A control method for improving the follow-up stability of the end of a robotic arm

Abstract

The present invention discloses a control method for improving the follow-up stability of the end of a robotic arm, including: the robotic arm receives the end target posture P inital ; based on the current posture of the robotic arm, filter the end target posture P inital to obtain the posture P filter after noise elimination; correct the posture P filter to obtain the corrected posture P correct ; transform the posture P correct to the end coordinate system of the robotic arm to obtain the final posture P final ; control the robotic arm to move to the final posture P final . When the robotic arm of the knee replacement surgical robot system performs bone cutting, the present invention can track the cutting plane in real time; at the same time, it can eliminate the jitter and possible errors during the bone cutting tracking of the robotic arm, and improve the bone cutting accuracy and user experience.

Description

Technical Field

[0001] The present invention relates to the technical field of knee replacement surgical robot systems, and particularly relates to a control method for improving the follow-up stability of the end of a robotic arm, which is applied to a knee replacement surgical robot system. Background Art

[0002] Due to its good surgical accuracy and repeatability, the knee replacement surgical robot system has achieved rapid development in recent years and has become a potential technical development direction in knee replacement surgery. The knee replacement surgical robot system uses point cloud registration technology to register the coordinate systems of the patient's knee joint bone image, the physical coordinate system, and the optical positioning tool coordinate system, and uses a robotic arm for surgery.

[0003] During the surgical process, different planes need to be cut on the bone for installing prostheses; on the one hand, when cutting the bone, the robotic arm needs to ensure that the saw blade can only move on the cutting plane, but remains unchanged in other directions. Since a flexible robotic arm is used to complete bone cutting to improve the operating comfort during bone cutting, but the stiffness of the flexible robotic arm is not enough, and there will be deviations in directions other than the cutting plane due to external forces such as when holding the oscillating saw; on the other hand, to ensure that the relative position between the saw blade and the bone remains unchanged, the robotic arm needs to track the position of the bone in real time.

[0004] The existing method for the robotic arm to track the bone in real time mainly uses a vision locator to locate the position between the two. Although the accuracy of the locator is very high, there are still certain error fluctuations due to environmental factors and other factors, which will cause the saw blade to keep shaking when reflected on the robotic arm, affecting the experience and accuracy during bone cutting. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the present invention provides a control method for improving the follow-up stability of the end of a robotic arm, which can eliminate the shaking and possible errors of the robotic arm of the knee replacement surgical robot system during the bone cutting tracking process, and improve the accuracy of bone cutting and the user experience.

[0006] The present invention discloses a control method for improving the follow-up stability of the end of a robotic arm, including:

[0007] The robotic arm receives the end target posture P inital ;

[0008] Based on the current posture of the robotic arm, the end target posture P inital is filtered to obtain the posture P after noise elimination filter ;

[0009] The posture P filter is corrected to obtain the corrected posture P correct ;

[0010] Convert the pose P correct to the coordinate system of the end of the robotic arm to obtain the final pose P final ;

[0011] Control the robotic arm to move to the final pose P final .

[0012] As a further improvement of the present invention, the robotic arm receives the end target pose P inital , including:

[0013] Calculate the position information of the positioning brackets installed on the end of the robotic arm and the positioning brackets on the skeleton through a vision locator, and calculate the target pose P of the robotic arm based on the position information inital .

[0014] As a further improvement of the present invention, Kalman filtering is used to filter the end target pose P inital to obtain the pose P after noise elimination filter .

[0015] As a further improvement of the present invention, the pose P filter is corrected to obtain the corrected pose P correct ; including:

[0016] V = [0 0 f / S]

[0017]

[0018] P correct = P filter - V correct T

[0019] In the formula, f is the external force received by the end of the robotic arm in the direction perpendicular to the bone cutting plane, S is the stiffness of the end of the robotic arm in the same direction, is the transformation matrix of the end of the robotic arm relative to the base coordinate, V correct is the correction matrix of the external force received by the end of the robotic arm in the direction perpendicular to the bone cutting plane, V correct T is V correct transpose of.

[0020] As a further improvement of the present invention, the conversion of the pose P correct to the coordinate system of the end of the robotic arm to obtain the final pose P final ; including:

[0021]

[0022] In the formula, P correctis the corrected attitude of the end of the robotic arm obtained in the previous step, P current is the currently measured attitude of the robotic arm, is P correct relative to P current conversion matrix, T z , T β , T γ are the components of T in the z, β, γ directions, is the matrix after setting the components of T in the z, β, γ directions to zero.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The present invention can eliminate the jitter problem caused by real-time tracking during bone cutting of the surgical robot and the errors that may be caused by the robotic arm itself, so as to improve the accuracy of the surgical robot during bone cutting; at the same time, medical staff can be more focused on the surgical process rather than the operation of the robotic arm when using it, improving the user experience of the surgical robot and the surgical effect of the patient. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flowchart of a control method for improving the follow-up stability of the end of a robotic arm disclosed in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings:

[0028] As Figure 1 shown, the present invention provides a control method for improving the follow-up stability of the end of a robotic arm, including:

[0029] Step 1: The robotic arm receives the end target attitude P sent from the host inital ;

[0030] Specifically, it includes:

[0031] Calculate the position information of the positioning brackets installed at the end of the robotic arm and the positioning brackets on the bone through the vision locator, and calculate the target attitude P of the robotic arm based on the position information inital .

[0032] Step 2: Filter the end - target pose P inital based on the current pose of the robotic arm to obtain the pose P after noise elimination filter ;

[0033] The filtering process uses the Kalman filtering method:

[0034] F(k|k - 1)=F(k - 1|k - 1)

[0035] P(k|k - 1)=P(k - 1|k - 1)+Q

[0036] F(k|k)=F(k|k - 1)+Kg(k)(Z(k)-F(k|k - 1))

[0037] Kg(k)=P(k|k - 1) / (P(k|k - 1)+R)

[0038] P(k|k)=(1 - Kg(k))P(k|k - 1)

[0039] Step 3: Correct the pose P filter to obtain the corrected pose P correct ; where,

[0040] V = [0 0 f / S]

[0041]

[0042] P correct =P filter -V correct T

[0043] In the formula, f is the external force received by the end of the robotic arm in the direction perpendicular to the bone - cutting plane, S is the stiffness of the end of the robotic arm in the same direction, is the transformation matrix of the end of the robotic arm relative to the base coordinate, V correct is the correction matrix of the external force received by the end of the robotic arm in the direction perpendicular to the bone - cutting plane, V correct T is V correct transpose of.

[0044] Step 4: Transform the pose P correct to the end - coordinate system of the robotic arm to obtain the final pose P final ; where,

[0045]

[0046] In the formula, P correct is the corrected pose of the end of the robotic arm obtained in the previous step, P current is the currently measured pose of the robotic arm, For P correct Relative to P current transformation matrix, T z , T β , T γ are the components of T in the z, β, γ directions, is the matrix obtained by setting the components of T in the z, β, γ directions to zero.

[0047] Step 5: The host controls the robotic arm to move to the final posture P final .

[0048] Example:

[0049] This method is applied to the entire process of robotic arm-assisted bone cutting, and this method is described through one execution process.

[0050] (1) Set the actual posture of the current robotic arm as P0; the robotic arm receives the end target posture P inital . Calculate the filtered posture through the Kalman filtering method, and the calculation method is as follows:

[0051] P predict = A * P0;

[0052] P = A * A * P + Q;

[0053] Gain = P * H / (P * H * H + R);

[0054] P filter = P predict +(P inital - P predict ) * Gain;

[0055] P = (1 - Gain * H) * P;

[0056] Among them, the parameters A, H, P, Q, R are obtained through system analysis and debugging to obtain the optimal parameter values.

[0057] (2) When the user uses the end tool of the robotic arm to cut bone, there will inevitably be a downward pressure on the end, which will cause the end to deviate from the plane where the bone is to be cut, affecting the final accuracy. In this method, the influence of external forces is eliminated through a correction algorithm. The calculation method is as follows:

[0058] Obtain the external force f on the current end in the direction perpendicular to the bone cutting plane. Assume that the stiffness of the robotic arm in this direction is S. Assume:

[0059] V = [0 0 f / S]

[0060] Calculate the transformation matrix from the end of the robotic arm to the base coordinates and transform V:

[0061]

[0062] Finally, the corrected value Pcorrect is obtained.

[0063] P correct = P filter - V correct T

[0064] (3) Finally, the posture P correct is transformed into the coordinate system of the end of the robotic arm to obtain the final posture P final .

[0065] In the follow-up situation, the target posture of the end of the robotic arm needs to refer to the current posture. If the deviation from the current posture is relatively large in the non-movable direction of the end, it will cause the robotic arm to rebound, which may cause damage to the equipment or people. Therefore, it is necessary to further transform P correct to obtain the final P final .

[0066]

[0067] Set P final as the target position of the robotic arm and control the robotic arm to reach the target position.

[0068] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for improving the follow-up stability of the end of a robotic arm, Characterized in that, Comprising: The robotic arm receives the target attitude P at the end inital ; Perform filtering on the end effector target pose P based on the current pose of the robotic arm inital to obtain the pose P after noise elimination filter ; Perform calibration on pose P filter to obtain the calibrated pose P correct ; Convert the pose P correct to the end - effector coordinate system of the robotic arm to obtain the final pose P final ; Control the robotic arm to move to the final pose P final .

2. The control method according to claim 1, Characterized in that, The robotic arm receives the end target attitude P inital , including: The vision locator calculates the position information of the positioning brackets installed at the end of the robotic arm and on the skeleton, and calculates the target posture P of the robotic arm based on the position information inital .

3. The control method according to claim 1, Characterized in that, Use Kalman filtering for the attitude P of the end target inital to perform filtering processing and obtain the attitude P after noise elimination filter .

4. The control method according to claim 1, Characterized in that, The attitude P filter is corrected to obtain the corrected attitude P correct ; Comprising: V = [0 0 f / S] P correct = P filter - V correct T Where, f is the external force received by the end of the robotic arm in the direction perpendicular to the bone cutting plane, and S is the stiffness of the end of the robotic arm in the same direction. is the transformation matrix of the end of the robotic arm relative to the base coordinate, V correct is the correction matrix of the external force received by the end of the robotic arm in the direction perpendicular to the bone cutting plane, V correct T is V correct transpose.

5. The control method according to claim 1, Characterized in that, The posture P correct is transformed to the coordinate system of the end of the robotic arm to obtain the final posture P final ; Comprising: Wherein, P correct is the corrected attitude of the end of the robotic arm obtained in the previous step, and P current is the currently measured attitude of the robotic arm, is the conversion matrix of P correct relative to P current , T z , T β , T γ are the components of T in the z, β, γ directions, is the matrix obtained by setting the components of T in the z, β, γ directions to zero.

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