DE10217019C1 - Force-torque sensor has disc-shaped reception part with peripheral sections attached to central part via respective spokes and coupled via coupling sections - Google Patents

Abstract

The sensor has a monolithic disc-shaped reception part (20) with a planar surface having a central part (21) with high rigidity and at least 3 peripheral sections (22) of medium rigidity at the ends of respective radial spokes (24), coupled via sections (23) of low rigidity. The spokes are each provided with a U-shaped recess, with expansion measuring strips connected in a Wheatstone bridge circuit applied to the planar surfaces of the peripheral sections and the coupling sections, for providing 3 force values and 3 torque values.

Description

The invention relates to force-moment sensors.

Regarding the fine manipulation of a robotic hand, there are big ones Demands on a so-called intelligent multidimensional len force-moment sensor placed in the fingertips the robot hand is provided. On top of that, it requires a lot cramped installation space in the fingertips a mechanically very compact sensor.

There are different types of force-moment sensors, which are housed in the fingertips of robot hands. For example, a six-component sensor with six strain gauges arranged on a cylinder is known. (See Antonio Bicchi "A criterion for optimal design of multi-axis force sensors" in Robotics and Autonomous Systems 10 ( 1992 ) pp. 269 to 286 in Elsevier Science Publishers B.V) The cylinder shape chosen by Bicchi, however, makes it difficult to find one the specified orientation, correct sticking of the strain gauges and is also very complex in terms of calibration.

In a further known embodiment of a six-component sensor six strain gauge pairs are arranged on a cuboid. (See Ch. Schwarzinger, L. Supper and Dr. H. Winsauer "Strain gauges as sensors for the control of the manipulative robotic hand ÖDIPUS, Meßtechnische Briefe 27 ( 1991 ), Issue 1, pp. 12 to 17). The sensor used in this sensor version Cuboid requires a relatively large amount of space in the fingertip in terms of its length and cross-section, and on top of that, this sensor version can only measure forces and moments that act directly on the fingertip.

A force-moment sensor is known from DE 100 13 059 C2, in which an approximately circular receiving part min at least three of the same size, at equal angular intervals long along the peripheral region of the receiving part, bie stiff sections, at least three flexible sections between between the rigid sections and at least three each because starting from the three flexible sections, radial has aligned connecting webs.

These connecting webs are perpendicular to the one at for example in the xy plane of a Cartesian coordinate system aligned center plane of the receiving part ten, axially symmetrical, rigid support part connected. In which Force-moment sensors are depending on the flexible sections because preferably two form a pair of strain gauges Strain gauges applied.

These strain gauges are connected to quarter, half or full bridges according to the principle of a Wheatstone bridge, so that the corresponding measured values can be derived from the strains or compressions detected by means of the strain gauges during a load. A total of three components are derived from these measured values in a data signal processing device, namely the moments M _x and M _y generated in the center plane corresponding to the xy plane, for example, and a force F perpendicular thereto, ie acting in the direction of the z axis _z determined.

In order to determine not only the force F _z but also two further forces F _x and F _y - acting in the direction of the x- and y-axis, there are at least four more on the axisymmetric part parallel to its central axis corresponding to the z-axis aligned strain gauges applied. In order to also determine the moment M _z , four strain gauges are aligned on the axially symmetrical support part at an angle to its center axis.

A disadvantage of the device known from DE 100 13 059 C2 is that with this sensor structure parts, namely for example as the perpendicular to the center plane of the receiving part straightened rigid support with the radially aligned trained connecting webs central area this Sensors are connected for example by gluing. here however, the measuring accuracy and thus also the reliability negatively impacted. It is also known to the force-moment sensors ensure the correct application of strain Measurement strips for example on a cylinder, cuboid or compli on the outer surfaces of the axisymmetric part adorned and therefore very time consuming. Another disadvantage is that in the execution by the provided in the middle Support part of the space for evaluation electronics limited is because there must be a hole in the middle of the board.

The object of the invention is therefore to miniaturize force To design torque sensors in a very compact manner, and beyond that sometimes very time-consuming application of strain gauges to facilitate and simplify and at the same time up to six components, d. H. three moments and three forces to determine decoupled.

According to the invention, this object is in a miniaturi based force-moment sensor according to one of claims 1 or 2 and also solved claims 3 or 4. here  are miniaturized according to the invention by means of Force-torque sensor according to claims 1 and 2 six compo elements, namely three moments and three forces and by means of the Force-moment sensors according to claims 3 and 4 two compo nenten, namely two forces exactly determined by measuring and then determined.

Advantageous further developments of the force-moment sensors are The subject matter of claims 5 to 11. Furthermore, in the Claims 12 to 16 different uses and uses possibilities of the force-moment sensors according to the invention given.

The force-moment sensors according to the invention are very compact since they are designed as a monolithic receiving part with a flat surface. Here, in the preferred embodiments on the monolithic part each strain gauges or means are brought up and combined to form a plurality of measuring bridges, which then makes a total of six components, namely three mutually orthogonal moments M _x , M _y and M _z and three also to one another orthogonal forces F _x , F _y , F _{z can be} detected and determined. Here, the strain gauges are applied in one plane to circumferential areas, preferably at regular intervals and additionally to the connecting parts running radially to the circumferential areas. This allows feedback on the respective moments and forces to be obtained, which act on the measuring level.

The big advantage over all previously known power Moment sensors is particularly in the very flat, com compact design, and especially in that measuring grids in egg  ner level can be applied from one side. on because of this advantageous design of the invention Force-moment sensors can lead to the usual sticking of Strain gauges also other alternative methods are used because the general necessary free access to the area (s) which strain gauges should be applied or must, only in the inventive embodiments of Force-moment sensors are given and guaranteed.

Miniaturized force-moment sensors according to the invention can therefore preferably in at least one tip of a robo hand or in medical technology and here in particular can be used in minimally invasive surgery (MIC). Using the force-moment according to the invention Principle underlying sensors can be enlarged in a The design of force-torque sensors, for example also in the gripping area of a mechanical gripping device device or in the wrist area of a robot or against possibly also for those used in space technology Gripping devices are used.

The invention is based on preferred embodiments tion forms with reference to the accompanying drawings explained in detail. Show it:

Figure 1 is a perspective view of a top view of the top of an embodiment of a force-moment sensor.

FIG. 2 shows a perspective view of the underside of the force-moment sensor of FIG. 1;

Fig. 3 is a plan view of the top of the force-moment sensor of Fig. 1 with the strain gauges applied, schematically as shown;

Fig. 4a in plan view about a third of the force-moment sensor of Figure 1 with applied strain gauges fen.

FIG. 4b shows in perspective a view of the underside of the Un part 4a shown in Figure a motor-torque sensor.

Figure 5 is a perspective illustration of a top view of the top of a further embodiment of a force-moment sensor.

Fig. 5a is a perspective view of part of the imple mentation form of the force-moment sensor of Figure 5 with end stop.

FIG. 6 is a perspective view of the underside of the force-moment sensor of FIG. 5;

FIG. 7a shows a top view of the upper side of approximately a quarter of the force-moment sensor of FIG. 5;

Fig. 7b in perspective a view of the underside of the reproduced in Fig. 7a portion of a force-moment sensor, and

Fig. 8 to 13 examples of possible circuit arrangements based on the principle of a Wheatstone bridge lead to half or quarter bridges connected strain gauges.

In Fig. 1 and Fig. 2, the top or bottom of a monolithic, approximately disc-shaped receiving part 20 is shown with a planar surface of a force-moment sensor, at least on the top, in a perspective representation. Here, the receiving part 20 consists of a first middle section 21 of high rigidity with first force introduction points 25 . In a miniaturized embodiment of a force-moment sensor, 25 dowel pins engage in the openings for force application, while a force application point 25 ', which is arranged in the center, serves for fastening by means of a screw. Furthermore, the receiving part 20 consists of at least three along the periphery formed second portions 22 ₁ to 22 _{3 of} medium rigidity, which are each divided into preferably equally large parts 22 ₁ a, 22 ₁ b to 22 ₃ a, 22 ₃ b, preferably at the outer ends in the transition areas ( 22 ₁ , 22 ₂ ; 22 ₂ , 22 ₃ and 22 ₃ , 22 ₁ ) between the adjoining second sections 22 ₁ to 22 ₃ , second force introduction points 26 are formed.

In the receiving part 20 are further formed between the section parts 22 a and 22 b of each second section 22 each lo-like relief sections 23 low stiffness. At least three starting from the first middle section 21 of the receiving part 20 , preferably ra dial extending connecting webs 24 are each connected to the relief sections 23 via connections not specified. These connecting webs 24 of the receiving part 20 have an average rigidity, which is achieved in that, as can be seen from the perspective illustration in FIG. 2, in the indirect region of each connecting web 23 a cross-section ## - shaped receptacle 27 is formed ,

So that the second sections 22 ₁ to 22 _{3 have} a medium stiffness, in the two section parts 22 ₁ a, 22 ₁ b to 22 ₃ a, 22 ₃ b in each case between the force application point 26 and the relief section 23, preferably at least one parallel provided to the flat top aligned opening 29 .

As can be seen from the top view of FIG. 3, respectively designed strain gauges 24 are arranged and applied on the flat surface of the section parts 22 a and 22 b of the second sections 22 and on the flat surface of the connecting webs 24 . Here, on the flat upper side of the connecting webs 24 , a pair of strain gauges is applied, which is aligned at 45 ° to a fictitious center line of the connecting webs 24 . In Fig. 3 indices of the strains / strains ε of the individual pairs are entered in the strain gauge pairs applied to the three webs 24 , namely 1 and 2, 3 and 4 as well as 5 and 6. With the indices 9 to 18 the respective strains / compressions ε of the strain gauges are entered, which are applied to the section parts 22 a, 22 b of the second sections 22 formed in the peripheral region.

In Fig. 3, a Cartesian coordinate system is indicated below the disc-shaped receiving part 20 . By means of the force applied to the connecting webs 24 strain Meßstrei fenpaare 1 and 2, 3 and 4 and 5 and 6 consisting of Strengthens th F _x and F _y, and bonding web from the moment M _z in the respective Ver 24 induced shear stresses can be detected who the. The mutually adjoining section parts 22 a and 22 b of adjacent second sections 22 of medium stiffness form elastic bending beams in such a way that, with the aid of the strain gauges, for example 9, 10 and 11, 12 bending stresses are determined and thus recorded, which result in moments M _x and M. _y and the force F _z .

Investigations by the inventors have shown that coupling of the measured values with respect to the loads introduced is very low. Since all measuring points, which are marked with the numbers 1 to 18 , are in one plane, the application of strain gauges is very easy. In addition to glued-on strain gauges, vapor-deposited or otherwise directly applied to the receiving part 20 of a force-moment sensor measuring grid can be used.

In Fig. 4a and 4b, a view of the top or in a perspective view, a view of the underside of a force-moment sensor is shown, the part 20 of a force-moment shown in Fig. 1 to 3 shown in Fig. 1 to 3 Sensor corresponds. Since only about a third of the force-moment sensor shown in FIGS . 1 to 3 is shown in FIGS . 4a and 4b, the corresponding sections, force introduction points and the applied strain gauges are provided with the same reference numerals provided with an A as in FIG . to 3 designated net 1.

The sensor shown in FIGS. 4a and 4b also has only a limited function compared to the sensors shown in FIGS. 1 to 3. For example, the forces F _y and F _z as well as a moment M _x can be determined and measured with the “one-third sensor” 20 ′ shown in FIGS. 4a and 4b.

In Fig. 5 and 6 each a perspective illustration of a top view of the top side or the underside of a further embodiment provide a force-moment sensor wiederge. In the embodiment of the force-moment sensor in FIGS. 5 and 6, in contrast to the embodiment of the force-moment sensor in FIGS. 1 to 3, not only are the at least three components required to determine three forces and three moments, but additionally formed a fourth component which is identical in structure and function, as a result of which the measuring system as a whole has a possibly beneficial redundancy. However, this redundant embodiment should only be implemented in an enlarged design. With a miniaturized force-moment sensor, it should be expedient to limit yourself to a version with the absolutely necessary, at least three components.

In the embodiment in FIGS. 5 and 6, too, the force-moment sensor is designed as a monolithic, approximately disk-shaped receiving part 30 with a flat surface. Here, the receiving part 30 in turn consists of a first mittle ren section 31 high rigidity with first force introduction lines 35th Through an opening 38 provided in the center of the receiving part 30 , supply lines or supply lines to the different strain gauges or devices attached to the sensor can optionally be guided in the larger design.

The monolithic receiving part 30 further consists of at least three second sections 32 of medium rigidity formed along the circumferential region, at the ends of which two second force introduction points, in the larger design, for example, each with its own force introduction point 36 , are formed. In the receiving part 30 between the second sections 32 and their outer ends 36 close to the force introduction points 36 tab-like relief sections 33 are formed. Furthermore, starting from the middle first section 31, four connecting webs 34 , which are connected to the second sections 32 in the monolithic structure. These connecting webs 34 in turn have an average rigidity, which can be realized, for example, in that in the central region of the connecting webs 34 a cross-section ## -shaped recess is formed, as can be seen from the bottom view in FIG. 6.

Although it is not shown in detail in the drawings, in the second embodiment of a force-moment sensor, respectively, appropriately designed strain gauges are applied to the flat surfaces of the second sections 32 and the connecting webs 34 , which in turn are based on the principle of a Wheatstone Bridge are connected, so that three forces F _x , F _y and F _z and three moments M _x , M _y and M _{z are again} to be determined from the measurement values thus obtained.

Also in the embodiment according to FIGS. 5 and 6, the two ten sections 32 are similar to the second portions 22 of the first embodiment is preferably the same size and preference as formed at equal angular intervals along the peripheral region. Furthermore, in the second sections 32, a required average stiffness can be achieved by forming at least two breakthroughs 39 aligned parallel to the flat surface of the force-moment sensor.

In Fig. 5a a portion, about a quarter of the receiving part 5 is shown 30 of the force-moment sensor of FIG.. In the 5a extending in the radial direction end stop difference to Fig. 5 in Fig. In the form of a dowel pin 40 pre see which is inserted in the inner flange 31 and protrudes with egg ner clearance fit in a bore 41 which ßenflansch Au 32 is formed, as the perspective Dar position in Fig. 5a can be seen. Corresponding end stops can also be provided between the other connecting webs 34 .

In Fig. 7a and 7b, the upper side or in a perspektivi rule representation, a plan view is shown on the underside of a force-moment sensor 30 '. The force-moment sensor 30 'corresponds to approximately a quarter of the disk-shaped receiving part 30 shown in FIGS. 5 and 6 of the force-moment sensor shown there. Since only a quarter of the force-moment sensor of FIGS. 5 and 6 is shown in FIGS . 7a and 7b, the corresponding sections and force introduction points are identified by the same reference numerals, but with an apostrophe.

Just like the sensor shown in FIGS . 4a and 4b, the sensor shown in FIGS . 7a and 7b also has only a limited function. For example, with the sensor 20 'shown in FIGS. 7a and 7b, the forces F _x or F _y and F _z as well as a moment M _x can be determined and measured with a certain inaccuracy.

On the section parts 22 a and 22 b and on the connecting webs 24 of the receiving part 20 of the first embodiment of a force-moment sensor, a total of eighteen strain gauges are provided, which are listed as pairs of strain gauges in the form of a Wheatstone bridge Half bridges are switched. Here, in Fig. 8, 10 and 12, the expansions / compressions ε ₁ to ε ₆ of the corresponding Deh-voltage Meßstreifenpaare in the two left branches eingetra gene, while the same dimensions each resistors R are provided in the two remaining branches of the half bridges. The voltages U ₁ to U ₃ obtained in the diagonal of the respective half bridges of FIGS. 8, 10 and 12 are entered in the corresponding figures below the corresponding half bridges relative to the applied voltage U _s .

In FIGS. 9, 11 and 13, the expansion / Stauchun are each gene of the Wheatstone bridge ε ε ₇ to ₁₈ of the respective strain Meßstreifenpaare in both branches entered. The voltages U ₄ to U ₆ obtained in each case in the diagonal of the respective bridges of FIGS. 9, 11 and 13 are indicated in the corresponding figures below the respective bridge in relation to the applied voltage U _s . Gain factors K are also listed in all equations.

LIST OF REFERENCE NUMBERS

20

receiving part

21

first section

22

second part

22

a,

22

b Section parts

23

relief sections

24

connecting web

25

first force application points

25

'' Force application point

26

second force application points

27

recess

28

strain

29

breakthrough

30

receiving part

31

first section

32

second part

32

a,

32

b ends of

32

33

relief sections

34

connecting web

35

first force application points

36

second force application points

37

recess

38

strain

39

breakthrough

40

end stop

41

drilling

Claims (16)

1. force-moment sensor, consisting of a monolithic disc-shaped receiving part ( 20 ) with a flat surface, the receiving part ( 20 ) from a first middle section ( 21 ) of high rigidity with first force introduction points ( 25 ), from at least three second sections ( 22 ₁ to 22 ₃ ) of medium stiffness formed along the circumferential area and each divided into two parts (22 ₁ a, 22 ₁ b to 22 ₃ a, 22 ₃ b), each with second force introduction points ( 26 ) in the transition area ( 22 ₁ , 22 ₂ ; 22 ₂ , 22 ₃ ; 22 ₃ , 22 ₁ ) between adjacent second sections ( 22 ₁ to 22 ₃ ), from between the section parts (22 ₁ a, 22 ₁ b to 22 ₃ a, 22 ₃ b ) each formed relief sections ( 23 ) of low stiffness and consists of at least three radially extending connecting webs ( 24 ) starting from the first section ( 21 ), each of which is connected via a connection to the relief sections ( 23 ) and which have an average rigidity, in that a cross-section ## - shaped recess ( 27 ) is formed on the underside in their central areas, and that on the flat surface of the section parts ( 22 a, 22 b) of the second sections ( 22 ) and the connecting webs ( 24 ) accordingly designed strain gauges ( 28 ) are applied, which are connected according to the principle of a Wheatstone bridge to quarter, half or full bridges in such a way that three forces (F _x , F _y , F _z ) and three moments (M _x , M _y , M _z ) can be determined. 2. Force-moment sensor, consisting of a monolithic disc-shaped receiving part ( 30 ) with a flat surface, the receiving part ( 30 ) from a first middle section ( 31 ) of high rigidity with first force introduction points ( 35 ), from at least three second sections ( 32 ) of medium rigidity formed along the circumferential area, at the ends of which second force introduction points ( 36 ) are formed, from relief sections ( 33 ) formed at the second sections ( 32 ) at the second force introduction points ( 36 ) and at least three of connecting webs ( 34 ) extending from the first section ( 31 ), which are connected to the second sections ( 32 ) and which have an average rigidity, by forming a cross section ## - shaped recess ( 37 ) on the underside in their central regions and that on the flat surfaces of the second sections ( 32 ) and the connecting webs ( 3rd 4 ) appropriately trained strain gauges are applied, which are connected according to the principle of a Wheatstone bridge to quarter, half or full bridges in such a way that three forces (F _x , F _y , F _z ) and three moments (M _x , M _y , M _z ) can be determined. 3. Force-moment sensor, consisting of a monolithic receiving part ( 20 ') with a flat surface, the receiving part ( 20 ') from a first section ( 21 ') of high rigidity with first force introduction points ( 25 '), from egg nem divided into two parts (22'a, 22'b) second section ( 22 ') of medium rigidity, each with a second force introduction point ( 26 ') at the outer end of each section part (22'a, 22'b), from between the two section parts (22'a, 22'b) formed relief sections ( 23 ') of low rigidity and consists of a connecting web ( 24 ') extending from the first section ( 21 '), which is connected via a connection to the relief sections ( 23 ' ) and which has an average rigidity, in that a cross-section ## - shaped recess ( 27 ') is formed on the underside in its central region, and that on the flat surface of the two section parts (22'a, 22' b) and the connecting st egs ( 24 ') correspondingly designed strain gauges ( 28 ') are applied, which are connected according to the principle of a Wheatstone bridge to quarter, half or full bridges in such a way that two forces (F _y , F _z ) can be determined. 4. force-moment sensor, consisting of a monolithic receiving part ( 30 ') with a flat surface, the receiving part from a first section ( 31 ') high rigidity with first force introduction points ( 35 '), from a second section ( 32 ') intermediate stiffness, to the En the second force introduction points (36') are formed from the second portion (32 ') in each case at the second force introduction points (36') discharge portions (33 shaped ') and of a first of the portion ( 31 ') extend from the connecting web ( 34 '), which is connected to the second section ( 32 ') and which has an average rigidity, in that on the underside in its central region a cross-section ## - shaped recess ( 37 ' ) and that correspondingly designed strain gauges are applied to the flat surface of the second section ( 32 ') and the connecting web ( 34 '), which are based on the principle of a Wheatstone Bridges are each connected to quarter, half or full bridges in such a way that two forces (F _y , F _z ) can be determined from the measurement values obtained in this way. 5. force-moment sensor according to one of claims 1 or 3, characterized in that the two parts (22a, 22b; 22'a, 22'b) of the second sections ( 22 , 22 ') of the same size and in be any angular distances along the circumferential region of the receiving part ( 20 ) are formed. 6. force-moment sensor according to one of claims 1 or 3, characterized in that the two parts (22a, 22b; 22'a, 22'b) of the second sections ( 22 , 22 ') of the same size and in the same Angular distances along the peripheral region of the receiving part ( 20 ) are formed. 7. force-moment sensor according to one of claims 1, 3, 5 or 6, characterized in that the two parts (22a, 22b; 22'a, 22'b) of the second sections ( 22 , 22 ') a middle Have rigidity by forming at least one opening ( 29 ; 29 ') parallel to the flat surface in each of the two parts between the force introduction point ( 26 , 26 ') and the relief section ( 23 , 23 '). 8. force-moment sensor according to one of claims 2 or 4, characterized in that the second sections ( 32 , 32 ') are of the same size and are formed at any angular intervals along the circumference of the receiving part ( 30 , 30 '). 9. force-moment sensor according to one of claims 2 or 4, characterized in that the second sections ( 32 , 32 ') of the same size and at equal angular intervals along the circumferential area of the receiving part ( 30 , 30 ') are formed. 10. force-moment sensor according to one of claims 2, 4, 8 or 9, characterized in that the second sections ( 32 , 32 ') have an average stiffness by in the second sections at least two parallel to the flat surface aligned openings ( 39 , 39 ') are formed. 11. Force-torque sensor according to one of claims 1 to 10, characterized in that on the top of the connecting webs ( 24 , 24 ', 34 , 34 ') each have a pair of strain gauges ( 1 , 2 ; 3 , 4 ; 5 ; 6 ) is applied at 45 ° to the fictitious center line of the connecting webs ( 24 , 24 ', 34 , 34 '). 12. Force-moment sensor according to one of claims 1, 2 or 5 to 11 for use in at least one fingertip of a ro boterhand. 13. Force-moment sensor according to one of claims 1, 2 or 5 to 11 for use in medical technology, in particular in the minimally invasive surgery (MIC). 14. Force-moment sensor according to one of claims 1, 2 or 5 to 11 for use in the gripping area of a mechanical gripping device setting up a robot. 15. Force-moment sensor according to one of claims 1, 2 or 5 to 11 for use in the wrist area of a robot. 16. force-moment sensor according to one of claims 1, 2 or 5 to 11 used in space technology Gripping devices.