BG67585B1 - Device for measuring forces and torques - Google Patents

Abstract

The device for measuring forces and torques according to the present invention consists of a first element (1) and a second element (2) accommodated oppositely to each other, and four legs (3, 4, 5 and 6) which connect the two elements (1 and 2) and are distributed evenly between the two elements (1 and 2) along their periphery. Four brackets (7, 8, 9 and 10) are arranged evenly along the periphery to the first element (1). Four other brackets (11, 12, 13 and 14) are arranged evenly along the periphery of the second element and are directed towards the brackets (7, 8, 9 and 10) of the first element (1) without coming into contact with these brackets. The space between bracket (7) and its corresponding bracket (11) accommodates a transverse MEMS sensor (15) and a longitudinal MEMS sensor (16). The space between bracket (8) and its corresponding bracket (12) accommodates a transverse MEMS sensor (17) and a longitudinal MEMS sensor (18). The space between bracket (9) and its corresponding bracket (13) accommodates a transverse MEMS sensor (19) and a longitudinal MEMS sensor (20). The space between bracket (10) and its corresponding bracket (14) accommodates a transverse MEMS sensor (21) and a longitudinal MEMS sensor (22). One end of each transverse and each longitudinal MEMS sensor is rigidly attached to the bracket of element (1), while its other end is rigidly attached to the bracket of element (2). Said device for measuring forces and torques would be applied for measuring the loads on the tools of metalworking machines or on the executive parts of robots, in processes such as metal cutting and machining, in assembly processes as well as in human training and interaction with collaborative robots and exoskeletons.

Description

Field of technique

The present invention relates to a device for measuring forces and torques applied to an executive unit of a robot or a metal-cutting machine. The device will find application for measuring forces and moments in technological processes such as assembly, cutting and processing of metals, etc. Also, the device could find application in exoskeletons and collaborative robots in learning and human interaction.

Prior art

A six-axis force sensor [1] is known, consisting of two elements located in opposite positions to each other and four legs evenly spaced between the two elements along their periphery, which connect the two elements and which deform elastically as a result of applying a load to one of the two elements, thereby allowing the measurement of forces and moments acting on one of the two elements based on the detected deformations generated in the legs. In this, each leg is shaped as a T-leg, consisting of a transverse beam extending in a circumferential direction connected at both ends to one member and a vertical beam perpendicular to the transverse beam connected to the other member. Leg deformations are detected by a first uniaxial strain gauge and a second uniaxial strain gauge, the first uniaxial strain gauge being attached to the surface of the cross beam facing the side opposite the vertical beam or to the surface of the cross beam facing the vertical beam so that it can to detect strain generated in the cross beam in the longitudinal direction. The second uniaxial strain gauge is attached to a side surface of a vertical beam so that it can detect strain generated in the vertical beam in a circumferential direction.

A disadvantage of the Six-Axis Force Sensor is that it is sensitive to noise due to the rigid mechanical construction with small deformations being sensed by strain gauges. Also, to accurately measure the deformations, it is necessary to attach the strain gauge at a certain point where the deformations are most pronounced.

Technical essence of the invention

The task of the invention is to create a device for measuring forces and torques, which is insensitive to noise when reading the forces and moments, has a simplified construction, easy to manufacture.

The task is solved with a device for measuring forces and torques, consisting of two elements located in opposite positions to each other and four legs, located evenly between the two elements along their periphery, which connect the two elements and which deform elastically as a result of applying a load to one of the two elements. To the first element, four consoles are evenly spaced along its periphery, which are directed towards the other element. To the second element, four other consoles are evenly spaced along its periphery, which are directed to the consoles of the first element without touching them.

The first pair of matching brackets are located midway between the first leg and the second leg. The second pair of matching brackets are located midway between the second leg and the third leg. The third pair of matching brackets are located midway between the third leg and the fourth leg. The fourth pair of matching brackets are located midway between the fourth leg and the first leg.

A transverse MEMS (microelectromechanical system) sensor and a longitudinal MEMS sensor are located between each of their respective cantilevers, one end of each sensor being fixedly attached to the cantilever of the first element and the other end of each sensor being fixedly attached to the cantilever of the second element.

The transverse MEMS sensor produces a signal proportional to the positional deviation created by the applied load of the first element relative to the second element in the transverse /tangential/ direction. The longitudinal MEMS sensor produces a signal proportional to the positional deviation created by the applied load of the first element relative to the second element in the longitudinal direction /along the axis of the device/. The applied load is a force or moment that causes elastic deformations in the four legs and deflection of the first member relative to the second, causing each cantilever of the first member to deflect relative to the corresponding cantilever of the second member. Movements in the longitudinal or transverse direction between the respective brackets are recorded by the MEMS sensors located on them, as a change in the output voltage, proportional to the movement in the longitudinal or transverse direction.

The advantage of the device for measuring forces and torques is its insensitivity to noise, since the sensors are mounted on the rigid elements and are independent of the elastic legs and the distribution of stresses and deformations on them. The device has a simplified monolithic construction, easy to fabricate by cutting or EDM.

Explanation of the attached figures

The invention is better explained by the following attached figures, where:

Figure 1 is a general view from one side of the device for measuring forces and moments;

figure 2 is a general view from the other side of the device for measuring forces and moments;

figure 3 is a longitudinal section of the device for measuring forces and moments.

Example of implementation of the invention

The invention is better explained by the following example.

The device for measuring forces and torques consists of two elements 1 and 2 located in an opposite position to each other and four legs 3, 4, 5 and 6, located evenly between the two elements 1 and 2 along their periphery, which connect the two elements 1 and 2. To the first element 1, four consoles 7, 8, 9 and 10 are uniformly located along its periphery, which are directed to the second element 2. To the second element 2, four other consoles 11, 12, 13 and 14 are uniformly located along its periphery, directed to the brackets 7, 8, 9 and 10 of the first element 1, without touching them. The first console 7 of the first element 1 and the first console 11 of the second element 2 are located midway between the first leg 3 and the second leg 4. The second console 8 of the first element 1 and the second console 12 of the second element 2 are located midway between the second leg 4 and the third leg 5. The third bracket 9 of the first element 1 and the third bracket 13 of the second element 2 are located halfway between the third leg 5 and the fourth leg 6. The fourth bracket 10 of the first element 1 and the fourth bracket 14 of the second element 2 are located midway between the fourth leg 6 and the first leg 3. A first transverse MEMS sensor 15 and a first longitudinal MEMS sensor 16 are attached at one end to the first bracket 7 of the first element 1 and at the other end to the first bracket 11 of the second element 2. A second transverse MEMS sensor 17 and a second longitudinal MEMS sensor 18 are attached at one end to the second bracket 8 of the first element 1 and at the other end to the second bracket 12 of the second element 2. A third transverse MEMS sensor 19 and a third longitudinal MEMS sensor 20 are attached at one end on the third bracket 9 of the first element 1 and at the other end on the third bracket 13 of the second element 2. A fourth transverse MEMS sensor 21 and a fourth longitudinal MEMS sensor 22 are attached at one end on the fourth console 10 of the first element 1, and at its other end on the fourth console 14 of the second element 2.

Use of the invention

The invention can be used in the following way.

The device is placed on a robot or metal-cutting machine, and the second element 2 is fixedly fixed to the robot or machine with bolts. A gripper of the robot or the tool of a metal-cutting machine is attached to the first element 1 with the help of bolts.

When an arbitrary spatial load is applied to the gripper or tool, this load is transmitted to the first element 1, resulting in elastic deformations in the four legs 3, 4, 5 and 6 that connect element 1 to element 2. As a result of this causes element 1 to deflect relative to element 2, causing all cantilevers 7, 8, 9, and 10 of element 1 to deflect relative to the corresponding cantilevers 11, 12, 13, and 14 of element 2. The displacements of the corresponding cantilevers are transmitted to the two opposite ends of the MEMS sensors located on them.

Transverse MEMS sensors 15, 17, 19, and 21 have a sensitive portion that is up to 3 mm wide and 12 pm to 270 pm thick. This part is an elastic silicon wafer with suitable geometry, including four piezo resistors connected in a bridge circuit. The deformation of the silicon wafer leads to a proportional change in the output voltage proportional to the displacement in the transverse direction.

The longitudinal MEMS sensors 16, 18, 20, and 22 have a sensitive portion that is up to 3 mm wide and 12 pm to 270 pm thick. This part is an elastic silicon wafer with another suitable geometry including four piezo resistors connected in a bridge circuit. The deformation of the silicon wafer leads to a proportional change in the output voltage proportional to the displacement in the longitudinal direction.

Thus, from the eight MEMS sensors 15, 16, 17, 18, 19, 20, 21 and 22, eight voltages v1, v2, v3, v4, v5, v6, v7, v8 are read, which can be combined into the vector:

V = [v1, v2, v3, v4, v5, v6, v7, v8] ^T

These stresses are determined by transverse and longitudinal displacements generated by various forces and moments.

In the most general case, the spatial load of element 1 can be represented by three forces Fx, Fy, Fz and three moments: Mx, Mu, Mz along the axes of the Cartesian coordinate system OXYZ, the center of which O is located in the center of the device and the X-axis coincides with the device axis. The load can be represented by a vector F:

F = [Fx, Fy, Fz, Mx, My, Μζ] ^τ

The relationship between the power loads F and the received voltages from the sensors V can be found by correlation [1] using the equation

F=CV (1), where C is the calibration matrix:

The calibration matrix C can be obtained experimentally by applying different loads F and making multiple recordings of the voltages V of the eight MEMS sensors. Once the relationships between F and V are known, one can use equation (1) and the method of least squares as suggested in [1] to obtain the matrix C. Once the calibration matrix is known, one can measure the six components of spatial forces and moments by taking the readings of the eight MEMS sensors 15, 16, 17, 18, 19, 20, 21 and 22 and using equation (1).

Claims (1)

A device for measuring forces and torques consisting of two elements (1 and 2) located in opposite positions to each other and four legs (3, 4, 5 and 6) connecting the two elements (1 and 2) and located evenly between the two elements (1 and 2) along their periphery, characterized by the fact that to the first element (1) four consoles (7, 8, 9 and 10) are evenly located along its periphery and to the second element (2) are evenly spaced four other brackets (11, 12, 13 and 14) along its periphery, directed to the brackets (7, 8, 9 and 10) of the first element (1) without touching them, as the first bracket (7) of the first element (1) and the first bracket (11) of the second element (2) are located midway between the first leg (3) and the second leg (4), the second bracket (8) of the first element (1) and the second bracket (12) of the second element (2) are located in the middle between the second leg (4) and the third leg (5), the third console (9) of the first element (1) and the third console (13) of the second element (2) are located in the middle between the third leg (5) and the fourth leg (6), the fourth bracket (10) of the first element (1) and the fourth bracket (14) of the second element (2) are located midway between the fourth leg (6) and the first leg ( 3), also a first transverse MEMS sensor (15) and a first longitudinal MEMS sensor (16) are attached at one end on the first bracket (7) of the first element (1) and at the other end on the first bracket (11) of the second element (2), also a second transverse MEMS sensor (17) and a second longitudinal MEMS sensor (18) are attached at one end on the second bracket (8) of the first element (1) and at the other end on the second bracket (12) of the second element (2), also a third transverse MEMS sensor (19) and a third longitudinal MEMS sensor (20) are attached at one end on the third bracket (9) of the first element (1) and at the other its end on the third bracket (13) of the second element (2), also a fourth transverse MEMS sensor (21) and a fourth longitudinal MEMS sensor (22) are attached at one end on the fourth bracket (10) of the first element (1) , and at its other end on the fourth bracket (14) of the second element (2)