A safety protection device for a six-degree-of-freedom parallel mechanism radiotherapy bed

Abstract

This application relates to a safety protection device for a six-degree-of-freedom parallel mechanism radiotherapy bed. The device includes a bed board and a base plate of the six-degree-of-freedom parallel mechanism radiotherapy bed, wherein three passive telescopic rods are provided in the space between the bed board and the base plate. A reflective laser rangefinder is installed inside the lower cylinder of the outer shell, with the light-receiving surface of the reflective laser rangefinder facing the lower end face of the piston telescopic rod. An electromagnetic power-off brake, consisting of an excitation part and a mechanical braking part connected vertically, is fixed to the upper port of the outer shell cylinder. This safety protection device provides redundant support in the event of a failure in the six-degree-of-freedom parallel mechanism of the radiotherapy bed, preventing bed board collapse and ensuring the safety of the patient and the radiotherapy bed itself.

Description

Technical Field

[0001] This invention relates to the field of radiotherapy, specifically to adjustable radiotherapy positioning devices, and more particularly to a radiotherapy bed with a six-degree-of-freedom parallel mechanism. Background Technology

[0002] Compared to traditional four-degree-of-freedom radiotherapy beds, six-degree-of-freedom parallel mechanism radiotherapy beds not only add the horizontal flipping function of the bed board (i.e., rotation around the X and Y axes), but also have the advantage of high positioning accuracy, thus becoming a recent research hotspot.

[0003] There are two main types of radiotherapy beds that employ a six-degree-of-freedom parallel mechanism. One type consists of six actively telescopic rods, where the six degrees of freedom of the bed board are adjusted by jointly adjusting the length of the six actively telescopic rods, as seen in the invention patent application with publication number CN105327458 A and the utility model patent application with authorization announcement number CN208990083U. The other type consists of six support rods of constant length, with a sliding mechanism consisting of a slider and a slide rail at the lower end of each support rod. The six degrees of freedom of the bed board are adjusted by jointly adjusting the position of the lower end of the six support rods to change their vertical height, as seen in the invention patent application with publication number CN 108031016A and the utility model patent application with authorization announcement number CN 213159029U.

[0004] However, existing six-degree-of-freedom parallel mechanism radiotherapy beds have many weaknesses. For example, breakage of connecting rods, reducer output shafts, motor output shafts, lead screws, or timing belts can ultimately cause the bed board to collapse or deflect, resulting in patient injury. Alternatively, belt slippage in a mechanism, or errors in parameter settings such as connecting rod length, reducer reduction ratio, or motor installation position due to carelessness or other reasons, can cause the bed board to deviate from its set trajectory, leading to incorrect patient treatment positioning. Therefore, effective monitoring and timely safety protection of the bed board posture of six-degree-of-freedom parallel mechanism radiotherapy beds are imperative.

[0005] Patent application CN 102636140A discloses a spatial six-degree-of-freedom detection device. The device has six lower ball joints 2 mounted on a fixed platform 1, forming a ring. These six lower ball joints 2 are divided into three on the left and three on the right, symmetrically distributed on both sides. Above the fixed platform 1 is a movable platform 7, on which six upper ball joints 8 are mounted, also forming a ring. Each upper ball joint 8 corresponds one-to-one with a lower ball joint 2. The upper ball joints 8 and their corresponding lower ball joints 2 are connected by a telescopic rod 3 according to the shortest distance principle. A displacement sensor 4 is mounted on the telescopic rod 3. Data from the displacement sensor 4 is transmitted via a signal line 12 to a network data acquisition card 13, and then via a network cable 14 to a computer 15. Although the detection device described in the above patent application can detect the six degrees of freedom of the moving platform 7 (equivalent to the bed board of the six-degree-of-freedom parallel mechanism radiotherapy bed), if it is to be introduced into the six-degree-of-freedom parallel mechanism radiotherapy bed to realize the detection of the six degrees of freedom of the bed board, there are obvious defects as follows: (1) The six telescopic rods 3 occupy a large space and are prone to interference with the existing six support rods of the six-degree-of-freedom parallel mechanism radiotherapy bed, or even cannot be set up; (2) There is no braking device on the telescopic rods 3, so it cannot play a redundant support role, and cannot prevent the bed board from collapsing and ensure patient safety.

[0006] Therefore, the industry is eager for the development of a safety protection device for a radiotherapy bed with a six-degree-of-freedom parallel mechanism. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a safety protection device for a radiotherapy bed with a six-degree-of-freedom parallel mechanism. This device can provide redundant support when the six-degree-of-freedom parallel mechanism of the radiotherapy bed fails, so as to avoid the bed board from collapsing and ensure patient safety.

[0008] The solution of the present invention to the above-mentioned technical problems is:

[0009] A safety protection device for a six-degree-of-freedom parallel mechanism radiotherapy bed, the safety protection device comprising a bed board and a base plate of the six-degree-of-freedom parallel mechanism radiotherapy bed, characterized in that,

[0010] Three passive telescopic rods are provided in the space between the bed board and the base plate. The lower end of each passive telescopic rod is hinged to the base plate by a Hooke hinge, and the upper end is hinged to the fixed seat on the bed board by an external threaded rod end joint bearing. The Hooke hinges are fixed to the base plate in a triangular arrangement, and the fixed seats are also fixed to the bed board in a triangular arrangement. When the six-degree-of-freedom parallel mechanism radiotherapy bed is in the initial state, all the passive telescopic rods are in an inclined state, and the three passive telescopic rods are not parallel to each other.

[0011] The passive telescopic rod consists of a housing cylinder and a piston telescopic rod fitted inside it. The lower end of the housing cylinder is connected to the Hooke hinge via a connector. The upper end of the piston telescopic rod is provided with an external thread rod end joint bearing. A reflective laser rangefinder is provided inside the lower part of the housing cylinder. The light-receiving surface of the reflective laser rangefinder is arranged opposite to the lower end face of the piston telescopic rod.

[0012] An electromagnetic power-off brake, sleeved on the piston telescopic rod, is fixed to the upper port of the outer casing cylinder. This electromagnetic power-off brake consists of an excitation section and a mechanical braking section connected vertically.

[0013] The excitation section, from top to bottom, includes a cover and a seat plate sleeved on the piston telescopic rod. An excitation coil and an armature are sleeved on the piston telescopic rod from top to bottom within the space enclosed by the cover and the seat plate.

[0014] The mechanical braking part includes a flange-shaped base extending from the upper port of the outer cylinder body to the surrounding area. A cylindrical housing is provided between the base and the seat plate of the excitation part, and an inner sleeve is provided inside the housing, which is fitted onto the piston telescopic rod. The upper end of the inner sleeve is fixed to the lower surface of the armature. The inner sleeve is provided with an annular shoulder at the lower middle part of the housing. A compression spring is fitted on the inner sleeve between the annular shoulder and the seat plate, and the seat plate and the annular shoulder protect it from being compressed. Symmetrical through holes are provided on the inner sleeve wall below the annular shoulder, radiating outward from the piston telescopic rod axis as the center point. Each through hole is embedded with a brake steel ball with a diameter larger than the thickness of the inner sleeve wall. A flared brake ring encloses the brake steel ball in the corresponding through hole.

[0015] When the excitation coil is de-energized, the tension of the compression spring drives the inner sleeve to move downward, and at this time, the brake steel ball locks the piston extension rod under the reaction of the brake ring; when the excitation coil is energized, the armature overcomes the tension of the compression spring and drives the inner sleeve to move upward, and the brake steel ball loses its restraining effect on the piston extension rod.

[0016] As can be seen from the description of the background art of this application, whether the six-degree-of-freedom parallel mechanism radiotherapy bed is safe essentially depends on whether the bed board is safe, that is, whether the current pose of the bed board is safe. As is well known, the basic design concept of the six-degree-of-freedom parallel mechanism radiotherapy bed is derived from the parallel industrial robot. Therefore, based on the working time and respective rotation angles of the six driving motors, the current theoretical pose (spatial position and orientation) of the bed board can be calculated using robotics theory (such as John J. Craig, et al. Introduction to Robotics (Third Edition) [M]. China Machine Press, 2006: 14 - 41). Then, the actual pose of the bed board detected by the safety protection device described in this application is compared. If the current theoretical pose is consistent with the actual pose, it indicates that the current pose of the bed board is "safe"; otherwise, it indicates that the current pose of the bed board is "unsafe".

[0017] As can be seen from the above solution of this application, the lengths of the three passive telescopic rods hinged at both ends to the bed board (equivalent to the moving platform in a parallel industrial robot) and the bottom plate (equivalent to the stationary platform in a parallel industrial robot) respectively are completely corresponding to the spatial position and state (i.e., RPY angles) of the bed board. Then, according to the current spatial position and RPY angles of the bed board, it is obvious that the current lengths of the three passive telescopic rods can be respectively calculated using robotics theory. Therefore, the control system supporting the safety protection device described in this application can continuously calculate the current lengths (hereinafter referred to as theoretical lengths) of the three passive telescopic rods respectively, and at the same time compare the theoretical lengths with the actual lengths measured by the corresponding reflective laser rangefinders; if the current actual lengths of the three passive telescopic rods are equal to the theoretical lengths, the control system will continue to calculate and compare the theoretical lengths and actual lengths of the three passive telescopic rods at the next moment until the bed board moves to the preset target pose and then stops. Otherwise, the control system will automatically cut off the power supply of the electromagnetic power-off brake and lock the piston telescopic rod to protect the safety of the patient.

[0018] To further protect the structural safety of the six-degree-of-freedom parallel mechanism radiotherapy bed, the control system automatically cuts off the working power supply of the entire six-degree-of-freedom parallel mechanism radiotherapy bed while automatically cutting off the power supply of the electromagnetic power-off brake.

[0019] The safety protection device for the radiotherapy bed described in this invention has the following beneficial effects:

[0020] 1. The number of passive telescopic rods is reduced from six to three, occupying less space and being convenient and flexible in distribution to avoid interference with the existing six active connecting rods;

[0021] 2. Electromagnetic power-off brakes are provided on all three passive telescopic rods. Therefore, when the pose of the bed board is unsafe, the power supply of the electromagnetic power-off brake is immediately cut off to lock the piston telescopic rod, thereby providing reliable redundant support for the bed board and ensuring the safety of the patient.

[0022] 3. Since the six-degree-of-freedom parallel mechanism radiotherapy bed is usually de-energized during the process of transferring the patient from the hospital bed to the radiotherapy bed, that is, in the state where the piston extension rod is locked by the electromagnetic de-energizer, there is no need to worry about the impact of the patient's transfer from the hospital bed to the radiotherapy bed affecting the accuracy of the radiotherapy bed. Attached Figure Description

[0023] Figure 1-3 This is a schematic diagram of the structure of a radiotherapy bed with a safety protection device described in this application, used to improve an existing six-degree-of-freedom parallel mechanism. Figure 1 Main view, Figure 2 Left view, Figure 3 This is a top view after the bed board has been removed.

[0024] Figure 4-6 for Figure 1-3 The three views of the embodiment shown are after removing the six sets of adjustment components, wherein Figure 4 Main view, Figure 5 Left view, Figure 6 This is a top view.

[0025] Figure 7-15 for Figure 4-6 The diagram shows the structure of the passive telescopic rod in the safety protection device shown. Figure 7 Main view, Figure 8 This is the left view (section view). Figure 9 for Figure 8 Enlarged view of the structure of section I. Figure 10 for Figure 8 Enlarged view of section II (electromagnetic de-energizer in de-energized state), Figure 11 for Figure 10 Sectional view A-A, Figure 12 for Figure 11 Enlarged view of the structure in section III. Figure 13 for Figure 8 Enlarged view of the electromagnetic de-energizing brake shown in Part II in the energized state. Figure 14 for Figure 13 B-B sectional view, Figure 15 for Figure 14 Enlarged view of the structure of section IV.

[0026] Figure 16 The diagram shows the motion state of the "six-dimensional treatment bed" disclosed in the authorization announcement number CN213159029U. The solid line in the diagram represents the initial state, and the dashed line represents the current state of the bed board.

[0027] Figure 17 for Figure 4-6The diagram shows the motion state of the safety protection device. The solid line in the diagram represents the initial state, and the dashed line represents the current state of the bed board.

[0028] Figure 18 for Figure 16 A schematic diagram illustrating the vector superposition principle of the pose change of the third support rod.

[0029] Figure 19 for Figure 17 A schematic diagram illustrating the vector superposition principle of the pose changes of the three passive telescopic rods.

[0030] Figure 20-22 This is a schematic diagram of the structure of a radiotherapy bed with a safety protection device described in this application used to improve another existing specific six-degree-of-freedom parallel mechanism, wherein... Figure 20 Main view, Figure 21 Left view, Figure 22 This is a top view after the bed board has been removed.

[0031] Figure 23 The diagram shows the motion state of a radiotherapy bed disclosed in the authorization announcement number CN208990083U. The solid line in the diagram represents the initial state, and the dashed line represents the current state of the bed board.

[0032] Figure 24 for Figure 23 A schematic diagram illustrating the vector superposition principle of the pose change of the first telescopic device.

[0033] Figure 25 for Figure 20-22 The diagram shows the principle of vector superposition of the pose changes of the three passive telescopic rods in the embodiment shown. Detailed Implementation

[0034] Example 1

[0035] This embodiment is a specific implementation of the safety protection device described in this application for improving the "six-dimensional treatment bed" (i.e., a six-degree-of-freedom parallel mechanism radiotherapy bed) disclosed in patent application CN213159029U. (See paragraphs

[0014] -

[0021] and appendices of patent application CN213159029U). Figure 1-3 As can be seen, the treatment board (i.e., the bed board described in this application) of this "six-dimensional treatment bed" has six sets of adjustment components between it and the base plate; wherein the adjustment components include support rods (i.e., support rods) of constant length, and each support rod has a sliding mechanism consisting of a slider and a guide rail (i.e., a slide rail) at its lower end. By jointly adjusting the position of the lower ends of the six support rods, the vertical height is changed, thereby realizing the six degrees of freedom adjustment of the bed board. From the aforementioned patent application... Figure 2As can be seen, there is a rectangular space between the four sets of adjustment components in the middle of the base plate. In this embodiment, the three passive telescopic rods described in this application are installed in this rectangular space. These three passive telescopic rods, together with the bed board and base plate of the "six-dimensional treatment bed" (i.e., a six-degree-of-freedom parallel mechanism radiotherapy bed), constitute the safety protection device described in this application. The following describes in detail, with reference to the accompanying drawings, a specific implementation scheme of the three passive telescopic rods described in this application for improving the above-mentioned "six-dimensional treatment bed".

[0036] See Figure 1-6 Four sets of adjustment components 3 in the middle between the bed board 1 and the base plate 2 (CN213159029U patent application) Figure 2 The empty space in 204 is provided with a first passive telescopic rod 4, a second passive telescopic rod 5, and a third passive telescopic rod 6; the lower end of each passive telescopic rod is hinged to the base plate 2 by a Hooke hinge 7, and the upper end is hinged to the fixed seat 9 on the bed board 1 by an external thread rod end joint bearing 8; the three Hooke hinges 7 are fixed on the base plate 2 in a triangular distribution, and the three fixed seats 9 are also fixed on the bed board 1 in a triangular distribution; when the six-degree-of-freedom parallel mechanism radiotherapy bed is in the initial state, each passive telescopic rod is in an inclined state, and the three passive telescopic rods (4, 5 and 6) are not parallel to each other.

[0037] See Figure 7-15 Each passive telescopic rod consists of a housing cylinder 10 and a piston telescopic rod 11 fitted inside it; each Hooke hinge 7 consists of an upper U-shaped frame 12, a lower U-shaped frame 13, and a cross shaft 14. The lower end of the housing cylinder 10 of the passive telescopic rod is fixedly connected to the upper U-shaped frame 12 of the Hooke hinge 7, and the upper end of the piston telescopic rod 11 is fixedly connected to the external threaded rod end joint bearing 8. A reflective laser rangefinder 15 is installed inside the lower part of the housing cylinder 10, and the light-receiving surface of the reflective laser rangefinder 15 is arranged opposite to the lower end face of the piston telescopic rod 11; an electromagnetic power-off brake 16 is fixedly fitted onto the piston telescopic rod 11 at the upper port of the housing cylinder 10, and the electromagnetic power-off brake 16 consists of an excitation part and a mechanical braking part connected at the top and bottom.

[0038] See Figure 10-15The excitation part of the electromagnetic power failure brake 16, from top to bottom, includes a cover 16-1 and a seat plate 16-2 fitted onto the piston telescopic rod 11. An excitation coil 16-3 and an armature 16-4 are fitted onto the piston telescopic rod 11 from top to bottom within the space enclosed by the cover 16-1 and the seat plate 16-2. The mechanical braking part of the electromagnetic power failure brake 16 includes a flange-shaped base 16-5 extending from the upper port of the outer cylinder 10 to the surrounding area. This flange-shaped base is connected to the excitation coil 16-3 and the seat plate 16-2. A cylindrical housing 16-6 is provided between the base plates 16-2 of the magnetic part, and an inner sleeve 16-7 is provided inside the housing, which is fitted onto the piston telescopic rod 11. The upper end of the inner sleeve 16-7 is fixed to the lower surface of the armature 16-4. The inner sleeve 16-7 is provided with an annular shoulder 16-8 in the lower middle part of the housing 16-6. A compression spring 16-9 is fitted on the inner sleeve 16-7 between the annular shoulder 16-8 and the base plate 16-2. The compression spring 16-9 is provided by the base plate 16-2. The annular shoulder 16-8 keeps it under constant pressure; the inner sleeve wall below the annular shoulder 16-8 is symmetrically provided with six through holes 16-10 radiating outwards from the axis of the piston telescopic rod 11 as the center point. Each through hole 16-10 is fitted with a brake steel ball 16-11 with a diameter larger than the wall thickness of the inner sleeve 16-7. A flared brake ring 16-12 surrounds the brake steel ball 16-11 within the corresponding through hole 16-10; when the excitation coil 16... When the excitation coil 16-3 is de-energized, the tension of the compression spring 16-9 drives the inner sleeve 16-7 to move downward. At this time, the brake ball 16-11 locks the piston extension rod 11 under the reaction of the brake ring 16-12. When the excitation coil 16-3 is energized, the armature 16-4 overcomes the tension of the compression spring 16-9 and drives the inner sleeve 16-7 to move upward. The brake ball 16-11 loses its restraining effect on the piston extension rod 11, and the piston extension rod 11 can then freely extend and retract within the outer cylinder 10.

[0039] The following describes in detail, with reference to the accompanying drawings, the working process and principle of the above-mentioned safety protection device for protecting the patient and the six-degree-of-freedom parallel mechanism radiotherapy bed itself.

[0040] I. Simplification of Mechanisms and Vector Superposition

[0041] See Figure 16 and combined Figure 1-3 To facilitate the calculation of the pose (position and orientation) of the bed board (i.e., the treatment board in the original document) described in patent application CN213159029U, we will... Figure 1-3 The adjustment component 3, namely the support rod 2043 in the "adjustment component 204" of patent application CN213159029U (i.e. Figure 1-3The first support rod 3-1A, the second support rod 3-1B, the third support rod 3-1C, the fourth support rod 3-1D, the fifth support rod 3-1E, and the sixth support rod 3-1F are represented by a straight line. The upper and lower hinge points of the six support rods 3-1A-3-1F are represented by small circles. Simultaneously, a virtual plane I (parallel to the base plate 2) is established using the plane containing the lower hinge points of the six support rods 3-1A-3-1F, and a virtual plane II (parallel to the bed board 1) is established using the plane containing the upper hinge points of the six support rods 3-1A-3-1F. The contents of patent application CN213159029U are omitted. Figure 3 The transmission mechanisms, excluding support rod 2043 and its upper and lower hinge mechanisms, are as follows. After the above simplification, the result is as follows: Figure 16 The diagram shows a simplified schematic of the six-degree-of-freedom parallel mechanism. The thin solid lines in the diagram represent the initial state of the six-degree-of-freedom parallel mechanism, and the dashed lines represent the corresponding states of the six-degree-of-freedom parallel mechanism after the state of the bed plate 1 changes.

[0042] See Figure 17 and combined Figure 4-6 For the three passive telescopic rods (4, 5, and 6), a similar simplification method is used: the Hooke's hinge 7 at the lower end of each passive telescopic rod is represented by two semi-ellipses (hinges); the hinge point of the external thread rod end spherical bearing 8 at the upper end of each passive telescopic rod is represented by a small circle; and the rod body of the passive telescopic rod, consisting of the outer cylinder 10 and the piston telescopic rod 11 fitted inside it, is simplified to the common piston cylinder telescopic symbol. Simultaneously, a virtual plane I' (parallel to the base plate 2) is established using the plane containing the hinge points of the three Hooke's hinges 7, and a virtual plane II' (parallel to the bed board 1) is established using the plane containing the hinge points of the three external thread rod end spherical bearings 8. After the above simplification, the following can be obtained: Figure 17 The diagram shows a simplified schematic of the safety protection device.

[0043] See Figure 18 and combined Figure 16 and Figure 1-3 A first static coordinate system oxyz is established on virtual plane I. The origin o of this coordinate system is located directly above the intersection of the perpendicular bisectors of the base plate 2. The x-axis is located directly above the longitudinal bisector of the base plate 2, the y-axis is located directly above the transverse bisector of the base plate 2, and the z-axis is perpendicular to the base plate 2. A first moving coordinate system OXYZ is established on virtual plane II (shown by dashed lines). When the bed plate 1 is in its initial state (i.e., in a horizontal state), the origin O of the first moving coordinate system OXYZ is also located directly above the intersection of the perpendicular bisectors of the base plate 2. The directions of the x-axis, y-axis, and z-axis are consistent with the directions of the x-axis, y-axis, and z-axis in the first static coordinate system oxyz, respectively.

[0044] See Figure 19Combination Figure 17 and Figure 4-6 A second static coordinate system o'x'y'z' is established on virtual plane I'. The z' axis of this coordinate system is collinear with the z-axis of the first static coordinate system oxyz, and the directions of the x', y', and z' axes are consistent with the directions of the x, y, and z axes in the first static coordinate system oxyz, respectively. A second moving coordinate system O'X'Y'Z' is established on virtual plane II'. When the bed board 1 is in the initial state (i.e., in the horizontal state), the z' axis of this coordinate system is also collinear with the z-axis of the first static coordinate system oxyz, and the directions of the x', y', and z' axes are consistent with the directions of the x, y, and z axes in the first static coordinate system oxyz, respectively.

[0045] See Figure 18 and combined Figure 16 and Figure 1-3 Because the existing six-degree-of-freedom parallel mechanism radiotherapy bed has a large number of support rods, it is impossible to clearly draw the vector superposition principle diagram after the pose change of the bed board 1. Figure 18 The diagram below illustrates the vector superposition principle after the pose change of the bed board 1, using only the third support rod 3-1C as an example. (See also...) Figure 18 When virtual plane II changes from a thin solid line to a dashed line, the lower endpoint A′3 of support rod 3-1C moves to point A3, while the upper endpoint B3 remains unchanged on virtual plane II, resulting in three vector triangles: △oA′3A3, △oA3B3, and △oOB3. From the method used to establish virtual plane I and virtual plane II, it can be seen that only endpoints O and B3 of the three vector triangles are on virtual plane II, while the remaining endpoints o, A′3, and A3 are on virtual plane I. Therefore, only vectors h3, a3, and a3' are on virtual plane I, b3' is on plane II, and the remaining vectors b3, c3, and p are spatial vectors in the first static coordinate system oxyz. For the remaining five support rods 3-1A, 3-1B, 3-1D, 3-1E, and 3-1F, the corresponding vector superposition principle diagram after the pose change of bed board 1 can be drawn using the same method.

[0046] See Figure 19 Combination Figure 17 and Figure 4-6 Since the passive telescopic pole consists of three pieces, it can be used in one row. Figure 19 The diagram below illustrates the vector superposition principle after the pose change of bed board 1. (See also...) Figure 19The upper hinge points K1, K2 and K3 of the three passive telescopic rods are located on the virtual plane II', and the lower hinge points S1, S2 and S3 are located on the virtual plane I'. Vectors k'1, k'2 and k'3 are located on the virtual plane II', and vectors s1, s2 and s3 are located on the virtual plane I'. Vectors 11, 12, 13, k1, k2, k3 and p' are all spatial vectors in the second static coordinate system o'x'y'z', where the modulus of vectors 11, 12 and 13 are equal to the rod length of the corresponding passive telescopic rod in the current state.

[0047] II. Determine if the bed board position is safe

[0048] Unless otherwise specified, all part numbers appearing below are from [reference needed]. Figure 1-19 .

[0049] 1. Calculate the pose of the bed board in the current state.

[0050] (1.1) According to Figure 16 Draw the vector superposition principle diagrams corresponding to the six support rods 3-1A, 3-1B, 3-1C, 3-1D, 3-1E, and 3-1F in the current state (the vector superposition principle diagram corresponding to support rod 3-1C is shown in [reference]). Figure 18 After that, the following calculation expression A) can be listed for the vectors a1-a6 of the hinge points of the six support rods 3-1A, 3-1B, 3-1C, 3-1D, 3-1E and 3-1F under the first static coordinate system oxyz:

[0051]

[0052] In equation A) above, vectors a'1—a'6 are vectors corresponding to the hinge points of the six support rods 3-1A—3-1F in the initial state. These vectors lie on the virtual plane I and can be calculated. For example, the vector a'3 corresponding to the hinge point of the third support rod 3-1C is equal to the distance from the origin o of the first static coordinate system oxyz to point A'3 multiplied by the corresponding unit vector (see equation A). Figure 18 h1-h6 are the corresponding vectors of the sliding motion of the lower hinge points of the six support rods 3-1A-3-1F from their initial positions to their current positions; where vectors h1-h6 can be calculated from the structural parameters of the radiotherapy bed described in patent application CN213159029U. See also Figure 17 Taking support rod 3-1C as an example, h3 is equal to its modulus |h3| (i.e., the sliding distance of the lower end of the third support rod 3-1C) multiplied by the unit vector n3; where, (H3 is the lead of the lead screw corresponding to support rod 3-1C, θ3 is the rotation angle of the motor corresponding to support rod 3-1C, η3 is the speed ratio of the reducer of the motor corresponding to support rod 3-1C), and n3 is a unit vector with the same direction as h3.

[0053] (1.2) Based on the vector mapping relationship, the following expression (B) is given for the spatial vectors b1-b6 corresponding to the hinge points on the six support rods 3-1A-3-1F in the first static coordinate system oxyz:

[0054]

[0055] In equation B) above, vector p represents the spatial vector corresponding to the origin of the first moving coordinate system OXYZ in the first static coordinate system oxyz, and this vector is p = [X,Y,Z]. T ;matrix Where α, β, and γ represent the angles of rotation of the virtual plane II (equivalent to bed board 1) around the x-axis, y-axis, and z-axis of the first static coordinate system oxyz, respectively; b1'—b6' are the vectors corresponding to the hinge points of the six support rods 3-1A—3-1F in the first moving coordinate system OXYZ. Since the distance between the origin of the first moving coordinate system OXYZ and the hinge points of the six support rods 3-1A—3-1F remains constant during the movement of bed board 1, vectors b1'—b6' are equal to the magnitude of vectors b1'—b6' multiplied by the corresponding unit vector (where vector b3' is referred to in the original text). Figure 18 ).

[0056] (1.3) Similarly, based on the vector mapping relationship, substitute the above expressions A) and B) into the following system of equations C) and call the fsolve function of Matlab (software version number R2017a) to solve it, and obtain the spatial position X, Y, Z of the first moving coordinate system OXYZ relative to the first static coordinate system oxyz and the RPY angles α, β, γ, that is, the pose of the bed board 1 in the current state.

[0057]

[0058] In equation C), vectors c1-c6 are the vectors corresponding to the movement of the lower hinge points of the six support rods 3-1A-3-1F. The definitions of vectors a1-a6 and b1-b6 are given in equations A and B, respectively. The symbol || represents the magnitude of the vector.

[0059] 2. Calculate the theoretical length of each passive telescopic rod under the current state.

[0060] (2.1) Coordinate system transformation

[0061] Transform the spatial positions X, Y, Z and RPY angles α, β, γ obtained in step 1 to the second static coordinate system using the following expression D):

[0062]

[0063] In equation D above, p' is the position vector of the second moving coordinate system relative to the second static coordinate system; α', β', and γ' represent the angles by which the virtual plane Ⅱ' rotates about the x' axis, y' axis, and z' axis of the second static coordinate system o'x'y'z', respectively. δ1 represents the difference in distance between virtual plane I and virtual plane I' from the upper surface of the base plate 2. δ1 is taken when virtual plane I is above virtual plane I', and -δ1 is taken when virtual plane I is below virtual plane I'. δ2 represents the difference in distance between virtual plane II and virtual plane II' from the lower surface of the bed plate 1. δ2 is taken when virtual plane II is above virtual plane II', and +δ2 is taken when virtual plane II is below virtual plane II'. The physical meanings of other symbols are as described above. T represents the transpose matrix.

[0064] (2.2) Calculate the theoretical length of the passive telescopic pole

[0065] First, based on the vector mapping relationship and the superposition principle (see... Figure 19 This yields the following expression E):

[0066]

[0067] In equation E), k1, k2, and k3 represent the vectors of the upper hinge points of the three passive telescopic rods 4, 5, and 6 in the second static coordinate system O'x'y'z', respectively. The physical meanings of p′ and R are as described above. k'1, k'2, and k'3 represent the vectors between the origin of the second moving coordinate system O'X'Y'Z' and the upper hinge points of the three passive telescopic rods 4, 5, and 6, respectively. Since the distance between the origin of the second moving coordinate system O'X'Y'Z' and the upper hinge points of the three passive telescopic rods 4, 5, and 6 remains constant during the movement of the bed board 1, vectors k'1, k'2, and k'3 are equal to the magnitudes of vectors k'1, k'2, and k'3 multiplied by the corresponding unit vectors (see [reference]). Figure 19 ).

[0068] Similarly, based on the mapping relationship of vectors and the principle of superposition (see... Figure 19 The system of simultaneous equations represented by the following equation F) is obtained:

[0069]

[0070] In the above formula (F), l1, l2, and l3 respectively represent the vectors between the upper and lower hinge points of the three passive telescopic rods 4, 5, and 6 in the second static coordinate system 'o'x'y'z'. The physical meanings of k1, k2, and k3 and the meaning of the symbol || are as described above. s1, s2, and s3 respectively represent the vectors between the origin of the second static coordinate system o'x'y'z' and the lower hinge points of the three passive telescopic rods 4, 5, and 6. This vector is known, that is, it is respectively equal to the modulus length of s1, s2, and s3 multiplied by the corresponding unit vectors;

[0071] Then, call the fsolve function of Matlab (software version number is R2017a) to solve the system of simultaneous equations represented by the above formula (F), and the theoretical lengths of the three passive telescopic rods 4, 5, and 6 in the current state can be obtained.

[0072] 3. Judgment of whether the pose of the bed board is safe

[0073] Compare the theoretical lengths of the three passive telescopic rods 4, 5, and 6 with the actually measured actual lengths of the corresponding passive telescopic rod laser rangefinders 15 respectively. If the theoretical lengths of the three passive telescopic rods 4, 5, and 6 are respectively equal to the actual lengths, it is determined that the current pose of the bed board 1 is safe, otherwise it is unsafe.

[0074] III. Safety protection

[0075] Refer to Figure 1-3 and Figure 7-9 When the safety protection device described in this application works, the supporting control system can continuously calculate the current theoretical lengths (the lengths between the upper and lower hinge points) of the three passive telescopic rods 4, 5, and 6 respectively, and at the same time compare these theoretical lengths with the actual lengths measured by the reflective laser rangefinders 15 in the corresponding passive telescopic rods respectively; if the current actual lengths of the three passive telescopic rods' 4, 5, and 6 are equal to the theoretical lengths, the control system will continue to calculate and compare the theoretical lengths and actual lengths of the three passive telescopic rods' 4, 5, and 6 at the next moment until the bed board 1 moves to the preset target pose and then terminates, otherwise the control system will automatically cut off the power supply of the electromagnetic power-off brake, lock the piston telescopic rod, and at the same time cut off the power supply of the existing six-degree-of-freedom parallel mechanism radiotherapy bed (such as the six-dimensional treatment bed described in the patent application with the authorized announcement number CN213159029U in this example) to ensure the safety of the patient and the radiotherapy bed itself. <00​​​​​​This embodiment is a specific implementation of the safety protection device described in this application for improving the "radiotherapy bed" (i.e., a six-degree-of-freedom parallel mechanism radiotherapy bed) disclosed in patent application CN208990083U. This is based on paragraphs

[0019] -

[0033] and appendices of the specification of patent application CN208990083U. Figure 1-2 As can be seen, the radiotherapy bed has six telescopic devices 3 between the bed board assembly 1 (equivalent to the bed board 1 described in this application) and the base plate 2; the telescopic rod 32 in each telescopic device 3 is hinged and fixed to the lower surface of the bed board assembly 1 and the upper surface of the base plate 2, respectively, so that the bed board assembly 1 can be adjusted in six degrees of freedom by jointly adjusting the length of the six telescopic devices 3. This is based on the aforementioned patent application. Figure 2 As can be seen, there is a gap in the middle of the base plate. In this embodiment, the three passive telescopic rods described in this application are installed in this gap. These three passive telescopic rods, together with the bed board and base plate of the radiotherapy bed (i.e., the six-degree-of-freedom parallel mechanism radiotherapy bed), form the safety protection device described in this application. The following describes in detail, with reference to the accompanying drawings, a specific implementation scheme of the three passive telescopic rods described in this application for improving the above-mentioned radiotherapy bed.

[0079] See Figure 20-22 Between the bed board 1 and the base plate 2, there are six telescopic devices: a first telescopic device 17A, a second telescopic device 17B, a third telescopic device 17C, a fourth telescopic device 17D, a fifth telescopic device 17E, and a sixth telescopic device 17F (the six telescopic devices 3 described in patent application CN208990083U). In the spaces between the six telescopic devices, there are a first passive telescopic rod 4, a second passive telescopic rod 5, and a third passive telescopic rod 6. The specific structure of the three passive telescopic rods 4, 5, and 6, and their connection relationship with the bed board 1 and the base plate 2, are exactly the same as in Embodiment 1 above. The public can refer to Embodiment 1 above. Figure 4-15 Implementation. When the six-degree-of-freedom parallel mechanism radiotherapy bed is in its initial state, each passive telescopic rod is also in an inclined state, and the three passive telescopic rods (4, 5 and 6) are not parallel to each other.

[0080] The following describes in detail, with reference to the accompanying drawings, the working process and principle of the above-mentioned safety protection device for protecting the patient and the six-degree-of-freedom parallel mechanism radiotherapy bed itself.

[0081] I. Simplification of Mechanisms and Vector Superposition

[0082] See Figure 23 and combined Figure 20-22 To facilitate the calculation of the pose (position and attitude) of the bed board 1 (i.e., bed board assembly 1 in the original document) described in the patent application with authorization publication number CN208990083U, we use its... Figure 1-2 The six telescopic devices 3 in the middle, namely Figure 20-22The first telescopic device 17A, the second telescopic device 17B, the third telescopic device 17C, the fourth telescopic device 17D, the fifth telescopic device 17E, and the sixth telescopic device 17F are represented using common piston cylinder telescopic symbols. The upper and lower hinge points of the six telescopic devices 17A-17F are represented by small circles. Simultaneously, a virtual plane I (parallel to the base plate 2) is established using the plane containing the lower hinge points of the six telescopic devices 17A-17F, and a virtual plane II (parallel to the bed board 1) is established using the plane containing the upper hinge points of the six telescopic devices 17A-17F. After the above simplification, the following is obtained: Figure 23 The diagram shows a simplified schematic of the six-degree-of-freedom parallel mechanism. The thin solid lines in the diagram represent the initial state of the six-degree-of-freedom parallel mechanism, and the dashed lines represent the corresponding states of the six-degree-of-freedom parallel mechanism after the state of the bed plate 1 changes.

[0083] See Figure 24 and combined Figure 20-22 A first static coordinate system oxyz is established on virtual plane I. The origin o of this coordinate system is located directly above the intersection of the perpendicular bisectors of the base plate 2. The x-axis is located directly above the longitudinal bisector of the base plate 2, the y-axis is located directly above the transverse bisector of the base plate 2, and the z-axis is perpendicular to the base plate 2. A first moving coordinate system OXYZ is established on virtual plane II (shown by dashed lines). When the bed plate 1 is in its initial state (already horizontal), the origin O of the first moving coordinate system OXYZ is also located directly above the intersection of the perpendicular bisectors of the base plate 2. The directions of the x-axis, y-axis, and z-axis are consistent with the directions of the x-axis, y-axis, and z-axis in the first static coordinate system oxyz, respectively.

[0084] See Figure 24 and combined Figure 20-23 Because the existing six-degree-of-freedom parallel mechanism radiotherapy bed has a large number of telescopic devices, it is impossible to clearly draw the vector superposition principle diagram after the pose change of the bed board 1. Figure 24 The diagram below illustrates the vector superposition principle after the pose change of the bed board 1, using only the first telescopic device 17A as an example. (See also...) Figure 24 When the virtual plane II changes from a thin solid line state to a dashed line state, the first telescopic device 17A changes from a thin solid line state to a dashed line state (see...). Figure 23 From the methods used to establish virtual plane I and virtual plane II, it can be seen that... Figure 24 Of the vectors shown, only vector e1' lies on virtual plane II, u1 lies on virtual plane I, and the remaining vectors e1, p, and q1 are spatial vectors in the first static coordinate system oxyz. For the remaining five telescopic devices 17B-17F, refer to... Figure 23 Using the same method, draw the corresponding vector superposition principle diagram after the pose change of bed board 1. This vector superposition principle diagram is similar to... Figure 24 .

[0085] The three passive telescopic rods (4, 5, and 6) described in this example can be simplified using the same method as in Example 1 to obtain a similar result. Figure 17 The diagram shows the motion state of the safety protection device. The methods for establishing the virtual planes I' and II', and the corresponding second static coordinate system o'x'y'z' and second moving coordinate system O'X'Y'Z' in this example are the same as in Embodiment 1. For details on the establishment methods, please refer to [link to previous document]. Figure 25 .

[0086] See Figure 25 and combined Figure 20-22 Using the same method as in Example 1, a vector superposition diagram of the pose changes of the three passive telescopic rods at positions 4-6 in the example was obtained. The content represented by each number in the diagram is also the same as in Example 1. Figure 19 same.

[0087] II. Determine if the bed board position is safe

[0088] Unless otherwise specified, all part numbers appearing below are from [reference needed]. Figure 20-25 .

[0089] 1. Calculate the pose of the bed board in the current state.

[0090] See Figure 24 and combined Figure 23 Based on the mapping relationship of vectors and the superposition principle, the following system of equations, represented by expression G), can be obtained:

[0091]

[0092] In the above equation G), the physical meaning of each operation symbol is as follows:

[0093] |q1|—|q6| represent the modulus of vectors q1, q2, q3, q4, q5, and q6, respectively. This modulus is equal to the initial length of the corresponding telescopic device plus the elongation in its current state. The initial length of the telescopic device can be measured, and the elongation in its current state is equal to... (In the formula, i is a natural number 1, 2, 3, 4, 5, 6, which represent the numbers of the telescopic devices; θ) i η corresponds to the rotation angle of the motor in the telescopic device. i To correspond to the speed ratio of the reducer in the telescopic device, σ i (This refers to the lead of the lead screw and nut pair in the corresponding telescopic device);

[0094] |e1-u1|—|e6-u6| represent the magnitudes of vectors e1 minus vector u1, e2 minus vector u2, e3 minus vector u3, e4 minus vector u4, e5 minus vector u5, and e6 minus vector u6, respectively; where the expression for vector e1—vector e6 is shown in equation F below:

[0095]

[0096] In the above formula H),

[0097] The vector is p = [X, Y, Z] T Where X, Y, and Z represent the coordinates of the origin of the first moving coordinate system in the first static coordinate system in the current state;

[0098] Matrix R is the same as in Example 1, that is Where α, β and γ represent the angles of rotation of the virtual plane Ⅱ (equivalent to bed board 1) around the x-axis, y-axis and z-axis of the first static coordinate system oxyz, respectively;

[0099] Vectors e'1 to e'6 represent the vectors between the origin of the first moving coordinate system OXYZ and the hinge points of the six telescopic devices 17A to 17F in the current state. These vectors are in the virtual plane II and can be measured (equal to the distance between the origin of the first moving coordinate system OXYZ and the hinge points of the six telescopic devices 17A to 17F multiplied by the corresponding unit vector).

[0100] Next, the fsolve function of Matlab (software version R2017a) is called to solve the system of equations represented by the above equation G), thus obtaining the spatial position X of the first moving coordinate system OXYZ relative to the first static coordinate system oxyz in the current state. , Y , Z and RPY angles α, β, γ represent the pose of bed board 1 in the current state.

[0101] After obtaining the position of the bed board 1, the methods for calculating the theoretical lengths of the three passive extension rods 4, 5 and 6, as well as for determining whether the position of the bed board 1 is safe and protecting the safety of the patient and the radiotherapy bed itself, are the same as in Example 1.

Claims

1. A safety protection device for a six-degree-of-freedom parallel mechanism radiotherapy bed, the safety protection device comprising a bed board and a base plate of the six-degree-of-freedom parallel mechanism radiotherapy bed, characterized in that, The bed board and the base plate are provided with six sets of adjustment components; each adjustment component includes a support rod of constant length; the lower end of each support rod is provided with a sliding mechanism consisting of a slider and a slide rail, and the vertical height of the bed board is changed by adjusting the position of the lower end of the six support rods in combination, thereby realizing the six degrees of freedom adjustment of the bed board; there is a rectangular space between the four sets of adjustment components in the middle of the base plate; three passive telescopic rods are also provided in the space between the bed board and the base plate, and the lower end of each passive telescopic rod is hinged to the base plate by a Hooke hinge, and the upper end is hinged to the fixed seat on the bed board by an external thread rod end joint bearing; the Hooke hinges are fixed to the base plate in a triangular distribution, and the fixed seats are also fixed to the bed board in a triangular distribution; when the radiotherapy bed of the six degrees of freedom parallel mechanism is in the initial state, the passive telescopic rods are all in an inclined state, and the three passive telescopic rods are not parallel to each other. The passive telescopic rod consists of a housing cylinder and a piston telescopic rod fitted inside it. The lower end of the housing cylinder is connected to the Hooke hinge via a connector. The upper end of the piston telescopic rod is provided with an external thread rod end joint bearing. A reflective laser rangefinder is provided inside the lower part of the housing cylinder. The light-receiving surface of the reflective laser rangefinder is arranged opposite to the lower end face of the piston telescopic rod. An electromagnetic power-off brake, sleeved on the piston telescopic rod, is fixed to the upper port of the outer casing cylinder. This electromagnetic power-off brake consists of an excitation section and a mechanical braking section connected vertically. The excitation section, from top to bottom, includes a cover and a seat plate sleeved on the piston telescopic rod. An excitation coil and an armature are sleeved on the piston telescopic rod from top to bottom within the space enclosed by the cover and the seat plate. The mechanical braking part includes a flange-shaped base extending from the upper port of the outer cylinder body to the surrounding area. A cylindrical housing is provided between the base and the seat plate of the excitation part, and an inner sleeve is provided inside the housing, which is fitted onto the piston telescopic rod. The upper end of the inner sleeve is fixed to the lower surface of the armature. The inner sleeve is provided with an annular shoulder at the lower middle part of the housing. A compression spring is fitted on the inner sleeve between the annular shoulder and the seat plate, and the seat plate and the annular shoulder protect it from being compressed. Symmetrical through holes are provided on the inner sleeve wall below the annular shoulder, radiating outward from the piston telescopic rod axis as the center point. Each through hole is embedded with a brake steel ball with a diameter larger than the thickness of the inner sleeve wall. A flared brake ring encloses the brake steel ball in the corresponding through hole. When the excitation coil is de-energized, the tension of the compression spring drives the inner sleeve to move downward. At this time, the brake steel ball locks the piston telescopic rod under the reaction of the brake ring. When the excitation coil is energized, the armature overcomes the tension of the compression spring and drives the inner sleeve to move upward, and the brake ball loses its restraining effect on the piston extension rod.

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