIG. 1, a proximal end of the first boom section  32  is pivotally coupled to the turret  30 . A distal end of the first boom section  32  is pivotally connected to a proximal end of the second boom section  34 . A distal end of the second boom section  34  is pivotally connected to a proximal end of the third boom section  36 . Although the preferred embodiment shown in FIG. 1 includes three boom sections, the boom  14  could include any number of boom sections. 
     As further shown in FIG. 1, the first actuator assembly  38  is connected between the turret  30  and the first boom section  32 . The first actuator assembly  38  extends or retracts to control the angular position of the first boom section  32  with respect to the truck  12 . The second actuator assembly  40  is coupled between the first boom section  32  and the second boom section  34  and controls the angular position of the second boom section  34  with respect to the first boom section  32 . The third actuator assembly  42  is coupled between the second boom section  34  and the third boom section  36  and controls the angular position of the third boom section  36  with respect to the second boom section  34 . An operator of the fire-fighting system  10  can control the position of the distal end of the third boom section  36  by controlling the position of the turret  30 , the first actuator assembly  38 , the second actuator assembly  40 , and the third actuator assembly  42 . The position of the distal end of the third boom section  36 , which is where the nozzle  18  is located, determines the dispensing point of the quenching agent. 
     The fire-fighting system  10  of the present invention allows an operator to manipulate the actuators  38 ,  40 ,  42  and strategically position the nozzle  18  for maximum fire-fighting efficacy. To safely deploy and position the nozzle  18  by manipulating the boom sections  32 ,  34 ,  36  with respect to one another, it is important that the boom base  28 , supporting the turret  30 , is approximately gravitationally level. The boom base  28  must be within three degrees offset from gravitational level along any axis through a center point. If the boom base  28  (which supports the boom  14  and the conveying pipeline  16 ) is not gravitationally level, it may result in unsafe operating conditions. For example, the boom  14  may experience unintended slewin (i.e., rotation about a vertical axis) at the turret  30 . Also, a gravitationally level boom base  28  is important to prevent tipping of the truck  12 . 
     Leveling of the truck chassis  20  and the boom base  28  is performed using the front outriggers  22   l ,  22   r  and the rear outriggers  23   l ,  23   r . As shown in FIG.  2 . the outriggers  22   l ,  22   r ,  23   l ,  23   r  include a support arm  46 , a foot  48 , cribbing  50 , solenoid  52 , pressure switch  54 , and extend sensor  56 . Once the truck  12  has reached its intended operating position, the outriggers  22   l ,  22   r ,  23   l ,  23   r  are deployed (i.e., extended out and away from truck) by moving the support arm  46  to place them into position to help level and stabilize the truck  12 . The extend sensor  56  is a proximity sensor that provides a signal when the outrigger  22   l ,  22   r ,  23   l ,  23   r  is fully extended away from the truck  12 . The outriggers  22   l ,  22   r ,  23   l ,  23   r  apply pressure to the surrounding ground by lowering the foot  48  down onto the cribbing  50 , which is placed on the ground under the extension foot  48  for additional support. 
     The raising and lowering of the foot  48  is done hydraulically using a system generally known to those of ordinary skill in the art. Although in FIG. 2, the solenoid  52  is shown located on the outrigger  22   l ,  22   r ,  23   l ,  23   r , it may also be located on the truck  12  near the corresponding outrigger  22   l ,  22   r ,  23   l ,  23   r . The solenoid  52  receives an electrical control signal and acts to open or close a hydraulic fluid valve, which controls the flow of fluid to a hydraulic cylinder, and thereby adjusts the vertical position of the foot  48  with respect to the support arm  46 . The pressure switch  54  provides a signal when it detects some threshold pressure level upon the arm  48 . The purpose of the pressure switch  54  is to provide a signal when the arm  48  is sufficiently lowered to generate the minimum pressure required upon the cribbing  50  for safe operation on the ground. This minimum pressure is generally around 500 pounds per square inch and functions to evenly distribute the weight between the four outriggers  22   l ,  22   r ,  23   l ,  23   r.    
     FIG. 3 shows a top view of the fire-fighting system  10  according to the present invention. FIG. 3 also shows the positions of the front outriggers  22   l ,  22   r  and the rear outriggers  23   l ,  23   r  with respect to the truck  12 , when the outriggers  22   l ,  22   r ,  23   l ,  23   r  have been fully deployed. The fire-fighting system  10  of the present invention operates to automatically level the chassis  20  of the truck  12 . Leveling of the chassis  20  also levels the base  28 , which is attached to the chassis  20 . Leveling of the base  28  acts to level the turret  30  and thus the entire boom  14  that it supports. As previously mentioned, leveling of the chassis  20  of the truck  12  is performed by using the outriggers  22   l ,  22   r ,  23   l ,  23   r  to apply pressure to the surrounding ground. 
     As shown in FIG. 3, the truck  12  has a tilt sensor  60  mounted to its chassis  20  near a longitudinal center line and closer to a front end of the truck  12 . The tilt sensor  60  is centered at the intersection of the imaginary line extending from the front outrigger  22   r  to the rear outrigger  23   l  and the imaginary line extending from the front outrigger  22   l  to the rear outrigger  23   r . As shown in FIG. 3, a y-axis  62  runs along a longitudinal centerline of the truck  12  of the fire-fighting system  10 , and an x-axis  64  runs orthogonal to the y-axis and through a center of the tilt sensor  60 . The tilt sensor  60  is disposed at the intersection of the y-axis  62  and the x-axis  64  and oriented such that it may provide a signal representing the angle between the y-axis  62  and gravitational level and the angle between the x-axis  64  and gravitational level. 
     As further shown in FIG. 3, a y′-axis  66  extends between a center of the foot  48  of the front outrigger  22   l  and a center of the foot  48  of the rear outrigger  23   r . An x′-axis  68  extends between a center of the foot  48  of the front outrigger  22   r  and a center of the foot  48  of the rear outrigger  23   l . Both the y′-axis  66  and the x′-axis  68  extend through the intersection of the y-axis  62  and the x-axis  64 . Using standard trigonometric relationships, and the signals from the tilt sensor  60 , it is thus possible to calculate the angles of the y′-axis  66  and the x′-axis  68  from gravitational level. These signals are then used to calculate which of the outriggers  22   l ,  22   r ,  23   l ,  23   r  to adjust as explained in greater detail below. 
     FIG. 4 shows a block schematic of the inputs and outputs from a microcontroller  70  used to perform the autoleveling function in the fire-fighting system  10  of the present invention. As shown in FIG. 4, the microcontroller  70  accepts input signals from the tilt sensor  60 , extend sensor signals  56   a ,  56   b ,  56   c , and  56   d  (corresponding to the front left outrigger  22   l , the front right outrigger  22   r , the rear left outrigger  23   l , and the rear right outrigger  23   r , respectively), and pressure switch signals  54   a ,  54   b ,  54   c , and  54   d  (corresponding to the front left outrigger  22   l , the front right outrigger  22   r , the rear left outrigger  23   l , and the rear right outrigger  23   r , respectively). Based on these input signals, the microcontroller  70  generates a drive signal to each of the outriggers  22   l ,  22   r ,  23   l ,  23   r . The drive signal (generated by the microcontroller  70  is an electrical control signal used to operate the solenoids  52  on the outriggers  22   l ,  22   r ,  23   l ,  23   r , which adjust hydraulic valves to affect the position of the feet  48  of the respective outriggers. 
     During operation the truck  12  is transported to a strategic position for fighting a fire. The operator then manually deploys the outriggers  22   l ,  22   r ,  23   l ,  23   r . The operator then commands the two front outriggers  22   l ,  22   r  and the two rear outriggers  23   l ,  2   r  to deploy or extend away from the chassis  20 . The outriggers  22   l ,  22   r ,  23   l ,  23   r  continue to deploy until a signal is received from the corresponding extend sensors  56   a ,  56   b ,  56   c ,  56   d . The operator continues to deploy the outriggers  22   l ,  22   r ,  23   l ,  23   r  until the signal is received from the extend sensor  56   a ,  56   b ,  56   c ,  56   d , deployment of the corresponding outrigger ceases. Once all four outriggers  22   l ,  22   r ,  23   l ,  23   r  have been fully deployed, the operator selects the autoleveling function. The microcontroller  70  operates the solenoids  52  of each of the outriggers  22   l ,  22   r ,  23   l ,  23   r  to begin extension (i.e., movement down and away from the support arm  56 ) of the foot  48 . This extension continues until a programmed pressure level is reached within the hydraulic fluid driving the foot  48  of the outrigger  22   l ,  22   r ,  23   l ,  23   r . When the pressure level is reached the pressure switch  54   a ,  54   b ,  54   c ,  54   d  activate and the microcontroller  70  ceases extension of the foot  48  of the corresponding outrigger  22   l ,  22   r ,  23   l ,  23   r . This process continues until each foot  48  of each outrigger  22   l ,  22   r ,  23   l ,  23   r  is extended to a minimum pressure point. At this point the microcontroller  70  executes the autoleveling routine described below. 
     As discussed above, and as illustrated in FIG. 3, the outriggers  22   l ,  22   r ,  23   l ,  23   r  are positioned on the y′-axis  66  and the x′-axis  68 . The tilt sensor  60 , however, provides a signal indicative of the angle with respect to gravitational level of the y-axis  62  and the x-axis  64 . Based on the angle provided by the tilt sensor  60 , in the form of a voltage, the microcontroller  70  calculates the slope of the chassis  20 . The tilt sensor  60  provides two voltages, one indicative of the slope of the y-axis  62  and the other indicative of the slope of the x-axis  64 . If the voltage provided by the tilt sensor  60  is positive, the slope is positive. A positive slope along the y-axis  62  is defined by a point on the rear of the truck  12  having a higher altitude than a point on the front of the truck  12 . A positive slope along the x-axis  64  is defined by a point on the right side of the truck  12  having a higher altitude than a point on the left side of the truck  12 . 
     Once the microcontroller  70  has calculated the slope along the y-axis  62  and the slope along the x-axis  64 , it calculates the slope along the y′-axis  66  and along the x′-axis  68  by performing a coordinate transformation using the following equations: 
     
       
         m′ x =m x  cosθ+m y  sinθm′ y =m y  cosφ−m x  sinφ 
       
     
     where m′ x  is the slope along the x′-axis  68 , and m′ y  is the slope along the y′-axis  66 , m x  is the slope along the x-axis  64 , m y  is the slope along the y-axis  62 , θ is the angle between the x-axis  64  and the x′-axis  68  (as shown in FIG.  3 ), and φ is the angle between the y-axis  62  and the y′-axis  66  (as shown in FIG.  3 ). 
     The microcontroller  70  then generates a drive signal to each of the outriggers  22   l ,  22   r ,  23   l ,  23   r  based on m′ x  and m′ y  using the following equations: 
     
       
         x1(t)=k(m′ x (t)) 
       
     
     
       
         x2(t)=−k(m′ x (t)) 
       
     
     
       
         y1(t)=k(m′ y (t)) 
       
     
     
       
         y2(t)=−k(m′ y (t)) 
       
     
     where x1(t) is the drive signal to the solenoid  52  of the outrigger  23   l  as a function of time, x2(t) is the drive signal to the solenoid  52  of the outrigger  22   r  as a function of time, y1(t) is the drive signal to the solenoid  52  of the outrigger  23   r  as a function of time, y2(t) is the drive signal to the solenoid  52  of the outrigger  22   l  as a function of time, and k is an adjustable constant that affects the response rate of the system. 
     The autoleveling system of the fire-fighting system  10  of the present invention is designed to operate so that leveling is obtained only by raising the position of one of the outriggers  22   l ,  22   r ,  23   l ,  23   r . Therefore, if the drive signal calculated using the above equations is negative, it will not be transmitted to the corresponding solenoid  52 . Only positive drive signals are sent causing one or more of the solenoids  52  to open and cause extension or lowering of the corresponding arm  46 . The microcontroller  70  continues to perform this procedure until the results from the tilt sensor  60  indicate that the chassis  20  of the truck  12  is sufficiently close to gravitationally level, and the pressure switches  54   a ,  54   b ,  54   c ,  54   d  have activated, at which time the autoleveling function is complete. 
     The microcontroller  70  will also terminate the autoleveling procedure if the truck  12  enters an unsafe position such that it may tip. Unsafe positions may be programmed into or calculated by the microcontroller  70  for this purpose. 
     Although the present invention has been described with reference to a fire-fighting vehicle, it should be apparent to one of ordinary skill in the art that the disclosed system would function equally as well to gravitationally level a boom and pipeline system mounted to another type of vehicle or even mounted to a base not intended to be mobile. For instance, the device of the present invention could be applied to a concrete pumping boom truck. The principle of the present invention may be employed to automatically level a boom system to insure its safe operation. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.