JP4350004B2 - 3D drag sensor - Google Patents

Description

  The present invention relates to a three-dimensional drag sensor having a center hole suitable for mounting on the tip of an endoscope or a catheter, and in particular, three-dimensional capable of measuring the contact force and the direction of the contact force between a body wall and the sensor. The present invention relates to a drag sensor.

Currently, minimally invasive and non-invasive treatments that can reduce the burden on patients are attracting attention, and typical medical devices include catheters and endoscopes used in the body lumen. These devices are often difficult to use under the complicated shape of the lumen, and therefore, an active catheter (see, for example, Non-Patent Document 1) whose tip freely deforms according to the body structure and insertion into the body. An optical fiber pressure sensor (see, for example, Non-Patent Document 2) that measures blood pressure in real time has been developed.
Research has also been conducted on devices that measure the pushing force when inserting an endoscope (see, for example, Non-Patent Document 3), and bending stiffness of the endoscope itself that greatly affects insertion characteristics (for example, Non-patent document 4).
Details of the outline, research on active catheter systems, structure of catheters with other degrees of freedom, evaluation of experimental results and motion characteristics, Journal of the Robotics Society of Japan 1996, 820-835 J. A. Wehrmeyer et al., Colonoscope flexural rigidity measurement Medical & Bilogical Engineering & Computing, July 1998, 475-479 C. A. Mosse et al., Device for measuring the forces exerted on thee shaft of an involving during colonescopy, Medical & Biological Engineering & Computing, March 1998, 186-190 Haga et al., Fiber Optic Pressure Sensor for Catheter Measurement and Control Vol.39 No.4 2000, 292-295

  Since catheters and endoscopes always have a risk of excessive stimulation when used, it is important for doctors to know the state of catheters in the body for safe and rapid treatment. However, at present, the information that allows the doctor to know the internal state of the catheter is obtained from force information as a response at the catheter root that the doctor feels during the catheter operation and the body lumen image from the distal end of the catheter. Visual information is the main, and it is generally difficult to safely operate the catheter with this information alone. Therefore, sensors that measure the contact force between the catheter tip and the body wall and the omnidirectional posture of the catheter tip are being developed, but since these sensors are attached to the catheter tip, work such as treatment forceps The advantage of a catheter that can perform diagnosis and treatment at the same time could not be fully utilized.

  The present invention has a large center hole in which a forceps or the like can be inserted in the center in alignment with the distal end of the endoscope or catheter in consideration of the operation of the endoscope or catheter, and between the distal end of the catheter and the body wall. An object of the present invention is to provide a three-dimensional drag sensor capable of measuring an omnidirectional posture such as contact force and catheter tip.

In order to achieve the above object, a three-dimensional drag sensor according to the present invention is a three-dimensional drag sensor having a center hole suitable for being mounted at the tip of an endoscope or a catheter, etc. It is characterized in that three or more strain gauges formed are arranged at equal intervals around the center hole.
The three-dimensional drag sensor of the present invention is characterized in that the insulating film is formed of a polyimide foil.
The three-dimensional drag sensor of the present invention is characterized in that a strain gauge is formed on an elastic thin plate.
The three-dimensional drag sensor of the present invention is characterized in that a hemispherical elastic body is mounted on the upper surface of the strain gauge.
The three-dimensional drag sensor of the present invention is a three-dimensional drag sensor provided with a center hole suitable for mounting on the tip of an endoscope or a catheter, etc., and an elastic member is provided on the side in contact with the endoscope or the catheter or the like. A strain gauge formed of a thin layer resistance material on an insulating film on an elastic thin plate having a center hole affixed to the upper surface of the substrate and equidistantly arranged around the center hole. 3 or more are attached to the elastic thin plate on the upper surface of the substrate and the lower surface of the hemispherical elastic body located above the strain gauge through an elastic thin plate thicker than the thickness of the strain gauge arranged between the strain gauges. It is characterized by being connected to a thin elastic plate.

The three-dimensional drag sensor of the present invention has the following excellent effects.
(1) Since it has a large center hole where forceps can be inserted in the center, there is no risk of obstructing the operation of therapeutic forceps even when attached to the tip of an endoscope or catheter. Can be treated at the same time.
(2) By providing three or more strain gauges at equal intervals around the center hole, it is possible to measure the omnidirectional posture.
(3) Accurate measurement can be performed by attaching a strain gauge to an elastic thin plate.
(4) By attaching a hemispherical elastic body to the upper surface of the strain gauge, it is possible to prevent damage to a human body or the like to be diagnosed or treated.

  The best mode for carrying out the three-dimensional drag sensor according to the present invention will be described below with reference to the drawings based on the embodiments.

1 is a front view of a three-dimensional drag sensor, and FIG. 2 is a cross-sectional view taken along line AA of FIG. In addition, the upper figure of FIG. 1 shows the state before an assembly for demonstrating each member, and the lower figure of FIG. 1 has shown the state after an assembly.
In FIG. 1, a three-dimensional drag sensor 1 is suitable for being mounted on the distal end of an endoscope or catheter 20 or the like, and is loaded with forceps or the like formed at the center of the endoscope or catheter 20 or the like. It has a center hole 2 aligned with a large center hole that can be formed. In this example, the diameter of the center hole 2 is about 8 to 12 mm.
A base 3 made of an elastic material such as rubber and having a center hole 2 is provided on the side in contact with the endoscope or the catheter 20, and an elastic thin plate 6 having the center hole 2 is attached to the upper surface of the base 3. Further, a hemispherical tip member 4 made of an elastic material such as rubber and having a center hole 2 is provided on the tip side of the three-dimensional drag sensor 1, and an elastic thin plate 7 is attached to the bottom surface of the tip member 4. .

As shown in FIG. 2, three or more strain gauges 5 are formed at equal intervals around the center hole 2, and in FIG. 2, there are three strain gauges 5 at 120 ° intervals. It is manufactured as an integral type provided with a strain gauge pattern, and is adhered to the elastic thin plate 6 on the upper surface of the base 3 using an adhesive, whereby the force and direction applied to the tip due to the deformation can be measured.
The tip member 4 has a hardness that does not affect the transmission of the force applied to the strain gauge 5, and the resistance of the strain gauge 5 is changed by the contact force transmitted through the tip member 4, and the resistance change is compensated for the Wheatstone bridge. In addition, the force in the triaxial direction is detected by converting it into an electrical signal using a dynamic strain amplifier. At that time, the strain is easily transmitted by the elastic thin plate 6 on the upper surface of the substrate 3 to which the strain gauge 5 is attached and the elastic thin plate 7 on the bottom surface of the tip member 4. Between the elastic thin plate 6 and the elastic thin plate 7, three small circular elastic thin plates 8 are arranged at equal intervals between three strain gauge patterns at intervals of 120 °, and fixed to the upper and lower elastic thin plates by adhesion or the like. Yes. The thickness of the elastic thin plate 8 is thicker than the thickness of the strain gauge 5, and the load acting on the tip member 4 is elastic on the upper surface of the substrate 3 through the elastic thin plate 7 on the bottom surface and the small circular elastic thin plate 8. It acts on the thin plate 6 and acts on three strain gauge patterns attached to the elastic thin plate 6.
As a material of the elastic thin plates 6, 7 and 8, for example, a material having elasticity such as a copper plate is desirable.
In addition, the center hole 2 is formed in advance by preparing the center hole 2 in the base 3, the elastic thin plate 6, the elastic thin plate 7 and the tip member 4, and assembling these components.

Next, an example of the above-described strain gauge pattern creation process will be described.
FIG. 3 shows a process for producing a strain gauge produced on a polyimide foil by using the lift-off method.
First, a resist is applied on the polyimide foil (FIG. 3A).
Next, patterning is performed to form a pattern (FIG. 3B).
Thereafter, using a Cu—Cr alloy target, a Cu—Cr alloy film is uniformly formed on the resist by sputtering (FIG. 3C).
Subsequently, the resist and unnecessary Cu—Cr alloy film are removed in acetone to obtain a target pattern (FIG. 3D).
The means for forming the alloy film on the resist is not limited to the sputtering method, but may be a vapor deposition method or the like. The material at that time may be a resistance material whose resistance changes due to strain, such as Ni—Cr.

FIG. 4 shows an integrated strain gauge fabricated on a polyimide foil.
In this example, a pattern was formed on the polyimide foil, other polymer is not limited to polyimide foil, S _i O ₂ film, etc., may be any insulating film. Further, as long as it is a technique capable of forming a strain gauge pattern, a printing method other than lithography may be used. Furthermore, an insulating film may be formed on the elastic thin plate 6, a strain gauge pattern may be formed thereon, and the elastic thin plate-insulating film-strain gauge may be integrated.

Based on FIG. 5, a method for detecting a force in three axial directions by converting a resistance change of the strain gauge 5 into an electrical signal using a Wheatstone bridge and a dynamic strain amplifier by a contact force transmitted via the tip member 4. I will explain.
Each gauge of the integrated strain gauge 5 provided with three strain gauge patterns around the center hole 2 at intervals of 120 ° is a resistor, and the three-dimensional drag sensor comes into contact with the object. The strain gauges I to III are deformed, and the magnitude of each of the resistances is minute but changes. This resistance change can be obtained as a differential voltage by passing through the bridge box. Since this differential voltage is very small, it is necessary to amplify it using a dynamic strain amplifier, and the weighting p and the angles φ and θ can be obtained by performing calculation processing by a computer using each obtained voltage value. it can.

6 and 7 show the relationship between the loads p and the angles φ and θ when the loads p and the angles φ and θ are obtained, FIG. 6 is a front view, and FIG. 7 is a plan view.

Now, as shown in FIGS. 6 and 7, as an experimental condition, the target surface and the three-dimensional drag sensor 1 are in surface contact, and the load P is installed so as to be applied from the vertical direction of the surface contact.
When the target surface is in contact with the three-dimensional drag sensor 1 at an angle, the angle from the vertical line when the sensor is viewed from the side is φ, and the angle based on the gauge when viewed from directly above is θ. By defining, it is possible to represent the contact position of the target surface.
Hereinafter, the output p of the three-dimensional drag sensor 1 is measured by changing the load p (N), the angle θ (deg), and the angle φ (deg), and the characteristics thereof are examined.
The output voltages obtained from the three gauges can be approximated by sinusoidal waveforms each having a phase difference close to 120 °, and it is known that the loads p and φ are proportional to the amplitude of the sinusoidal wave. Therefore, the relationship between the output from each sensor and the contact load p between the object and the contact angles θ and φ is the experimentally obtained correction values, ie, the amplitude coefficient A _i , the phase α _i , and the average output of B _i . It can be expressed as follows using the value.
Y _i = A _i φpcos (θ + α _i ) + B _i p
i = 1 to 3

By solving the above equations simultaneously, p and the contact angles θ and φ can be obtained. The calculation is as follows.
_{Q 1 = A 3 B 1 B} 2 {B 3 (B 2 Y 1 -B 1 Y 2) + B 2 (B 1 Y 3 -B 3 Y 1)}
_{Q 2 = A 1 B 2 B} 3 {B 3 (B 2 Y 1 -B 1 Y 2) + B 2 (B 1 Y 3 -B 3 Y 1)}
_{Q 3 = A 2 B 1 B} 3 {B 3 (B 2 Y 1 -B 1 Y 2) + B 1 (B 3 Y 2 -B 2 Y 3)}
_{Q 4 = A 3 B 1 B} 2 {B 3 (B 2 Y 1 -B 1 Y 2) + B 1 (B 3 Y 2 -B 2 Y 3)}
D = Q ₄ cos α ₃ -Q ₃ cos α ₂ -Q ₂ cos α ₁ + Q ₁ cos α ₃
E = Q ₁ sin α ₃ −Q ₂ sin α ₁ −Q ₃ sin α ₂ + Q ₄ sin α ₃
Then,
Θ = arctan {Q ₄ cos α ₃ −Q ₃ cos α ₂ −Q ₂ cos α ₁ + Q ₁ cos α ₃ / Q ₁ sin α ₃ −Q ₂ sin α ₁ −Q ₃ sin α ₂ + Q ₄ sin α ₃ }
When E <0, θ = Θ + 180 °
When D <0, E> 0, θ = Θ + 360 °
Otherwise, θ = Θ
Using the obtained θ, p and φ are obtained,
p = A ₂ Y ₁ cos (θ + α ₂ ) -A ₁ Y ₂ cos (θ + α ₁ ) / A ₂ B ₁ cos (θ + α ₂ ) -A ₁ B ₂ cos (θ + α ₁ )
φ = Y ₁ −B ₁ p / A ₁ pcos (θ + α ₁ )

As described above, the contact conditions p, θ, and φ can be obtained by solving simultaneous equations from the sensor output.
Therefore, an accuracy confirmation experiment was performed by the method shown in FIGS. The experiment method was performed in the same manner as the above characteristic measurement, and an experimental set value was obtained from the sensor output from the above formula, and an error from the set value was obtained. The results obtained are shown in Table 1. From the results, it was confirmed that the load and angle information can be specified by all the sensors with an error.

It is a front view of the three-dimensional drag sensor concerning an embodiment of the invention. It is an AA arrow line view of FIG. The manufacturing process of the strain gauge produced on the polyimide foil using the lift-off method which concerns on embodiment of this invention is shown. 1 shows an integrated strain gauge produced on a polyimide foil according to an embodiment of the present invention. It is the figure explaining the method of detecting the force of a triaxial direction by converting the resistance change of a strain gauge into an electrical signal using a Wheatstone bridge and a dynamic strain amplifier. It is a front view which shows the relationship of angle (phi) and (theta) at the time of calculating | requiring the load p of contact state and angle (phi), (theta) which concerns on embodiment of this invention. It is a top view which shows the relationship of the angle (phi) and (theta) at the time of calculating | requiring the load p of contact state and angle (phi), (theta) which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3D drag sensor 2 Center hole 3 Base | substrate 4 Tip member 5 Strain gauge 6 Elastic thin plate 7 Elastic thin plate 8 Small circular elastic thin plate

Claims (1)

  In a three-dimensional drag sensor provided with a center hole suitable for being mounted on the tip of an endoscope or a catheter, the side contacting the endoscope or the catheter is provided with a base made of an elastic member and having a center hole. Three or more strain gauges made of a thin layer resistive material on an insulating film are arranged on the elastic thin plate having a center hole attached to the upper surface of the substrate at equal intervals around the center hole. The elastic thin plate on the upper surface of the substrate and the elastic thin plate attached to the lower surface of the hemispherical elastic body located above the strain gauge are connected via an elastic thin plate thicker than the thickness of the strain gauge disposed on Characteristic 3D drag sensor.

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