SE544031C2

SE544031C2 - A method of controlling a crane, and a crane

Info

Publication number: SE544031C2
Application number: SE2050359A
Authority: SE
Inventors: Leif Törnblom
Original assignee: Hiab AB c/o Cargotec Sweden AB
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2021-11-09
Also published as: SE2050359A1; EP3889095B1; DK3889095T3; EP3889095A1

Abstract

A crane (1) comprising a movable arm (2), and a tool (9) provided at an end of the movable arm (2). The crane (1) comprises a control system configured to a) detect a first condition in which the tool (9) is in a holding position and the movable arm (2) is in an unloaded condition in which it is not actively lifting an object held by said tool (9), b) registering a first point of time at which the first condition is obtained and counting a period time (t) from the first point of time, and, c) when the counted period of time (t) exceeds a threshold value (tthreshold), activating a safe operation mode in the control system which prevents a first hydraulic device (3, 4, 5)) from moving the movable arm (2), said safe operation mode being deactivatable by an actuation of a second hydraulic valve for controlling the holding position of the tool (9).

Description

A method of controlling a crane, and a crane TECHNICAL FIELD The present invention relates to a method of controlling a crane,said crane comprising: a movable arm; at least one first hydraulicdevice configured to move the movable arm; a first hydraulic valveconfigured to control the operation of the at least one firsthydraulic device; a tool provided at an end of the movable arm,said tool comprising a first part and a second part; a secondhydraulic device configured to displace said first part in relation tosaid second part to a holding position in which the tool isconfigured to hold an object; a second hydraulic valve configuredto control the operation of the second hydraulic device, and; acontrol system comprising a readable memory, a user interfaceconfigured to enable a user to control the movable arm and tool byreceiving user commands, and a processor configured to controlthe first hydraulic device and the second hydraulic device bygenerating control signals to the first hydraulic valve and thereceived user second hydraulic valve in response to said commands.

The present invention also relates to such a crane.

BACKGROUND Hydraulic cranes of the type defined hereinabove may besubjected to leakage of hydraulic liquid present in the hydraulicvalve used for controlling the operation of the hydraulic device that controls the motion of the movable part of the tool that is responsible for holding an object. Such a leakage may imply thatif the crane operator gives user commands for the tool to grip orhold an object and then waits a period of time before actually liftingthe object with the crane, a situation where the tool no longer is ina gripping or holding position even though the crane operator mayassume so, may arise. These situations may be a safety issue forthe crane operator and may further lead to that the surrounding and objects handled by the crane are damaged.

This is a problem for cranes with hydraulically actuated cranetools, like for example hydraulic hooks and brick grabs. Often, thistype of tools are designed. Often, the tool is designed so as to belocked in a holding position once the arm is actively lifting theobject. This may be a mechanical locking of the tool caused by theown weight of the object being lifted. The locking in the holdingposition assumes that the tool is in fact in a holding position whenthe arm actively lifts the object. However, if leakage occurs duringinactivity when no lifting is performed by the crane, the leakagemay result in that the tool is not in the perfect holding positionwhen lifting by means of the arm is started. The tool then runs therisk of dropping the object as the mechanical locking has not been achieved when initiating the lifting of the object. lt is an object of the present invention to present a method ofcontrolling a crane, and a crane, that prevents unintentionaldropping of an object caused by imperfect holding of the objectdue to leakage or other dysfunctionality in a valve that controls a hydraulic device that controls the operation of the hook.

SUMMARY The object of the present invention is achieved by a method ofcontrolling a crane, the crane comprising: - a movable arm, - at least one first hydraulic device configured to move the movablearm, - a first hydraulic valve configured to control the operation of theat least one first hydraulic device, - a tool provided at an end of the movable arm, the tool comprisinga first part and a second part - a second hydraulic device configured to displace the first part inrelation to the second part to a holding position in which the toolis configured to hold an object, - a second hydraulic valve configured to control the operation thesecond hydraulic device, - a control system comprising - a readable memory, - a user interface configured to enable a user to control themovable arm and tool by receiving user commands, and, - a processor configured to control the first hydraulic deviceand the second hydraulic device by generating control signals tothe first hydraulic valve and the second hydraulic valve inresponse to the received user commands, the method beingcharacterized in that it comprises the steps ofa) detecting a first condition in which the tool is in the holdingposition and the movable arm is in an unloaded condition in whichit is not actively lifting an object held by the tool, b) registering a first point of time at which the first condition isobtained and counting a period time from the first point of time, and, c) when the counted period of time exceeds a threshold value (andsaid first condition is maintained), activating a safe operationmode in the control system which prevents the first hydraulicdevice from moving the movable arm, the safe operation mode being deactivatable by an actuation of the second hydraulic valve.

The deactivation of the safe operation mode may result from adirect actuation of the second hydraulic valve in response to acrane operator command via the user interface. Alternatively, oras a supplement to the mentioned direct actuation, thedeactivation of the safe operation mode may be an automaticactuation of the second hydraulic valve performed automaticallyby the control system itself as a response to a tentative by a userto move the movable arm when the safe operation mode isactivated. The automatic actuation of the second hydraulic valvemay be a predetermined actuation that results in that it is madesure that the first part is in a holding position before deactivatingthe safe mode. The actuation of the second hydraulic valve madein response to a user command may result in that it is made surethat the first part is in a holding position or that it is made sure thatthe first part is not in a holding position. lf the crane operator givesa user command to move the first part in position which is not aholding position then this indicates that the crane operator isaware of the fact that the tool is not holding the object and thereis hence no risk that the object should be dropped during amovement of the movable arm. A tentative to move the movablearm includes any tentative to move a structural element which ismovable via order from the user interface, wherein the structuralelement is connected the movable arm such that a motion thereof will also result in a motion of the movable arm. Such further structural element may typically be a boom which is part of thecrane, to which boom the movable arm is connected. Also otherstructural elements, which are not hydraulically driven and themotion of which is controllable via the user interface, and themotion of which will induce a motion of the movable arm are prevented from being moved, in the safe operation mode.

According to one embodiment the actuation of the secondhydraulic valve is an actuation in response to a user command received via the user interface.

According to one embodiment the actuation of the secondhydraulic valve is an actuation in response to a user command received via the user interface to apply the holding position.

According to one embodiment the control system is configured tobe in an off-mode and an on-mode, and that the method comprisesthe further step of - detecting a switch from the off-mode to the on-mode, and - as a response to the switch being detected, activating the safe operation mode.

According to one embodiment the control system is configured to execute the steps of the method.

The object of the present invention is also achieved by a cranecomprising: - a movable arm, - at least one first hydraulic device configured to move the movable arm, - a first hydraulic valve configured to control the operation of theat least one first hydraulic device, - a tool provided at an end of the movable arm, the tool comprisinga first part and a second part - a second hydraulic device configured to displace the first part inrelation to the second part to a holding position in which the toolis configured to hold an object, - a second hydraulic valve configured to control the operation thesecond hydraulic device, - a control system comprising - a readable memory, - a user interface configured to enable a user to control themovable arm and tool by receiving user commands, and, - a processor configured to control the first hydraulic deviceand the second hydraulic device by generating control signals tothe first hydraulic valve and to the second hydraulic valve inresponse to the received user commands, the crane beingcharacterized in that the control system is configured toa) detect a first condition in which the tool is in the holding positionand the movable arm is in an unloaded condition in which it is notactively lifting an object held by the tool, b) register a first point of time at which the first condition isobtained and counting a period time from the first point of time,and, c) when the counted period of time exceeds a threshold value (andsaid first condition is maintained), activate a safe operation modewhich prevents the first hydraulic device from moving the movablearm, the safe operation mode being deactivatable by an actuation of the second hydraulic valve.

The deactivation of the safe operation mode may be a directactuation of the second hydraulic valve through a user commandreceived interface. from a crane operator via the user Alternatively, or as a supplement to the mentioned directactuation, control system is configured to perform the deactivationof the safe operation mode may be an automatic actuation of thesecond hydraulic valve performed as a response to a tentative bya user to move the movable when the safe operation mode isactivated. A tentative to move the movable arm includes anytentative to move a structural element which is movable via anorder from the user interface, wherein the structural element isconnected to the movable arm such that a motion thereof will alsoresult in a motion of the movable arm. Such further structuralelement may typically be a boom which is part of the crane, to which boom the movable arm is connected.

According to one embodiment the actuation of the secondhydraulic valve is an actuation in response to a user commandreceived via the user interface. Thus, actuation of the second hydraulic valve can be simplified.

According to one embodiment the control system is configured tobe in an off-mode and an on-mode, and that the control system isconfigured to - detect a switch from the off-mode to the on-mode, and - as a response to the switch being detected, activate the safeoperation mode. Thus, in cases in which the control system hasbeen in an off-mode for a time, and the time from the applicationof the off-mode to the switch to the on-mode has not been counted,the control system will automatically activate the safe operation mode.

According to one embodiment the off-mode is a mode in whichpower for actuation of the first and second hydraulic devices isturned off. According to one embodiment, the off-mode includesthat the control system is disconnected from an electric power SOUFCG.

According to one embodiment the crane comprises at least onepump configured to deliver pressurized fluid to the first hydraulicdevice and to the second hydraulic device, and that, in the off-mode, the pump is inactive.

According to one embodiment the second hydraulic valvecomprises a spool, a motion of which results in the displacement of the first part in relation to the second part to a holding position.

According to one embodiment the crane comprises at least onemovable boom to which the arm is directly or indirectly connectedand that, in the safe operation mode, movement of the boom, inparticular a movement of the boom through an order via the user interface, is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS ln the following, embodiments of the invention are described withreference to the attached drawing, on which: Fig. 1 embodiment of the invention, is perspective view showing a crane according to an Fig. 2 is a schematic representation of a hydraulic system of thecrane in fig. 1, Fig. 3 is a first side view showing a tool of the crane, Fig. 4 is a second side view of the tool shown in Fig. 3, and Fig. 5 is a flow chart of a method of controlling a crane according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THEINVENTION Fig. 1 shows an embodiment according to the invention of a crane1 comprising a movable arm 2. The crane 1 may, for example, be mounted on a working machine, such as truck.

The crane 1 comprises a plurality of first hydraulic devices 3, 4, 5configured to move the movable arm 2, and corresponding firsthydraulic valves 6, 7, 8 (see fig. 2), which are configured to controlthe operation of the respective first hydraulic devices 3, 4, 5. Thefirst hydraulic devices 3, 4, 5 each comprises a cylinder-piston arrangement.

At an end of the movable arm 2 there is provided a tool 9, whichcomprises a first part 10 and a second part 11. A second hydraulicdevice 12 is configured to displace the first part 10 in relation to the second part 11 to a holding position in which the tool 9 is configured to hold an object. The second hydraulic device 12comprises a cylinder-piston arrangement. A second hydraulicvalve 13 is configured to control the operation the secondhydraulic device 12. The second hydraulic valve 13 is a directionalvalve, and comprises a spool. The flow of hydraulic liquid throughthe second hydraulic valve 13 depends on the position of thespool. A motion of the spool thus, results in the displacement ofthe first part in relation to the second part to or from the holdingposition. The first hydraulic valves 6, 7, 8 for controlling the motionof the movable arm 2 each has a corresponding design andfunctionality as the second hydraulic valve 13, but for the purposeof controlling the motion of the movable arm 2 by means of the first hydraulic devices 3, 4, 5.

Further, the crane 1 comprises a control system14 comprising areadable 15 memory and a user interface 16. The user interface16 is configured to enable a user to control the motions of themovable arm 2 and the tool 9 by receiving user commands via theuser interface 16. The user commands may also be referred to asorders. ln the embodiment shown, the user interface 16 is ahandheld remote control device for controlling the motion of thearm 2 and the tool 9 by controlling the above-mentioned firsthydraulic valves 6, 7, 8 and the second hydraulic valve 13. Theuser interface 16 may comprise a wired or a wireless controldevice or a combination of wired and wireless control devices. Theuser interface may allow for the crane to be controlled by a craneoperator at the location of the crane or at a remote location withsupport from video images of the crane. The control system 9further comprises a processor 17 configured to control the first hydraulic devices 3, 4, 5 and the second hydraulic device 12 by generating control signals to the first hydraulic valves 6, 7, 8 andto the second hydraulic valve 13 in response to the received user commands.

The control system 14 is configured to detect a first condition inwhich the tool 9 is in the holding position and the movable arm 2is in an unloaded condition in which it is not actively lifting anobject held by the tool 9. The detection may be executed by meansof suitable sensors, for example pressure sensors arranged in thefirst hydraulic devices. ln another example, it may be determinedby signals from a spool sensor monitoring the position of the spoolin the hydraulic valve 13 whether the valve is actuated to set thetool 9 in a holding position. The loading condition of the movablearm 2 may for example be determined based on signals frompressure sensors arranged in the first hydraulic devices. Thecontrol system 14 may hence detect the first condition using a combination of signals received from suitable sensors.

The object may typically be resting on and be supported by groundin said first condition. Further, the control system 14 is configuredto register a first point of time at which the first condition isobtained and counting a period time from the first point of time.When the counted period of time exceeds a threshold value, andthe first conditions is still maintained without any actuation of thesecond hydraulic device 12 during said time period, the controlsystem is configured to activate a safe operation mode whichprevents the first hydraulic devices 3, 4, 5 from moving themovable arm 2. The phrase “actively lifting the object” is herereferring to the lifting of the object that is intended to be moved by the crane. A practical example may be a large package of building material that is to be moved from the load bed of a truck to aconstruction site where the building material is to be used. ln orderto be able to move the package with the crane, straps are oftenused to attach the package to a crane tool such as a hydraulichook. Using this example the object to be moved would be thecombination of the package of building material and the straps, sothe crane would be actively lifting the object when the lifting actionof the crane is applied to both the straps and the package of building material.

The safe operation mode is deactivatable by an actuation of thesecond hydraulic valve 13. ln the presented exemplifyingembodiment, the deactivation of the safe operation mode may bea direct actuation of the second hydraulic valve 13 through anactuation order by a user via the user interface 16. Alternatively,or as a supplement to the mentioned direct actuation, thedeactivation of the safe operation mode may be an automaticactuation of the second hydraulic valve 13 performed by thecontrol system 14 itself as a response to a tentative by a user tomove the movable arm 2 when the safe operation mode isactivated. The automatic actuation of the second hydraulic valvemay hence make sure that the first part is in a holding positionbefore the control system allows the movable arm 2 to be moved.A tentative to move the movable arm 2 includes any tentative tomove a structural element which is movable via order from the userinterface 16, wherein the structural element is connected themovable arm 2 such that a motion thereof will also result in amotion of the movable arm 2. Such further structural element maytypically be a boom 18 which is part of the crane, to which boom 18 the movable arm is connected. ln the shown embodiment, the order to the second hydraulic valve13 which triggers a deactivation of the safe operation mode is anorder to apply the holding position, either by the user via the userinterface 16 or automatically by the control system 14 itself. The13 which deactivation of the safe operation mode may be an order to apply order to the second hydraulic valve triggers athe holding position or a release position for the tool 9 in the casethat the order is received from a crane operator via the userinterface 16. ln the case of the automatic actuation the controlsystem 14 actuates the second hydraulic valve to set the tool in a holding position. ln the embodiment described here, the control system 14 isconfigured to be in an off-mode and an on-mode. The controlsystem 14 is configured to detect a switch from the off-mode to theon-mode, and, as a response to the switch being detected, activatethe safe operation mode. The off-mode is a mode in which powerfor actuation of the first hydraulic devices 3, 4, 5 and the secondhydraulic devices 12 is turned off and the control system 14 isdisconnected from an electric power source (not shown). Thecrane 1 comprises at least one pump 19 configured to deliverpressurized fluid to the first hydraulic devices 3, 4, 5 and to thesecond hydraulic device 12. ln the off-mode, the pump 19 is inacüve. ln the illustrated embodiment, the hydraulic crane 1 comprisesfurther structural elements, which are connected to the movablearm 2 and provided with hydraulic devices or for moving those further structural elements. The control system 9 is configured to enable a user to move said further structural elements via ordersreceived by the user interface. Any motion of such a furtherstructural element, which results in a motion of the movable arm2, is regarded as a motion of the movable arm 2. The first hydraulicdevices 3, 4, 5 for moving the movable arm thus includes ahydraulic device 5 for moving the boom 18 in relation to a column20, which is also part of the crane 1. The arm 2 itself is telescopicand comprises a first part 2a and a second part 2b. One of the firsthydraulic devices 3 is configured to telescopically displace saidfirst part 2a in relation to the second part 2b. Anotherfirst hydraulicdevice 4 is configured to pivot the arm 2 in relation to the boom18.

Also which are not hydraulically driven and the motion of which is controllable via the possible other structural elements,user interface 16, and the motion of which will induce a motion ofthe movable arm 2 are prevented from being moved in the safe operation mode.

Fig. 5 is a flow chart of a method of controlling a crane 1 illustratedin fig. 1. The method comprises the steps of - detecting (S1) a first condition in which the tool 9 is in theholding position and the movable arm 2 is in an unloadedcondition in which it is not actively lifting an object held bythe tool 9, - registering (S2) a first point of time at which the firstcondition is obtained and counting a period time t from thefirst point of time, and, - when the counted period of time t exceeds a threshold value ttmeshoid, activating (S3) a safe operation mode in the control system which prevents the first hydraulic devicefrom moving the movable arm 2, the safe operation modebeing deactivatable by an actuation of the second hydraulic valve 13, automatic or manual.

The control system is configured to be in an off-mode and an on-mode, and step S3 also comprises - detecting a switch from the off-mode to the on-mode, and - as a response to the switch being detected, activating the safe operation mode When the safe operation mode is deactivated, the counted periodof time t is further reset to zero. After deactivating the safeoperation mode, the counting will hence start from zero when acondition in which the tool 9 is in the holding position and the movable arm 2 is in an unloaded condition, once again is detected. lf the time counter has been inactive due to the control system 14having been in the off-mode, the control system will thus ensurethat the safe operation mode is active upon detection that a switchto the on-mode has been performed, irrespectively of the fact that the counted period time may be less than said threshold value.

Claims

1. A method of controlling a crane (1), said crane (1) comprising:- a movable arm (2), - at least one first hydraulic device (3, 4, 5) configured to move themovable arm (2), - a first hydraulic valve (6, 7, 8) configured to control the operationof the at least one first hydraulic device (3, 4, 5) - a tool (9) provided at an end of the movable arm (2), said tool (4)comprising a first part (10) and a second part (11), - a second hydraulic device (12) configured to displace said firstpart (10) in relation to said second part (11) to a holding positionin which the tool (9) is configured to hold an object, - a second hydraulic valve (13) configured to control the operationthe second hydraulic device (12), - a control system (14) comprising - a readable memory (15), - a user interface (16) configured to enable a user to controlthe movable arm (2) and the tool (9) by receiving user commands,and, - a processor (17) configured to control the first hydraulicdevice (3, 4, 5) and the second hydraulic device (12) by generatingcontrol signals to the first hydraulic valve (6, 7, 8) and to thesecond hydraulic valve (13) in response to said received usercommands, said method being characterized in that it comprisesthe steps ofa) detecting a first condition in which the tool (9) is in said holdingposition and the movable arm (2) is in an unloaded condition in which it is not actively lifting an object held by said tool (9), b) registering a first point of time at which the first condition isobtained and counting a period time (t) from the first point of time,and, c) when the counted period of time (t) exceeds a threshold value(ttmeshold), activating a safe operation mode in the control system(14) which prevents the first hydraulic device (3, 4, 5) from movingthe movable arm (2), said safe operation mode being deactivatable by an actuation of said second hydraulic valve (13).

2. A method according to claim 1, characterized in that saidactuation of said second hydraulic valve (13) is an actuation in response to a user command received via the user interface (16).

3. A method according to claim 2, characterized in that saidactuation of the second hydraulic valve (13) is an actuation inresponse to a user command received via the user interface (16) to apply said holding position.

4. A method according to any one of claims 1-3, characterized inthat the control system (14) is configured to be in an off-mode andan on-mode, and that the method comprises the further step of - detecting a switch from said off-mode to said on-mode, and - as a response to said switch being detected, activating said safe operation mode.

5. A method according to any one of claims 1-3, characterized inthat the control system (14) is configured to execute the steps of the method.

6. A crane (1) comprising: - a movable arm (2), - at least one first hydraulic device (3, 4, 5) configured to move themovable arm (2), - a first hydraulic valve (6, 7, 8) configured to control the operationof the at least one first hydraulic device (3, 4, 5), - a tool (9) provided at an end of the movable arm (2), said tool (9)comprising a first part (10) and a second part (11), - a second hydraulic device (12)configured to displace said firstpart (10) in relation to said second part (11) to a holding positionin which the tool (9) is configured to hold an object, - a second hydraulic valve (13) configured to control the operationthe second hydraulic device (12), - a control system (14) comprising - a readable memory (15), - a user interface (16) configured to enable a user to controlthe movable arm (2) and the tool (9) by receiving user commands,and, - a processor (17) configured to control the first hydraulicdevice (3, 4, 5) and the second hydraulic device (12) by generatingcontrol signals to the first hydraulic valve (6, 7, 8) and to thesecond hydraulic valve (13) in response to said received usercommands, said crane being characterized in that the controlsystem (14) is configured toa) detect a first condition in which the tool (9) is in said holdingposition and the movable arm (2) is in an unloaded condition inwhich it is not actively lifting an object held by said tool (9), b) register a first point of time at which the first condition isobtained and counting a period time (t) from the first point of time, and, c) when the counted period of time (t) exceeds a threshold value(tmreshoid), activate a safe operation mode which prevents the firsthydraulic device (3, 4, 5) from moving the movable arm (2), saidsafe operation mode being deactivatable by an actuation of said second hydraulic valve (13).

7. A crane (1) according to c|aim 6, characterized in that saidactuation of the second hydraulic valve (13) is an actuation in response to a user command received via the user interface (16).

8. A crane (1) according to c|aim 7, characterized in that saidactuation of the second hydraulic valve (13) is an actuation inresponse to a user command received via the user interface (16) to apply said holding position.

9. A crane (1) according to any one of claims 6-8, characterizedin that the control system (14) is configured to be in an off-modeand an on-mode, and that the control system (14) is configured to- detect a switch from said off-mode to said on-mode, and - as a response to said switch being detected, activate said safe operation mode.

10. A crane (1) according to any one of claims 7-9, characterized in that the second hydraulic valve (13) is a directional valve.

11. A crane (1) according to c|aim 9, characterized in that saidoff-mode is a mode in which power for actuation of the first (3, 4,5) and second hydraulic devices (12) is turned off and the control system (14) is disconnected from an electric power source.

12. A crane (1) according to claim 9 or 11, characterized in that it comprises at least one pump (19) configured to deliverpressurized fluid to the first hydraulic device (3, 4, 5) and to thesecond hydraulic device (12), and that, in said off-mode, said pump is inactive.

13. A crane (1 ) according to any one of claims 7-12, characterizedin that the second hydraulic valve (13) comprises a spool, a motionof which results in said displacement of said first part (10) in relation to said second part (11) to the holding position.

14. A crane (1) 7-13,characterized in that the crane (1) comprises at least one according to any one of claims,movable boom (18) to which the arm (2) is directly or indirectlyconnected and that, in said safe operation mode, movement of said boom (18) is prevented.