A medical electron linear accelerator frame structure with high-precision positioning

Abstract

The present invention discloses a medical electron linear accelerator frame structure with high-precision positioning. The invention belongs to the field of motion mechanism, measuring mechanism and fixed frame structure and motion control thereof, and includes motion mechanism, measuring mechanism and fixed frame; wherein the motion mechanism includes a rotating frame, dual-drive motor gears, gear bearings, drag chain and component support mechanism, etc., and the dual-drive motor gear anti-backlash technology is used to realize the precise rotational motion and positioning of the motion mechanism; in addition, the measuring mechanism adopts the coupling measurement technology of photoelectric encoder and circular grating to realize the precise measurement of the angle position under different motion states; at the same time, the motion control system of the medical linear accelerator collects the position measurement signal to control the dual-drive motor gears, and finally realizes the precise positioning of the angle position of the rotating frame through the motion mechanism.

Description

Technical Field

[0001] The invention belongs to the field of motion mechanisms, measuring mechanisms and fixed frame structures and motion control thereof, and relates to a high-precision medical linear accelerator; more specifically, to a high-precision positioning medical electron linear accelerator frame structure. Background Art

[0002] During radiotherapy, the medical electron linear accelerator needs to rotate the frame to achieve different angles and speeds. Currently, gear transmission is a common transmission method for medical electron linear accelerators, and gears can achieve very high mechanical precision through fine processing.

[0003] In order to reduce friction and compensate for errors in the manufacturing or assembly process, there will be a certain amount of tooth clearance in the design of the gear, which will cause the load to rotate a very small angle during the reverse transmission transition, thereby affecting the positioning accuracy of the rotating frame. When the rotating frame of the medical electron linear accelerator adopts gear transmission, the gear tooth clearance of the gear bearing is generally 1-2mm, which will cause a small angle deviation of 0.1-0.2°. Although this deviation meets the standard requirements, precision radiation technology pursues smaller angle deviations and higher positioning accuracy. In addition, if a large load is driven to rotate, the tooth clearance will cause large vibrations when the master and slave gears come into contact, generate noise, and even damage the motion mechanism. Therefore, for the linear accelerator motion mechanism that frequently changes the direction of rotation, a better solution should be adopted for gear transmission.

[0004] As for the angle measurement method of medical electron linear accelerator, the photoelectric encoder method is currently widely used. It is small in size and mature in technology. However, due to manufacturing errors, assembly and installation, its measurement accuracy may even exceed the allowable value of the national standard. Therefore, in order to ensure that the measurement results truly reflect the actual angle position and ensure that the positioning accuracy of the rack is within the 0.5° required by the national standard, it is necessary to add another angle measurement method for comparison and reference, such as circular grating. The measurement accuracy of circular grating is higher than that of photoelectric encoder in static state, but the resolution and measurement accuracy are reduced in dynamic measurement. In actual use, circular grating is used as the main measurement method in static state, and photoelectric encoder is used as the main measurement method in dynamic state. The two measurement results are compared at the same time to provide a reference for the operator's decision. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a medical electron linear accelerator frame structure with high-precision positioning, which meets the control requirements of the precise movement of the medical electron linear accelerator and ensures the stable and reliable operation of the medical electron linear accelerator.

[0006] Technical solution: The high-precision positioning medical electron linear accelerator frame structure of the present invention comprises a base, and a fixed frame and a rotating frame are respectively installed on the upper end of the base;

[0007] A gear bearing is arranged between the fixed frame and the rotating frame;

[0008] A second driving motor is installed at the connection between the fixed frame and the base, and a first driving motor is installed at the other end of the fixed frame;

[0009] Two grating plates, grating plate 1 and grating plate 2, are respectively installed at both ends of the rotating frame;

[0010] A driving motor gear 1 is installed at the top end of the gear bearing, and a driving motor gear 2 is installed at the other end close to the base;

[0011] A tow chain is installed on the fixed frame;

[0012] An image-guided ray generator and a support thereof and an image-guided receiver and a support thereof are installed on the rotating gantry, and the image-guided ray generator and a support thereof and the image-guided receiver and a support thereof are symmetrically arranged about the central axis of the rotating gantry;

[0013] A dose guiding device and its support and a radiation head and its support are installed on the rotating frame, and the dose guiding device and its support and the radiation head and its support are symmetrically arranged about the central axis of the rotating frame;

[0014] The central axis line of the image guidance ray generator and its support and the image guidance receiver and its support projection on the rotating frame is perpendicular to the central axis line of the dose guidance device and its support and the radiation head and its support projection on the rotating frame.

[0015] Furthermore, a power supply is also included.

[0016] Beneficial effects: Compared with the prior art, the present invention can improve the positioning and measurement accuracy of the rotating frame, ensuring more accurate positioning when using precise radiotherapy techniques, such as intensity-modulated radiotherapy and rotational intensity-modulated radiotherapy; the dual-gear drive method adopted by the motion mechanism can improve the positioning accuracy while also reducing the collision between gears, reducing noise, reducing the risk of gear damage, and extending the life of the gears; the dual-gear drive uses two independent motors, and when one motor fails, the other motor can continue to ensure the movement of the rotating frame; a precise measuring mechanism coupled with a photoelectric encoder and a circular grating is used, so that the angle of the rotating mechanism under different working conditions can be accurately measured, and the measurement results are fed back to the control system in real time to control the precise rotation of the rotating frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the present invention;

[0018] Figure 2 yes Figure 1The main view of

[0019] Figure 3 It is a schematic diagram of the arrangement of the double gears and the measuring mechanism in the structure of the present invention;

[0020] Figure 4 is a schematic diagram of rack motion control provided by an embodiment of the present invention;

[0021] Figure 5 This is a precise measurement workflow diagram provided by an embodiment of the present invention;

[0022] In the figure, 1 is a fixed frame, 2 is a rotating frame, 3 is a gear bearing, 4 is a drag chain, 5 is a drive motor gear 1, 6 is a drive motor 1, 7 is a drive motor gear 2, 8 is a drive motor 2, 9 is a radiation head and its support, 10 is a dose guidance device and its support, 11 is an image guidance ray generator and its support, 12 is an image guidance receiver and its support, 13 is a light source, 14 is a reflector 1, 5 is a lens 1, 16 is a grating plate 1, 17 is a fixed grating, 18 is a photosensitive tube, 19 is a reflector 2, 20 is a lens 2, 21 is a grating plate 2, 22 is an indicator grating, 23 is a lens 3, and 24 is a photoelectric element. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0024] As shown in the figure, a medical electron linear accelerator frame structure with high-precision positioning according to the present invention comprises a base, and a fixed frame 1 and a rotating frame 2 are respectively installed at the upper end of the base;

[0025] A gear bearing 3 is installed between the fixed frame 1 and the rotating frame 2;

[0026] A second driving motor 8 is installed at the connection between the fixed frame 1 and the base, and a first driving motor 6 is installed at the other end of the fixed frame 1;

[0027] Two grating plates, grating plate 1 16 and grating plate 21, are respectively installed at both ends of the rotating frame 2;

[0028] A driving motor gear 1 5 is installed at the top end of the gear bearing 3, and a driving motor gear 2 7 is installed at the other end close to the base;

[0029] A drag chain 4 is installed on the fixed frame 1;

[0030] An image-guided ray generator and its support 11 and an image-guided receiver and its support 12 are installed on the rotating gantry 2. The image-guided ray generator and its support 11 and the image-guided receiver and its support 12 are symmetrically arranged about the central axis of the rotating gantry 2.

[0031] A dose guiding device and its support 10 and a radiation head and its support 9 are installed on the rotating gantry 2, and the dose guiding device and its support 10 and the radiation head and its support 9 are symmetrically arranged about the central axis of the rotating gantry 2;

[0032] The central axis line of the projections of the image-guided ray generator and its support 11 and the image-guided receiver and its support 12 on the rotating gantry 2 is perpendicular to the central axis line of the projections of the dose guidance device and its support 10 and the radiation head and its support 9 on the rotating gantry 2.

[0033] Furthermore, a power supply 13 is also included.

[0034] Specifically,

[0035] A high-precision positioning medical electron linear accelerator frame structure is used to improve the rotation accuracy and positioning accuracy of the medical electron linear accelerator frame, mainly including a motion mechanism, a measuring mechanism and a fixed frame;

[0036] The motion mechanism mainly includes a rotating frame 2, dual drive motors (drive motor 1 6 and drive motor 2 8) and drive motor gears (drive motor gear 1 5 and drive motor gear 2 7), gear bearings 3, drag chains 4 and various component equipment supports;

[0037] The measuring mechanism mainly includes two measuring systems: a photoelectric encoder and a circular grating;

[0038] The high-precision positioning medical electron linear accelerator frame structure is specifically:

[0039] The motion mechanism adopts a double gear drive mode to improve the positioning accuracy and stability of the rotating frame 2 during the rotation process;

[0040] The measuring mechanism couples the two measuring methods of the photoelectric encoder and the circular grating to monitor the motion state and angular position of the rotating frame 2 in real time;

[0041] The measuring mechanism of the medical electron linear accelerator frame structure feeds back the position information to the accelerator control system, and the control system adjusts the torque and rotation direction of the two driving gears according to the position information to realize the forward and reverse rotation of the frame without tooth gap;

[0042] As for the motion mechanism, the specific features are as follows: in the layout of the motion mechanism, the double gears are arranged symmetrically with the rotating frame 2, the gear bearings 3 are subjected to balanced forces, and the accelerator rotating frame 2 runs more stably and is positioned more accurately;

[0043] In the running state of the motion mechanism, when the rotating frame 2 is in a stationary state, the driving torques of the two driving gears are equal in magnitude and opposite in direction, and the backlash in the rotation direction is completely eliminated; when the frame starts to rotate, the torque of one driving gear gradually increases, and the torque and direction of the other driving gear gradually change, and finally the frame is driven to move in the same direction; during the movement of the frame, the tooth surface of one driving gear is always in full meshing with the large gear surface of the gear bearing 3, thereby realizing backlash-free drive of the frame;

[0044] As for the measuring mechanism, it is specifically: the photoelectric encoder measuring system is used as the main measuring method when the rotating frame 2 is in motion, and measures the angle of the rotating frame 2 in real time;

[0045] The circular grating measurement system is used as the main measurement method when the rotating frame 2 is stationary to measure the actual angle of the rotating frame 2;

[0046] The measuring mechanism uses the same light source 13 to project the light source to different measuring systems through the reflector 14, and feeds back the measurement signal to the control system of the gear drive motor to control the precise positioning of the angle of the rotating frame 2 in real time;

[0047] As for the frame structure, the specific structure is as follows: the gear drive motor drives the rotating frame 2 to rotate or stop through a dual-gear drive mode, the photoelectric encoder and the circular grating system perform real-time measurement, and the measurement results are transmitted to the control system for real-time comparison; when the measurement results of the photoelectric encoder and the circular grating differ within the allowable θ angle range, the measurement data of the photoelectric encoder is transmitted to the drive motor through the control system in real time, and the size and direction of the torque of the dual-gear drive motor are adjusted, thereby controlling the motion state of the rotating frame 2 to ensure the precise positioning of the rotating frame 2; when the measurement results of the photoelectric encoder and the circular grating exceed a certain θ angle range, the machine is stopped for inspection to determine whether there is a measurement device failure;

[0048] As for the motion mechanism, it is specifically as follows: the motion mechanism mainly includes a rotating frame 2, dual drive motors (drive motor 1 6 and drive motor 2 8) and drive motor gears (drive motor gear 1 5 and drive motor gear 2 7), gear bearings 3, drag chains 4 and various component equipment supports (image-guided receiver and its support 12, image-guided ray generator and its support 11 and dose-guided device and its support 10, etc.);

[0049] The motion mechanism, specifically including the radiation head and its support 9, the image-guided ray generator and its support 11, the image-guided receiver and its support 12, the dose-guided device and its support 13, etc., are symmetrically distributed on the X and Y axes, and the rotating frame 2 is subjected to overall force balance to achieve smooth rotation of the frame;

[0050] As for the frame structure, it is specifically as follows: the frame mechanism, the moving mechanism and the fixed frame 1 are connected by a gear bearing 3, the gear bearing 3 provides support for the moving mechanism and drives the rotating frame 2 to rotate through gear transmission.

[0051] The frame structure provided by the embodiment of the present invention adopts a double-gear drive, and two driving gears and a large gear of the gear bearing 3 form two groups of driving units, and a bias torque is established in the two groups of driving units through a control system; there is always a tooth surface of the two driving gears in meshing with the tooth surface of the large gear, so that the large gear cannot swing between the gears, thereby achieving the purpose of eliminating the gap. Due to its excellent gap elimination advantage, it can significantly reduce vibration, eliminate noise, and accurately position; at the same time, the double-gear drive technology is adopted, the power required by a single drive motor is smaller, and the motor size is also smaller, so that the overall size of the medical electron linear accelerator is smaller; and a symmetrical layout is adopted, so that the force of the rotating mechanism of the medical electron linear accelerator is more balanced.

[0052] Furthermore, an embodiment of the present invention provides a measuring mechanism that adopts two angle measurement technologies. In addition to the traditional commonly used photoelectric encoder technology, a circular grating measurement technology is added. The circular grating method in the angle measurement technology is a measurement technology with higher precision, especially in static conditions. This method is also a future direction of medical electron linear accelerator angle measurement technology. The two measurements are used in different states to give full play to their respective excellent characteristics, and at the same time, the measurement results are compared for reference, which is conducive to the operator to grasp the actual angle position more accurately. Example

[0053] The embodiment of the present invention provides a medical electron linear accelerator frame structure with high-precision positioning, which improves the positioning accuracy of the rotating frame through double-gear anti-backlash technology; uses two angle measurement coupling mechanisms to improve the accuracy of position measurement, thereby improving the positioning accuracy of the frame.

[0054] Specifically, the frame structure mainly includes: a motion mechanism, a measuring mechanism and a fixed frame 1;

[0055] Among them, the motion mechanism includes a rotating frame 2, dual drive motor gears, a gear bearing 3, a radiation head and its support 9, an electronic portal imaging device support, an image-guided radiotherapy device support, a drag chain 4, etc.; the gear bearing 3 is used to connect the drive motor and the rotating frame 2, and convert electrical energy into kinetic energy of the rotating frame 2 through the drive motor gear transmission. At the same time, the gear bearing 3 is also a load transfer medium between the fixed frame 1 and the rotating frame 2. The load generated by each device / component on the rotating frame 2 is transmitted to the fixed frame 1 through the gear bearing 3; the rotation of the gear bearing 3 is controlled simultaneously by the upper and lower gears, and each gear and the large gear of the gear bearing 3 form a group of drive units. The two groups of drive units use the offset torque established in the electrical control system to ensure that the drive gear of at least one of the two groups of drive units is always in meshing with the tooth surface of the large gear, thereby completely eliminating the problems of low positioning accuracy and high noise caused by the existence of tooth gap during single gear movement;

[0056] Specifically, the measuring mechanism includes a photoelectric encoder and a circular grating; in a moving state, the photoelectric encoder is used to measure the angle; the photoelectric encoder converts the geometric displacement of the rotating frame into a pulse signal through photoelectric conversion, determines the rotation speed by calculating the number of pulses, and then determines the position of the rotating frame 2; the rotation direction of the rotating frame 2 can be determined by outputting two optical code signals with a phase difference of 90°; in a static state, the circular grating measurement technology is used to measure the angle; the circular grating measurement is based on the Moire fringe principle, and the photoelectric element determines the number of grating pitches of the grating movement by reading the number of moving Moire fringes, thereby obtaining the accurate angular displacement of the rotating frame.

[0057] When existing medical electron linear accelerators use gear transmission, they all use single gear transmission. Due to the tooth clearance problem caused by design or long-term operation wear, the positioning accuracy of the rotating frame 2 will be seriously affected; in existing medical electron linear accelerators, a single technology is mostly used for accurate angle measurement. When an error occurs in the equipment, the accurate position of the rotating frame cannot be truly reflected; the positioning mechanism of this embodiment is adopted, using double gear drive, and through precise electronic control technology, the tooth clearance-free movement of the rotating frame 2 can be achieved, and the positioning accuracy can be significantly improved; two angle measurement technologies are used to achieve accurate measurement under different conditions. Example

[0058] As shown in the figure, this embodiment provides a frame structure, the radiation head and its support 9, the dose guidance device and its support 10, the image guidance ray generator and its support 11, and the image guidance receiver and its support 12 are connected to the rotating frame 2 by welding or bolts; the rotating frame 2 is connected to the gear bearing 3 by bolts, and the rotation of the rotating frame 2 is driven by the drive motor gear 5 / 6 meshing with the gear bearing 3. The stator of the gear bearing 3 is connected to the fixed frame 1 by bolts, and the fixed frame 1 is used to support all the loads of the accelerator; the electrical signal cable is coiled on the drag chain 4 through the drag chain, and the drag chain 4 is connected to the rotating frame 2 by bolts or welded with support rods, and the drag chain 4 rotates with the rotating frame 2; the double gear structure provided in this embodiment has the following working principle: Figure 4 As shown, when the position deviation is greater than X1, the bias torque is 0, the torques of the drive motor 1 6 and the drive motor 2 8 are equal in magnitude and in the same direction, and the drive motor gear 1 5 and the drive motor gear 2 7 are simultaneously meshed with the tooth surfaces of the gear bearing 3 in the same direction, so that the gear bearing 3 rotates in one direction; when the position deviation is between 0 and X1, the control system provides a bias torque through current and voltage regulation, inputs a positive torque to the drive motor 1 6, and inputs a reverse torque to the drive motor 2 8. As the position deviation decreases to 0, the bias torque gradually increases to a maximum value, and the torques of the drive motor 1 6 and the drive motor 2 8 gradually decrease, and the torque of the drive motor 2 8 decreases faster. Finally, the torques of the two motors are equal in magnitude and in opposite directions, so that the gear bearing 3 is in a stationary state; when the position deviation is less than -X1, the drive motor 1 6 and the drive motor 2 The torques of 8 are equal in magnitude and direction, and the drive motor gear 1 5 and the drive motor gear 2 7 are meshed with the tooth surface of the gear bearing 3 in the other direction at the same time, so that the gear bearing 3 rotates in the opposite direction; when the position deviation is between -X1 and 0, the control system provides a bias torque through current and voltage regulation, inputs positive torque to the drive motor 2 8, and inputs reverse torque to the drive motor 1 6. As the position deviation decreases to 0, the bias torque gradually increases to the maximum value, and the torques of the drive motor 1 6 and the drive motor 2 8 gradually decrease. The torque of the drive motor 1 6 decreases faster, and finally the torques of the two motors are equal in magnitude and opposite in direction, so that the gear bearing 3 is in a stationary state; during the whole process, when moving in two different directions, there is always a small gear tooth surface meshing with the large gear tooth surface of the gear bearing 3, completely eliminating the backlash. Whether it is the machining accuracy of the large gear or the shape change of the large gear surface during long-term operation, there will be no backlash, thereby ensuring the positioning accuracy of the rotating frame. At the same time, the driving motor gear 5 and the driving motor gear 2 7 are arranged symmetrically on both sides of the large gear of the gear bearing 3. The two small gears have a mutually offsetting effect on the two radial components of the large gear of the gear bearing, reducing the small deformation and displacement caused by the unbalanced stress on the large gear for a long time, which ultimately affects the positioning accuracy of the rotating frame. Example

[0059] As shown in the figure, this embodiment provides a motion mechanism, in which the main functional components such as the radiation head and its support 9, the image-guided ray generator and its support 11, the image-guided receiver and its support 12 on the rotating frame are symmetrically distributed on the X and Y axes. The rotating frame 2 is overall balanced in force and runs more smoothly. Example

[0060] As shown in the figure, this embodiment provides a measuring mechanism; this embodiment includes two measuring systems, namely a photoelectric encoder measuring system and a circular grating measuring system; the photoelectric encoder measuring system is composed of a light source 13, a radiator 14, a lens 15, a grating plate 16, a fixed grating 17, and a photosensitive tube 18; the light source 13 can be a light emitting diode, which is installed on a fixed support, and the light of the light source 13 is converted into parallel light through a reflector 14 and a lens 15; the parallel light passes through a grating plate 16 fixedly connected to the rotating frame 2 and irradiates the fixed grating 17, and the photosensitive tube 18 receives the light signal of the fixed grating 17 and converts it into an electrical signal, and determines the angle and rotation direction of the rotating frame 2 through the electrical signal;

[0061] The circular grating measurement system comprises a light source 13, a second reflector 19, a second lens 20, a second grating plate 21, an indicator grating 22, a third lens 23 and a photoelectric element 24; the light emitted by the fixed light source 13 is converted into parallel light by the second reflector 19 and the second lens 20, passes through the second circular grating plate 21 fixed to the rotating frame 2, and then forms moiré fringes after passing through the indicator grating 22, and reaches the photoelectric element 24 through the third lens 23, and the photoelectric element 24 converts the received light signal into an electrical signal, and calculates the rotation angle through the electrical signal, thereby determining the position of the rotating frame 2; wherein, the second reflector 19, the second lens 20, the indicator grating 22, the third lens 23 and the photoelectric element 24 are coaxially mounted on a fixed support, and the second grating plate 21 is fixedly mounted with the rotating frame 2 and rotates with the rotating frame 2; through the control system, the measured real-time angle position is transmitted to the motor drive system, and the motion state and angle of the rotating frame 2 are adjusted in time.

[0062] The circular grating has high accuracy and resolution in static state, and can be used to measure the angle of the rotating frame 2 in static state. When the rotating frame 2 rotates, the real-time angle of the rotating frame 2 can be measured by the photoelectric encoder.

[0063] Preferably, the two measurement methods are used simultaneously to monitor the motion state of the rotating frame and compare them with each other, so as to avoid inaccurate measurements caused by errors of the measuring equipment itself when using a single measurement technology.

[0064] For detailed workflow, see Figure 5 .

[0065] In summary, the medical electron linear accelerator frame structure with high-precision positioning provided by the embodiment of the present invention fully embodies the advantages of simple structure, easy operation and accurate control by adopting the dual-gear drive backlash elimination technology, and ensures that the medical electron linear accelerator is always in a precise positioning state. The two angle measurement technologies are adopted, while giving full play to the advantages of the two technologies in different states. By comparing the two measurement results, it is helpful for the operator to judge whether there is a measurement deviation in the measurement system, and avoid single measurement inaccuracy caused by manufacturing errors or damage and failure of the measurement equipment itself, thereby ensuring that the motion state of the medical electron linear accelerator is always under precise monitoring.

[0066] Compared with the prior art, the motion mechanism of the embodiment of the present invention has more accurate positioning, longer service life of the equipment, more precise measurement, improved stability of the medical electron accelerator, reduced failure risk, and reduced maintenance.

[0067] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A medical electron linear accelerator frame structure with high-precision positioning, characterized in that: The frame structure includes a motion mechanism, a measuring mechanism and a fixed frame; The motion mechanism includes a rotating frame, dual drive motor gears, gear bearings, a radiation head and its support, an electronic portal imaging device support, an image-guided radiotherapy device support and a drag chain; the gear bearings are used to connect the drive motor and the rotating frame, and convert electrical energy into kinetic energy of the rotating frame through the drive motor gear transmission. At the same time, the gear bearings are the load transfer medium between the fixed frame and the rotating frame. The loads generated by the various devices / components on the rotating frame are transferred to the fixed frame through the gear bearings; The rotation of the gear bearing is controlled simultaneously by the upper and lower gears, and each gear and the large gear of the gear bearing form a set of drive units. The two sets of drive units are set by the bias torque established in the electrical control system, so that the drive gear of at least one set of the two drive units is always in meshing state with the tooth surface of the large gear; The measuring mechanism includes a photoelectric encoder and a circular grating; In the moving state, a photoelectric encoder is used to measure the angle; the photoelectric encoder converts the geometric displacement of the rotating frame into a pulse signal through photoelectric conversion, and determines the rotation speed by calculating the number of pulses, and then determines the position of the rotating frame; the rotation direction of the rotating frame is determined by outputting two optical code signals with a phase difference of 90°; in the static state, the circular grating measurement technology is used to measure the angle; the circular grating measurement is based on the Moire fringe principle, and the photoelectric element determines the number of grating pitches moved by reading the number of moving Moire fringes, thereby obtaining the accurate angular displacement of the rotating frame.

2. The high-precision positioning medical electron linear accelerator frame structure according to claim 1, characterized in that: The radiation head and its support, the dose guidance device and its support, the image guidance ray generator and its support, and the image guidance receiver and its support are connected to the rotating frame by welding or bolts; the rotating frame and the gear bearing are connected by bolts, and the rotation of the rotating frame is driven by the drive motor gear meshing with the gear bearing; the stator of the gear bearing is connected to the fixed frame by bolts; the electrical signal cable is coiled on the drag chain through the drag chain, the drag chain and the rotating frame are connected by bolts or welded with support rods, and the drag chain rotates with the rotating frame.

3. The high-precision positioning medical electron linear accelerator frame structure according to claim 1, characterized in that: The measuring mechanism comprises two measuring systems, namely a photoelectric encoder measuring system and a circular grating measuring system; the photoelectric encoder measuring system comprises a light source, a radiator, a lens, a grating plate, a fixed grating and a photosensitive tube; the light source adopts a light emitting diode, which is installed on a fixed support, and converts the light of the light source into parallel light through a reflector and a lens; the parallel light passes through a grating plate fixedly connected to the rotating frame and irradiates the fixed grating, and the light signal received by the photosensitive tube from the fixed grating is converted into an electrical signal, and the angle and rotation direction of the rotating frame are determined by the electrical signal; The circular grating measurement system includes a fixed light source, a second reflector, a second lens, a second grating plate, an indicator grating, a third lens and a photoelectric element. The light emitted by the fixed light source is converted into parallel light by the second reflector and the second lens, passes through the second circular grating plate fixed to the rotating frame, and then forms moiré fringes after passing through the indicator grating, and reaches the photoelectric element through the third lens. The photoelectric element converts the received light signal into an electrical signal, calculates the rotation angle through the electrical signal, and thus determines the position of the rotating frame; Among them, the second reflector, the second lens, the indicator grating, the third lens and the photoelectric element are coaxially mounted on the fixed support, and the second grating plate is fixedly mounted on the rotating frame and rotates with the rotating frame; The measured real-time angle position is transmitted to the motor drive system through the control system to adjust the motion state and angle of the rotating frame in time.

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