RU2637721C1 - Method for graduating multicomponent force and torque sensors and device for its implementation - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: invention relates to graduation of the force/torque sensors (FTS) with a number of components from one to six. The goal is achieved due to the fact that FTS which mounting flange is connected with cables (at the ends of which there are loads of known mass) through intermediate components (stiffness which is chosen in such a way as to exclude the impact of tensile force on the mounting flange of FTS) moves behind its sensitive flange by the drive system (DS), providing spatial displacement. Thus, the angles of cable inclination and the force or torque acting on the FTS change. The angles of cable inclination are recorded by high-precision angle sensors. In order to tension the cables a drive system can be used instead of loads to ensure the creation of a stable tension force for the cables.

EFFECT: calibration automation of force/torque sensors due to the use of BBS and ensuring the universality of the device, which allows to specify a load in the form of segregates of the main force and torque vector and in all allowable load range of the graduated force/torque sensor, as well as to create complex loading.

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Description

The invention relates to the field of testing and calibration of devices for measuring forces and moments, and in particular to the field of calibration of torque sensors (DSM) with the number of components from one to six.

There is a known method for calibrating a DSM and a bench for its implementation, described in patent CN 103604561 B. The forces and moments are applied to the DSM by means of cables stretched through the pulleys, at the ends of which loads are attached. The stand allows you to load the DSM with the selected components of the main vector of forces and moments F _X , F _Y , F _Z , M _X , M _Y , M _Z , and also create a complex load, which is a superposition of the selected components. The disadvantage of the proposed method is the need for manual replacement of goods during the calibration process, which leads to an increase in the calibration time.

A known bench for calibration of the DSM is described in CN patent No. 103196629 A. The DSM is mounted on a table that moves by means of drives consisting of an engine, a gearbox and a ball screw so as to ensure that the necessary loads are applied to the DSM by means of a pressure head into which one-component force sensor. The design allows you to automate the process of graduation DSM. The disadvantage of this stand is the inability to create dedicated components of the main moment M _X , M _Y , M _Z.

Known bench for the calibration of DSM, protected by patent DE 102006004283 A1. The principle of operation of the stand is that the DSM with the test load fixed to it rotates sequentially with the manipulator relative to the horizontal axis of the manipulator 360 ° in increments of 10 ° or 5 °. In addition, at each such step, the DSM manipulator rotates with the test load fixed on it relative to the longitudinal axis of the manipulator output link with a certain step. At the same time, at each step, the DSM is affected by the gravity of a load of known mass and moments of this force, and signals are taken from the DSM at each step, which allows its automated calibration. The disadvantages of this method are reflected in the following considerations. To create a selected component of the main force vector in the entire range of DSM loading, it is necessary either to manually change the load of a known mass, which increases the calibration time, or to close the kinematic scheme of the manipulator and create the selected components of the main vector due to the influence of the output link of the manipulator on the support. In this case, the output flange of the manipulator should be equipped with an additional DSM. This is necessary to prevent damage to the graduated DSM. As an additional DSM, a calibration DSM of the same load range as a graduated DSM can serve. However, in this case, the accuracy of the calibration of the DSM is limited by the accuracy of the calibration DSM, which may be insufficient for high-precision calibration of the DSM. As for the separation of the components of the main moment (the creation of a pair of forces) in the entire range of loading, in such a design it can be provided only due to the influence of the output link of the manipulator on the support when the kinematic circuit of the manipulator is closed.

The closest in technical essence to the claimed invention are a method for calibrating the DSM and a stand for its implementation, protected by patent CN 101936797 A and selected as a prototype. With this calibration method, the following operations are performed: 1. The DSM is mounted on the adjusting table so that the DSM mounting flange is rigidly fixed to the adjusting table, and the sensitive DSM flange is rigidly connected to the adapter, in the central hole of which the cable end is fixed; the free end of the cable is pulled through the lower pulley located on the axis of the fixed rack, so that the cable is parallel to the plane of the adapter.

2. A load of known mass is attached to the free end of the cable, thereby creating the selected component of the main vector F _X. The force F _{X is} calculated as F _X = ƒ, where ƒ is the weight of a load of known mass. The adjustment table is rotated 90 °, thereby creating the selected component F _Y = ƒ.

3. A load of known mass is removed, the free end of the cable is removed from the lower pulley and passed through the upper pulley, then a load of known mass is attached to the free end of the pulley, so the cable is located at an angle θ to the plane of the adapter; component F _{Z is} calculated as F _z = -ƒ⋅sinθ.

4. A load of known mass is removed, the fixed end of the cable is removed from the central hole of the adapter and this end of the cable is inserted into the hole of the adapter located at a distance b from the central hole in the positive direction of the Y-axis of the DSM, component M _{X is} calculated as

,

,

where B is the projection of the distance between the point of contact of the pulley with the cable and the Central hole of the adapter on the plane of the adapter.

5. A load of known mass is removed, the adjusting table is rotated 90 °, the fixed end of the cable is removed from the adapter hole and this cable end is inserted into the adapter hole located at a distance b from the central hole in the negative direction of the X-axis of the DSM, component M _{Y is} calculated as

.

.

6. The load of known mass is removed, the free end of the cable is removed from the lower pulley and passed through the upper pulley, the fixed end of the cable is removed from the adapter hole and inserted into the central hole, a load of known mass is attached to the free end of the cable, component M _{Z is} determined:

.

.

A device for implementing this calibration method is a fixed plate on which an adjustment table and two racks are located. A DSM is mounted on the adjustment table so that its mounting flange is rigidly fixed, and its sensitive flange is rigidly connected to an adapter having five holes for fixing the cable (one central and four at a distance b from the central in the axes of the coordinate system of the DSM). Between two racks there are two axes: lower and upper, on which pulleys are fixed: lower and upper, respectively. The lower pulley is located so that the cable, one end fixed in any of the holes of the adapter, and the other free end passed through the lower pulley, is parallel to the plane of the adapter. The upper pulley is located so that the cable, one end fixed in any of the holes of the adapter, and the other free end passed through the upper pulley, occupies an inclined position relative to the plane of the adapter with an angle of inclination θ.

The advantages of the described method include the mathematical dependence of the components of the main vector of forces and moments on the weight of the load. Thus, by changing the weight of a load of known mass, it is possible to load the DSM in its entire load range. Also, the components of the main vector of forces and moments mathematically depend on the angle θ, which can be removed, for example, from an angle sensor.

The disadvantages of the described method include the lack of calibration automation, since manual loading of the test load is required for loading the DSM in its entire operating range, which affects the time of the calibration process. The disadvantages of the stand also include the lack of versatility of the stand, since it is not provided for the selection of components F _Z , M _X , M _Y , M _Z.

The aim of the present invention is to provide a method for automated and universal calibration of VHI and a device that implements it. The device should allow the load components (forces F _X , F _Y , F _Z , and moments M _X , M _Y , M _Z ) and complex loads representing a superposition of forces and moments throughout load range of a specific DSM.

This goal is achieved due to the fact that in the proposed method of calibrating the DSM, the mounting flange of which is connected to four cables (at the ends of which loads of known mass are attached) through intermediate parts (the rigidity of which is selected so as to exclude the effect of tensile force on the mounting flange of the DSM) moves behind its sensitive flange with a drive system (PS) that provides spatial displacements, for example, with a six-stage industrial manipulator. Thereby, the tilt angles of the cables and the force or moment acting on the DSM are changed. Cable tilt angles are recorded by high-precision angle sensors. Thus, the accuracy of the DSM calibration is limited by the accuracy of the angle sensors used.

In addition to the clean selected component when moving the DSM strictly according to the direction of the coordinate axis of the DSM, it is possible to create a complex load on the DSM, for example, first by translating (rotating) it, and then, in the new position of the DSM in space, by setting another movement to determine the second component the main vector of forces and moments.

PS allows you to move the DSM in six degrees of freedom in space (three linear and three angular). Thus, when moving the DSM using the PS from the position corresponding to the zero value of the selected load component to the position corresponding to the maximum value, the calibration process is automated. In addition, the versatility of the stand is achieved due to the possibility of creating both selected components of the main vector of forces and moments, and complex loading of the DSM.

The technical result of the claimed invention is

1. Automation of the DSM calibration process through the use of PS.

2. The universality of the device, which allows you to set the load in the form of the selected components of the main vector of forces and moments in the entire allowable load range of the calibrated DSM, as well as create complex loading.

In FIG. 1a, FIG. 1b, FIG. 1c shows a calibration stand.

FIG. 1a is a general view;

FIG. 1b - adapter flange;

FIG. 1c - fixing the sensor.

In FIG. 2 shows the appearance of the DSM.

In FIG. 3a, FIG. 3b, FIG. 3c, FIG. 3d, FIG. 3d, FIG. 3e shows a diagram of the application of forces and moments.

Description of the device for graduation of the DSM (Fig. 1a, b, c).

The calibration stand consists of a frame 1, on which four pulleys 2 are installed, having freedom of angular movement relative to their vertical axes. Four ropes are threaded through pulleys 2. The design provides precise adjustment of the position of the pulleys 2 relative to the frame 1. The free ends of the ropes 3 are attached to loads of known mass 4, the fixed ends of the ropes 3 are attached to two-stage hinges 5. Angle sensors 6 are built into the two-stage hinges 5. Two-stage hinges 5 are connected to the adapter flange 7. On the adapter flange 7, a mounting flange DSM 8 is attached, which is attached to the outlet flange 9 of the PS 10 with its sensitive flange.

In FIG. 2 shows the appearance of the DSM. DSM consists of a mounting flange 11 and a sensitive flange 12.

Description of the calibration method

The proposed calibration method is as follows.

1. The DSM with a sensitive flange is fixed on the output flange of the PS, while the adapter flange is fixed on the mounting flange of the DSM. On the transitional flange, on each side, one two-stage hinge is fixed (a total of four two-stage hinges).

2. Substations are moved to a pre-calculated initial position, such that each of the cables fixed at one of their ends to the output links of two-stage hinges (four cables in total), and the others, free, pulled through pulleys mounted on a fixed frame, is parallel to the plane of the mounting flange DSM, two cables parallel to the X axis of the _{mouth of the} mounting flange of the DSM and two cables parallel to the Y _{axis of the} mounting flange of the DSM. At the free ends of the cables, identical loads of known mass are fixed.

3. PS in accordance with a given program, in automatic mode, performs step-by-step movement and orientation of the DSM. To set the selected component of the main vector of forces and moments, the SHS displaces the DSM along one of the axes of the coordinate system O _yst X _yst Y _yst Z _{yst of the} mounting flange of the DSM, or rotates the DSM relative to one of the axes of the coordinate system O _mouth X _mouth Y _mouth Z _{mouth of the} mounting DSM flange . The coordinate system OXYZ DSM coincides with the coordinate system O _yst X _yst Y _yst Z _{yst of the} mounting flange of the DSM. The DSM measurement center is the origin of the OXYZ DSM coordinate system.

4. Assignment of the component F _Z (Fig. 3a). To create the force + F _{Z, the} PS moves the DSM mounted on the adapter flange in the negative direction of the Z axis. To create the force -F _{Z, the} PS moves the DSM in the positive direction of the Z axis.

The force F _{z is} calculated by the formula:

F _Z = (sinγ ₁ + sinγ ₂ + sinγ ₃ + sinγ ₄ ) ⋅T, where γ ₁ , γ ₂ , γ ₃ , γ ₄ are the angles of deviation of the cables from the plane of the mounting flange of the DSM, T is the cable tension force created by the weight of the goods known mass. The values of the angles γ ₁ , γ ₂ , γ ₃ , γ ₄ are taken from the angle sensors.

5. The task load M _X (M _Y ) (Fig. 3B, C). To create the moment + M _X (+ M _Y ), the PS rotates the DSM mounted on the adapter flange so that the moment vector coincides in the direction with the positive direction of the X (Y) axis. To create the moment -M _X (-M _Y ), the PS rotates the DSM so that the moment vector coincides in the direction with the negative direction of the X (Y) axis.

The moment M _{X is} calculated by the formula: M _X = (sinγ ₂ + sinγ ₄ ) ⋅k⋅Т, where k is the projection of the distance between the center of measurement of the DSM and the center of the axis of rotation of the two-stage hinge on the plane of the mounting flange of the DSM, counted in the direction of the X axis (Y ) DSM coordinate systems. The values of the angles, γ ₂ , γ ₄ are taken from the angle sensors. The moment M _{Y is} calculated by the formula: M _Y = (sinγ ₁ + sinγ ₃ ) ⋅k⋅Т. The values of the angles, γ ₁ , γ ₃ are taken from the angle sensors.

6. The job load F _X (F _Y ) (Fig. 3d, d). To create the force + F _X (+ F _Y ), the SHPS moves the JSM mounted on the adapter flange in the negative direction of the X (Y) axis. To create the force -F _X (-F _Y ), the PS moves the JSM in the positive direction of the X (Y) axis. The force F _{X is} calculated by the formula: F _X = (sinθ ₂ + sinθ ₄ ) ⋅Т, where θ ₂ , θ ₄ are the angles of deviation of the cables from the Y axis of the DSM coordinate system. The values of the angles θ ₂ , θ ₄ are taken from the angle sensors. The force F _{Y is} calculated by the formula: F _Y = {sinθ ₁ + sinθ ₃ ) ⋅Т, where θ ₁ , θ _З are the angles of deviation of the cables from the X axis of the DSM coordinate system. The values of the angles θ ₁ , θ ₃ are taken from the angle sensors.

7. The load setting M _Z (Fig. 3E). To create a moment + M _{Z, the} PS rotates the DSM mounted on the adapter flange so that the moment vector coincides in the direction with the positive direction of the Z axis. To create the moment -M _{Z, the} PS rotates the DSM so that the moment vector coincides in the direction with the negative direction of the Z axis The moment M _{Z is} calculated by the formula M _Z = Qsinθ ₁ + sinθ ₂ + sinθ ₃ + sinθ ₄ ) ⋅k⋅Т.

The values of the angles θ ₁ , θ ₂ , θ ₃ , θ ₄ are taken from the angle sensors.

Complex load assignment

The complex load on the DSM is given by the PS as a superposition of the positions creating the components of the forces F _X , F _Y , F _Z and moments M _X , M _Y , M _Z. In the general case, the vector of forces and moments

can be imagined as

It is possible to build the described calibration device with the number of cables different from four, but it must be at least three.

Instead of loads of known mass, a drive system (pneumatic, electric, hydraulic) can be used to tension the cables, which ensures the creation of a stable tension force of the cables.

Claims (3)

1. The method of calibrating force-torque sensors, which consists in the fact that the force-torque sensor is loaded with a cable tension force created by the weight of a load of known mass attached to the free end of the cable, the cable tension force vector changing due to the cable tilting to the plane of the mounting flange of the torque sensor by a certain angle, characterized in that the load value is set by changing the tilt angles of the cables when moving the torque sensor in space in one or more coordinates; carry out the selection of components F _X , F _Y and F _{Z of the} main vector F along three mutually perpendicular axes of the coordinate system of the torque sensor X, Y, Z by shifting the force sensor by a fixed value along the corresponding axis, and to set the component of the main moment M: M _X , M _Y and M _Z along the three mutually perpendicular axes X, Y, Z coordinate system of the torque sensor rotate the torque sensor at a given angle; the complex loading of the torque sensor is ensured by the superposition of forces and moments. 2. A device for calibrating torque sensors, containing a block-cable system, in which the cables are pulled by the weight of cargo of known mass, characterized in that a drive system is used to change the tilt angle of the cables, providing spatial movement, rigidly connected with the sensitive flange of the torque sensor, mounting flange which through an adapter flange with two-stage hinges placed on it with integrated angle sensors is connected to cables passed through fixed base pulleys having freedom of angular movement relative to their vertical axes. 3. The device according to claim 2, characterized in that a drive system is used to create a stable cable tension force.

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