阅读说明：本技术 具有受控热传导的机器人力/扭矩传感器 (Robotic force/torque sensor with controlled heat conduction ) 是由 J·利普赛 于 2021-06-16 设计创作，主要内容包括：机器人力/扭矩(FT)传感器约束附接工具产生的热量经FT传感器主体径向传导。工具的热量经导热构件引导到FT传感器主体的中心。工具的热量通过绝热构件与FT传感器主体的除其中心以外的部分隔离。如附接到可变形梁表面的应变计的换能器从FT传感器主体的中心以基本相等的距离布置。当热量从中心经FT传感器主体径向向外传导时,所有换能器在任何给定时间经历基本相等的热负荷。本发明的实施例基本消除了以如半桥或四分之一桥的差分电路拓扑连线的转换器组之间的热梯度,增强了这种电路抑制由FT传感器主体或换能器本身的热变化引起的共模信号分量的能力。消除FT传感器主体中除径向方向以外的热梯度,提高了已知温度补偿技术的有效性。(The robot force/torque (FT) sensor constrains heat generated by the attachment tool from being conducted radially through the FT sensor body. The heat of the tool is conducted to the center of the FT sensor body via the heat conductive member. The heat of the tool is isolated from the portion of the FT sensor body other than the center thereof by the heat insulating member. Transducers such as strain gauges attached to the deformable beam surface are arranged at substantially equal distances from the center of the FT sensor body. As heat is conducted radially outward from the center through the FT sensor body, all transducers experience substantially equal thermal loads at any given time. Embodiments of the present invention substantially eliminate thermal gradients between groups of transducers wired in a differential circuit topology, such as a half-bridge or quarter-bridge, enhancing the ability of such circuits to reject common-mode signal components caused by thermal variations in the FT sensor body or the transducer itself. Eliminating thermal gradients in the FT sensor body other than in the radial direction improves the effectiveness of known temperature compensation techniques.)

1. A robotic force/torque sensor interposed between a robot and a heat generating tool, comprising:

a tool interface region having a central bore;

a mounting interface region disposed annularly about and spaced apart from the tool interface region;

a plurality of deformable beams extending radially around and connecting the tool interface region to the mounting interface region;

a transducer secured to a surface of at least some of the deformable beams and configured to convert tensile and compressive strains at the deformable beam surface into electrical signals;

a thermally conductive member configured to contact the central bore in a thermally conductive relationship; and

a thermal insulation member configured to isolate portions of the robotic force/torque sensor other than the central aperture from thermal contact with the thermally conductive member.

2. The robotic force/torque sensor of claim 1, wherein:

heat from the heat generating tool is conducted through the thermally conductive member to the central bore and radially outward through the tool interface region and the deformable beam; and is

The transducer includes strain gauges fixed to the surface of the deformable beam at substantially the same distance along the length of the beam, measured from the tool interface region, whereby all of the strain gauges experience substantially simultaneously temperature changes caused by the heat generating tool.

3. The robotic force/torque sensor of claim 1, wherein the thermally conductive member comprises:

a shank sized and shaped for thermal contact with an inner surface of the central bore; and

a flange connected to the shank and sized and shaped to extend at least partially over the first surface of the tool interface region.

4. The robotic force/torque sensor of claim 3, wherein the thermal insulation comprises:

an annular ring disposed between a first surface of the tool interface region and a flange of the thermally conductive member.

5. The robotic force/torque sensor of claim 4, further comprising a fastener connecting a flange of the thermally conductive member and the tool interface region, wherein the thermal insulation member is disposed between the flange and the tool interface region.

6. The robotic force/torque sensor of claim 4, wherein an adhesive connects one side of the thermal insulation member to a flange of the thermally conductive member and an adhesive connects another side of the thermal insulation member to a facing surface of the tool interface region.

7. A method of operating a robotic force/torque sensor, the robotic force/torque sensor having: a tool interface region having a central bore; a mounting interface region disposed annularly about and spaced apart from the tool interface region; a plurality of deformable beams extending radially around and connecting the tool interface region to the mounting interface region; and a transducer secured to a surface of at least some of the deformable beams and configured to convert tensile and compressive strains at the deformable beam surface into electrical signals, the method comprising:

placing a thermally conductive member in thermally conductive relation to the central bore; and

isolating portions of the robotic force/torque sensor other than a central bore from thermal contact with the thermally conductive member by using the thermal insulation member;

whereby heat from a heat generating tool attached to the heat conducting member is conducted through the heat conducting member to the central bore and radially outward through the tool interface region and the deformable beam.

8. The method of claim 7, wherein the transducer comprises strain gauges fixed to a surface of the deformable beam at substantially the same distance along the length of the beam from the tool interface region such that all of the strain gauges experience substantially simultaneously temperature changes caused by the heat generating tool.

9. The method of claim 7, wherein the thermally conductive member comprises:

a shank sized and shaped for thermal contact with an inner surface of the central bore; and

a flange connected to the shank and sized and shaped to extend at least partially over the first surface of the tool interface region.

10. The method of claim 7, wherein the insulation comprises:

an annular ring disposed between a first surface of the tool interface region and a flange of the thermally conductive member.

Technical Field

The present invention relates generally to force/torque sensors for robotic applications, and in particular to force/torque sensors having predictable heat distribution throughout the sensor body during operation.

Background

Robotics is an ever-growing and increasingly important area in industrial, medical, scientific, aerospace, and other applications. In many cases where the robotic arm or a tool attached thereto is in contact with a workpiece, the applied force and/or torque must be closely monitored. Force/torque sensors are therefore an important component of many robotic systems.

Many types of force/torque sensors are known in the art. One known type of force/torque sensor uses a mechanical-electrical transducer, such as a strain gauge, to measure the deformation of a trabecula connecting two regions of the sensor body, one such region being connected to the robotic arm and the other region being connected to the robotic tool. For example, a central region of the sensor body (commonly referred to in the art as a Tool Adapter Plate (TAP), and referred to herein as a "Tool interface region") is connected (directly or indirectly) to a Tool. Another region of the sensor body (commonly referred to in the art as a Mounting Adapter Plate (MAP) and referred to herein as a "Mounting interface region") disposed annularly about and spaced apart from the tool interface region is connected (directly or indirectly) to the robotic arm. While in some embodiments the tool interface region and the mounting interface region may be separate components that are assembled into a force/torque sensor, in many modern designs the force/torque sensor body is a unitary design, e.g., milled from a single piece (or sheet) of metal. The terms tool interface region and mounting interface region refer to both types of force/torque sensor configurations.

Of course, in any given application, the robot may be connected to the tool interface area and the tool may be connected to the attachment interface area. Thus, the terms tool interface region and mounting interface region are used herein as reference terms only. Furthermore, one or more other devices may be interposed between the force/torque sensor and the tool or robot, such as the main unit and the tool unit of a robotic tool changer, as is well known in the art.

The mounting interface region and the tool interface region are connected to each other by a plurality of relatively thin (and thus mechanically deformable) beams arranged radially around the tool interface region, in some cases similar to spokes of a wheel. A relative force or torque between objects attached to the tool interface region and the mounting interface region, respectively, attempts to move the mounting interface region relative to the tool interface region, resulting in a slight deformation or bending of at least some of the beams.

Transducers, such as strain gauges, are secured to some or all surfaces of at least some of the beams in various positions and orientations. Strain gauges, which exhibit strain-related resistance, convert the tensile and compressive strain (caused by mechanical deformation of the beam) of the beam surface into electrical signals. The signals from the strain gauges on the instrumented beams are processed together after calibration to resolve the magnitude and direction of the relative forces and/or torques between the tool interface region and the mounting interface region, and thus between the tool and the robot. As non-limiting examples, U.S. patent publications 2017/0211999 and 2017/0205296 and international publication WO2018/200668, both assigned to the assignee of the present application, describe force/torque sensors for robotic applications. These disclosures are incorporated herein by reference in their entirety.

As known in the art, and as discussed in the incorporated disclosure above, thermal variations have a detrimental effect on accurate force/torque measurements. For example, variations in the resistance of the sensor and/or cable, expansion of the sensor body material, and other effects can cause errors.

Silicon strain gauges are preferred for many applications due to their high sensitivity compared to foil strain gauges. However, they show significantly worse temperature performance. Silicon strain gauges have two main Temperature effects-the Temperature Coefficient of Resistance of the strain gauge (TCR) and the Temperature Coefficient of strain Factor of the strain gauge (TC GF). TCR occurs when the resistance of a silicon strain gauge changes with temperature. In some strain gauges, the resistance may change more over a temperature range of 0-50 ℃ than when the sensor is loaded at full scale. TCGF occurs because the strain factor of a silicon strain gauge (which describes the correlation between the strain experienced by the gauge and the resulting change in its resistance) is temperature dependent. The resistance of the conductors used to connect the strain gauges together and to measure the electronics is also temperature dependent.

As the temperature increases, the metallic force/torque sensor body will expand to the extent described by the coefficient of expansion of the material. For example, the expansion coefficient of steel is about 11ppm/K, which means that an expansion of 11 μm/m can be expected at a temperature increase of 1 degree Celsius. This expansion is "detected" by the surface strain gauges as significant strain even when no mechanical load is applied.

Other thermal factors that may introduce error (although generally less prominent than those described above) include erroneous non-common mode outputs of the balancing circuit of the strain gauge having a temperature gradient across it; temperature dependence of the modulus of elasticity of the sensor body material; self-heating of the strain gauge due to the excitation voltage; the relative humidity and hygroscopicity of the strain gauge carrier material; and temperature-dependent changes in the effectiveness of the adhesive used to bond the strain gauge to the sensor body surface.

Attempts have been made in the art to eliminate the deleterious effects of temperature changes on force/torque sensors. Self-compensating strain gauges with temperature characteristics tailored to a particular material exhibit less temperature dependent effects. However, self-compensating strain gauges are more complex, more expensive than conventional strain gauges, and must be carefully matched to the force/torque sensor body material. Furthermore, some circuit configurations, such as a half wheatstone bridge circuit, may result in temperature-induced changes that appear as common-mode signals being cancelled out at least if all of the strain gauges in the bridge experience the same temperature change (as described above, thermal gradients across the bridge configuration undermine this assumption).

As discussed in the incorporated disclosure above, advanced techniques for compensating strain gauge readings for temperature induced errors are known in the art. For example, US2017/0205296 discloses fixing a strain gauge to an unstressed part of a sensor body. Any significant strain detected by this strain gauge is purely thermally induced due to expansion of the sensor body and changes in the resistivity of the sensor and/or cable, and can be mathematically removed from the output of the other strain gauges when measuring the actual force and torque. WO2018/200668 discloses the use of thermal sensors in proximity to strain gauges and explicit compensation of the individual strain gauge outputs for local temperature changes. The publication also discloses a transient temperature compensation method whereby the transient temperature distribution throughout the sensor body is modeled and the thermally induced strain is predicted and removed from the measurement signal.

Generally, these techniques are most effective where the temperature variation is uniform across the force/torque sensor body — this rarely occurs in practical applications. However, even with the necessity of receiving uneven heating, it would be advantageous to control the heating so that substantially all of the strain gauges experience temperature changes substantially simultaneously.

The background section herein is provided to place embodiments of the invention in a technical and operational context to assist those skilled in the art in understanding their scope and utility. The approaches described in the background section may be pursued, but are not necessarily approaches that have been previously conceived or pursued. Unless expressly stated otherwise, any statement herein is not to be construed as prior art merely because of its inclusion in the background section.

Disclosure of Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding to those skilled in the art. This summary is not an extensive overview of the disclosure and is not intended to identify key/critical elements of the embodiments or to delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

According to one or more embodiments described and claimed herein, a robotic force/torque (FT) sensor constrains conduction of heat generated by an attached tool through an FT sensor body in a radial direction. Heat from the tool is conducted to the center of the FT sensor body through the heat conductive member. In addition, the portion other than the center of the FT sensor main body is insulated from heat generated by the tool by the heat insulating member. The transducers (e.g., strain gauges attached to the deformable beam surface) are arranged substantially equidistant from the center of the FT sensor body. Thus, all transducers experience substantially equal thermal loads at any given time as heat is conducted radially outward from the center through the FT sensor body. Embodiments of the present invention substantially eliminate thermal gradients between transducer groups wired in a differential circuit topology (e.g., half-bridge or quarter-bridge), enhancing the ability of such circuits to reject common-mode signal components caused by thermal variations in the FT sensor body or the sensor itself. Eliminating thermal gradients in the FT sensor body, rather than thermal gradients in the radial direction, increases the effectiveness of known temperature compensation techniques.

One embodiment relates to a robot force/torque sensor interposed between a robot and a heat generating tool. The robot force/torque sensor includes: a tool interface region having a central bore; a mounting interface region annularly disposed about and spaced from the tool interface region; a plurality of deformable beams extending radially around and connecting the tool interface region to the mounting interface region; a transducer secured to a surface of at least some of the deformable beams and configured to convert tensile and compressive strains at the surface of the deformable beams into electrical signals; a thermally conductive member configured to contact the central bore in a thermally conductive relationship; and a thermal insulation member configured to insulate a portion of the robot force/torque sensor other than the central hole from thermal contact with the heat conductive member.

Another embodiment relates to a method of operating a robotic force/torque sensor having: a tool interface region having a central bore; a mounting interface region annularly disposed about and spaced from the tool interface region; a plurality of deformable beams extending radially around and connecting the tool interface region to the mounting interface region; and a transducer secured to a surface of at least some of the deformable beams and configured to convert tensile and compressive strains at the surface of the deformable beams into electrical signals. The heat conducting member is in heat conducting relationship with the central bore. The portion of the robot force/torque sensor other than the central bore is isolated from thermal contact with the thermally conductive member by the use of an insulating member. Heat from a heat generating tool attached to the heat conducting member is conducted through the heat conducting member to the central bore and radially outward through the tool interface region and the deformable beam.

Drawings

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. However, the present invention should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

Fig. 1 is an exploded sectional view of a force/torque sensor in operation.

Fig. 2 is an exploded perspective view of the force/torque sensor.

Fig. 3 is a cross-sectional view of a force/torque sensor.

Fig. 4 is a flow chart of a method of operating a robotic force/torque sensor.

Detailed Description

For simplicity and illustrative purposes, the present invention is described primarily by reference to exemplary embodiments thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without limitation to these specific details. In this description, well-known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.

Fig. 1 is an exploded cross-sectional view of a typical tool 10 (e.g., a grinder) attached to a robotic arm 12, such as may be deployed in a factory or other application. A robotic force/torque (FT) sensor 14 is interposed between the tool 10 and the robot 12. The FT sensor 14 measures the force and torque between the robot 12 and the tool 10, i.e. when the robot 12 presses the tool 10 against a workpiece. Other components may be included in the "stack," as known in the art, such as a robotic tool changer component that provides a mechanical interface and provides for transferring utilities between the robot 12 and the attachment tool 10. Many tools 10 generate significant heat that is conducted to connected metal components, such as FT sensor 14. Occasional temperature gradients caused by uneven/uncontrolled heating of the body of FT sensor 14 are a significant source of force and torque measurement errors.

Fig. 2 shows FT sensor 14. FT sensor body 16 includes a tool interface region 18 having a central bore 20, a mounting interface region 22, and a plurality of deformable beams 24 connecting tool interface region 18 and mounting interface region 22. The mounting interface region 22 is annularly disposed about and spaced apart from the tool interface region 18. The deformable beam 24 extends radially around the tool interface region 18. The embodiment shown in fig. 2 has three deformable beams 24 — the configuration shown and described in the above-incorporated publication US 2017/0205296. However, this configuration is not limiting, and generally any number of deformable beams 24 may be used.

The transducer 26 is secured to a surface of at least some of the deformable beams 24. The transducer 26 is configured to convert the tensile and compressive strains at the deformable beam surface into electrical signals. In the embodiment shown in FIG. 2, the transducer 26 comprises a strain gauge, such as a silicon strain gauge, which exhibits a mechanical strain-dependent resistance. However, embodiments of the present invention are not limited to using silicon (or other types of) strain gauges as the transducer 26. The transducers 26 may be attached to only one surface, e.g., the uppermost surface, of each instrumented deformable beam 24, or they may be attached to some or all surfaces, e.g., opposing surfaces, of each instrumented deformable beam 24. Various wiring topologies of strain gauges are known, such as wheatstone bridge, half-bridge and quarter-bridge configurations. Note that the wiring connecting the transducers 26 and the measurement circuitry that interprets the generated electrical signals into force and torque are not shown in fig. 2. Preferably, the transducers 26 are fixed to the surface of the deformable beam 24 at substantially the same distance along the length of the beam, as measured from the tool interface region 18.

Consider a conventional FT sensor that includes only body 16 and transducer 26. The tool may be attached to the tool interface region 18 (or mounting interface region 22) directly or through a thermally conductive (i.e., metallic) means. The motor, weld head, etc. generate a significant amount of heat when the tool is operated. The heat is conducted to a facing surface, e.g., an upper surface, of the tool interface region 18, as shown in fig. 2. While heat will conduct along the deformable beam 24 to the mounting interface region 22, it also conducts from the upper surface of the tool interface region 18 (and deformable beam 24) through the body of the FT sensor 14 to the lower surface. That is, in addition to any radial gradients as heat flows along deformable beam 24 to mounting interface region 22, an axial thermal gradient is also created within FT sensor body 16. These bi-directional thermal gradients (axial and radial) are difficult to model accurately. Therefore, it is difficult to account for temperature compensation techniques when applying them to the transducer 26. Furthermore, the use of stress-free transducers 26 for measuring and therefore subtracting thermally-induced strain is limited, as different portions of the FT sensor body 16 will be at different temperatures.

In particular, in the common case where transducers 26 are attached to opposite sides of the instrumented deformable beam 24, such as the upper and lower surfaces, as shown in FIG. 2, and these transducers 26 are in a differential configuration, such as a half-bridge connection, the axial thermal gradient will heat the transducers 26 on the upper surface, and then the transducers 26 on the lower surface. Because the temperature-induced variations in the output of the two transducers 26 are different, the half-bridge circuit cannot reject these variations as a common-mode signal.

According to an embodiment of the present invention, heat from the attachment tool is directed to the center of the tool interface region 18, and only there. Heat is then conducted only radially through FT sensor body 16, through tool interface region 18 and along deformable beams 24 toward mounting interface region 22. While this may result in thermal gradients that affect the operation of FT sensor 14, it is a predictable gradient. For example, heat is applied substantially simultaneously to substantially the entire thickness of the tool interface region 18. Thus, when heat is conducted radially outward through the tool interface region 18 and into the deformable beam 24, there is little or no thermal gradient in the radial direction. This means that transducers 26 attached to the upper and lower surfaces of instrumented deformable beam 24 will experience substantially the same magnitude of temperature change at substantially the same time. Thus, a balanced circuit topology such as a half bridge will suppress common mode temperature induced strain, and the half bridge will only output a signal corresponding to applied force and torque induced deformation of beam 24. Attaching all of the transducers 26 to the various surfaces of the deformable beam 24 at substantially the same distance along the length of the beam 24, as measured from the tool interface region 18, ensures that all of the transducers experience temperature changes substantially simultaneously. These controlled, predictable aspects of heat flow through FT sensor 14 greatly simplify the application of temperature compensation techniques to the output of transducer 26.

In one embodiment, as shown in fig. 2, heat from the attachment tool is directed to the tool interface region central bore 20 through the thermally conductive member 28. The thermally conductive member 28 includes a portion, such as a shank 30, disposed within the central bore 20. The shank portion 30 of the thermally conductive member 28 contacts the central bore 20 in thermally conductive relation. For example, in one embodiment, the shank 30 forms a close physical fit with the inner surface of the central bore 20. In another embodiment, the shank 30 is press-fit into the central bore 20. In yet another embodiment, the space between the shank 30 and the central bore 20 is filled with a thermally conductive paste. The handle 30 may be a cylindrical tube, as shown, or may be solid. Further, while the central bore 20 and the shank 30 are depicted as circular and cylindrical, respectively, these shapes are not limiting. The central bore 20 and the shank 30 may be rectangular, star-shaped, or any other mating shape that achieves contact in a thermally conductive relationship.

As the name implies, the heat conductive member 28 is formed of a material having high thermal conductivity, such as aluminum or copper. In addition to high thermal conductivity, the thermally conductive member 28 must exhibit sufficient strength and rigidity to support the attachment tool and transfer forces and torques from the tool to the tool interface region 18 without substantial bending, compression, or other deformation. To facilitate a rigid connection with the tool interface region 18, the thermally conductive member 28 includes a flange 32. As discussed further herein, the flange 32 may be connected to the tool interface region 18 by bolts or other fasteners or by other means.

To ensure that heat from the attachment tool is directed only to the central bore 20 and not conducted to the upper surface of the tool interface region 18, an insulating member 34 is interposed between the flange 32 of the heat conducting member 28 and the facing surface of the tool interface region 18. In the embodiment shown in fig. 2, the thermal insulation 34 is a flat annular ring, i.e. a large washer, but this shape is not limiting. Insulation 34 is configured to isolate all portions of FT sensor 14 except for central bore 20 from thermal contact with thermally conductive member 28. Thus, it is preferably at least coextensive with the flange 32 of the thermally conductive member 28, and may extend radially beyond the flange 32 in some embodiments. As the name implies, the heat insulating member 34 is formed of a material having low thermal conductivity, such as titanium, stainless steel, fiberglass, or the like. In addition to low thermal conductivity, the thermal insulation member 34 must exhibit sufficient strength and rigidity to transfer forces and torques from the flange 32 of the thermally conductive member 28 to the tool interface region 18 substantially without bending, compression or other deformation.

Fig. 3 is a cross-sectional view of FT sensor 14 in an operating configuration (fig. 1 shows this configuration in an exploded cross-sectional view). FT sensor body 16 includes a tool interface region 18, a mounting interface region 22, and a plurality of deformable beams 24 (not shown in fig. 3) connecting tool interface region 18 to mounting interface region 22. At least some of the deformable beams 24 are equipped with transducers 26. A thermally conductive member 28 including a shank 30 and a flange 32 is disposed within and above FT sensor 14 such that shank 30 fits within central bore 20 of tool interface region 18 and flange 32 extends at least partially above an upper surface of tool interface region 18. An insulating member 34 is interposed between flange 32 of thermally conductive member 28 and tool interface region 18 of FT sensor 14. In one embodiment, the thermally conductive member 28 is rigidly secured to the tool interface region 18 by a plurality of fasteners 36, such as countersunk bolts, connecting the flange 32 to the tool interface region 18 and extending through-holes in the insulating member 34. The fasteners 36 (e.g., bolts, screws, rivets, etc.) are preferably formed of a metal having a low thermal conductivity, such as 316 stainless steel. Other ways of rigidly securing thermally conductive member 28 and thermally insulating member 34 to FT sensor 14 are within the scope of embodiments of the invention. For example, in one embodiment, the adhesive is applied between the flange 32 and one face of the insulation member 34, and also between the other face of the insulation member 34 and the facing side of the tool interface region 18.

In practice, a robotic tool, e.g., a welding head, a drill or grinder such as one having a motor, etc., attached (directly or indirectly) to the thermally conductive member 28 of the FT sensor 14, generates significant heat. This heat is directed by the heat conducting member 28 to the central bore 20 of the tool interface region 18 where it is conducted radially outward by the FT sensor 14, substantially equally in each radial direction. The insulation 34 isolates the FT sensor 14 (particularly the facing surface of the tool interface region 18) from this heat, ensuring that substantially all of the heat conducted from the tool is directed to the central bore 20 of the tool interface region 18. This configuration substantially eliminates any thermal gradients in the axial direction (i.e., through the thickness of FT sensor body 16). Because the transducers 26 attached to the instrumented deformable beam 24 are positioned at substantially equal distances along the length of the beam, each transducer 26 experiences substantially equal thermal loading at any given time, as measured from the tool interface region 18. In particular, thermal gradients across the transducers 26 wired together in a differential circuit topology, such as a half-bridge or quarter-bridge, are substantially eliminated, allowing the differential circuit to effectively cancel the common mode thermal component of the output variations.

Fig. 4 shows steps in a method 100 of operating a robotic FT sensor 14. As described above, FT sensor 14 has: a tool interface region 18 having a central bore 20; a mounting interface region 22 disposed annularly about the tool interface region 18 and spaced apart from the tool interface region 18; a plurality of deformable beams 24 extending radially around the tool interface region 18 and connecting the tool interface region 18 to the mounting interface region 22; a transducer 26 secured to a surface of at least some of the deformable beams 24 and configured to convert the tensile and compressive strains at the deformable beam surface into electrical signals. The thermally conductive member 28 is placed in thermally conductive relation to the central bore 20 (block 102). The portions of the FT sensor 14 other than the central bore 20 are isolated from thermal contact with the thermally conductive member 28 by the use of the thermal insulation 34 (block 104). In operation, heat from a heat generating tool attached (directly or indirectly) to the heat conducting member 28 is conducted through the heat conducting member 28 to the central bore 20 and radially outward through the tool interface region 18 and the deformable beam 24. In this manner, transducers 26 attached to some of the deformable beams 24 are simultaneously subjected to substantially the same thermal load, thereby simplifying the temperature compensation technique.

Embodiments of the present invention present significant advantages over prior art FT sensors, particularly in applications where the attachment tool generates heat. By directing this heat to the center of the tool interface region 18, and otherwise isolating the FT sensor 14 from this heat, substantially uniform heat conduction through the FT sensor body 16 in a strictly radial direction is ensured. By positioning the transducers 26 substantially equidistant from the tool interface region 18, it is ensured that all of the transducers 26 have a substantially uniform thermal load, thereby allowing known temperature compensation techniques to operate with greater efficiency and accuracy.

As used herein, a material described as having high thermal conductivity has a thermal conductivity k greater than about 100 BTU/hr-ft-F. Materials described herein as having low thermal conductivity have a thermal conductivity k of less than about 50 BTU/hr-ft-F. As used herein, the term "configured to" means arranged, organized, adjusted or arranged to operate in a specific manner; the term is synonymous with "designed for". As used herein, the term "substantially" encompasses and accounts for similar sources of mechanical tolerances, measurement errors, random variations, and inaccuracies.

The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.