METHOD OF CONTROLLING WORKING MACHINE, CONTROL SYSTEM AND WORKING MACHINE

Abstract

The invention relates to a method of controlling a working machine. The working machine comprises a first power source arranged to drive a mechanical driveline, a hydraulic system comprising a hydraulic pump and an actuator arranged to be driven to move by the hydraulic pump, where the hydraulic pump is separated from, or disconnectable from, the first power source. The method comprises determining whether the working machine is in an increased response mode. The method further comprises increasing a response of the hydraulic system upon determining that the working machine is in the increased response mode.

Claims

1. A method of controlling a working machine comprising a first power source arranged to drive a mechanical driveline, a hydraulic system comprising a hydraulic pump and an actuator arranged to be driven to move by the hydraulic pump, where the hydraulic pump is separated from, or disconnectable from, the first power source, the method comprising: determining whether the working machine is in an increased response mode; and increasing a response of the hydraulic system upon determining that the working machine is in the increased response mode.

2. The method according to claim 1, wherein the increase of the response comprises increasing a rotational speed of the hydraulic pump.

3. The method according to claim 1, wherein the increase of the response comprises changing a filter for a lever signal from an actuator lever for operating the hydraulic system.

4. The method according to claim 1, wherein the working machine comprises a bucket, and wherein the increased response mode is an excavation mode.

5. The method according to claim 1, wherein the determination of whether the working machine is in the increased response mode is made based on one or more of: a kickdown signal; a disconnection of a hydraulic energy storage of the hydraulic system; a position of the actuator; a gearshift pattern; an acceleration signal from an accelerator pedal; a speed pattern of a traveling speed of the working machine; and detection data from a detection device.

6. The method according to claim 1, further comprising decreasing the response upon determining that the working machine is no longer in the increased response mode.

7. The method according to claim 1, wherein the working machine comprises a second power source arranged to drive the hydraulic pump, and wherein the first power source is arranged to operate independently of the second power source.

8. The method according to claim 1, wherein the working machine is a wheel loader.

9. A control system for controlling a working machine comprising a first power source arranged to drive a mechanical driveline, a hydraulic system comprising a hydraulic pump and an actuator arranged to be driven to move by the hydraulic pump, where the hydraulic pump is separated from, or disconnectable from, the first power source, the control system comprising at least one data processing device and at least one memory having at least one computer program stored thereon, the at least one computer program comprising program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform the step of: determining whether the working machine is in an increased response mode; and commanding increase of a response of the hydraulic system upon determining that the working machine is in the increased response mode.

10. The control system according to claim 9, wherein the increase of the response comprises increasing a rotational speed of the hydraulic pump.

11. The control system according to claim 9, wherein the increase of the response comprises changing a filter for a lever signal from a manual actuator lever for operating the hydraulic system.

12. The control system according to claim 9, wherein the determination of whether the working machine is in the increased response mode is made based on one or more of: a kickdown signal; a disconnection of a hydraulic energy storage of the hydraulic system; a position of the actuator; a gearshift pattern; an acceleration signal from an accelerator pedal; a speed pattern of a traveling speed of the working machine; and detection data from a detection device.

13. The control system according to claim 9, wherein the at least one computer program comprises program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform the step of: commanding a decrease of the response upon determining that the working machine is no longer in the increased response mode.

14. A working machine comprising: a mechanical driveline; a first power source arranged to drive the mechanical driveline; a hydraulic system comprising a hydraulic pump and an actuator arranged to be driven to move by the hydraulic system, where the hydraulic pump is separated from, or disconnectable from, the first power source; and a control system according to claim 9.

15. The working machine according to claim 14, wherein the working machine comprises a bucket, and wherein the increased response mode is an excavation mode.

16. The working machine according to claim 14, wherein the working machine comprises a second power source arranged to drive the hydraulic pump, and wherein the first power source is arranged to operate independently of the second power source.

17. The working machine according to claim 14, wherein the working machine is a wheel loader.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

[0040] In the drawings:

[0041] FIG. 1 schematically illustrates a side view of a wheel loader according to the invention;

[0042] FIG. 2 is a block diagram illustrating components of the wheel loader;

[0043] FIG. 3 schematically illustrates a side view of the wheel loader and a pile;

[0044] FIG. 4 schematically illustrates a side view of the wheel loader when traveling towards the pile in an increased response mode;

[0045] FIG. 5a is a schematic and illustrative diagram of a lifting lever signal versus time;

[0046] FIG. 5b is a schematic and illustrative diagram of the speed of a hydraulic pump according to the prior art and the speed of a hydraulic pump of the invention as a function of the lifting lever signal in FIG. 5a; and

[0047] FIG. 6 is a flowchart outlining the general steps of the method according to the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0048] In the following, a method of controlling a working machine, a control system for controlling a working machine, and a working machine comprising a control system, will be described. The same reference numerals will be used to denote the same or similar structural features.

[0049] FIG. 1 schematically illustrates a side view of a wheel loader 10 according to the invention. The wheel loader 10 is one example of a working machine according to the invention. The wheel loader 10 comprises a mechanical driveline 12 and a hydraulic system 14.

[0050] The wheel loader 10 of this example comprises a front body section 16 and a rear body section 18, which sections each has an axle for driving a pair of wheels 20. The rear body section 18 comprises a cab 22. The body sections 16, 18 are connected to each other in such a way that they can pivot in relation to each other around a vertical axis by means of two first actuators in the form of hydraulic cylinders 24, 26 arranged between the two body sections 16, 18. The hydraulic cylinders 24, 26 are thus arranged one on each side of a horizontal centerline of the wheel loader 10 in a traveling direction in order to tum the wheel loader 10.

[0051] The wheel loader 10 of this example further comprises an equipment 28 for handling objects or material 30. The equipment 28 comprises a load-arm unit 32, also referred to as a linkage, and an implement in the form of a bucket 34 fitted on the load-arm unit 32. A first end of the load-arm unit 32 is pivotally connected to the front body section 16. The bucket 34 is pivotally connected to a second end of the load-arm unit 32. The load-arm unit 32 with the bucket 34 thereon can be raised and lowered relative to the front body section 16 by means of two boom or lifting hydraulic cylinders 36a, 36b, each of which is connected at one end to the front body section 16 and at the other end to the load-arm unit 32. The bucket 34 can be tilted relative to the load-arm unit 32 by means of a bucket or tilting hydraulic cylinder 36c. The wheel loader 10 is mainly used to move material 30 from one position to another. The initial position is often a pile of some material 30, and the other position is a load receiver.

[0052] The wheel loader 10 of this example further comprises a camera device 38.

[0053] The camera device 38 is one example of a detection device according to the invention. As shown in FIG. 1, the camera device 38 is here positioned on the cab 22 but may be positioned elsewhere on the wheel loader 10. The camera device 38 faces in a forward direction.

[0054] FIG. 2 is a block diagram illustrating some components of the wheel loader 10.

[0055] The wheel loader 10 of this example comprises a first power source 40, a second power source 42 and a control system 44 for controlling each of the first power source 40 and the second power source 42. Each of the first power source 40 and the second power source 42 is here exemplified as an electric motor. One or both of the first power source 40 and the second power source 42 may alternatively be, for example, an internal combustion engine.

[0056] The first power source 40 is configured to drive the mechanical driveline 12. As shown in FIG. 2, the mechanical driveline 12 of this example comprises a gearbox 46. The gearbox 46 is in signal communication with the control system 44. The gearbox 46 may comprise a torque converter .

[0057] The hydraulic system 14 of this specific example comprises a lifting hydraulic pump 48a for hydraulically driving the lifting hydraulic cylinder 36a, a lifting hydraulic pump 48b for hydraulically driving the lifting hydraulic cylinder 36b, and a tilting hydraulic pump 48c for hydraulically driving the tilting hydraulic cylinder 36c. Each hydraulic pump 48a-48c is configured to provide pressurized hydraulic oil to its associated hydraulic cylinder 36a-36c. Each hydraulic cylinder 36a-36c is an example of an actuator according to the invention. The first power source 40 is configured to drive the hydraulic pumps 48a-48c. As shown in FIG. 2, each hydraulic cylinder 36a-36c is separated from the first power source 40. The first power source 40 and the second power source 42 operate independently.

[0058] The hydraulic system 14 of this specific example further comprises a suspension accumulator 50a associated with the lifting hydraulic cylinder 36a, and a suspension accumulator 50b associated with the lifting hydraulic cylinder 36b. Each suspension accumulator 50a, 50b is an example of a hydraulic energy storage according to the invention. Each suspension accumulator 50a, 50b is configured to store and release hydraulic energy. To this end, the hydraulic system 14 further comprises a disconnection valve 52a associated with the suspension accumulator 50a, and a disconnection valve 52b associated with the suspension accumulator 50b. Each disconnection valve 52a, 52b is here exemplified as an on-off valve. Each disconnection valve 52a, 52b is controlled by the control system 44.

[0059] The hydraulic system 14 of this specific example further comprises a lifting valve arrangement Ma associated with the lifting hydraulic cylinder 36a, a lifting valve arrangement 54b associated with the lifting hydraulic cylinder 36b, and a tilting valve arrangement Mc associated with the tilting hydraulic cylinder 36c. Each valve arrangement 54a-54c is configured to control oil flow to and from chambers of the respectively associated hydraulic cylinders 36a-36c. Each valve arrangement 54a-54c is here exemplified as a 5/3 directional control valve. Each valve arrangement 54a-54c is controlled by the control system 44.

[0060] It should be understood that the hydraulic system 14 in FIG. 2 is merely one of many examples. According to one example, one of the hydraulic pumps 48a-48c hydraulically drives a plurality of the hydraulic cylinders 36a-36c. According to a further example, the hydraulic system 14 comprises two tilting hydraulic cylinders 36c. According to a further example, one of the suspension accumulators 50a, 50b is associated with both lifting hydraulic cylinders 36a, 36b.

[0061] The wheel loader 10 further comprises a transmission 56. The transmission 56 is configured to transmit a rotation of an output shaft of the second power source 42 to a rotation of each input shaft of the hydraulic pumps 48a-48c. To this end, the transmission 56 may comprise a gear train. FIG. 2 further shows a rotational speed 58 of the hydraulic pumps 48a-48c. Since the first power source 40 is separated from, and works independently of, the second power source 42, the hydraulic system 14 is a decoupled hydraulic system.

[0062] The control system 44 of this example comprises a data processing device 60 and a memory 62 having a computer program stored thereon. The computer program comprises program code which, when executed by the data processing device 60, causes the data processing device 60 to perform, or command performance of, various steps according to the invention.

[0063] The wheel loader 10 of this specific example further comprises an optional manual gearshift lever 64. The gearshift lever 64 is configured to send a gearshift signal 66 to the control system 44 indicative of a position of the gearshift lever 64. The control system 44 controls the gearbox 46 based on the gearshift signal 66.

[0064] The wheel loader 10 of this specific example further comprises a manual kickdown button 68. When actuated, a kickdown signal 70 is sent to the control system 44. The control system 44 controls the gearbox 46 based on the kickdown signal 70.

[0065] The wheel loader 10 of this specific example further comprises a manual disconnection button 72. When actuated, a disconnection signal 74 is sent to the control system 44. The control system 44 controls the disconnection valves 52a, 52b based on the disconnection signal 74.

[0066] The wheel loader 10 of this specific example further comprises a manual lifting actuator lever 76a. When actuated, a lifting lever signal 78a indicative of a position of the lifting actuator lever 76a is sent to the control system 44. The control system 44 controls the lifting hydraulic cylinders 36a, 36b based on the lifting lever signal 78a.

[0067] The wheel loader 10 of this specific example further comprises a manual tilting actuator lever 76b. When actuated, a tilting lever signal 78b indicative of a position of the tilting actuator lever 76b is sent to the control system 44. The control system 44 controls the tilting hydraulic cylinder 36c based on the tilting lever signal 78b.

[0068] FIG. 2 further shows a filter 80a for use by the control system 44 to control the lifting valve arrangement Ma based on the lifting lever signal 78a, a filter 80b for use by the control system 44 to control the lifting valve arrangement 54b based on the lifting lever signal 78a, and a filter 80c for use by the control system 44 to control the tilting valve arrangement Mc based on the tilting lever signal 78b.

[0069] The wheel loader 10 of this specific example further comprises an accelerator pedal 82. When actuated, an acceleration signal 84 indicative of a position of the accelerator pedal 82 is sent to the control system 44. The control system 44 controls the first power source 40 based on the acceleration signal 84. Upon receiving the kickdown signal 70, the control system 44 controls the mechanical driveline 12 to perform a gear down shift given that a traveling speed of the wheel loader 10 is below a threshold value.

[0070] FIG. 2 further shows the camera device 38. The camera device 38 is configured to send image data 86, as captured by the camera device 38, to the control system 44. The image data 86 is one example of detection data according to the invention. In this example, the control system 44 is configured to perform image processing based on the image data 86 to extract environmental information outside the wheel loader 10.

[0071] FIG. 3 schematically illustrates a side view of the wheel loader 10 and a pile 88. The phase when the bucket 34 is loaded in the pile 88 is called an excavation phase. During the excavation phase, the wheel loader 10 may approach the pile 88 with lowered, stationary bucket 34.

[0072] In FIG. 3, the wheel loader 10 is in a normal response mode 90. In the normal response mode 90, the power output to the hydraulic system 14 may be low, or even zero, even if the power output to the mechanical driveline 12 is substantial. The hydraulic system 14 is thus at standby in the normal response mode 90. In the normal response mode 90, the rotational speeds 58 of the hydraulic pumps 48a-48c are low or zero. In this way, energy consumption is low in the normal response mode 90. Furthermore, the disconnection valves 52a, 52b are open in the normal response mode 90 such that each hydraulic cylinder 36a-36c is in fluid communication with the respectively associated suspension accumulator 50a, 50b. This reduces the stiffness of the load-arm unit 32.

[0073] FIG. 4 schematically illustrates a side view of the wheel loader 10 when traveling towards the pile 88. Arrow 92 indicates the traveling speed of the wheel loader 10. Before the wheel loader 10 reaches the pile 88, the wheel loader 10 is prepared for digging in the pile 88. In order to prepare for the excavation phase, the driver of the wheel loader 10 may for example perform one or more actions that can be used to trigger a shift from the normal response mode 90 to an excavation mode 94. The excavation mode 94 is one example of an increased response mode 96 according to the invention. Identification of the excavation mode 94 can be made based on one or a combination of the following triggers.

[0074] The driver may for example push the kickdown button 68 to prepare the wheel loader 10 for the excavation phase. According to the invention, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 upon receiving the kickdown signal 70. The kickdown signal 70 can thus be used as a trigger for the excavation mode 94.

[0075] As a further example, the driver may push the disconnection button 72 to disconnect the suspension accumulators 50a, 50b in order to make the hydraulic cylinders 36a-36c more stiff in preparation for the excavation phase. The control system 44 thereby commands a closing of the disconnection valves 52a, 52b. This improves the ability to force the bucket 34 into the pile 88. According to the invention, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 upon receiving the disconnection signal 74. The disconnection of any of the suspension accumulators 50a, 50b can thus be used as a trigger for the excavation mode 94.

[0076] As a further example, the suspension accumulators 50a, 50b may be disconnected automatically, i.e., without manually pushing the disconnection button 72.

[0077] Such automatic disconnection can for example be made based on a selected gear, a direction of travel, the kickdown signal 70, a travelling speed or a combination thereof. According to the invention, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 upon issuing such automatic disconnection signal to any of the suspension accumulators 50a, 50b. Also in this way, the disconnection of any of the suspension accumulators 50a, 50b can be used as a trigger for the excavation mode 94.

[0078] As a further example, the driver may lower the load-arm unit 32 in preparation for the excavation phase. According to the invention, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 based on a position of one or more of the hydraulic cylinders 36a-36c. The position of at least one of the hydraulic cylinders 36a-36c can thus be used as a trigger for the excavation mode 94.

[0079] As a further example, the driver may perform a gearshift, for example from the second gear to the first gear in preparation for the excavation phase. The wheel loader 10 may be configured to use a second gear as a base gear. A gearshift pattern where the wheel loader 10 shifts from second gear to the first gear can at least partially be used as an indication that a higher response of the hydraulic system 14 is requested. For example, the shift to the first gear in combination with one or more of a traveling speed 92 of the wheel loader 10 being above or below a threshold value, and a requested torque of the first power source 40 being above or below a threshold value, can be used to trigger the increased response mode 96. According to the invention, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 based on a gearshift pattern. The gearshift pattern can thus be used as a trigger for the excavation mode 94.

[0080] As a further example, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 based on the acceleration signal 84. The driver may for example accelerate or decelerate the wheel loader 10 in a characteristic way prior to digging into the pile 88. The acceleration signal 84 can thus be used as a trigger for the excavation mode 94.

[0081] As a further example, a speed pattern of the wheel loader 10 that is characteristic for the excavation phase can be used to determine an imminent excavation phase. The driver may for example decelerate towards the pile 88 after having changed traveling direction from rearward to forward. According to the invention, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 based on a speed pattern. The speed pattern of a traveling speed 92 of the wheel loader 10 can thus be used as a trigger for the excavation mode 94.

[0082] As a further example, image data 86 from the camera device 38 can be used to determine an imminent excavation phase. Based on the image data 86, the control system 44 may for example determine that the wheel loader 10 approaches the pile 88. According to the invention, the control system 44 can determine that the wheel loader 10 is in the excavation mode 94 based on the image data 86 from the camera device 38. The image data 86 can thus be used as a trigger for the excavation mode 94.

[0083] Once the control system 44 determines that the wheel loader 10 is in the increased response mode 96, here the excavation mode 94, the control system 44 controls a response of the hydraulic system 14 to increase. When the response is increased, the hydraulic cylinders 36a-36c will react immediately to movements of the lifting actuator lever 76a and/or the tilting actuator lever 76b. In this way, the wheel loader 10 is provided with a response boost and is thereby prepared for the excavation phase. The response of the hydraulic system 14 can be increased by one or a combination of the following measures.

[0084] According to one example, the control system 44 commands an increase of a rotational speed of the second power source 42. As a consequence, the rotational speeds 58 of the hydraulic pumps 48a-48c will increase and the response of the hydraulic system 14 is increased. The performance of the wheel loader 10 is thereby increased. An increase of the rotational speed 58 of the hydraulic pumps 48a-48c is thus one measure for increasing the response of the hydraulic system 14.

[0085] As a further example, the control system 44 may change the filters 80a-80c for controlling the valve arrangements 54a-54c. Also in this way, the response of the hydraulic system 14 can be increased. A change of one or more of the filters 80a-80c can thus be used as a measure for increasing the response of the hydraulic system 14.

[0086] Increasing the response of the hydraulic system 14 will require some extra energy, but only when actually needed, instead of always in a conventional wheel loader. When the bucket 34 reaches the pile 88, the power output to the mechanical driveline 12 is increased as the pile 88 pushes back on the bucket 34. In the pile 88, the bucket 34 is lifted and tilted in. Due to the increased response, the power output to the hydraulic system 14 will be high immediately when the bucket 34 is lifted. The response of the hydraulic system 14 in the first lift is crucial for the drivability in the excavation phase.

[0087] After expiration of a certain time and/or upon determining that none of the triggers for the excavation mode 94 is active, the control system 44 can determine that the wheel loader 10 is again in the normal response mode 90. Upon determining that the wheel loader 10 is in the normal control mode, the control system 44 may control the response of the hydraulic system 14 to decrease to reduce energy consumption.

[0088] FIG. 5a is a schematic and illustrative diagram of the lifting lever signal 78a versus time. Here, the lifting actuator lever 76a is actuated at approximately 1.8 s.

[0089] FIG. 5b is a schematic and illustrative diagram of the speed of a hydraulic pump according to the prior art and the speed of the lifting hydraulic pump 48a of the invention as a function of the lifting lever signal 78a in FIG. 5a. In the prior art, the response is slow and the initial performance is consequently low. As shown in FIG. 5b it takes some time until the hydraulic pump according to the prior art is revved up after actuation of the lifting actuator lever 76a.

[0090] With the invention, the excavation phase is identified and it is thereby determined that the wheel loader 10 is in an increased response mode 96. As a result, the response of the hydraulic system 14 is increased and the lifting hydraulic pump 48a is revved up before the driver actuates the lifting actuator lever 76a. Due to the increased response, the lifting hydraulic pump 48a is revved up faster when the driver actuates the lifting actuator lever 76a- than in the prior art. As a result, the performance of the wheel loader 10 is improved. The timing and amount of revving up the hydraulic pumps 48a-48c when the entering the increased response mode 96 can be tuned depending on implementation.

[0091] FIG. 6 is a flowchart outlining the general steps of the method of controlling the wheel loader 10 according to the invention. The method comprises a step S1 of determining whether the wheel loader 10 is in an increased response mode 96. The method further comprises a step S2 of increasing the response of the hydraulic system 14 upon determining that the wheel loader 10 is in the increased response mode 96. The method further comprises a step S3 of determining whether the wheel loader 10 remains in the increased response mode 96. Upon determining in step S3 that the wheel loader 10 remains in the increased response mode 96, the increased response of the hydraulic system 14 is maintained. Upon determining that the wheel loader 10 is no longer in the increased response mode 96, the method proceeds to a step S4. In step S4, the response of the hydraulic system 14 is decreased. In a step S5, the method ends. In case it is determined in step S1 that the wheel loader 10 is not in the increased response mode 96, the method proceeds to step S5.

[0092] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.