Robotic arm for calibrating a force gauge in a calibration jig

Abstract

Apparatus for calibrating a force-sensitive catheter, the apparatus comprising a test weight supported by a rim formed around a bore of a motorized arm and configured for calibrating a force gauge of a catheter calibration jig of the apparatus, the motorized arm configured to place the test weight above a top surface of the force gauge, and a processor. The test weight has a shape that is configured to have the weight freely disengage and rest on the gauge when applying a normal force on the weight lower surface by lifting the force gauge to a test position along a vertical axis. The processor is configured to (i) operate the motorized arm to place the test weight above gauge, (ii) operate a mechanical stage to lift gauge to the test position, (iii) receive force measurements from gauge, and (iv) generate calibration data for the gauge based on the force measurements.

Description

[0001] ROBOTIC ARM FOR CALIBRATING A FORCE GAUGE IN A

[0002] CALIBRATION JIG

[0003] FIELD OF THE DISCLOSURE

[0004] This disclosure relates generally to calibration of force sensitive catheters , and more speci fically to automated calibration of a force gauge of a calibration j ig for calibrating force sensitive catheters .

[0005] BACKGROUND

[0006] During a cardiac ablation procedure , the contact force between an electrode and tissue being ablated is an important parameter for both pulse- field ablation ( PFA) and radiofrequency (RF) ablation .

[0007] PFA and RF ablation are cardiac catheter treatment methods that may restore a heart ' s sinus rhythm . During the clinical procedure , a physician inserts a distal end of a catheter into the heart by a minimally invasive method, such as through a femoral artery . The physician manipulates the proximal end of the catheter shaft to position the distal end at a desired tissue location and to engage the one or more electrodes against the tissue with a desired contact force . When contact is achieved, ablation may then be activated . The quality and depth of the ablation achieved may be related to the accuracy of the contact force applied .

[0008] The present disclosure will be understood from the following detailed description, taken in conj unction with the drawings in which : BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1 is a schematic block diagram of a catheter contact force calibration apparatus, according to an example of the present disclosure;

[0010] Fig. 2 is a schematic perspective view of the jig of the apparatus of Fig. 1, and of the robotic arm of apparatus the apparatus, which together enable calibration of the force gauge of the jig, according to an example of the present disclosure;

[0011] Figs. 3A, 3B, 3C and 3D are schematic illustrations of the elements comprised in the apparatus of Fig. 1 that enable automatic calibration of the force gauge, according to an example of the present disclosure; and

[0012] Fig. 4 is a flow chart that schematically describes the automatic calibration of the force gauge of the jig of Fig. 2 using the apparatus of Fig. 1, according to an example of the present disclosure.

[0013] DESCRIPTION OF EXAMPLES

[0014] OVERVIEW

[0015] During manufacturing, contact force as would be sensed by a distal end assembly of a catheter inside an organ, is calibrated. During calibration, a jig is used to apply a force to the distal end assembly and to measure the applied force. The jig applies force in a plurality of different 3D directions and optionally compresses, deflects, and / or deforms the distal end assembly, while a force gauge of the jig measures the force exerted on the distal end assembly.

[0016] In some examples, the force-sensing assembly may measure the deformation of an elastic portion of the distal end assembly and infer force based on the sensed deformation in response to a force applied by the force gauge to the elastic portion .

[0017] In other examples , the catheter distal end assembly includes a force-sensing assembly . A processor compares the output of the force-sensing assembly to that of the j ig' s force gauge , to calibrate the force-sensing assembly . The relationship established between the force measured by the force sensing assembly of the distal end assembly and the measured force by the j ig may be used to determine contact force based on the sensor assembly' s output .

[0018] Routine calibration of the force gauge itsel f is required because its accuracy may deteriorate over time or be af fected by ambient environment changes . As the force gauge is highly linear over the required measurement range of typically applied contact forces ( e . g . , 0 to 300 grams for some tip catheters or 0 to 10 grams for some basket catheters ) , it is suf ficient to calibrate the force gauge using two data points : zero force and some intermediate force - using a calibration test weight , e . g . , of 50 grams . However, a manual calibration of the gauge increases the workload and may introduce inaccuracies .

[0019] An example of the present disclosure described hereinafter provides a technique to automatically calibrate the force gauge , solving the issues of excess workload and inaccuracies . A processor controlling the j ig may initiate periodic calibrations of the force gauge to ensure accurate force measurements or calibration upon detection of ambient condition changes , such as in temperature and humidity . In this way, the disclosed technique ensures a stable and high-yield manufacturing process, as well as accurate force measurements of each manufactured catheter.

[0020] To this end, the jig used in calibrating the forcesensitive catheters is supplemented with a robotic arm fitted with a test weight. The arm is configured to accept different test weights depending on an expected range of contact forces (e.g., depending on the catheter type to calibrate) . To have different test weights, the weights can differ, for example, in material and / or in their internal structure, like in the size of a cavity made in them.

[0021] The processor operates the jig, including the robotic arm, to calibrate the force gauge of the calibrating jig.

[0022] In the example shown in Fig. 1, the disclosed catheter calibration apparatus includes a motorized arm that carries a weight in a bore for calibrating the force gauge. The apparatus further includes a calibration jig with automated force gauge calibration. The motorized arm is configured to place the test weight above the top surface of the gauge. Depending on design specifics, the arm can engage and disengage the jig by rotating (as seen in Fig. 2) or by being inserted linearly.

[0023] The arm comprises a bore at its distal end configured to hold the test weight so that, upon contact with the force gauge, the test weight freely disengages from the arm and rests on the gauge to perform the force gauge calibration. Lowering the arm is one way to cause the test weight to disengage freely. However, this method requires a more sophisticated robotic arm (e.g., one with two degrees of freedom instead of one) . Another way, shown in Fig. 3D, is to move the force gauge upwards using a mechanical stage configured to lift and lower the gauge along a vertical axis (e.g., during catheter calibration) .

[0024] In an example, the processor of the apparatus is configured to (i) operate the motorized arm to place the test weight above the gauge, (ii) operate the mechanical stage to lift the gauge to the test position, (iii) receive force measurements from the gauge, and (iv) generate calibration data for the gauge based on the force measurements. The processor is further configured to measure the gauge's zero-weight force and generate the calibration linear curve (e.g., calculate two coefficients of a line) based on the additional zero-weight force.

[0025] In some examples, for the test weight to disengage from the bore when lifted by the gauge, the bore and the test weight have matched conical shapes that allow the test weight. For example, an inverted conical frustum-shaped weight is provided, that fits into a conical bore in the arm. The shape of the weight is configured to disengage when supported by a rim formed around the bore based on applying a normal force on its lower surface. In other examples, free disengagement is achieved by the bore and the test weight having another complementary shape (e.g., the bore has an opening, and the test weight comprises a vertical leg that fits in the opening) .

[0026] DETAILED DESCRIPTION OF THE DRAWINGS

[0027] CALIBRATION APPARATUS DURING AUTOMATIC FORCE SELF¬

[0028] CALIBRATION MODE

[0029] Fig. 1 is a schematic block diagram of a catheter contact force calibration apparatus 100, according to an example of the present disclosure. Apparatus 100 comprises a jig 200 and a motorized arm 210 that holds a test weight 250. Jig 200, which is described in detail in Fig. 2, is otherwise configured to hold a catheter distal end (not shown) and operates to apply contact force in a plurality of directions. Optionally, the force applied selectively deflects and / or presses the distal end in a defined manner and measures the resulting forces using a force gauge 208.

[0030] A processor 102 comprising a memory 103 periodically calibrates gauge 208 and / or responds to detected changes in ambient conditions, such as those detected by a temperature sensor 223 and a humidity sensor 225. Processor 102 stores the calibration result (e.g., two coefficients of a linear calibration curve equation) in memory 103 for use during catheter manufacturing testing.

[0031] Motorized arm 210 is coupled to an axle 212 that is movable by a processor-controlled motor 214. To calibrate the force gauge, the processor first moves (e.g., rotates) arm 210 to bring test weight 250 mounted on arm 210 over force gauge 208.

[0032] Processor 102 then commands a z-stage 206 to vertically move a predefined distance to lift test weight 250 (e.g., to have test weight 250 disengage from a rim of the bore and rest on gauge 208) by moving the top surface of gauge 208 into contact with the test weight.

[0033] Force measurement can now take place. The inverted conical shapes of test weight 250 and a rim 216 of a bore 217 in arm 210 enable the weight to freely disengage from the arm when the Z stage lifts the weight, thereby preventing any effect of arm 210 on the force measurement.

[0034] Once the processor receives the force measurement, it commands stage 206 to move downward by a predefined distance so that the test weight returns to its place in bore 217. Then, the processor rotates arm 210 back to its idle position. The jig's vacated inner space is now available for insertion of the next distal end assembly of a catheter to run the calibration procedure.

[0035] Fig. 1 is provided as an example; thus, other layouts are possible to achieve the same effect. For example, test weight 250 may be moved horizontally into position using a linear stage rather than by rotation. The weight can freely disengage from the arm using an arm that can also move vertically .

[0036] While Fig. 1 depicts a conical configuration of test weight 208 and test weight rim 216 of bore 217, there may be many other configurations for lifting the test weight vertically off arm 210 by z-stage 206. For example, the bore and the test weight can have complimentary shapes that allow the test weight to be freely lifted vertically. For example, the bore has an opening (e.g., a hexagonal-shaped aperture) , and the test weight comprises a vertical leg that fits in the opening. The horizontal leg of the test weight has a larger size (and / or is shaped differently) than that of the bore aperture so that the test weight is suspended on its hori zontal portion while being carried by the bore .

[0037] JIG OPERATED IN AUTOMATIC FORCE GAUGE CALIBRATION MODE

[0038] Fig . 2 is a schematic perspective view of j ig 200 of apparatus 100 of Fig . 1 and of robotic arm 210 of apparatus 100 , which together enable automatic calibration of force gauge 208 of the j ig, according to an example of the present disclosure .

[0039] Jig 200 includes a base 201 fitted with a bridge 202 that can be pivoted in a 6 direction using a motori zed cam 203 . Bridge 202 has a catheter shaft holding apparatus 205 and a motori zed azimuthal stage 204 that can rotate the shaft in a ( / ) direction . Jig 200 includes a Z-stage 206 supporting a force gauge 208 that can li ft the force gauge to engage with either the distal end assembly of the catheter (not shown) during catheter calibration and li ft weight 250 for force gauge calibration . All motions controlled by processor 102 are used to selectively twist and deflect the distal end assembly .

[0040] As noted above , processor 102 runs a gauge calibration on a periodic basis and when a change in ambient conditions is detected by, for example , a temperature sensor 223 and a humidity sensor 225 .

[0041] To calibrate force gauge 208 , the processor moves arm

[0042] 210 ( e . g . , rotates over an angle Q using axle 212 that is driven by motor 214 ) to bring the test weight ( seen in Figs. 1 and 3) that rests in a conical rim 216 of bore 217, into a test position over force gauge 208.

[0043] Then processor 102 commands z-stage 206 to vertically move a predefined height and lift the test weight by the top surface of gauge 208. The conical shape of the test weight and rim 216 of bore 217 in arm 210 offsets any effect of arm 210 on the force measurement, as seen in Fig. 3. After force measurements are completed, the processor commands stage 206 to move downward (e.g., by the predefined height) , returning the test weight to its place in bore 217 in arm 210.

[0044] Figs. 3A, 3B, 3C, and 3D are schematic figures of the elements comprised in the apparatus of Fig. 1 that enable automatic calibration of force gauge 208, according to an example of the present disclosure. Fig. 3A is a top view of arm 210 and the trajectory, along the angle Q, that arm 210 moves relative to gauge 208. Fig. 3B is a top view of arm 210 when conical bore 217 is located over gauge 208.

[0045] Fig. 3C is a side view of arm 210 when conical test weight 250, mounted on conical rim 216 of bore 217, is located over gauge 208 at a predefined height 218 over base 201.

[0046] Fig. 3D is a side view showing conical test weight 250 lifted by z-stage 206 in preparation for test weight measurement. As seen, test weight 250 lies on gauge 208 so that it is disengaged from arm 210. METHOD OF AUTOMATIC CALIBRATION OF FORCE GAUGE USING

[0047] CONICAL STRUCTURE

[0048] Fig. 4 is a flow chart that schematically describes the automatic calibration of force gauge 208 of jig 200 of Fig. 2 using apparatus 100 of Fig. 1, according to an example of the present disclosure. The algorithm, according to the present example, carries out a process that begins at calibration initiation step 402, during which processor 102 initiates gauge calibration upon a change in ambient conditions, such as those detected by a temperature sensor 223 and a humidity sensor 225. Processor 102 also periodically initiates the calibration. The processor is configured to detect that a catheter is mounted in jig 200 using a sensor 207 disposed on the catheter calibration jig and deactivate the automatic calibration of force gauge 208 if a catheter is mounted in jig 200.

[0049] While force gauge calibration occurs, the processor indicates to a user that the force gauge calibration is ongoing (e.g., by turning on a red light) .

[0050] At zero force calibration step 404, processor 102 measures the zero force (no weight) reading of gauge 208 to obtain a zero-force data point of the linear calibration curve .

[0051] At arm positioning step 406, the processor rotates arm 210 to bring test-weight 250 over force gauge 208.

[0052] Next, at lifting test weight step 408, processor 102 commands z-stage 206 to vertically move a predefined height to lift test weight 250 by the top surface of gauge 208.

[0053] The processor measures test weight 250 at test weight measuring step 410. The conical shape of the test weight 250, and the weight bore in arm 210, offsets any effect of arm 210 on the force measurement.

[0054] Based on its exact weight, the processor calculates the linear calibration curve for gauge 208 at calibration curve calculation step 412.

[0055] The processor stores the calibration curve, or the two coefficients of the linear equation of the calibration curve, in its a memory 103, at coefficients storing step 414.

[0056] After the processor receives force measurement and successfully calculates the calibration coefficients, processor 102 commands stage 206 to move down so that test weight 250 returns to conical rim 216 of bore 217 in arm 210 at lowering test weight step 416.

[0057] At arm repositioning step 418, the processor rotates arm 210 back to its idle position to allow the next catheter assembly to be calibrated.

[0058] Finally, at apparatus readiness indication step 420, processor 102 indicates (e.g. by turning on a green light) that jig 200 is ready to calibrate the next catheter assembly .

[0059] The processor can be further configured to report the force gauge calibration results (e.g., history of coefficient values) e.g. on a computer display.

[0060] The flowchart described in Fig. 4 is simplified for clarity of presentation. Other steps may be included in the method, such as turning on a red light to alert a user that apparatus 100 is undergoing force gauge calibration. EXAMPLES

[0061] Example 1

[0062] Apparatus (100) for calibrating a force-sensitive catheter (14) , the apparatus comprising a test weight (250) , a motorized arm (210) , and a processor (102) . The test weight (250) is configured for calibrating a force gauge (208) of a catheter calibration jig (200) of the apparatus (100) , the test weight (250) having a shape that is configured to disengage when supported by a rim (216) formed around a bore (217) based on applying a normal force on its lower surface. The motorized arm (210) carries the test weight (250) , the motorized arm configured to place the test weight (250) above the top surface of the force gauge (298) , the arm (210) comprising bore (217) at its distal end, the rim (216) is sized to support the test weight (250) so that lifting the force gauge (208) to a test position along the vertical axis causes the test weight (250) to freely disengage from the arm (210) and rest on the gauge (208) . The processor (102) is configured to (i) operate the motorized arm (210) to place the test weight (250) above the gauge (208) , (ii) operate a mechanical stage (206) to lift the gauge (208) to the test position, (iii) receive force measurements from the gauge (208) , and (iv) generate calibration data for the gauge (208) based on the force measurements.

[0063] Example 2 The apparatus (100) according to example 1, wherein the test weight (250) has an inverted conical frustum shape .

[0064] Example 3

[0065] The apparatus (100) according to any of examples 1 and 2, wherein the processor (102) is further configured to measure a zero-weight force on the gauge (208) , and to generate the calibration data based on the zero-weight force .

[0066] Example 4

[0067] The apparatus (100) according to any of examples 1 through 3, wherein the processor (102) is configured to generate the calibration data by calculating two coefficients of a linear function based on the zero-weight force and the test weight (250) measurements.

[0068] Example 5

[0069] The apparatus (100) according to any of examples 1 through 4, wherein the apparatus further comprises at least one temperature sensor (223) and a humidity sensor (225) , and wherein the processor (102) is configured to initiate the calibration based on an output of at least one of the sensors (223, 225) .

[0070] Example 6 The apparatus (100) according to any of examples 1 through 5, wherein the processor (102) is configured to detect that a catheter is mounted in the jig (200) using a sensor (207) disposed on the jig.

[0071] Example 7

[0072] The apparatus (100) according to any of examples 1 through 6, wherein the processor (102) is configured to deactivate automatic calibration of the force gauge (208) if a catheter is mounted in the catheter calibration jig (200) .

[0073] Example 8

[0074] The apparatus (100) according to any of examples 1 through 7, wherein the processor (102) is configured to indicate to a user that the calibration of the force gauge (208) is ongoing.

[0075] Example 9

[0076] The apparatus (100) according to any of examples 1 through 9, wherein the processor (102) is configured to report the force gauge (208) calibration results.

[0077] Example 10 The apparatus (100) according to any of examples 1 through 9, wherein the arm (210) is configured to accept different test weights (250) depending on an expected range of contact forces.

[0078] Example 11

[0079] Method for calibrating a force-sensitive catheter (14) , the method comprising supporting a test weight (250) for calibrating a force gauge (208) of a catheter calibration jig (200) by a rim (216) formed around a bore (217) , the test weight (250) having a shape that is configured to disengage when applying a normal force on its lower surface. The test weight is placed above a top surface of the force gauge (208) using a motorized arm (210) that carries the test weight, the arm (210) comprising bore (217) at its distal end, the rim (216) is sized to support the test weight (250) so that lifting the force gauge (208) to a test position along the vertical axis causes the test weight to freely disengage from the arm and rest on the gauge. The motorized arm (210) is operated to place the test weight above the gauge (208) . A mechanical stage (206) is operated to lift the gauge (208) to the test position. Force measurements are received from the gauge. Calibration data for the gauge (208) is generated based on the force measurements .

[0080] The examples described above are cited by way of example, and the present disclosure is not limited by what has been particularly shown and described hereinabove. Rather the scope of the disclosure includes both combinations and sub-combinations of the various features described hereinabove , as well as variations and modi fications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art .

Claims

CLAIMS1. Apparatus for calibrating a force-sensitive catheter, the apparatus comprising: a test weight for calibrating a force gauge of a catheter calibration jig of the apparatus, the test weight having a shape that is configured to disengage when supported by a rim formed around a bore based on applying a normal force on its lower surface; a motorized arm that carries the test weight, the motorized arm configured to place the test weight above a top surface of the force gauge, the arm comprising a bore at its distal end, the rim is sized to support the test weight so that lifting the force gauge to a test position along the vertical axis causes the test weight to freely disengage from the arm and rest on the gauge; and a processor configured to (i) operate the motorized arm to place the test weight above the gauge, (ii) operate a mechanical stage to lift the gauge to the test position, (iii) receive force measurements from the gauge, and (iv) generate calibration data for the gauge based on the force measurements .

2. The apparatus according to claim 1, wherein the test weight has an inverted conical frustum shape.

3. The apparatus according to claim 1 or claim 2, wherein the processor is further configured to measure a zero-weight force on the gauge, and to generate the calibration data based on the zero-weight force.

4. The apparatus according to claim 3, wherein the processor is configured to generate the calibration data by calculatingtwo coefficients of a linear function based on the zero-weight force and the test weight measurements.

5. The apparatus, according to any one of claims 1-4, wherein the apparatus further comprises at least one temperature sensor and a humidity sensor, and wherein the processor is configured to initiate the calibration based on an output of at least one of the sensors.

6. The apparatus, according to any one of claims 1-5, wherein the processor is configured to detect that a catheter is mounted in the jig using a sensor disposed on the jig.

7. The apparatus, according to any one of claims 1-6, wherein the processor is configured to deactivate automatic calibration of the force gauge if a catheter is mounted in the catheter calibration jig.

8. The apparatus, according to any one of claims 1-7, wherein the processor is configured to indicate to a user that the calibration of the force gauge is ongoing.

9. The apparatus, according to any one of claims 1-8, wherein the processor is configured to report the force gauge calibration results.

10. The apparatus, according to any one of claims 1-9, wherein the arm is configured to accept different test weights depending on an expected range of contact forces.

11. Method for calibrating a force-sensitive catheter, the method comprising: supporting a test weight for calibrating a force gauge of a catheter calibration jig by a rim formed around a bore,the test weight having a shape that is configured to disengage when applying a normal force on its lower surface ; placing the test weight above a top surface of the force gauge using a motori zed arm that carries the test weight , the arm comprising a bore at its distal end, the rim is si zed to support the test weight so that li fting the force gauge to a test position along the vertical axis causes the test weight to freely disengage from the arm and rest on the gauge ; operating the motori zed arm to place the test weight above the gauge ; operating a mechanical stage to li ft the gauge to the test position; receiving force measurements from the gauge ; and generating calibration data for the gauge based on the force measurements .12 . The method according to claim 11 , wherein the test weight has an inverted conical frustum shape .13 . The method according to claim 11 or claim 12 , and comprising measuring a zero-weight force on the gauge , and generating the calibration data based on the zero-weight force .14 . The method according to claim 13 , wherein generating the calibration data comprises calculating two coef ficients of a linear function based on the zero-weight force and the test weight measurements .15 . The method, according to any one of claims 11- 14 , and comprising initiating the calibration based on an output of at least one of a temperature sensor and a humidity sensor .

16. The method, according to claim 11, and comprising detecting that a catheter is mounted in the jig using a sensor disposed on the jig.

17. The method, according to any one of claims 11-16, and comprising deactivating automatic calibration of the force gauge if a catheter is mounted in the catheter calibration jig-18. The method, according to any one of claims 11-17, and comprising indicating to a user that the calibration of the force gauge is ongoing.

19. The method, according to any one of claims 11-18, and comprising reporting the force gauge calibration results.

20. The method, according to any one of claims 11-19, and comprising accepting different test weights depending on an expected range of contact forces.

Images