Patent ID: 12221327

DETAILED DESCRIPTION

FIGS.1,2and3show a pick and carry crane10. The crane10has a front body12which is the front part of the crane10. The front body12is pivotally connected via a pivot arrangement30(exemplified by the dashed line inFIGS.2and3) to a rear body14of the crane10. The pivot point30is provided with moveable linkages (hydraulic rams in this instance although other linkages are known), to control the pivot angle of the front body12to the rear body14. Adjusting the pivot angle using the moveable linkages helps to turn the crane10.

A side tipping line34(seeFIG.4) is defined when the front body12is pivoted relative to the rear body14.

In the embodiment of the pick and carry crane10as depicted in the Figures, the side tipping line34is an imaginary longitudinal axis that extends between a point at which the outer tyres T1 of the front body contact the ground, via wheel20, and a point at which the outer tyre T3 of the rear body contacts the ground, via wheel18. Thus, the tyres T1 and T3 of the wheels20and18define the points about which the crane may topple sideways. The crane10includes two sets of rear tyres T3 and T2. In this embodiment, the foremost set T3 is used to define the tipping line as the rearmost set T2 can be lifted during a taxi mode so that those tyres are no longer in contact with the road or other travel surface.

The pick and carry crane illustrated has three axles, but is to be realised that in different embodiments, the mobile crane may have two axles, or more than three axles.

Attached to the rear end of the front body12is a boom support arm24. The boom support24may be a separate structure that is mounted e.g. welded or bolted to the front body12. In an embodiment, the boom support arm24forms part of the chassis of the front body12. The boom support arm24pivotally supports boom26, where the boom26is raised and lowered about the pivot point, represented by pin27(FIG.2), using linear actuators in the form of hydraulic rams28A and28B, between the front body12and the boom26. The boom26is telescopic. Other forms of linear actuators and booms can be used in place of or in addition to rams28and boom26.

FIG.5illustrates the joins between the boom26and the boom support arm24. Embodiments employ boom articulation which allows both up and down articulation as well as side to side articulation of the boom. In the embodiment illustrated inFIG.5, a dual articulation joint40provides both forms of articulation.

In this embodiment, the lateral movement of the boom26is restricted to 5° either side of the vertical so that the total lateral movement of the boom is restricted to 10°.

In an alternate embodiment, the total lateral movement of the boom is restricted to 20°, 10° to either side of the vertical.

FIG.6illustrates the lateral articulation of the boom26at an angle α. As shown the pick and carry crane12is here depicted on slanted terrain ‘G’ at an angle θ relative to the horizon. The slope of the terrain ‘G’ will move the centre of gravity away from the centre of the pick and carry crane, thereby increasing the tipping moment, destabilising the crane. By laterally articulating the boom26as illustrated, the centre of gravity is brought back towards the centre of the crane, thereby reducing the tipping moment and potentially improving the stability.

In alternate embodiments, the extent of the lateral movement may be set depending on a number of factors such as the maximum length of the boom when extended, the capacity of the crane, operating conditions etc.

The hydraulic rams28A and28B control both the up and down articulation of the boom26as well as the lateral articulation. For certain embodiments there may be an advantage to using hydraulic rams to control both up and down, and lateral articulation since known pick and carry cranes include such hydraulic rams. Therefore, it is not necessary to develop and install a new articulation mechanism to accommodate the lateral articulation in addition to the existing up and down articulation.

Features of pick and carry cranes relating to the control of tipping are described in PCT/AU2014/000261, PCT/AU2017/050999, AU2018903904 and AU2019903890, the contents of which are incorporated herein. It is to be realised that the lateral articulation of the boom as herein described could be incorporated in the tipping prevention considerations and controls discussed in those applications.

FIG.7illustrates a system100for controlling an operation of the mobile crane10. The system comprises two user controls114A and114B connected to a determinator112. Two actuators118A and118B are also connected to the determinator112as are two sensors116A and116B. In use a user will actuate one of the user controls114A or114B which sends a command to the determinator112. The determinator112will process that command in the manner described below, and if appropriate actuate the corresponding actuator.

In the embodiment illustrated, each user control114A and114B corresponds to an actuator so user control114A may actuate actuator118A and user control114B may actuate actuator118B.

The determinator112receives input from the sensors116A and116B and uses this input in the manner described below.

FIG.7is schematic in nature. The user controls may correspond to the control of any one of the following functions of the mobile crane10:a speed of the mobile crane;a luff angle of the boom26of the mobile crane;an extension of the boom26;an articulation of the front chassis or body10of the mobile crane relative to a back chassis or body14of the mobile crane;an activation of a winch of the mobile crane; ora lateral articulation angle of the boom26of the mobile crane.

The mobile crane is driven by altering the speed and the steering which corresponds to an articulation of the front chassis relative to the rear chassis. As the mobile crane traverses different terrain, the pitch and roll of the front and rear chassis may be affected and therefore, the pitch and roll of the front and rear chassis are further characteristics of the mobile crane which may be affected by user input.

Therefore, the user controls114A and114B correspond, for example to a luff up/down lever, or a boom extend/retract lever. The manner in which each of the above functions (characteristics) of the crane is controlled is known in the art and will not be further described herein. For the current description it is sufficient to note that each user control will actuate a corresponding actuator118A and118B. Each command issued by a user control will generally have a direction and a magnitude associated with it.

So, if a user control corresponds to luff up/luff down, then the corresponding actuator will be the hydraulic rams28A and28B.

The determinator112comprises a central processing unit120connected to storage122. When a command is received by the determinator112from a user control114A, the determinator will initially evaluate the current tipping moment of the crane. In this embodiment, the tipping moment is evaluated by determining the position of the centre of gravity of the crane relative to the tipping line34. It is to be realised that there are three other tipping lines which may be relevant, with reference toFIG.4the four lines joining the outer tyres in contact with the travel surface. In practice it is only the side tipping lines which are relevant since the mobile crane is exceedingly unlikely to tip over forwards or backwards due to the weight distribution.

Therefore, in this embodiment, the tipping moment is calculated by first determining the distance between the centre of gravity to the closest side tipping line. However, in further embodiments, the calculation may be repeated for the forward and backward tipping lines.

The position of the centre of gravity may not always be known precisely. In an embodiment, the tipping moment is estimated by determining the position of the top of the boom based on sensor or usage data and assuming that the load is located directly below the attachment point to the boom. The vertical position of the load relative to the attachment point may be estimated based on sensor or usage data for the winch. In an embodiment, the centre of gravity is determined based on the weight of the load, the angle and extension of the boom, and the vertical height of the load.

In this embodiment, the tipping moment is calculated as:

Distance from load to tipping line * weight of the suspended load

It is to be realised that, for best results, both vertical and lateral distances between the tipping line and the load are taken into account.

The determinator112will then compare the determined tipping moment to a predetermined amount. In this embodiment, since an approximation is used the predetermined amount is set as 90% of the rated capacity of the crane. This will provide sufficient leeway to account for most errors.

The determinator will then predict an effect of the user input on the tipping moment of the mobile crane. To do this, the determinator112will effectively run a simulation whereby it assumes that the command corresponding to the user input is carried out and determines the effect of this on the tipping moment. To do so, the determinator stores a mathematical model of the mobile crane including the position of the load, determines how the command would change the configuration of the crane including the position of the load, articulation of the crane and, if applicable, the pitch and roll of the front and read chassis, and then recalculates the tipping moment in the manner described above.

If the determinator then determines that the user's command will result in the tipping moment exceeding the predetermined amount (90% of the rated capacity), the determinator will alter a response to the user input. It is to be realised that the manner in which the response to the user input is altered will depend on the user input. However, in certain embodiments, where the command issued by a user control has a direction and a magnitude associated with it, the determinator will alter either or both of the direction and the magnitude.

For example, if the operator actuates the luff up/down lever to execute a command to raise the boom by 20° and the determinator determines that this command would cause the tipping moment to exceed the predetermined amount, then the command may be restricted to 4°. Alternatively, the determinator will determine the maximum allowable and substitute that instead.

In a further example, the operator actuates the luff up/down control, but this control is restricted to controlling a speed of the boom luff and has 10 different speeds and a direction (up or down). In this case, the determinator may predict the effect of the command over a predetermined time (e.g. 30s) and evaluate the change to the tipping moment of the crane over that predetermined time and, if the tipping moment exceeds the predetermined amount then restrict the speed of the change in the boom luff, for example.

In further example, the time period used by the determinator will depend on the evaluation of the current tipping moment. If it is determined that the current tipping moment is close to the predetermined amount, then the time period over which the effect of the command is predicted will be shorter than if the current tipping moment is further away from the predetermined amount.

In a further embodiment, the determinator evaluates the rate of change of the tipping moment. This may be a more accurate determination of whether the crane is in imminent danger of tipping since, particularly with variables such as a change in the roll of the chasses, the tipping moment can be affected exponentially if the boom is extended and has a relatively large luff angle.

In an embodiment, the velocity of the boom head is determined and used as an approximation of the rate of change of the tipping moment. If the velocity of the boom head compared to the current tipping moment

In the determination of the tipping moment as described, it is necessary to know the position of the load. In an embodiment, it is assumed that the load is positioned vertically below the attachment point to the boom, and the attachment point of the boom is calculated using sensors which determine the angle and extension of the boom, height of the load, and the articulation of the crane. In an alternate embodiment, usage data is used to determine the current configuration of the crane (angle and extension of the crane).

In a further embodiment, the crane includes sensors which determine the position, velocity and acceleration of the load, and these measurements are used to determine the tipping momentum. An advantage of such an embodiment may be that any swing in the load can be determined and combined with the determination of the tipping moment. Since a small variation of the configuration of the crane can result in large changes to the swing in the load, particularly when the articulation and boom orientation are away from the resting position (no articulation, boom down and fully retracted).

In these circumstances, determination of the swing of the load may be used to restrict the response to a user command when the load is in a position which tends to increase the tipping moment. In an embodiment, the manner in which the command is executed may reduce the load swing, in particular when the command relates to lateral articulation of the boom.

It is to be realised that in further embodiments, refinements are possible. For example the determinator may alter a response to the user input in dependence on a difference between the determined tipping moment and the predetermined amount. So, if that difference is large, the command corresponding to the user input is not restricted, but as the difference gets smaller, the restriction increases until, when the predetermined amount has been reached, the user input is blocked entirely.

In certain embodiments, the future tipping moment may be calculated. If, for example, it is known that the configuration may change in future, those changes may be taken into account when calculating the tipping moment. For example, if it is known that the configuration of the crane will change due to characteristics of the terrain that the crane will transverse, these may be taken into account when calculating the tipping moment.

FIG.8illustrates a user display130connected to the determinator100. In this embodiment, the user display130comprises three display elements132A,132B and132C. Each display element corresponds to a different command initiated by a user input. So, in this embodiment, display element132A corresponds to luff up; display element132B corresponds to luff down and display element132C corresponds to boom extend.

As the user initiates the user input, the determinator determines a current tipping moment of the mobile crane and predicts an effect of the user input on the tipping moment of the mobile crane; and if the predicted effect of the user input is to increase the tipping moment of the mobile crane past a predetermined amount. This is done in the manner described above. The determinator will then designate a first range of the effect of the user input as a safe range and a second range of the effect of the user input as a warning range. For example, for the first range, the designator may determine that a tipping moment within 75% of the predetermined amount is safe and a tipping moment between 75% and 100% of the predetermined amount is a warning zone.

It is to be realised therefore that the predetermined amount corresponds to a tipping condition for the mobile crane (in other words a set of configurations of the crane where there is a high likelihood that the crane will tip, taking such variables into account such as the swing on the load and uneven distribution of the load).

The determinator will then divide up the corresponding display element into two portions and display the available range of the corresponding command as corresponding display portions which are represented in dependence on a relation between the range corresponding to the safe zone and the range corresponding to the warning zone.

For example, if the user initiates a luff up command, then the determinator will determine the amount of luff up which can be safe executed and an amount which will bring the crane close to tipping. If, for example, it determines that the safe zone is 5° from the current position and the warning zone is a further 15° beyond that, the display element132A will be divided into two portions:134A and136A showing the operator the relative safe zone remaining in that aspect of the operation of the mobile crane.

This may provide the operator with a quick and intuitive representation of the available safe operation of the crane.

In this embodiment, the portion136A corresponding to the warning zone is displayed in red, and the portion134A corresponding to the safe zone is displayed in green. This may make it more intuitive for an operator to evaluate.

In this embodiment, the display is continuously updated as the configuration of the crane changes. If the user's operation tends to increase the tipping moment, the user will see the corresponding warning portions of the display increasing. Furthermore, as the configuration of the crane changes over time, the user will see corresponding changes to the warning portions of the display.

When a plurality of user inputs is represented on the screen, as shown inFIG.8(only three examples are shown; it is to be realised that many more may be shown), the user is provided with a representation which may be quickly evaluated.

This aspect may be usefully combined with the previous aspect of altering a response to a user input. In an embodiment, the user may experience reduced responsiveness to a command as the red regions on the display grow in size.

In a further embodiment, the display elements may be broken into three regions, and the determinator calculates a safe zone, a warning zone and a no-go zone. In this embodiment, the portion corresponding to the safe zone may be represented in green, the portion corresponding to the warning zone represented in orange and the portion corresponding the no-go zone represented in red.

FIG.9illustrates a display160according to a further embodiment. The display160represents the terrain over which the crane may move. This may be derived from mapping data, from radar, or elsewhere. In the embodiment illustrated, the ground has a flat portion142and an inclined portion144. Using range and altitude information, the determinator divides the terrain into regions which do not affect the tipping moment (regions144) and regions which do affect the tipping moment, but which are acceptable in the current configuration (regions146) and regions which would cause the crane to tip in the current configuration (regions148).

The determinator classifies the terrain regions by determining the effect of the incline on the pitch and roll of the front and back chassis, calculating the tipping moment for those values (assuming that the remaining configuration stays the same) and comparing those against the predetermined value (here also 90% of the rated capacity).

In an embodiment, the effect of the user input may be varied depending on how close the crane configuration is to tipping, or how fast the tipping moment is approaching a tipping condition. It is to be realised that this may be done with any user input, but finds particular application to those user inputs where the user is able to determine a rate of change as well as a direction of change. With reference to the terrain depiction ofFIG.9, one set of examples where the effect of the user input may be reduced relates to control of the speed and direction of the crane.

If the user, for example, selects that the mobile crane should undergo maximum forward acceleration (by placing their foot flat on the accelerator pedal), and the determinator determines that there is a close undulation in the terrain, which if the mobile crane were to traverse, would result in a tipping condition, then the determinator would not provide the full acceleration to the user, but would, for example, only provide half of the available acceleration.

Similar considerations might apply to steering and other changes to the configuration of the mobile crane.

It is to be realised that the amount by which the effect of the user input is throttled may depend on the current configuration of the mobile crane. The closer the current configuration is to a tipping state, the more the effect will be throttled.

FIG.10illustrates a display200according to a further embodiment. The display200includes a representation of the mobile crane. In this embodiment, the display comprises a display element202which shows the safe zones for boom extension and luff (collectively forming the radius of the load relative to the body of the crane), and crane articulation. The display element202has two dimensions ‘x’ and ‘y’ where the x-dimension corresponds to the radius formed by boom extension and luff and the y-dimension corresponds to articulation. As shown, the element202is divided into display portions202,204,206,208and210of decreasing danger of crane configuration. Marker250shows the current position of the end of the boom and therefore represents the current configuration of the mobile crane.

The display element202is generated by the determinator which calculates how changes to the current configuration would affect the tipping moment of the crane. The display element202is broken down into a series of pixels (which may, or may not correspond to the display pixels on the display concerned), each pixel representing a radius and length of the boom. In this embodiment, each pixel represents a 0.1 m change in the radius and 5° change in the articulation, but in further embodiments a coarser or finer resolution may be used.

For each of these pixels, a tipping moment for the crane is calculated and categorised according to how likely the crane is to tip in that configuration. To convey the tipping likelihood to the user, each pixel is assigned a colour according to the corresponding likelihood. In the embodiment illustrated, red is chosen for those configurations which would almost certainly lead to tipping; pink for those less likely to lead to tipping; light green for configurations almost certainly safe; and dark green for those configurations which are safe.

If the crane is in the corresponding configuration then increasing either the articulation or the boom extension will tend to move the crane towards tipping over, as reflected in the severity rating of that portion. A key220shows the severity rating, in this case designated by a corresponding colour. In the drawing shown the key220is labelled “Hook Load (tonne)”. However, in this embodiment, the load weight has been determined and incorporated into the calculations of the pixel colours for the display element202. Therefore, a more correct labelling for the key202would be “Percentage Rated Capacity” as this is intended to show the relative amount of rated capacity available to the operator.

It is to be realised that, in this embodiment, the determinator predicts the effect that boom extension and luff, and articulation would have on the tipping moment. For the purposes of determining the pixel colours, an assumption is made that the roll and pitch of the crane will remain constant.

However, as the roll and pitch of the crane change, the display element202will be updated.

FIG.11illustrates a display300with a display portion302similar to the display portion202ofFIG.10, but for a different model of crane. The display element302differs from the display element202in that the different colour regions are not symmetrically arranged around the boom. This is because in this configuration, the crane is situated on uneven terrain (a 3° slope, as shown in the display300) so that the tipping moment is unsymmetrical with respect to the boom.

In general, the display200or300will update as the pitch and roll of the crane changes over time, to reflect to the user how changes in the configuration can affect the tipping moment.