A surgical robot telecentric fixed point adjustment method

Abstract

The application discloses a kind of surgical robot telecentric immovable point adjustment method, comprising the following steps: establishing admittance control model;The current position of telecentric immovable point is calculated, and its initial position is combined with the external force suffered by instrument arm is adjusted to the admittance control model so that the telecentric immovable point moves in the set range, and the target position of telecentric immovable point is calculated accordingly;According to the target position of telecentric immovable point, the target position of each joint is solved and each joint is driven to move.The application can adjust the position of RCM point to release the stress of patient's body surface and robot contact, reduce the stress damage to patient's body surface, and the adjustment of RCM point is constrained in a smaller movement range, with safety protection function, to avoid the risk of excessive drag amplitude caused by human factors.

Description

Technical Field

[0001] This invention relates to the field of surgical robot technology, and in particular to a method for adjusting the telecentric fixed point of a surgical robot. Background Technology

[0002] Minimally invasive surgery has largely replaced open surgery as the main direction of development in the field of surgical medicine. Compared with traditional open surgery, minimally invasive surgery has advantages such as less trauma, less pain, and faster recovery. With the development of robotics technology, minimally invasive surgery based on robot-assisted systems, represented by the da Vinci Surgical System, has gradually matured and is widely used.

[0003] The laparoscopic surgical robot is a master-slave teleoperated system, comprising a master robotic arm and a slave robotic arm. The master robotic arm is directly controlled by the operator, while the slave robotic arm is equipped with surgical instruments. The operator can control the slave robotic arm by manipulating the master robotic arm, thereby utilizing the surgical instruments on the slave robotic arm to perform surgery on the patient. Preoperative positioning of the slave robotic arm is necessary to meet the surgical positioning requirements. The key steps of preoperative positioning are: first, making a surgical incision in the patient's skin according to the surgical procedure requirements; inserting a trocar into the surgical incision; then, moving the surgical robot to the operating table; and finally, dragging the surgical arm to adjust its position and aligning it with the trocar. Because the connection between the surgical arm and the trocar is rigid, and this process is a subjective, qualitative operation, significant stress inevitably exists at the connection point between the trocar and the patient's skin, potentially posing a risk of further injury to the patient. Therefore, it is necessary to provide a method that allows for moderate adjustment of the surgical robot's distal fixed point within safe limits after the trocar alignment is completed, thereby reducing the risk of damage to the patient's skin. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned shortcomings, this invention proposes a method for adjusting the telecentric fixed point of a surgical robot. After the tamper docking is completed, the telecentric fixed point of the surgical robot can be adjusted appropriately within a safe range to reduce the risk of damage to the patient's body surface.

[0005] Technical solution:

[0006] A method for adjusting the telecentric fixed point of a surgical robot includes the following steps:

[0007] Establish an admittance control model;

[0008] The current position of the telecentric fixed point is calculated, and the admittance control model is adjusted in combination with its initial position and the external force on the acquired robotic arm so that the telecentric fixed point moves within a set range, and the target position of the telecentric fixed point is calculated accordingly.

[0009] Based on the target position of the centroidal fixed point, the target position of each joint is determined and the movement of each joint is driven.

[0010] The stiffness coefficient of the admittance control model is 0 to achieve the requirement of free dragging of the robotic arm.

[0011] Adjusting the admittance control model specifically involves adjusting the damping coefficient within the admittance control model.

[0012] The adjustment of the damping coefficient in the admittance control model is specifically as follows:

[0013] After the card is installed, the initial position of the telecentric fixed point is calculated based on the joint angles and link information of the robotic arm.

[0014] Construct the free drag zone and the damping zone based on the initial position of the telecentric fixed point;

[0015] Calculate the real-time position of the telecentric fixed point after adjustment, and adjust the damping coefficient according to its spatial distance from the initial position:

[0016] If the telecentric fixed point is located in the free drag zone, the damping coefficient should be adjusted according to the free drag requirements of the machine arm.

[0017] If the centroidal fixed point is located in the damping region and its edge, the damping coefficient is adjusted according to the direction of the external force applied to the centroidal fixed point.

[0018] The free drag zone and damped zone are constructed based on the initial position of the telecentric fixed point as follows:

[0019] The free drag zone for adjusting the centroid fixed point is constructed with the initial position of the centroid fixed point as the center and the first radius. The area between the circular area constructed with the initial position of the centroid fixed point as the center and the second radius and the free drag zone is used as the damping zone for adjusting the centroid fixed point.

[0020] The damping coefficient is adjusted according to the direction of the external force applied at the telecentric fixed point as follows:

[0021] Calculate the angle between the vector between the initial and real-time positions of the telecentric fixed point and the vector of the applied external force;

[0022] Determine whether the included angle is below π / 2. If so, it means that the direction of the external force is towards the initial position of the centroidal fixed point. Adjust the damping coefficient according to the free dragging requirements of the machine arm.

[0023] If not, it means that the direction of the external force is away from the initial position of the centroid fixed point. If the centroid fixed point is located within the damping zone, the damping coefficient of the centroid fixed point adjustment is set to be positively correlated with the spatial distance. If the centroid fixed point is located at the edge of the damping zone, the position deviation of the centroid fixed point adjustment is set to 0.

[0024] The damping coefficient B for adjusting the telecentric fixed point is set to be positively correlated with the spatial distance r, specifically B = kr or B = kr 2 , where k represents the damping adjustment coefficient.

[0025] The adjustment of the damping coefficient according to the free dragging requirements of the robotic arm is specifically as follows:

[0026] The damping coefficient in the admittance control model is set to a constant that allows the robotic arm to drag freely, thereby obtaining the target position of the telecentric fixed point.

[0027] The external forces acting on the acquisition arm also include:

[0028] The external force on the robotic arm is detected by sensors based on the sensor coordinate system and then converted to the end effector coordinate system.

[0029] The specific steps of converting the external force on the robotic arm detected by the sensor based on the sensor coordinate system to the end effector coordinate system are as follows:

[0030] After the card is installed, the attitude transformation matrix of the sensor coordinate system relative to the robot base coordinate system is obtained by calculating the forward kinematics of the robot arm based on the current joint angles, link information and sensor installation position of the robot arm.

[0031] The attitude transformation matrix of the end effector coordinate system relative to the robot base coordinate system is calculated;

[0032] Based on the aforementioned calculation, the attitude transformation matrix of the sensor coordinate system relative to the end-effector coordinate system is obtained, and the external force on the instrument arm detected by the sensor based on the sensor coordinate system is transformed to the end-effector coordinate system.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. After the puncture card is installed, the position of the RCM point can be adjusted to release the stress on the patient's body surface in contact with the robot, thereby reducing stress damage to the patient's body surface.

[0035] 2. In this invention, the adjustment of the RCM point is constrained to a small range of motion, which has a safety protection function and avoids risks such as excessive dragging due to human factors.

[0036] 3. This invention provides operators with guiding force feedback through variable damping admittance control, making the adjustment process more subjective and controllable. Attached Figure Description

[0037] Figure 1 A schematic diagram of the structure of a robotic arm;

[0038] Figure 2This is a schematic diagram of adjusting the position of the fixed point.

[0039] Among them, 1 is the adjustment arm, 2 is the surgical arm, 3 is the instrument arm, and 4 is the force sensor. Detailed Implementation

[0040] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0041] Figure 1 This is an exemplary structural diagram of the surgical robot of the present invention, starting from the robotic arm, as shown below. Figure 1 As shown, the robotic arm includes an adjusting arm 1, a surgical arm 2, and an end-effector. The adjusting arm 1 is used to perform positioning movements, adjusting the spatial position of the RCM point (i.e., the distal fixed point). The adjusting arm 1 includes five joints J1 to J5, as shown... Figure 1 As shown, joint J1 is a rotational base joint, with its axis corresponding to S1; joints J2 and J3 are horizontal and vertical movement joints, respectively, with their axes corresponding to S2 and S3; J4 and J5 are yaw and redundant pitch joints, respectively, with their axes corresponding to S4 and S5; the surgical arm 2 includes a flip joint J6, a pitch joint composed of multiple joints and links, and an instrument arm 3 mounted on the pitch joint. The pitch joint is used to drive the distal surgical instrument to perform pitch motion around a distal fixed point. This invention does not limit the configuration of the pitch joint; any joint configuration that can realize Cartesian space motion can implement this invention. Exemplarily, the pitch joint in this invention adopts a parallelogram link structure. A sensor 4 for collecting the external force on the instrument arm 3 is mounted on the instrument arm 3.

[0042] The robot telecentric fixed point adjustment method of the present invention includes the following steps:

[0043] (1) Obtain the external force on the robotic arm through sensors;

[0044] For ease of operation, all movements of the robotic arm are based on the end-effector coordinate system. Therefore, it is necessary to convert the external forces detected by the sensors, which are based on the sensor coordinate system, to the end-effector coordinate system. Specifically:

[0045] (11) Establish a coordinate system;

[0046] With the intersection of the axes of base joints J1 and J2 as the origin, the opposite direction of gravity as the z-axis, the direction of movement of joint J2 as the x-axis, and the y-axis determined according to the right-hand rule, a robot base coordinate system O0 is established.

[0047] With the distal fixed point (RCM point) as the origin, the z-axis as the opposite direction of gravity, and the x-axis as the direction perpendicular to the z-axis and pointing forward within the normal plane of the front plane of the instrument arm (i.e., the plane formed by extending from the axis of the instrument arm towards the front side of the instrument arm), the y-axis is determined according to the right-hand rule, thus establishing the end-effector coordinate system O.t ;

[0048] With the sensor installation location as the origin, and the upward direction along the length of the instrument arm as the z-axis, and the y-axis aligned with the y-axis of the end effector coordinate system, the z-axis is determined using the right-hand rule, and a sensor coordinate system O is established. f .

[0049] (12) Convert the external force acquired by the force sensor to the coordinate system of the end effector;

[0050] After the card is installed, based on the current joint angles of the robotic arm, link information, and sensor installation positions, the attitude transformation matrix of the sensor coordinate system relative to the robot base coordinate system is obtained through forward kinematics calculation of the serial robotic arm. Where, n f o f a f These represent the orientations of the x-axis, y-axis, and z-axis of the sensor coordinate system in the robot's base coordinate system;

[0051] Based on the definition of the end effector coordinate system, the attitude transformation matrix of the end effector coordinate system relative to the robot base coordinate system can be calculated as follows: Where, n t o t a t Let x, y, and z be the orientations of the end effector coordinate system in the robot's base coordinate system, respectively. Since the z-axis of both the end effector coordinate system and the robot's base coordinate system are in the opposite direction of gravity, then a... t =[0 0 1] T Since the y-axis directions of the sensor coordinate system, robot base coordinate system, and end effector coordinate system are consistent, then o t =o f According to the right-hand rule, we can obtain

[0052] The attitude transformation matrix of the sensor coordinate system relative to the end effector coordinate system is calculated as follows: Assume the external force detected by the force sensor is F. f =[fx fy fz] T Then, transforming to the end-effector coordinate system is as follows:

[0053] (2) Establish an admittance control model;

[0054] The complete admittance control model is as follows:

[0055]

[0056] in, P eThey are respectively the acceleration deviation, velocity deviation, and position deviation for the adjustment of the telecentric fixed point. M, B, and K are respectively the inertia coefficient, damping coefficient, and stiffness coefficient;

[0057] In this invention, the free-dragging effect is realized based on the force sensor. Therefore, it can be considered that the stiffness coefficient K = 0, and the above formula can be further simplified to Then, according to the external force F obtained by the current sensor t and the velocity deviation at the current moment, the acceleration deviation at the next moment can be calculated According to the obtained acceleration deviation (t + 1), integrating once can obtain the velocity deviation at the next moment (t + 1). Integrating the velocity deviation (t + 1) can obtain the position deviation P of the telecentric fixed point at the next moment e (t + 1). In this way, the adjusted position of the telecentric fixed point can be calculated, that is, the target position P of the telecentric fixed point d = P a + P e (t + 1), where P a is the position before the adjustment of the telecentric fixed point; the inertia coefficient M is a constant matrix, which is obtained by adjusting parameters to obtain the inertia coefficient that satisfies the free dragging of the robotic arm;

[0058] (3) Perform the adjustment planning of the telecentric fixed point;

[0059] After the punch card is installed, the initial position coordinates of the telecentric fixed point in the robot base coordinate system are calculated as [x0 y0 z0] according to the joint angles and link information of the current robotic arm T , and then as the telecentric fixed point is slightly adjusted, the real-time position coordinates of the telecentric fixed point in the robot base coordinate system are [x a y a z a T , and the spatial distance from its initial position is and r changes in real time as the telecentric fixed point is adjusted;

[0060] Taking the initial position of the telecentric fixed point as the center and with a radius R0, construct the free-dragging area A for the adjustment of the telecentric fixed point; construct the damping area B for the adjustment of the telecentric fixed point between the circular area with a radius R1 centered on the initial position of the telecentric fixed point and the free-dragging area, where R1 > R0;

[0061] i. When r < R0, it means that the telecentric fixed point is within the free-dragging area. Then, the damping coefficient B for the adjustment of the telecentric fixed point is a constant matrix, which can be obtained by adjusting parameters to obtain the damping coefficient that satisfies the free dragging of the robotic arm. Define it as B c, and based on this, the target position of the telecentric fixed point is calculated according to step (2);

[0062] ii. When R0 ≤ r < R1, it indicates that the telecentric fixed point is within the damping zone. Calculate the vector between the initial position and the real-time position of the telecentric fixed point and the vector of the external force application the included angle

[0063] If it means that the direction of the external force application is towards the initial position of the telecentric fixed point. At this time, set the damping coefficient B for the adjustment of the telecentric fixed point c , and based on this, the target position of the telecentric fixed point is calculated according to step (2);

[0064] If it means that the direction of the external force application is away from the initial position of the telecentric fixed point. At this time, the damping coefficient B for the adjustment of the telecentric fixed point is positively correlated with the spatial distance r. That is, as the real-time position of the telecentric fixed point moves away from its initial position during the adjustment process, the damping coefficient B for the adjustment of the telecentric fixed point continuously increases, and the damping sense of the movement of the telecentric fixed point continuously strengthens. Based on this, the target position of the telecentric fixed point is calculated according to step (2); Specifically, it can be set as B = kr or B = kr 2 , where k represents the damping adjustment coefficient;

[0065] iii. When r = R1, it indicates that the telecentric fixed point is at the edge of the damping zone. Then calculate the vector and the vector of the external force application the included angle

[0066] If it means that the direction of the external force application is towards the initial position of the telecentric fixed point. At this time, set the damping coefficient B for the adjustment of the telecentric fixed point c , and based on this, the target position of the telecentric fixed point is calculated according to step (2);

[0067] If it means that the direction of the external force application is away from the initial position of the telecentric fixed point. Set the position deviation P e for the adjustment of the telecentric fixed point to 0, that is, the target position P d of the telecentric fixed point after adjustment is equal to its current position P a , then the telecentric fixed point no longer moves outward.

[0068] (4) Perform the adjustment of the telecentric fixed point;

[0069] Obtain the target position of the telecentric fixed point in the Cartesian space through step (3), solve for the target positions of the joints of the robotic arm through inverse kinematics, and drive the joints to move to complete the adjustment of the telecentric fixed point.

[0070] After the puncture card is installed, the position of the RCM point can be finely adjusted to release the stress on the patient's body surface in contact with the robot, reducing stress damage to the patient's body surface. In addition, the present invention provides the operator with a guiding force feedback effect through the variable damping admittance control method, making the adjustment process more subjective and controllable.

[0071] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations (such as quantity, shape, position, etc.) can be made to the technical solution of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A surgical robot system for adjusting the distal fixed point, characterized in that: include: Sensors, mounted on the robotic arm, are used to collect the external forces acting on the robotic arm; The model building module is used to build the admittance control model; The position calculation module is used to calculate the current position of the telecentric fixed point, and adjust the damping coefficient in the admittance control model by combining its initial position and the external force on the robotic arm collected by the sensor, so that the telecentric fixed point moves within a set range, and calculate the target position of the telecentric fixed point accordingly. Specifically, the position calculation module adjusts the damping coefficient in the admittance control model as follows: After the card is installed, the position calculation module calculates the initial position of the telecentric fixed point based on the joint angle and link information of the robotic arm, constructs the free drag zone and the damping zone accordingly, and calculates the real-time position of the telecentric fixed point after adjustment, thereby adjusting the damping coefficient based on the spatial distance between it and the initial position. Surgical robots are used to determine the target positions of each joint of their robotic arms based on the target position of the telecentric fixed point, and to drive the movement of each joint.

2. The surgical robot system for adjusting the distal fixed point according to claim 1, characterized in that: The stiffness coefficient of the admittance control model is 0 to achieve the requirement of free dragging of the robotic arm.

3. The surgical robot system for adjusting the distal fixed point according to claim 1, characterized in that: The position calculation module adjusts the damping coefficient based on the spatial distance between the real-time position after adjustment from the telecentric fixed point and the initial position, specifically as follows: If the distal fixed point is located in the free drag zone, the surgical robot adjusts the damping coefficient according to the free drag requirements of the instrument arm; If the distal fixed point is located in the damping zone and its edge, the surgical robot adjusts the damping coefficient according to the direction of the external force applied to the distal fixed point.

4. The surgical robot system for adjusting the distal fixed point according to claim 1, characterized in that: The surgical robot constructs a free drag zone and a damping zone based on the initial position of the distal fixed point, specifically as follows: The free drag zone for adjusting the centroid fixed point is constructed with the initial position of the centroid fixed point as the center and the first radius. The area between the circular area constructed with the initial position of the centroid fixed point as the center and the second radius and the free drag zone is used as the damping zone for adjusting the centroid fixed point.

5. The surgical robot system for adjusting the distal fixed point according to claim 1, characterized in that: The surgical robot adjusts its damping coefficient according to the direction of the external force applied at the distal fixed point as follows: The surgical robot calculates the angle between the vector between the initial and real-time positions of the telecentric fixed point and the vector of the applied external force. The surgical robot determines whether the included angle is below π / 2. If so, it indicates that the direction of the external force is towards the initial position of the telecentric fixed point. The surgical robot adjusts the damping coefficient according to the free dragging requirements of the instrument arm. If not, it means that the direction of the external force is away from the initial position of the telecentric fixed point. If the telecentric fixed point is located in the damping zone, the damping coefficient of the surgical robot set by adjusting the telecentric fixed point is positively correlated with the spatial distance. If the telecentric fixed point is located at the edge of the damping zone, the positional deviation of the telecentric fixed point adjustment of the surgical robot is set to 0.

6. The surgical robot system for adjusting the distal fixed point according to claim 5, characterized in that: The damping coefficient B for adjusting the telecentric fixed point of the surgical robot is positively correlated with the spatial distance r, specifically B = kr or B = kr. 2 , where k represents the damping adjustment coefficient.

7. The surgical robot system for adjusting the distal fixed point according to claim 3 or 4, characterized in that: The surgical robot adjusts its damping coefficient according to the free drag requirements of the surgical arm as follows: The surgical robot sets the damping coefficient in the admittance control model to a constant that allows the instrument arm to drag freely, thereby obtaining the target position of the telecentric fixed point.

8. The surgical robot system for adjusting the distal fixed point according to claim 1, characterized in that: The surgical robot detects the external force on the surgical arm based on the sensor coordinate system using the sensor, and then converts it to the end effector coordinate system.

9. The surgical robot system for adjusting the distal fixed point according to claim 8, characterized in that: Specifically, the surgical robot converts the external forces acting on the surgical arm, detected by the sensors in the sensor coordinate system, to the end-effector coordinate system as follows: After the card is installed, the surgical robot calculates the attitude transformation matrix of the sensor coordinate system relative to the robot base coordinate system through the forward kinematics of the robotic arm, based on the current joint angles of the robotic arm, the link information, and the installation position of the sensor. The surgical robot calculates the attitude transformation matrix of the end effector coordinate system relative to the robot base coordinate system; The surgical robot calculates the attitude transformation matrix of the sensor coordinate system relative to the end-effector coordinate system based on the aforementioned calculation, and transforms the external force on the instrument arm detected by the sensor based on the sensor coordinate system to the end-effector coordinate system.

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