Split-bridge force sensor

Abstract

To provide a force sensor.SOLUTION: A force sensor comprises: a beam having a longitudinal axis and a proximal end portion and a distal end portion; a first Wheatstone bridge disposed on a first face of the beam, and including multiple tension gauge resistors and multiple compression gauge resistors; a second Wheatstone bridge disposed on the first face of the beam, and including multiple tension gauge resistors and multiple compression gauge resistors. At least one tension gauge resistor and at least one compression gauge resistor from each of the first and second Wheatstone bridges are disposed at the proximal end portion of the beam. At least one tension gauge resistor and at least one compression gauge resistor from each of the first and second Wheatstone bridges is disposed at the distal end portion of the beam.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] (Priority Claim) This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 586,721, filed November 15, 2017, and U.S. Provisional Patent Application No. 62 / 586,166, filed November 14, 2017, each of which is incorporated herein by reference in its entirety. [Background technology]

[0002] Force sensing and feedback during minimally invasive surgical procedures can provide greater immersion, realism, and intuitiveness for the surgeon performing the procedure. To optimize haptic rendering and accuracy performance, force sensors may be placed on the surgical instrument as close as possible to the anatomical tissue interaction. One approach is to embed a force sensor at the distal end of the surgical instrument shaft, with electrical strain gauges formed on the force transducer through a printing or additive deposition process, to measure the strain applied to the surgical instrument.

[0003] FIG. 1 is an exemplary diagram showing a force sensor including a rectangular beam with four full Wheatstone bridges (full bridges). A bridge circuit is an electrical circuit topology in which two circuit branches (usually parallel to each other) are bridged by a third branch connected between the first two branches at a midpoint along them. Two full bridges are formed on each of two adjacent, orthogonal sides of the beam to measure forces perpendicular to the beam's longitudinal axis. The beam may be fixed to the distal portion of a surgical instrument shaft to sense forces perpendicular to the shaft's longitudinal axis. The force applied perpendicular to the side of the beam (i.e., the X or Y force) is determined by subtracting the force measurements determined by the full bridges at the proximal and distal ends of that side of the beam.

[0004] A force sensor may encounter a variety of different strain sources, including orthogonal forces, moments, off-axis forces, off-axis moments, compression / tension, torsion, ambient temperature, and temperature gradients, on the object to be measured. Each full bridge cancels out the stresses of temperature, torsion, off-axis forces, and off-axis moments. Each individual full bridge output represents the stress due to force, moment, and compression / tension. Subtracting the output value generated by a proximal full bridge formed on a side from the output value generated by a distal full bridge on the same side cancels out the moments and compression / tension, resulting in an output value representative of the orthogonal force on the object to be measured.

[0005] Force sensors in surgical instruments can be critical to ensuring patient safety. Therefore, force sensor error detection is sometimes required to protect against harm by detecting force sensor failure. One approach to error detection is to provide additional full bridges to generate redundant force measurements that can be compared to detect errors. However, due to limited space on the sides of the beam, forming additional full bridges on the sides is impractical. Furthermore, manufacturing processes are typically limited to forming bridges on at most two sides. Forming bridges on four sides significantly increases manufacturing costs. Summary of the Invention

[0006] In one aspect, a force sensor includes a beam having a longitudinal axis, a proximal end, and a distal end. A first Wheatstone bridge is disposed on a first surface of the beam and includes first and second tension gauge resistors and first and second compression gauge resistors. A second Wheatstone bridge is disposed on the first surface of the beam and includes third and fourth tension gauge resistors and third and fourth compression gauge resistors. The first and third tension gauge resistors and the first and third compression gauge resistors are disposed at the proximal end of the beam. The second and fourth tension gauge resistors and the second and fourth compression gauge resistors are disposed at the distal end of the beam.

[0007] In another aspect, a force sensor includes a beam having a longitudinal axis, a proximal end, and a distal end. A first tension gauge half bridge is disposed on a first surface of the beam and includes first and second tension gauge resistors. A second tension gauge half bridge is disposed on the first surface of the beam and includes third and fourth tension gauge resistors. A compression gauge half bridge is disposed on the first surface of the beam and includes first and second compression gauge resistors. The first and third tension gauge resistors and the first compression gauge resistor are disposed at the proximal end of the beam. The second and fourth tension gauge resistors and the second compression gauge resistor are disposed at the distal end of the beam.

[0008] In yet another aspect, a force sensor includes a beam having a longitudinal axis, a proximal end, and a distal end. A first bridge circuit is disposed on a first surface of the beam and includes a plurality of tension gauge resistors and at least one compression gauge resistor. A second bridge circuit is disposed on the first surface of the beam and includes a plurality of tension gauge resistors and at least one compression gauge resistor. At least one tension resistor from each of the first bridge circuit and the second bridge circuit and at least one compression gauge resistor from one of the first bridge and the second bridge are disposed at the proximal end of the beam. At least one tension resistor from each of the first bridge circuit and the second bridge circuit and at least one compression gauge resistor from the other of the first bridge and the second bridge are disposed at the distal end of the beam. [Brief explanation of the drawings]

[0009] The drawings are not necessarily drawn to scale, and in these drawings, like numbers may illustrate like elements in different views from one another. Like numbers with different letter suffixes may represent different instances of like elements. The drawings generally illustrate by way of example, but not by way of limitation, various embodiments discussed in this document.

[0010] [Figure 1] 1 is an exemplary drawing showing a force sensor including a rectangular beam with four full Wheatstone bridges (full bridges). [Figure 2] 1A-1C are exemplary side elevational views of a distal portion of a surgical instrument comprising an elongated shaft with an attached force sensor beam, according to some examples. [Figure 3] 1 is an exemplary perspective view of a force sensor beam having a pair of splitter bridge circuits formed on the beam side surfaces. FIG. [Figure 4A] FIG. 2 is an exemplary schematic diagram illustrating a first full-bridge circuit. [Figure 4B] FIG. 10 is an exemplary schematic diagram illustrating a second full-bridge circuit. [Figure 5] FIG. 1 is an exemplary perspective view of a force sensor beam having a beam side with a pair of interleaved splitter bridge circuits formed thereon. [Figure 6] 1 is an exemplary perspective view of a force sensor beam having a beam face side with a pair of interleaved split half-bridge circuits. FIG. [Figure 7] FIG. 2 is an exemplary schematic diagram illustrating three half-bridge circuits. [Figure 8] 7 is an exemplary side view of a beam showing the placement of gauge sensors for the interleaved three half-bridge example of FIG. 6. FIG. [Figure 9] 1 is an exemplary perspective view of a force sensor beam having a beam surface with a pair of interleaved split half-bridge circuits. FIG. [Figure 10] 10 is an exemplary side view illustrating the placement of gauge sensors for the interleaved three half-bridge example of FIG. 9. FIG. [Figure 11] FIG. 1 is an exemplary perspective view of a beam having a T-gauge (tension) and a C-gauge (compression) positioned along the neutral axis of the beam. [Figure 12] FIG. 1 is an exemplary perspective view of a beam having tension gauges R1 and R2 at the proximal and distal ends of the beam, respectively, positioned along the neutral axis of the beam. [Figure 13] 13 is an explanatory diagram showing a half-bridge circuit including R1 and R2 in FIG. 12. [Figure 14] FIG. 10 is an exemplary side view of a force applied to a cantilever beam showing strain measurements at a distance l from the location where the force is applied to the beam. [Figure 15] FIG. 10 is an exemplary side view of a force applied to a cantilever beam showing strain measurements at proximal and distal distances from the location where the force is applied to the beam. [Figure 16] FIG. 1 is a side view of a cantilever beam. [Figure 17A] FIG. 10 is a side view of a beam with a Wheatstone bridge disposed at its proximal end. [Figure 17B] FIG. 17B is a schematic diagram of the Wheatstone bridge circuit of FIG. 17A. [Figure 18] FIG. 1 is a side view of a beam with a split Wheatstone bridge having tension gauge resistor R1 and compression gauge resistor R2. [Figure 19] FIG. 1 illustrates an example force sensor including a beam with two split full bridge circuits. [Figure 20A] FIG. 1 is an exemplary simplified block diagram illustrating mechanically separated leads extending between strain gauge elements of two proximal split bridge circuit halves and strain gauge elements of two distal split bridge circuit halves. [Figure 20B] FIG. 20B is an illustration showing certain details of a first example arrangement of strain gauge elements of the example sensor of FIG. 20A. [Figure 20C] FIG. 20B is an illustration showing certain details of a second example arrangement of strain gauge elements of the exemplary sensor of FIG. 20A. [Figure 21] FIG. 10 is an illustration showing a set of proximal and distal connection pads with matching areas for the input and measurement pads. [Figure 22] FIG. 10 is an exemplary diagram showing a set of proximal and distal connection pads where the measurement pads have a larger area than the input pads. [Figure 23] FIG. 1 is an exemplary circuit schematic illustrating a force sensor including exemplary first and second divider bridge circuits disposed on a beam that share a common excitation voltage input. [Figure 24] FIG. 24 is an example diagram illustrating tap leads for the example double divider bridge circuit of FIG. 23. DETAILED DESCRIPTION OF THE INVENTION

[0011] 2 is an exemplary side elevation view of a distal portion of a surgical instrument 202, shown partially cut away, comprising an elongated shaft 204 with a force sensor beam 206 attached, according to some examples. The surgical instrument 202 includes an end effector 208, which may include, for example, an articulatable jaw. During a surgical procedure, the end effector 208 contacts anatomical tissue, which generates forces in the X, Y, or Z directions and a moment M about an axis in the Y direction. Y The force sensor 206, which includes a longitudinal axis 210, can be used to measure X and Y forces perpendicular to the longitudinal axis 210.

[0012] 3 is an exemplary perspective view of a force sensor beam 206 having a beam side 212 with a pair of split bridge circuits formed thereon. The bridge circuits are split, with a portion of each bridge circuit located at the proximal end of the beam and a portion of the bridge circuit located at the distal end of the beam. More specifically, in the example of FIG. 3, the bridge circuits have strain gauge resistors R formed thereon and aligned along a neutral axis (equidistant from the sides of the beam) at the proximal beam end 206P, according to some examples. C1 , R C3 , R T1 , R T3 and a strain gauge resistor R aligned along the neutral axis at the distal beam end 206D. C2 , R C4 , R T2 , R T4 , and 214. Identical pairs (not shown) of interleaved split full bridges are formed on adjacent orthogonal beam sides 214. The pair of interleaved split full bridges formed on adjacent orthogonal sides are configured to measure forces perpendicular to the longitudinal axis 210 of the beam 206, which may impart tensile strain to the beam. It will be appreciated that alignment of the gauge resistors along the neutral axis reduces the effects of off-axis loads, since the neutral axis is insensitive to off-axis forces and moments.

[0013] Figure 4A shows the input voltage V in and a first output voltage V O1 Tensile strain gauge resistor R coupled to produce T1 and R T2 and a compression strain gauge resistor R C1 and R C2 4B is an example schematic diagram illustrating a first split full-bridge bridge of a pair including a compression gauge half-bridge with an input voltage V in and a second output voltage V O2 Tensile strain gauge resistor R coupled to produce T3 and R T4 and a compression strain gauge resistor R C3 and R C4 FIG. 10 is an exemplary schematic diagram illustrating a second split full bridge of the pair including a compression gauge half bridge having a

[0014] As explained in more detail below, each tensile strain gauge resistor R T1 -R T4 and each compression strain gauge resistor R C1 -R C4 The compression strain gauge resistor R includes a plurality of elongated resistor portions aligned in parallel and joined end to end to form a serpentine or serpentine configuration. C1 -R C4 The elongated portion of the tensile strain gauge resistor R may be aligned parallel to the longitudinal axis 210 of the beam to sense compressive strain on the beam 206. T1 -R T4 The elongated portion of the sensor may be aligned perpendicular to the longitudinal axis of the beam to sense tensile strain on the beam.

[0015] 3, each interleaved split full bridge has a tension gauge sensor resistor and a compression gauge sensor resistor located at the proximal end 206P of the beam 206. Each interleaved split full bridge also has a tension gauge sensor and a compression gauge sensor located at the distal end 206D of the beam 206. Specifically, strain gauge resistors R T1 , R T3 , R C1 and R C3 is located at the proximal end 206P of the beam 206, and a strain gauge resistor R T2 , R T4 , R C2 and R C4 is disposed at the distal end 206D of the beam 206. Additionally, a strain gauge resistor R T1 The elongated portions of the strain gauge resistors R are co-located and occupy the same longitudinal area of the beam. T3 (similar to Figure 8 in detail). Strain gauge resistor R C1 The elongated portions of the strain gauge resistors R are aligned so that they are co-located and occupy the same longitudinal area of the beam. C3 (Details similar to Figure 8) Interleaved compression gauge resistors R C1 , R C3 is an interleaved tension resistor R T1 , R T3 The strain gauge resistor R is placed closer to the proximal end of the beam than the T2 The elongated portions of the strain gauge resistors R are aligned so that they are co-located and occupy the same longitudinal area of the beam. T4 (Details similar to Figure 8) The strain gauge resistor R C3 The elongated portions of the strain gauge resistors R are aligned so that they are co-located and occupy the same longitudinal area of the beam. C4 (Details similar to Figure 8) Interleaved compression gauge resistors R C2 , R C4 is an interleaved tension resistor R T2 , R T4The interleaving of the strain gauge resistors in the example of Figure 3 will be better understood from an explanation with reference to the example of an interleaved half bridge shown in the illustrative drawing of Figure 8.

[0016] FIG. 5 illustrates strain gauge resistors R, each aligned along the neutral axis at the proximal beam end 206P, according to some examples. C1 , R C3 , R T1 , R T3 and strain gauge resistors R each aligned along the neutral axis at distal beam end 206D. C2 , R C4 , R T2 , R T4 1 is an exemplary perspective view of a force sensor beam 206 having a beam side 212 with a staggered split full bridge formed thereon, the beam having four elongated rectangular sides and a rectangular end face. Identical pairs of staggered split full bridges (not shown) are formed on adjacent orthogonal beam sides 214. The pairs of staggered split full bridges formed on adjacent orthogonal sides are configured to measure forces normal to the longitudinal axis of the beam, which may impart a tensile strain to the beam.

[0017] The exemplary schematic diagrams of Figures 4A-4B above represent the first and second full bridges of the interleaved split full bridge of Figure 5. Each interleaved split full bridge has a tension gauge sensor resistor and a compression gauge sensor resistor located at the proximal end 206P of the beam 206. Each full bridge also has a tension gauge sensor and a compression gauge sensor located at the distal end 206D of the beam 206. Specifically, strain gauge resistors R T1 , R T3 , R C1 and R C3 is located at the proximal end 206P of the beam 206, and a strain gauge resistor R T2 , R T4 , R C2 and R C4are located at the distal end 206D of the beam 206. However, unlike the interleaved split full-bridge pairs of FIG. 3, the split interleaved split bridge of FIG. 5 is arranged in an "interleaved" arrangement, where the strain gauge pairs of each full-bridge are located adjacent to each other at opposite ends of the beam. The strain gauge resistors R of the first interleaved split full-bridge T1 and R C1 are positioned adjacent to each other at the proximal end 206P of the beam 206. The strain gauge resistors R of the second interleaved split full bridge T3 and R C3 are disposed adjacent to each other at the proximal end 206P of the beam 206, and strain gauge resistors R T1 and R C1 Similarly, the strain gauge resistor R of the first interleaved split full bridge is offset further from the proximal end 206P than the T2 and R C2 are positioned adjacent to each other at the distal end 206D of the beam 206. The second interleaved split full-bridge strain gauge resistors R T4 and R C4 are positioned adjacent to each other at the distal end 206D, and strain gauge resistors R T2 and R C2 206D.

[0018] Both the interleaved split full-bridge and the interleaved split full-bridge have redundant first and second output voltages, V O1 and V O2, which produces a redundant first output voltage V. The longitudinal distribution of the tension and compression gauge sensor resistors in the interleaved split full-bridge pair of FIG. 3 and the interleaved split full-bridge pair of FIG. 5 cancels and substantially eliminates noise that may be caused by forces from other sources, such as off-axis load moments in any of three directions and forces in any of two orthogonal directions relative to the force being measured. Furthermore, each of the interleaved split full-bridge pair and each of the interleaved split full-bridge pair includes both tension and compression strain gauge resistors that are configured to substantially cancel the effects of temperature variations. Furthermore, the interleaving of these strain gauge resistors in the example of FIG. 3 ensures that they measure strain at the same location on the beam, thereby providing a consistent measurement of the redundant first output voltage V, even with temperature variations along the length of the beam. O1 and the second output voltage V O2 have matching values.

[0019] Therefore, the distribution of the gauge sensor resistors of each full bridge between the proximal and distal ends of the beam determines the first and second output signals V O1 and V O2 The first and second output signal values V are then filtered out to remove the effects of noise from other sources of force and to cancel out the effects of temperature so that the first and second output signal values V O1 and V O2 may be compared to determine whether they have different values. O1 and V O2 A determination that the values of σ differ provides an indication of an error due to, for example, damage to the force sensor.

[0020] 6 is an exemplary perspective view of a force sensor beam 206 having a beam face 212 with a pair of interleaved split half-Wheatstone bridges (half-bridges), each with a tension gauge sensor resistor formed at the proximal and distal ends of the beam 206, and a shared half-bridge with a compression gauge resistor formed at the proximal and distal ends of the beam, according to some examples. A first tension gauge half-bridge has a strain gauge resistor R at its proximal end 206P. T1and a strain gauge resistor R at the distal end 206D. T2 (similar in detail to FIG. 8). A second tension gauge half bridge includes a strain gauge resistor R at its proximal end 206P. T3 and a strain gauge resistor R at the distal end 206D. T4 (similar in detail to Figure 8). The compression gauge half bridge has a strain gauge resistor R at its proximal end. C1 and a strain gauge resistor R at the distal end 206D. C2 Identical pairs of interleaved half bridges (not shown) with tension gauge sensor resistors and identical shared half bridges (not shown) with compression gauge sensor resistors are formed on adjacent orthogonal beam faces 214. The pairs of interleaved split half bridges formed on adjacent orthogonal faces are configured to measure forces perpendicular to the longitudinal axis 210 of the beam 206, which may impart a tensile strain to the beam. The shared compression gauge sensor resistors formed on adjacent orthogonal beam faces are configured to measure forces parallel to the longitudinal axis of the beam, which may impart a compressive strain to the beam 206.

[0021] 7 is an exemplary schematic diagram illustrating three half-bridges. The first tension gauge half-bridge 602 includes a tension strain gauge resistor R aligned along the neutral axis. T1 and R T2 The second tension gauge half bridge 604 includes a tension strain gauge resistor R aligned along the neutral axis. T3 and R T4 The compression half bridge 606 includes a compression strain gauge resistor R aligned along the neutral axis. C1 and R C2 Each of the first and second tension gauge half bridges 602, 604 and the compression gauge half bridge 606 receives an input voltage V in The first strain gauge half bridge 602 is coupled to receive a first tension output V O1 The second strain gauge half bridge 604 is coupled to provide a second tension output V O3 The compression gauge half bridge 606 is coupled to provide a compression force output V O2Each resistor R T1 -R T4 and R C1 -R C2 The resistor R comprises a plurality of parallel elongated sections aligned in parallel and joined end to end to form a serpentine or snake-like shape. C1 -R C2 The elongated portion of resistor R is aligned parallel to the longitudinal axis 210 of beam 206 and acts as a compression gauge sensor. T1 -R T4 The elongated portion of the is aligned perpendicular to the longitudinal axis 210 of the beam 206 and acts as a tension gauge sensor.

[0022] 6, each interleaved split half bridge has a tension gauge sensor resistor and a shared compression gauge sensor resistor located at the proximal end 206P of the beam 206. Each interleaved split half bridge also has a tension gauge sensor and a shared compression gauge sensor located at the distal end 206D of the beam 206. Specifically, strain gauge resistor R T1 , R C1 and R T3 is located at the proximal end 206P of the beam 206, and a strain gauge resistor R T2 , R C2 and R T4 is disposed at the distal end 206D of the beam 206.

[0023] FIG. 8 shows a side view of the beam showing the placement of gauge sensors for the interleaved three half-bridge example of FIG. 6, shown in dashed lines. Strain gauge resistors R T1 The long and thin part of L T1 The strain gauge resistors R are arranged in the same location and occupy the same longitudinal area of the beam. T3 The long and thin part of L T3 Interleaved strain gauge resistor R T1 and R T3 is the compression gauge resistor R from the proximal end of the beam. C1 The lead extends between the proximal and distal ends. T1、T2is located at the proximal end 206P. T1 and R located at the distal end 206D. T2 and strain gauge resistor R T2 The long and thin part of L T2 The strain gauge resistors R are arranged in the same location and occupy the same longitudinal area of the beam. T4 The long and thin part of L T4 Interleaved strain gauge resistor R T2 and R T4 is the compression gauge resistor R C2 The lead extends between the proximal and distal ends of the beam. T3、T4 is located at the proximal end 206P. T3 and R located at the distal end 206D. T4 A lead extending between the proximal end and the distal end C1、C2 is located at the proximal end 206P. C1 and R located at the distal end 206D. C2 Combine with.

[0024] 9 is an exemplary perspective view of a force sensor beam 206 having a beam face 212 with interleaved split half bridges, each with a tension gauge sensor resistor formed at the proximal and distal ends of the beam, and a shared half bridge with a compression gauge resistor formed at the proximal and distal ends of the beam, according to some examples. The schematic diagram of FIG. 7 also represents three interleaved half bridges of FIG. 9. The first tension gauge half bridge has a strain gauge resistor R at its proximal end 206P. T1 and a strain gauge resistor R at the distal end 206D. T2 The second tension gauge half bridge includes a strain gauge resistor R at the proximal end 206P. T3 and a strain gauge resistor R at the distal end 206D. T4 The compression gauge half bridge includes a strain gauge resistor R at the proximal end. C1 and a strain gauge resistor R at the distal end 206D. C2Identical pairs of interleaved split half-bridges (not shown) with tension gauge sensor resistors and identical shared half-bridges (not shown) with compression gauge sensor resistors are formed on adjacent orthogonal beam faces 214. The pairs of interleaved split half-bridges formed on adjacent orthogonal faces are configured to measure forces perpendicular to the longitudinal axis 210 of the beam 206, which may impart a tensile strain to the beam 206. The shared compression gauge sensor resistors formed on adjacent orthogonal beam faces are configured to measure forces parallel to the longitudinal axis 210 of the beam, which may impart a compressive strain to the beam 206.

[0025] 10 is an exemplary side view illustrating the placement of gauge sensors in the interleaved three half-bridge example of FIG. 9. The first tension gauge resistor half-bridge has a tension strain gauge resistor R aligned along the neutral axis. T1 and R T2 The second tension gauge resistor half bridge includes a tension strain gauge resistor R aligned along the neutral axis. T3 and R T4 The compression gauge resistor half bridge includes a compression strain gauge resistor R aligned along the neutral axis. C1 and R C2 A first compression gauge resistor R C1 is the first tension gauge resistor R T1 and a third tension gauge resistor R T3 A first tension gauge resistor R is placed at the proximal end of the beam between T1 is the third tension gauge resistor R T3 A second compression gauge resistor R is located closer to the proximal end of the beam than the first compression gauge resistor R. C2 is the second tension gauge resistor R T2 and the fourth tension gauge resistor R T4 A fourth tension gauge resistor R is placed at the distal end of the beam between T4 is the second tension gauge resistor R T2 The lead extends between the proximal and distal ends of the beam. T1、T2 is located at the proximal end 206P. T1 and R located at the distal end 206D. T2A lead extending between the proximal end and the distal end T3、T4 is located at the proximal end 206P. T3 and R located at the distal end 206D. T4 The lead extends between the proximal end and the distal end. C1、C2 is located at the proximal end 206P. C1 and R located at the distal end 206D. C2 Combine with.

[0026] Therefore, both the interleaved split half-bridge and the interleaved split half-bridge have redundant first and second tension output voltages V O1 and V O3 The longitudinal distribution of the tension and compression gage sensor resistors in the interleaved split half-bridge pair of FIG. 6 and the interleaved split half-bridge pair of FIG. 9 cancels and substantially eliminates noise that may be caused by forces from other sources, such as off-axis load moments in any of three directions relative to the force being measured and forces in either of two orthogonal directions. Furthermore, in the interleaved half-bridge example of FIG. 6, the interleaving of the strain gage resistors ensures that they measure strain at the same location on the beam, which results in a redundant first output voltage V O1 and the third output voltage V O3 will have consistent values even with temperature variations along the length of the beam.

[0027] In arriving at the present invention, the inventors realized that each half bridge (both tension gauge half bridges and compression gauge half bridges) cancels the following stresses: moment, off-axis force, off-axis moment, compression / tension, torsion, and ambient temperature. The inventors also realized that each half bridge output includes the following: force and gradient temperature. The inventor further states that V O If is the output of the half-bridge, then we know that

number

[0028] Next, (ε p -ε d ) cancels out: moment, off-axis force, off-axis moment, compression / tension, torsion, and ambient temperature, then subtracts the "T gauge" half-bridge output and the "C gauge" half-bridge output to cancel out gradient temperatures.

[0029] V O1 is the output of the half bridge at "T gauge" and V O2 If is the output of the half bridge at "C gauge", then V O1 -V O2 The subtraction cancels out the ambient temperature and gradient temperature, and only the final output after subtraction is the "Force" that is sought.

[0030] For the split half-bridge example of FIGS. 6 and 9, the redundant comparison can be performed as follows:

[0031] The redundant comparison is made between the half-bridge measurement V O1 , V O2 and V O3 This is done after extracting the force signal and the temperature difference signal from the For example, for the X-axis (denoted by "x"), Force1 _x and deltaT1 _x To get V O1_x and V O2_x You can use Force2 _x and deltaT2 _x To get V O3_x and V O2_x You can use For the Y-axis (denoted by "y"), Force1 _y and deltaT1 _y To get V O1_y and V O2_y You can use Force2 _y and deltaT2 _y To get V O2_y and V O2_y You can use For redundancy checks, Force _x :Force1 _x and Force2 _x Check if the matches, Force _y :Force1 _y and Force2 _y Check if it matches, deltaT:deltaT1 _x and deltaT1 _y Check if the match.

[0032] These comparison checks cover any failure of the gauge.

[0033] deltaT2 _x and deltaT2 _y are a kind of throwaway terms because they do not provide any additional information.

[0034] The mathematics used to calculate force and deltaT from the voltage output is as follows:

number

number

[0035] Therefore, the distribution of the gauge sensor resistors of each tension gauge half bridge between the proximal and distal ends of the beam eliminates the effects of noise from other force sources and cancels the effects of temperature, thereby reducing the magnitude of the first and second tension gauge force output signals VO1 and V O3 generate the same redundant value. The first and second tensile gauge force output signal values V O1 and V O3 may be compared to determine whether they have different values. O1 and V O3 A determination that σ has a different value provides an indication of an error due to, for example, damage to the force sensor.

[0036] The redundant temperature values are the compression output values V generated by the compression gauge half-bridges formed in adjacent orthogonal planes. O2 The compressed output value V produced by the half bridges formed in adjacent orthogonal planes is given by O2 may be compared to determine whether they have different values. A determination that compression gauge half bridges on adjacent orthogonal planes have different values provides an indication of an error due to, for example, damage to the force sensor.

[0037] Proof

[0038] A. Determine Tgauge strain and Cgauge strain: FIG. 11 is an exemplary perspective view of a beam with a T-gauge (tension) and a C-gauge (compression) positioned along the neutral axis of the beam.

[0039] Values used to determine the change in force and temperature include: F g : Force along the sensing surface l: Position of applied force M: Moment applied perpendicular to the detection surface F Z : Force applied parallel to the neutral axis I: Moment of inertia A: Area or cross-sectional area CTE: Coefficient of thermal expansion ΔT: Temperature change ε: strain ρ: Poisson's ratio T-gauge strain measurement method:

number

number

[0040] B. Determination of Force and ΔT: Figure 12 is an exemplary perspective view of a beam with tension gauges R1 and R2 at the proximal and distal ends, respectively, positioned along the neutral axis of the beam. Figure 13 is an exemplary schematic diagram showing a half-bridge circuit including R1 and R2 of Figure 12.

[0041] For the half bridge in Figure 12-13, using the T-gauge strain measurements described above, R1, R2, and V in Based on V O can be calculated.

number

number

number

[0042] The nominal resistance of both gauges is the same R value under no load. The change in resistance depending on the strain experienced by the gauge is multiplied by the gauge factor. For small resistance changes, a first order approximation gives:

number

[0043] Regarding power V O The distortion equation can be used instead to obtain

number

[0044] Similarly, the equation for the half-bridge was obtained using a compression (C) gauge.

number

[0045] Using the equations for C gauge and T gauge, F ll and ΔT = (ΔT1 - ΔT2) can be solved.

number

number

number

number

[0046] C. Basic Force Measurement Using Strain: FIG. 14 is an exemplary side view of a force applied to a cantilever beam showing strain measurements at a distance l from the location where the force is applied to the beam.

[0047] The strain equation for a normal force applied to the distal end of the cantilever is:

number

[0048] It can be seen that the strain equation not only depends on the distance l from the sensing point, but also on the applied force F. Therefore, to be able to measure the applied force, a second measurement is needed to remove the dependency on "l". The most obvious way to do this is to measure the strain at different points along the beam.

[0049] Figure 15 shows the force at a proximal distance l from the point where the force is applied to the beam. prox and distal distance ldist 1 is an exemplary side view of a force applied to a cantilever beam showing strain measurements at . As a result, the following can be obtained:

number

number

[0050] Then, subtract the two measurements to get:

number

[0051] The difference in distance is a known quantity, the distance between the two sensed points.

[0052] D. Force measurement under noise sources FIG. 16 is a side view of a cantilever beam.

[0053] In a typical force measurement scenario, there will be noise sources / signals that we are not interested in but still produce measurable strain on the beam, which we will detect, resulting in an erroneous estimation of the applied force. Other sources of strain that may be present are: Two orthogonal forces Moments in all three directions Temperature changes is.

[0054] If the reference frame is chosen so that the force we want to measure is directed along the X axis, An unwanted strain source to measure is force (F y , F z ), moment (M x , M y , M z ) and temperature (ΔT).

[0055] Therefore, the most general strain equation for a point sensing element on a cantilever beam oriented parallel to the neutral axis is:

number

number

[0056] As can be seen from the above equation, point measurements of strain are dependent on many strain sources, and the act of subtracting proximal and distal measurements eliminates several sources of strain as common modes. The following are eliminated: ·Force:F z Moment: M y , M z

[0057] If the sensing points / elements are placed symmetrically around the neutral axis (d=0), the following will not affect the strain measurements: ·Force:F y Moment: M x

[0058] Therefore, the uncompensated strain source is temperature changes. The most common method of compensating for temperature is to use a Wheatstone bridge configuration that uses "C" (compression) and "T" (tension) gauges to locally remove strain from temperature changes.

[0059] Figure 17A is a side view of a beam with a Wheatstone bridge disposed at its proximal end, and Figure 17B is a schematic diagram of the Wheatstone bridge circuit of Figure 17A.

[0060] The output of the Wheatstone bridge is:

number

[0061] The resistance-strain relationship of the gauge is as follows:

number

[0062] If the nominal resistance of all gauges is the same and we substitute the strain-resistance relationship and make a first approximation, we obtain

number

[0063] F x When is applied, the above equation can be transformed into the following form:

number

[0064] Thus, an output signal is obtained that is proportional to the applied force.

[0065] If there is a temperature change, the strain seen by all gauges will be the same and the output will be zero, which means that the temperature change is locally compensated.

[0066] Therefore, to measure an applied force in the sensing direction (X-axis), two Wheatstone bridges are required, located near the proximal and distal ends of the beam.

[0067] E. Force Measurement Using a Single Wheatstone Bridge Figure 18 is a side view of a beam comprising a split Wheatstone bridge having tension and compression gauge resistors R1, R2 at its proximal end positioned along the neutral axis, and tension and compression gauge resistors R3, R4 at its distal end positioned along the neutral axis. The schematic diagram of Figure 17B is applicable to the split bridge of Figure 18.

[0068] Looking at a trivial design, we compensate for temperature locally, measure two signals, and subtract the two signals externally to get the applied force, but the Wheatstone bridge equation structure has the ability to subtract signals internally, so we can use this to our advantage, and we can position the gauges so that instead of the temperature being compensated locally, we can compensate for the temperature effect globally.

[0069] The temperature change seen at each measurement point can be decomposed into the ambient temperature change, which is the same everywhere, and the temperature difference, which is the temperature difference between the ambient temperature and the temperature at that point. The ambient temperature change is ultimately the common mode, and the mere act of subtracting the proximal and distal signals removes its effect.

[0070] In the above configuration, the output signal is obtained as follows.

number

[0071] If there is no temperature difference, R1 and R2 are tension gauges, R3 and R4 are compression gauges, and the relationship to the applied force is -ρ r It can be seen that R1 and R2 together measure the applied force, and R3 and R4 similarly measure the applied force, since R1 varies with R2. Therefore, the overall equation becomes:

number

number

[0072] The same configuration for temperature difference has different results: R1 and R2 measure the effect of the temperature difference between the proximal and distal gauges, and R3 and R4 do the same. Even though the two pairs are different gauge types, they have the same sensitivity to strain due to temperature changes.

number

number

[0073] Thus, the "C" gauge can be roughly considered a temperature compensated gauge and the "T" gauge a measuring gauge.

[0074] 19 is an exemplary diagram illustrating a force sensor 1900 including a beam 1902 with two split full bridge circuits. The beam 1902 includes a proximal end 1902P, a distal end 1902D, and a central section therebetween. The first split bridge circuit includes a strain gauge resistor R C1 , R C3 , R T1 , R T3 The first bridge circuit includes a compressive strain gauge resistor R disposed at the proximal end of the beam. C1 and tension gauge resistor R T1 and a compressive strain gauge resistor R placed at the distal end of the beam. C3 and tension gauge resistor R T3 The second divider bridge circuit is connected to the strain gauge resistor R C2 , R C4 , R T2 , R T4The second bridge circuit includes a compressive strain gauge resistor R located at the proximal end of the beam. C2 and tension gauge resistor R T2 and a compressive strain gauge resistor R placed at the distal end of the beam. C4 and tension gauge resistor R T4 and is divided into

[0075] Conductive measurement output leads L1-L4 and input signal leads L5-L6 disposed on the beam electrically couple the strain gauge resistors as shown. Measurement output lead L1 is connected to node V O1 - With R T1 and R T3 The measurement output lead L2 is disposed to extend integrally with the proximal, central and distal portions of the beam to electrically couple the O1 + In R C1 and R C3 The measurement output lead L3 is disposed to extend integrally with the proximal, central and distal portions of the beam to electrically couple the O2 + In R C2 and R C4 The measurement output lead L4 is arranged to extend integrally with the beam to electrically couple to node V. O2 - In R T2 and R T4 The input signal lead L5 is arranged to extend integrally with the beam to electrically couple to the node V. I + In R C1 , R C2 , R T1 and R T2 The input signal lead L6 extends into the proximal portion of the beam to electrically couple to node V. I - In R C3 , R C4 , R T3 and R T4 The leads L1-L6 extend into the distal portion of the beam for electrically coupling the leads L1-L6 to the beam. The leads L1-L6 are integrally disposed with the beam and are mechanically coupled to the beam.

[0076] R T1 , R T3 , R C1 , R C3 The input tap node V is connected to I + , and R T2 , R T4 , R C2 , R C4 V coupled to I - R acts as an input signal node and is coupled to receive the positive and negative polarities of the input excitation signal. T1 , R T3 Each junction of, and R C1 , R C3 Measurement tap node V at the junction of O1 - and V O1 + serves as an output measurement signal node and is coupled to provide an output measurement signal indicative of distortion. T2 , R T4 Each junction of, and R C2 , R C4 Measurement tap node V at the junction of O2 - and V O2 + serves as an output measurement signal node and is coupled to provide an output measurement signal indicative of the distortion.

[0077] Because each split bridge includes both a strain gauge resistor located at the proximal end of the beam and a strain gauge resistor located at the distal end of the beam, the leads L1-L6 electrically coupling the resistors of each bridge are relatively long. For example, the leads coupling the resistors of the first and second split bridges of Figure 19 are relatively long compared to the leads used to couple the resistors of the non-split bridge circuit of the exemplary bridge of Figure 1, in which each bridge is located entirely at either the proximal end of the beam or the distal end of the beam.

[0078] A split bridge circuit can introduce undesirable amounts of unbalanced lead resistance between the strain gauges because the gauges are distributed over beam positions over a long distance compared to the size of the strain gauges. The lead resistance affects the accuracy of the sensor measurement and introduces cross-coupling and temperature-dependent offsets.

[0079] More specifically, the conductive leads are integrally formed on the beam via a deposition and etching process that produces the strain gauge. Preferably, the leads do not change electrical properties in response to, for example, changes in temperature or force applied to the beam. However, the conductive leads that extend along the beam to couple the active resistive strain gauge at the opposite end of the beam experience strain as the beam distorts in response to force applied to the beam, which changes the resistance of the conductive wire. In some instances, the length of the leads may be comparable in magnitude to the overall length of the conductor line segments that make up the serpentine-shaped resistive strain gauge element. Because the electrical connection wires are not intended to act as active resistive elements in a bridge circuit, changes in the resistance of the conductive wires can cause distortion in strain measurements. Therefore, a balance must be struck between reducing lead resistance and minimizing any remaining lead resistance.

[0080] 20A-20B are diagrams illustrating an example force sensor 2000 including a beam 2002 having a neutral axis 2004 and including two split full-bridge circuits with split bridge halves electrically coupled by measurement output leads L1'-L4', and with electrically coupled input leads L5-L6 including a beam 2002 mechanically separated from the beam 2002. FIG. C1 -R C4 and R T1 -R T4 in simplified block diagram form, showing the mechanically isolated measurement output leads L1'-L4' extending between the strain gauge elements of the split bridge halves, and the node V I + In R C1 , R C2 , R T1 and RT2 and the input signal lead L5' electrically couples the node V I - In R C3 , R C4 , R T3 and R T4 FIG. 20B shows an input signal lead L6' electrically coupling the strain gauge element R of the exemplary sensor of FIG. C1 -R C4 and R T1 -R T4 20C shows details of a first exemplary arrangement of strain gauge elements R of the exemplary sensor 2000 of FIG. C1 -R C4 and R T1 -R T4 20B-20C show details of a second exemplary arrangement of the 1000 Ω 1 ...

[0081] Referring to FIG. 20A, the mechanically decoupled measurement output leads L1'-L4' in FIG. 20A correspond to the correspondingly labeled integral measurement output leads L1'-L4' in FIG. 19. The mechanically decoupled leads L1'-L4' are routed out off the beam, and one example of this implementation would have leads L1'-L6' that are part of a flex circuit / cable wire-bonded to the beam. The flex cable is attached with sufficient slack so that deflection of the beam due to applied forces does not cause strain on the flex circuit / cable; further, the leads on the flex circuit can be made of a lower resistivity electrical material such as copper compared to a higher resistivity thin-film material such as nichrome (an alloy of nickel and chromium), thus providing a lower magnitude of lead resistance. Thus, the leads L1'-L4' electrically coupling the strain gauge elements are mechanically isolated from strains imparted during deflection of the beam 2002 due to a deflecting force (not shown) applied to the beam.

[0082] Referring to the exemplary two-bridge configuration of Figure 20B, except for the lead changes, the configuration of the force sensor 2000 of Figure 20B is identical to the configuration of the sensor of Figure 19. The extended measurement output leads L1'-L4' and input leads L5-L6 are mechanically decoupled from the beam and are connected to shorter integral proximal lead segments X P1 -X P6 and a shorter integral distal lead portion X D1 -X D6 is disposed integrally with the beam, resulting in less stress being applied to the leads during mechanical deflection of the beam, and therefore less distortion in the strain measurements when compared to the exemplary sensor of FIG.

[0083] The mechanically isolated lead wire L1' is connected to the V of the proximal and distal bridge halves. O1 - At the node labeled R C1 and R C3 The insulated lead wires L2' are arranged to extend mechanically isolated from the beam between the proximal, central, and distal portions of the beam so as to electrically couple the V O1 + At the node labeled R T1 and R T3 The insulated lead wires L3' are positioned to extend between the proximal, central, and distal portions of the beam, but are mechanically isolated from the beam, to electrically couple the V of the proximal and distal bridge halves. O2 - At the node labeled R C2 and R C4 The insulated lead wires L4' are positioned to extend mechanically isolated from the beam between the proximal, central, and distal portions of the beam so as to electrically couple the V O2 + At the node labeled R T2 and R T4 The proximal lead element X is disposed to extend between the proximal, central, and distal portions of the beam while being mechanically isolated from the beam so as to electrically couple the P3 -X P4 is the voltage V I+ , which in turn couples to the voltage V I + With R C1 , R C2 , R T1 and R T2 Distal lead element X D3 -X D4 is the voltage V I - is bonded to R C3 , R C4 , R T3 and R T4 voltage V I + electrically coupled to

[0084] Referring to the exemplary two-bridge configuration of FIG. 20C, each compression gage resistor and each tension gage resistor is symmetrically positioned about the neutral axis 2004 of the beam. Furthermore, in the second example configuration, the R C1 and R T1 , as well as the R of the proximal half of the second bridge C2 and R T2 are symmetrically arranged about the proximal transverse axis 2006P therebetween in the proximal portion of the beam. T1 is R C1 Partially encloses R T2 is R C2 Partially surrounds R C1 and R T1 The terminals are aligned transversely proximal to the proximal transverse axis 2006P and R C2 and R T2 The terminals of the first bridge are laterally aligned distally to the proximal transverse axis 2006P. C3 and R T3 , as well as the R of the distal half of the second bridge C4 and R T4 are symmetrically disposed about a distal transverse axis 2006D therebetween at the distal portion of the beam. C3 and R T3 The terminals of are aligned transversely proximal to the distal transverse axis 2006D, and R C4 and R T4 The terminals of are aligned laterally distal to the distal transverse axis 2006D.C3 is R C3 Partially encloses R T4 is R C4 Partially surrounds.

[0085] Still referring to FIG. 20C, the elongated lead segments L1′-L4′ are mechanically separated from the beam to form a shorter, integral proximal lead segment X P7 -X P8 and a shorter integral distal lead portion X D7 -X D8 is disposed integrally with the beam. As a result, less stress is applied to the leads during mechanical deflection of the beam, thus resulting in less distortion of the strain measurement when compared to the exemplary sensor of FIG.

[0086] The coupling between the nodes and the leads is the same as in the first and second exemplary configurations of Figures 20B-20C. More specifically, referring to Figure 20C, the mechanically decoupled lead L1' has V O1 - At the node labeled R C1 and R C3 The separated lead wire L2' is arranged to extend mechanically isolated from the beam between the proximal, central, and distal portions of the beam so as to electrically couple the V O1 + At the node labeled R T1 and R T3 The separated lead wire L3' is positioned to extend mechanically isolated from the beam between the proximal, central, and distal portions of the beam so as to electrically couple the V O2 - At the node labeled R C2 and R C4 The separated lead wires L4' are arranged to extend mechanically isolated from the beam between the proximal, central, and distal portions of the beam so as to electrically couple the V O2 + At the node labeled R T2 and R T4The proximal lead element X is disposed between the proximal, central, and distal portions of the beam and extends mechanically isolated from the beam so as to electrically couple the P7 -X P8 is the voltage V I + and thereby the voltage V I + With R C1 , R C2 , R T1 and R T2 Electrically couple the distal lead element X D7 -X D8 is the voltage V I - is bonded to R C3 , R C4 , R T3 and R T4 voltage V I + electrically coupled to

[0087] FIG. 21 is an example diagram showing a set of proximal connection pads 2110P and a set of distal connection pads 2110D located on the beam 2002 of FIG. 20A , with the input pads 2112 and measurement pads 2114 having matching areas. The set of proximal connection pads 2110 and the set of distal connection pads 2110 are located on the example beam 2002 to electrically couple the mechanically isolated measurement output leads L1′-L4′ and input signal leads L5′-L6′ to the strain gauge resistors. Wire bonds (which are in FIG. 21 and are small arcs from the pads to the set of leads, including L5-L6 in the lead bundle) electrically couple the measurement output leads L1′-L4′ to the measurement pads 2114 and the input signal leads L5′-L6′ to the input pads 2112. The input signal pads 2112 are connected to the excitation voltage V as shown. I + , V I - A measurement output pad 2114 is coupled to receive the sensed output voltage V O1 - , V O1 + , V O2- , V O2 + are coupled to receive the

[0088] Conventionally, all pads typically have the same area and therefore the same resistance. However, wire bonds can be inconsistent, which can affect the resistance of the electrical connection between the pad and the lead, which can affect the zero offset between signals on different electrical leads and can affect the temperature sensitivity of the electrical connection. Increasing the resistance at the input pad affects the voltage gain, which is related to the sensitivity of the measurement. Increasing the resistance at the output measurement pad affects the zero offset. In general, gain is easier to manage than zero offset, for example using software.

[0089] FIG. 22 is an example diagram showing a set of proximal connection pads 2110P' and a set of distal connection pads 2110D', where the measurement output pads 2114' have a larger area than the input signal pads 2112'. The input pad area is sacrificed to provide the larger measurement pad area. The larger measurement pad area reduces the resistance of the measurement pads 2114', which reduces the effect of wire bond variations on connection pad resistance and reduces the effect of wire bond variations on zero offset. Thus, the relative increase in measurement pad size compared to input signal pad size reduces the variability in measurement pad resistance and lessens the effect of wire bond position and size variations on measurement accuracy.

[0090] 22, a set of proximal connection pads 2110P' and a set of distal connection pads 2110D' are disposed on the example beam 2002 for electrically coupling the mechanically isolated leads L1'-L4' and L5'-L6' to the strain gauge resistors. Wire bonds electrically couple the leads L1'-L4' to the measurement output pads 2114'. The input signal pads 2112' are connected to the excitation voltage V as shown. I + , V I -The measurement signal output pad 2114' is coupled to receive the sensed output voltage V O1 - , V O1 + , V O2 - , V O2 + are coupled to receive the

[0091] Figure 23 shows the excitation voltage input V I + , V I - FIG. 23 is an exemplary circuit schematic illustrating a force sensor 2000 including exemplary first and second split bridge circuits 2310, 2320 disposed on a beam that shares a common ground. One half of each bridge circuit is disposed at the proximal end of the beam, and one half of each bridge circuit is disposed at the distal end of the beam. However, to simplify the drawing, FIG. 23 does not show the physical separation of the proximal and distal halves at each end of the beam. FIG. 23 illustrates an exemplary configuration of the first and second split bridge circuits in separate, non-overlapping locations on the beam. FIG. 5 illustrates an exemplary interleaved arrangement of the first and second split bridge circuits. FIG. 6 illustrates an exemplary interleaved arrangement of the first and second split bridge circuits.

[0092] As described above, measurement redundancy is achieved using two split-bridge circuits, each with a half-bridge located at the proximal end of the beam and a half-bridge portion located at the distal end of the beam. For example, mismatch in corresponding output measurements of the two split-bridge circuits indicates measurement error and possible damage to one or both of the two bridge circuits. To ensure accuracy in determining measurement mismatch, for example, the resistances of corresponding tap leads of the first and second bridge circuits should match.

[0093] Figure 24 is an example diagram showing tap leads for the example dual divider bridge circuit of Figure 23. The tap leads between the voltage levels and the circuit nodes have equal lead lengths and uniform line widths to provide matched resistance between a given tap point and each of the circuit nodes electrically coupled to the tap point. Thus, the resistance between each tap point and the nodes electrically coupled to the tap point is balanced.

[0094] In particular, for example, the excitation input voltage V I + The tap points of V I +A The length and width of the tap leads between the circuit nodes receiving V I + The voltage V is indicated by a single hash mark on either side of the tap point. I + The tap points of V I +B The length and width of the tap leads between the circuit nodes receiving the signal are equal to the tap lead length and lead width.

[0095] Excitation input voltage V I - Tap points and V I -A The length and width of the tap leads between the circuit nodes receiving V I - The voltage V is indicated by double hash marks on either side of the tap point. I - Tap points and V I -B The length and width of the tap leads between the circuit nodes receiving the signal are equal to the tap lead length and lead width.

[0096] Measurement voltage V O1 + Tap points and V O1 + The length and width of the tap leads between the circuit nodes supplying V O1 + The voltage V is indicated by three hash marks on either side of the tap point. O1 + Tap points and V O1 +BThe length and width of the tap leads between the circuit nodes receiving the signal are equal to the tap lead length and lead width.

[0097] Measurement voltage V O1 - Tap points and V O1 -A The length and width of the tap leads between the circuit nodes supplying V O1 - The voltage V is indicated by the four hash marks on either side of the tap point. O1 - Tap points and V O1 -B The length and width of the tap leads between the circuit nodes receiving the signal are equal to the tap lead length and lead width.

[0098] Measurement voltage V O2 + Tap points and V O2 +A The length and width of the tap leads between the circuit nodes supplying V O2 + The voltage V is indicated by five hash marks on either side of the tap point. O2 + Tap points and V O2 +B The length and width of the tap leads between the circuit nodes receiving the signal are equal to the tap lead length and lead width.

[0099] Measurement voltage V O2 - Tap points and V O2 -A The length and width of the tap leads between the circuit nodes supplying V O2 - The voltage V is indicated by the six hash marks on either side of the tap point. O2 - Tap points and V O2 -B The length and width of the tap leads between the circuit nodes receiving the signal are equal to the tap lead length and lead width.

[0100] Equal tap lead lengths ensure balanced tap lead length resistance on each side of each tap point, resulting in more accurate determination of circuit damage based on, for example, measured output signal mismatch.

[0101] While illustrative examples have been shown and described, a wide range of modifications, changes, and substitutions are contemplated in the foregoing disclosure, and in some examples, some features of the examples may be used without the corresponding use of other features. Those skilled in the art will recognize many variations, alternatives, and modifications. Accordingly, the scope of the present disclosure should be limited only by the following claims, which are appropriately construed broadly and in a manner consistent with the scope of the examples disclosed herein. The foregoing description has been presented to enable those skilled in the art to make and use force sensors with beams and distributed bridge circuits. Various modifications to the examples will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other examples and applications without departing from the scope of the invention. In the foregoing description, numerous details have been set forth for purposes of explanation. However, those skilled in the art will appreciate that the invention may be practiced without these specific details. In other instances, well-known processes have been shown in block diagram form so as not to obscure the description of the invention with unnecessary detail. The same reference numbers may be used to represent different views of the same or similar items in different drawings. Accordingly, the foregoing description and drawings of embodiments according to this invention are merely illustrative of the principles of the invention. It will thus be understood that various modifications can be made to the examples by those skilled in the art without departing from the scope of the invention as defined in the appended claims.

[0102] The following additional note is added: (Supplementary Note 1) A beam having a longitudinal axis, a proximal end, and a distal end; a first Wheatstone bridge disposed on a first surface of the beam, the first Wheatstone bridge including first and second tension gage resistors and first and second compression gage resistors; a second Wheatstone bridge disposed on the first surface of the beam, the second Wheatstone bridge including third and fourth tension gage resistors and third and fourth compression gage resistors; and the first and third tension gage resistors and the first and third compression gage resistors are disposed at a proximal end of the beam; the second and fourth tension gage resistors and the second and fourth compression gage resistors are disposed at a distal end of the beam. Force sensor. (Supplementary Note 2) The first and third tension gauge resistors are installed at the same location on the beam, the first and third compression gage resistors are co-located on the beam; the second and fourth tension gauge resistors are co-located on the beam; the second and fourth compression gage resistors are co-located on the beam; 10. A force sensor as defined in claim 1. (Supplementary Note 3) The first and third tension gauge resistors include interleaved elongated portions; the first and third compression gauge resistors include interleaved elongated portions; the second and fourth strain gauge resistors include interleaved elongated portions; the second and fourth compression gauge resistors include interleaved elongated portions; 10. A force sensor as defined in claim 1. (Supplementary Note 4) The first and third tension gauge resistors have a serpentine configuration interleaved with each other; the first and third compression gauge resistors have a serpentine configuration interleaved with one another; the second and fourth strain gauge resistors have a serpentine configuration interleaved with one another; the second and fourth compression gauge resistors have a serpentine configuration interleaved with one another. 10. A force sensor as defined in claim 1. (Supplementary Note 5) The first, second, third, and fourth tension gauge resistors are aligned with a neutral axis of the beam; the first, second, third, and fourth compression gage resistors are aligned with a neutral axis of the beam; 10. A force sensor as defined in claim 1. (Supplementary Note 6) One of the first and third tension gauge resistors is disposed between the first compression gauge resistor and the third compression gauge resistor; the other of the first and third tension gage resistors is disposed adjacent to only one or the other of the first and third compression gage resistors; one of the second and fourth tension gage resistors is disposed between the second compression gage resistor and the fourth compression gage resistor; the other of the second and fourth tension gauge resistors is disposed adjacent to only one or the other of the second and fourth compression gauge resistors. 10. A force sensor as defined in claim 1. (Supplementary Note 7) The first, second, third, and fourth tension gauge resistors are aligned with a neutral axis of the beam; the first, second, third, and fourth compression gage resistors are aligned with a neutral axis of the beam; 10. A force sensor as defined in claim 1. (Supplementary Note 8) a third Wheatstone bridge disposed on a second surface of the beam perpendicular to the first surface, the third Wheatstone bridge including fifth and sixth tension gauge resistors and fifth and sixth compression gauge resistors; a fourth Wheatstone bridge disposed on the second surface of the beam, the fourth Wheatstone bridge including seventh and eighth tension gage resistors and seventh and eighth compression gage resistors; further comprising the fifth and seventh tension gage resistors and the fifth and seventh compression gage resistors are disposed at a proximal end of the beam; the sixth and eighth tension gage resistors and the sixth and eighth compression gage resistors are disposed at a distal end of the beam. 10. A force sensor as defined in claim 1. (Appendix 9) A beam having a longitudinal axis, a proximal end, and a distal end; a first tension gauge half Wheatstone bridge (half bridge) disposed on a first surface of the beam, the first tension gauge half bridge including first and second tension gauge resistors; a second strain gauge half bridge disposed on the first surface of the beam, the second strain gauge half bridge including third and fourth strain gauge resistors; a compression gauge half bridge disposed on the first surface of the beam, the compression gauge half bridge including first and second compression gauge resistors; and the first and third tension gage resistors and the first compression gage resistor are disposed at a proximal end of the beam; the second and fourth tension gage resistors and the second compression gage resistor are disposed at a distal end of the beam. Force sensor. (Supplementary Note 10) The first and third tension gauge resistors are installed at the same location on the beam, the second and fourth tension gauge resistors are co-located on the beam; 10. The force sensor of claim 9. (Supplementary Note 11) The first and third tension gauge resistors include interleaved elongated portions; the second and fourth strain gauge resistors include interleaved elongated portions; 10. The force sensor of claim 9. (Supplementary Note 12) The first and third tension gauge resistors have a serpentine configuration interleaved with each other; the second and fourth strain gauge resistors have a serpentine configuration interleaved with one another. 10. The force sensor of claim 9. (Supplementary Note 13) The first, second, third, and fourth tension gauge resistors are aligned with a neutral axis of the beam; the first and second compression gauge resistors are aligned with a neutral axis of the beam; 10. The force sensor of claim 9. (Supplementary Note 14) The first compression gauge resistor is disposed between the first tension gauge resistor and the third tension gauge resistor; the second compression gage resistor is disposed between the second tension gage resistor and the fourth tension gage resistor; 10. The force sensor of claim 9. (Supplementary Note 15) The first, second, third, and fourth tension gauge resistors are aligned with a neutral axis of the beam; the first and second compression gauge resistors are aligned with a neutral axis of the beam; 10. The force sensor of claim 9. (Supplementary Note 16) A third tension gauge half Wheatstone bridge (half bridge) disposed on a second surface of the beam perpendicular to the first surface, the third tension gauge half bridge including fifth and sixth tension gauge resistors; a fourth strain gauge half bridge disposed on the second surface of the beam, the fourth strain gauge half bridge including seventh and eighth strain gauge resistors; further comprising the fifth and seventh tension gage resistors and the third compression gage resistor are disposed at a proximal end of the beam; the sixth and eighth tension gage resistors and the fourth compression gage resistor are disposed at a distal end of the beam. 10. A force sensor as defined in claim 1. (Appendix 17) A beam having a longitudinal axis, a proximal end, and a distal end; a first bridge circuit disposed on a first surface of the beam, the first bridge circuit including a plurality of tension gauge resistors; a second bridge circuit disposed on the first surface of the beam, the second bridge circuit including a plurality of tension gauge resistors; a third bridge circuit disposed on the first surface of the beam, the third bridge circuit including a plurality of compression gauge resistors; and at least one tension resistor from each of the first and second bridge circuits and at least one compression gage resistor from the third bridge are disposed at a proximal end of the beam; at least one tension gage resistor from each of the first and second bridge circuits and at least one compression gage resistor from the third bridge are disposed at a distal end of the beam; Force sensor. (Supplementary Note 18) The at least one tension gauge resistor from each of the first and second bridge circuits disposed at the proximal end of the beam is co-located on the beam; the at least one tension gauge resistor from each of the first and second bridge circuits located at the distal end of the beam is co-located on the beam; 18. The force sensor of claim 17. (Supplementary Note 19) The at least one compression gauge resistor from the third bridge circuit disposed at the proximal end of the beam is disposed between the at least one tension gauge resistor from each of the first and second bridge circuits disposed at the proximal end of the beam; the at least one compression gage resistor from the third bridge circuit located at the distal end of the beam is disposed between the at least one tension gage resistor from each of the first and second bridge circuits located at the distal end of the beam; 18. The force sensor of claim 17. (Appendix 20) A beam having a longitudinal axis, a proximal end, and a distal end; a first Wheatstone bridge disposed on a first surface of the beam, the first Wheatstone bridge including first and second tension gage resistors and first and second compression gage resistors; the first tension gage resistor and the first compression gage resistor are disposed at the proximal end of the beam; the second tension gage resistor and the second compression gage resistor are disposed at the distal end of the beam. First Wheatstone bridge and; a first measurement signal lead mechanically isolated from the beam, the first measurement signal lead coupling the first compression gage resistor and the second compression gage resistor; a second measurement signal lead mechanically isolated from the beam, the second measurement signal lead coupling the first tension gauge resistor and the second tension gauge resistor; having Force sensor. (Supplementary Note 21) A second Wheatstone bridge disposed on the first surface of the beam, the second Wheatstone bridge including third and fourth tension gauge resistors and third and fourth compression gauge resistors; the third tension gage resistor and the third compression gage resistor are disposed at the proximal end of the beam; the fourth tension gage resistor and the fourth compression gage resistor disposed at the distal end of the beam; a second Wheatstone bridge; a third measurement signal lead mechanically isolated from the beam, the third measurement signal lead coupling the third compression gage resistor and the fourth compression gage resistor; a fourth measurement signal lead mechanically isolated from the beam, the fourth measurement signal lead coupling the third strain gauge resistor and the fourth strain gauge resistor; further comprising: 21. The force sensor of claim 20. (Supplementary Note 22) Each of the first, second, third, and fourth compression gauge resistors is symmetrically arranged around the neutral axis; each of the first, second, third, and fourth tension gauge resistors being symmetrically disposed about the neutral axis; 22. The force sensor of claim 21. (Supplementary Note 23) Each of the first, second, third, and fourth compression gauge resistors is equally and symmetrically disposed about the neutral axis; each of the first, second, third, and fourth tension gauge resistors being equally and symmetrically disposed about the neutral axis; 22. The force sensor of claim 21. (Supplementary Note 24) The beam includes a proximal transverse axis extending between the first compression gauge resistor and the first tension gauge resistor disposed proximally displaced from the proximal transverse axis, and the third compression gauge resistor and the third tension gauge resistor disposed distally displaced from the proximal transverse axis; the beam includes a distal transverse axis extending between the second compression gauge resistor and the second tension gauge resistor disposed proximally displaced from the distal transverse axis, and the fourth compression gauge resistor and the fourth tension gauge resistor disposed distally displaced from the distal transverse axis; 23. The force sensor of claim 22. (Supplementary Note 25) a first input signal tap line electrically coupling the first compression gauge resistor and the first tension gauge resistor to a first input signal; a second input signal tap line electrically coupling the second compression gauge resistor and the second tension gauge resistor to a second input signal; a first input signal pad electrically coupled to the first input signal tap line; a second input signal pad electrically coupled to the second input signal tap line; a first measurement signal pad electrically coupled to the first measurement signal lead; a second measurement signal pad electrically coupled to the first measurement signal lead; and an area of each of the first and second input pads is smaller than an area of each of the first and second measurement signal pads; 21. The force sensor of claim 20. (Supplementary Note 26) The first input signal pad is wire-bonded to the first input signal tap line; the second input signal pad is wire-bonded to the second input signal tap line; the first measurement signal pad is wire-bonded to the first measurement signal lead; the second measurement signal pad is wire-bonded to the first measurement signal lead; 26. The force sensor of claim 25. (Supplementary Note 27) A second Wheatstone bridge disposed on the first surface of the beam, the second Wheatstone bridge including third and fourth tension gauge resistors and third and fourth compression gauge resistors; the third tension gage resistor and the third compression gage resistor are disposed at the proximal end of the beam; the fourth tension gage resistor and the fourth compression gage resistor are disposed at the distal end of the beam; the first input signal tap line electrically couples the first and third compression gage resistors and the first and third tension gage resistors to the first input signal; the second input signal tap line electrically couples the second and fourth compression gage resistors and the second and fourth tension gage resistors to the second input signal. a second Wheatstone bridge; a third measurement signal lead mechanically isolated from the beam, the third measurement signal lead coupling the third compression gage resistor and the fourth compression gage resistor; a fourth measurement signal lead mechanically isolated from the beam, the fourth measurement signal lead coupling the third strain gauge resistor and the fourth strain gauge resistor; a third measurement signal pad electrically coupled to the third measurement signal lead; a fourth measurement signal pad electrically coupled to the fourth measurement signal lead; further comprising an area of each of the first and second input pads is smaller than an area of each of the first, second, third and fourth measurement signal pads; 26. The force sensor of claim 25. (Appendix 28) A beam having a longitudinal axis, a proximal end, and a distal end; a first Wheatstone bridge disposed on a first surface of the beam, the first Wheatstone bridge including first and second tension gage resistors and first and second compression gage resistors; a second Wheatstone bridge disposed on the first surface of the beam, the second Wheatstone bridge including third and fourth tension gage resistors and third and fourth compression gage resistors; and the first and third tension gage resistors and the first and third compression gage resistors are disposed at the proximal end of the beam; the second and fourth tension gage resistors and the second and fourth compression gage resistors are disposed at the distal end of the beam; A force sensor, a first measurement signal lead mechanically isolated from the beam, coupling the first compression gauge resistor and the second compression gauge resistor, the first measurement signal lead including a first measurement signal tap point, wherein a resistance of the first measurement signal lead between the first measurement tap point and the first measurement gauge resistor matches a resistance of the first measurement signal lead between the first measurement tap point and the second compression gauge resistor; a second measurement signal lead mechanically isolated from the beam, coupling the first tension gauge resistor and the second tension gauge resistor, the second measurement signal lead including a second measurement signal tap point, wherein a resistance of the second measurement signal lead between the second measurement tap point and the first tension gauge resistor matches a resistance of the second measurement signal lead between the second measurement tap point and the second tension gauge resistor; a third measurement signal lead mechanically isolated from the beam, coupling the third compression gage resistor and the fourth compression gage resistor, the third measurement signal lead including a third measurement signal tap point, wherein a resistance of the third measurement signal lead between the third measurement tap point and the third compression gage resistor matches a resistance of the third measurement signal lead between the third measurement tap point and the fourth compression gage resistor; a fourth measurement signal lead mechanically isolated from the beam, coupling the third tension gauge resistor and the fourth tension gauge resistor, the fourth measurement signal lead including a fourth measurement signal tap point, wherein a resistance of the fourth measurement signal lead between the fourth measurement tap point and the third tension gauge resistor matches a resistance of the fourth measurement signal lead between the fourth measurement tap point and the fourth tension gauge resistor; Including, Force sensor. (Supplementary Note 29) a first input signal tap line electrically coupling the first and third compression gauge resistors and the first and third tension gauge resistors to a first input signal, the first input signal tap line including a first input signal tap point, and a resistance of the first input signal tap line being matched between the first input signal tap point, a junction of the first compression gauge resistor and the first tension gauge resistor, and a junction of the third compression gauge resistor and the third tension gauge resistor; a second input signal tap line electrically coupling the second and fourth compression gauge resistors and the second and fourth tension gauge resistors to a second input signal, the second input signal tap line including a second input signal tap point, wherein a resistance of the second input signal tap line matches between the second input signal tap point, a junction of the first compression gauge resistor and the first tension gauge resistor, and a junction of the third compression gauge resistor and the third tension gauge resistor; further comprising: 29. The force sensor of claim 28. (Appendix 30) A beam having a longitudinal axis, a proximal end, and a distal end; a first tension gauge half Wheatstone bridge (half bridge) disposed on a first surface of the beam, the first tension gauge half bridge including first and second tension gauge resistors; a second strain gauge half bridge disposed on the first surface of the beam, the second strain gauge half bridge including third and fourth strain gauge resistors; a compression gauge half bridge disposed on the first surface of the beam, the compression gauge half bridge including first and second compression gauge resistors; and the first and third tension gage resistors and the first compression gage resistor are disposed at a proximal end of the beam; the second and fourth tension gage resistors and the second compression gage resistor are disposed at a distal end of the beam; a first measurement signal lead mechanically isolated from the beam, the first measurement signal lead coupling the first compression gage resistor and the second compression gage resistor; a second measurement signal lead mechanically isolated from the beam, the second measurement signal lead coupling the first tension gauge resistor and the second tension gauge resistor; a third measurement signal lead mechanically isolated from the beam, the third measurement signal lead coupling the third strain gauge resistor and the fourth strain gauge resistor; having Force sensor. (Supplementary Note 31) a first input signal tap line electrically coupling the first compression gauge resistor and the first and third tension gauge resistors to a first input signal; a second input signal tap line electrically coupling the second compression gauge resistor and the second and fourth tension gauge resistors to a second input signal; a first input signal pad electrically coupled to the first input signal tap line; a second input signal pad electrically coupled to the second input signal tap line; a first measurement signal pad electrically coupled to the first measurement signal lead; a second measurement signal pad electrically coupled to the first measurement signal lead; a third measurement signal pad electrically coupled to the first measurement signal lead; and an area of each of the first and second input pads is smaller than an area of each of the first, second and third measurement signal pads; 31. The force sensor of claim 30. (Supplementary Note 32) The first measurement signal lead includes a first measurement signal tap point equally spaced from the first and second compression gauge resistors; the second measurement signal lead includes a second measurement signal tap point equally spaced from the first and second strain gauge resistors; the third measurement signal lead includes a third measurement signal tap point equally spaced from the third and fourth strain gauge resistors; 31. The force sensor of claim 30. (Supplementary Note 33) a first input signal tap line electrically coupling the first and third compression gauge resistors and the first and third tension gauge resistors to a first input signal, the first input signal tap line including a first input signal tap point, and a resistance of the first input signal tap line being matched between the first input signal tap point, a junction of the first compression gauge resistor and the first tension gauge resistor, and a junction of the third compression gauge resistor and the third tension gauge resistor; a second input signal tap line electrically coupling the second and fourth compression gauge resistors and the second and fourth tension gauge resistors to a second input signal, the second input signal tap line including a second input signal tap point, wherein a resistance of the second input signal tap line matches between the second input signal tap point, a junction of the first compression gauge resistor and the first tension gauge resistor, and a junction of the third compression gauge resistor and the third tension gauge resistor; further comprising: 33. The force sensor of claim 32.

Claims

1. a beam including a proximal end, a distal end, and a first surface between the proximal end of the beam and the distal end of the beam; a first bridge circuit on the first surface of the beam, the first bridge circuit including a first tension gauge resistor, a second tension gauge resistor, a first compression gauge resistor, and a second compression gauge resistor; a second bridge circuit on the first surface of the beam, the second bridge circuit including a third tension gauge resistor, a fourth tension gauge resistor, a third compression gauge resistor, and a fourth compression gauge resistor; and the first and third tension gage resistors and the first and third compression gage resistors are at the proximal end of the beam; the second and fourth tension gage resistors and the second and fourth compression gage resistors are at the distal end of the beam; a longitudinal axis extending between the proximal end of the beam and the distal end of the beam; a neutral axis extends parallel to the longitudinal axis and equidistant from opposite edges of the first face of the beam within the first face of the beam; the first, second, third, and fourth tension gauge resistors are each disposed on the first surface of the beam and each aligned with a neutral axis of the beam; Force sensor.

2. the first and third strain gauge resistors are co-located on the beam; the first and third compression gage resistors are co-located on the beam; the second and fourth strain gauge resistors are co-located on the beam; the second and fourth compression gage resistors are co-located on the beam; The force sensor of claim 1 .

3. the first and third tension gauge resistors include corresponding first and third tension gauge resistor elongated portions, the first and third tension gauge resistor elongated portions interdigitating with each other; the first and third compression gage resistors include corresponding first and third compression gage resistor elongated portions, the first and third compression gage resistor elongated portions interdigitating with each other; the second and fourth tension gauge resistors include corresponding second and fourth tension gauge resistor elongated portions, the second and fourth tension gauge resistor elongated portions interdigitating with each other; the second and fourth compression gage resistors include corresponding second and fourth compression gage resistor elongated portions, the second and fourth compression gage resistor elongated portions interdigitating with each other; The force sensor of claim 1 .

4. the first and third tension gauge resistors have corresponding first and third tension gauge resistor serpentine configurations, the first and third tension gauge resistor serpentine configurations being interdigitated; the first and third compression gauge resistors have corresponding first and third compression gauge resistor serpentine configurations, the first and third compression gauge resistor serpentine configurations interdigitating with each other; the second and fourth tension gauge resistors have corresponding second and fourth tension gauge resistor serpentine configurations, the second and fourth tension gauge resistor serpentine configurations being interdigitated; the second and fourth compression gauge resistors have corresponding second and fourth compression gauge resistor serpentine configurations, and the second and fourth compression gauge resistor serpentine configurations are interdigitated. The force sensor of claim 1 .

5. the first, second, third, and fourth compression gage resistors are respectively located on the first surface of the beam and respectively aligned along the neutral axis; The force sensor of claim 1 .

6. one of the first and third tension gauge resistors is between the first and third compression gauge resistors, and the other of the first and third tension gauge resistors is adjacent to only one or the other of the first and third compression gauge resistors; one of the second and fourth tension gauge resistors is between the second and fourth compression gauge resistors, and the other of the second and fourth tension gauge resistors is adjacent to only one or the other of the second and fourth compression gauge resistors; The force sensor of claim 1 .

7. the first, second, third, and fourth compression gage resistors are each located on the first surface and each aligned along the neutral axis in the first surface of the beam; The force sensor according to claim 6.

8. the beam has a second surface perpendicular to the first surface; the force sensor further includes a third bridge circuit on the second surface of the beam, the third bridge circuit including fifth and sixth tension gage resistors and fifth and sixth compression gage resistors; the force sensor further includes a fourth bridge circuit on the second surface of the beam, the fourth bridge circuit including seventh and eighth tension gage resistors and seventh and eighth compression gage resistors; the fifth and seventh tension gage resistors and the fifth and seventh compression gage resistors are at the proximal end of the beam; the sixth and eighth tension gage resistors and the sixth and eighth compression gage resistors are at the distal end of the beam. The force sensor of claim 1 .

Images