METHOD FOR DETERMINING A PHYSICAL PARAMETER OF AN UPPER LINK

Abstract

A method for determining a physical parameter of an adjustable upper link of a three-point hitch during a working operation thereof includes providing a lower link of the three-point hitch and an implement attachable to the upper and lower links of the three-point hitch. The method includes generating calibration data prior to the working operation of the three-point hitch, where the calibration data defines a relationship of a length of the upper link to an upper link angle defined between the upper link and a reference line. Moreover, the calibration data is used to determine a physical parameter of the adjustable upper link during the working operation.

Claims

1. A method for determining a physical parameter of an adjustable upper link of a three-point hitch during a working operation thereof, comprising: providing a lower link of the three-point hitch and an implement attachable to the upper and lower links of the three-point hitch; generating calibration data prior to the working operation of the three-point hitch, where the calibration data defines a relationship of a length of the upper link to an upper link angle defined between the upper link and a reference line; and using the calibration data to determine a physical parameter of the adjustable upper link during the working operation.

2. The method of claim 1, further comprising: detecting a current angle of the upper link during the working operation; and determining the current upper link length of the upper link as the physical parameter.

3. The method of claim 1, further comprising: detecting a current length of the upper link during the working operation; and determining a current upper link angle of the upper link as the physical parameter.

4. The method of claim 1, wherein the generating step comprises generating the calibration data based on an articulation position of the lower link for connecting a lifting strut.

5. The method of claim 1, wherein the generating step comprises generating the calibration data based on a connecting position on the supporting structure of the vehicle for connecting the upper link.

6. The method of claim 1, wherein the generating step comprises generating the calibration data based on an adjustable length of the lifting strut.

7. The method of claim 1, wherein the generating step comprises generating the calibration data based on a mast height (of the implement.

8. The method of claim 1, wherein the generating step comprises generating the calibration data based on a lifting position of the lower link.

9. The method of claim 5, wherein the calibration data is generated for different lifting positions of the lower link.

10. The method of claim 1, further comprising: defining a working range for the lower link delimited by a lifting position and a further lifting position; and suppressing the determination of the physical parameter of the upper link for a lifting position of the lower link outside the working range.

11. The method of claim 1, further comprising varying the upper link length between a minimum upper link length and a maximum upper link length in order to generate calibration data in a lifting position of the lower link with attached implement.

12. The method according to claim 11, wherein the varying step comprises: varying the upper link length first in the direction of the minimum upper link length or of the maximum upper link length; and varying the upper link length thereafter in the opposite direction.

13. The method of claim 11, further comprising detecting the upper link angle during a length variation of the upper link.

14. The method of claim 1, wherein the calibration data is generated as a component of a characteristic curve.

15. The method of claim 1, further comprising determining the upper link length as a function of a change of the upper link angle over time.

16. The method of claim 1, further comprising determining the upper link length as a function of an adjusting direction of the upper link length.

17. A method for determining a physical parameter of an adjustable upper link of a three-point hitch during a working operation thereof, comprising: providing a lower link of the three-point hitch and an implement attachable to the upper and lower links of the three-point hitch; detecting a current angle of the upper link during the working operation; generating calibration data prior to the working operation of the three-point hitch, where the calibration data defines a relationship of a length of the upper link to an upper link angle defined between the upper link and a reference line; using the calibration data to determine a physical parameter of the adjustable upper link during the working operation; and determining the current upper link length of the upper link as the physical parameter.

18. The method of claim 17, further comprising detecting a current length of the upper link during the working operation.

19. A method for determining a physical parameter of an adjustable upper link of a three-point hitch during a working operation thereof, comprising: providing a lower link of the three-point hitch and an implement attachable to the upper and lower links of the three-point hitch; detecting a current length of the upper link during the working operation; generating calibration data prior to the working operation of the three-point hitch, where the calibration data defines a relationship of a length of the upper link to an upper link angle defined between the upper link and a reference line; using the calibration data to determine a physical parameter of the adjustable upper link during the working operation; and determining a current upper link angle of the upper link as the physical parameter.

20. The method of claim 19, further comprising detecting a current angle of the upper link during the working operation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein:

[0031] FIG. 1 is a side view of a three-point hitch with a lower link in a first lifting position,

[0032] FIG. 2 is a side view of a three-point hitch according to FIG. 1 with the lower link in a different lifting position,

[0033] FIG. 3 is a diagram with calibration data as characteristic curves that represent an upper link angle in relation to an upper link length, and

[0034] FIG. 4 is a block diagram with a schematically illustrated interaction of components for determining a physical parameter of an upper link.

[0035] Corresponding reference numerals are used to indicate corresponding parts throughout the several views.

DETAILED DESCRIPTION

[0036] The embodiments of the present disclosure described below are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present disclosure.

[0037] FIG. 1 shows an agricultural vehicle 10, more particularly a tractor, having a supporting structure 12 (e.g., frame chassis, etc.) shown partially and schematically. A three-point hitch 14, shown schematically and not true to scale, is mounted on the supporting structure 12. A planar kinematics of the three-point hitch 14 spans a plane, which is designated as an x-z plane with reference to FIGS. 1 and 2. The x-direction here corresponds to a vehicle longitudinal direction or vehicle horizontal line 16, while the z-direction corresponds to a vehicle vertical direction or a vehicle vertical line 17. A y-direction arranged perpendicular to the x-direction and the z-direction corresponds to a vehicle transverse direction. A schematically shown implement 18 is mounted on the vehicle 10 by means of a three-point hitch 14.

[0038] The three-point hitch 14 includes an upper link 20 that is articulated to the supporting structure 12 of the tractor 10 via a connecting point 22. The connecting point 22 enables three different connecting positions for the upper link 20 along the vehicle vertical direction 17, wherein the connecting position 22-1 is used in the example.

[0039] The three-point hitch 14 further includes two lower links 24 at a distance from one another in the y-direction or transverse direction of the vehicle 10. Each lower link 24 is articulated via a bearing 26 to the support structure 12. The lower link 24 includes two different articulation positions 28-1 and 28-2 for selective connection of a lifting strut 30. In the illustrated embodiment, the lifting strut 30 is connected at the articulation point 28-2. The lower link 24 is articulated via the lifting strut 30 to one end of a lifting arm 32, which is connected at its other end via a connection point 34 to the support structure 12 of the vehicle 10. The lifting arm 32 can be pivoted relative to the support structure 12 via a hydraulic cylinder 38, which engages with a lifting arm joint 36 and is supported against the support structure 12. With an appropriate actuation of the hydraulic cylinder 38, the lifting arm 32 is pivoted such that the pivoting movements thereof are transmitted via the lifting strut 30 to the lower link 24. In this manner, the lower link 24 is pivoted, for example, from a first lifting position at an angle .sub.1 relative to the vehicle horizontal line 16 (FIG. 1) into a further lifting position at an angle .sub.5 relative to the vehicle horizontal line 16 (FIG. 2). The length of the lifting strut 30 is constant. In another embodiment, the length of the lifting strut 30 is adjustable (e.g., as a lifting spindle) so that angular positions of the lifting arm 32 and the lower link 24 can be adjusted relative to one another.

[0040] The upper link 20 and the lower link 24 are connected via a coupling point 40 or a coupling point 42 to the implement 18. The upper link 20 is adjustable relative to the upper link length L thereof between a minimum length L_min and a maximum link L_max. For this purpose, the upper link 20 is designed, for example, as a hydraulic upper link having a piston-cylinder unit. At a constant lifting position, e.g., with the angle .sub.1 or .sub.5, of the lower link 24 and a constant mast height M between the coupling point 40 and the coupling point 42, the coupling point 40 is moved along a circular path Kr with the mast height M as the radius when the upper link length L is adjusted. An upper link angle between the upper link 20 and the vehicle horizontal line 16 as the reference line is varied in this case.

[0041] According to the method, calibration data is provided for determining the upper link length L or the upper link angle of the upper link 20 during working operation of the three-point hitch 14. According to FIG. 3, the calibration data is provided for the sake of example in the form of different characteristic curves K1, K2, K3, K4, K5. A different lower link angle is associated with each characteristic curve K. For example, the characteristic curve K1 is associated with the lower link angle .sub.1, and the characteristic curve K2 is associated with the lower link angle .sub.2, etc. The characteristic curves K are components of a diagram which presents a relationship between the upper link length L and the upper link angle depending on different adjusted lifting positions of the lower link 24 (i.e., different lower link angles ). Thereby a simple conversion between the upper link length L and the upper link angle during the working operation is possible if the three-point hitch 14 is adjusted in a defined manner.

[0042] The upper link length L and the upper link angle of the upper link 20 are to be determined in a cost-effective manner during working deployment, dispensing with typical sensor means on the vehicle 10 for detecting different physical parameters or features.

[0043] In one embodiment, suitable sensor means (e.g., inertial or inclination sensors) are provided on the upper link 20 in order to detect the upper link angle . In this embodiment, the upper link angle is detected by sensor means at an adjusted lifting position of the lower link 24 and the upper link length L is determined as a physical parameter. A cost-intensive and elaborate instrumentation or retrofitting on the vehicle 10 or the three-point hitch 14 for detecting the upper link length L can thus be avoided. In another embodiment, the upper link length L is first detected by sensor means in order to determine the upper link angle as a physical parameter by means of the provided calibration data for an adjusted lifting position of the lower link 24. In this case, a detection of the upper link angle by sensor means is superfluous.

[0044] The calibration data is generated by means of a calibration process. In other words, the diagram according to FIG. 3 is calibrated for a specific geometry of the three-point hitch 14. The implement 18 is attached to the three-point hitch 14 to be calibrated. During the calibration, the lower link 24 is adjusted in at least two different lifting positions of the three-point hitch 14, e.g., in a first lifting position with the lower link angle .sub.1 according to FIG. 1 and in a further lifting position with the lower link angle .sub.5 according to FIG. 2. In each adjusted lifting position, the upper link 20 is moved or adjusted between the two end positions thereof, i.e., between the minimum upper link length L_min and the maximum upper link length L_max. The movement of the upper link 20 is presumed to be known, e.g., a continuous movement with constant adjusting speed or with a non-constant adjusting speed known by empirical tests. In order to compensate for any deviations from the presumed movement of the upper link 20, the upper link 20 is adjusted in both directions.

[0045] Beginning from the start of the calibration, a current upper link length L_akt can be recorded at every point in time without having to be measured. During the recorded variation of the upper link length L, the respective value of the current upper link angle _akt is detected for each current upper link length L_akt, by means of sensor equipment, for example. From the value pairs of the current upper link length L_akt and the current upper link angle _akt recorded at a defined lifting position of the lower link 24, a characteristic curve (e.g., characteristic curve K5) can be created and stored.

[0046] As already explained, the individual characteristic curves K each correspond to an adjusted lifting position or working position of the lower link 24, i.e., an adjusted lower link angle . Individual characteristic curves K are thus generated on the basis of a respective lifting position of the lower link 24. For the characteristic diagram according to FIG. 3, the characteristic curve K1 is first generated at a minimum lifting position of the lower link 24 and the characteristic curve K5 is generated at a maximum lifting position of the lower link 24. The three-point hitch 14 is initially adjusted for this purpose to the lifting position with the lower link angle .sub.1. In addition, the upper link 20 is moved into the end position thereof with the minimum upper link length L_min. This is a starting position P1 for the calibration. Then the upper link 20 is extended to the maximal upper link length L_max (position P2) and then again retracted completely (position P3). As already explained, the upper link angle is recorded during this displacement of the upper link 20. Thus, the characteristic curve K1 is generated and recorded. Subsequently the three-point hitch 14 is adjusted to the maximum lifting position of the lower link 24 with the lower link angle .sub.5 (position P4). The upper link 20 is again completely extended (position P5) and then completely retracted (position P6). Thus, the characteristic curve K5 is also generated and recorded. Additional characteristic curves K lying between characteristic curves K1 and K5 (e.g., characteristic curves K2, K3, K4) can be generated analogously in order to produce the characteristic diagram according to FIG. 3. Alternatively, arbitrarily many characteristic curves between K1 and K5 can be generated by interpolation.

[0047] After generating the characteristic curves for specific lifting positions of the lower link 24, the calibration is complete. The three-point hitch 14 and the upper link 20 can now be adjusted to a working position in order to begin working operation. In this case, the three-point hitch 14 or the lower link 24 is lowered into a position P7, for example, and the upper link 20 is extended along with the upper link coupling point 40 into a position P8.

[0048] For the sake of completeness, it should be mentioned that the calibration or characteristic diagram explained according to FIG. 3 is applicable to a specific adjustment of the three-point hitch 14, and a corresponding different characteristic diagram must be generated for a different specific adjustment. These specific adjustments relate in particular to the adjusted connecting position at the connecting point 22, the adjusted length of the lifting strut 30, the adjusted articulation position 28 at the lower link 24 and any different possible coupling point 40, 42 on the implement 18, with correspondingly different mast heights M.

[0049] The lifting positions with the lower link angles .sub.1 and .sub.5 can be considered the lower and upper limits of a defined working range of the three-point hitch 14. In this disclosure, the determination of a physical parameter is suppressed outside this working range. In particular, a determination of the upper link length L is suppressed, whereas the upper link angle continues to be detected and recorded in order to enable determination of the upper link length L again as soon as the three-point hitch 14 is again operating within the defined working range.

[0050] It can be seen from the diagram according to FIG. 3 that for certain lifting positions of the lower link 24, namely for characteristic curves K1 to K4, an upper link angle determined by sensor means cannot unambiguously be associated with an upper link length L, so that the length thereof cannot be unambiguously determined directly. On the contrary, two different positions of the three-point hitch 14 are initially possible which is expressed, for example, by the two different values L_A and L_B for the upper link length L on either side of the inflection point L_s in characteristic curve K1. Therefore, a distinction of cases is carried out during working operation in order to determine whether the sought value of the upper link length L is in the range A to the left of the inflection point L_s or in the range B to the right of the inflection point L_s. To distinguish the cases, it is possible to record a variation over time of the upper link angle and a displacement direction of the upper link 20 (from a greater length L to a smaller length L or vice versa). Taking into account the end positions L_min and L_max of the upper link 20, it is possible to decide whether the upper link length L of the upper link 20 is in the range A or in the range B.

[0051] The diagram or characteristic diagram according to FIG. 3 can alternatively be used proceeding from an upper link length L determined by sensor means in order to determine the upper link angle . In contrast to a determination of the upper link length L, a distinction of cases is superfluous in this case, because the determination of the upper link angle based on the detected upper link length L is unambiguous.

[0052] In order to perform the method for determining a current upper link length L_akt or a current upper link angle , at least one control device 44 for acquiring and processing sensor data is arranged on the vehicle 10 (FIG. 4). This control device 44 (or a further control device communicating therewith) is used for controlling the three-point hitch 14 for adjusting or changing the position thereof and for controlling a hydraulic control valve 46 actuating the upper link 20 to change the upper link length L. A memory unit 48 connected to the control device 44 is also provided in order to store the generated calibration data or characteristic curves K. An operating interface 50 on the vehicle 10 is used for starting the calibration process and for manually actuating the three-point hitch 14 and the upper link 20. By means of a characteristic curve K in the memory unit 48 and a current upper link angle _akt detected by sensor means, the control device 44 can determine the associated current upper link length L_akt. Conversely, the control device 44 can also determine the current upper link angle _akt associated with an upper link length L_akt detected by a sensor. The control device 44 in an embodiment is programmed such that the upper link 20 is controlled based on a specific input parameter. In particular, the control valve 46 is controlled by the control device 44 in such a manner that a target parameter in the form of a target upper link length L_soll or a target upper link angle _soll is regulated. The current upper link length L_akt determined on the basis of the stored calibration characteristic diagram or the current upper link angle L_akt [sic; _akt] determined by means of this calibration characteristic diagram is used as the feedback for the regulation.

[0053] While exemplary embodiments incorporating the principles of the present disclosure have been disclosed hereinabove, the present disclosure is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.