DEVICE FOR MEASURING DEFORMATIONS, STRESSES, FORCES AND/OR TORQUES IN A PLURALITY OF AXES

Abstract

The invention preferably relates to an apparatus for measuring deformations, stresses, forces and/or torques of an object comprising a spring body and a sensor chip, which comprises one or more sensor elements for measuring a deformation, stress, force and/or a torque as well as an electronic circuit on a substrate. The spring body comprises a base plate on the front side of which a force conductor, preferably in the form of a pin, is installed, the sensor chip being positioned on the rear side of the base plate below the force conductor. The invention further relates to a system comprising a described apparatus and a data processing unit, wherein the data processing unit is configured for reading out measured data detected by the sensor chip and preferably detects the forces and/or torques acting on the force conductor based thereon.

Claims

1. An apparatus for measuring multi-axis loads on an object comprising: a spring body, and a sensor chip comprising one or more sensor elements configured to measure deformations, stresses, forces and/or torques and an electronic circuit on a substrate, wherein the spring body comprises a base plate on the front side of which a force conductor is installed, wherein the sensor chip is positioned on the rear side of the base plate below the force conductor.

2. The apparatus according to the preceding claim 1, wherein the spring body is configured in such a way that forces and/or torques acting on the force conductor are concentrated in a localized area of the base plate, such that the sensor chip installed on the rear side below said area enables conclusions to be drawn about the forces and/or torques acting on the force conductor on the basis of a measurement of deformations or stresses of its substrate that is connected to said area of the base plate.

3. The apparatus according to claim 1, wherein the force conductor is formed by a pin which is substantially perpendicular to the base plate when no force is exerted upon it.

4. The apparatus according to claim 3, wherein the pin has a diameter from 0.5 mm to 5 mm, a length from 5 mm to 500 mm, and/or an aspect ratio of diameter to length from 1:3 to 1:100.

5. The apparatus according to claim 3, wherein the pin has a central bore.

6. The apparatus according to claim 1, wherein the base plate has a thickness between 0.1 mm and 2 mm.

7. The apparatus according to claim 1, wherein the base plate and/or the force conductor has a relief groove, in the form of a border around the area where the force conductor comes into contact with the base plate.

8. The apparatus according to claim 1, wherein the base plate and/or the force conductor are formed from a metal.

9. The apparatus according to claim 1 wherein the one or more sensor elements are configured for a resistive, optical, magnetic, inductive and/or capacitive measurement of deformations, stresses, forces and/or torques of the substrate.

10. The apparatus according to claim 1 wherein the one or more sensor elements comprise piezoresistive structures, and/or the sensor chip has more than 5 more sensor elements, the sensor elements having different sensitivities for a measurement of deformations, stresses, forces and/or torques of the substrate.

11. The apparatus according to claim 1 wherein the sensor chip is configured to measure deformations, stresses, forces and/or torques in multiple axes and/or to measure a two-dimensional distribution of deformations, stresses, forces and/or torques of the substrate.

12. The apparatus according to claim 1 wherein the substrate of the sensor chip comprises a semiconductor material.

13. The apparatus according to claim 1 wherein the substrate of the sensor chip has a thickness between 100 ?m and 600 ?m.

14. A system comprising: a) an apparatus according to claim 1, and b) a data processing unit, wherein the data processing unit is configured for reading out the measured data detected by the sensor chip.

15. A system according to claim 1 wherein the data processing unit is configured to detect the forces and/or torques acting on the force conductor from the measured data related to deformations, stresses, forces and/or torques of the substrate detected by the sensor chip.

16. The apparatus according to claim 8, wherein the metal is selected from the group consisting of iron, steel, stainless steel, spring steel, brass, copper, titanium, aluminum, lead, magnesium, beryllium copper and an alloy of the aforementioned.

17. The apparatus according to claim 1 wherein the one or more sensor elements are configured for a piezoresistive measurement of deformations, stresses, forces and/or torques of the substrate.

18. The apparatus according to claim 10 wherein the one or more sensor elements comprise piezoresistive sensor bridges.

19. The apparatus according to claim 12, wherein the semiconductor material is selected from the group consisting of silicon, monocrystalline silicon, polysilicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride and indium phosphide.

Description

DETAILED DESCRIPTION

[0137] In the following, the invention will be explained in more detail by means of examples, without being limited to them.

[0138] FIG. 1 shows a schematic illustration of a preferred embodiment of a spring body 1 according to the invention.

[0139] The spring body 1 comprises a force conductor 3, which has the shape of a pin and mechanically couples into a base plate 5 in a fixing area. Without the application of force, the force conductor 3 is substantially perpendicular to the base plate 5. Forces or torques acting on the force conductor 3 cause deflections or deformations which are directly transmitted to the fixing area of the base plate 3.

[0140] FIG. 1A shows a top view of the spring body 1 such that the front side of the base plate 5 is visible. FIG. 1 B illustrates the rear side of the base plate 5.

[0141] FIG. 1A illustrates a deflection of the force conductor 3 in a spatial direction. As can be seen in FIG. 1B, such a deflection results in a characteristic deformation of the rear side of the base plate 5 below the pin 3. Red areas indicate extension, while blue areas indicate compression. The arrangement or alignment of the areas of compression and extension allow a highly precise resolution of the direction of the deflection of the force conductor 3. The amplitude of the deformation or stress in the base plate 5 also correlates very precisely with the amplitude of the deflection of the force conductor 3.

[0142] The illustrated spring body 1 thus allows the forces and/or torques acting on the force conductor 3 to be concentrated in a localized area of the base plate 5, such that a sensor chip (not shown in FIG. 1) on the rear side below said area allows conclusions to be drawn about the forces and/or torques acting on the force conductor 3 on the basis of a measurement of deformations, stresses, forces and/or torques of its substrate connected to said area of the base plate 5.

[0143] For this purpose, the shape of a round pin 3, which is substantially perpendicular to the base plate 5 without any forces, has proved advantageous. Particularly good results can also be achieved if the pin 3 has a central bore 6 and there is a relief groove 7 in the form of a border is present in the base plate 5 and/or the force conductor 3.

[0144] FIGS. 2 and 3 illustrate the measurement of the resulting stresses or deformations in the area of the base plate 5 underneath the force conductor 3.

[0145] As illustrated in FIGS. 2A and B, the sensor chip 2 or its substrate experiences an analogous deformation or stress distribution due to its direct coupling to the base plate 5, which can be recorded on the sensor chip 2 by means of the sensor elements (not shown).

[0146] FIG. 3 illustrates a two-dimensional stress distribution at the base plate 5 resulting from a deflection of the force conductor 3 as shown in FIG. 1.

[0147] FIGS. 3A and 3B show, respectively, the two-dimensional distribution of normal stresses Sx (or ?.sub.xx) and Sy (or ?.sub.yy).

[0148] The sensor chip 2 or the sensor elements installed thereon preferably detect the difference of the normal stresses S.sub.x?S.sub.y (or ?.sub.xx??.sub.yy)

[0149] The difference can be seen in FIG. 3 C. Advantageously, the stress distribution is characterized by a series of characteristic peaks which allow a highly precise measurement of the deflection of the force conductor 3.

[0150] FIG. 4 illustrates a preferred embodiment of a sensor chip 2, showing the sensor technology or electronics located on the substrate.

[0151] The sensor chip 2 comprises a total of 32 sensor elements 9, which are positioned at different positions on the substrate to ensure a two-dimensional resolution of the stress distribution. The sensor chip 2 itself has a length and width of approx. 2 mm?2.5 mm and a thickness of approx. 300 ?m.

[0152] The sensor chip 2 is fully integrated in CMOS technology. The sensor elements 9 are piezoresistive sensor bridges which are preferably Wheatstone bridges (see FIGS. 4 B and C).

[0153] FIG. 4B illustrates a sensor element 9 which is a piezoresistive sensor bridge of the PMOS type and is aligned parallel to the coordinate system (x,y) and is sensitive in particular to the difference in normal stresses ?.sub.xx??.sub.yy.

[0154] FIG. 4 C shows a sensor element 9, which is a piezoresistive sensor bridge of the NMOS type and is oriented at 45? to the coordinate system (x,y) and is sensitive in particular to shear stress ?.sub.xy.

[0155] In addition to the sensor elements 9, the sensor chip has additional electronic components. In particular, the sensor chip 2 comprises a control logic as electronic circuit 11 or an analog-to-digital converter (ADC) and an operational amplifier (differential difference amplifier (DDA)). In the preferred embodiment, there is also an inductive interface (telemetric interface) for wireless readout of measured data or for power supply.

[0156] One example application of a preferred apparatus is illustrated in FIG. 5. Here, the apparatus with the force conductor 3 is present within a joystick. A movement of the joystick leads to a deflection of the force conductor 3, which can be detected on the basis of a measurement of the stress or deformation distribution by the sensor chip (not illustrated).

[0157] To supply power to the sensor chip and to read out the measured data, the apparatus comprises an inductive interface in the form of a secondary coil. The electrical power required for operation can be coupled in by an external base unit or reader, which comprises a primary coil for this purpose. Thereupon, the integrated sensor elements can measure the voltage or deformation distribution and in turn transmit measured data wirelessly to the base unit or reader.

[0158] The base unit or reader can already perform a (pre)evaluation of the data by means of an electronic reading process as a data processing unit. Preferably, the measured data is also transferred to another external data processing unit, for example a PC, notebook or mobile device, for evaluation, visualization and/or storage.

LIST OF REFERENCE SIGNS

[0159] 1 Spring body [0160] 2 Sensor chip [0161] 3 Force conductor, preferably pin [0162] 5 Base plate [0163] 6 Central bore [0164] 7 Relief groove [0165] 9 Sensor elements [0166] 11 Electronic circuit, for example ASIC [0167] 13 Inductive interface

BIBLIOGRAPHY

[0168] Gieschke P., Y. Nurcahyo, M. Herrmann, M. Kuhl, P. Ruther and O. Paul, CMOS Integrated Stress Mapping Chips with 32 N-Type or P-Type Piezoresistive Field Effect Transistors, 2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems, Sorrento, Italy, 2009, pp. 769-772, doi: 10.1109/MEMSYS.2009.4805496.

[0169] Jaeger Richard. C., Suhling, Jeffrey C., Ramani, Ramanathan, Bradley, Arthur T. and Xu, Jianping, CMOS Stress Sensors on (100) Silicon, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 35, NO. 1, January 2000.

[0170] Kuhl M., Gieschke, P., Rossbach, D., Hilzensauer, S., Panchaphongsaphak, T., Ruther, P., Lapatki, B., Paul, O., Manoli, Yi, A Wireless Stress Mapping System for Orthodontic Brackets Using CMOS Integrated Sensors, in IEEE Journal of Solid-State Circuits, vol. 48, no. 9, pp. 2191-2202, September 2013, doi: 10.1109/JSSC.2013.2264619.