CN103542963A - Variable-gain three-dimensional force sensor - Google Patents

Abstract

The invention discloses a three-dimensional force sensor with variable gain, which comprises an elastic body, an upper gain control frame and a lower gain control frame. The elastic body includes four fixed platforms, a central loading platform, four outer floating beams, four inner floating beams and four elastic beams. The upper and lower gain control frames are in the shape of sheets, and are respectively fixed on the upper and lower sides of the fixed platform to control the gain of the z-axis force. Four elastic beams respectively extend from the four sides of the central loading table and are connected to the inner floating beams. The outer floating beam is parallel to the inner floating beam with gain control for the x and y axes. The present invention realizes a three-dimensional force sensor with variable gain, so that within a small range, the strain maintains a high gain to the input force value, and is in a low gain between the range and the full range, so that the sensor In the case of meeting the actual measurement needs, the fusion of high sensitivity, large range and small volume is achieved.

Description

A 3D Force Sensor with Variable Gain

technical field

The invention relates to a three-dimensional force sensor, in particular to a three-dimensional force sensor with variable gain, and belongs to the technical field of sensors.

Background technique

Since its appearance in the 1970s, multi-dimensional force sensors have been firstly applied in the field of intelligent robots. In recent years, they have also been widely used in aerospace, machinery manufacturing and assembly, medical engineering, automotive industry, and sports competitions.

The three-dimensional force sensor measures the three force components (Fx, Fy, Fz) in the three-dimensional space of rectangular coordinates, and is the most widely used type of multi-dimensional force sensor. The strain-type three-dimensional force sensor based on the cross-shaped elastic beam structure is the most commonly used one in this field. It has the advantages of simple and compact structure, high sensitivity, and small inter-dimensional crosstalk. However, with the increasing demand for high-performance three-dimensional force sensors, the limitations caused by the contradiction between their sensitivity and stiffness have become increasingly prominent, namely: high-sensitivity sensors have low stiffness and cannot measure large-scale forces; The sensor has poor sensitivity and cannot be sensitive to small force value changes.

In practical applications, the effect of high sensitivity is more obvious only in a small range, and when the measured force value is large, the value of the same sensitivity is weakened. Therefore, a three-dimensional force sensor with variable gain is developed so that its strain maintains a high gain (high sensitivity) to the input force value in a small range, and a low value between the range and the full range. The gain (low sensitivity) state can effectively overcome the contradiction between sensitivity and stiffness, and meet the needs of large range and high sensitivity in actual use, so it has high practical value.

Contents of the invention

The technical problem to be solved by the present invention is to provide a three-dimensional force sensor with variable gain, so that in a small range, the strain maintains a high gain to the input force value, and is in a low gain between the range and the full range, As a result, the sensor achieves fusion of high sensitivity, large range, and small volume while meeting the actual measurement requirements.

Technical solution: In order to solve the above technical problems, the technical solution adopted in the present invention is as follows: a three-dimensional force sensor with variable gain, including an elastic body, an upper gain control frame fixed above the elastic body, and a lower gain control frame fixed below the elastic body Control frame; the elastic body includes a central loading platform, four fixed platforms, four outer floating beams, four inner floating beams and four elastic beams, wherein the four fixed platforms are symmetrically distributed in the central loading around the platform; the four outer floating beams connect two adjacent fixed platforms; the four inner floating beams are located inside the corresponding outer floating beams and parallel to the four outer floating beams; The above four elastic beams respectively extend from the centers of the four sides of the central loading platform and are connected to the inner floating beams; the heights of the outer floating beams and the inner floating beams are equal, and the corresponding inner floating beams and outer floating beams There is a gap between them; the setting of the gap makes the outer floating beam play a role in gain control, the size of the gap is related to the actual required range range I, and the range can be analyzed according to the ANSYS finite element analysis software known to those skilled in the art. The maximum amount of deformation under I to determine the size of the gap.

The upper gain control frame and the lower gain control frame have the same shape, which is in the shape of a thin sheet, and the plane shape is a centrosymmetric figure. The upper gain control frame and the lower gain control frame are respectively composed of four upper floating beams and four lower floating beams. One upper floating beam and four lower floating beams are respectively perpendicular to the four elastic beams, and there is a vertical gap between the elastic beams, and the upper gain control frame and the lower gain control frame enclose a The square empty slot, the gap between the upper floating beam and the elastic beam and the gap between the lower floating beam and the elastic beam ensure the gain control effect of the upper floating beam and the lower floating beam. The measurement range I is related, and the maximum deformation under the measurement range I can be analyzed according to the ANSYS finite element analysis software known to those skilled in the art to determine the size of the gap.

The elastic body has a monolithic structure and is symmetrical about the Cartesian three-dimensional coordinate axis. Each fixed platform of the elastic body is provided with a through hole in the center, and a corner close to the central loading platform is provided on the upper surface and the lower surface respectively. The inward depression constitutes an upper frame fixing platform and a lower frame fixing platform, and the planes enclosed by the upper frame fixing platform and the lower frame fixing platform are adapted to the upper gain control frame and the lower gain control frame respectively.

The four corners of the upper gain control frame and the lower gain control frame are provided with four fixing holes, and the centers of the upper frame fixing table and the lower frame fixing table are provided with fixing holes matching the upper gain control frame and the lower gain control frame. The upper gain control frame and the lower gain control frame are fixed on the fixing platform of the elastic body through the cooperation of the fixing hole and the threaded hole.

Wherein, the gap between the outer floating beam and the inner floating beam, the gap between the upper floating beam and the elastic beam in the vertical direction, and the vertical gap between the lower floating beam and the elastic beam can preferably be 0.5mm- 1mm.

Preferably, the upper floating beam and the lower floating beam can be designed to move inwardly toward the central loading table, so that the upper floating beam and the lower floating beam are closer to the root of the elastic beam. The distance between the upper floating beam and the lower floating beam and the root of the elastic beam is used to adjust the gain change when loading in the z direction, and the closer to the root of the elastic beam, the more obvious the gain change.

Beneficial effects: compared with the prior art, the present invention has the following beneficial effects:

(1) Realize the variable gain of three-dimensional force. The present invention adopts a double floating beam structure, and adds an upper and lower gain control frame, so that the strain of the sensor maintains a high gain (high sensitivity) to the input force value within a small range, and the strain from outside the range to the full range keep the gain low (low sensitivity). The present invention satisfies the power of the three dimensions of x, y, and z: within the measuring range I, the change of the elastic strain sensitive to the unit force is relatively large; within the measuring range II, the change of the elastic strain sensitive to the unit force is small small, thus achieving a variable gain in three-dimensional force.

(2) The structure is simple and compact. The invention retains the advantages of the cross elastic beam structure, has a simple structure, is easy to process, and has little crosstalk between dimensions.

(3) The combination of high sensitivity, large range and small volume has been achieved. Compared with sensors with the same volume, the present invention has significantly larger measuring range. Compared with sensors with the same range, it has obvious high sensitivity in the range I, so that the fusion of high sensitivity, large range and small volume can be truly realized.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the sensor of the present invention.

Fig. 2 is a schematic structural diagram of the sensor elastic body of the present invention.

Fig. 3 is a structural schematic diagram of the upper (lower) gain control frame type I of the sensor of the present invention.

Fig. 4 is a schematic structural diagram of the upper (lower) gain control frame type II of the sensor of the present invention.

FIG. 5 is a deformation diagram of the sensor of the present invention subjected to Fx in the range I.

Fig. 6 is a deformation diagram of the sensor of the present invention subjected to Fx in the range II.

FIG. 7 is a deformation diagram of the sensor of the present invention subjected to Fz in the range I.

Fig. 8 is a deformation diagram of the sensor of the present invention subjected to Fz in the range II.

Fig. 9 is an output characteristic of the sensor of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, further illustrate the present invention, should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various aspects of the present invention Modifications in equivalent forms all fall within the scope defined by the appended claims of this application.

The specific implementation manner of the present invention will be described below in conjunction with the accompanying drawings.

As shown in FIG. 1 , the variable gain three-dimensional force sensor of the present invention includes an elastic body 1 , an upper gain control frame 2 and a lower gain control frame 3 . The elastic body has a monolithic structure and is symmetrical about the Cartesian three-dimensional coordinate axis. As shown in FIG. 2 , the elastic body includes four fixed platforms 11 , a central loading platform 12 , four outer floating beams 13 , four inner floating beams 14 and four elastic beams 15 . Four fixed platforms 11 are symmetrically distributed around the central loading platform 12, and four outer floating beams 13 and four inner floating beams 14 form four pairs of double beams, respectively connecting adjacent fixed platforms 11 two by two. Four elastic beams 15 respectively extend from four sides of the central loading platform 12 and are connected with the inner floating beams 14 . The four inner floating beams 14 are located inside and parallel to the corresponding outer floating beams, and the heights of the inner and outer floating beams are equal. There are slender empty slots in the inner and outer floating beams, so that the outer floating beams play a role of gain control. The size of the spacing between the inner floating beam and the outer floating beam is related to the actual required range I, and the maximum deformation under the range I can be analyzed according to the ANSYS finite element analysis software known to those skilled in the art to determine the size of the gap. Generally, it has better performance between 0.5mm-1mm.

A through hole 111 is provided in the center of each fixing platform 11 of the elastic body, which is used for fixing the sensor to the external base in practical application. A corner near the center loading platform 12 is recessed inwardly on the upper surface and the lower surface respectively to form an upper frame fixing platform 112 and a lower frame fixing platform 113, and a threaded hole 114 is set at the center of the upper frame fixing platform 112 and the lower frame fixing platform 113 Used to fix upper gain control frame 2 and lower gain control frame 3.

As shown in Fig. 3 and Fig. 4, the upper gain control frame and the lower gain control frame are in the shape of a sheet, and the planar shape is a centrally symmetrical figure. The upper gain control frame and the lower gain control frame are identical in shape, and are composed of four upper floating beams 22 and four lower floating beams respectively. Four fixing holes 21 are arranged at the four corners of the frame, and a square larger than the central loading platform 12 is formed in the middle. Empty groove 23, described fixing hole 21 cooperates with the fixing table 11 of described elastic body, four floating beams 22 are perpendicular to four elastic beams 15 respectively, and leave gap in axial direction, the size of this gap is the same as the actual It is related to the required range I, and the maximum deformation under the range I can be analyzed according to the ANSYS finite element analysis software well known to those skilled in the art to determine the size of the gap. Generally, it has better performance between 0.5mm and 1mm. The type of gain control frame can be changed by the position of the upper floating beam or the lower floating beam, as shown in Fig. 3 (Type I) and Fig. 4 (Type II). Type I is square as a whole, and the processing is simple. Type II moves the upper floating beam and the lower floating beam closer to the root of the elastic beam by moving the lower floating beam of the upper floating beam. The distance of is used to adjust the gain change when loading in the z direction, the closer to the root of the elastic beam, the more obvious the gain change. According to actual use requirements, the upper and lower gain floating beams can be brought closer to the root of the elastic beams in a manner similar to Type II.

The measurement of Fx, Fy and Fz by the sensor of the present invention is divided into two stages: from 0 to a certain force value is a high-gain stage, which is called the range I. In this stage, the strain increment sensitive to the unit force value is large and the sensitivity is high. The period from this specific force value to the full scale force value is a low gain stage, called Scale Range II. In this stage, the strain increment sensitive to the unit force value is small and the sensitivity is low, but it can effectively measure larger force values. The floating beams of the upper and lower gain control frames are used to control the measurement gain of the z-axis force; the outer floating beams of the x-axis control the measurement gain of the x-axis force; the outer floating beams of the y-axis control the measurement gain of the y-axis force.

FIG. 5 is a deformation diagram of the sensor of the present invention subjected to Fx in the range I. At this time, the inner floating beam in the x-axis is not in contact with the outer floating beam, and the output gain of the sensor is large and the sensitivity is high. Fig. 6 is a deformation diagram of the sensor of the present invention subjected to Fx in the range II. At this time, the inner floating beam is in contact with the outer floating beam, and the inner floating beam and the outer floating beam are combined to form a large rigidity floating beam, which increases the stiffness of the sensor, reduces the output gain, and can effectively measure a large force value. Due to the symmetry of the sensor structure, the case subject to Fy is consistent with the case of Fx.

FIG. 7 is a deformation diagram of the sensor of the present invention subjected to Fz in the range I. At this time, the elastic beam is not in contact with the upper floating beam and the lower floating beam, and the output gain of the sensor is large and the sensitivity is high. Fig. 8 is a deformation diagram of the sensor of the present invention subjected to Fz in the range II. At this time, the elastic beam is in contact with the upper floating beam and the lower floating beam, and the upper floating beam and the lower floating beam play a supporting role in the deformation process of the elastic beam, so that the stiffness of the sensor increases and the output gain decreases.

Figure 9 shows the sensor output characteristics. In the range I, the strain increment of the sensitive part of the sensor (located on the elastic beam, which is also the sticking part of the strain gauge) is large, because the elastic strain is proportional to the resistance change of the strain gauge and also proportional to the voltage output of the bridge, so The elastic strain can represent the output of the sensor. It can be seen that the output gain of the sensor in the range I is large and the sensitivity is high; in the range II, due to the support of the floating beam, the output gain decreases, the sensitivity decreases, and the stiffness increases, which can effectively measure larger force values.

Claims (5)

1. a three-dimensional force sensor for variable gain, is characterized in that, comprises elastic body (1), is fixed on the upper gain control framework (2) of elastic body (1) top and is fixed on the lower gain control framework (3) below elastic body (1);

Described elastic body (1) comprises a center loaded platform (12), four fixed stations (11), four outer floating beams (13), four interior floating beams (14) and four elastic beams (15), wherein, described four fixed stations (11) are symmetrically distributed in the surrounding of center loaded platform (12); Described four outer floating beams (13) are connected adjacent fixed station (11) between two; Described four interior floating beams (14) are positioned at corresponding outer floating beam (13) inner side parallel with described four outer floating beams (13); Described four elastic beams (15) extend out and are connected with described interior floating beam (14) from the center of four sides of center loading bench (12) respectively; Described outer floating beam (13) is highly equal with interior floating beam (14), and is provided with gap between corresponding interior floating beam (14) and outer floating beam (13);

Described upper gain control framework (2) is identical with lower gain control framework (3) shape, be laminar, symmetric figure centered by flat shape, upper gain control framework (2) and lower gain control framework (3) are comprised of four upper floating beams (22) and four lower floating beams respectively, four upper floating beams (22) are vertical with four elastic beams (15) respectively with four lower floating beams, and in the vertical direction leaves gap respectively and between elastic beam, described upper gain control framework (2) and lower gain control framework (3) surround the square dead slot (23) that is greater than center loaded platform (12).

2. the three-dimensional force sensor of variable gain according to claim 1, it is characterized in that, described elastic body is monolithic construction, and about Descartes's three-dimensional coordinate rotational symmetry, described elastomeric each fixed station (11) is provided with through hole (111) at center, and it caves inward respectively and forms upper frame fixed station (112) and underframe fixed station (113) at upper surface and lower surface near one jiao of center loaded platform (12), the plane that described upper frame fixed station (112) and underframe fixed station (113) surround is suitable with upper gain control framework (2) and lower gain control framework (3) respectively.

3. the three-dimensional force sensor of variable gain according to claim 1 and 2, it is characterized in that, four jiaos of described upper gain control framework (2) and lower gain control framework (3) are provided with four fixed orifices (21), the center of described upper frame fixed station (112) and underframe fixed station (113) is provided with the threaded hole (114) that the fixed orifice (21) with upper gain control framework (2) and lower gain control framework (3) matches, described upper gain control framework (2) and lower gain control framework (3) are fixed on described elastomeric fixed station (11) by described fixed orifice (21) and threaded hole (114).

4. the three-dimensional force sensor of variable gain according to claim 1, it is characterized in that, the gap of gap, upper floating beam and elastic beam in the vertical direction between outer floating beam (13) and interior floating beam (14) and the gap of lower floating beam and elastic beam in the vertical direction are 0.5mm-1mm.

5. the three-dimensional force sensor of variable gain according to claim 1, is characterized in that, described upper floating beam (22) and lower floating beam are designed to move in center loaded platform (12), makes floating beam (22) and lower floating beam near elastic beam root.

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