Six-dimensional force sensor applying annular flexible spherical hinge

Abstract

According to the technical scheme, the six-dimensional force sensor comprises an upper platform, a lower platform, force measuring branches, the annular flexible spherical hinges and three stand columns, the upper platform and the lower platform are of the same structure, and the upper platform and the lower platform are arranged in a parallel state and are provided with the three stand columns; the upper platform, the lower platform and the stand column are provided with annular flexible spherical hinges, and strain gauges are arranged on the force measuring branches. The number of the force measuring branches is six, every three force measuring branches form a group, and the force measuring branches are horizontally and vertically arranged with the group as the unit. The two ends of the horizontally-arranged force measuring branch are connected with the annular flexible spherical hinges on the stand columns, and the vertically-arranged force measuring branch is connected with the annular flexible spherical hinges of the upper platform and the lower platform. The cylindrical flexible spherical hinge has the advantages that parts are easy to machine, the manufacturing cost is reduced, the application range is wide, the problem that a traditional cylindrical flexible spherical hinge is difficult to machine and install is solved, and the measurement precision of the sensor is improved.

Description

Technical Field

[0001] The invention relates to the field of processing and manufacturing of force sensors, and in particular to a six-dimensional force sensor using an annular flexible ball joint. Background Art

[0002] Six-dimensional force sensors are sensors for measuring spatial force information. They can not only measure single-dimensional force information, but also measure force and torque in three-dimensional space, so they are widely used in the wrist, base and other parts of robots. They play a vital role in enabling robots to complete complex and delicate tasks and achieve flexible and intelligent operations. Especially in operations such as grasping and assembly, contour detection, obstacle avoidance, human-computer interaction, and force feedback control, how to obtain a six-dimensional force sensor with superior performance has become one of the hot issues studied by scholars at home and abroad.

[0003] Since the 1960s, when Stewart of Germany designed the first spatial parallel six-dimensional force sensor, many domestic and foreign scholars have begun to devote themselves to the development of six-dimensional force sensors. So far, there are many types of six-dimensional force sensors, such as piezoelectric, capacitive, strain gauge, photoelectric, etc. At the same time, in the development process of six-dimensional force sensors, many materials and different configurations of six-dimensional force sensors have also been invented. Among the many forms of six-dimensional force sensors, the strain gauge six-dimensional force sensor has a relatively simple manufacturing principle, relatively low cost, relatively long development time, and relatively mature manufacturing technology, which also determines that the vast majority of six-dimensional force sensor products on the market are resistance strain gauge six-dimensional force sensors. The parallel structure strain gauge six-dimensional force sensor is widely used because of its strong stiffness and load-bearing capacity, small coupling error and many other advantages.

[0004] Many parallel six-axis force sensors use a ball joint connection method, which regards the force measurement branch as a two-force rod that only bears axial force. From the perspective of sensor processing technology and actual installation, traditional ball joints have problems such as difficult processing technology and difficult installation and use, which also increases costs. From the perspective of actual effects, traditional ball joints are composed of a ball socket and a ball head, and there is a gap and friction between the two, which has become a factor affecting the error of the six-axis force sensor.

[0005] Chinese patent ZL99102526.1 designs a preloaded six-dimensional force sensor, which uses a cone-shaped spherical pair to replace the traditional ball pair, and adds a preloaded part, thereby reducing the influence of the excessive contact area between the ball head and the socket of the traditional ball pair and the gap on the sensor accuracy. However, the cone-shaped spherical pair increases the volume of the six-dimensional force sensor and reduces its application scenarios. Chinese patent CN201310038102.8 designs a cylindrical flexible ball joint to replace the traditional ball joint, thereby eliminating the problems of friction torque and gap in the ball joint. Since the notch of the cylindrical flexible ball joint is usually processed by milling, its special shape greatly increases the difficulty of processing. Secondly, how to install the cylindrical flexible ball joint on the upper and lower platforms and detection branches after processing has become another major problem.

[0006] Among the above-mentioned types of six-dimensional force sensors, no matter which ball joint form is adopted, there are problems such as difficulty in processing, installation and use, so there are some problems in the use of six-dimensional force sensors. Summary of the invention

[0007] In order to solve the above problems described in the existing six-dimensional force sensor, the present invention provides a six-dimensional force sensor using an annular flexible ball joint, which solves the problems of friction and clearance in traditional ball joints and the difficulty in processing and installing cylindrical flexible ball joints.

[0008] Technical solutions adopted by this product

[0009] A six-dimensional force sensor using an annular flexible ball joint. The sensor comprises an upper platform (1), a lower platform (5), a column (4), a force measuring branch (3), and an annular flexible ball joint (2). The upper platform (1) and the lower platform (5) are placed in parallel and have three columns (4). The annular flexible ball joint (2) is arranged on the upper platform (1), the lower platform (5), and the column (4), and a strain gauge is arranged on the force measuring branch (3). There are six force measuring branches (3), three of which form a group, and the force measuring branches (3) are placed horizontally and vertically in groups. Both ends of the horizontally placed force measuring branches (3) are connected to the annular flexible ball joints (2) on the column (4), and the vertically placed force measuring branches (3) are connected to the annular flexible ball joints (2) of the upper platform (1) and the lower platform (5). The annular flexible ball joint (2) is formed by milling. As can be seen from the definition of a flexible ball joint, a flexible ball joint is a component that is partially weakened by cutting and bends and deforms under the action of a force or moment. It can be seen that when a force or moment is applied to the annular flexible ball joint (2), it can bend and deform in three directions in space, thereby realizing the function of an ideal ball joint in three rotation directions in space.

[0010] Compared with the existing six-dimensional force sensor, the present invention has the following advantages: the annular flexible ball joint (2) has a simple cutout form and is symmetrically distributed, and can be easily processed by milling; the annular flexible ball joint (2) is directly processed and formed in the upper platform (1) and the lower platform (5), which solves the problem of difficult installation and use of traditional columnar flexible ball joints; it avoids the problems of gap, friction and excessive volume in traditional spherical pairs, and improves the measurement accuracy of the sensor.

[0011] The preferred embodiment of the present invention is:

[0012] The upper platform (1) and the lower platform (5) have three annular flexible ball joints (2), and each column (4) has an annular flexible ball joint (2). The annular flexible ball joint (2) is a semicircular groove. The semicircular grooves at both ends are arranged symmetrically about their center lines. A through hole is provided at the geometric center of the groove, and a concave platform is provided on the outside of the through hole. Every two annular flexible ball joints (2) and the force measuring branch (3) are arranged on the same axis. The force measuring branch (3) is provided with a threaded hole, and the annular flexible ball joint (2) and the force measuring branch (3) are connected by bolts.

[0013] The annular flexible ball joints (2) of the upper platform (1) and the lower platform (5) are distributed in an equilateral triangle.

[0014] The through hole of the annular flexible ball joint (2) is a tube perforation.

[0015] The force measuring branches (3) in a vertical state are evenly distributed on the same circumferential surface.

[0016] The geometric centers of the annular flexible ball joints (2) on the upright column are on the same plane and form an equilateral triangle.

[0017] Both ends of the force measuring branch (3) are provided with threaded holes.

[0018] The upper platform (1), the lower platform (5), the column (4) and the annular flexible ball joint (2) are arranged in an integrated manner.

[0019] The triangle formed by the axes of the three force measuring branches (3) is an equilateral triangle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the three-dimensional structure of an annular flexible ball joint.

[0021] Figure 2 The schematic diagram of the structure of a six-dimensional force sensor using an annular flexible ball joint.

[0022] In the figure: upper platform 1, annular flexible ball joint 2, force measuring branch 3, column 4, lower platform 5,

[0023] Bolt 6. DETAILED DESCRIPTION

[0024] The six-dimensional force sensor in this embodiment is composed of an upper platform 1, a lower platform 5, six columns 4, six force measuring branches 3, twelve annular flexible ball joints 2, and twelve screws 6.

[0025] The lower platform 5 is placed horizontally, and the upper platform 1 and the lower platform 5 are parallel to each other; a resistance strain gauge is arranged on the central axis of the force measuring branch 3, and the strain gauge measures the axial tensile and compressive stresses.

[0026] There are three annular flexible ball joints 2 on the lower platform 5 and the upper platform 1 , and there is one annular flexible ball joint 2 on each column 4 .

[0027] Both the lower platform 5 and the upper platform 1 have three mounting columns 4 .

[0028] There are six force measuring branches 3, three in each group, and the force measuring branches 3 are placed horizontally and vertically in groups; the two ends of the horizontally placed force measuring branches 3 are connected to the annular flexible ball joints 2 on the columns 4, and the vertically placed force measuring branches 3 are connected to the annular flexible ball joints 2 of the upper platform 1 and the lower platform 5.

[0029] A concave platform and a through hole are arranged at the center of the annular flexible ball joint 2.

[0030] Both ends of the force measuring branch 3 are provided with threaded holes, and the force measuring branch 3 and the annular flexible ball joint 2 are connected by screws 6.

[0031] The measurement principle of a six-dimensional force sensor using an annular flexible ball joint is: since both ends of the force measuring branch 3 are connected to the annular flexible ball joint 2, the two ends of the force measuring branch only bear axial force when subjected to force. When the force acting on the upper platform 1 is a force in the X and Y directions and a torque in the Z direction, the force is detected by placing the force measuring branch 3 horizontally; when the X and Y directions are a torque and the Z direction is a force, the force is detected by placing the force measuring branch 3 vertically.

[0032] The present invention can be applied to various fields requiring six-dimensional force measurement, such as precision force control, precision assembly, and robot safety detection.

[0033] The present invention is not limited to the above-mentioned embodiments. Without departing from the spirit and essential content of the present invention, relevant technical personnel can make appropriate modifications and variations based on the contents of the present invention, but the appropriate modifications and variations are within the scope of protection of the claims of the present invention.

Claims

1. A six-dimensional force sensor using an annular flexible ball joint, characterized in that: An upper platform (1), a lower platform (5), a column (4), a force measuring branch (3), and an annular flexible ball joint (2); the upper platform (1) and the lower platform (5) are placed in parallel and have three columns (4); the annular flexible ball joint (2) is arranged on the upper platform (1), the lower platform (5), and the column (4); strain gauges are arranged on the force measuring branch (3); three force measuring branches (3) form a group, and there are six in total; the force measuring branches (3) are placed horizontally and vertically in groups; both ends of the horizontally placed force measuring branch (3) are connected to the annular flexible ball joint (2) on the column (4); the vertically placed force measuring branch (3) is connected to the annular flexible ball joint (2) of the upper platform (1) and the lower platform (5).

2. A six-dimensional force sensor using an annular flexible ball joint according to claim 1, characterized in that: The annular flexible ball joint (2) is formed by processing two semicircular grooves on the outer surfaces of the upper platform (1), the lower platform (5) and the column (4). The circular grooves on the outer surfaces are arranged symmetrically about their center lines, and a through hole is provided at the center of the circular grooves.

3. A six-dimensional force sensor using an annular flexible ball joint according to claim 1, characterized in that: The upper platform (1), the lower platform (5) and the column (4) are provided with an annular flexible ball joint (2); the upper platform (1) and the lower platform (5) are provided with three annular flexible ball joints (2); the upper platform (1) and the lower platform (5) are provided with three columns (4) respectively, and each column (4) is provided with an annular flexible ball joint (2).

4. A six-dimensional force sensor using an annular flexible ball joint according to claim 1, characterized in that: Threaded holes are arranged at both ends of the force measuring branches (3). There are six force measuring branches (3) in total, with three branches forming a group. The force measuring branches (3) are placed horizontally and vertically in groups. Both ends of the horizontally placed force measuring branches (3) are connected to the annular flexible ball joints (2) on the columns (4), and the vertically placed force measuring branches (3) are connected to the annular flexible ball joints (2) of the upper platform (1) and the lower platform (5).

5. The six-dimensional force sensor using an annular flexible ball joint according to claim 1, characterized in that: The annular flexible ball joints (2) on the upper platform (1), the lower platform (5) and the pillars (4) are arranged in the form of an equilateral triangle.

6. A six-dimensional force sensor using an annular flexible ball joint according to claim 1, characterized in that: The annular flexible ball joint (2) and the force measuring branch (3) of the upper platform (1) and the lower platform (5) are on the same axis; the annular flexible ball joint (2) and the force measuring branch (3) on the column (4) are on the same axis and the plane formed by the axis is parallel to the upper and lower platforms.

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