Method and system for weighing a load

Abstract

The invention relates to a method for weighing a load for a crane (12) that uses a scale (10), wherein the crane (12) includes a boom (14), an implement (16) for gripping the load, a scale (10) for weighing the load, and a flexible line (20) for conveying an operating force from the boom (14) to the implement (16), and in the method the scale (10) is tuned at least once prior to use of the scale (10) in different tuning orientations of the crane (12) in order to form a correction function that compensates a systematic error that depends on the angle between the boom (14) and the implement (16) as a function of the orientation of the crane (12), a weighing result is measured with the scale (10) by weighing the load, and the weighing result of the scale (10) is automatically corrected as a function of orientation using software means (22) and by means of the correction function by determining a quantity that correlates with the angle between the boom (14) and the implement (16) during weighing. The invention also relates to a system for weighing a load.

Description

[0001] METHOD AND SYSTEM FOR WEIGHING A LOAD

[0002] The invention relates to a method for weighing a load for a crane that uses a scale, wherein the crane includes a boom, an implement for gripping the load, and a flexible line between the boom and the implement for conveying an operating force to the implement .

[0003] The invention also relates to a system for weighing a load.

[0004] Cranes such as, for example, articulating boom cranes use a scale to weigh loads lifted by the implement attached to the crane. Almost invariably, the operating force for the implement is conducted from a base machine, for example from a forest machine or a truck, via the crane by means of flexible lines such as, for example, hydraulic hoses. When the crane is operated in different orientations to lift a load, the flexible line is subjected to different stresses, as its points of attachment to the implement and crane are fixed. As the scale is located between the crane and the implement, the tension caused by the stiffness of the flexible lines causes a lifting or downward pulling force on the implement, which causes a systematic weighing error.

[0005] When the scale is fared, the weight of the empty implement is set to zero and, at the same time, the force of the flexible lines affecting the weighing is set to zero. When the crane is operated by moving the tip inwards and outwards, the orientation of the boom relative to the scale changes, whereby the distance between the points of attachment of the flexible lines running from the tip of the crane to the implement changes. When the tip of the crane is moved inwards, this distance increases, whereby the lifting force of the hoses increases and the scale starts to register negative kilograms, i.e. the weight registered is too low. When, on the other hand, the tip is moved outwards, the distance between the points of attachment begins to decrease, whereby the flexible line presses downwards and the scale begins to register too many kilograms. As a result, the scale is subject to a systematic error that depends on the height at which the unloading of a load in a stack or pile is carried out.

[0006] Established requirements pertaining to the measurement of timber stipulate that a measurement cannot contain any systematic errors, even if the measurement error is within acceptance limits.

[0007] The publication US 2008319710 Al, which discloses a method for estimating the weight of an excavator payload, is known in the prior art. This method does not use a scale but rather estimates the weight of the load from the pressures in the cylinders of the boom of the excavator. It is not possible with this estimation, however, to attain an accuracy that is sufficient for the measurement of timber. The poor accuracy is due to inaccuracies in the measurement of the cylinder pressures, which inaccuracies are caused by the friction in the cylinders, which increases with pressure, as well as by the friction in the articulated joints of the booms of the crane.

[0008] The object of the invention is to provide a method and a system for weighing a load lifted by a crane that take into account a systematic error caused by flexible lines. The characteristic features of a method according to the invention are set out in the attached patent claim 1, while the characteristic features of a system according to the invention are set out in the attached patent claim 10.

[0009] The object of a method according to the invention is achieved by a method for weighing a load for a crane that uses a scale, wherein the crane includes a boom, an implement for gripping the load, a scale, and a flexible line between the boom and the implement for conveying an operating force to the implement, and wherein the method includes the steps of tuning the scale at least once prior to use of the scale in different tuning orientations of the crane in order to form a correction function that compensates a systematic error that depends on the angle between the boom and the implement as a function of the orientation of the crane, and automatically correcting the weighing result of the scale as a function of orientation using software means and by means of the correction function by determining a quantity that correlates with the angle between the boom and the implement during weighing.

[0010] In the method according to the invention, the force caused by the angle between the boom and the implement, which biases the weighing result of the scale, is taken into account by means of a correction function which compensates or at least minimizes the biasing force in all operating orientations of the crane. The weighing result is thus more accurate than with methods according to the prior art, as the systematic error can be eliminated or at least minimized.

[0011] In this context, the angle between the boom and the implement refers to the angle between the longitudinal axis of the boom and an imaginary line that runs through the implement to the end of the boom.

[0012] More specifically, the angle between the boom and the implement is unique in each tuning orientation. It is thus possible to ascertain the systematic error caused by the orientation of the implement in each tuning orientation, which enables a calculation between tuning orientations. Preferably, the scale includes a sensor for measuring the force acting on the same between the parts of the crane that are attached to the scale. By means of forces measured directly between the parts of the crane, the weight of the load can be determined reliably and accurately, as opposed to estimates in which an indirect measurement, for example of the friction in the cylinders, reduces the accuracy of the weight estimate and makes it more complicated.

[0013] It is understood here that the term "scale" refers to a measuring device with which the weight of a load can be measured directly without indirect inference or calculation.

[0014] Preferably, the scale is a separate physical unit arranged between the second end of the boom and the implement. In other words, the scale joins the boom and the implement to each other .

[0015] Preferably, the crane used in the method is a timber crane, and the load to be weighed is a tree or trees. Especially in this kind of operating environment, a sufficient accuracy in the weighing of a load and the elimination of any systematic weighing errors are required in order for a weighing to meet the general requirements governing the weighing of timber.

[0016] Preferably, the boom includes two ends, wherein the first end is closer to the point of attachment of the crane to the work machine when the crane is fully extended and the second end lies opposite the first end, and the scale is arranged between the end of the boom and the implement. In this kind of case especially, the flexible line causes an error in the scale.

[0017] Preferably, the quantity that correlates with the angle between the boom and the implement is the angle between the boom and the implement. Alternatively, the correlated quantity can be, for example, the position of the end of the boom or of the implement relative to the point of articulation of the crane on the work machine.

[0018] Preferably, in the method, the implement is moved by means of the crane to the load to be lifted for the lifting and weighing of the load. This movement causes a change in the angle between the boom and the implement, whereby the angle-dependent error changes .

[0019] Preferably, when the implement is moved by means of the crane, the angle between the longitudinal axis of the boom and the line formed between the end of the boom and the implement changes. This produces a change in the distance between the points of attachment of the flexible lines, which in turn causes a weighing error.

[0020] Preferably, in the method, the implement is moved to the load to be lifted by means of the crane, the load is lifted by means of the crane, and the load is weighed by means of the scale. The weighing error caused by the flexible lines occurs when the angle between the boom of the crane and the scale changes.

[0021] Preferably, the tuning of the scale is carried out at least once prior to the use of the scale by determining a systematic error in at least two tuning orientations of the crane that differ with regard to the angle between the boom and the implement and by forming a correction function that compensates the systematic error as a function of the orientation of the crane based on this determination. It is thus possible to form a correction function for all operating orientations of the crane, so that the systematic error can be eliminated or at least minimized in all operating situations. More specifically, the tuning of the scale is carried out in the following steps, wherein a zero position of the crane in which the error of the scale is essentially zero is determined by means of a sensor or sensors that determine the quantity that correlates with the angle between the boom and the implement, the systematic error in the measurement of the scale is determined in at least two different tuning orientations of the crane, the quantity that correlates with the angle between the boom and the implement is determined in the tuning orientations using the sensor or sensors, and a correction function is formed that compensates the systematic error as a function of orientation.

[0022] Said tuning orientations can be different from the zero position, although alternatively the zero position can be one of the tuning orientations.

[0023] A tuning orientation refers here to an orientation in which the quantity that correlates with the angle between the boom and the implement is determined using a sensor or sensors. Each tuning orientation has a unique angle between the boom and the implement .

[0024] In other words, the distance between the fixed points formed on the boom and on the implement by the flexible line changes in different tuning orientations, which changes the systematic error caused by the flexible line in the measurement result of the scale.

[0025] According to a first embodiment, the error is determined using a known load in different tuning orientations. According to a second embodiment, an error-free orientation of the scale is determined by taring the scale, so that in that orientation the error is eliminated.

[0026] Preferably, the tuning is performed automatically. An automatic tuning speeds up the implementation of the method and eliminates the possibility of systematic human errors that can be caused by actions of a user.

[0027] Alternatively, the tuning can be performed manually in steps carried out by the user. In this case, separate instructions for performing the tuning correctly are preferably provided to the user.

[0028] Preferably, the orientation of the scale and of the boom relative to each other is the angle between them. The angle can be a two- or three-dimensional angle, since preferably the link located between the scale and the boom of the crane includes two articulated joints that are perpendicular to each other, which render possible an angle in two different directions. In other words, two angles or an angle and its direction can be included in the measurement.

[0029] Preferably, a link including two articulated joints that are perpendicular to each other is provided between the end of the boom and the implement, and in the method the tuning of the scale is carried out with respect to both articulated joints in order to form the correction function, and this correction function is used to compensate the weighing result. This allows the angle between the scale and the crane to be taken into account in both directions.

[0030] According to one embodiment, the crane includes an additional sensor for determining an additional quantity, and in the method the effect of the additional quantity on the measurement result of the scale is determined and the correction function is formed, which takes into account the effect of the additional quantity so as to compensate the additional quantity, wherein the additional quantity is, for example, one or more of the following: a rotational torque of the link, a temperature, a pressure of a hydraulic fluid when the flexible line is a hydraulic hose. Temperature is known to affect the stiffness of flexible lines, as is hydraulic pressure, which also causes forces that act on the lines. A rotational torque is also known to have at least some effect on weighing. In addition to those mentioned, there can be other variables that affect measurement.

[0031] It can be established by means of the sensor system whether the rotational torque is wrong due to circumstances, and this effect can be compensated in the weighing result.

[0032] According to one embodiment, the scale is tuned in at least two different tuning orientations of the crane, preferably in 3-20 different tuning orientations of the crane, and the correction function is fitted to the respective tuning orientations. By limiting the number of tuning orientations, it is possible to minimize the duration and data amount of the tuning step while simultaneously obtaining a very accurate estimate for the correction function in all operating orientations of the crane.

[0033] Alternatively, the tuning can be performed as a continuous movement between tuning orientations, in which case there can be hundreds or even thousands of tuning-orientation points. According to one embodiment, the correction function can be fitted by interpolation, extrapolation, or a combination of the two .

[0034] According to one embodiment, in the method, when the additional quantity is temperature, the temperature is determined and a tuning of the scale is carried out again when the temperature changes by more than 5 °C, preferably by more than 10 °C, relative to the previous tuning. A change in temperature can change the stiffness of the flexible lines, which can affect the measurement result.

[0035] The object of a system according to the invention is achieved by a system for weighing a load, wherein the system includes a crane that includes a boom, an implement for gripping the load, a scale connected to the boom for weighing the load, and a flexible line between the boom and the implement for conveying an operating force to the implement. The system further includes a sensor for determining a quantity that correlates with the angle between the boom and the implement, software means for processing measurement data of the scale and memory for the software means, as well as a tuning load for the scale. The software means in the system is configured to determine, in different tuning orientations of the crane, a correction function that compensates a systematic error that depends on the angle between the boom and the implement as a function of the orientation of the crane, to store the correction function in the memory, and to automatically correct the weighing result of the scale during lifting as a function of orientation by means of the correction function by determining the quantity that correlates with the angle between the boom and the implement by means of the sensor. The system according to the invention can be entirely or partially implemented using technology that already exists in connection with cranes as a programmable part of the system. The implementation of the system is thus readily adaptable to already existing systems.

[0036] In this context, a crane can also be called a loader.

[0037] In this context, the term scale should be interpreted in the sense that it can be integrated into the tip of the boom, into the link, the rotation device, the crane or the implement, or means for fastening the same, or the scale can be a separate component somewhere between the aforementioned parts.

[0038] Preferably, the scale is a deformation-measuring scale located between the implement and the end of the boom. This is generally the kind of scale used in connection with forest machines, for which a high weighing accuracy is required.

[0039] Preferably, the scale includes strain gauge sensors for determining the force caused by the load and the weight of the load. Strain gauge sensors provide a good measurement accuracy for the scale.

[0040] Preferably, the sensor is an orientation sensor of the boom for determining the orientation data of the boom, and the system further includes a second sensor configured to be connected to the scale for determining the orientation data of the implement .

[0041] Alternatively, the sensor that determines the quantity that describes the angle between the boom and the implement can also be, for example, a combination of a plurality of sensors or simply a single position sensor of the implement more preferably sensors, or data processed by the sensors.

[0042] According to a preferred embodiment, the scale is a weighing link, preferably suspended between the end of the boom and the rotation device. The weighing link can be based on a measurement of the oil pressure in the link by a pressure sensor .

[0043] According to an alternative embodiment, the scale is a suspended scale, which can be located, for example, between the rotation device and the implement.

[0044] Preferably, the crane is an articulating boom crane including at least two booms that are attached to each other in an articulated manner.

[0045] In a preferred embodiment, the crane includes a pillar boom, a lifting boom and a folding boom, which are attached to each other in an articulated manner.

[0046] Preferably, a rotation device is provided between the implement and the scale. The operation of the rotation device can increase the tension in the flexible line in the extreme orientations of the crane.

[0047] The system preferably includes a control unit that includes calculating means, the aforementioned memory and the aforementioned software means.

[0048] The implement is preferably a gripper or grapple. These are the most common implements used in connection with a crane that can require an accurate weighing. Preferably, the end of the boom includes the link and an additional sensor for measuring an additional quantity, and the software means is configured to determine an effect of the additional quantity on the weighing result of the scale in a calibration measurement and to form the correction function so as to compensate the additional quantity, wherein the additional quantity is one or more of the following: a rotational torque of the link, a temperature, a pressure of a hydraulic fluid when the flexible line is a hydraulic hose. The system thus enables a monitoring of an additional quantity as well as a compensation of the same in the calculation, where necessary .

[0049] Preferably, the flexible line is a hydraulic hose. Hydraulic hoses are particularly thick and produce a significant force on the scale.

[0050] Alternatively, the flexible line can be any hose, conduit, cable, or other analogous element which is formed so as to be flexible and by means of which an operating force is conveyed via the crane to the implement or some other component suspended from the crane. Flexible means that the line is made of a material that can bend back and forth repeatedly without permanent deformation. A flexible line can be made, for example, of plastic, rubber or some other composite material, but not of metal or some other line material that is known to be rigid that cannot be bent back and forth.

[0051] Preferably, the flexible line is conducted externally past the scale from the boom to the implement.

[0052] There are preferably two or four flexible lines. For example, in hydraulics, both inlet and return lines of the hydraulics must be provided in order to operate the implement. The invention, which is not limited to the embodiments presented in the following, is described in more detail with reference to the attached drawings, wherein

[0053] Figure 1 shows a side view of a work machine on which a system according to the invention is arranged,

[0054] Figure 2a shows a side view of a crane depicted in a first orientation,

[0055] Figure 2b shows a side view of a crane depicted in a second orientation,

[0056] Figure 2c shows a side view of a crane depicted in a third orientation,

[0057] Figure 3 shows steps of a method according to the invention as a block diagram, and

[0058] Figure 4 shows a graph of a weighing result as a function of the orientation of the crane and the scale relative to each other .

[0059] A system 40 according to the invention is preferably implemented in connection with a work machine 11, which in the embodiment shown in Figure 1 is a forest machine, more specifically a forest tractor 15. Alternatively, it is also possible to implement the system in connection with, for example, a truck or the like. The basic parts of the system include a crane 12 that includes a boom 14, to which a scale 10 for weighing a load and, via the scale 10, an implement 16 for gripping the load are attached. The boom 14 includes two ends, a first end 17 that is closer to the point of attachment of the crane 12 to the work machine 11, and a second end 18 at the opposite end of the boom 14 relative to the first end 17. In addition, the system 40 includes a sensor 24 for determining a quantity that describes the angle between the boom 14 and the implement 16, as well as software means 22 with which it is possible to determine a correction function for the weighing result of the scale from the quantity that describes the angle of the boom and the implement.

[0060] Preferably, the scale 10 is what is known as a weighing link, which is preferably suspended by means of the link 34 from the end 18 of the boom 14 of the crane 12. The link 34 preferably includes two articulated joints 30 and 32, which are arranged perpendicular to each other. The rotation device 46, the scale 10 and the implement 16 are preferably connected underneath the link 34. The scale 10 and the implement 16 suspended from the scale can be rotated about a vertical axis by means of the rotation device 46.

[0061] The scale 10 can include a sensor 62 for measuring a force between the boom 14 and the implement 16. The sensor can be, for example, a strain gauge sensor. By means of the sensor 62, the weight of the load can be measured directly by the scale, rather than having to be estimated indirectly via some other quantity .

[0062] The implement 16 can be, for example, the grapple 46 shown in Figures 2a-2c, but it can also be some other implement, such as a gripper or a harvester head.

[0063] Preferably, the crane is an articulating boom crane as shown in Figures 2a-2c, which includes a base support 50 attached to the work machine, a pillar boom 52 attached to the base support 50 by a vertical articulated joint, a lifting boom 54 connected to the pillar boom by a horizontal articulated joint, and a folding boom 56 connected to the lifting boom by a transverse articulated joint. In this embodiment, references to the boom 14 refer to the folding boom 56. A link 34 is formed at the end 18 of the boom 14.

[0064] As shown in Figures 2a-2c, the crane 12 includes a flexible line 20 rigidly attached to one end to the boom 14, by means of which operating power is conveyed to the implement 16. In Figures 2a-2c, the flexible line 20 is attached at the other end to the rotation device 46 via which the operating force is transmitted to the implement 16. It is understood that, alternatively, it is also possible for the flexible line to be conducted directly to the implement.

[0065] The flexible line is preferably a hydraulic hose. Alternatively, flexible line can also refer to a protective encasing of electrical conductors or of a hydraulic line, to electrical cables, a pneumatic line or an analogous flexible line that conveys power. Instead of a single flexible line, there can be a plurality of lines such as, for example, in the case of hydraulic hoses where there are two, namely an inlet hose and a return hose. In all cases, there can also be a plurality of hoses or cables that are bundled together.

[0066] The system 40 also preferably includes the control unit 58 shown in Figure 1, which includes a calculation unit 60, a memory 38, and software means 22. In practice, the control unit can be a user interface already encountered in forest machines that already includes a calculation unit and a memory. The control unit 58 can be connected to the orientation sensors 24 and 26 in a wired or wireless manner in order to store the measurement data in the memory 38, from which the software means 22 can take the measurement data, which the calculation unit uses to correct the weighing result of the scale 10. Alternatively, it is also possible for the software means, the memory, and the calculation unit to be configured as a cloud service, in which case the system includes data transfer means in order to send the measurement data to the correction calculation implemented as a SaaS service, from which the corrected weighing result is returned to the system.

[0067] The orientation sensor 24 of the boom 14 can be, for example, an acceleration and orientation sensor, which can be a component in a crane that uses tip control. The second orientation sensor, for its part, can be, for example, part of the rotation device, since the rotation device is suspended from the scale by the force of gravity and its orientation is essentially the same as the orientation of the scale.

[0068] Alternatively the second orientation sensor can also be part of the scale.

[0069] With a crane equipped with tip control, in some cases, the system according to the invention can be implemented exclusively in the form of a software component that utilizes a scale, orientation sensors, a memory, and a calculation unit that are already present to calculate the corrected weighing result. A tip control can be implemented in various ways that are well known to a person skilled in the art. What is important for this invention is that the position of the end of the boom is known with a tip control, and this position correlates directly with the orientation of the boom and the implement relative to each other. It is not necessary to determine the orientation separately, but rather quantities of the tip control in the coordinate system of the work machine, or derivatives or partial variables of the same (distance from the axis of rotation, height in relation to the point of attachment on the machine frame, pivot angle, etc. ) can be used as the variables ("a quantity that correlates with the angle between the boom and the implement") of the correction function .

[0070] Instead of orientation sensors, it is also possible to use a sensor that determines a quantity that describes the angle between the boom and the implement such as, for example, a position sensor that determines the position of the implement relative to the point of attachment of the crane to the work machine. It is also possible to use other geopositioning or imaging devices and methods to determine an orientation or position or both such as, for example, different camera systems, laser scanners, or radar. These kinds of devices can also already be installed on work machines for other purposes, in which case the method according to the invention can be implemented without any additional investment in equipment.

[0071] The steps of an embodiment of a method according to the invention are described next with reference to Figure 3. In this embodiment, the quantity describing the angle between the boom and the implement is directly the angle between the two, which is determined by determining the orientation of the boom and the orientation of the implement. It is understood with reference to this embodiment, however, that the steps of the method are also the same in the other implementations, merely the determination of the quantity describing the angle between the boom and the implement can be different.

[0072] The method includes three basic steps, namely a tuning prior to the lifting of the load, which is represented by the reference number 200, the steps of grabbing and weighing the load, represented by the reference number 202, and the step of correcting the weighing result, which is represented by the reference number 204. In a preferred embodiment, in the step of tuning the scale, what is known as the zero position, in which the error resulting from the angle between the boom and the implement is zero and the weight registered by the scale is correct, is determined in a step 205. At the same time, the angle between the boom and the implement in the zero position or a quantity that describes said angle is determined. The zero position is preferably obtained by taring the scale. In a step 206, the crane is moved into at least one other orientation, where the zero position is the second tuning orientation, preferably into 3 to 20 different orientations, in each of which the tuning weighing result registered by the scale is determined by means of the scale. The orientations preferably include a minimum of two tuning orientations, of which one can be the zero position. Naturally, however, a more accurate and more reliable error compensation is achieved by using a plurality of tuning orientations. Preferably, the tuning orientations can be the extreme orientations of the crane, wherein in one of these orientations the end of the boom 14 is as close as possible to the articulated joint of the crane with the working machine, in a second it is as far away as possible from said articulated joint, in a third it is as low as possible and in a fourth it is as high as possible.

[0073] In a step 208, in addition to the weighing result, tuning orientation data of the scale and of the boom assembly in relation to each other is determined using an orientation sensor or sensors. In a step 210, both the tuning weighing data and the tuning orientation data are stored together in the memory of the control unit by the software means. This step can be repeated a number of times in a loop, always returning to step 206, until a number of tuning orientations have been obtained that is sufficient for accuracy. In a step 212, the software means determines a preferably continuous correction function based on the successive tuning weighing data points and tuning orientation data points, and the weighing result of the weighing step can be corrected by means of the correction function for every orientation of the crane from one extreme orientation of the crane to the other.

[0074] According to a preferred embodiment, what is known as the zero position, in which the error resulting from the angle between the boom and the implement is zero, is determined during the tuning step. This is preferably achieved by taring the scale in said zero position.

[0075] According to one embodiment, tuning is performed three- dimensionally with respect to two different axes, since the work machine to which the crane is attached can also be on an incline during a tuning weighing. This produces a more accurate correction function.

[0076] According to a further embodiment, the system includes the additional sensor 36 shown in Figure 1, which in this embodiment determines a rotational torque of the link 34. A rotational torque affects the weighing result of the weighing link so that a deviation from an optimal tension can be taken into account in connection with the formation of the correction function, provided that the effect of a change in rotational torque on the weighing result has been established in advance for the different tuning rotational torques. Instead of a rotational torque, the additional sensor can be configured to determine one or more other additional quantities such as, for example, a pressure of a hydraulic fluid in a hydraulic hose when the flexible conductor is a hydraulic hose, or a temperature. In this context, compensation does not refer to a temperature compensation of an internal calculation of the scale, but rather to the compensation of the error caused by the angle between the boom and the implement by means of the correction function. Preferably, the correction function can be a fitting between tuning orientation points. This allows a correction function to be formed that corrects the weighing error quite well in all orientations of the crane.

[0077] Figure 4 shows a curve plotted by a line 54 between tuning weighing results in different tuning weighing orientations vp, of which there are eight in this figure. Naturally, the mass of the tuning load is constant in all tuning orientations. The correction function f can be determined from the function of the curve of the tuning weighing results in such a manner that the correction function returns the weighing result to the actual mass of the tuning load in all tuning orientations.

[0078] After the tuning step 200, one can move to the step 202 of lifting and weighing the load, in which the implement is moved by the crane to the load to be lifted in a step 214, the load is gripped by the implement in a step 216, and the load is weighed by the scale to determine a weighing result in a step 218. During a movement, the angle a between the longitudinal axis A of the boom 14 and the line J formed between the end 18 of the boom 14 and the implement 16 changes, as illustrated in Figures 2a-2c, which also causes a change in the relative distances between the points of attachment of the flexible lines that convey a force from the crane to the implement. Weighing can be carried out in a stationary position or while in motion, as the software means is able to take this into account in a weighing according to the prior art using acceleration sensors. At the same time, in a step 220, the orientation data of the scale and the boom relative to each other is determined based on the orientation data of the orientation sensor and the orientation data of the second orientation sensor. In a step 222, the weighing result and the orientation data of the scale and the boom relative to each other are stored in the memory by the software means.

[0079] Finally, in the correction step 204, the software means retrieves the weighing and orientation data in a step 224, fits, in a step 226, the orientation data into a correction function, by means of which the weighing result is processed and converted into a corrected weighing result in a step 228. The conversion of the weighing result into a corrected weighing result can be, for example, a multiplication or a division of the weighing result by a correction coefficient. Finally, in a step 230, the software means stores the corrected weighing result in the memory.

[0080] The description of the steps presented above is only one example of an implementation of the correction of a weighing result. It is understood that the correction can be modelled in other ways within the limits set out in the patent claims.

[0081] Preferably, the correction of the weighing result is performed separately for each weighing result, which produces the best weighing accuracy, although in a simplified form the correction can be performed by calculating an average of the weighing orientations and processing the total mass of the weighing results with the correction function once only.

[0082] Two different weighing technologies are mainly used in crane scales: hydraulic pressure or strain gauge sensors. The operation of most scales currently in use is based on hydraulic pressure and its measurement. A weighing link containing a hydraulic cylinder is installed between the boom of the crane and the rotator, wherein the pressure of the hydraulic oil contained in the weighing link changes when a load is lifted. The pressure and the change in pressure are measured by a pressure sensor, the measured values of which are converted into a weighable mass. The operation of the pressure sensors is often based on a mechanical deformation. A flexible material located in the measuring end of the pressure sensor deforms as a function of the pressure acting on it, and the measurement can be performed, for example, by registering the deformation of the measuring end of the sensor by means of an electric current. The measurement can also be performed by measuring the correlation between an electrical capacitance of a resistor of the sensor and the deformation of the material of the sensing end of the sensor.

[0083] The scale used in a method and in a system according to the invention can be, for example, a Tamtron OneTimberSG, which includes an angle sensor for determining the orientation of the scale. This sensor is preferably the cited second orientation sensor in a system according to the invention.

[0084] Although the description of the invention presented in the foregoing is preferably applied to the correction of a systematic measurement error of a weighing link, exactly the same method is also applicable to a crane scale solution in which the mass of the load is determined based on data obtained from the crane. In practice, the determination of the mass is carried out based on the pressure sensor of a lifting cylinder in this case, although it is also possible to utilize pressures of other cylinders, or, at least in principle, different power and energy measurements of the crane. In these cases as well, a systematic error may arise due to the fact that flexible lines run across each articulated joint of the crane, which can cause a systematic error. This method makes no distinction with regard to the origins of the systematic error depending on the weighing data and orientation.

Claims

CLAIMS1. A method for weighing a load for a loader (12) , wherein the crane (12) includes a boom (14) , an implement (16) for gripping the load, and a flexible line (20) for conveying an operating force from the boom (14) to the implement (16) , characterized in that the crane (12) further includes a scale (10) that can be used by the crane (12) , and in the method- the scale (10) is tuned at least once prior to use of the scale (10) in different tuning orientations of the crane (12) in order to form a correction function that compensates a systematic error that depends on the angle between the boom (14) and the implement (16) as a function of the orientation of the crane (12) ,- a weighing result is measured with the scale (10) by weighing the load, and- the weighing result of the scale (10) is automatically corrected as a function of orientation using software means (22) and by means of the correction function by determining a quantity that correlates with the angle between the boom (14) and the implement (16) during weighing.

2. A method according to claim 1, characterized in that the boom (14) includes two ends (17, 18) , wherein the first end (17) is closer to a point of attachment of the crane (12) to the work machine (11) when the crane (12) is fully extended and the second end (18) lies opposite the first end (17) , and the scale (10) is arranged between the second end (18) of the boom (14) and the implement (16) in order to measure forces transmitted from the implement (16) to the boom (14) .

3. A method according to claim 1 or 2, characterized in that the angle between the boom (14) and the implement (16) is unique in each tuning orientation.

4. A method according to any of claims 1 to 3, characterized in that the scale (10) includes a sensor (62) for measuring the force acting on the same between the parts of the crane (12) that are attached to the scale (10) .

5. A method according to any of claims 1 to 4, characterized in that the systematic error contains at least an error caused in the weighing result of the scale (10) by the flexible line (20) .

6. A method according to any of claims 1 to 5, characterized in that the tuning of the scale (10) is carried out at least once prior to use of the scale (10) by determining the systematic error in at least two tuning orientations of the crane that differ with regard to the angle between the boom (14) and the implement (16) and by forming the correction function that compensates the systematic error as a function of the orientation of the crane (12) based on this determination .

7. A method according to any of claims 1 to 6, characterized in that the orientation of the scale (10) and the boom (14) relative to each other is the angle between them.

8. A method according to any of claims 2 to 7, characterized in that a link (34) including two articulated joints (30, 32) that are perpendicular to each other is provided between the second end (18) of the boom (14) and the implement (16) , and in the method the tuning of the scale (10) is carried out with respect to both articulated joints (30,32) in order to form the correction function, and this correction function is used to compensate the weighing result.

9. A method according to any of claims 1 to 8, characterized in that the crane (12) includes an additional sensor (36) for determining an additional quantity, and in the method an effect of the additional quantity on the measurement result of the scale (10) is determined and the correction function is formed, which takes into account the effect of the additional quantity so as to compensate the additional quantity, wherein the additional quantity is one or more of the following: a rotational torque of the link (34) , a temperature, a pressure of a hydraulic fluid when the flexible line (20) is a hydraulic hose.

10. A system (40) for weighing a load, wherein the system(40) includes a crane (12) that includes a boom ( 14 ) ,- an implement (16) for gripping the load, and- a flexible line (20) between the boom (14) and the implement (16) for conveying an operating force to the implement (16) , wherein the system (40) further includes- a sensor (24) for determining a quantity that correlates with the angle between the boom (14) and the implement (16) , and- software means (22) for processing measurement data of the scale (10) and a memory (38) for the software means (22) , characterized in that the system (40) further includes a scale (10) connected to the boom (14) for weighing the load, and the software means (22) is configured- to determine, in different tuning orientations of the crane (12) , a correction function that compensates a systematicerror that depends on the angle between the boom (14) and the implement (16) as a function of the orientation of the crane (12) ,- to store the correction function in the memory (38) , and- to automatically correct the weighing result of the scale (10) during lifting as a function of orientation by means of the correction function by determining the quantity that correlates with the angle between the boom (14) and the implement (16) by means of the sensor (24) .

11. The system according to claim 10, characterized in that the sensor (24) is an orientation sensor of the boom (14) for determining the orientation data of the boom (14) , and the system further includes a second sensor (26) configured to be connected to the scale (10) for determining the orientation data of the implement (16) .

12. A system according to claim 10 or 11, characterized in that the scale (10) is a weighing link, preferably suspended between the boom (14) and the rotation device (46) .

13. A system according to any of claims 10 to 12, characterized in that the scale (10) includes a sensor for measuring the force acting on the same between the parts of the crane (12) that are attached to the scale (10) .

14. A system according to any of claims 10 to 13, characterized in that the end (18) of the boom (14) includes a link (34) and an additional sensor (36) for measuring an additional quantity, and the software means (22) is configured to determine an effect of the additional quantity on the measurement result of the scale (10) in a calibration measurement and to form the correction function for compensating the additional quantity, wherein the additionalquantity is one or more of the following: a rotational torque of the link (34) , a temperature, a pressure of the hydraulic fluid in the flexible line (20) when the flexible line is a hydraulic hose.

15. A system according to any of claims 10 to 14, characterized in that the flexible line (20) is conducted externally past the scale (10) from the boom (14) to the implement (16) .

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