HYDRAULIC ARRANGEMENT

Abstract

The invention relates to a method (50) of operating an actuated arrangement (1) including a lifting boom (3), an associated lifting actuator (4), a tool attachment device (5) for attachment of a tool (7, 23), and an associated tilting actuator (6). The torque that is exerted onto the tool attachment device (5) is calculated using the attitude of the tool attachment device (5), a mass information, representing the mass that is connected to the tool attachment device (5), and a tool type information, representing the characteristics of the tool (7, 23) that is to be attached to the tool attachment device (5).

Claims

1. A method of operating an actuated arrangement comprising a lifting boom, an associated lifting actuator, a tool attachment device for attachment of a tool, and an associated tilting actuator, wherein the torque that is exerted onto the tool attachment device is calculated using the attitude of the tool attachment device, a mass information, representing the mass that is connected to the tool attachment device, and a tool type information, representing the characteristics of the tool that is to be attached to the tool attachment device.

2. The method according to claim 1, wherein the characteristics of the tool include the length of the distance (d) between the point of rotation and the centre of gravity of the tool that is to be attached to the tool attachment device and/or the angle enclosed between the direction of the connection between the point of rotation and the centre of gravity of the tool that is to be attached to the tool attachment device and the direction of the gravity in dependence of the attitude and/or its mass.

3. The method according to claim 1, wherein the method is used for calculating a compensation signal for modifying the actuation signal that is applied to the tilting actuator, in particular for compensating the variation of the torque that is exerted onto the tool attachment device in dependence of the attitude of the tool attachment device, preferably in a way to maintain a constant rotational speed of the tool attachment device and/or for compensating the variation of the torque that is exerted onto the tool attachment device in dependence of the current mass of the tool that is connected to the tool attachment device.

4. The method according to claim 1, wherein the attitude of the tool attachment device is determined using a positional information of the lifting boom and/or of the tool attachment device, in particular using the information of at least one position sensor and/or of at least one translational position sensor and/or of at least one angular position sensor.

5. The method according to claim 1, wherein the mass that is connected to the tool attachment device is determined using a load information representing a load acting onto the lifting boom, in particular using an information from a pressure sensor, preferably a pressure sensor representing the load acting onto the lifting actuator.

6. The method according to claim 5, wherein sensor information, in particular pressure sensor information, is compensated for friction, speed and fluid flow effects, influencing the information obtained by the sensors.

7. The method according to claim 1, wherein the lifting actuator and/or the tilting actuator comprises at least a hydraulic actuator, in particular at least a hydraulic piston, or is essentially designed as a hydraulic actuator, in particular as at least a hydraulic piston.

8. The method according to claim 1, wherein using tool type information that is determined using an automated tool type identification device and/or using tool type information that is entered by an operator and/or using tool type information that comes from a movement characteristics obtained during operation of the actuated arrangement.

9. The method according to claim 1, wherein the calculation is performed using a mathematical description of the arrangement and/or that a lookup table is used for performing the calculation.

10. The method according to claim 1, wherein the actuated arrangement comprises a tool that is attached to the tool attachment device, the tool preferably taken from the group comprising forks, bale grapplers, shovels and buckets, where the tools are preferably used interchangeably.

11. A controller device, in particular electronic controller device, that is designed and arranged to perform a method according to claim 1.

12. An actuated arrangement, comprising a lifting boom, an associated lifting actuator, a tool attachment device for attachment of a tool, an associated tilting actuator, and a controller device according to claim 11.

13. A working vehicle, comprising an actuated arrangement according to claim 12.

14. The method according to claim 2, wherein the method is used for calculating a compensation signal for modifying the actuation signal that is applied to the tilting actuator, in particular for compensating the variation of the torque that is exerted onto the tool attachment device in dependence of the attitude of the tool attachment device, preferably in a way to maintain a constant rotational speed of the tool attachment device and/or for compensating the variation of the torque that is exerted onto the tool attachment device in dependence of the current mass of the tool that is connected to the tool attachment device.

15. The method according to claim 2, wherein the attitude of the tool attachment device is determined using a positional information of the lifting boom and/or of the tool attachment device, in particular using the information of at least one position sensor and/or of at least one translational position sensor and/or of at least one angular position sensor.

16. The method according to claim 3, wherein the attitude of the tool attachment device is determined using a positional information of the lifting boom and/or of the tool attachment device, in particular using the information of at least one position sensor and/or of at least one translational position sensor and/or of at least one angular position sensor.

17. The method according to claim 2, wherein the mass that is connected to the tool attachment device is determined using a load information representing a load acting onto the lifting boom, in particular using an information from a pressure sensor, preferably a pressure sensor representing the load acting onto the lifting actuator.

18. The method according to claim 3, wherein the mass that is connected to the tool attachment device is determined using a load information representing a load acting onto the lifting boom, in particular using an information from a pressure sensor, preferably a pressure sensor representing the load acting onto the lifting actuator.

19. The method according to claim 4, wherein the mass that is connected to the tool attachment device is determined using a load information representing a load acting onto the lifting boom, in particular using an information from a pressure sensor, preferably a pressure sensor representing the load acting onto the lifting actuator.

20. The method according to claim 1 wherein sensor information, in particular pressure sensor information, is compensated for friction, speed and fluid flow effects, influencing the information obtained by the sensors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further advantages, advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings, wherein the drawings show:

[0026] FIG. 1: a schematic of an embodiment of an actuated hydraulic arrangement;

[0027] FIG. 2: the mechanical section of an embodiment of an actuated hydraulic arrangement in a schematic side view with two different tools attached thereto;

[0028] FIG. 3: a block diagram of a possible embodiment of a control scheme of a compensated actuated hydraulic arrangement.

DETAILED DESCRIPTION

[0029] FIG. 1 shows a schematic arrangement of a possible embodiment of an actuated hydraulic arrangement 1. The actuated hydraulic arrangement 1 comprises a hydraulically actuated boom arrangement 2, comprising a lifting boom 3 and a tool attachment device 5 with a tool attached to it. Presently, the tool attached to the tool attachment device 5 is a shovel 7. The lifting boom 3 is actuated by a lifting hydraulic piston 4, while the tool attachment device 5 is actuated by a tilting hydraulic piston 6. The tilting hydraulic piston 6 actuates the tool attachment device 5/the shovel 7 via a Z-kinematics 8, which is known in the state of the art as such.

[0030] The movement of the hydraulically actuated boom arrangement 2 is initiated by an appropriate control input, presently made by an operator operating a control joystick 9. The control commands that are input by means of the control joystick 9 are transmitted via a vehicle bus system 10 (or by other means) to an electronic controller 11. The electronic controller 11 uses this input, together with the additional input from several sensors 12, 13, 14 and 15 (as will be discussed in detail later on) to generate output signals to a control valve arrangement 16 comprising a plurality of actuated control valves. The pressurised hydraulic oil that is needed for operation of the actuated hydraulic arrangement 1 is generated by a hydraulic pump 17.

[0031] For completeness, it should be mentioned that the hydraulic pump 17 usually supplies several additional hydraulic consumers as well. As an example for a possible hydraulic consumer, in FIG. 1 a hydraulic steering system 18 is schematically shown, where the hydraulic steering system 18 is connected to the hydraulic circuitry by means of a priority valve 19. As mentioned, this is simply shown as an example of a possible additional consumer 18, 19, were the additional consumer(s) might be optional as well (i.e. no additional consumer may be present).

[0032] Apart from the control input by the control joystick 9, in the presently shown embodiment the electronic controller 11 also receives an input from a boom angle sensor 12, a tool angle sensor 13, a first boom piston pressure sensor 14, and a second boom piston pressure sensor 15.

[0033] The boom angle sensor 12 measures the angle of the lifting boom 3 with respect to the vehicle chassis (not shown), the hydraulically actuated boom arrangement 2 is connected to. Similarly, the tool angle sensor 13 measures the angle of the tool attachment device 5 with respect to the lifting boom 3. As it is clear for a person skilled in the art, the attitude of the tool attachment device 5 (and therefore the attitude of the tool itself; presently a shovel 7) with respect to the surroundings/horizon/vehicle chassis can be determined by appropriately combining the measurement valves of boom angle sensor 12 and tool angle sensor 13. The necessary calculations may be performed by the electronic controller 11.

[0034] Further, first boom piston pressure sensor 14 (essentially) measures the hydraulic fluid pressure in the first piston chamber 21 of the lifting hydraulic piston 4 (the first piston chamber 21 increases in volume, when the lifting boom 3 is raised; consequently, during such a movement fluid flows into the first piston chamber 21 and out of the second piston chapter 22; further, during such a movement, the pressure in the second piston chamber 22 is lower than the pressure in the first piston chamber 21), while the second boom piston pressure sensor 15 (essentially) measures the hydraulic fluid pressure in the second piston chamber 22 of lifting hydraulic piston 4 (the second piston chamber 22 increases in volume, when the lifting boom 3 is lowered; consequently, during such a movement fluid flows into the second piston chamber 22 and out of the first piston chamber 21; further, during such a movement, the pressure in the second piston chamber 22 may be lower or higher than the pressure in the first piston chamber 21, depending whether a passive (gravity assisted) movement, or a positively powered movement occurs, respectively). Indeed, this may be the reason why two pressure sensors 14, 15 are employed. If a positively powered down movement situation (almost) never occurs, use of a single pressure sensor 14, 15 may prove to be sufficient (namely first boom piston pressure sensor 14).

[0035] The use of the presently shown and described sensors 12, 13, 14, 15 (i.e. boom angle sensor 12, tool angle sensor 13, first 14 and second 15 boom piston pressure sensor) is quite widespread for actuated boom arrangements of the type, presently in question.

[0036] It is further customary in the prior art that for a lowering movement of the lifting boom 3 and/or a dumping movement of a shovel 7 (equivalent to a clockwise movement in FIG. 1) gravity is used. This is done for saving energy, and also to reduce the generation of noise and to reduce wear of the various components of the actuated hydraulic arrangement 1. Therefore, a lowering movement of the lifting boom 3 is normally commanded by the electronic controller 11 (on receiving an appropriate control command from the operator via control joystick 9) by actuating the various control valves of the control valve arrangement 16 in a way that an orifice is opened so that first piston chamber 21 of lifting hydraulic piston 4 (whose pressure is measured by first boom piston pressure sensor 14) becomes fluidly connected to the fluid reservoir 20, so that hydraulic fluid can leave the respective chamber 21 towards a fluid reservoir 20. At the same time, another orifice is opened so that the second piston chamber 22 of lifting hydraulic piston 4 (whose pressure level is measured by a second boom piston pressure sensor 15) is connected to the fluid reservoir 20 as well, so that fluid from the fluid reservoir 20 can fill the increasing volume of second chamber 22 of the lifting hydraulic piston 4. The speed of the lowering movement is controlled by an appropriately chosen size of the orifices. How the variable size orifice is technically implemented is usually not of a major relevance. In particular, solutions that are known in the art may be employed. As an example, displacing of a spool (that is an actuated one) may be used for this. Preferably, there should be some kind of a continuity between the operator input and the size of the orifice. Mathematically speaking, the connection should be monotonically increasing, preferably strictly monotonically increasing.

[0037] Since the fluid flow though the respective valves of the control valve arrangement 16, which determines the linear moving speed of the lifting hydraulic piston 4, not only depends on the size of the orifices of the control valves, but also depends on the pressure differential over the respective valves, the load on the lifting boom 3 has an influence on the lowering speed as well. This is, because the load on the lifting boom 3 influences the pressure differential Δp over the valves. In detail, the formula Q=k A √{square root over (Δp)} holds, where Q is the flow through the valve, k is the valve constant, A is the opening area of the valve, and Δp is the pressure differential across the valve.

[0038] The load on the lifting boom 3, however, can be determined from the pressures measured by first 14 and second 15 boom piston pressure sensor (at least approximately). The input from these sensors 14, 15 is therefore used by the electronic controller 11 to modify the control signal inputted by control joystick 9 in a way that the lowering speed approximately only depends on the angle of the control joystick 9, and not any more on the load on the lifting boom 3.

[0039] A further modification of the presently described actuated hydraulic arrangement 1 over a standard actuated hydraulic arrangement lies in the fact that the electronic controller 11 further uses the various sensor inputs by sensors 12, 13, 14, 15 (i.e. boom angle sensor 12, tool angle sensor 13, first boom piston pressure sensor 14 and second boom piston pressure sensor 15) to calculate the torque on the tool attachment device 5 more precisely (at least approximately). It is to be noted that the torque acting on the tool attachment device 5 depends on the position of both lifting boom 3 and tool attachment device 5, the load that is currently held by the tool (and therefore approximately the load acting on the lifting boom 3, when the weight of the tool is added; however, the force is usually dependent on the position of the lifting boom 3 and of the tool attachment device 5 as well), and the type of tool that is attached to the tool attachment device 5, which will be described in more detail in the following.

[0040] Similar to the modification of the control signal for the control valve arrangement 16 by the electronic controller 11 with respect to a valve actuation for controlling the position of lifting hydraulic piston 4 (and therefore of the lifting boom 3), the input command by the control joystick 9 is modified by the electronic controller 11 as well, before it is applied to the control valve arrangement 16, when a gravity assisted movement of the tool attachment device 5 is commanded (in the presently shown embodiment of a shovel 7; this is equivalent to a clockwise rotation of the shovel 7, as shown in FIG. 1). Also similar to the lifting boom 3, a normally gravity assisted movement of the shovel 7 (clockwise rotation) might necessitate a powered movement, depending on the current situation.

[0041] In detail, using the input by the control joystick 9 and taking into account the input data from the various sensors 12, 13, 14, 15, a modified control signal is calculated and applied to the control valve arrangement 16, so that the rotation speed of the tool attachment device 5 (and therefore of the attached tool; presently a shovel 7) essentially only depends on the position of the control joystick 9, and not any more on the load contained in the shovel 7, the position of the hydraulically actuated boom arrangement 2, and/or the type of tool attached to the tool attachment device 5.

[0042] The control schematics 30 for this actuation is shown and described in more detail with reference to FIG. 3 in the following.

[0043] In accordance with FIG. 2, it is shown that the type of tool 7, 23 attached to the tool attachment device 5 has a significant influence on the torque acting on the tool attachment device 5 and consequently on the force, acting on the tilting hydraulic piston 6. In detail, FIG. 2a shows a shovel 7 being attached to the tool attachment device 5, while in FIG. 2b a bale grappler 23 is attached to the tool attachment device 5. As can be seen from FIG. 2, when comparing the two sub-FIGS. 2a, 2b, the distance d between the point of rotation 25 (between tool attachment device 5 and lifting boom 3) and the centre of gravity 24 is different for a shovel 7, as opposed to a bale grappler 23. Indeed, typically the distance d between the point of rotation 25 and the centre of gravity 24 is comparatively short for a shovel 7 (where d is typically in the order of 25 cm), while it is significantly larger in the case of a bale grappler 23 (where d is typically in the order of approximately 1 m).

[0044] FIG. 3 shows a block diagram 30 of the logical setup, how an operator input command (comprising a tilting aspect CMD.sub.tilt 31, as well as a boom moving aspect CMD.sub.boom 41) is modified before it is applied to the appropriate control valves of the control valve arrangement 16. The necessary calculations can be performed by an electronic controller 11, or a similar device.

[0045] The operator input command CMD.sub.tilt 31 (tilting aspect thereof) is first recalculated into a flow request Q.sub.CMD 33 (for example litres per minute) in a flow command calculation block 32. This flow request Q.sub.CMD is modified using the scaled flow command calculation block 34, thus generating a modified flow request Q′.sub.CMD 35. For performing this calculation, the scaled flow command calculation block 34 uses the (low-pass filtered) calculated pressure p.sub.tilt 50 in the tilting cylinder 6, the calculation thereof being described in the following. This modified flow request Q′.sub.CMD 35 is then translated into a valve actuation signal Q.sub.act 37 in a valve command block 36, and consequently applied to the respective valves of the control valve arrangement 16.

[0046] The resulting change of the attitude of the tool attachment device 5/of the attached tool 7, 23 is measured in attitude measurement block 38, using the sensor input by tool angle sensor 13 (possibly boom angle sensor 12) as well.

[0047] The attitude value X.sub.tilt 39 is fed into a forward kinematics block 40 as a first input signal.

[0048] In a second control thread, an operator input command CMD.sub.boom 41 concerning a lifting action of the lifting boom 3 is directly fed into a valve command block 42. The thus generated valve control signal Q.sub.act 43 is applied to the respective valves of the control valve arrangement 16. The resulting change of the position of the lifting boom 3 is measured 44 (for example using a boom angle sensor 12). The respective positional signal X.sub.boom 45 is fed into the forward kinematics 40 as a second input value.

[0049] It is to be noted that in the presently shown example, the commanding signal CMD.sub.boom 41 for the lifting boom 3 is not compensated before being applied to the lifting hydraulic piston 4. While this is certainly possible, presently it is mainly done for simplifying the explanation. Certainly, the commanding signal CMD.sub.boom 41 for the lifting boom 3 can be compensated similarly to the commanding signal CMD.sub.tilt 31 for the tilting actuator 6, like it is described above.

[0050] In parallel, the positional information of the lifting boom X.sub.boom 45, and preferably also the pressure information p.sub.boom 46, concerning lifting hydraulic piston 4 (and possibly measured by first 14 and second 15 piston pressure sensor) are fed into a speed and friction compensation block 47. Here, the contribution in pressure differences occurring from friction and/or speed/flow of the hydraulic oil is compensated for with input from the measured cylinder speed. The measured cylinder speed may be simply based on the derivative dX.sub.boom/dt. However, some more complicated mathematical connection is possible as well. As an example, the non-linearity between the position/positional angle of the lifting boom 3 and the linear/translational speed of the hydraulic piston 4 may be considered in this context. It is to be noted that this speed and friction compensation block 47 is optional; but it improves the accuracy of the compensation.

[0051] The forward kinematics 40 uses the positional information X.sub.tilt, X.sub.boom 39, 45 from the various sensors, calculates the positions q.sub.act 48 of the different bodies/elements of the hydraulic actuated boom arrangement 2 and forwards the respective data to a tilting hydraulic piston pressure calculation block 49. There, the estimated tilt cylinder pressure p.sub.tilt 50 is calculated. This is sort of equivalent to the torque that acts on the point of rotation 25 of the tool attachment device 5. The thus calculated estimated tilt cylinder pressure p.sub.tilt 50 is passed through a low pass filter 51 (to avoid undesired oscillations in the command signals) and is then fed to the scaled flow calculation block 34, where it is used as an additional input (as a reminder: the main input is the commanded flow Q.sub.CMD 33) for compensating the commanded fluid flow Q′.sub.CMD 35 to the respective actuated valves of the control valve arrangement 16.

[0052] While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.