Capacitive six-dimensional force sensor
Through the comb-tooth electrode structure and four-quadrant design of the capacitive six-dimensional force sensor, the overlap area between the plates is increased, solving the problems of large volume and low accuracy of traditional six-dimensional force sensors, and achieving high sensitivity measurement of small forces and moments in miniaturized occasions.
Patent Information
- Application Number
- CN202422162492.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-04
- Publication Date
- 2025-07-08
- Estimated Expiration
- 2034-09-04
AI Technical Summary
The existing six-dimensional force sensors have a large volume, a large range but low accuracy, making them difficult to apply in miniaturized occasions. They also lack the accuracy when measuring small forces and torques, have large crosstalk between dimensions, and have poor temperature performance.
Capacitive six-dimensional force sensor is adopted, and the comb-tooth electrode structure is used to increase the overlap area between the plates. Combined with the four-quadrant comb-tooth electrode structure, the sensitivity is increased through the differential capacitance output, and accurate measurement of small forces and moments is achieved.
It significantly improves the sensitivity and accuracy of the sensor, reduces interdimensional crosstalk, improves temperature performance, and is suitable for six-dimensional force measurement in miniaturized occasions.
Smart Images
Figure CN223077790U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of six - dimensional force sensors, in particular to a capacitive six - dimensional force sensor. Background Technique
[0002] The six - dimensional force sensor can measure the force signals in three directions of X, Y, and Z in space, and can also measure the torques around the three directions of X, Y, and Z. The six - dimensional force sensor is mainly applied to fields such as aerospace, electronic weighing scales, industrial control, and robots. At present, the six - dimensional force sensors on the market are mainly mechanical sensors, which have a large installation space and a large range, but have insufficient accuracy when measuring small forces and torques, and are not suitable for occasions requiring miniaturization and the measurement of small forces and torques. There is currently little relevant research on six - dimensional force sensors applied to miniaturized occasions such as the fingertips of robots and minimally invasive surgical medical robots.
[0003] Based on the working principle, the MEMS - based six - dimensional force sensors are commonly classified into piezoresistive and capacitive types. The working principle of the MEMS piezoresistive sensor is as follows: piezoresistors are fabricated on a specific crystal plane through ion implantation technology, and wires are fabricated through a metal film deposition process and the resistors are connected in a specific manner to form a Wheatstone bridge. When the sensor is subjected to external forces or torques, the resistance value changes, and the strain signal at the piezoresistor is converted into an electrical signal through the Wheatstone bridge to achieve the measurement of forces and torques. The working principle of the MEMS capacitive sensor is as follows: electrodes are etched on the upper and lower silicon wafers respectively. When the sensor is subjected to external forces or torques, the upper and lower electrode plates generate relative displacement, causing changes in the distance or overlapping area between the upper and lower electrode plates, thereby causing changes in the capacitance value to achieve the measurement of forces and torques.
[0004] Traditional six - dimensional force sensors are large in volume and difficult to apply in occasions with narrow installation spaces. At the same time, traditional six - dimensional force sensors have a large range but low accuracy, and are not accurate enough when measuring small forces or torques. Moreover, due to the structural limitations of the six - dimensional force sensor, the measurement sensitivity is low, the cross - coupling between dimensions is large, and the temperature performance is poor, resulting in a decline in the overall performance of the sensor. Content of the Utility Model
[0005] The purpose of the utility model is to provide a capacitive six - dimensional force sensor to solve the problems in the prior art.
[0006] To achieve the above - mentioned purpose, the utility model provides the following technical solution: A capacitive six - dimensional force sensor includes a bottom electrode plate, pads, and a top electrode plate. A corrugated ring is arranged on the top of the top electrode plate, and a top electrode, a top silicon column, and a top support ring are arranged at the bottom of the top electrode plate; a bottom electrode, a bottom silicon column, a bottom support ring, and a reference capacitor are arranged on the top of the bottom electrode plate, and the bottom electrode, the bottom support ring, and the reference capacitor are all connected to pads.
[0007] Preferably, the bottom electrode plate includes bottom comb teeth electrodes and bottom sector electrodes. The bottom electrode plates are distributed in four quadrants, and there are two bottom comb teeth electrodes and one bottom sector electrode in each quadrant.
[0008] Preferably, the top electrode plate includes top comb teeth electrodes and top sector electrodes. The top electrode plates are distributed in four quadrants, and there are two top comb teeth electrodes and one top sector electrode in each quadrant.
[0009] Preferably, the top electrode and the bottom electrode are staggered.
[0010] Preferably, the diameter of the inner ring of the corrugated ring is larger than the diameter of the etching area of the top electrode.
[0011] Compared with the prior art, the beneficial effects of the present utility model are as follows:
[0012] 1. By using the comb tooth type electrode structure, the overlapping area between the electrode plates is greatly increased. When under the action of force or torque, the change amount of the overlapping area between the upper and lower electrode plates also becomes larger, and the change amount of the output capacitance signal increases, thereby increasing the sensitivity.
[0013] 2. By adopting the four - quadrant comb tooth electrode structure, there are two capacitance outputs in each quadrant. Due to the distribution characteristics of the upper and lower electrode plates, when under the action of a single - direction force or torque, within the same quadrant, one of the two capacitances increases and the other decreases, forming a differential capacitance pair, further increasing the change amount of the output capacitance and further increasing the sensitivity. Description of the Drawings
[0014] The drawings are used to provide a further understanding of the present utility model, and constitute a part of the specification. Together with the embodiments of the present utility model, they are used to explain the present utility model, and do not constitute a limitation to the present utility model. In the drawings:
[0015] Figure 1 is the structural schematic diagram of the present utility model;
[0016] Figure 2 is the structural schematic diagram of the top electrode plate of the present utility model;
[0017] Figure 3 is the structural schematic diagram of the bottom electrode plate of the present utility model;
[0018] Figure 4 is the top view of the present utility model;
[0019] Figure 5 is the present utility model Figure 4 the cross - sectional view taken along B - B in.
[0020] In the figure: 1. Bottom plate; 2. Pad; 3. Top plate; 4. Corrugated ring; 11. Bottom comb electrode; 12. Bottom silicon column; 13. Bottom sector electrode; 14. Bottom support ring; 15. Reference capacitor; 31. Top silicon column; 32. Top support ring; 33. Top sector electrode; 34. Top comb electrode. Detailed implementation mode
[0021] To make the purpose, technical solution and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model. Therefore, the following detailed description of the embodiments of the present utility model provided in the drawings is not intended to limit the scope of the present utility model to be protected, but merely represents the selected embodiments of the present utility model.
[0022] Please refer to Figures 1-5 , in an embodiment of the present utility model, a capacitive six-axis force sensor includes a bottom plate 1, a pad 2 and a top plate 3. A corrugated ring 4 is arranged on the top of the top plate 3. The corrugated ring 4 is of an annular structure, and the diameter of the inner ring of the corrugated ring 4 is greater than the diameter of the top electrode etching area. A top electrode, a top silicon column 31 and a top support ring 32 are arranged at the bottom of the top plate 3; a bottom electrode, a bottom silicon column 12, a bottom support ring 14 and a reference capacitor 15 are arranged on the top of the bottom plate 1. The bottom electrode, the bottom support ring 14 and the reference capacitor 15 are all connected to the pad 2; the top electrode and the bottom electrode are arranged in a staggered manner.
[0023] The bottom plate 1 includes a bottom comb electrode 11 and a bottom sector electrode 13. The bottom plate 1 is distributed in four quadrants, and there are two bottom comb electrodes 11 and one bottom sector electrode 13 in each quadrant.
[0024] The top plate 3 includes a top comb electrode 34 and a top sector electrode 33. The top plate 3 is distributed in four quadrants, and there are two top comb electrodes 34 and one top sector electrode 33 in each quadrant.
[0025] The substrate of the top plate of the capacitive six-axis force sensor is a silicon wafer with crystal planes, including structures such as silicon pillars, corrugated rings, top electrodes, and support rings, all obtained through photolithography and etching processes. Among them, the silicon pillars are evenly distributed in the etching area of the top electrode on the back of the top plate, and together with the support ring, they play the role of support and force transmission. The silicon pillar structure is equivalent to adding evenly distributed spring elements between the upper and lower plates, significantly increasing the overload resistance of the six-axis force sensor. The corrugated ring is an annular area etched on the front. The diameter of the inner ring of the corrugated ring is larger than the diameter of the etching area of the top electrode on the back, isolating the etching area of the top electrode from the outer ring of the top plate, reducing the stiffness of the structure. Thus, when tangential forces (Fx, Fy) and torques (Mx, My) are applied to the sensor, the elastic deformation of the area containing the top electrode inside the corrugated ring of the upper plate increases, increasing the output of the differential capacitance and the sensitivity, while reducing the stress applied to the silicon pillars. In the actual manufacturing process, the structural stiffness of the top plate depends on the etching depth and width of the corrugated ring, and also on the number and diameter of the silicon pillars. The top electrode is in the shape of long comb teeth and a fan. Among them, the fan-shaped electrode is dedicated to measuring the normal stress Fz in the z direction, and the comb-shaped electrode measures the other five outputs. The top electrodes are distributed in four quadrants, facilitating the detection of the differential capacitance output.
[0026] The substrate of the bottom plate of the capacitive six-axis force sensor is a silicon wafer with crystal planes, including structures such as silicon pillars, bottom electrodes, and support rings, all obtained through photolithography and etching processes. Among them, the silicon pillars are evenly distributed in the electrode etching area on the front of the bottom plate, and their positions correspond one by one to the silicon pillars of the top plate. The silicon pillars of the top plate and the bottom plate are connected through a bonding process, playing a role in supporting and transmitting force to the sensor structure. The bottom electrodes are divided into comb-shaped structures and fan-shaped structures. For the comb structure, the bottom electrodes and the top electrodes are staggered, and there is a certain distance between the upper and bottom electrodes in the vertical direction. One comb unit of the top electrode overlaps with two comb units of the bottom electrodes. For the fan-shaped electrode, the total area of the top electrode is slightly smaller than that of the bottom electrode, ensuring that when subjected to shear direction forces and torques, the overlapping area between the bottom electrode and the top electrode remains unchanged. The electrodes are distributed in four quadrants, with two comb electrodes and one fan-shaped electrode in each quadrant. Each electrode has an external lead pad for connecting to the detection circuit. The support rings are distributed outside the area of the bottom electrodes, divided into an inner ring and an outer ring, playing a role in protecting the sensor structure from overload. There are two reference capacitors distributed between the inner and outer rings of the support ring. The external lead pads of the reference capacitors are used for connecting to the detection circuit and are electrically connected to the top plate at the same time.
[0027] When a normal force Fz is applied to the top plate, the silicon pillars are compressed, the gap between the top electrode of the sensor and the fan-shaped electrodes of the bottom electrode decreases, and the change in the gap is proportional to the magnitude of the applied normal force Fz. The change in the plate spacing will cause a change in the capacitance value. By measuring the change in the capacitance of the top electrode on the fan-shaped part, the magnitude of Fz can be calculated.
[0028] When shear forces Fx and Fy are applied to the top plate, the shear forces deform the corrugated ring and cause the silicon pillars to bend laterally. The top plate undergoes displacement within the plate plane, resulting in a change in the overlapping area of the comb-shaped regions between the top electrode and the bottom electrode, thus causing a change in capacitance. The change in the overlapping area is proportional to the magnitude of the applied shear force. Since the length of the comb-shaped units of the bottom electrode is greater than that of the top electrode, and the bottom plate completely covers the top plate in the length direction when the displacement of the top plate is maximum, when the shear force Fx is applied, the comb-shaped capacitance outputs in the second and fourth quadrants remain unchanged, while differential capacitance outputs are generated in the first and third quadrants. Similarly, when the shear force Fy is applied, the comb-shaped capacitance outputs in the first and third quadrants remain unchanged, and differential capacitance outputs are generated in the second and fourth quadrants. The magnitudes of Fx and Fy can be calculated based on the output situations of the differential capacitances in different quadrants.
[0029] When torques Mx and My are applied to the top plate, an angle is generated between the top electrode and the bottom electrode, and this angle is approximately proportional to the magnitude of the applied torque. By measuring the differential capacitance outputs of two opposite quadrants and combining the fan-shaped areas of each quadrant in the electrode region of the sensor, the magnitude of this angle can be calculated. Multiplying the angle between the two plates by the torsional stiffness in the x or y direction can calculate the magnitudes of Mx and My, and the torsional stiffness is a function of the number of silicon pillars and the distance of the silicon pillars from the center of the plate. The total torsional stiffness is the sum of the torsional stiffnesses contributed by all the silicon pillars.
[0030] When a torque Mz is applied to the top plate, the silicon pillars bend laterally along the center of the torque, and the overlapping areas of the top electrodes on the bottom in all four quadrants change, all generating differential capacitance outputs. The differential capacitance output is proportional to the magnitude of the applied torque Mz, and this ratio is related to the number of comb teeth of the electrode, the distance from the center of the comb teeth to the center of the plate, and the effective length of the electrode.
[0031] Finally, it should be noted that the above are only the preferred embodiments of the present utility model and are not used to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.
Claims
1. A capacitive six - dimensional force sensor, characterized in that: It includes a bottom electrode plate (1), a pad (2) and a top electrode plate (3). A corrugated ring (4) is arranged on the top of the top electrode plate (3). A top electrode, a top silicon column (31) and a top support ring (32) are arranged on the bottom of the top electrode plate (3). A bottom electrode, a bottom silicon column (12), a bottom support ring (14) and a reference capacitor (15) are arranged on the top of the bottom electrode plate (1). The bottom electrode, the bottom support ring (14) and the reference capacitor (15) are all connected to the pad (2).
2. The capacitive six-axis force sensor according to claim 1, wherein: The bottom electrode plate (1) includes a bottom comb-shaped electrode (11) and a bottom sector electrode (13). The bottom electrode plate (1) is distributed in four quadrants, and there are two bottom comb-shaped electrodes (11) and one bottom sector electrode (13) in each quadrant.
3. A capacitive six - dimensional force sensor according to claim 1, characterized in that: The top electrode plate (3) includes a top comb-shaped electrode (34) and a top sector electrode (33). The top electrode plate (3) is distributed in four quadrants, and there are two top comb-shaped electrodes (34) and one top sector electrode (33) in each quadrant.
4. The capacitive six-axis force sensor according to claim 1, wherein: The top electrode and the bottom electrode are staggered.
5. A capacitive six-axis force sensor according to claim 1, wherein: The corrugated ring (4) is of an annular structure, and the diameter of the inner ring of the corrugated ring (4) is larger than the diameter of the etching area of the top electrode.