WO2021245849A1

WO2021245849A1 - Medical treatment instrument unit, medical manipulator, and medical robot

Info

Publication number: WO2021245849A1
Application number: PCT/JP2020/021984
Authority: WO
Inventors: 大輔原口
Original assignee: リバーフィールド株式会社
Priority date: 2020-06-03
Filing date: 2020-06-03
Publication date: 2021-12-09

Abstract

A medical manipulator according to one aspect of the present invention which has sufficient bending strength, treatment ability, and durability, and drives a treatment unit using a drive unit is provided with: a shaft having a transmission mechanism for transmitting driving force from the drive unit to the treatment unit; and a soft joint part provided between the shaft and the treatment unit. The soft joint part has: disk bodies disposed in multiple stages at predetermined intervals in a first direction along the axis of the shaft; and connection sections that connect adjacent disk bodies and extend in a second direction perpendicular to the first direction. When viewed in the first direction, adjacent connection parts extend in mutually different directions. The soft joint part is characterized by being made from a resin material having a bending deformation range (bending strength/flexural modulus) of 3.0% or more, a compressive strength of 50 MPa or more, and a flexural modulus of 10 GPa or less.

Description

Medical treatment tool unit, medical manipulator and medical robot

The present invention relates to a medical treatment tool unit driven by a drive unit, a medical manipulator including such a medical treatment tool unit, and a medical robot including such a medical manipulator.

A medical manipulator that drives a treatment part such as forceps by a drive unit is expected as a technology that accurately reflects the movement of the operator's hand to reduce the burden on the operator and patient by surgery and increase the possibility of telemedicine. ing.

Patent Document 1 discloses a flexible tube of a medical manipulator which is excellent in torsional rigidity, load bearing capacity, and flexibility while being miniaturized. This flexible tube is formed between a plurality of ring portions connected in the axial direction, a tube connecting portion that partially connects the adjacent ring portions in the axial direction, and a ring portion adjacent in the axial direction. It is divided on both sides in the circumferential direction of the tube joint and is provided with slits that allow bending of the flexible tube due to bending of the tube joint. In this tube joint, the dimension in the circumferential direction gradually decreases from one side in the axial direction which is the fixed side at the time of bending to the other side in the axial direction which becomes the movable side at the time of bending.

Patent Document 2 discloses a joint portion and a medical instrument of a medical instrument that facilitates operability of the joint portion and the surgical instrument. The joint part of this medical device has a highly flexible outer shell part formed in a cylindrical shape having a space inside, and a tubular part that is arranged in the inner space of the outer shell part and has a higher compression rigidity than the outer shell part. The core material tube formed in the core material tube and the cable used for operating the surgical instrument are inserted inside the core material tube, and the material has a smaller coefficient of friction against the cable than the core material tube. The formed resin tube is provided.

Japanese Unexamined Patent Publication No. 2019-34082 Japanese Unexamined Patent Publication No. 2020-18835

In a medical manipulator, a flexible joint that bends a treatment part such as forceps with multiple degrees of freedom (DOF) is indispensable in a robot minimally invasive surgery system. A medical manipulator having such a flexible joint portion is required to have sufficient bending force, treatment force (grip force) and durability required for surgery.

An object of the present invention is to provide a medical treatment tool unit having sufficient bending force, treatment force and durability. The present invention also aims to provide a medical manipulator equipped with such a medical treatment tool unit, and to provide a medical robot equipped with such a medical manipulator and capable of estimating force.

In order to solve the above problems, one aspect of the present invention is a medical treatment tool unit having a treatment unit driven by a drive unit, and a shaft having a transmission mechanism for transmitting a driving force from the drive unit to the treatment unit. , A flexible joint portion provided between the shaft and the treatment portion. The flexible joint portion connects between a disk body arranged in a plurality of stages in a first direction along the axis of the shaft at predetermined intervals and an adjacent disk body, and extends in a second direction orthogonal to the first direction. It has a connecting portion which is present and has a connecting portion in which the extending directions of the adjacent connecting portions when viewed in the first direction are different from each other. The flexible joint portion was formed of a resin material having a bending deformation region (bending strength / flexural modulus) of 3.0% or more, a compressive strength of 50 MPa or more, and a bending elastic modulus of 10 GPa or less. It is a feature.

According to such a configuration, since the connecting portion having the highest stress at the time of bending in the flexible joint portion is made of a resin material having excellent bending characteristics, excellent flexibility can be ensured for a long period of time. Can be done.

In the medical treatment tool unit, the resin material for the flexible joint preferably contains at least one resin selected from the group consisting of PEEK, PEI, PPSU, PSU, PES, and POM-C. By using such a resin material for the flexible joint portion, it is possible to obtain the mechanical strength, long-term heat resistance and chemical resistance required for the flexible joint portion.

In the medical treatment tool unit, a set of one disk body and one connecting portion connected to the disk body is regarded as a one-stage structure, and the extending directions of the connecting portions in adjacent structures are set. It is preferable that they differ from each other by 45 degrees. As a result, in the structure in which the disk resistance and the connecting portion are combined, the positions of the adjacent connecting portions are arranged differently by 45 degrees when viewed in the first direction, and the stress concentration on the connecting portion with respect to the bending direction is relaxed. Will be done.

In the medical treatment tool unit, the number of stages of the structure in the flexible joint portion is preferably 9 or more and 12 or less. As a result, it is possible to increase the flexibility of bending while relaxing the stress concentration applied to the structure when the flexible joint portion bends.

In the medical treatment tool unit, it is preferable that the treatment portion has a grip portion and the extending direction of the connecting portion is not located along the occlusal surface of the grip portion arranged on the tip end side of the flexible joint portion. This makes it easier to bend in the direction along the occlusal surface of the grip portion.

The medical treatment tool unit may have a spring portion or a flexible tube portion inserted in the center of a plurality of discs. As a result, rigidity is added to the flexible joint portion by the spring portion or the flexible tube portion, and it becomes easy to obtain a treatment force.

The present invention provides, in another aspect, a medical manipulator including the above-mentioned medical treatment tool unit and a drive unit for driving the treatment tool of the medical treatment tool unit. The drive unit may drive the treatment tool by air pressure. In another aspect, the present invention is a medical robot provided with a medical manipulator that drives a treatment tool by this air pressure, and an air pressure sense estimation that estimates an external force applied to the treatment tool based on the measurement of the air pressure. Provide a medical robot equipped with a mechanism.

The medical manipulator according to the present invention provided in such a medical robot has excellent linearity between the operating force from the actuator and the operation, and also has excellent repetitive operation stability (bending durability), so that the air pressure sense is estimated. The accuracy of the external force estimated by the mechanism can be improved.

According to the present invention, it is possible to provide a medical manipulator having sufficient bending force, treatment force and durability. The present invention also provides a medical manipulator equipped with a medical treatment tool unit and a medical robot capable of estimating force.

It is a perspective view which illustrates the medical manipulator which concerns on this embodiment. It is a figure which illustrates the treatment part of the medical manipulator which concerns on this embodiment. It is a perspective view which illustrates the flexible joint part. It is a top view which illustrates the flexible joint part. It is a front view which illustrates the flexible joint part. It is a figure which illustrates the stress distribution in a flexible joint part. It is a schematic diagram of a pneumatic drive system with one degree of freedom. It is a figure which illustrates the state which the flexible joint part was bent. It is a figure which shows the relationship between the bending cylinder force and the bending angle of a flexible joint part. It is a figure which shows the relationship between the bending cylinder force and the bending angle of a flexible joint part. It is a figure which shows the relationship between the grip cylinder output and the length of a flexible joint part. It is a figure which shows the relationship between the bending cylinder force and the bending angle of a flexible joint part. It is a figure which shows the experimental apparatus. It is a figure which shows the force applied to the environment measured by the force sensor in two directions, and the state of a flexible joint part. It is a figure which shows the force applied to the environment measured by the force sensor in two directions, and the state of a flexible joint part. It is a figure which shows the result of the static load analysis of the flexible joint part which concerns on a comparative example. It is a figure which shows the result of the static load analysis of the flexible joint part (manufactured by PEEK) which concerns on this embodiment. It is a block diagram for demonstrating the force sense estimation mechanism of the medical robot which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same members are designated by the same reference numerals, and the description of the members once described will be omitted as appropriate.

(Composition of medical manipulator)
FIG. 1 is a perspective view illustrating the medical manipulator according to the present embodiment.
FIG. 2 is a diagram illustrating a treatment unit of the medical manipulator according to the present embodiment.
The medical manipulator 1 according to the present embodiment includes a medical treatment tool unit provided with a treatment unit 60 and a drive unit 50 for driving the treatment unit 60. For the drive unit 50, for example, a pneumatic cylinder is used. In the present embodiment, the forceps unit 100 including the treatment portion 60 having the grip portion 61 will be described as a specific example of the medical treatment tool unit.

The forceps unit 100 (medical treatment tool unit) included in the medical manipulator 1 is provided between the shaft 20 having a transmission mechanism for transmitting a driving force from the drive unit 50 to the treatment unit 60, and between the shaft 20 and the treatment unit 60. A flexible joint portion 10 is provided. In the present embodiment, the direction along the axis of the shaft 20 is referred to as the X direction (first direction), one of the directions orthogonal to the X direction is referred to as the Y direction, and the X direction and the direction orthogonal to the Y direction are referred to as the Z direction. I will decide.

A plurality of

wires

211, 212, and 213 are inserted in the shaft 20 as a part of the transmission mechanism, and the power from the drive unit 50 is transmitted to the grip portion 61 of the forceps unit 100. The forceps unit 100 includes wires 211 for opening and closing the grip portion 61, and

wires

212 and 213 for bending the flexible joint portion 10 to adjust the orientation of the grip portion 61.

For example, a slide cam 62 is provided in the grip portion 61, and the slide cam 62 is operated by a wire 211 inserted in the center of the shaft 20 to open and close the grip portion 61. For example, pulling the wire 211 closes the grip portion 61, and returning the wire 211 opens the grip portion 61.

The

wires

212 and 213 are inserted at symmetrical positions about the wires 211. By pulling one of the

wires

212 and 213 and extending the other, the flexible joint portion 10 can be bent and the direction of the grip portion 61 can be changed. Although not shown in FIG. 2, a set of wires different from the set of

wires

212 and 213 is also provided, and the

wires

212 and 213 are bent in a direction orthogonal to the bending direction of the flexible joint portion 10. You can do it. By balancing these wire operations, the flexible joint portion 10 can be bent 360 degrees in any direction when viewed in the X direction.

FIG. 3 is a perspective view illustrating the flexible joint portion.
FIG. 4 is a plan view illustrating the flexible joint portion.
FIG. 5 is a front view illustrating the flexible joint portion.
The flexible joint portion 10 is formed of a resin material. The flexible joint portion 10 connects between the discs 11 arranged in a plurality of stages in the X direction at predetermined intervals and the adjacent discs 11, and is connected to each other in a second direction (direction along the YZ plane) orthogonal to the X direction. ) With a connecting portion 12 extending. The flexible joint portion 10 has a length of about 10 mm (mm) in the X direction and a diameter of about 5 mm. The thickness of one disk body 11 is about 0.4 mm, and the distance between adjacent disk bodies 11 is about 0.5 mm. The thickness of the connecting portion 12 is about 0.4 mm, and extends so as to pass through the center (center seen in the X direction) of the flexible joint portion 10 (extending in the radial direction of the disk body 11).

In the flexible joint portion 10, the pair of one disk body 11 and one connecting portion 12 connected to the disk body 11 is regarded as a one-stage structure ST, and the connecting portion 12 in the adjacent structure ST is used. The extending directions are provided so as to differ from each other by 45 degrees. That is, when viewed in the X direction, the connecting portions 12 are installed so as to be offset by 45 degrees in the extending direction. By installing the connecting portion 12 in this way, stress concentration on the connecting portion 12 with respect to the bending direction of the flexible joint portion 10 is alleviated, and both strength and flexibility of the flexible joint portion 10 are achieved. ..

The number of stages of the structure ST in the flexible joint portion 10 is preferably 9 or more and 12 or less. If the number of steps of the structure ST is less than 9, it becomes difficult to secure the flexibility when bending the flexible joint portion 10, and if it is more than 12 steps, it becomes difficult to secure the strength of the flexible joint portion 10 in the X direction.

As shown in FIG. 5, a hole h1 through which the wire 211 is inserted penetrates through the center of the flexible joint portion 10 when viewed in the X direction, and the

wires

212 and 213 are formed on a predetermined circumference centered on the center of the flexible joint portion 10. A plurality of holes h2 through which the wire is inserted penetrates. The diameter of the hole h1 is about 1.8 mm, and the diameter of the hole h2 is about 0.5 mm.

In the flexible joint portion 10 used in the medical manipulator 1 according to the present embodiment, the bending deformation region (bending strength / flexural modulus) is 3.0% or more, the compressive strength is 50 MPa or more, and the bending elasticity. It is made of a resin material having a modulus of 10 GPa or less. As described above, when the flexible joint portion 10 in which the structure ST of the disk body 11 and the connecting portion 12 is provided in a plurality of stages is formed of a resin material, the resin material within the range of the above characteristics can be used. The connecting portion 12, which has the highest stress during bending, has excellent bending characteristics. Therefore, excellent flexibility can be ensured for a long period of time as the flexible joint portion 10 made of the resin material.

The resin material for the flexible joint portion 10 as described above includes a group consisting of PEEK (Polyetheretherketone), PEI (polyetherimide), PPSU (Polyphenylsulfone), PSU (Polysulfone), PES (Polyethersulfone), and POM-C (polyacetal copolymer). At least one selected resin is included. The resin material used for the flexible joint portion 10 will be described later.

Further, it is preferable that the extending direction of the connecting portion 12 is not located in the direction along the occlusal surface of the grip portion 61 arranged on the distal end side of the flexible joint portion 10 (Y direction in FIGS. 1 and 2). This makes it easier to bend in the direction along the occlusal surface of the grip portion 61. That is, the wire 211 is pulled when the grip portion 61 is closed, and a force is applied to the flexible joint portion 10 in the compression direction. In this state, a force is required to bend the flexible joint portion 10 as compared with the case where no force is applied to the flexible joint portion 10 in the compression direction. In the forceps unit 100, an operation of bending along the occlusal direction is performed with the grip portion 61 closed. Since the extending direction of the connecting portion 12 is not located along the occlusal surface, it becomes easy to perform the bending operation along the occlusal surface even when the grip portion 61 is closed.

Here, the inventor of the present application has found the present invention by conducting various studies on the resin material in the flexible joint portion 10 of the medical manipulator 1 according to the present embodiment. The examination is shown below.

A robot forceps provided with a flexible joint (an example of a medical manipulator 1) has a problem of a trade-off relationship between rigidity characteristics and flexibility characteristics at a joint with a metal part. To solve this problem, the inventor of the present application considers that the flexible joint portion 10 is made of super engineering plastic (SEP) widely used in medical equipment because of its excellent heat resistance, chemical stability, and mechanical strength. investigated.

The prototype of the flexible joint 10 is designed using polyetheretherketone (PEEK) with 12 machined slits, and the bending and gripping movements of the forceps unit 100 are realized by wire actuation. To. The results of the performance evaluation show that the flexible joint portion 10 made of PEEK can maintain the bending range even when a compressive force in the axial direction (X direction) is applied.

The flexible joint portion 10 made of PEEK is durable against a compressive force of 30 Newton (N), and the relationship between the degree of compression and the compressive force is linear. The flexible joint portion 10 made of PEEK can withstand a maximum of 10,000 bendings without significantly changing the mechanical properties of the bending. The flexible joint portion 10 has sufficient rigidity to output a force exceeding 1.2 N to the environment from the grip portion 61 of the forceps unit 100. The experimental results by the inventor of the present application show that the developed forceps unit 100 has the basic feasible performance of robotic surgery.

Next, the study of a specific resin material for the flexible joint portion 10 conducted by the inventor of the present application will be described in detail.

(Section 1)
Multi-degree of freedom (DOF) is essential for robotic forceps (medical manipulator 1) used in robotic minimally invasive surgical systems. This study focuses on the mechanism of the distal bending joint (flexible joint 10) of a robotic forceps (medical manipulator 1).

The number of parts in the flexible continuous joint is small, and small spare parts such as shafts, bearings, and pulleys are not required, so it is superior to the rigid link joint in terms of mechanical simplicity and miniaturization. Ding et al. Has developed an insertable robot effector platform equipped with a multi-backbone continuum mechanism for realizing bending motion (Non-Patent Document 1). Haraguchi et al. Have proposed a pneumatically driven multi-DOF forceps using a machined spring in combination with a backbone structure of a NiTi superelastic wire (Non-Patent Document 2). Hu et al. Has developed a flexible suture robot using two coil spring bending portions that rotate in the pitch direction and the yaw direction, respectively (Non-Patent Document 3).

Many of these flexible continuum joints have shown great flexibility by adopting a wire actuation mechanism to realize bending motion. However, the high tension of the working wire causes excessive compression of the flexible joint. Therefore, attention should be paid to the rigidity in the axial direction (X direction). The above-mentioned flexible continuum joint is mainly made of a metal material such as a titanium alloy or stainless steel. Metallic bend joints are difficult to maintain in terms of both compressive stiffness and bending flexibility.

Apart from the elastic continuum element, the other group uses a "quasi-flexible" joint consisting of stacked rigid discs (Non-Patent Documents 4 and 5) or rigid portions (Non-Patent Document 6) in the axial direction (X direction). ) Is increased in rigidity. However, since the bending direction and bending range are limited at each part, the rigid disk or the mechanism connecting the rigid parts increases the length of the flexible joint, which increases the bending radius of the joint and bends. Bending dexterity is reduced.

On the other hand, in order to perform laparoscopic surgery especially in a narrow space, it is necessary to satisfy the dual requirements of both rigidity and flexibility at the wrist joint joint of the robot forceps (medical manipulator 1). Therefore, it is expected that another material will be used instead of metal in the continuum joint.

Often, super engineering plastics (SEPs) are used in mechanical parts that face workloads in both the axial and bending directions (eg, flexible couplers made of polyacetal material). In addition, SEP often has excellent heat resistance, chemical stability, and the like. These advantages make SEP suitable for medical devices used in special environments such as insulation, sterilization, weight reduction, and non-magnetic.

Therefore, in this study, we propose a robot forceps (medical manipulator 1) in which the flexible joint portion 10 is made of SEP material due to the following three advantages. First, the SEP joint is more flexible in bending than the metal joint while maintaining moderate axial rigidity. Second, the SEP junction is reasonably applicable to medical energy devices such as electric knives due to its electrical insulation. Thirdly, it is possible to realize low-cost manufacturing by injection molding at the mass production stage.

Here, we will introduce the design and prototype of a robot forceps (medical manipulator 1) equipped with a SEP flexible wrist joint and its practical performance evaluation. Section 2 describes the SEP flexible joint structure and the operating mechanism of the robot forceps (medical manipulator 1). Section 3 shows some experimental results of the mechanical properties and durability of the SEP flexible joint for the practical performance evaluation of the SEP flexible joint.

(Section 2) Materials and Methods (2-1) Design and Mechanism of Robot Forceps As shown in FIG. 1, the robot forceps (medical manipulator 1), which is an example of the medical manipulator 1, is mainly driven by the forceps unit 100. It is equipped with a unit 50. The forceps unit 100 is connected to the drive unit 50 via the actuator adapter 30, and the actuator adapter 30 transmits the movement of the actuator in the drive unit 50 to the forceps unit 100 and easily separates the sterilized portion and the unsterilized portion. Designed to be able to.

The forceps unit 100 has a shaft 20, a flexible joint portion 10 with two degrees of freedom bending, and a grip portion 61. The length of the shaft 20 is about 300 mm, and the diameter of the shaft 20 and the flexible joint portion 10 is 4.5 mm.

The drive unit 50 has five pneumatic cylinders, each with a position sensor, and performs two pairs of wire tendon drives for flexible joint control and one push-pull drive for grip control. Pneumatic cylinders generally have a good power-to-weight ratio, so the drive unit mechanism is small and lightweight. In addition, the high back-drivability makes it possible to estimate the external force.

As shown in FIG. 2, the length of the bent portion of the flexible joint portion 10 is as small as 10 mm. The bending motion of the flexible joint portion 10 is driven by four stainless steel wires (7 × 7 stranded wire, diameter: 0.36 mm). Note that FIG. 2 shows

wires

212 and 213, which are two of the four stainless steel wires. Opposite wires operate in pairs every two, and the tendon drive mechanism determines the bending motion with one degree of freedom (the mechanism for driving the bending motion by the drive unit will be described later).

A commercially available gripping forceps (Autonomy Lapro-Angle Instruments manufactured by Cambridge Endo) was used for the grip portion 61. The opening and closing movement is determined by push-pull operation from a central stainless steel wire (1 x 7 stranded wire, diameter: 0.75 mm). FIG. 2 shows wire 211 as a stainless steel wire. The slide cam 62 at the base of the grip portion 61 converts the linear motion of the wire 211 into the opening / closing motion of the grip portion 61 (maximum opening angle is 66 °).

(2-2) Guideline for selecting SEP material The flexible joint portion 10 is made of SEP material. In this study, the following seven SEP materials were selected as candidates. That is, polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyacetal copolymer (POM-C), polyetherimide (PEI), polyphenylsulfone (PPSU), and polysulfone (PSU). , Polyethersulfone (PES).

Table 1 shows the relevant characteristics of SEP candidates for the application of the flexible joint 10. All candidates have been verified to have sufficient biocompatibility for practical use as medical materials. In addition, all candidates other than POM have sufficient heat resistance (about 130 ° C.) for autoclave sterilization, and they also have chemical resistance to acute or alkaline chemicals for cleaning. There is.

In this study, the flexible joint portion 10 was manufactured using PEEK because of its excellent mechanical rigidity. Other materials may be used as long as they have certain advantages suitable for a given application.

The mechanical rigidity of PPS and PEI is good, but the problem is that they have low resistance to impact. Since PPSU, PSU, and PES are more flexible and have better formability than PEEK, manufacturing costs can be reduced by simplifying the design of the flexible joint 10, in this case flexible. The number of slit portions of the joint portion 10 is smaller, and the wall thickness can be increased. Also, if the forceps unit 100 is intended for single use with the flexible joint 10, POM (classified as a normal engineering plastic) can also be used.

Here, in addition to the above seven resin materials, PTFE and PP were also examined. Furthermore, SUS304 was also examined as a metal material. When the flexible joint portion 10 was constructed using PTFE and PP as the resin material, it was found that the strength of the flexible joint portion 10 was insufficient because the compressive strength was low (less than 50 MPa). Further, when the flexible joint portion 10 is configured by using SUS304, the bending deformation region is low (less than 3.0%) and the flexural modulus is high (more than 10 GPa). Therefore, when the flexible joint portion 10 is configured, a spring is used. There is no choice but to make it a structure, and some kind of reinforcing member is required.

From the above examination results, the resin material forming the flexible joint portion 10 has a bending deformation region (bending strength / flexural modulus) of 3.0% or more, a compressive strength of 50 MPa or more, and a bending elastic modulus. The one with a modulus of 10 GPa or less is suitable. The above seven resin materials meet all of these requirements. Of these, PEEK, PEI, PPSU, PSU and PES are preferred, with PEEK being the most preferred.

(2-3) Design of flexible joint portion 10 using PEEK As shown in FIGS. 3 to 5, in the flexible joint portion 10 using PEEK, 12 slits are hollowed out to realize bending motion. , The thickness of each slit is 0.4 mm. The distance between the two slits (the gap between the adjacent discs 11) is 0.5 mm. The connection between the two slits is continuously shifted by 45 ° from the one in front of it. A bending motion drive wire passes through each disk 11 through a path determined by four concentric holes h2 having a diameter of 0.5 mm. Further, the gripping motion driving wire (stainless steel wire in the center) passes through the path determined by the hole h1 in the center having a diameter of 1.8 mm.

FIG. 6 is a diagram illustrating the stress distribution in the flexible joint portion.
FIG. 6 shows the FEM analysis result of the stress distribution in the flexible joint portion 10 when a compressive force of 30 N is applied to the top in order to output the gripping force. The compressive force arises from the wire tension for the gripping motion. According to the grip mechanism, when the wire is pulled at 30N, the grip force exceeds 7.5N at the center of the grip 61, which is reasonably sufficient for laparoscopic surgery. Therefore, a compressive force exceeding 30 N is not required.

The analysis was performed by Solidworks 2017. It can be seen that the compressed length was 0.48 mm as determined by linear static dynamics analysis. The stresses at some spots nominally exceeded the compressive strength (105 MPa according to Table 1). From this result, it is found that the flexible joint portion 10 formed by PEEK has sufficient durability to avoid plastic deformation due to extra force due to the gripping motion.

(2-4) Pneumatic drive system FIG. 7 is a schematic diagram of a pneumatic drive system with one degree of freedom. The bending

wires

212 and 213 of the flexible joint portion 10 are connected to the corresponding bending cylinders 52 and 53 (SMC, CJ2XB10-15Z) in the drive unit 50, and the pair of reciprocal cylinders expand and contract to drive the tendon. conduct. The drive wire of the grip portion 61 is also connected to the central grip cylinder 51 (SMC Corporation, CJ2XB16-15RZ).

For each

cylinder

51, 52 and 53, an analog linear encoder (Renishaw, ATOM4T0-100) is used as a position sensor to measure the position of each cylinder rod in position control. Each

cylinder

51, 52 and 53 is operated by a 5-port servo valve (FESTO, MPYE-5-M5-010-B, FESTO) of the control unit 70, and two pressure sensors are attached to the two control ports of the valve. And control the driving force.

A PI controller represented by the equation (1) is implemented for controlling the pneumatic driving force of the

cylinders

51, 52 and 53. The symbol u shown in the formula (1) represents the input voltage of the servo valve (considering the neutral voltage of 5.0 V), F _ref represents the desired cylinder force, and F _meas represents the measured cylinder force calculated by the pressure sensor. represents, K _p and K _i represent the feedback gain parameter of the PI controller shows these values in Table 2. In this system, the control cycle is 0.002 seconds.

FIG. 8 is a diagram illustrating a state in which the flexible joint portion is bent.
FIG. 8 shows the appearance of the forceps unit 100 when the flexible joint portion 10 is bent using the pneumatic drive system. When a force of 20 N is output by the bending cylinder, the bending angle of the flexible joint portion 10 is 67 °, which is the mechanical bending limit of this prototype.

(Section 3) Mechanical Performance of Flexible Joint 10: Experiments and Results This section describes experiments to evaluate the mechanical performance of flexible joint 110 by PEEK, including rigidity and durability.

(3-1) Bending mechanism of the flexible joint portion 10 by PEEK The bending mechanism of the flexible joint portion 10 by PEEK was tested in consideration of the driving force of the grip portion 61. First, the forceps (grip portion 61) were set straight on the flexible joint portion 10 made of almost new PEEK (bending less than 500 times). At this time, the force output from all the cylinders was controlled to 0N. Then, the force of one bending cylinder was gradually increased by 1N to 20N. The maximum force to achieve a maximum bending range of 67 ° was determined to be 20N. After that, the force of the cylinder was gradually reduced to 0N by the same procedure. Bending angles and corresponding cylinder forces were recorded. As shown in FIG. 8, the bending angle is measured from a photograph taken from directly above the flexible joint portion 10. In this case, the driving force of the grip portion 61 is not applied.

FIG. 9 is a diagram showing the relationship between the bending cylinder force and the bending angle of the flexible joint portion.
FIG. 9 shows a change in the bending angle of the flexible joint portion 10 corresponding to the force output from the bending cylinder even when there is no driving force of the grip portion 61.

Next, the same experiment was conducted under the condition that the gripping cylinder retracts the gripping device drive wire, closes the gripping portion 61, and generates a driving force of 30N. In this case, in addition to the tension of the bending wire of the flexible joint portion 10, a compressive load of 30 N due to the tension of the drive wire of the grip portion 61 is applied to the flexible joint portion 10 by PEEK.

FIG. 10 is a diagram showing the relationship between the bending cylinder force and the bending angle of the flexible joint portion.
FIG. 10 shows a change in the bending angle of the flexible joint portion 10 corresponding to the force output from the bending cylinder when the driving force of the grip portion 61 is present.

Comparing the relationship between the bending angle of the flexible joint portion 10 and the bending cylinder force due to the increase in the output of the bending cylinder, FIGS. 9 and 10 show that when the bending cylinder outputs 13N, the grip portion 61 It is shown that the flexible joint portion 10 can bend up to 50 ° regardless of the driving force. Further, FIGS. 9 and 10 show the same tendency in the relationship between the bending angle of the flexible joint portion 10 and the bending cylinder force when the bending angle is less than 50 °.

However, when the driving force of the grip portion 61 exists and the bending angle exceeds 50 °, it becomes difficult to increase the bending angle. As shown in FIG. 9 (without gripping driving force), when the bending cylinder output is 20N, the flexible joint portion 10 can bend 65 °, but when the bending cylinder outputs the same force, the bending angle in FIG. 10 is It was 61 °.

When the output of the bending cylinder decreased, it can be seen that the hysteresis was the same both when the driving force of the grip portion 61 was present and when it was not present. (Although the starting angle was slightly different, the bending angle of the flexible joint 10 in both cases hardly changed until the bending cylinder output decreased to 10 to 11N, and when the bending cylinder output decreased to 6N. , The bending angle of the flexible joint 10 in both cases recovered to 50 °.)

It is considered that the main reason for the hysteresis is the static friction of the operation transmission mechanism, that is, the static friction of the cylinder piston and the wire and its guide path. Taking the cylinder force increasing process of FIG. 9 as an example, the bending angle of the flexible joint portion 10 was 50 ° when the bending cylinder force became 13N, while the bending cylinder force became 6N in the cylinder force decreasing process. When it became, the bending angle of the flexible joint portion 10 recovered to 50 °. An extra force of about 7N prevented the bending wire from returning to its original position.

In addition, FIGS. 9 and 10 show that when the bending angle is less than 50 °, the cylinder output difference between the increasing and decreasing processes for bending the flexible joint 10 to the same angle is 6-7N. There is. The cylinder output difference was 9N at the maximum bending angle. Therefore, the magnitude of static friction is estimated to be 6-9N.

Next, the difference in bending angle according to the cylinder force after 50 ° with and without the driving force of the grip portion 61 will be examined. This phenomenon was considered to be caused by the compression of the flexible joint portion 10 by PEEK. In the absence of the driving force of the grip 61, the slits of the flexible joint 10 due to PEEK on the bending side began to contact each other at a bending angle of about 60 °. On the other hand, when the flexible joint portion 10 was slightly compressed by the driving force of the grip portion 61, the slits on the bending side came into contact with each other at a bending angle of about 50 ° and began to compress. At that time, the bending cylinder had to output an extra compression force, which resulted in a smaller bending angle than in the absence of the driving force of the grip 61. According to this result, the SEP flexible junction related to the combination of the grip portion 61 with the drive controller needs to be designed and mounted so as not to cause this kind of mechanical interference.

(3-2) Compressive Rigidity Test As discussed in the previous section, the gripping cylinder pulls on the central wire to generate a gripping force, which applies additional compressive force to the wrist joint. Since this results in an error in position control, compression of the flexible joint 10 should also be evaluated.

In the experiment, the force of the four bending cylinders was kept at 0N, and the force of the gripping cylinder was gradually increased by 2N to 30N. The length of the flexible joint 10 and the corresponding cylinder force in this case were measured and recorded.

FIG. 11 is a diagram showing the relationship between the grip cylinder output and the length of the flexible joint portion.
From the experimental results, it was found that when the compressive force was increased to 30 N, the flexible joint portion 10 was compressed by 0.62 mm. On the other hand, the results of FEM analysis show compression of the wrist joint of 0.48 mm with the same compressive load (see (2-2) and FIG. 6 above), which results in compression deformation of the flexible joint 10 by PEEK. Can be predicted approximately.

The compression of the flexible joint portion 10 causes a positional error of the tip of the forceps unit 100. However, since the compression length can be measured in real time using the positions of the four bending cylinders, the position error can be compensated by the control system for the entire surgical robot arm.

(3-3) Bending durability test The robot forceps (medical manipulator 1) should have a long life. Here, an experiment was conducted to confirm the following items related to durability performance. That is, the experiment has two items, that is, the durability of the forceps unit 100 according to the development provided with the flexible joint portion 10 against bending fatigue, and whether or not the bending characteristics do not change. The relationship described in (3-1) above was investigated.

In this experiment, the two bending cylinders are manufactured so as to output a driving force according to a sine function reference (amplitude: 20N, frequency: 1Hz) and to repeatedly perform a bending motion of the flexible joint portion 10 with one degree of freedom. Therefore, the flexible joint portion 10 continuously bends to both sides with a bending angle amplitude of about 65 °. During the experiment, bending was temporarily stopped after each repetition of 1000, 2000, 3000, 5000, and 10000 times, and the experiment shown in (3-1) above was performed without the driving force of the grip portion 61.

FIG. 12 is a diagram showing the relationship between the bending cylinder force and the bending angle of the flexible joint portion.
FIG. 12 shows the relationship between the bending cylinder force and the angle of the flexible joint portion 10 after each set of the number of repeated bendings. The results show that the bending characteristics of the flexible joint portion 10 due to PEEK do not change significantly. The variation between the bending angle and the cylinder output curve was considered to be due to the static friction of the operation transmission mechanism that causes the hysteresis in FIGS. 9 and 10. For the curves after 2000 and 10000 bends where maximum variation appears, FIG. 12 shows a cylinder output difference of 4-5N between these two curves for bending the flexible joint 10 to the same angle. It shows that there is, and it is within the range of static friction discussed in (3-1) above (6 to 9N). In addition, no cracks or large plastic deformation occurred in the flexible joint portion 10.

(3-4) Flexural rigidity test In many cases, the surgical assistance robot needs to apply operating forces such as contact and lifting to the object. In these cases, the bending motion of the flexible joint 10 should be rigid enough to transmit the required force. Large additional deformation due to reaction force from the environment is not allowed.

An experiment was conducted to confirm the performance that exerts this power. FIG. 13 is a diagram showing an experimental device. The movement of the tip of the forceps unit 100 in one direction was constrained by a jig fixed to a force sensor (CFS018CA101U, Leptorino Corp.). Initially, the force output from the four bending cylinders was 0N. Next, the output force of the bending cylinder that drives the flexible joint portion 10 and bends in the restraint direction was increased by 2N to 26N. This experiment was performed in the Z-axis direction and the X-axis direction shown in FIG.

14 and 15 show the force applied to the environment as measured by the two-way force sensor and the state of the flexible joint 10. The linearity between the force of the cylinder and the force output from the forceps unit 100 reveals that the flexible joint 10 with PEEK is rigid enough to transmit the working force to the environment. A maximum value of about 1.2N was measured in both directions. If a larger driving force is applied, the forceps unit 100 can output a stronger force, but at the same time, the compression deformation of the flexible joint portion 10 may also increase. In this experiment, when the force of the actuator increased, local deformation occurred at the connection point between the flexible joint portion 10 and the grip portion 61. This deformation was due to a mounting backlash between the flexible joint 10 and the grip 61 as a result of the mechanical design.

(4) Discussion The experiments in Section 3 demonstrated that PEEK's performance regarding durability and rigidity of the flexible joint 10 is basically suitable for robotic surgery. Comparing the performance with the flexible forceps introduced by Miyazaki (Non-Patent Document 4), which has the same outer diameter and bending range as the present study, the length of the flexible joint 10 according to the present study is only 12 mm. The length of the comparison target is 28 mm. This means that the forceps unit 100 according to the present study has sufficient skill to function well in a narrow space. Regarding the performance of the output force, the forceps unit 100 according to this study is strong with respect to the bending force (1.2N to 1.0N) and the gripping force (7.5N to 0.6N).

However, some improvements are still needed to improve performance. First, the friction between the drive wire and other components should be reduced. This friction hinders the reproducibility of the same bending angle when the cylinders output the same force. The effects of friction need to be dynamically compensated for in force control. For position control, a position sensor can be used to measure the actual bending angle and this information can be applied to the control loop.

Secondly, the compressive rigidity of the flexible joint portion 10 should be strengthened to maintain the maximum bendable angle and reduce the positional error of the forceps unit 100 in the position control.

Third, the maximum bending force should be strengthened without major deformation. The experimental results shown in (3-4) above indicate that the maximum bending force without large deformation was 1.2N. This magnitude of force is sufficient for surgical operations such as cutting, excision, detachment, and suturing, but insufficient for lifting and holding large organs.

(5) Summary of Study In the above, a robot forceps (medical manipulator 1) equipped with a forceps unit 100 having a flexible joint portion 10 made of PEEK plastic, which is a kind of super engineering plastic material, was examined. The bending and gripping movements of the forceps unit 100 were realized by wire actuation driven by a pneumatic cylinder located away from the tip. The results of the performance evaluation experiment clarified the mechanical properties of the flexible joint portion 10. The relationship between bending motion output and bending angle helped to build a simple dynamic model of the position controller. However, this relationship changed after bending over 50 ° due to the joint compression due to the driving force of the 30N grip 61, where the flexible joint 10 was compressed by 0.62 mm by PEEK. Regarding durability, the bending characteristics did not change significantly even after the wrist joint joint was repeatedly bent 10,000 times without the driving force of the grip portion 61. With respect to flexural rigidity, the PEEK flexible joint 10 can withstand an external force of more than 1.2 N at the center of the grip 61 and maintain its shape when in contact with the environment. In conclusion, the robotic forceps (medical manipulator 1) with the flexible joint 10 made by PEEK show excellent performance and have potential for use in robotic surgery.

(Comparative example)
FIG. 16 is a diagram showing the results of static load analysis of the flexible joint portion according to the comparative example.
The flexible joint portion according to the comparative example shown in FIG. 16 is made of stainless steel (SUS204).
FIG. 17 is a diagram showing the results of static load analysis of the flexible joint portion (manufactured by PEEK) according to the present embodiment.
In each of the examples, the static load analysis result at the time of bending when the compressive force 30N is applied to the flexible joint portion is shown.

From this analysis result, it is possible to significantly reduce the stress level acting as the flexible joint portion 10 by using PEEK, which has higher flexibility and can be designed to be thicker than SUS304. Therefore, as the flexible joint portion 10, it is possible to increase the functionality and durability against flexion by using PEEK rather than by using SU304.

By constructing the flexible joint portion 10 with the resin material examined as described above, it becomes possible to provide a medical manipulator 1 having sufficient bending force, treatment force and durability.

FIG. 18 is a block diagram for explaining the force sense estimation mechanism of the medical robot. The medical robot 500 includes an actuator 55 (specifically, a gripping cylinder 51, a bending cylinder 52, 53) for operating the forceps unit 100, a drive unit 50 including a linear encoder 56 attached to each actuator 55, and a pneumatic sense. It includes an estimation mechanism 561, a pneumatic control unit 562, a pneumatic measurement unit 571, and a servo valve 572. The pneumatic control unit 562 outputs a control signal for controlling the servo valve 572, and the servo valve 572 changes the air pressure supplied to each actuator 55 by this control signal, and the forceps unit 100 associated with each actuator 55. (Treatment portion 60 such as grip portion 61, flexible joint portion 10) is displaced. The linear encoder 56 included in the drive unit 50 measures the position of the operating portion of the forceps unit 100 associated with the actuator 55 by measuring the position of the piston of the actuator 55. The air pressure measuring unit 571 measures the air pressure supplied from the servo valve 572 to each actuator 55.

The air pressure sensation estimation mechanism 561 obtains the force applied in the operating direction of the actuator 55 based on the information on the position of each part of the forceps unit 100 from each linear encoder 56 and the information on the air pressure from the air pressure measuring unit 571. Based on the force, the external force applied to the moving portion of the forceps unit 100 is estimated. Specifically, the air pressure sensation estimation mechanism 561 can estimate the bending external force of the flexible joint portion 10 of the forceps unit 100 and the gripping force of the grip portion 61.

As described above, in the forceps unit 100 included in the medical manipulator 1 of the medical robot 500 according to the present embodiment, the linearity between the operating force output by the actuator 55 and the displacement of the moving portion of the forceps unit 100 is high. There is little change in this linearity over time. Therefore, the air pressure sensation estimation mechanism 561 can more accurately estimate the external force applied to the moving portion of the forceps unit 100.

Although the present embodiment has been described above, the present invention is not limited to these examples. For example, in the above embodiment, the example of the forceps having the grip portion 61 as the treatment portion 60 is shown, but the treatment portion 60 other than the forceps may be used. Specific examples include a cutting tool such as an ultrasonic scalpel and a laser scalpel. Further, the gist of the present invention also includes those to which a person skilled in the art appropriately adds, deletes, and changes the design of each of the above-described embodiments, and those in which the features of the configuration examples of each embodiment are appropriately combined. Is included in the scope of the present invention as long as it is provided. For example, the medical treatment tool unit (forceps unit 100) may have a spring portion or a flexible tube portion inserted in the center of a plurality of discs. As a result, the rigidity of the spring portion or the flexible tube portion is added to the flexible joint portion, and the spine structure (core material) for increasing the compression rigidity of the flexible joint portion 10 is formed, so that the treatment force can be easily obtained. PEEK is suitable as the material for the flexible tube portion.

1 ... Medical manipulator 10 ... Flexible joint 11 ... Disc body 12 ... Connecting part 20 ... Shaft 30 ... Actuator adapter 50 ... Drive unit 51 ...

Grip cylinder

52, 53 ... Bending cylinder 55 ... Actuator 56 ... Linear encoder 60 ... Treatment unit 61 ... Grip portion 62 ... Slide cam 70 ... Control unit 100 ... Forceps unit (medical treatment tool unit)
211,212,213 ... Wire 500 ... Medical robot 561 ... Pneumatic sense estimation mechanism 562 ... Pneumatic control unit 571 ... Pneumatic measurement unit 572 ... Servo valve ST ... Structure h1, h2 ... Hole

Claims

A medical treatment tool unit having a treatment unit driven by a drive unit.
A shaft having a transmission mechanism for transmitting a driving force from the driving unit to the treatment unit,
A flexible joint portion provided between the shaft and the treatment portion,
Equipped with
The flexible joint portion is
Discs arranged in a plurality of stages at predetermined intervals in the first direction along the axis of the shaft, and
A connecting portion that connects between adjacent discs and extends in a second direction orthogonal to the first direction, and the extending directions of the adjacent connecting portions that are adjacent to each other in the first direction are different from each other. With a connecting part,
The flexible joint portion was formed of a resin material having a bending deformation region (bending strength / flexural modulus) of 3.0% or more, a compressive strength of 50 MPa or more, and a bending elastic modulus of 10 GPa or less. A characteristic medical treatment tool unit.
The medical treatment tool unit according to claim 1, wherein the resin material contains at least one resin selected from the group consisting of PEEK, PEI, PPSU, PSU, PES, and POM-C.
The set of one disk body and one connecting portion connected to the disk body is regarded as a one-stage structure, and the extending directions of the connecting portions in the adjacent structures differ from each other by 45 degrees. The medical treatment tool unit according to claim 1 or 2.
The medical treatment tool unit according to claim 3, wherein the number of stages of the structure in the flexible joint portion is 9 or more and 12 or less.
The treatment portion has a grip portion, and the extending direction of the connecting portion is not located in a direction along the occlusal surface of the grip portion arranged on the tip end side of the flexible joint portion, claims 1 to 4. The medical treatment tool unit according to any one of the above.
The medical treatment tool unit according to any one of claims 1 to 5, which has a spring portion or a flexible tube portion inserted in the center of the plurality of discs.
A medical manipulator including the medical treatment tool unit according to any one of claims 1 to 6 and a drive unit for driving the treatment tool of the medical treatment tool unit.
The medical manipulator according to claim 7, wherein the drive unit drives the treatment tool by air pressure.
The medical robot provided with the medical manipulator according to claim 8, further comprising an air pressure sensation estimation mechanism that estimates an external force applied to the treatment tool based on the measurement of the air pressure.