Patent Publication Number: US-10773934-B2

Title: Machine having hoisting system with instrumented fairlead

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a machine equipped with a sideboom and a fairlead for guiding a hoisting cable to and from the sideboom, and more particularly to such a machine where the fairlead is instrumented with a cable state sensing mechanism. 
     BACKGROUND 
     Pipelayers are specialized machines used to suspend and place pipelines in a prepared trench or the like. A typical pipelayer includes a load manipulating boom positionable outwardly from the side of the machine in a direction generally perpendicular to a forward travel direction. It is common for a cable and rigging system to be provided for manipulating the position of the boom, as well as a load suspended by the boom adjacent to or within a trench. It is also typical for pipelayers to operate in teams with a group of the machines operating in a coordinated fashion, to each support a different section of pipe as the pipe is gradually placed into a trench. In some instances the pipe sections are welded together as they are suspended by the pipelayer machines. Pipelayer teams often require precise and concerted efforts not only for successful placement but also to optimize speed and efficiency and protect operators and ground crew personnel. 
     Due to the nature of pipeline placement and support of pipe sections out to the side of the machine, there can be challenges to stably supporting the suspended load without risking tipping the machine. These challenges can be particularly acute in poor underfoot conditions, as well as steep terrain. To enhance stability most pipelayer machines are equipped with a counterweight positioned opposite the sideboom, and which can be adjusted to compensate for adjustments in the height and positioning of a suspended load. One example pipelayer machine is known from U.S. Pat. No. 8,783,477 to Camacho et al. It will be appreciated that a significant degree of operator skill can be required to control the speed and travel direction of a pipelayer machine while also monitoring and adjusting the suspension height of the load and positioning of the supporting sideboom. The availability of skilled operators, as well as ground crew, at worksites that are often remote has long challenged the industry. For these and other reasons, continued advancements and improvements to develop and exploit technological solutions in the pipelayer field are desirable. 
     SUMMARY OF THE INVENTION 
     In one aspect, a machine includes a frame, and a hoisting system coupled to the frame and including a winch assembly. The hoisting system further includes a boom movable by pivoting between a first boom position, and a second boom position at which the boom extends outboard of the frame. The hoisting system further includes a fairlead, and a hoisting cable extending through the fairlead from the winch assembly to the boom. The fairlead is supported at a fixed orientation relative to the frame, such that a feed angle of the hoisting cable between the fairlead and the boom varies in response to the pivoting of the boom between the first boom position and the second boom position. The machine further includes a hoisting control system having a cable state sensing mechanism resident on the fairlead and structured to produce cable monitoring data indicative of at least one of a cable feed length, a cable feed angle, or a cable load, and an electronic control unit coupled with the cable state sensing mechanism and structured to output an alert based on the cable monitoring data. 
     In another aspect, a fairlead system for a machine includes a fairlead having a first end forming a fairlead base having a mounting surface, for mounting the fairlead to a frame in a machine, and a second end, and defining a longitudinal fairlead axis extending between the first end and the second end. The fairlead further includes a feed pulley, for feeding a hoisting cable through the fairlead between a winch assembly and a pivotable boom and the machine. A cable state sensing mechanism is resident on the fairlead and structured to produce cable monitoring data indicative of at least one of a cable feed length, a cable feed angle, or a cable load, and instrumentation circuitry for connecting the cable state sensing mechanism to an electronic control unit in a hoisting control system in the machine. 
     In still another aspect, a method of operating a machine includes guiding a hoisting cable between a winch assembly and a boom in the machine by way of a fairlead supported at a fixed orientation relative to a frame of the machine, and pivoting the boom between a first boom position and a second boom position relative to the frame. The method further includes producing cable monitoring data from a cable state sensing mechanism resident on the fairlead. The cable monitoring data is indicative of a change to at least one of a cable feed length, a cable feed angle, or a cable load that occurs in response to the pivoting of the boom between the first boom position and the second boom position. The method still further includes outputting an alert based on the cable monitoring data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a machine, according to one embodiment; 
         FIG. 2  is a diagrammatic view of a fairlead system, including a detailed enlargement, according to one embodiment; 
         FIG. 3  is a partially open side diagrammatic view of a fairlead system shown as it might appear ready for installation on a centerframe beam of a machine, according to one embodiment; 
         FIG. 4  is a block diagram of a control system, according to one embodiment; 
         FIG. 5  is a diagrammatic view of parts of a hoisting system in a first configuration; 
         FIG. 6  is a diagrammatic view of parts of a hoisting system in another configuration; and 
         FIG. 7  is a flowchart illustrating example process and control logic flow, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , there is shown a ground-engaging machine  10  according to one embodiment, and structured as a pipelayer machine for transporting, suspending, and placing pipe sections of a pipeline according to generally known practices. Machine  10  includes a frame  12  having a front frame end  14  and a back frame end  16 . An engine system  22  is mounted adjacent to front frame end  14  in the illustrated embodiment. An operator station  20 , such as an operator cab, is coupled to and mounted upon frame  12  between front frame end  14  and back frame end  16 . Ground-engaging elements  18 , including tracks in the illustrated embodiment, are coupled to and positioned upon opposite sides of frame  12 . Machine  10  further includes a counterweight  30  positioned upon one side of frame  12  and adjustable by way of one or more counterweight actuators  32  in a generally conventional manner. 
     Machine  10  further includes a hoisting system  24  coupled to frame  12  and including a winch assembly  26 , and a boom  28  movable by pivoting between a first boom position, and a second boom position, at which boom  28  extends outboard of frame  12 . Boom  28  may include a sideboom, and is pivotable about a sideboom pivot axis  29  having a fixed orientation and extending in a fore-to-aft direction relative to frame  12 . Boom  28  may be oriented substantially vertically at the first boom position, and oriented approximately as shown in  FIG. 1  outboard of frame  12  at the second boom position. Boom  28  (hereinafter “sideboom  28 ”) may be structured for lowering further than what is shown in  FIG. 1 , to or below a horizontal plane in certain embodiments. Those skilled in the art will be familiar with positioning and adjustment of a counterweight such as counterweight  30  to offset a load supported by way of a sideboom, such as a length of pipe. In an implementation, sideboom  28  may be coupled to frame  12  at each of a forward location and a rearward location by way of a forward connector  36  and a rearward connector  38 , respectively. Sideboom  28  may further include a first or forward beam  50  and a second or rearward beam  52  coupled with forward connection  36  and rearward connection  38 , respectively, and arranged in a generally triangular pattern. Other sideboom designs and configurations could be employed in different embodiments. Hoisting system  24  further includes an upper hook pulley block  44  supported by sideboom  28 , a lower hook pulley block  46  suspended below upper hook pulley block  44 , and a hook  48 . A hoisting cable  43  may be attached to hook  48  and extends through lower hook pulley block  46  and upper hook pulley block  44 , with lower hook pulley block  46  suspended by hoisting cable  43 . Hoisting cable  43  can also extend to a winch  42  in winch assembly  26 . Hoisting cable  43  may be attached to and wrap about a winding drum or the like of winch  42  to enable raising and lowering of hook  48 . Another winch  40  of winch assembly  26  can include another winding drum or the like that is attached to and winds one or more boom cables  41  structured for raising and lowering sideboom  28  in a generally known manner. 
     Hoisting system  24  further includes a fairlead system  55  including a fairlead  56 . Hoisting cable  43  extends through fairlead  56  from winch assembly  26  to sideboom  28 . Fairlead  56  is supported at a fixed orientation relative to frame  12 , such that a feed angle of hoisting cable  43  between fairlead  56  and sideboom  28  varies in response to the pivoting of sideboom  28  between the first boom position and the second boom position. Fairlead  56  may be positioned at a fairlead mounting location longitudinally between front frame end  14  and back frame end  16 , and latitudinally between winch assembly  26  and sideboom  28 . The fairlead mounting location may be both forward and outboard of operator station/cab  20 . It can also be noted from  FIG. 1  that fairlead  56  is mounted upon a centerframe beam  54  that extends latitudinally across frame  12  generally between engine system  22  and operator station/cab  20 . Centerframe beam  54  can further be coupled with a track roller frame or the like (not numbered) supporting one of ground-engaging elements  18 , by way of forward connection  36  and rearward connection  38 . 
     Machine  10  further includes a hoisting control system  60  having a cable state sensing mechanism  62 ,  64 ,  66 , resident on fairlead  56 . The cable state sensing mechanism  62 ,  64 ,  66  can include one or more sensors  62 ,  64 ,  66  structured to produce cable monitoring data indicative of at least one of a cable feed length, a cable feed angle, or a cable load. Hoisting control system  60  also includes an electronic control unit  74  coupled with the cable state sensing mechanism  62 ,  64 ,  66  and structured to output an alert responsive to the cable monitoring data. 
     Referring also now to  FIG. 2 , fairlead  56  further includes a plurality of feed pullies, including a first feed pulley  80  rotatable about a first axis  81 , and a second feed pulley  82  rotatable about a second axis  83 . Hoisting cable  43  may extend about feed pullies  80  and  82  in a serpentine pattern, meaning that hoisting cable  43  changes direction at least twice, in opposite directions. Also shown in  FIG. 2  are additional details relating to the cable state sensing mechanism  62 ,  64 ,  66  which may be coupled with or part of electrical instrumentation circuitry  70  resident on fairlead  56 . As used herein, the term “circuitry” should be understood to include electrical connectors, wiring, circuit elements, or any of the various sensors contemplated herein. Wiring alone is not fairly understood to be circuitry. A wiring harness  78  is coupled with or part of instrumentation circuitry  70 , and structured to connect with hoisting control circuitry  76  on machine  10 . Hoisting control circuitry  76  can include or be connected with a counterweight position sensor  72  associated with counterweight actuator  32 , and also includes or is electrically connected with electronic control unit  74 . 
     As noted above, the cable state sensing mechanism  62 ,  64 ,  66  can include one or more sensors, in one implementation a cable angle sensor  66 . Electronic control unit  74  may further be structured to determine an angle of sideboom  28  based on the cable monitoring data produced by cable angle sensor  66 , as further discussed herein. The cable state sensing mechanism  62 ,  64 ,  66  may additionally or alternatively include a load sensor  64 , and electronic control unit  74  may be further structured to determine a hook load based on the cable monitoring data produced by load sensor  64 . In a further implementation, feed pulley  82  can include a pulley pin  84 , and load sensor  64  may include a strain gauge coupled with pulley pin  84 . A force vector  65  is also depicted in  FIG. 5 , and represents an example force exerted by tensioned hoisting cable  43  on feed pulley  82 . Contact between hoisting cable  43  and feed pulley  82 , and strain on pulley pin  84 , enables load sensor  64  to produce the cable monitoring data that is indicative of a load on hoisting cable  43 . Because load or tension on hoisting cable  43  can vary with an orientation of sideboom  28 , electronic control unit  74  can be structured to determine the actual current load or hook load based upon both the observed load on hoisting cable  43  as indicated by raw data produced by load sensor  64 , and the orientation of sideboom  28 . As an alternative to a strain gauge, a different type of load sensor might be used such as a position sensor coupled with a displaceable mechanism such as a gas spring, a mechanical spring, or an otherwise deformable or deflectable mechanism. Position and/or orientation sensors contemplated herein could include rotary or linear potentiometers, Hall effect sensors, inductive or capacitive sensors, optical sensors, or still another type. The cable state sensing mechanism  62 ,  64 ,  66  may also include a cable feeding sensor  62 , and electronic control unit  74  may be structured to determine a cable feed length through fairlead  56  based on the cable monitoring data produced by cable feeding sensor  62 . Cable feeding sensor  62  may include a pulley rotation counter, as further discussed herein. A body or frame sensor  68  which can produce data indicative of a position or orientation of frame  12  can also be resident on fairlead  56 , with pitch, roll, and yaw being monitored by sensor  68 . In a practical implementation strategy, sensor  68  can include an initial measurement unit or IMU. 
       FIG. 2  also includes a detailed enlargement illustrating additional features of cable angle sensor  66 , including a collar  71  positioned upon and extending circumferentially about hoisting cable  43 . It will be appreciated that hoisting cable  43  can feed in and out from fairlead  56  at a varying feed angle, through collar  71 . Collar  71  may be free to rotate with an upward and downward movement of hoisting cable  43  that occurs in response to the pivoting of sideboom  28 . Collar  71  may also be restricted from moving in and out with the feeding of hoisting cable  43  by way of an inboard stop  75  and an outboard stop  77 . Each of stop  75  and stop  77  can have a generally arcuate form and be positioned in fairlead  56  such that collar  71  contacts stop  77  if hoisting cable  43  is fed outward, and contacts stop  75  if hoisting cable  43  is fed inward. Collar  71  can be understood as a sensor target, with a sensor body  69  being supported at a fixed location and orientation in fairlead  56 . A sensor or sensor body coupled to one of fairlead  56  and hoisting cable  43 , and a sensor target coupled to the other of fairlead  56  and hoisting cable  43  provides a practical implementation strategy, although those skilled in the art will appreciate a variety of other ways of sensing cable angle. Electromagnetic pickups  73  or the like can be located upon sensor body  69  to enable detection of proximity of sensor target/collar  71  and thereby output the cable monitoring data indicative of cable angle, the significance of which will be further apparent from the following description. 
     Referring also now to  FIG. 3 , there is shown fairlead system  55  and illustrating fairlead  56  partially open and in further detail. Fairlead  56  can include a first fairlead end  57  forming a base and a second fairlead end  59  that includes a cable guide  58 . A mounting surface  61  is formed on first fairlead end/base  57 . In the illustrated embodiment, fairlead  56  includes a post  86  extending downwardly from first fairlead end  57  and having a plurality of bolting holes  88  formed therein. In  FIG. 3  post  86  is shown as it might appear being inserted into an aperture  94  formed in centerframe beam  54 . A plurality of bolting holes  90 , which can register with bolting holes  88  formed in centerframe beam  54 , are structured to receive bolts  92  to attach fairlead  56  in place upon centerframe beam  54 . It will be appreciated that fairlead system  55  could be installed by way of another strategy, such as an alternative bolting strategy with horizontally oriented bolts, by welding to a centerframe beam or another frame component, or by still another construction.  FIG. 3  also illustrates a first sideplate  96  and a second sideplate  97  of fairlead  56 , defining a through-channel extending therebetween. It can be seen that each of pulley  80  and pulley  82  is supported at least partially within through-channel  98 . A longitudinal fairlead axis  99  extends between first end  57  and second  59 . Certain prior strategies for monitoring machine position, boom position, and other properties attempted to place instrumentation such as position sensors directly on a machine boom. In the case of a pipelayer machine, for example, the boom is often removed for transport, necessitating breaking of electrical connections, and reestablishing electrical connections when the machine is prepared for returning to service after transport. An instrumented fairlead can maintain all the instrumentation onboard the machine without such drawbacks. It is further contemplated that a replacement fairlead system according to the present disclosure could be provided as an aftermarket component providing the foregoing and other advantages to existing machines already in the field. Fairlead system  55  can thus be bolted-on or welded-on in place of an existing fairlead, or provided as original equipment. 
     It will also be recalled that cable feeding sensor  62  produces cable monitoring data indicative of a cable feed length through fairlead  56 . In one embodiment, cable feeding sensor  62  can be structured as a rotation counter to output the cable monitoring data each time pulley  80  completes a rotation in a first direction. Cable feeding sensor  62 , or another sensor (not shown), could output a cable infeed signal each time pulley  80  completes a rotation in an opposite direction. An electronic proximity sensor, an electromechanical switch, or still other strategies could be used, such as an arrangement of sensor targets on pulley  80  that are sensed to indicate rotation in one direction by way of a first pattern rotated past a sensor and indicate rotation in an opposite direction by way of a reverse pattern rotated past the sensor. 
     Those skilled in the art will be familiar with the phenomenon of pulley block collision, and its potential risks of straining a hoisting cable or causing other problems. A location of the normally stationary upper hook pulley block  44  in space can be determined on the basis of fixed boom geometry and sideboom angle, which is directly proportional to cable feed angle. A location of lower hook pulley block  46  can be determined on the basis of a length of hoisting cable  43  fed through fairlead  56 , with a number of pulley revolutions in a feeding-out direction being proportional to a cable feed length. It will also be recalled that sensor  68  may be resident on fairlead  56 . Electronic control unit  74  can receive data from sensor  68  indicative of an orientation of frame  12 , and thus machine  10 . Based upon the known relationship between cable feed angle and sideboom orientation, electronic control unit  74  can determine an angle of sideboom  28  relative to a horizontal reference plane or some other reference. In this general manner, electronic control unit  74  monitors orientation of hoisting cable  43  and can account for position of machine  10  upon a slope, thus determining whether there is a risk of tipping over of machine  10  when supporting a given load at least when counterweight orientation is also considered, as further discussed herein. 
     Referring also now to  FIG. 4 , there are shown components of control system  60  in an example arrangement. Electronic control unit  74  includes an input/output interface  100 , for receiving inputs from various sensors and sending outputs in the nature of control commands, monitored quantities or qualities, and condition alerts as further discussed herein. Sensors  62 ,  64 ,  66 ,  68 ,  72  are shown coupled with electronic control unit  74  to provide cable monitoring data, machine/frame monitoring data, and counterweight monitoring data as the case may be, in the form of sensor signals, as described herein. Electronic control unit  74  further includes a processor  102 , which can include any suitable central processing unit such as a microcontroller or a microprocessor. Processor  102  is in communication with a memory  104  that stores computer executable program instructions in the nature of a load monitoring program or control routine  106  and a cable feed program or control routine  108 , as also further discussed herein. Memory  104  can include RAM, ROM, a hard drive, Flash, SDRAM, EEPROM, or still another type of memory. A load curve map is shown at  110  and is referenced by program  106  to determine a load condition of machine  10 , such as an overload condition or likely overload condition, and generate appropriate alerts, as further discussed herein. A display  112 , which may be mounted in or on operator cab  20 , can include a graphical user interface such as a touchscreen (not numbered), structured to convey various types of information to an operator, and receive control inputs from an operator. A plurality of alert icons are shown at  114  and represent alerts or warnings that can be presented to an operator by way of illumination, for example. Other operator perceptible alerts such as audible alerts might be used. 
     Turning now to  FIG. 5 , there is shown fairlead system  55  as it might appear where sideboom  28  is at a raised, stowed position. A cable feed angle  135  is defined between hoisting cable  43  and a horizontal reference plane. A boom angle  125  is defined between sideboom  28  and the horizontal reference plane.  FIG. 6  illustrates fairlead  55  as it might appear where sideboom  28  is lowered to a substantially horizontal position. In  FIG. 6 , cable feed angle  135  is shown between hoisting cable  43  and the horizontal reference plane, and angle  125  is equal substantially to zero. Based upon the known relationship or ascertainable relationship between cable feed angle  135  and sideboom angle  125 , cable angle measurements by way of cable angle sensor  66  can give a direct and proportional determination. The relationship between cable angle  135  and boom angle  125  can depend upon the relative size/lengths of fairlead  56  and sideboom  28  as well as the positioning of those components in machine  10 . In one implementation boom angle  125  could be mapped to cable feed angle  135 , whereas in other implementations boom angle  125  could be calculated by way of electronic control unit  74  in real time. 
     INDUSTRIAL APPLICABILITY 
     Operating machine  10  can include supporting a pipeline or section of pipeline in cooperation with a plurality of other pipelayer machines. The pipelayer machines can be arranged one after the other next to a prepared trench, with each pipelayer supporting a different pipe section in a roller sling or the like. Operators, or control systems, can raise, lower, and reposition as desired the individual pipe sections to place the pipeline in the trench as the group of machines moves forward. Ground crews can assist the machines with placement, positioning, welding together of adjacent pipe sections, and other support activities. A hoisting cable such as hoisting cable  43  can be guided in each one of the machines between a winch assembly and a boom by way of an instrumented fairlead such as fairlead  56  supported at a fixed orientation relative to the frame of the associated machine. 
     To position the pipeline sections as desired each machine can pivot its boom between a first boom position and a second boom position relative to the frame. The cable state sensing mechanism comprised of one or more sensors as described herein, resident on the fairlead, can produce cable monitoring data indicative of at least one of a cable feed length, a cable feed angle, or a cable load. Continuous or periodic monitoring will produce cable monitoring data indicative of changes to the at least one of a cable feed length, a cable feed angle, or a cable load that occurs in response to the pivoting of the boom between the first boom position and the second boom position. For example, pivoting sideboom  28  may impart the tendency for upper hook pulley block  44  and lower hook pulley block  46  to vary their relative spacing from one another, depending upon the extent (if any) to which hoisting cable  43  is wound or unwound from winch  42 . Analogously, pivoting of sideboom  28  varies cable feed angle and cable load. Based on the cable monitoring data that is indicative of changes to the parameters of interest, electronic control unit  74  can output an alert for display on display  112 , for production of an audible alert, for signaling to a site manager or supervisory control system, for data recording purposes, or for still another purpose. 
     Referring now to  FIG. 7 , there is shown a flowchart  200  illustrating example process and control logic flow corresponding to program  106 , and example process and control logic flow corresponding to program  108 . It should be appreciated that programs  106  and  108  could be executed as subroutines of the same software program or could run as separate parallel routines, for example. At a block  205  is shown the body IMU (frame sensor  68 ) that produces data indicative of frame position or orientation, and at a block  210  is shown cable angle sensor  66  that produces data indicative of cable angle. An angle converter is shown at a block  220  whereby electronic control unit  74  calculates an angle of sideboom  28  relative to a reference such as a horizontal reference plane. It will be recalled that cable feed angle varies with sideboom orientation. At a block  225  a boom overhang calculator is shown, which can enable electronic control unit  74  to determine the relative extent to which, or the absolute extent to which, sideboom  28  extends outwardly of frame  12 . At a block  230  is shown counterweight IMU, which can monitor a counterweight position (sensor  78 ). At a block  231  a position converter converts a position signal indicative of counterweight position to a counterweight angle, for example. A max load calculator is shown at  232 . At block  232 , electronic control unit  74  can determine a max allowable load for a given orientation of fairlead  56 , at a given orientation of machine  10 /frame  12 , and at a given orientation of counterweight  30 . As further discussed below, electronic control unit  74  can output an alert based on a current hook load and the determined max allowable load from block  232 . 
     It should also be appreciated that changing a sideboom angle, for instance, can change the max allowable load and justify outputting an alert. For example, an operator might lower sideboom  28  from a first orientation where a given hook load is allowable to a second orientation where the given hook load is not allowable. In such circumstances an overload alert can be output and the operator, or control system  60 , could raise sideboom  28 , raise counterweight  30 , adjust both sideboom  28  and counterweight  30 , or take some other action. Machine underfoot conditions could also be a factor in what max allowable loads or other threshold conditions are determined and how those conditions are managed. As suggested above, changes in any of cable feed angle, cable feed length, cable load, or still other parameters can justify outputting an alert, typically, but not necessarily, because relative machine stability and/or likelihood of tipping is changed. In view of the foregoing, it will thus be appreciated that load monitoring and management of overload, pulley block collision, and other machine operating conditions according to the present disclosure can be a dynamic process. 
     At a block  235  is shown the strain pin, producing the load monitoring signal by way of sensor  64 . At a block  240  is depicted a strain to load converter where a strain detected by way of sensor  64  is converted to a load on hoisting cable  43 . The determined load on hoisting cable  43  can be converted to a current hook load according to known trigonometric or other computational or inferential techniques, for example. A load curve map is shown at a block  245 . At block  245  electronic control unit  74  can compare the max allowable load to a current hook load. The load curve map might include a current hook load coordinate and a max load coordinate. An alternative strategy could include a cable load coordinate, a fairlead boom angle coordinate, a max load coordinate, and/or a counterweight angle coordinate. Still other map configurations could be used. 
     Several of the blocks in flowchart  200  represent information that can be displayed on display  112  to an operator. Machine angle is shown at a block  250  and can represent machine angle as determined on the basis of data from frame sensor  68 . Boom angle is shown at a block  255  and can display to an operator an angle of sideboom  28  relative to a horizontal reference plane, or relative to some other reference such as frame  12 . At a block  260 , boom overhang is displayed. At a block  262 , the max load determined at max load calculator  232  is displayed. At a block  265 , the current hook load on hoisting cable  43  is displayed. Block  270  displays a percent load, meaning a percent of max allowable load that is currently applied to hoisting cable  43 . At a block  272  counterweight position is displayed. 
     At a block  280  of program  108  is shown cable feed or cable feeding data produced by cable feed sensor  66 . At a block  282  is shown a feed-to-cable length converter where, for example, a number of pulley rotations is converted to a cable length. At a block  288 , it is queried whether conditions are near the 2-block limit, based on determined locations of hook blocks  44  and  46  as described herein. If no, the control routine can end or exit at a block  294 . If yes, the control routine can advance to a block  299  to output an anti-2-block warning or pulley collision alert. At a block  286  electronic control unit  74  can receive the load on hoisting cable  43  and query whether conditions are near a load limit? If no, the control routine can advance to a block  292  to end or exit. If yes, the control routine can advance to a block  298  to produce the load warning or overload alert. 
     The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.