KR20150030900A - Structure and design method of control arm - Google Patents

Abstract

A control arm structure and a design method thereof are disclosed. The control arm structure includes a motor pulley connected to a motor to be operated; a capstan disk positioned adjacent to the motor pulley; a wire coupled to the motor pulley and the capstan disk, respectively, and mechanically connecting the motor pulley and the capstan disk; an arm unit coupled to the capstan disk and extended a predetermined distance from the center of the capstan disk; and a gimbal coupled to a bottom end of the arm unit. The control arm structure is designed to satisfy a mathematical formula (1) of Tp > Tm to prevent the wire slip, and prevents the generation of slip in the wire in a process of operating the control arm structure which connects the motor pulley and the capstan disk through a pulley wire.

Description

Control arm structure and control arm design method

The present invention relates to a control arm structure and a control arm design method.

Medically, surgery refers to the repair of a skin, mucous membrane, or other tissue that is cut, torn or manipulated using a medical device. Particularly, due to problems such as hemorrhage, side effects, patient's pain, scarring, etc., the incision is made by cutting the skin of the surgical site and opening, treating, And is attracting attention as an alternative.

The surgical robot may be divided into a master unit for generating and transmitting a signal required by a physician's operation and a slave unit for receiving signals from the operation unit and applying operations necessary for surgery to the patient. And the slave unit may be divided into respective parts of one surgical robot, or they may be separately provided as separate units, that is, the operation unit may be a master robot and the driving unit may be divided into slave robots, respectively.

In the master part of the surgical robot, a control arm for physician's operation is installed. In the case of robot surgery, the master does not directly manipulate the instrument necessary for the surgery, but moves the control arm Allow the instrument to perform the operations required for surgery.

In a surgical robot, when the doctor holds the control arm directly with his or her fingers and performs operation for a long time, the weight of the control arm may have to be directly handled by the doctor.

In addition, a physician can sense the movement of the control arm by gripping the control arm and signaling the motion, so that it can be used as an input signal necessary for operation of the surgical robot.

To this end, as shown in FIG. 1, the control arm may have a structure in which a capstan disk is installed at a hinge portion where an arm is coupled to the robot body, and the capstan disk is connected to a motor pulley by a wire.

In order to reduce the weight of the control arm and to implement gravity compensation, a driving force may be applied to move the arm upward by operating the motor. In order to realize force feedback by sensing the operation of the control arm, The rotation of the motor pulley along with the motion can be signaled through the encoder.

In the conventional control arm structure, a motor (pulley) having a high torque value is connected to a capstan disk via a wire to realize the above-described gravity compensation and force feedback, As shown in FIG.

At this time, if the torque of the motor is excessively large, the wire wound around the motor pulley can not withstand the torque (torque) output from the motor, and a slip may occur.

That is, in the structure in which the motor for driving the control arm is coupled with the capstan disk and the pulley through the wire, the wire slips between the motor and the capstan disk according to the torque value of the motor (if too large) There is a possibility of occurrence.

The above-described background technology is technical information that the inventor holds for the derivation of the present invention or acquired in the process of deriving the present invention, and can not necessarily be a known technology disclosed to the general public prior to the filing of the present invention.

On the other hand, US Patent Publication No. US2012 / 0330287 discloses a surgical instrument including a driving portion-pulley wire-capstan structure. Korean Patent Laid-Open Publication No. 1998-043123 discloses a surgical stapling method for preventing slippage between a pulley and a wire. And the like.

Patent Document 1: U.S. Published Patent Application No. US2012 / 0330287 Patent Document 2: Korean Patent Publication No. 1998-043123

The present invention provides a control arm structure and a control arm design method that can prevent slippage of a wire in a control arm structure in which a motor pulley and a capstan disk are pulley-connected by a wire.

Other objects of the present invention will become readily apparent from the following description.

According to an aspect of the present invention, there is provided a motor drive apparatus including a motor pulley connected to a motor, a capstan disk positioned adjacent to the motor pulley, and a motor pulley coupled to the motor pulley and the capstan disk, An arm portion coupled to the capstan disk and extending a predetermined distance from the center of the capstan disk and a gimbal coupled to an end of the arm portion; A control arm structure is provided which is designed to satisfy the following expression (1) in order to prevent slippage of the wire.

Tp > Tm (1)

Here, Tp is a torque acting on the motor pulley by a user operation on the gimbal, and Tm is a torque acting on the motor pulley due to the operation of the motor.

The motor output, the diameter of the motor pulley, the diameter of the capstan disk, the friction coefficient of the wire, the elastic limit of the wire, the number of times the wire is wound on the motor pulley, the extension distance of the arm portion, The design variables such as the weight of the gimbals and the like can be adjusted.

Tm can be derived from equation (2) by measuring the current applied to the motor when the motor is operated.

Tm = Tn x Im / In (2)

Where Tn is the rated torque of the motor, In is the nominal current of the motor, and Im is the measured value of the current applied to the motor.

Tp can be derived from equation (3).

Tp = Ft x Rp (3)

Here, Ft is the elastic limit of the wire, and Rp is the radius of the motor pulley.

The wire is fixed to the capstan disk by a tensioner so that the wire is pulled by the force of Ft by a user operation on the gimbal while the tightening torque of the tensioner can be derived from equation (4).

Tt = Ft x r (4)

Here, Tt is the tightening torque of the tensioner, and r is the radius of the tensioner.

According to another aspect of the present invention, there is provided a motor control apparatus including a motor pulley connected to a motor, a capstan disk positioned adjacent to the motor pulley, a wire pulley-connected to the motor pulley and the capstan disk, CLAIMS 1. A method of designing a control arm comprising an arm extending a predetermined distance from a center of a capstan disk and a gimbal coupled to an end of the arm, the method comprising: (a) deriving a torque acting on the motor pulley by user manipulation of the gimbal (B) calculating a torque acting on the motor pulley by operation of the motor; and (c) calculating the output of the motor, the diameter of the motor pulley, the diameter of the capstan disk, Adjusting the design parameters such as the friction coefficient, the elastic limit of the wire, the number of times the wire is wound on the motor pulley, the extension distance of the arm portion, and the weight of the arm portion and the gimbals This should control arm design method is provided.

Other aspects, features, and advantages will become apparent from the following drawings, claims, and detailed description of the invention.

According to the embodiment of the present invention, it is possible to prevent a slip from occurring in the wire during operation of the control arm structure in which the motor pulley and the capstan disk are connected by the pulley wire.

1 is a schematic diagram showing a control arm structure according to an embodiment of the present invention;
2 is a front view showing a control arm structure according to an embodiment of the present invention;
3 is a bottom view of a control arm structure according to an embodiment of the present invention.
4 is a flowchart illustrating a method of designing a control arm according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Referring to the accompanying drawings, the same or corresponding components are denoted by the same reference numerals, .

2 is a front view illustrating a control arm structure according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view illustrating a control structure according to an embodiment of the present invention. Referring to FIG. 1, FIG. 4 is a flowchart illustrating a method of designing a control arm according to an embodiment of the present invention. Referring to FIG. 1 to 3, a motor 10, a motor pulley 12, a capstan disk 20, a tensioner 22, a wire 30, an arm portion 40, and a gimbal 42 are shown.

The present embodiment is an improvement of the structure of a control arm for operating a mechanical device such as a master interface arm of a surgical robot. In particular, the present invention prevents a slip of a wire connecting a capstan disk and a motor pulley, that is, .

The control arm structure according to the present embodiment is a technique of deriving a formula relating to a winding torque (torque) of a wire connecting a motor pulley and a capstan disk, and then adjusting the winding torque to such an extent that the slip does not occur in the elastic limit of the wire Is applied.

Motor drive of the capstan disk applied to the control arm of the surgical robot can be configured as shown in Fig. That is, for power transmission between the motor pulley and the capstan disk, a wire can be used as shown in Fig.

Since the backlash is close to zero as compared with the gear system in which the impact is transmitted when the gear is moved, the power transmission system through the wire can be used as a power transmission system for the control arm (control arm) of the surgical robot, have.

In order to relieve the physician's arm fatigue during the operation using the robot, the control arm needs to be applied with a gravity compensating technique for 'not feeling weight'. In addition, a virtual wall is set, Haptic technique or force feedback technique that informs the physician using reverse torque of the motor needs to be implemented.

To this end, the control arm structure according to the present embodiment may include a motor pulley 12, a capstan disk 20, a wire 30, an arm portion 40, and a gimbals 42.

The motor pulley 12 is a pulley connected to the rotating shaft of the motor 10 and rotated according to the operation of the motor 10. [ The motor pulley 12 according to the present embodiment has a predetermined diameter Dp and the wire 30 described below can be wound several times (n) on the motor pulley 12. [ For example, the diameter of the motor pulley 12 may be 11.44 mm, and the wire 30 may be wound seven times on the motor pulley 12.

The capstan disk 20 is a disk located adjacent to the motor pulley 12 and installed at a hinge portion where the arm portion 40 is connected to the robot body. As the capstan disk 20 rotates, the arm portion 40 (and the gimbals 42) connected thereto is rotated. The capstan disk 20 according to the present embodiment has a predetermined diameter Dc and the wire 30 described later can be fixed by the tensioner 22 at a predetermined point of the capstan disk 20. [

The wires 30 are pulley-connected to the motor pulley 12 and the capstan disk 20 so as to connect the motor pulley 12 and the capstan disk 20. The wire pulley 12 includes a motor pulley 12 and a capstan disk 20, Is mechanically interlocked by the wire (30). The wire 30 according to the present embodiment is wound around the motor pulley 12 with a predetermined friction coefficient mu.

Also, the wire 30 according to the present embodiment has a predetermined elastic limit Ft according to the material thereof.

Since various components constituting the surgical robot are complex and the driving force must be transmitted in various directions, the wire 30 of tungsten material can be generally used.

A maximum tensile force, that is, a tensile force corresponding to an elastic limit can be applied within a range in which the wire 30 wound around the motor pulley 12 is not broken, and such an elastic limit value is obtained by performing a tensile test on the wire 30 Can be confirmed.

That is, a strain-strain curve can be derived from the tensile test of the wire 30, and the maximum value of the straight line section can be confirmed as an elastic limit value.

For example, when using tungsten wire 30, the elastic limit may be 5.4 kgf. Further, in the control arm structure according to the present embodiment, a value obtained by multiplying the elastic limit by the safety factor in consideration of the safety factor may be used as the elastic limit value at design time.

For example, when the safety factor is set to 80%, the design elastic limit of the tungsten wire 30 may be 4.32 (= 5.4 x 80%) kgf.

The arm portion 40 is an arm-shaped structure extending from the capstan disk 20 and may be formed of a single member or a plurality of members may be combined to constitute the arm portion 40 according to the present embodiment . For example, a plurality of members may be combined with a selective compliance assembly robot arm (SCARA) structure to constitute the arm portion 40 according to the present embodiment, so that the gimbals 42 described later can be moved to an arbitrary position in the three- have. The arm portion 40 according to the present embodiment may extend a predetermined distance Da from the center of the capstan disk 20 and may have a predetermined weight ma.

The gimbal 42 is a component corresponding to a kind of 'handle' which is coupled to the end of the arm 40 and is held by a user (doctor). The gimbal 42 is supported by the arm 40 And can be moved to an arbitrary position on the three-dimensional space.

In order to prevent the physician from feeling the weight of the gimbal 42 when the doctor grips the gimbal 42, the control arm according to the present embodiment can be applied to the gravity compensation technique as described above. Also, haptic and / or force feedback techniques may be implemented in the movement of the gimbals 42, and the 'motor pulley 12-capstan disk 20' structure may be applied to the control arm according to this embodiment .

As described above, the control arm structure according to the present embodiment can be applied to the structure of the 'motor pulley 12-capstan disk 20' connected to each other by the wire 30, And a control arm structure is designed so that slip does not occur.

That is, by designing the control arm so as to satisfy the following equation (1), it is possible to prevent the wire 30 from slipping.

Tp > Tm (1)

Where Tp is a torque acting on the motor pulley 12 by a user's operation on the gimbal 42 and Tm is a torque acting on the motor pulley 12 by the operation of the motor 10. [ That is, as the user operates the gimbals 42, the torque value applied to the motor pulley 12 becomes larger than the torque value applied to the motor pulley 12 as the motor 10 operates (for gravity compensation, etc.) It is possible to prevent the wire 30 from slipping.

In order to design the control arm by adjusting the torque value as described above, the design parameters affecting the torque value Tp acting on the motor pulley 12 as the user operates the gimbals 42 are derived, Variables are adjusted.

These design parameters include the diameter Dp of the motor pulley 12, the diameter Dc of the capstan disk 20, the friction coefficient mu of the wire 30, the elastic limit Ft of the wire 30, The number n of turns of the motor 30 on the motor pulley 12, the extension distance Da of the arm 40 and the weights ma and mg of the arm 40 and the gimbals 42 .

On the other hand, the torque value Tm acting on the motor pulley 12 as the motor 10 operates is related to the output value of the motor 10, which can be derived from the specification of the selected motor 10 have.

That is, Tm can be derived from the following equation (2) by measuring the current applied to the motor 10 when the motor 10 is operated.

Tm = Tn x Im / In (2)

Where Tn is the nominal torque of the motor 10 and In is the nominal current of the motor 10. [ That is, the rated torque Tn value and the rated current In value are derived from the specification information of the selected motor 10, and the measured current value Im is input to calculate the Tm value from the equation (2) have.

For example, a control arm is manufactured by selecting a motor 10 having a rated torque value of 0.420 Nm and a rated current value of 4.58 A. When a maximum load is applied to the motor 10 (when the arm portion 40 is a capstan disk 20), the current value applied to the motor 10 is measured to be 2.29 A. When the gimbal 42 is operated,

Tm = 0.42 x 2.29 / 4.58 = 0.21 Nm

As shown in FIG.

In this case, by setting the current to be applied to the motor 10 to flow only 2.29 A, the torque value acting on the motor 10 can be made not to exceed 0.21 (Nm) at the maximum.

It can be seen that the torque value obtained experimentally in the actual operating state of the control arm based on the selected motor 10 is calculated to be 0.21 Nm which is about 50% of the rated torque (0.42 Nm) of the selected motor 10.

On the other hand, the torque value Tp acting on the motor pulley 12 as the user operates the gimbals 42 is related to the design specifications of the control arm and can be derived from the following equation (3).

Tp = Ft x Rp (3)

Where Ft is the elastic limit value of the wire 30 and Rp is the radius of the motor pulley 12 (= Dp / 2).

That is, Tp corresponds to the torque generated in the motor pulley 12 when the wire 30 is pulled at the Ft value. When calculation is made for the above-described case,

Tp = 4.32 (kgf) x 5.72 (mm) = 24.71 (kgfmm) = 0.246 (Nm)

The torque value Tp generated when the wire 30 is pulled by the force Ft is calculated as follows.

Tp: Tm = 0.246 (Nm): 0.21 (Nm)

As a result, since the torque value Tp acting on the motor pulley 12 is 0.246 Nm greater than the torque value Tm from the motor 10, which is 0.21 Nm, the wire 30 It is possible to prevent slippage from occurring in the case of the present invention.

The above result is based on the premise that the wire 30 is pulled by the tensile force of Ft due to the user's operation on the gimbal 42. To this end, a separate tensioner 22 is attached to the wire 30 30 must be secured to the capstan disk 20.

The tightening torque to be applied to the tensioner 22 so that the tensile force Ft is retained on the wire 30 can be obtained from the following equation (4) Can be derived.

Tt = Ft x r (4)

Here, Tt is the tightening torque of the tensioner 22, and r is the radius of the tensioner 22.

For example, when the tensioner 22 using an outer diameter 12.7 wave is used to fix the wire 30, the tightening torque of the tensioner 22 is,

Tt = 4.32 x 6.35 = 27.432 kgfmm

Can be calculated as follows. That is, the tensile force Ft can be maintained on the wire 30 by tightening the tensioner 22 with a tightening torque of 27.432 kgfmm.

In conclusion, in order to prevent the slip of the wire 30 between the motor pulley 12 and the capstan disk 20 in the control arm structure of the surgical robot using the capstan disk 20, The torque value Tp acting on the motor pulley 12 is calculated (S100) and the torque value Tm acting on the motor pulley 12 is derived as the motor 10 is operated S200).

The steps of calculating the Tp value and the Tm value may be performed sequentially or in parallel, and it is not necessary that one step precedes or follows another step.

Next, the control arm may be designed by appropriately adjusting the mechanical design parameter value so that the Tp value is larger than the Tm value (S300).

The tensioner 22 may be assembled by applying the calculated torque Tt to the tensioner 22 so as to maintain the tension of the wire 30 constant.

On the other hand, the total force Fw applied to the motor pulley 12 by the wire 30 wound around the motor pulley 12 can be calculated by the following equation (5).

Fw = 占 x Ft 占 n (5)

Here, μ is the inherent friction coefficient (constant) of the wire 30 to be used, and n is the number of times the wire 30 is wound on the motor pulley 12.

The number of windings of the wire 30 determines the width of the motor pulley 12 that can be mounted within the width of the capstan disk 20, The winding pitch and the number of turns can be determined.

In the case of the above example, Fw can be calculated as follows.

Fw = mu x 4.32 x 7 = 30.24 mu kgf

That is, the force finally applied to the motor pulley 12 according to the number of times the wire 30 is wound on the motor pulley 12 can be confirmed.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

10: motor 12: motor pulley
20: capstan disk 22: tensioner
30: wire 40:
42: Gimbal

Claims (6)

A motor pulley operatively connected to the motor;
A capstan disk positioned adjacent to the motor pulley;
A wire pulley coupled to the motor pulley and the capstan disk, respectively, for mechanically connecting the motor pulley and the capstan disk;
An arm portion coupled to the capstan disk and extending a predetermined distance from a center of the capstan disk;
And a gimbal coupled to an end of the arm portion,
Wherein the control arm structure is designed to satisfy the following equation (1) to prevent slippage of the wire.
Tp > Tm (1)
Here, Tp is a torque acting on the motor pulley by a user operation on the gimbal, and Tm is a torque acting on the motor pulley by operation of the motor.
The method according to claim 1,
Wherein the output of the motor, the diameter of the motor pulley, the diameter of the capstan disk, the friction coefficient of the wire, the elastic limit of the wire, the number of times the wire is wound on the motor pulley, An extension distance of the arm portion, and a weight of the arm portion and the gimbals is adjusted.
The method according to claim 1,
Wherein Tm is derived from the following equation (2) by measuring a current applied to the motor when the motor is operated.
Tm = Tn x Im / In (2)
Here, Tn is a nominal torque of the motor, In is a nominal current of the motor, and Im is a measured value of a current applied to the motor.
The method according to claim 1,
Wherein Tp is derived from the following equation (3).
Tp = Ft x Rp (3)
Here, Ft is an elastic limit of the wire, and Rp is a radius of the motor pulley.
5. The method of claim 4,
The wire is fixed to the capstan disk by a tensioner so that the wire is pulled by the force of the Ft by a user operation on the gimbal, wherein the tightening torque of the tensioner is expressed by the following equation (4) Wherein the control arm structure is formed of a metal plate.
Tt = Ft xr (4)
Here, Tt is a tightening torque of the tensioner, and r is a radius of the tensioner.
A capstan disk disposed adjacent to the motor pulley; a wire pulley-connected to the motor pulley and the capstan disk; a wire coupled to the capstan disk; 1. A method of designing a control arm including an arm extending a predetermined distance and a gimbal coupled to an end of the arm,
(a) deriving a torque acting on the motor pulley by a user operation on the gimbal;
(b) deriving a torque acting on the motor pulley by operation of the motor; And
(c) the output of the motor, the diameter of the motor pulley, the diameter of the capstan disk, the coefficient of friction of the wire, the elastic limit of the wire, the wire wound on the motor pulley Adjusting the at least one design parameter selected from the group consisting of a number of times, an extension distance of the arm portion, and a weight of the arm portion and the gimbals.
Tp > Tm (1)
Here, Tp is a torque acting on the motor pulley by a user operation on the gimbal, and Tm is a torque acting on the motor pulley by operation of the motor.

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