KR101358669B1 - Apparatus for measuring force or torque of multi-DOFs gripper device on a slider of robot arms and method of the same - Google Patents

Abstract

The present invention relates to an apparatus and a method for measuring the contact force (force or torque) between a gripper and a contact object, the present invention does not directly attach a sensor to a gripper inserted into the body, but is transmitted to a gripper sensed by an externally installed sensor An apparatus and method for measuring a force or torque at a slider of a robot arm of a multi-degree of freedom gripper device that enables the contact force to be measured through the torque being provided.

Description

Apparatus for measuring force or torque of multi-DOFs gripper device on a slider of robot arms and method of the same}

The present invention relates to an apparatus and a method for measuring the contact force (force or torque) between a gripper and a contact object, and more particularly, a sensor is directly connected to the gripper to measure the force or torque of the multiple degree of freedom gripper. An apparatus and a method for indirectly measuring contact force by attaching a sensor to a slider of a robot arm without attaching the same.

There are many changes in medical technology as the technology develops, and surgery is one of various medical technologies. Surgery is a medical act of incision and stitching of the skin. All of the existing surgeries have pain after recovery and surgical stimulation after recovery, and it takes a long time to return to daily life after surgery. Recently, minimally invasive surgery has been widely used to minimize post-operative pain by minimizing the incision site and to reduce the time to return to daily life after surgery.

Minimally invasive surgery involves the insertion of an observation device called an endoscope and a small surgical device into the body and looking at the internal organs displayed on the monitor. However, this surgical method is performed in a very narrow area, so the operator has to operate the surgical device with the correct position and the correct force and speed, which puts a lot of pressure on the operator. Surgical methods are widely used.

A robot for minimally invasive surgery is commonly referred to as a minimally invasive surgical robot, which inserts a robot arm with surgical instruments attached to it and a robot arm with an endoscope camera attached to it, and the operator sits at the master console and displays a 3D image. Looking at the remote control of the surgical instruments inserted into the patient's body is to perform the operation. In order for the operation to be successful, it is necessary to accurately check the surrounding conditions including the surgical target part.However, the surgical robot currently on the market can visually check the surgical part situation only by video feedback through a laparoscopic CCD camera. It is very difficult to distinguish visually invisible areas from hidden tissues such as blood vessels, nerves, and cancer cells, so that the interaction force between the slave robot and the internal organs of the human body is measured and the doctor can accurately contact the force (force or torque, It's very important to give feedback so that you don't damage unnecessary parts.

As such, the technique used to measure the interaction force between the gripper of the slave robot arm and the surrounding environment is measured near the end of the surgical tool or on a slider attached to the trocar or robot arm as shown in FIG. The method to use is used. The measurement at the part adjacent to the end of the surgical tool is to attach the sensor directly to the contact surface inside the gripper, and the measurement at the slider attached to the robot arm is to install the sensor at a specific position outside the body away from the contact surface. To take measurements.

Patent Documents 1 to 3 as such a force measurement technology. Patent document 1 measures a strain strain at the end of a surgical instrument using an optical sensor called a diffraction grating sensor (FBG, Fiber Bragg Grating), and the FBG reflects and effectively changes the wavelength of light that changes in response to strain strain. It affects the index of refraction and the grating cycle to detect the reflected wavelength and to detect the deformation. This is a direct measurement of the interaction force with the environment through the deformation of the optical sensor at the end of the surgical instrument.

Patent document 2 attaches a modular force sensor composed of a strain gauge to a distal tube link portion of an end portion of a surgical tool. Is to measure the contact force directly.

Patent document 3 uses a strain gauge or the like to directly measure the contact force acting at the end of a surgical tool, and has a six-axis force / coaxial force on a joint before the first joint of a slave arm having a parallel structure and operated by a master device. By attaching a torque sensor, it measures the force of interaction between an object outside the patient's body and the slave arm and uses it to classify the force generated outside and inside the patient's body.

Non-patent documents 1 and 2 are techniques for force feedback in a surgical robot. Non-Patent Literature 1 is a technique of measuring a contact force directly at the end by attaching a resistive sensor to the gripper end, and Non-Patent Literature 2 is attaching a strain gauge sensor to the end of the surgical gripper and attaching a strain gauge sensor directly to the end. It is a technique to measure.

These conventional techniques have the following problems as a method of measuring the force by attaching a sensor to the surface of the surgical tool gripper. That is, a high current flows to the end of the surgical tool for ablation in the surgical procedure. The high current may damage the sensor, and the sensor may be damaged even during sterilization by high temperature and high pressure. In addition, the surgical tool is a consumable that has to be discarded when a certain number of times or more is used, thereby causing a problem of unnecessary waste of manufacturing cost and resources by installing a sensor on the surgical tool that is discarded.

1. US Patent Publication No. 2010/0250000 (2010.09.30) 2. United States Patent No. 07552920 (July 13, 2010) 3. United States Patent Application Publication No. 2009/0248038 (2009.10.01)

1. G. Tholey, et, al., "A Modular, Automated Laparoscopic Grasper with Three-Dimensional Force Measurement Capability," IEEE Int. Conf. on Robotics and Automation, Roma, Italy, 10-14, Apr., 2007. 2. G. S. Fischer, et, al., "" Ischemia and Force Sensing Surgical Instruments for Augmenting Available Surgeon Information, "Int. Conf. on Biomedical Robotics and Biomechatronics, Feb., 2006

The present invention has been developed to solve the problems of the prior art as described above, to overcome the limitations of the method of measuring the force at the end of the surgical instrument to attach the sensor to the slider of the robot arm to measure the force An object is to provide a device for measuring force or torque at the slider of a robot arm of a multi-degree of freedom gripper device.

That is, the present invention is not affected by high current, does not need to be sterilized by high temperature and high pressure, and it is possible to measure the contact force of the gripper on the outside of the treatment site that can be used repeatedly, and thus the power to drive the gripper Apparatus and method for measuring force or torque in a slider of a robot arm of a multiple degree of freedom gripper device by attaching a sensor to a transmitting slider to detect the contact force of the gripper by measuring the force or torque applied when the slider is driven. To provide.

The present invention for solving the above problems includes a slave robot arm with a gripper attached to the end and a slave robot arm with an endoscope camera attached, the gripper is in contact with the organs by the drive of the drive body driven by the movement of the slider A device for measuring contact force that transmits a force or torque to a doctor, comprising: installing a sensor for sensing a force or pressure between a slider and a driving body that is pushed or pulled by a slider to operate a gripper, And a contact force calculation program for calculating a contact force for the gripper to contact the organ from the pressure.

In addition, the present invention can be carried out by variously modifying the drive body driven by the operation of the slider, but preferably constituted by a wire, the gripper is operated by the tension or relaxation of the wire by the movement of the slider, thus operating The force or pressure between the slider and the wire is sensed by the sensor so that the gripper's contact force can be detected.

The sensor constituting the present invention can be used in a variety of selection, but preferably a force sensor or a pressure sensor.

In addition, the calculation program of the present invention may be implemented in various modifications, but in a preferred embodiment, the contact force (τ _e ) at which the gripper is in contact with the organ is expressed by the following equation.

으로부터 구해진다.

Obtained from

The contact force calculation program may include friction compensation means, and when the wire is modeled as a nonlinear spring in the wire driving method, the contact force f _g is given by the following dynamic equation.

으로 표현된다.

.

Another aspect of the present invention is a contact force measuring method using a force or torque measuring device in the slider of the robot arm of the gripper device configured as described above, the sensor is applied to the force or pressure acting between the drive and the moving body by the slider movement. Sensing; And calculating the contact force of the gripper by calculating the detected force or pressure information in the contact force calculation program.

The present invention can be generated when the sensor is installed in the gripper by estimating and calculating the contact force of the gripper by installing the sensor on the gripper driving means of the robot arm outside the body without installing the sensor on the gripper inserted into the body. You can solve the problem. That is, since the sensors, which are means for detecting the contact force of the gripper, are installed on the outside of the body, it is possible to prevent the sensor from being damaged by the high current applied to the surgical tool during the surgery, and the sensor is separated from the surgical tool. Not only can the sensor be protected by exposure to high temperature and high pressure, but it can also be used to dispose of surgical instruments, thereby preventing unnecessary waste of manufacturing costs and resources.

1 is a block diagram of a force or torque measuring device in the slider of the robot arm of the gripper device according to the present invention.
2 is a block diagram of a robotic arm control system for surgery.
3 is a signal flow diagram in a surgical robot arm control system.
4 is a perspective view of an example of a robot arm with a gripper actuated by a slider;
5 is a configuration diagram of a gripper driving means of a wire driving method.
6 is a block diagram for a slave controller using a reaction torque observer.
7 is a block diagram of a reaction force observer in the controller shown in FIG.
8 is a view showing a portion for measuring the interaction force between the gripper and the surrounding environment of a conventional slave robot arm.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. In the drawings of the present invention, the sizes and dimensions of the structures are enlarged or reduced from the actual size in order to clarify the present invention, and the known structures are omitted so as to reveal the characteristic features, and the present invention is not limited to the drawings . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the subject matter of the present invention.

The present invention enables to measure the contact force of the gripper to operate inside the body from the outside of the body, the sensor (S) is installed in the drive means 10 for operating the gripper 1 and the gripper from the information detected from the sensor The contact force of (1) can be detected.

The driving means 10 may be implemented by various modifications, but may include a slider 2 which is moved by an actuator and a driving body 3 which is pushed or pulled by the slider 2 to operate the gripper 1. . The driving body 3 may be implemented by various modifications, and may be configured by selecting any one that is already used in many medical robots, but preferably, may be made of a wire. That is, as the slider 2 moves horizontally, the wire may be tensioned or relaxed to use a wire method in which the gripper 1 is operated, and the gripper driving means 10 having the wire type drive body 3. The configuration of is as shown in Figure 5, this configuration is already known and a detailed description thereof will be omitted.

In the medical robot having a contact force measuring device according to the present invention, description of parts not related to the configuration for calculating the contact force of grippers similar to those of a general medical robot will be omitted.

As shown in FIGS. 1 and 4, the gripper 1 is connected to the robot arm 11 so as to be free to move, and is operated by the driving means 10 and installed at a joint portion of the driving means. There is a contact force calculation program (SW) for calculating a contact force for the gripper to contact the organ from the force or pressure sensed in the). The contact force calculation program SW may be installed in the main computer 100 installed outside the robot or in the slave computer 200 provided in the robot, but is preferably installed in the main computer 100.

The sensor S may be any type of sensor capable of detecting a force or pressure acting between the joint portion of the gripper driving means 10 or the slider 2 and the driving body, but is preferably a force sensor or There is a pressure sensor.

Similar to a conventional medical robot, but having a contact force measuring device of the present invention, the robot controls the motion controller 300 for controlling the power supplied to the actuator for operating the slider 2 and communicating with the main computer, and the motion controller. It includes a control program 110, the motion controller 300 also controls the driving of an actuator, such as a motor installed in the robot arm.

A contact force measuring method using a contact force measuring device using a force or torque measuring device in the slider of the robot arm of the gripper device according to the present invention configured as described above comprises the steps of: sensing a force or pressure generated when the sensor operates the gripper drive means; And calculating the contact force of the gripper by calculating the detected force or pressure information in the contact force calculation program.

Hereinafter, an embodiment of the present invention will be described in more detail.

Surgical slave robot system of the present invention is similar to the conventional surgical robot, as shown in Figure 1 and 2, the main control main computer 100 separated from the robot, the slave computer 200 provided in the robot ), The robot arm is provided with a slave robot arm interface. The robot arm interface may be the driving means 10 described above as a means for connecting the gripper to the robot arm.

In addition, the robot according to the present invention controls the actuators such as each motor, reads the encoder signal attached to the motor, supplies electricity to each part and communicates with the main computer, and C language It is made of a computer programming language such as, and has a control program 110 for transmitting a command directly to the motion controller, reading motor state information such as encoder signals or outputting a control signal for moving the motor.

3 is a flow chart of the software showing the data flow of the overall system. The force or pressure sensor S attached between the slider 2 and the driving body 3, which is an example of the driving means 10, collects data in real time by a callback function within the program, and the slave computer 200. Information is communicated through the NI-DAQ board attached to it. The motion controller 300 exchanges information with the main computer 100 using a communication protocol such as TCP, and in real time through a command of the control program 110, the state of the motor including the movement of the motor or the encoder signal. request.

Figure 4 shows the appearance of a surgical slave robot arm, the dotted line portion in the overall view of the left side driving means 10 (slider, hereinafter referred to as "slider"). As shown enlarged on the right side, the slider 2 is provided with a plurality for gripper motion, and each of the sliders 2 drives the driving body 3, and a sensor between the driving body 3 and the slider 2 is provided. (S) is provided.

Since a lot of wires are used as a drive system of the gripper 1, the wire will be described as a drive body. Power is transferred from the actuator to the slider, and when the surgical tool is coupled to the gripper, the force of the slider acts on the wire to transfer power to the gripper and activate the gripper.

5 is a configuration diagram for explaining the operation principle of the gripper driving means composed of a slider and a wire. Measuring the force or pressure the slider pulls or pushes through the sensor tells you the torque that is transmitted to the gripper, and conversely, the force or pressure generated by the gripper's interaction with the surroundings is transmitted to the sensor through the wiper. Therefore, changes in contact force caused by the surrounding environment can be detected.

The power transmitted to the gripper is driven by a wire driven by the movement of the slider. At this time, friction may be generated and friction compensation due to friction should be considered. Friction modeling requires model-based friction compensation and can be represented by mechanical friction models such as mass, spring, and friction. As shown in FIG. 5, the wire driving method includes an actuator, a wire, and a gripper. In this case, when the wire is modeled as a nonlinear spring, it can be represented by a dynamic equation such as Equation (1) below.

(1)

(One)

Where θ is the angle, m is the mass, c is the damping coefficient, f _fric is the friction force, f _k is the force transmitted through the _wire , K _wire is the force-displacement coefficient of the wire, f _a is the force generated by the driver, f _g is the contact force acting on the joint.

When the displacement of the actuator only only be used a wire drive, friction when friction f _fric1 in can be estimated and the actuator from the displacement is 0, the friction f _fric2 of the gripper is assuming Coulomb model, and measures the f _a f _g can be obtained.

)과 슬레이브의 위치(X_s)와의 차이가 각각의 제어기를 통과하며 합쳐지고, 각각의 모터로 전송된다. 이때 전류(I_a)와 로봇의 위치 정보가 반력 관측기로 입력되어, 추정된 힘을 출력하게 된다. 위치 및 힘 제어기는 각각 PD 제어 또는 P 제어를 사용하였고, Ka는 전압 변환 이득이고, Kt는 모터 상수이다. 반력 관측기는 외란 관측기의 개념을 이용한 것으로, 마스터-슬레이브 시스템에서 이를 통해 슬레이브 주변 환경과의 상호작용으로 발생하는 반력(F_e), 즉 접촉력을 추정할 수 있다. 파라미터 변화나 마찰에 의한 성분이 무시할 수 있을 정도로 작다고 가정하면 접촉력은 외란으로 간주할 수 있고, 외란 관측기와 동일한 구조로 표현될 수 있다.6 is a block diagram for a slave controller using a reaction torque observer. When the operator's force (F _h ) and position (X _m ) from the main computer enter the slave controller, each assumes an estimated contact force (

) And the position of the slave (X _s ) are combined through each controller and transmitted to each motor. At this time, the current I _a and the position information of the robot are input to the reaction force observer, and output the estimated force. The position and force controllers used PD control or P control, respectively, Ka is the voltage conversion gain and Kt is the motor constant. The reaction force observer uses the concept of the disturbance observer, and in this, the master-slave system can estimate the reaction force (F _e ), that is, the contact force generated by the interaction with the slave environment. Assuming that the component due to parameter change or friction is negligibly small, the contact force can be considered disturbance and can be expressed in the same structure as the disturbance observer.

은 반력 관측기의 주파수 대역을 나타내며 샘플링 시간에 따라 일반적인 힘 센서의 제한된 주파수 대역보다 더 넓은 주파수 대역을 가질 수 있다. 속도 정보는 위치 정보를 미분하고 저역 통과 필터를 통해 얻을 수 있다. 여기서,

는 저역 통과 필터의 차단 주파수를 나타낸다.FIG. 7 illustrates the reaction force observer of FIG. 6 in detail, and there is also a block line for the slave gripper using the speed controller based reaction force observer. This reaction force observer uses velocity information to estimate the contact force, where

Represents the frequency band of the reaction force observer and may have a wider frequency band than the limited frequency band of a typical force sensor depending on the sampling time. Velocity information can be differentiated from position information and obtained through a low pass filter. here,

Denotes the cutoff frequency of the low pass filter.

The estimated contact force can be obtained as in Equation (2) below.

(2)

(2)

에 입력이 되고, 이를 통해 추정된 접촉력을 얻을 수 있다. 이렇게 구해진 추정된 접촉력은 앞서 설명한 바와 같이 직접 측정된 힘과 서로 비교하여 에러를 최소화시킨 최종 추정된 힘으로 출력되게 된다.The gripper obtains velocity information from the encoder's actuator signal, which transmits power, and directly measures the force transmitted through the sensor. Velocity information is given by (2)

It is input to, and the estimated contact force can be obtained through this. The estimated contact force thus obtained is output as the final estimated force which minimizes the error compared with the directly measured force as described above.

1: gripper
10: gripper driving means
2: Slider
3: driving body
11, 12: robot arm
S: sensor
SW: contact force calculation program
100: main computer
110: control program
200: slave computer
300: motion controller

Claims (13)

In the device for measuring the contact force for transmitting a force or torque to the operator, the slave robot arm with a gripper attached to the distal end and the slave robot arm with an endoscope camera, the gripper actuated by the driving means to the organ ,
The driving means is composed of a slider operated by an actuator and a driving body for operating the gripper,
A sensor for sensing a force or pressure generated during the operation of the gripper is installed between the slider and the driving body of the driving means,
And a contact force calculation program for calculating a contact force for contacting the gripper with the organ from the force or pressure sensed by the sensor. delete The method of claim 1,
The driving body is a wire, the force or torque measuring device in the slider of the robot arm of the multi-degree of freedom gripper device, characterized in that the gripper is operated by the tension or relaxation of the wire by the movement of the slider. The method of claim 1,
The force or torque measuring device in the slider of the robot arm of the multi-degree of freedom gripper device, characterized in that the sensor is a force sensor or a pressure sensor The method of claim 1,
The contact force calculation program is installed in the main computer that controls the driving of the robot,
A motion controller for controlling power supplied to an actuator for operating the slider and communicating with a main computer; and a control program for controlling the motion controller. Torque measuring device. The method of claim 1,
The contact force τ _{e for} contacting the gripper with the organ is expressed by the following equation.

Force or torque measuring device in the slider of the robot arm of the multiple degree of freedom gripper device, characterized in that obtained. The method of claim 1,
The contact force calculation program is provided with friction compensation means,
The friction compensated contact force f _g is given by

Force or torque measuring device in the slider of the robot arm of the multiple degree of freedom gripper device, characterized in that obtained.
Where θ is the angle, m is the mass, c is the damping coefficient, f _fric is the friction force, f _k is the force transmitted through the _wire , k _wire is the force-displacement coefficient of the wire, f _a is the force generated by the driver, f _g is the contact force acting on the joint. And a slave robot arm having a gripper attached to the distal end and a slave robot arm having an endoscope camera mounted thereon, wherein a sensor is installed between the slider of the gripper driving means and the driving body for operating the gripper, and the gripper driving means is driven by an actuator. Force or torque at the slider of the robot arm of the gripper device, comprising a slider that is operated and a driving body for operating the gripper, and having a contact force calculation program that calculates a contact force for the gripper to contact the organ from the force or pressure sensed by the sensor. In the contact force measuring method using a measuring device,
Sensing by the sensor a force or pressure acting upon driving of the gripper driving means;
And calculating the contact force of the gripper by calculating the detected force or pressure information in a contact force calculation program. delete 9. The method of claim 8,
The drive body is a wire, and the wire is tensioned or relaxed by the movement of the slider to operate the gripper, and the gripper calculates the contact force of the gripper from the force or pressure between the slider and the wire sensed by the sensor. Method of measuring force or torque at the slider of the robot arm of the road gripper device. 9. The method of claim 8,
The sensor is a force sensor or a pressure sensor, characterized in that the force or torque measuring method in the slider of the robot arm of the multi-degree of freedom gripper device. 9. The method of claim 8,
The contact force τ _{e for} contacting the gripper with the organ is expressed by the following equation.

Force or torque measurement method in the slider of the robot arm of the multiple degree of freedom gripper device, characterized in that obtained. 9. The method of claim 8,
In the contact force calculation program, a friction compensation process is further performed, and in this process, the frictionally compensated contact force f _g is represented by the following equation.

Force or torque measurement method in the slider of the robot arm of the multiple degree of freedom gripper device, characterized in that obtained.
Where θ is the angle, m is the mass, c is the damping coefficient, f _fric is the friction force, f _k is the force transmitted through the _wire , k _wire is the force-displacement coefficient of the wire, f _a is the force generated by the driver, f _g is the contact force acting on the joint.

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