FI93058C - Procedure for weighing a load - Google Patents

Description

93058

METHOD OF WEIGHING THE LOAD

The invention relates to a method for weighing a load according to the preamble of claim 1.

A method and apparatus for weighing a load are already known from Finnish patent application 905840. In this method, sensors are placed on a pallet equipped with supports, such as legs or wheels, such as a driving deck or a container, from the signals of which the weight of the load is determined. These sensors are placed on a rigid frame of the chassis in the vicinity of the attachment points of the supports and measure the deformations and / or stresses caused by the load 15 and determine the weight of the load.

A disadvantage of the known method and device is that the placement of the sensors at the measuring points in the vicinity of the attachment points of the supports takes place mainly experimentally, whereby locating the most suitable measuring points in different truck construction may produce difficulties.

The object of the invention is to eliminate the above-mentioned drawback. In particular, it is an object of the invention to provide an efficient method for determining measuring points so that the sensors can be attached directly to the load platform and then calibrated so that the correct measurement result, i.e. the load weighing result, is obtained.

The method according to the invention is characterized by what is stated in the appended claims.

In the method according to the invention for weighing a load arranged on a load base, sensors, preferably strain gauge sensors, are added to measuring points arranged in the vicinity of the support points, i.e. support points, on the rigid frame of the load base. According to the invention, the measuring points are determined on the basis of the Finite-Element Method (FEM) known per se for determining the shear stresses of the structures, so that the measuring points are placed in the vicinity of the support points in substantially undisturbed shear stress ranges; and the sensors 10 attached to the determined measurement points are calibrated on the basis of test measurements by determining correction factors based on the weight loads of the other support points acting on each support point, which correction factors are used to calculate actual weight measurement values such as total weight 15 and / or reference point weights.

In one embodiment of the invention, the load is arranged to rest on the chassis frame at desired points on different sides of the support points, whereby the chassis body 20 is subjected to point loads, the shear stresses caused by which are determined. The advantage of this method is that, in particular, the calibration procedures can be carried out simply and reliably.

In one embodiment of the invention, to determine the measurement points, the load platform is modeled for element procedure processing.

In one embodiment of the invention, a number of truck chassis models are formed in advance, such as truck chassis models 30, which are based on modeling.

In one embodiment of the invention, a plurality of sensors are fitted at the same measuring point on the vertical side of the body at the same level at different angles to eliminate thermal expansion and secondary force effects.

*. In one embodiment of the invention, the sensors 3 93058 are connected to a data processing device, by means of which the weight loads and / or the total load on the supports are calculated using predetermined correction factors.

The method according to the invention has the advantage of being able to quickly determine measuring points on any load platform to which sensors, preferably strain gauge sensors, are attached for fast and real-time weight measurement of the load. The method according to the invention is suitable for measuring the load of lorries, trucks, vehicle combinations, trains, transport containers, elevators and other bulk-loaded devices on transport platforms.

A further advantage of the invention is that the installation of the measuring sensor and the entire equipment on existing platforms can be carried out quickly and reliably. This is especially the case when a pallet model already exists on the basis of which the 20-element method can be applied.

A further advantage of the invention is that the measuring points of the measuring sensors can be determined reliably and the measuring sensors can be attached directly to fixed chassis frame structures, where they are not alt-25 Tiina to breakage or to shocks and other strong fatigue stresses.

A further advantage of the invention is that it allows a fast and reliable computer-based weight measurement system to be implemented in a wide variety of truck platforms and thus significantly reduces the need for fixed weighing equipment. A further advantage is that rapid and continuous monitoring of overloads and overloads can be carried out, especially in vehicles.

35 The invention will now be described in detail. with reference to the accompanying drawing, in which Figure 1 is a schematic side view of the body structure of a car 4 93058 trailer; Figure 2 is a plan view of the frame structure of Figure 1; Figure 3 is an enlarged detail of the frame beam of the trailer of Figure 1, illustrating the modeling of the element method; Fig. 4 is a schematic side view of the frame structure of Fig. 1 with 10 point loading forces applied to the frame structure and showing the locations of the fulcrum and measurement points; Figures 5A, 5B, 5C and 5D show the distribution of shear forces in the longitudinal direction of a single frame beam in an arrangement according to the model of Figure 4, in which the individual point loads alternately act on the frame structure.

Figures 1 and 2 show the frame structure of a truck trailer. The frame 1 of the trailer comprises two parallel spaced-apart frame beams 2, 3, which are connected to each other by transverse supports 4, 5, 6 and 7. These supports further extend transversely beyond the frame beams 2, 3.

In addition, there may be other additional supports in connection with the frame beams 2, 3. In connection with the attachment points of the wheel bogies, there are further wheel bogie supports 8a, 8b for the front wheels 10 of the trailer 25 and wheel bogie supports 9a, 9b for the rear wheels 11. The wheels 10, 11 are then fastened to the frame beams 2, 3 from the support points Ά1, A2 and B1, B2, respectively.

Sensors, preferably strain gauge sensors, 30 are attached to the chassis 1, in this case to the trailer frame 1 and in particular to the frame beams 2, 3, at the points of attachment of the supports, i.e. the wheel support points A1, A2; B1, B2 in the vicinity of predetermined measuring points C1, C2, C3, C4 (Fig. 4). The weight K of the load acting on the trailer is determined from the signals given by the sensors installed at the measuring points on the basis of the deformations of the frame 1. The shear stresses on the frame in particular are determined by means of the sensors. measurement points.

The positions of the measuring points are determined on the basis of the element method FEM (Finite Element Met-5 hod) known per se. The element method determines the shear stresses on the trailer body 1 and in particular on its frame beams 2, 3. The basic idea of the element method is that any complex structure can be divided into simple basic parts, i.e. elements whose elastic and strength properties are known and which can be represented by mathematical formulas. These parts, i.e. the elements, are assembled as a whole, taking into account the interdependencies of all the parts. In this way, a model 15 of a trailer body 1 or a similar chassis is constructed which corresponds to the actual structure in terms of its elastic properties with sufficient accuracy.

The element method is illustrated in the example of Fig. 3, which shows a part of the frame beam 2, 3 as seen from the side (Fig. 1). According to the element method, the frame beam 1, 2 is divided into small elements 12. The total number of elements in the frame beams 2, 3 of the trailer may reach several thousand. The shear stresses on each element are calculated with the desired continuous load and / or certain point loads. Distribution of the load K in the longitudinal direction of the frame beams 2, 3 and the support points A1, A2; The location of B1, B2 is taken into account in the method in which the existing plurality of ready-made FEM software can be used by appropriately customizing them. The distribution of the shear forces along the longitudinal direction of the frame beam 2, 3 is obtained as a result of the calculation and can be presented either as a graphical graph or suitably in tabular form. The distribution of shear forces with respect to the support points can be used to determine the support reactions, i.e. the weight stresses on the supports.

· Assume that the frame beam 2, 3 is subjected to 93058 6 point loads ΚΙ, K2, K3, K4 in certain combinations (1 = K1, 2 = K2, 3 = Κ3, 4 = Κ4, - = 0) and the magnitude of each point load is similar to e.g. 1000 kg. When the point loads act one at a time, the shear force graphs for the frame beam 2, 3 shown in Figures 5 to 5 are obtained. When the point load K1 * 1000 kg acts on the front end of the frame beam 2, 3, the graph of shear forces is shown in Figure 5A. When the point load K2 = 1000 kg acts between the support points A1, B1 near the front end 10, a graph of the shear forces according to Fig. 5B is obtained. When the point load K3 = 1000 kg acts between the support points A1, B1 near the rear end, the shear pattern shown in Fig. 5C is obtained. When the point load K4 acts at the rear end of the frame beam 2, 3, the shear force graph according to Fig. 5D 15 is obtained. The corresponding shear force values are also shown in Table 1 below on rows 1-4 (i.e., the combinations 1_, _2_, _3_, and _4).

Table 1 illustrates the shear forces caused by the point loads K1, K2, K3, K4 with their various combinations in the vicinity of the support points at the selected measuring points C1, C2, C3, C4, which are shown schematically in Figure 4. The shear forces PA, at the front and rear bogie support points A, B 25 and on the basis of these the total weight KP on the frame beam 2, 3 has in turn been calculated. The reaction forces PA, PB and the total weight KP are shown by combinations of different point loads.

Calibration is performed by test loading 30 frames with a known load and measuring the load *. elongation e at the measuring point and the shear force V corresponding to the elongation e is calculated. According to the beam theory, the theoretical elongation V at the measuring point is calculated. Calculate the correction factor k 35 by dividing the theoretical shear force Vt by the measured shear force V (i.e. k = Vt / V). When the correction factor is known. roin k can be used to calculate the theoretical value of the shear force Vt caused by the load using the product of any measured shear force 93058 7 and the correction factor k.

Of course, when the previous operations are performed for each measuring point, the correction factor k for each of the 5 strips is known. Thus, the support reactions A and B can now be calculated. The support loads can be calculated by multiplying the support reactions by g = 9.81 m / s2. kg.

An example of the effect of point loads on a trailer frame beam 2, 3 is given above.

The measuring points C1, C2, C3, C4 are in this case selected from the vicinity of the support points A1, A2 and B1, B2, respectively, outside the bogies. In this case, the areas prohibited for load-20 are the areas between these anchorages. In the case of point loads, which was presented above, this can be easily arranged. If loads are applied to the frame beam 2, 3 in any of its longitudinal areas between the support points: 25 A1, A2 and / or B1, B2, measuring points and appropriate sensors must also be placed in their vicinity. In this way, there are no forbidden areas in the longitudinal direction of the frame beam.

The measuring points are placed in the vicinity of the support points, in particular because the differences in the shear forces acting on the different points of the support points make it possible to determine the support reactions, i.e. the weight stresses on the support points, reliably (cf. Table 1). This is especially emphasized when continuous loads are used, where the shear force curves and their values vary in the longitudinal direction of the load platform, in this case the frame beams 2, 3. In the case of point loads 93058 8, the freedom to place the measuring points is greater, as can be seen from the application example presented above. However, placing the measuring points in the vicinity of the support points is advantageous in this case as well, in order to avoid interference.

The measuring sensors are attached to the calculated measuring points, as already stated above. The sensors are preferably strain gauge sensors. Preferably, two or more 10-band strain gauge sensors are attached to each measuring point, i.e. a group of sensors at the same level at an angle to each other. The sensor array is further attached to a measuring point calculated on the vertical beam of the frame beam or the like.

In the embodiments of Figures 1 and 2, the sensor groups of the strain gauge strip-15 are fixed so that the measuring sensor groups 13a, 13b are attached to the measuring points C1, C2 of the beam 2, respectively, and the measuring sensor groups 15a, 15b of the beam 2, respectively. The measuring sensor groups 14a, 14b are attached to the measuring points C1, C2 of the beam 3 and the measuring sensor groups 16a, 16b to the measuring points C3, C4 of the beam 3, respectively.

The sensor groups 13a, 13b, 14a, 14b associated with the front wheel 10 and front wheel bogie measurement points C1, C2 are connected to the Wheatstone bridge so that the effects of sensor deformations are amplified at the bridge outputs, from where the bridge signal is fed to the amplifier to a data processing section 18, such as a microprocessor (Figure 30 2). Similarly, the sensor wheels 15a, 15b, 16a, 16b associated with the measuring points C3, C4 of the rear wheels 11 are connected to the Weston bridge and the difference signal from the outputs of the bridge is fed to an amplifier and a signal processing unit.

In connection with the data processing section 18, there are suitable display devices 19, 20, 21 for displaying the total weight measurement values of the front axle, the rear axle and li 93058 9, and preferably connections to the printer 22 and another computer 23 or the like.

The data processing unit 18 processes the measurement information from both the front and rear bogies and calculates the correction factors taking into account the weight loads acting on both bogies and the weight of the entire trailer load. These are displayed on the respective display devices 19, 20, 21.

It should be noted that the vehicle body, such as the frame beams 2, 3 of the trailer body 1, are always subjected to secondary stresses when the wheels 10, 11 are at different heights or when the vehicle is on an inclined surface or the load is asymmetrical. To this end, several sensors are placed at each measuring point so that these secondary effects can be eliminated. Thus, sensors, such as strain gauge sensors, can be placed at the measurement points on the vertical side of the frame beam, either on the same side of the frame beam or on different sides thereof. Furthermore, the sensors can be positioned so that their electrical connection is implemented in such a way that the effect of temperature changes on the measurement result can be eliminated.

The invention has been described in detail above. . 25 with reference to some preferred embodiments thereof. It should be noted, however, that the invention may be modified in many different ways within the scope of the inventive idea defined by the appended claims.

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II

Claims (6)

93058 11 A method for weighing a load (K) arranged on a pallet, the method comprising proximity to the rigid body (1) of the pallet in the vicinity of the attachment points (AI, A2, B1, B2) of the supports (8a, 8b, 9a, 9b) sensors, preferably stretch strip sensors (13a, 13b, 14a, 14b, 15a, 15b, 16a, 16b) are attached to the arranged measuring points (C1, C2, C3, C4), from the signals of which the weight of the load (K) is determined by the body (1) deformations, characterized in that - the measuring points (C1, C2, C3, C4) are determined on the basis of the finite element method (FEM-) known per se, A1, A2, B1, B2) in the vicinity of substantially undisturbed shear stress regions; and - the sensors (13a, 13b, 14a, 14b, 15a, 15b, 16a, 16b) attached to the specified measuring points (C1, C2, C3, C4) are calibrated on the basis of the experimental measurements by assigning correction factors (k) to each reference point (e.g. A1). ) on the basis of the shear stress loads of the other supporting points (A2, B1, B2), the correction factors (k) of which are used to calculate the actual weight measurement values, such as total weight and / or support point weights, from the actual weight measurement values. Method according to claim 1, characterized in that the load (K) is arranged to rest on the chassis frame (1) at desired points on different sides of the support points (A1, A2, B1, B2), whereby the chassis frame is subjected to point loads (K1). , K2, K3, K4) for which the shear stresses are determined. . Method according to Claim 1 or 2, characterized in that the load platform is modeled for element method processing in order to determine the measuring points 93058 12. Method according to Claim 3, characterized in that a number of truck chassis models, such as truck chassis models, are formed in advance, on the basis of which the modeling is carried out. Method according to one of the preceding claims, characterized in that a plurality of sensors are arranged at the same measuring point on the vertical side of the body at the same level at different angles in order to eliminate thermal expansions and secondary force effects. Method according to Claim 5, characterized in that the sensors (13a, 13b, 14a, 14b, 15a, 15b, 16a, 16b) are connected to a data-processing device (18) for calculating the weight loads on the supports and / or using predetermined correction factors. or total load. Il 13 93058