Method for determining a compensated angle

Abstract

The invention relates to a method for determining a compensated angle (αcomp) of a component (2) of a work machine which can be pivoted relative to a reference component (4) between a first and a second end position, wherein there is a known end position angle difference between the first and the second end position, wherein an angle sensor (8) is provided which is coupled to the component (2) and the reference component (4) and which is designed to measure sensor angle values ​​of the component relative to the reference component.The method comprises a calibration phase, including pivoting (110, 16) of the component (2) into the first end position and detecting a first sensor angle value (αSens(αmin)) in the first end position, pivoting (120, 18) of the component (2) into the second end position and detecting a second sensor angle value (αSens(αmin)) in the second end position, and determining (130) a hysteresis angle value from the sensor angle difference between the first and the second sensor angle value and from the end position angle difference, and an application phase, including detecting (140) a sensor angle value for a determination time, determining (150) whether a positive or a negative pivot direction of the component is present at the determination time, and determining (160) the compensated angle (αcomp) by correcting the sensor angle value at the determination time by a value dependent on the hysteresis angle value and Angle correction depending on the swivel direction.

Description

[0001] The present invention relates to a method for determining a compensated angle, a computing unit and a computer program for carrying out the method, and a working machine. Background of the invention

[0002] In mobile work machines, e.g. an excavator, a wheel loader, a telehandler or a crane, it is often of interest to determine the position of an element (e.g. the upper carriage of an excavator relative to a world coordinate system) or the position of individual joints (e.g. boom, stick, bucket joints). Knowledge of these quantities is useful, for example, to give the operator precise feedback on the position of the work tool or to implement control or regulation algorithms, e.g. for work space limitation or coordinate control. To determine the position of an element, methods can be used, for example, for stroke measurement (e.g. magnetostrictive) on a cylinder, for joint angle measurement (e.g. using a potentiometer or an optical or magnetic encoder) or using inertial sensors. Disclosure of the invention

[0003] According to the invention, a method for determining a compensated angle, a computing unit and a computer program for implementing the method, and a work machine having the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the subclaims and the following description.

[0004] The invention uses the measure of determining, by means of a calibration phase and an application phase, a compensated angle of a component of a work machine that can be pivoted relative to a reference component between a first and a second end position, wherein sensor angle values ​​are measured or recorded with an angle sensor that is coupled to the component and the reference component. In the calibration phase, the component is pivoted successively into the first and second end positions, and corresponding sensor angle values ​​are recorded, from which a hysteresis angle value is determined. In the application phase, a sensor angle value and a pivot direction are recorded or determined for a determination time, and the compensated angle is determined by correcting the sensor angle value by an angle correction that depends on the hysteresis angle value and the pivot direction. By the procedure according to the invention, ieIn particular, by considering the hysteresis angle value and the swivel direction during angle correction, consistent values ​​for the compensated angle can be determined, which compensate for errors caused by play in the mechanical coupling of the angle sensor to the component and the reference component. In particular, the compensated angle is independent of the swivel direction.

[0005] According to one embodiment, with a positive pivot direction, a first fraction of the hysteresis angle value is added to the sensor angle value at the determination time, and with a negative pivot direction, a second fraction of the hysteresis angle value is subtracted from the sensor angle value at the determination time. In particular, the sum of the first and second fractions of the hysteresis angle value is equal to the hysteresis angle value. The first and second fractions of the hysteresis angle value can be equal to half the hysteresis angle value. According to this embodiment, the compensated angle lies within a band determined by the hysteresis, e.g., in its center.

[0006] According to one embodiment, the pivot direction is determined based on sensor angle values ​​at successive points in time. The pivot direction is determined as positive if the sensor angle values ​​increase between successive points in time and as negative if the sensor angle values ​​decrease between successive points in time. If the sensor angle values ​​change towards larger angles, a positive pivot direction is assumed. If the sensor angle values ​​change towards smaller angles, a negative pivot direction is assumed. This embodiment is easy to implement because it is based on existing variables (sensor angle values).

[0007] According to one embodiment, the pivot direction is determined based on measurements by a sensor different from the angle sensor, in particular an inertial sensor. This is expedient because this method is independent of measurements from the angle sensor; in particular, measurement errors do not affect both the sensor angle and the pivot direction.

[0008] According to one embodiment, the steps of the deployment phase are repeated without performing the calibration phase in between. This repeated execution of the steps of the deployment phase can, in particular, be carried out continuously, so that each time newly available sensor angle values ​​are compensated.

[0009] According to one embodiment, the calibration phase is performed again to update the hysteresis angle value. In particular, the calibration phase is performed again at at least one specific point in time and / or in response to at least one specific event and / or in response to a corresponding input from an operator of the work machine. Possible changes in the hysteresis angle, for example due to wear, can thus be taken into account.

[0010] A computing unit according to the invention, e.g. a control unit of a mobile work machine, is set up, in particular in terms of programming, to carry out a method according to the invention.

[0011] A work machine according to the invention has a component that can be pivoted relative to a reference component between a first and a second end position, wherein a known end position angle difference exists between the first and the second end position, wherein an angle sensor is provided which is (mechanically) coupled to the component and the reference component and which is configured to measure sensor angles of the component relative to the reference component. The work machine further has a computing unit according to the invention. The (mechanical) coupling can have a play that leads to a hysteresis in the measured sensor angle values. This hysteresis is taken into account by the method according to the invention in order to achieve consistent angle determination.

[0012] According to one embodiment, the angle sensor comprises a detection element fixedly mounted on the reference component and an arm element rotatably mounted on the reference component and engaging a follower element fixedly mounted on the component. Play may be present between the arm element and the follower element.

[0013] Implementing a method according to the invention in the form of a computer program or computer program product with program code for performing all method steps is also advantageous, as this entails particularly low costs, particularly if an executing control unit is also used for other tasks and is therefore already present. Suitable data storage devices for providing the computer program include, in particular, magnetic, optical, and electrical storage devices, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0014] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0015] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0016] The invention is illustrated schematically in the drawing using exemplary embodiments and is described in detail below with reference to the drawing. Character description

[0017] Figure 1 illustrates rotational movements of a component relative to a reference component and a corresponding angle measurement with an angle sensor. Figure 2 shows a flowchart according to an embodiment of the invention. Detailed description of the drawing

[0018] Figure 1illustrates rotary movements or swivel movements 16, 18 of a rotatable component 2 relative to a reference component 4 and an associated angle measurement with an angle sensor 8. The component 2 is attached to the reference component 4 by means of a rotary joint 6, so that the component 2 can swivel or rotate relative to the reference component 4. The component 2 can be, for example, a boom of an excavator, wherein the reference component 4 is the upper carriage of the excavator or is permanently attached to the upper carriage. The rotary movement or swivel movement of the component is brought about by an actuator, e.g. a hydraulic cylinder or similar (not shown). The angle measurement is intended to determine an angle of rotation about an axis of the rotary joint 6 of the (rotatable) component 2 relative to the reference component 4. The rotatable component 2 is also referred to simply as component 2.

[0019] Component 2 is between a first end position corresponding to a (actual) minimum angle a minute and a second end position corresponding to an (actual) maximum angle a max corresponds, rotatably movable (rotatable) or pivotable. The first end position is assumed, for example, when the hydraulic cylinder is retracted as far as possible and the second end position is assumed, for example, when the hydraulic cylinder is extended as far as possible. Since the kinematics or the geometry of the structure comprising component 2, reference component 4, swivel joint 6 and the actuator are known, the minimum angle a minute and the maximum angle a max known per se or, since the direction corresponding to the zero angle (ie the orientation of the corresponding coordinate system) can be determined arbitrarily, at least the actual angular difference a max - a minuteof these two angles. This angle difference is also called the end position angle difference.

[0020] An angle sensor 8 is provided, which has, for example, an element fixedly arranged on the reference component 4, referred to as a detection element, and an element rotatably arranged on the reference component 4, referred to as an arm element 10. The arm element 8 is rotatable, for example, about an axis that coincides with the axis of the pivot joint 6. Furthermore, the arm element 8 is engaged with an element fixedly arranged on the pivotable component 4, referred to as a follower element 12, so that the arm element 8 is rotated or followed by the component 2. The follower element 12 is, for example, a pin. The angle sensor 8 measures or detects an angle, referred to as a sensor angle. a Senseof the arm element 10 relative to the detection element. For example, the arm element 10, the detection element together with other elements of the angle sensor can form a potentiometer whose variable resistance corresponds to the angle value. The angle sensor is in particular designed to determine current sensor angle values ​​(i.e. current values ​​for the sensor angle) continuously or at certain time intervals that are regularly or irregularly spaced, for example on a time grid or with a certain measuring frequency. The angle sensor can further be designed to transmit measured or determined current sensor angle values ​​to an electronic control (computing unit), e.g. of the work machine, which has the pivotable component and the reference component (not shown).

[0021] There is a play between the arm element 10 and the follower element 12, which leads to a hysteresis in the angle measurement by the angle sensor 8. The resulting hysteresis curve is shown below in the Figure 1 shown in a diagram in which the sensor angle values a Sense against the actual angle a act More generally, there is a play caused by the mechanical coupling of the angle sensor 8 to component 2 and the reference component 4. This play can lead to hysteresis.

[0022] For example, a first pivoting movement 16 takes place in the direction of smaller angles (negative pivoting direction), ie clockwise in the figure, until the first end position or the actual minimum angle a minute is reached. In this case, a minimum angle measured by the angle sensor, ie a minimum sensor angle value a Sense ( a minute). During the first pivoting movement 16, the pin, ie the follower element 12, rests against a clockwise part of the fork-shaped end of the arm element 10.

[0023] After reversing the movement, a second pivoting movement 18 takes place in the direction of larger angles (positive pivoting direction), ie counterclockwise in the figure, until the second end position or the actual maximum angle a max is reached. After a transition phase, the pin, ie the follower element 12, rests against a counterclockwise part of the fork-shaped end of the arm element 10 during the second pivoting movement 18. This transition between the parts against which the follower element rests, ie this play, leads to the fact that immediately after the reversal of movement, the angle measured by the angle sensor 8, ie the sensor angle value, initially rests at the minimum sensor angle value a Sense ( a minute). The sensor angle value therefore initially remains unchanged, although a change in the actual angle a act When the actual maximum angle is reached a max a maximum angle measured by the angle sensor, ie a maximum sensor angle value a Sense ( a max ), reached.

[0024] If a subsequent movement in the direction of smaller angles occurs, i.e. clockwise, a phase occurs immediately after the reversal of movement due to the play in which the sensor angle value initially remains at the maximum sensor angle value α Sens (α max ), although the actual angle a act already reduced.

[0025] This hysteresis leads to the fact that a measured sensor angle value cannot be clearly assigned to the actual angle, or that the sensor angle value is an erroneous value for the actual angle. This problem is solved by the method according to the invention, in which a compensated angle a comp is determined.

[0026] Figure 2 shows a flowchart according to an embodiment of the invention, ie, a method for determining a compensated angle of a component of a work machine that is pivotable relative to a reference component between a first and a second end position. It is assumed that an angle sensor is provided that is configured to determine or measure sensor angle values. This corresponds to the Figure 1illustrated arrangement. The method can be implemented, for example, by an electronic controller (or computing unit) of the work machine by executing a corresponding computer program (angle compensation program). The electronic controller is also particularly configured to control an actuator that effects the relative pivoting movement of the component to the reference component (e.g., by executing a corresponding actuator control program). As explained above, the angle sensor transmits measured current sensor angle values ​​to the electronic controller. Compensated angles determined by the electronic controller using the method can be further used by the electronic controller for control tasks.

[0027] The procedure includes a calibration phase (steps 110 to 130) and a deployment phase (steps 140 to 160).

[0028] In step 110, the first end position is approached (by controlling the actuator accordingly), which corresponds, for example, to the actual minimum angle a minute This corresponds approximately to the first gift movement 16 in Figure 1 The corresponding sensor angle value determined by the angle sensor in the first end position is recorded and used as the first or minimum sensor angle value a Sense ( a minute ). The following then applies: α Sens α min = α min + α down .

[0029] The deviation of the first or minimum sensor angle value from the actual minimum angle is called the first offset angle a down The first offset angle, which is generally non-zero, is determined by the clearance, as explained. Furthermore, the offset angle can include a systematic deviation (particularly due to the determination of the zero angle).

[0030] Subsequently, in step 120, the second end position is approached (by appropriately controlling the actuator), which corresponds, for example, to the actual maximum angle a max (obviously, the opposite procedure could also be used, ie first the maximum angle is approached and then the minimum angle is approached). The corresponding sensor angle value determined by the angle sensor is recorded and used as the second or maximum sensor angle value a Sense ( a max ). The following then applies: α Sens α max = α max + α up .

[0031] The deviation of the minimum sensor angle value from the actual maximum angle is called the second offset angle a up The second offset angle, which is generally different from zero, is determined by the aforementioned clearance (and, if applicable, by the systematic deviation).

[0032] In step 130, a hysteresis angle value a hyst In particular, the hysteresis angle value a hyst as the difference (referred to as the sensor angle difference) between the first and second offset angles using the equations above: α hyst = α down − α up = α Sens α min − α min − α Sens α max − α max .

[0033] This can be rephrased to: α hyst = α Sens α min − α Sens α max − α min − α max .

[0034] In this equation for the hysteresis angle value a hyst The first term (sensor angle difference) can be determined from measured sensor angle values, and the second term (end position angle difference) is known from the kinematics of the components under consideration. The hysteresis angle value is determined accordingly as the sensor angle difference minus the end position angle difference. Any systematic deviation that may exist is eliminated from the second term due to the difference. The hysteresis angle value a hyst is used for angle compensation in the subsequent deployment phase.

[0035] In step 140, a sensor angle value a Sense ( tB) for a determination time tB recorded. An angle measurement value from the angle sensor is recorded. The determination time tB can be a current point in time, for example.

[0036] In step 150, a pivoting direction of the component at the determination time tB This determines whether the component rotates toward larger angles or toward smaller angles. Rotation toward larger angles is called the positive pivot direction. Rotation toward smaller angles is called the negative pivot direction.

[0037] The swivel direction can be determined, for example, by comparing successive sensor angle values ​​(measured by the angle sensor). a Sense ( tk ) at consecutive points in time tk where k is an integer and the time points are regularly spaced, for example ( tk +1 = tk + Δ t , with constant Δ t ). A positive pivot direction is then considered to exist if: α Sens t k > α Sens t k − 1 .

[0038] A negative swivel direction occurs when: α Sens t k < α Sens t k − 1 .

[0039] The determination time tB is in particular one of the successive points in time tk .

[0040] In addition to comparing consecutive sensor angle values, other methods are also conceivable for determining the swivel direction. Such as evaluating measured values ​​from one or more other sensors, such as inertial sensors. Control signals, such as those for the actuator, can also be evaluated for this purpose.

[0041] In step 160 the compensated angle a comp This involves a correction of the sensor angle value a Sense ( tB ) at the time of determination tB to correct the angle a corrwhich depends on the hysteresis angle value a hyst and the swivel direction S, so it applies a corr = a corr ( a hyst , S ), where S e.g. the values "pos" for the positive swivel direction and " negative " for the negative swivel direction. The angle correction is added to the sensor angle value: α comp t B = α Sens t B + α korr α hyst S .

[0042] In particular, it is intended to measure the sensor angle value a Sense ( tB ) at the time of determination tB to be corrected by half the hysteresis angle value for a positive swivel direction a hyst to the sensor angle value a Sense ( tB ) is added and for negative swivel direction half of the hysteresis angle value a hyst from the sensor angle value a Sense ( tB ) is subtracted to obtain the compensated angle a comp The compensated angle a comp then moves in the middle between the hysteresis branches, as in Figure 1 shown.

[0043] With this correction, where half the hysteresis angle value is added or subtracted, the following applies for a positive swivel direction: α comp t B = α Sens t B + α korr α hyst pos = α Sens t B + α hyst / 2 .

[0044] For negative swivel direction the following applies: α comp t B = α Sens t B + α korr α hyst neg = α Sens t B + α hyst / 2 .

[0045] More generally, a correction other than the addition / subtraction of half the hysteresis angle value can be selected. For example, still starting from a comp ( tB ) = α Sens ( tB ) + a corr ( a hyst , S ), the angle correction as a product of the hysteresis angle value a hyst and a factor depending on the swivel direction r ( S ) must be given: α korr α hyst S = r S ⋅ α hyst .

[0046] The factor r ( S ) with positive swivel direction equal to a constant g (ie r ( pos ) = g ) and for negative swivel direction equal to one minus the constant g (ie r ( negative ) = 1 -g ) . The constant g lies in particular between zero and one (ie g ∈ [0,1]). The constant g is a (first) fraction of the hysteresis angle value, which is added to the sensor angle value for positive swivel direction. One minus the constant g (ie 1 - g ) is a (second) fraction of the hysteresis angle value, which is subtracted from the sensor angle value in the case of a negative swivel direction.

[0047] The compensated angle a comp can be used to implement control functions of the working machine (e.g., in suitable control algorithms). Display or information functions, such as displaying angle information on a display of the working machine, can also be implemented to facilitate operation of the working machine.

[0048] Steps 140 to 160 of the deployment phase can be carried out repeatedly, in particular continuously, for different determination times, i.e., a jump is made from step 160 to step 140. The same hysteresis angle value can be used in each case, i.e., steps 140 to 160 of the deployment phase are repeated without performing a calibration phase between the repetitions.

[0049] Optionally, in step 170, a re-execution of the calibration phase can be triggered (i.e., a jump to step 110) to update the hysteresis angle value. Step 170 can be performed at specific times (e.g., regularly) and / or in response to specific events (e.g., start of the working machine) and / or in response to a corresponding input from an operator of the working machine. Redetermining the hysteresis angle value is useful because the play of the mechanical coupling of the angle sensor to the component and the reference component can change over time (e.g., due to wear) or even with temperature.

[0050] Furthermore, it may be provided to check whether the hysteresis angle value is above a predetermined maximum angle; such a check can be performed, for example, after step 130. If it is determined that the hysteresis angle value is above a predetermined maximum angle, an error message can be generated and output, for example, on a display of the working machine. Such an error message can also be transmitted to control algorithms that use the compensated angle (e.g., to implement automatic control functions), so that they implement only limited functionality in response.

Claims

1. Method for determining a compensated angle ( α comp ) a component (2) of a work machine which is pivotable relative to a reference component (4) between a first and a second end position, wherein there is a known end position angle difference between the first and the second end position, wherein an angle sensor (8) is provided which is coupled to the component (2) and the reference component (4) and which is designed to measure sensor angle values of the component relative to the reference component, comprising a calibration phase, including pivoting (110, 16) of the component (2) into the first end position and detecting a first sensor angle value ( α Sens ( α min )) in the first end position; pivoting (120, 18) the component (2) into the second end position and detecting a second sensor angle value ( α Sens ( α min )) in the second end position; determining (130) a hysteresis angle value from the sensor angle difference between the first and the second sensor angle value and from the end position angle difference; and an application phase, including detecting (140) a sensor angle value for a determination time; determining (150) whether a positive or a negative pivoting direction of the component is present at the determination time; and determining (160) the compensated angle ( α comp ) by correcting the sensor angle value at the time of determination by an angle correction depending on the hysteresis angle value and the swivel direction.

2. Method according to claim 1, wherein in the case of a positive swivel direction, a first fraction of the hysteresis angle value is added to the sensor angle value at the time of determination and in the case of a negative swivel direction, a second fraction of the hysteresis angle value is subtracted from the sensor angle value at the time of determination in order to obtain the compensated angle ( α comp ) (160).

3. The method of claim 2, wherein the sum of the first and second fractions of the hysteresis angle value is equal to the hysteresis angle value.

4. The method according to claim 2 or 3, wherein the first and second fractions of the hysteresis angle value are equal to half the hysteresis angle value.

5. Method according to one of the preceding claims, wherein the hysteresis angle value is determined as the sensor angle difference minus the end position angle difference.

6. The method according to any one of the preceding claims, wherein the pivot direction is determined (150) based on sensor angle values at successive times; wherein the pivot direction is determined as positive if the sensor angle values increase between successive times and as negative if the sensor angle values decrease between successive times.

7. Method according to one of the preceding claims, wherein the pivoting direction is determined (150) based on a measurement by a sensor different from the angle sensor (8), in particular an inertial sensor.

8. Method according to one of the preceding claims, wherein the steps of the deployment phase are carried out repeatedly without intermediate performance of the calibration phase.

9. Method according to one of the preceding claims, wherein the calibration phase is performed again to update the hysteresis angle value; wherein, in particular, the calibration phase is performed again at at least one specific time and / or in response to at least one specific event and / or in response to a corresponding input from an operator of the work machine.

10. A computing unit comprising a processor configured to carry out the method according to any one of the preceding claims.

11. A work machine comprising a component (2) pivotable relative to a reference component (4) between a first and a second end position, wherein a known end position angle difference exists between the first and the second end position, wherein an angle sensor (8) is provided which is coupled to the component (2) and the reference component (4) and which is configured to measure sensor angle values of the component relative to the reference component; further comprising a computing unit according to claim 10.

12. Work machine according to claim 11, wherein the angle sensor (8) has a detection element fixedly arranged on the reference component (4) and an arm element (10) which is rotatably mounted on the reference component and engages with a carrier element (12) fixedly arranged on the component (2).

13. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to claims 1 to 9.

14. A computer-readable data carrier on which the computer program according to claim 13 is stored.

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