KR100455038B1 - Method for measuring wheel axel weight and apparatus thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for measuring a load on a vehicle, wherein at least one strain gauge attached to a leaf spring of a suspension device of a vehicle is loaded on a vehicle, and at a time due to an impact according to a load to be loaded. Measure the dynamic strain change, measure the static strain change according to the cargo loaded on the vehicle, and the friction between each plate constituting the preset leaf spring and the impact energy when loading the cargo from the dynamic strain change is released The present invention provides a method and apparatus for measuring a load on a vehicle, wherein the static strain change is obtained by correcting the static strain change from the ratio of impact energy (friction impact energy) in an ideal state.

Description

METHOD FOR MEASURING WHEEL AXEL WEIGHT AND APPARATUS THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring a load on a vehicle, and more particularly, to a load measuring apparatus capable of accurately measuring a load and a load on a vehicle in real time.

Under the Road Traffic Law, the weight limit of vehicles is 10 tons (5 tons) and 40 tons of gross weight. (Herein below, congratulation (or axle load) refers to the load on the entire axle of the vehicle, and "lubricated load" refers to the load on one of the wheels on both ends of the vehicle. Accordingly, the word "load" is a concept including "lubricated load" and "axial load". However, in this case, 10 tons of axial load is an axis type (single axis, continuous axis) or an inter-axis distance and tire number in the case of a continuous axis. (Single wheel, double wheel), etc., are not considered, and the total weight is also irrespective of the vehicle type (single vehicle, connected vehicle) or the number of axes. Of these limits, the upper limit of the total weight of the vehicle, 40 tonnes, is based on a limit of 10 tonnes x 4 axles = 40 tonnes per axle, based on a four-axle semi-trailer vehicle. The criteria set for Therefore, vehicles with a total weight of 40 tons or more than 10 tons of axial load are regarded as overload vehicles by road method, regardless of type.

However, since the cargo loading place and the weighing station are spatially separated from each other, the actual vehicle load can be measured only after the loading is completed. Therefore, depending on the driver's experience, there is no choice but to load the cargo, and it is difficult to unload the loaded cargo even if the weighing center detects an overload after the loading is completed. For this reason, the driver has no choice but to drive the vehicle even when the driver is overweight.

Therefore, at present, the current weight restrictions of the road traffic law are extremely difficult to achieve the original legislative purpose of preventing road damage by overloading vehicles, and excessive penalties and sanctions result in enormous property disadvantages for the driver.

In the related art, a method of obtaining a build-up of a vehicle from a strain change according to the weight of a cargo loaded by attaching a strain gauge to a leaf spring of a vehicle has been proposed, but in such a method, the friction force generated between the multiple springs constituting the leaf spring is applied. There is a problem that does not consider much difference with the actual weight of the vehicle on which the cargo is loaded.

Accordingly, it is an object of the present invention to provide a vehicle deceleration measuring apparatus having high precision and stability in a vehicle mounted state and a measuring method thereof.

In particular, it is an object of the present invention to provide a method capable of accurately measuring the actual weight in consideration of the influence of physical factors related to the strain change when loading cargo in a vehicle.

1 is a perspective view schematically showing a suspension device of a general vehicle.

Figure 2 is a graph showing the strain occurring in the leaf spring when loading the vehicle over time.

Figure 3a and 3b is a circuit diagram showing a sensor unit for the in-vehicle measurement of the vehicle of the present invention.

4A and 4B are schematic views showing a structure in which the sensor unit of the present invention is arranged on a leaf spring of a vehicle.

5A and 5B are graphs showing the correction of the error of the actual weight with respect to the measured value at full and tolerance.

6a and 6b schematically show different examples of the strain measurement method according to the present invention,

Figure 6c shows an experimental method for simulating the weight change applied to each wheel when the vehicle is in an uneven area.

7 is a flowchart illustrating a procedure of the vehicle load measuring method of the present invention by way of example.

The present invention measures the amount of impact applied to the leaf spring of the vehicle when loading the cargo in the vehicle and converts it to the actual weight measured when stopping at a flat place. Therefore, when the work of the truck can know the weight immediately, it is possible to prevent the overload.

Specifically, the present invention measures the dynamic strain change with time due to the impact of the load being loaded while loading the cargo on the vehicle with at least one strain gauge attached to the leaf spring of the suspension of the vehicle, The static strain change is measured according to the cargo loaded on the vehicle, and the impact energy in the ideal state in which friction between the impact energy at the time of loading the cargo and each plate constituting the preset leaf spring is released from the dynamic strain change (friction release) A method for measuring a load on a vehicle, characterized by obtaining the actual load axial load by correcting the static strain change from the ratio of impact energy).

The correction of the static strain change is performed by the following equation.

Here, the impact energy at the time of loading, the dynamic strain change x time, α is the conversion factor during the celebration, ε _s means the strain due to the load load in the stationary state, respectively.

In addition, the present invention includes at least one sensor unit attached to each leaf spring of the suspension of the vehicle for measuring the strain change according to the load of the vehicle; It provides a load measuring device of the vehicle comprising a control unit for converting the load load of the vehicle by reading the strain change per axis of the vehicle in a static state and a dynamic state when loading the cargo in the vehicle.

According to an aspect of the present invention, the strain gauge of the full bridge attached to the leaf spring obtains the strain due to the pure loading load with temperature compensation, and simultaneously measures the amount of impact applied during loading. Therefore, in comparison with the magnitude of the frictional force acting between the multiple leaf springs through the impact amount at the time of loading, it is to be converted into the ideal loading load obtained from the known load spring and strain relationship equation.

According to another aspect of the present invention, in order to prevent an error caused by the commercial weighing device measuring the weight of the entire vehicle and converting the load, the strain signal per axis of the vehicle and the weighing value of the vehicle are inputted independently. Measurement is possible. In addition, since the material constant such as the leaf spring age is different for each vehicle, by repeatedly correcting it from the standard value, it is possible to configure the device having an independent weight conversion formula of the actual vehicle.

On the other hand, according to another aspect of the present invention, by independently processing the signal of the strain gauge per wheel of the vehicle and the congratulations accordingly to obtain the congratulations of the entire vehicle to be generated on the uneven surface, such as the uneven surface This can prevent the error of load measurement.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a perspective view schematically showing a suspension device of a general vehicle. Suspension of a vehicle connects an axle shaft to a vehicle body and absorbs vibrations and shocks received from the road surface while driving, thereby improving ride comfort and safety of the vehicle. The suspension device of FIG. 1 is composed of a shock absorber for adjusting the free vibration of the spring and the spring, a shock absorber for improving the riding comfort, a stabilizer for preventing the left and right vibration of the vehicle, and the like. The illustrated spring is a leaf spring, both ends of which are attached to the vehicle body by means of shackles and shackle pins to support the vehicle body. Since the spring supports the load of the vehicle body, in the present invention, the sensor portion for measuring the load of the vehicle is mounted on the spring.

When loading a vehicle, the strain generated in the leaf spring varies depending on the loading condition, which is caused by the friction force between the multiple springs constituting the leaf spring.

2 is a graph showing the strain (ie, strain change) occurring in the leaf spring when loading the vehicle over time.

Looking at the drawings, the strain at the time of loading in an ideal state, it can be seen that the strain increases over time and is maintained at a constant size. In practice, however, the static strain measurement, that is, the static strain change after the cargo has been loaded with the vehicle stationary on a flat surface, shows that it is less than ideal over time. This is because the weight of the cargo loaded by the friction between the leaf springs is not accurately transmitted as the strain change. Therefore, the static strain measurement alone underestimates the load due to the loading of cargo, so that accurate load is not possible. Such underestimation may cause a difference to 20% of the actual weight, which may be a big burden on the vehicle driver.

On the other hand, when loading the cargo into the vehicle, considering the temporal change of the strain rate due to the impact, it can reflect the effect of the friction between the leaf spring when loading, it will be able to accurately obtain the actual load.

Accordingly, in the present invention, the impact energy is obtained by dynamically measuring the change in strain due to the weight of the cargo applied to the leaf spring of the vehicle when loading the cargo, and this is an ideal state, that is, the impact in the state that the friction of the leaf spring is released Compare the energy to the strain in the static state.

The impact energy applied to the leaf spring when loading the vehicle in the vehicle is a product of the dynamic strain εv and the time ΔT in FIG. 2, and is expressed as in Equation (1) below.

By calculating the friction release impact energy in the ideal state in which the friction between the layers is eliminated in advance, and calculating the ratio with the impact energy at actual loading, the error of deformation in the static state can be estimated. By correcting the static strain by 2), the actual weight can be converted at the time of loading.

Where α; Fantasy factor in celebration

ε _s ; Strain due to loading in stationary state

The dynamic strain, that is, dynamic strain change with time, is preferably measured in the range of 20 to 200 times per second, more preferably about 50 to 100 times per second. The measurement is controlled so that the sensor unit detects and outputs a dynamic change through the control unit. The result is temporarily stored in the storage unit in the control unit, and the impact energy at the time of loading is calculated by calculation.

The sensor unit of the present invention comprises at least one strain gauge capable of measuring the strain change of the leaf spring, it is preferable to include at least two strain gauges to obtain a stable measurement value. An example of the structure of the sensor unit is as follows.

Figure 3a shows a circuit diagram of a sensor unit 200 for measuring the wheel load of the vehicle according to the present invention. The wheel load measurement sensor unit 200 according to the present invention includes a bridge circuit including a pair of strain gauges 210 and 220 and fixed resistors 230 and 240. Here, each of the fixed resistors 230 and 240 has the same resistance value, and the resistance value of the fixed resistor 220 is equal to the resistance value of the strain gauges 210 and 220 in the no-load state.

When an external power source V _s is applied, the output voltage V _o of the bridge circuit is transferred to the control unit and converted into a load. The pair of strain gauges 210 and 220 are mounted on one spring.

The output _Vo of the bridge circuit of FIG. 3A can be calculated by the following equation (3).

Here, R _s1 and R _s2 refer to the resistances of the strain gauges 210 and 220 in the state where a load is applied, respectively.

4A and 4B illustrate another form in which the strain gauges 210 and 220 of FIG. 3A are mounted to the leaf spring 400 of the vehicle.

In FIG. 4A, a pair of strain gauges 210, 220 are mounted on the same side of the spring 400, and these strain gauges 210, 220 are attached to be perpendicular to each other. For example, when the first strain gauge 210 is mounted in parallel with the longitudinal direction of the spring 400, the second strain gauge 220 may be mounted to be perpendicular to this. However, it should be noted that in this example, the strain generated in the leaf spring 400 due to the load acting on the vehicle has only the spring 400 longitudinal component. Therefore, the strain due to the vehicle load can be sufficiently measured by the first strain gauge 210, and the second strain gauge 220 does not directly contribute to the measurement of the strain. However, the second strain gauge 220 is not for the purpose of measuring the strain, but for compensating for the characteristic change of the strain gauge, and has a meaning as a reference resistance.

In such an arrangement of strain gauges, there is no strain component due to load in the direction perpendicular to the spring longitudinal direction, but strain due to Poisson's ratio. Therefore, when the load of the vehicle is applied to the spring 400, if the resistance increase of ΔR occurs in the first strain gauge 210 arranged in the longitudinal direction, the second strain gauge 220 arranged in a direction perpendicular thereto The resistance decrease of ΔR occurs due to the Poisson's ratio. Therefore, the output _Vo of the bridge circuit can be calculated by considering these resistance changes in Equation (3).

Meanwhile, in FIG. 4B, a pair of strain gauges 210 and 220 are mounted on opposite surfaces of the leaf spring 400, respectively. The first strain gauge 210 mounted on the top surface of the spring and the second strain gauge 220 mounted on the bottom surface of the spring are mounted in the same direction, that is, in the longitudinal direction of the spring. In such a strain gauge arrangement, if a load acts on the spring 400 and an increase in resistance of ΔR occurs in the first strain gauge 210, a resistance decrease of ΔR occurs in the second strain gauge 220. Therefore, the output _Vo of the bridge circuit can be calculated by considering this resistance change in the above equation. As described above with reference to FIG. 4A, even in this case, measurement of strain is enough for one strain gauge, and the other strain gauge has a meaning as a reference resistance.

The reason for configuring the bridge circuit by using a pair of strain gauges including a dummy strain gauge is as follows.

As can be seen from the above equation (3), the output (V _o ) of the bridge circuit according to the circuit configuration of Figures 3a and 3b is the resistance of the two active resistance elements (strain gauges 210, 220) irrespective of the fixed resistance It is determined by the values R _s1 and R _s2 . Therefore, each variable of Equation (3) which determines the output values of these strain gauges is subject to both the characteristic change of the strain gauge itself or the influence of the external environment, and in Eq. (3) these effects cancel each other out. For example, according to the structure of the sensor unit of the present invention, it is possible to ignore the change over time of the output value of the strain gauge due to deterioration of the characteristics of the strain gauge itself or deterioration of the elastic deformation characteristics of the structure (spring) with the strain gauge. In addition, even if the sensor unit changes in ambient temperature due to the driving state of the vehicle, geothermal heat, or the like, these effects are canceled out and not reflected in the output signal.

As mentioned above, although the sensor part circuit structure suitable for measurement of a wheel load was demonstrated, the technical idea of this invention can be easily applied also to the measurement of a load factor.

Figure 3b shows the circuit structure of the sensor unit 300 of the present invention used for the load accumulation measurement. As shown, four strain gauges 310, 320, 330, and 340 constitute one bridge circuit.

One pair of four strain gauges 310, 320, 330, 340 is mounted on a first spring at one end of the axle, and the other pair of strain gauges 330, 340 It is mounted on a second spring at the other end of the axle. The method of mounting the strain gauge on the spring is similar to the method of mounting the strain gauge for measuring the wheel load described above. For example, two pairs of strain gauges 310, 320 or 330, 340 may be mounted on the same surface of one spring, one of which may be mounted in the longitudinal direction of the spring and the other of which is perpendicular to the spring. Alternatively, two strain gauges may be mounted longitudinally on opposite surfaces of the spring.

If the former case, the output of the bridge circuit of Figure 3b can be expressed by the following equation (4).

Here, it is assumed that the load applied to each of the springs on both ends of the axle is the same, and therefore, the resistance change of the strain gauges 310, 320, 330, and 340 is also assumed. Of course, the vehicle-vehicle measuring apparatus of the present invention is applicable even when the load acting on each spring is not the same. As before, the remaining two strain gauges mounted perpendicular to the spring longitudinal direction will experience a change in resistance due to Poisson's ratio.

Due to this assumption, the change (ΔR / R) of the resistance value of the strain gauge obtained by the above equation (4) corresponds to the average value of the wheel load applied to both ends of the axle. Therefore, by taking this multiple of the resistance change, the load on the actual axle can be found, which must be taken into account later in the signal processing and conversion to the load.

In this way, a pair of strain gauges are attached to each of the two springs at both ends of the axle to form a bridge circuit with these strain gauges, and the output of the vehicle can be obtained by measuring the output of the bridge.

The output _Vo from the sensor unit, ie the static strain and the dynamic strain, are converted into loads by the controller. The output _Vo from the bridge circuit is amplified by a signal amplifier in the control section and then converted into a digital signal by an analog / digital converter (A / D converter) in the control section. The converted signal is input to a calculation unit in the control unit and converted into a load.

The conversion to load is obtained using a correspondence relationship existing between the strain and the load, and the data of the correspondence relationship can be stored in the storage means in a table. For example, in equation (2) described above, the conversion factor α during the celebration is a proportional relationship of the general formula (primary equation) obtained from data obtained by experimentally obtaining the vehicle loading celebration for the strain gauge signal value. May correspond to

This proportional relationship can be stored in memory and can be modified by very simple operation. That is, compared with the signal value of the strain gauge and the actual ratio during the celebration after the vehicle is full, the α can be corrected so that the ratio of the celebration during the full ride to the signal value is in error.

Further, α may be corrected so as to compare the signal value of the strain gauge with the actual ratio of the celebration in the state in which no load is loaded on the vehicle, so that the ratio of the celebration during tolerance to the signal value is in error when α is in error. have.

By repeating this method, as the number of error corrections increases, the proportional relationship between strain and load can be obtained to minimize the error between the measured value and the actual weight. 5A and 5B are graphs showing an example of correcting an error of an actual weight with respect to a measured value at full and tolerance.

On the other hand, in the present invention, the signal of the strain gauge for each axis of the vehicle and the resulting congratulations are independently processed to obtain the congratulations of the entire vehicle. In this way, the load on each axis may be different in the inclined place or when the cargo is not evenly mounted on the vehicle. Therefore, the weight of the vehicle can be measured independently and the weight can be obtained to obtain the exact actual weight of the entire vehicle. do. In addition, the effects of the deterioration of the components constituting the shaft can be considered independently, which is preferable for the actual load and load measurement.

In this method, the bridge circuit is composed of two wheels of each wheel as one axis, but the parallel state of the two wheels on one axis may be broken on unpaved roads or uneven terrain where the floor is not uniform. Errors can occur in measuring loads. In order to improve such an error, it is desirable to independently obtain the signal of the strain gauge and consequent congratulation in each wheel unit instead of an axis unit, and process it to obtain congratulation in the whole vehicle.

To this end, the following experiment was performed.

First, as shown in Figs. 6a and 6b, a pair of suspension devices are simulated to put a weight of 1 kg on the left and right leaf spring models of elastic material, respectively, to arbitrarily create a state where the balance is broken. The weight of the instrument was measured and compared with the equilibrium value. FIG. 6A illustrates an example in which a bridge circuit (that is, one bridge circuit per axis) is configured on an axis basis, and FIG. 6B illustrates an example in which a bridge circuit (that is, two bridge circuits per axis) is configured on a wheel basis. The equilibrium state corresponds to the case where 1 kg of weight is placed on both iron plates in the same way (ie, in this case, it is flat ground). This is the case. Figure 6c shows an example in which the weight of the lifting weight on both iron plates. Tables 1 and 2 below show the experimental results for the axial error values for the strain change measurements per axis and the axial error values for the strain change measurements per wheel, respectively.

When the weights applied to both wheels (L, R) were the same, there was almost no error regardless of the method of measuring strain.However, when the weights were different, the variation of strain per wheel was less and the deviation was very accurate. It can be seen that can be obtained.

7 is a flowchart illustrating a load measuring process of the present invention. First, after inputting tooth weight information, for example, the number of shafts, the number of tires, the vehicle type, and other degrees, the tolerance of each axis and the strain value at the time of full parking are input from the sensor unit to automatically calculate the load. At this time, the impact energy is determined from the dynamic strain to determine the correction. If correction is required, the load is automatically calculated by the correction and the load is displayed.

If an error occurs between the indicated loading load and the actual load measured at the weighbridge, modify the relation between the strain and the load from the value corresponding to the error and repeat the above procedure to obtain a more accurate loading load.

The above process may be programmed in a microprocessor in the control unit so that a series of procedures may be automatically performed, and a description of a detailed program source is omitted here.

According to the load measuring device and the load measuring method of the present invention described above, it is possible to provide a load measuring device that can know the load load in an ideal state even in the state of impact applied during loading.

In addition, the operator can easily measure the load of the vehicle actually loaded using the load measuring device of the present invention with a simple operation, thereby preventing the overload at the source.

Claims (10)

Attaching at least one strain gauge on the leaf spring of the vehicle suspension system, and measures the dynamic strain change due to the impact of the load being loaded while loading the vehicle over time, and by the cargo loaded on the vehicle Ideal for measuring static strain change, measuring impact energy during loading and static strain change due to preset cargo, and breaking the friction between impact energy during loading and each plate constituting the preset plate spring. The static strain change is corrected from the ratio of the impact energy (friction impact energy) in the state to obtain the actual loading celebration, The dynamic strain change is measured in the range of 50 to 200 times per second, Load shaft load by the correction of the static strain change is calculated by the following equation. <Formula> (Here, the impact energy at the time of loading is the dynamic strain change × time, α is the conversion factor during the celebration, ε _s refers to the strain due to the loading load in the stationary state) delete delete The method for measuring a load on a vehicle according to claim 1, wherein the conversion factor α during the celebration is obtained by experimentally obtaining a loading celebration weight of the vehicle with respect to a signal value of the strain gauge. 5. The method according to claim 4, wherein α is compared with the signal value of the strain gauge and the actual ratio during celebration after the vehicle is full on the cargo so that α is equal to the signal value during full celebration with respect to the signal value when there is an error in the α. Method for measuring the load of a vehicle, characterized in that the correction. 5. The method according to claim 4, wherein when there is an error in α compared with the signal value of the strain gauge and the actual ratio during celebration without loading the vehicle, the ratio during celebration during tolerance to the signal value A method for measuring a load on a vehicle, wherein α is corrected. The method of claim 1, wherein the strain gauge independently processes the signal of the strain gauge for each axis of the vehicle and the resulting celebration during the celebration of the entire vehicle. The method of claim 1, wherein the strain gauge independently processes the signal of the strain gauge per wheel of the vehicle and the congratulations accordingly, thereby obtaining the congratulations of the entire vehicle. At least one sensor unit attached to each leaf spring of the suspension device of the vehicle to measure strain change according to the load of the vehicle; A control unit which reads the change of strain per axis of the vehicle in the static state and the dynamic state from the sensor unit when converting the cargo into the vehicle, and converts the loading celebration of the vehicle by the following relationship; (Where, the impact energy at the time of loading is the dynamic strain change x time, α is the conversion factor during the celebration, ε _s refers to the strain due to the loading load in the stationary state); Load measuring device of the vehicle comprising a. The apparatus of claim 9, wherein the sensor unit independently measures the strain change of each wheel of the vehicle.