Detection device and measurement system

Abstract

The present invention provides a detection device and measurement system that can accurately calculate force based on detected strain, regardless of the characteristics of the strain-generating part. [Solution] The detection device 100 of the embodiment includes a setting unit 141 in which a proportionality constant and a limit value are set as individual parameters representing each basic model E, which is a series connection of a spring element and a Coulomb friction element, is associated with an overall model M which is a series connection of a basic model E which is associated with the relationship between strain generated in the strain generating part 12 and the force, and an input unit 142 which receives a signal from at least one detection element 13 which detects the strain of the strain generating part 12, and a force calculation unit 143 which calculates the force that depends on the calculation of each basic model E based on the strain from the input unit 142 and the parameters set for each basic model E, and estimates the force applied to the strain generating part 12 by summing the forces that depend on the calculation of each basic model E.

Description

Technical Field

[0001] The present invention relates to a detection device and a measurement system.

Background Art

[0002] Measurement systems such as force sensors and torque meters detect the strain of a measurement target to which a force is applied, and calculate the force (for example, torque) applied to the measurement target based on this strain. For example, there is a measurement system configured by a detection element that detects strain due to tensile strain or compressive strain using a strain gauge attached to a strain generating part, and a detection device that obtains a force from these strains.

[0003] The strain generating part is a mechanical element that detects the strain of the measurement target, and may be the measurement target itself, or a dedicated member assembled in series with the measurement target. In addition, a subordinate strain generating part may be configured in parallel without hindering the strain generated in the measurement target that is the main strain generating part. The strain gauge is a detection element that is attached to the strain generating part and whose resistance value changes according to the strain of the strain generating part. By configuring a bridge circuit using the strain gauge, strain can be detected based on changes in the output voltage of the bridge circuit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0005] In order to calculate a force with high accuracy using such a measurement system, it is preferable that the strain of the strain generating part and the force have a proportional relationship. More strictly speaking, the measurement accuracy depends on the mechanical characteristics resulting from the structure including the connection method of the strain generating part to the measurement target, the material, the environmental conditions, and the like.

[0006] However, when using the object to be measured as a strain-generating part, the strain-generating part does not necessarily possess ideal characteristics for measurement. For example, a vehicle's power transmission shaft is designed for power transmission, so it only needs to have the performance required of a transmission shaft, and does not necessarily possess ideal characteristics for torque measurement. In other words, the relationship between torque and strain does not show a linear straight line, and simple conversion using constants reduces the accuracy of the measurement. Furthermore, the hysteresis that occurs when the forward and return paths separate during the process of increasing the load and then returning to a no-load state is also a problem that contributes to the reduction in measurement accuracy.

[0007] The object of the present invention is to provide a detection device and measurement system that can accurately calculate force based on detected strain, regardless of the characteristics of the strain-generating part. [Means for solving the problem]

[0008] To achieve the above objectives, the detection device of the present invention comprises: a setting unit that associates the relationship between strain and force occurring in the strain-generating part with an overall model formed by connecting multiple basic models, each of which is a series connection of a spring element and a Coulomb friction element, in parallel, and sets proportionality coefficients and limit values ​​as individual parameters representing each basic model; an input unit that receives a signal from at least one detection element that detects the strain in the strain-generating part; and a force calculation unit that calculates the force based on the calculation of each basic model based on the strain output by the input unit and the parameters set for each basic model, and estimates the force applied to the strain-generating part by summing the forces based on the calculation of each basic model.

[0009] Furthermore, in the measurement system of the present invention, a measurement device comprising components outside the housing of the detection device and input / output units for external devices is connected to the components inside the housing of the detection device via wireless communication.

[0010] Furthermore, in the measurement system of the present invention, the detection device and the measurement device equipped with an input / output unit for an external device are connected via wireless communication. [Effects of the Invention]

[0011] According to the present invention as described above, whether the strain generating part is the object to be measured itself, or is attached in series with the object to be measured, or whether a subordinate strain generating part is configured in parallel without hindering the strain occurring in the object to be measured which is the main measuring part, the force transmitted by the object to be measured can be measured accurately based on the detected strain, regardless of the characteristics of the strain generating part. [Brief explanation of the drawing]

[0012] [Figure 1] This is a side view showing an example configuration of the measurement system of the embodiment. [Figure 2] Block diagram showing the detection device and measuring device of the embodiment. [Figure 3] Examples of graphs showing the linear characteristics of the measured object (A), the nonlinear characteristics (B), and the hysteresis characteristics (C) are shown. [Figure 4] (A) is a schematic diagram showing the configuration of the basic model, (B) is an example of a graph showing the relationship between force and displacement in the basic model, and (C) is an example of a graph corresponding to the generation and removal of strain when the relationship between strain and torque is represented by the basic model. [Figure 5] This is a schematic diagram showing the overall model. [Figure 6] Examples of graphs (A) to (C) show the behavior when the strain-torque relationship is represented by three different basic models, and example of a graph (D) shows the behavior when the strain-torque relationship is represented by the overall model. [Figure 7] This table shows specific examples of output strain from the input section of the detection device in response to load torque. [Figure 8] This graph shows the strain in response to the load torque corresponding to Figure 7. [Figure 9]In FIG. 8, this is a graph showing the slope of each section that the overall model should represent. [Figure 10] This is a table showing the calculation results of the proportionality coefficient and the limit value of each basic model based on the detected strain in the forward path corresponding to the increase of the load torque in FIG. 7. [Figure 11] This is a table showing the calculation results of the proportionality coefficient and the limit value of each basic model based on the detected strain in the return path corresponding to the decrease of the load torque in FIG. 7. [Figure 12] This is a flowchart showing an example of the torque calculation processing of the present embodiment. [Figure 13] This is a flowchart showing the torque calculation processing indicated by each basic model in FIG. 12. [Mode for Carrying Out the Invention]

[0013] A mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described with reference to the drawings. The present embodiment is applied to a measurement system S, and a detection device 100 and a measurement device 200 constituting the same. Further, a measurement method for performing the processing described below, and a program for causing a computer to execute the processing are also aspects of the present invention. Note that the illustration of the measurement device 200 is omitted in FIG. 1, and the illustration of components other than the detection element 13 of the detection device 100 is omitted in FIG. 2.

[0014] [Configuration] As shown in FIG. 1 and FIG. 2, the measurement system S is a system that calculates a force (for example, torque) applied to a measurement object from strain generated in a strain generating portion. Here, the measurement system S in which a subordinate strain generating portion is connected in parallel to a main strain generating portion that is the measurement object will be described. That is, the subordinate strain generating portion is provided so as to be capable of indirectly detecting the strain of the measurement object. However, this does not exclude a general measurement method in which the strain generating portion prepared by the measurement system S is connected in series to a transmission system. In the following description, torque may be used as a derived physical quantity of force (a combined unit including the unit N), but the present invention is also valid even if torque is read as force. The measurement system S includes a detection device 100 and a measurement device 200.

[0015] [Detection Device] The detection device 100 is a device that detects strain of a strain generating part, and calculates the force applied to a measurement target based on the detected strain. The detection device 100 is, for example, a torque sensor that detects the transmission torque of a power transmission shaft SF for transmitting power from a drive source, such as a drive shaft of a vehicle, with the power transmission shaft SF as the measurement target. As described above, it is preferable that the measurement target used as the main strain generating part exhibits linearity in the relationship between torque and strain (see Fig. 3(A)). However, many measurement targets including the power transmission shaft SF exhibit non-linearity that cannot be ignored (see Fig. 3(B)). Furthermore, hysteresis in which the forward path and the return path corresponding to the increase and decrease of torque are separated is also observed (see Fig. 3(C)).

[0016] The detection device 100 includes a gripping part 11, a strain generating part 12, a detection element 13, a detection processing part 14, and a power supply 15, which are accommodated in a housing 10. The housing 10 of the present embodiment is attached so as to cover the power transmission shaft SF. Note that there is no need to perform additional processing on the measurement target for attaching the housing 10.

[0017] (Gripping Part) The gripping part 11 is an element directly fixed to the measurement target. The gripping part 11 of the present embodiment grips the power transmission shaft SF by coming into contact with two positions spaced apart in the axial direction of the power transmission shaft SF.

[0018] (Strain Generating Part) The strain generating part 12 is an element that reflects the measurement target itself or the strain of the measurement target. The strain generating part 12 of the present embodiment is attached to the measurement target via the gripping part 11. More specifically, the strain generating part 12 is a plate body that connects the two gripping parts 11, and is an element whose influence on the strain occurring in the measurement target is negligible.

[0019] (Detection Element) The detection element 13 is an element that detects the strain of the strain generating part 12. The detection element 13 is attached to the strain generating part 12. There is only one detection element 13, but there may be more than one. Since the resistance value of the detection element 13 changes with the strain of the strain generating part 12, the strain can be detected with high sensitivity as a voltage change by forming a Wheatstone bridge circuit. In this embodiment, the strain generating part 12 is attached to the object to be measured via the gripping part 11, and the detection element 13 is provided so as to be able to indirectly detect the strain of the object to be measured. More specifically, the detection element 13 is not directly attached to the power transmission shaft SF of the vehicle, but is attached to the strain generating part 12 which is attached to the power transmission shaft SF.

[0020] Furthermore, the strain generating section 12 and the detection element 13 attached thereto rotate together with the power transmission shaft SF. In other words, the strain generating section 12 is movable relative to the measuring device 200 along with the object being measured, but since the connection between the detection device 100 and the measuring device 200 is wireless, communication is possible.

[0021] (Detection processing unit) The detection processing unit 14 performs the processing necessary for detecting force in the detection device 100. The detection processing unit 14 consists of processing circuits such as a program-operated processor, and storage media such as memory for storing programs and data, but the implementation of the hardware and program can be changed in various ways.

[0022] As shown in Figure 2, the detection processing unit 14 includes a setting unit 141, an input unit 142, a force calculation unit 143, a control unit 144, and a communication unit 145.

[0023] <Settings section> The setting unit 141 sets proportionality constants and limit values ​​as individual parameters representing each basic model in the overall model. The overall model is described below. The overall model is a model in which multiple basic models are connected in parallel. As shown in Figure 4(A), the basic model E is a series connection of a spring element α and a Coulomb friction element β. As shown in Figure 4(B), in the initial stage when the displacement increases, the spring element α behaves linearly with respect to the force based on the spring constant (proportionality constant) as an ideal spring, and when the maximum static friction force (limit value) is exceeded, the Coulomb friction element β begins to slip, and the force remains constant. For example, if the relationship between the strain and torque of the strain generating section 12 follows one basic model E, then in a graph with strain on the horizontal axis and torque on the vertical axis, after a positive strain is generated in the power transmission shaft SF and then removed, the strain generating section 12 behaves as shown in Figure 4(C).

[0024] Thus, beyond the upper limit, the torque does not increase. Once the strain is removed, the spring element α reacts and behaves in a way that releases the stored torque. The torque continues to decrease until it reaches the lower limit, which is zero, as the strain decreases. Physically, the lower limit should be the upper limit with the sign reversed, but for ease of handling and practical convenience, it is conveniently represented as coinciding with the left end of the hysteresis loop.

[0025] As shown in Figure 5, the overall model M applied to this embodiment is a model (Masing model) formed by the parallel combination of multiple basic models E. If the basic models E that constitute this overall model M represent the relationship between strain and torque, then in the initial stage when strain occurs, the torque corresponding to the spring element α of all basic models E increases linearly. However, as the strain further increases, the torque exhibited by the spring element α in each basic model E successively exceeds the limit value of the Coulomb friction element β, and the torque represented by each basic model E becomes constant. Therefore, after the torque exhibited by all spring elements α exceeds the limit value of the Coulomb friction element β, the torque represented by the overall model M no longer changes with increasing strain.

[0026] Furthermore, in a graph with strain on the horizontal axis and torque on the vertical axis, when positive strain occurs, the behavior of multiple basic models E is as shown in Figures 6(A) to (C), and when multiple of these are connected in parallel, the behavior is as shown in Figure 6(D). The dashed line in Figure 6(D) shows the behavior when the positive strain is removed while it is still occurring. In this way, by using the overall model M, it is possible to represent the behavior that mimics the hysteresis loop exhibited by the actual strain generating section 12. Here, for convenience, the behavior of the model when the hysteresis loop is closed by the occurrence and removal of positive strain is shown, but it is similarly possible to represent the hysteresis loop for both positive and negative strains using the overall model M. In this case, the proportionality constant and limit value may be set separately in the force calculation section 143, corresponding to the positive and negative signs of the strain occurring in the strain generating section 12.

[0027] On the other hand, as shown in the example in Figure 8 (vertical axis is strain, horizontal axis is load torque), when a load torque is applied to and then removed from the object being measured, the strain detected by the strain generating section 12 draws a curve that deviates from the dotted line (dotted line) with respect to the regression line (dotted line) with an intercept of zero, in the load increase section (forward path) and the load decrease section (return path).

[0028] By appropriately setting parameters such as the proportionality constant representing the spring element α and the limit value at which the Coulomb friction element β begins to slip, it becomes possible to represent (estimate) the behavior exhibited by the actual measurement target using the overall model M. Such proportionality constants and limit values ​​can be set in advance based on the measured results of the behavior exhibited by the actual measurement target. Furthermore, the proportionality constants and limit values ​​may be set separately in response to increases and decreases in the strain generated in the strain generating section 12.

[0029] The method for setting the proportionality constant and limit value is as follows, for example: (a) Using a torque load device, a predetermined number of load torques are applied sequentially to the power transmission shaft SF, and the detection device 100 measures the strain corresponding to each of the load torques. From the results, the manually calculated parameters are input from the operation unit 250 of the measuring device 200 (described later) and set in the setting unit 141 of the detection device 100.

[0030] (b) A learning mode is provided in the detection device 100 or the measuring device 200, and the operation unit 250 of the measuring device 200 instructs the detection device 100 to apply a predetermined number of load torques to the power transmission shaft SF from the torque load device, and automatically determines that the detected strain is stable, collects multiple torque-strain pairs, calculates a corresponding number (equal number) of parameters for the basic model E from the obtained multiple torque-strain pairs, and stores them in the setting unit 141 of the detection device 100.

[0031] <Input section> The input unit 142 receives a signal corresponding to the strain, i.e., a voltage value, from at least one detection element 13 that detects the strain of the strain generating unit 12. The input unit 142 in this embodiment includes at least an ADC (analog-to-digital converter) and further includes one or more of a bridge circuit, an amplification circuit, an offset adjustment circuit, and a filter circuit, with the ADC being placed after passing through these circuits. In addition, a temperature compensation circuit may be incorporated into the bridge circuit.

[0032] <Force calculation section> The force calculation unit 143 calculates the force based on the calculations of each basic model E based on the strain from the input unit 142 and the parameters set for each basic model E, and estimates the force applied to the strain generating unit 12 by summing these forces. First, the force calculation unit 143 determines the force represented by each basic model E based on the proportionality constant and limit value set for each basic model E in the setting unit 141 and the strain from the input unit 142. Next, it estimates the force applied to the strain generating unit 12 as the overall model M by summing these forces represented by each basic model E. In other words, it obtains a value corresponding to the force applied to the strain generating unit 12 by summing them up.

[0033] The force calculation unit 143 includes a storage unit 143a, a differential strain calculation unit 143b, a differential force calculation unit 143c, a determination unit 143d, a stored force calculation unit 143e, and a summing unit 143f. The storage unit 143a stores strain and force. The stored strain may include the input strain as well as the differential strain described below. The stored force may include the force calculated by each basic model E as well as the differential force described below.

[0034] The differential strain calculation unit 143b calculates the difference between the input strain and the strain stored in the memory unit 143a (the previous strain). Initially, it may read the previous strain stored in the memory unit 143a and resume, or it may reset the previous strain. If the previous strain has been reset, the input strain becomes the differential strain. The differential force calculation unit 143c calculates the differential force value for each basic model E based on the differential strain and proportionality constant.

[0035] The determination unit 143d determines whether the value obtained by adding the difference force value to the force of each basic model E (the force accumulated up to the previous time) stored in the memory unit 143a is true (exceeds the corresponding limit value) or false (does not exceed the limit value). Initially, the unit may read the accumulated force stored in the memory unit 143a and resume, or it may reset the accumulated force. If the accumulated force has been reset, it is determined whether the difference force exceeds the limit value. Note that exceeding the limit value includes cases where the force increases and exceeds the upper limit value, and cases where the force decreases and falls below the lower limit value.

[0036] If the determination unit 143d determines that the force does not exceed the limit value, the accumulated force calculation unit 143e stores the difference in force in the stored force (force accumulated up to the previous time) in the storage unit 143a and stores that value in the storage unit 143a. In other words, it adds the difference in force to the stored force of each basic model E and updates the stored force as the force represented by that basic model E. If the determination unit 143d determines that the force exceeds the limit value, the accumulated force calculation unit 143e adopts the limit value.

[0037] The summing unit 143f estimates the force applied to the strain generating unit 12 by summing the accumulated forces corresponding to each basic model E.

[0038] <Department Head> The control unit 144 controls the input of parameters such as proportionality constants and limit values ​​from the communication unit 145 to the setting unit 141, and the input of parameters from the setting unit 141 to the force calculation unit 143.

[0039] <Communications Department> The communication unit 145 transmits the voltage value representing the force obtained by the force calculation unit 143 to the measuring device 200. The communication unit 145 also receives parameters such as proportionality constants and limit values ​​transmitted from the measuring device 200. In this embodiment, the detection device 100 and the measuring device 200, which are physically separated, are connected by wireless communication to enable communication.

[0040] (power supply) The power supply 15 is a secondary battery that supplies power to the input unit 142, the power calculation unit 143, the setting unit 141, the control unit 144, and the communication unit 145.

[0041] [Measuring device] The measuring device 200 is a device that outputs the force detected by the detection device 100 to an external device, such as a recording device.

[0042] The measuring device 200 consists of processing circuits such as a processor that operates according to a program, and storage media such as memory that stores programs and data, but the implementation of the hardware and program can be changed in various ways. The measuring device 200 has a communication unit 210, an arithmetic unit 220, an input / output unit 230, a display unit 240, an operation unit 250, and a control unit 260.

[0043] (Communications Department) The communication unit 210 communicates information with the detection device 100. For example, the communication unit 210 receives a voltage value representing force transmitted from the detection device 100. The information communicated and transmitted also includes proportionality coefficients and limit values ​​set in the setting unit 141.

[0044] (calculation section) The calculation unit 220 converts the received voltage value into a signal that can be input to an external recording device or the like. At this time, the calculation unit 220 may perform secondary calculations. Specifically, calculations such as multiplication by a constant, multiplication with other measured physical quantities such as rotational speed, and low-pass filtering are envisioned.

[0045] (input / output section) The input / output unit 230 performs input and output of information to and from the outside. For example, the input / output unit 230 outputs the converted and calculated voltage value to an external recording device or the like. In this embodiment, the output signal to the outside is a so-called analog voltage output, but the measuring device 200 may also include a recording device. In that case, the detection device 100 may be configured to include some or all of the elements of the measuring device 200.

[0046] (Display) The display unit 240 is an output unit that displays information on a display screen so that it can be visually recognized by the user. The display unit 240 can display proportionality constants, limit values, and forces calculated by the force calculation unit 143, which are set in the setting unit 141.

[0047] (Operation unit) The control unit 250 is a device for receiving information from the outside. This includes input via external communication. The control unit 250 includes input devices such as keyboards, mice, touch panels, and switches, as well as communication devices such as network adapters.

[0048] (Control Unit) The control unit 260 controls the calculations performed by the calculation unit 220 and the display on the display unit 240 in response to input from the operation unit 250.

[0049] [Processing Procedure] The processing procedure of this embodiment described above will be explained with reference to the figures, as well as to specific mathematical formulas, parameters, graph examples, and flowcharts showing the processing flow of each device.

[0050] (Measurement of strain) First, the strain corresponding to the load torque of the object to be measured is measured in advance using a static torque load device. For example, the device is attached to the power transmission shaft SF, which is the object to be measured, and after applying a load up to the rated torque, the strain corresponding to multiple load torques is detected while returning to no load.

[0051] Figure 7 is a table simulating the strain at 10 measurement points (200, 400, 600, 800, 1000, 800, 600, 400, 200, 0 [N·m]) from load torque 0 [N·m] to rated torque 1000 [N·m], expressed as voltage values ​​[V] corresponding to the output of the input unit 142 (11 points if the initial load torque of 0 [N·m] is counted). Note that the actual output of the input unit 142 is a digital signal, which is the result of ADC conversion of the detected voltage, but for convenience, it is shown here as the analog voltage value before conversion. Also, for ease of understanding, the measurement points in Figure 7 are conveniently spaced equally, but this is just an example, and the spacing between measurement points can be arbitrary. For example, if the hysteresis curve changes significantly, a narrower spacing between measurement points can be used for more accurate correction. Furthermore, although Figure 7 uses the same load torque measurement points for both forward and reverse directions, it is not limited to this.

[0052] In Figure 7, the corrected strain [V] is the value obtained by correcting each detected output strain [V] so that its starting point aligns with the origin. Thus, a circuit or process for performing offset correction of the detected values ​​is also included in the detection device 100. The regression line [V] is a least-squares line created based on the corrected strain [V]. The strain error [V] is the difference between the corrected strain [V] and the regression line [V] at each detection point. Ideally, it is preferable that this strain error [V] is zero.

[0053] Figure 8 is a graph showing the strain against load torque [N·m], with the corrected strain [V] shown as a solid line and the regression line [V] as a dotted line.

[0054] (Identification of proportionality constant) If we let T be the torque applied to the object being measured, and γ be the corresponding strain, then we can first consider that this torque T is distributed to each basic model E as Ti in the following equation (1). JPEG2026170694000002.jpg19143

[0055] Here, if we let ki be the proportionality constant corresponding to the spring constant of each basic model E, and Li be the limit value corresponding to the maximum static friction force, then following Hooke's Law, the strain γ can be expressed as shown in equation (2) below. JPEG2026170694000003.jpg22143 Here, as shown in Figure 8, we consider the case where the defined range is from zero to positive rated torque for convenience, but even when dealing with positive and negative rated torques, the defined range can be similarly expressed as from the lower limit (negative rated torque) to Li. Furthermore, the following explanation can also be adapted to positive and negative rated torques.

[0056] Each of the multiple intervals delimited by the detection points contains one or more basic models E functioning as springs. Therefore, the slope Ai of each interval shown in Figure 9 is obtained by the following equation (3). Note that element numbers outside the range are treated as ki=0. JPEG2026170694000004.jpg20143

[0057] As the torque is gradually increased from the starting point, the basic model E also acts as a Coulomb friction, and each basic model E reaches a limit value one by one, which can be seen as representing the broken line shown in the graph of Figure 9. From the behavior of the basic model E, which becomes constant when it reaches this limit value, the relationship in equation (4) below is clear. Here, each Ai (here, A1 to A5) can be determined from the measurement results, and from this, the proportionality constant ki corresponding to each basic model E can be obtained. JPEG2026170694000005.jpg45143

[0058] In actual applications, the detection device 100 receives strain input from its detection element 13, and its purpose is to determine the corresponding torque. Therefore, when the basic model E is expressed with strain as the input (horizontal axis) and torque as the output (vertical axis), it is given by the following equation (5). JPEG2026170694000006.jpg38143

[0059] (Identifying limit values) The basic model E also requires a limit value corresponding to the point at which the Coulomb friction element β begins to slip. The constant Li representing the limit value is obtained by equation (5) above. However, it is determined from Ti, not the input load torque T at the measurement point (end of each section) during actual measurement. The limit value remains constant outside the range of each section.

[0060] Ki is the proportionality constant corresponding to each interval, and can be calculated from the previously determined Ki as shown in equation (6) below. JPEG2026170694000007.jpg48143

[0061] Figure 10 shows an example of calculating the proportionality constant ki for the outward journey in the simulated data shown in Figure 7, and Figure 11 shows an example of calculating the proportionality constant for the return journey. As described above, each Ai (A'1 to A'5 in Figure 9) for the return journey can be determined from the measurement results, and the proportionality constant ki can be obtained from this. In Figure 11, ki_ave is the average value when the strain increases and decreases.

[0062] The proportionality constant and limit value may be set separately in the force calculation unit 143 in response to increases and decreases in the force applied to the strain generating unit 12.

[0063] (Calculation of torque) Based on the proportionality constant and limit value determined as described above, the process of calculating torque from the strain detected by the detection device 100 will be explained with reference to the flowcharts in Figures 12 and 13. The proportionality constant and limit value are input in advance via the communication unit 145 and set in the setting unit 141.

[0064] As shown in Figure 12, initially, the memory unit 143a is reset (step S101). Then, the strain detected by the detection device 100 is input and acquired by the input unit 142 (step S102). The differential strain calculation unit 143b calculates the difference between the current strain and the previous strain stored in the memory unit 143a as the differential strain (step S103). Initially, since the strain is reset, the current strain becomes the differential strain.

[0065] Next, the force calculation unit 143 calculates the torque of each basic model E using the above equation (4) (step S104). The flow of this torque calculation will be explained with reference to the flowchart in Figure 13. The differential force calculation unit 143c calculates the differential torque based on the differential strain and proportionality constant (step S201). The determination unit 143d determines whether the value obtained by adding the differential torque to the accumulated torque up to the previous time exceeds the limit value (step S202). Note that in step S201 of Figure 13, for convenience only, it shows whether or not it exceeds the upper limit value.

[0066] If it is determined that the limit value is not exceeded (YES in step S202), the accumulated torque calculation unit 143e adds the differential torque to the accumulated torque (step S203), and the storage unit 143a stores the added value as the accumulated torque (step S204). If it is determined that the limit value is exceeded (NO in step S202), the accumulated torque stored in the storage unit 143a is used as the limit value (step S205), and this limit value is stored as the accumulated torque (step S204).

[0067] The above calculation continues until the accumulated torque of all basic model E is calculated (YES in step S105) (step S104). Once the accumulated torque of all basic model E is calculated (NO in step S105), the summing unit 143f calculates the total torque by taking the sum of the accumulated torques of each basic model E, as shown in equation (6) above (step S106). Furthermore, the storage unit 143a stores the strain that was input this time (step S107). Note that the above process may be called and executed many times during repeated measurements, with the processes from S102 to S107 being repeated.

[0068] [effect] (1) The detection device 100 of this embodiment has a setting unit 141 in which a proportionality constant and a limit value are set as individual parameters representing each basic model E, which is a series connection of a spring element α and a Coulomb friction element β, is associated with an overall model M which is a series connection of a basic model E which is a series connection of a spring element α and a Coulomb friction element β, with respect to the relationship between the strain generated in the strain generating part 12 and the force generated, and an input unit 142 which receives a signal from at least one detection element 13 which detects the strain of the strain generating part 12, and a force calculation unit 143 which calculates the force that depends on the calculation of each basic model E based on the strain from the input unit 142 and the parameters set for each basic model E, and estimates the force applied to the strain generating part 12 by summing the forces that depend on the calculation of each basic model E.

[0069] In this way, the force is calculated based on the proportionality constants and limit values ​​representing each basic model E and the detected strain, and by summing these values, the force applied to the strain-generating section 12, including its hysteresis characteristics, can be estimated. Therefore, accurate force calculation is possible regardless of the characteristics of the object being measured. In other words, by considering the nonlinearity and hysteresis characteristics of the object being measured and improving the linearity of the transformation, high-precision measurement can be achieved.

[0070] For example, in a feedback control system based on torque measurement, even if strain is detected in the power transmission shaft SF being measured, if hysteresis characteristics exist, the measured torque output will continue to be emitted when the system is returned to an unloaded state after a load has been applied. Therefore, the control output cannot be stopped unless exceptional processing is performed near zero.

[0071] In this embodiment, the effects of nonlinearity and hysteresis in the measurement target can be suppressed, ensuring accuracy as a torque meter, and thus stabilizing control using the measurement system S. Therefore, in addition to improving the accuracy of the measured values, it is also possible to use inexpensive but poorly performing strain-generating material, thus contributing to a reduction in development and manufacturing costs.

[0072] Generally, for objects consisting of numerous mechanical elements, such as a steering mechanism composed of a handle, steering shaft, and gear mechanism, it is conceivable to associate some kind of model with each contact mechanism between each mechanical element, represent the overall model M that exhibits unique characteristics as a whole configuration by analyzing the force transmitted through multiple mechanical elements from the final output, and then incorporate it as additional control that does not cause discomfort to humans.

[0073] However, the inventors of this invention did not limit themselves to such conventional methods, but came up with a novel idea: to measure the force acting on a single component (for example, a vehicle's power transmission shaft SF) or an integrated structure, they deliberately used an overall model M consisting of multiple basic models E. Moreover, they conceived of a technique that had not existed before, using it not for force analysis and reproduction, but for correcting measured values ​​based on detected values, and achieved the effect of improving the accuracy of measured values.

[0074] (2) The force calculation unit 143 includes a storage unit 143a for storing strain and force, a differential strain calculation unit 143b for calculating the differential strain which is the difference between the input strain and the strain stored in the storage unit 143a, a differential force calculation unit 143c for calculating the differential force value for each basic model E based on the differential strain and the proportionality constant, and a determination of whether the value obtained by adding the differential force value to the force of each basic model E stored in the storage unit 143a exceeds a limit value (true) or does not exceed a limit value (false). The system includes a determination unit 143d that makes a determination, a stored force calculation unit 143e that, if the determination unit 143d determines that the result is false, adds the difference in force to the force of each basic model E stored in the memory unit 143a to update the force stored in the memory unit 143a as the force represented by the basic model, and if the determination unit 143d determines that the result is true, sets the force of each basic model E stored in the memory unit 143a as a limit value, and a summation unit 143f that estimates the total force applied to the strain generating unit 12 by summing the forces corresponding to each basic model E.

[0075] Therefore, even for objects where strain and force do not have a perfectly linear relationship, by considering the accumulation and release of force based on the operating range for each basic model E, it is possible to calculate the force with good overall accuracy. In addition, the previous strain can be stored and used in the next calculation.

[0076] (3) The proportionality constant and limit value are set separately in the force calculation unit 143 in response to increases and decreases in strain generated in the strain generating section 12. Furthermore, the proportionality constant and limit value are set separately in the force calculation unit 143 in response to the sign of the strain generated in the strain generating section 12. This makes it possible to calculate highly accurate forces in the forward and return strokes, which have hysteresis and nonlinearity corresponding to increases and decreases in force.

[0077] For example, by switching between referencing the values ​​during strain increase and decrease, it is possible to represent more realistic characteristics than the point-symmetrical figure like the parallelogram of the basic hysteresis shape shown in Figure 4(C). Alternatively, by switching between positive and negative strain, characteristics that include symmetry with respect to the y-axis can be easily represented. In other words, it is possible to correct not only hysteresis characteristics but also nonlinear characteristics.

[0078] (4) The housing 10 is provided so that it can be attached to the object to be measured without any additional processing. For this reason, even if the object to be measured rotates, such as the power transmission shaft SF of a vehicle, making it difficult to directly attach the detection element 13, or if the strain generating part 12 cannot be connected in series to the power transmission shaft SF, as in this embodiment, it is possible to perform calculations with reduced errors caused by the object to be measured, enabling high-precision torque measurement. Furthermore, even if the strain generating part 12 can be connected in series to the power transmission shaft SF, while expensive materials with excellent linear characteristics in the elastic range are generally used for the strain generating part 12, this method allows for the selection of inexpensive materials with inferior linear characteristics.

[0079] [Differentiation] This embodiment is not limited to the above-described form, and includes the following modifications.

[0080] (1) As shown in the example above, the forward and return paths corresponding to the increase or decrease in torque (force) are often not point-symmetric. In this case, as described above, different proportionality constants and limit values ​​may be selected for the forward and return paths, or they may be calculated separately and combined by taking the average value (see Figure 11 ki_ave). This has the effect of mitigating the data variability due to the instability of the torque load device and the object being measured when acquiring data used to identify the parameters of the basic model E. This instability also includes behavior resulting from the probabilistic and statistical deformation of the material.

[0081] (2) The setting unit 141 may also have a time-dependent coefficient set as an individual parameter representing each basic model E, in addition to the proportionality coefficient and the limit value. In this case, the force calculation unit 143 calculates a time-corrected limit value based on the limit value using a time-dependent coefficient corresponding to the elapsed time since the determination unit 143d of any basic model became true, and uses the time-corrected limit value instead of the limit value, and or calculates a time-corrected proportionality coefficient based on the proportionality coefficient, and uses the time-corrected proportionality coefficient instead of the proportionality coefficient. The time-dependent coefficient can be prepared, for example, as a lookup table or function with the elapsed time since the determination unit 143d of any basic model became true as a parameter. Alternatively, the dwell time of any load may be used as a parameter. This makes it possible to reproduce the creep phenomenon.

[0082] Furthermore, a temperature measurement unit may be provided to detect temperature, and in addition to proportionality coefficients and limit values, a temperature dependency coefficient may be set in the setting unit 141 as individual parameters representing each basic model E. In this case, the force calculation unit 143 calculates a temperature correction limit value based on the limit value according to the difference between the temperature detected by the temperature measurement unit and a fixed reference temperature, and uses the temperature correction limit value instead of the limit value, and / or calculates a temperature correction proportionality coefficient based on the proportionality coefficient, and uses the temperature correction proportionality coefficient instead of the proportionality coefficient. This makes it possible to represent the temperature characteristics of the object being measured. However, before starting the calculation of the difference force in each basic model E, the force calculation unit 143 must determine the equivalent difference strain from the force represented by the basic model E stored in the memory unit 143a and the proportionality coefficient used last time, and recalculate the force represented by the basic model when the applicable correction proportionality coefficient and / or correction limit value are used.

[0083] (3) In the above embodiment, the strain of the object to be measured was indirectly detected by attaching the strain generating part 12 to which the detection element 13 is attached to the object to be measured. However, it may also be applied to a detection device 100 that directly attaches the detection element 13 to the object to be measured to detect the strain. In this case, the strain generating part 12 becomes the object to be measured itself, and calculations can be performed with reduced errors caused by the characteristics of the object to be measured.

[0084] (4) The measurement target is not limited to the vehicle's power transmission shaft SF, but is applicable to any member or structure. It is not limited to a single member, and structures in which multiple members are fixedly or movably connected may also be measured. Furthermore, although it is suitable for measuring movable objects such as the vehicle's power transmission shaft SF, it is not limited to this, and stationary members may also be measured.

[0085] (5) The connection between the detection device 100 and the measuring device 200 is not limited to wireless, but may be wired, or may be a connection via a communication network, whether wired or wireless. Communication includes optical communication. In the above embodiment, the housing 10 housed the detection element 13 along with the setting unit 141, input unit 142, and force calculation unit 143. However, the housing 10 may house only some of the components, namely the setting unit 141, input unit 142, and force calculation unit 143. Furthermore, components outside the housing 10 may be provided in the measuring device 200. In other words, the measuring device 200 may have some of the functions of the detection device 100. For example, the force calculation unit 143 may be provided in the measuring device 200. In this way, even if some components are provided in the housing 10 and other components are provided outside the housing 10, the whole can still be considered as the detection device 100. The components housed in the housing 10 and the components outside the housing 10 may be connected by wireless or wired communication, and may be connected via a communication network, whether wired or wireless. For example, a measuring device 200, which includes components outside the housing 10 of the detection device 100 and an input / output unit 230 for external devices, may be connected to the components inside the housing 10 of the detection device 100 via wireless communication.

[0086] (6) Although the above-described detection device 100, measuring device 200, and measuring system S were explained using an example of torque measurement, they are not limited to this and can be broadly applied as force sensors for measuring the force applied to the object being measured.

[0087] [Other embodiments] Although embodiments and modifications of the present invention have been described above, these embodiments and modifications are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments described above can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the invention described in the claims. [Explanation of symbols]

[0088] 10 cabinets 11 Gripping part 12 Strain part 13 detection elements 14 Detection Processing Unit 15 Power supply 100 detection device 141 Settings Section 142 Input section 143 Force calculation section 143a Storage section 143b Difference Strain Calculation Unit 143c Differential force calculation section 143d Judgment section 143e Storage Capacity Calculation Unit 143f Totalization section 144 Control Unit 145 Communications Department 200 measuring devices 210 Communications Department 220 Arithmetic section 230 Input / output section 240 Display section 250 Operation section 260 Control Unit E Basic Model M Overall Model S Measurement System SF Power Transmission Shaft α spring element β Coulomb friction element

Claims

1. The relationship between strain and force occurring in the strain-generating area is represented by an overall model consisting of multiple basic models, each a series connection of a spring element and a Coulomb friction element, connected in parallel. A setting section is used to define the relationship between strain and force, and proportionality coefficients and limit values ​​are set as individual parameters representing each basic model. An input unit that receives a signal from at least one detection element that detects the strain in the strain-generating portion, A force calculation unit calculates the force based on the calculations of each basic model based on the strain from the input unit and the parameters set for each basic model, and estimates the force applied to the strain generating unit by summing the forces based on the calculations of each basic model. A detection device characterized by having the following features.

2. The force calculation unit, A memory unit that stores strain and force, A differential strain calculation unit that calculates the difference in strain between the input strain and the strain stored in the memory unit, A difference force calculation unit that calculates the difference force value in each basic model based on the difference strain and the proportionality constant of each basic model, A determination unit determines whether the value obtained by adding the difference force value to the force of each basic model stored in the memory unit is true (exceeding the limit value) or false (not exceeding the limit value), If the determination unit determines that the result is false, it adds the difference in force to the force of each basic model stored in the memory unit and updates the force stored in the memory unit as the force represented by that basic model. If it determines that the result is true, it sets the force of each basic model stored in the memory unit as a limit value. A summing unit estimates the total force applied to the strain-generating part by summing the forces corresponding to each basic model, The detection device according to claim 1, characterized by having the following features.

3. The detection device according to claim 1, characterized in that the proportionality constant and the limit value are set separately in the force calculation unit in response to increases and decreases in the strain occurring in the strain generating portion.

4. The detection device according to claim 1, characterized in that the proportionality constant and the limit value are set separately in the force calculation unit, corresponding to the sign of the strain occurring in the strain generating part.

5. A setting unit in which the proportionality coefficient, the limit value, and the time-dependent coefficient are set as individual parameters representing each of the above basic models, A force calculation unit that calculates a time-corrected limit value based on the limit value according to the elapsed time since the determination unit's determination became true and the time-dependent coefficient, and uses the time-corrected limit value instead of the limit value, and / or calculates a time-corrected proportional coefficient based on the proportional coefficient, and uses the time-corrected proportional coefficient instead of the proportional coefficient, The detection device according to claim 2, characterized by having the following features.

6. A temperature measuring unit that detects temperature, A setting unit in which the proportionality coefficient, the limit value, and the temperature dependence coefficient are set as individual parameters representing each of the above basic models, The force calculation unit calculates a temperature correction limit value based on the limit value according to the difference between the temperature detected by the temperature measurement unit and a fixed reference temperature, and uses the temperature correction limit value instead of the limit value, and / or calculates a temperature correction proportional coefficient based on the proportional coefficient, and uses the temperature correction proportional coefficient instead of the proportional coefficient. The detection device according to claim 2, characterized by having the following features.

7. It has a housing that accommodates the detection element, The housing contains all or part of the setting unit, the input unit, and the force calculation unit. The detection device according to claim 1, characterized in that the housing is provided so as to be attached to the object to be measured without any additional processing.

8. It has a housing that accommodates the detection element, The housing contains the setting unit, the input unit, and a part of the force calculation unit. The detection device according to claim 1, characterized in that the components housed in the housing and the components outside the housing are connected via wireless communication.

9. The detection device according to claim 1, characterized in that the strain generating portion is provided in a manner that allows for the indirect detection of the strain of the object to be measured.

10. A measurement system characterized in that a measuring device, which includes components outside the housing of the detection device and input / output units for an external device, is connected via wireless communication to the components inside the housing of the detection device according to claim 8.

11. A measurement system characterized in that a measuring device having an input / output unit for an external device is connected to the detection device according to claim 1 via wireless communication.

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