Magnetic suspension damping system for mobile C-arm machine and damping control method thereof

Abstract

The invention discloses a magnetic suspension damping system for a mobile C-arm machine and a damping control method of the magnetic suspension damping system, and relates to the technical field of electromagnetic damping. The magnetic suspension damping system is arranged between a machine frame and a base of the movable C-arm machine and used for active damping and comprises a magnetic suspension damping unit, a position sensor and a damping control circuit which are distributed at the bottom of the C-arm machine frame, and the position sensor is used for detecting vibration displacement of the C-arm machine frame in real time. The damping control circuit is used for operating a real-time dynamic algorithm (such as a PID algorithm) to dynamically adjust the current of the electromagnetic coil, and closed-loop control of detection-calculation-adjustment is achieved. According to the non-contact and real-time closed-loop control self-adaptive dynamic damping system provided by the invention, the accuracy and imaging quality of projection data of the mobile C-arm machine can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shock absorption, and in particular to a magnetic suspension shock absorption system for a mobile C-arm machine and a shock absorption control method thereof. Background Art

[0002] A mobile C-arm X-ray machine (also known as a mobile C-arm machine or mobile C-arm) with three-dimensional scanning and interventional functions is a core device for navigation in interventional surgeries such as orthopedics. It collects X-ray projection data and reconstructs three-dimensional images to provide doctors with real-time anatomical structure information - such as the vertebral and screw position information required in orthopedic surgery.

[0003] When the mobile C-arm is frequently moved during surgery (for example, from preoperative scanning to intraoperative navigation) or when the surgical operation is disturbed (such as when the doctor adjusts the patient's position or when the surgical instrument collides), mechanical vibration is likely to occur. The vibration frequency is usually in the range of 10-500Hz, and the vibration displacement is usually in the range of 0.3-1.0mm, leading to the following problems: 1. Projection data offset: Vibration causes the relative position of the C-arm frame and the patient's surgical area to change, and the projection data is offset. The offset error is usually greater than 0.5mm, which seriously affects the accuracy of three-dimensional reconstruction. 2. Image quality degradation: Vibration causes the projection data to be blurred, and the resolution of the three-dimensional reconstructed image is reduced, resulting in an inability to clearly display bone and soft tissue structures. 3. Increased surgical risks: Blurred images make it impossible for doctors to accurately judge the screw insertion position, resulting in a screw dislocation rate of more than 10%, greatly increasing the risk of nerve and vascular damage.

[0004] Accordingly, various vibration reduction designs have been developed for mobile 3D C-arms. Currently, mainstream mobile 3D C-arms generally utilize passive mechanical vibration reduction, which absorbs vibration energy through physical material deformation. Specifically, the core structure of the vibration reduction system typically utilizes rubber damping blocks, installed between the C-arm frame and the base. These blocks absorb low-frequency vibrations through elastic deformation. Furthermore, some high-end equipment (such as the GE OEC 3D) incorporates a superimposed spring structure to form a spring damping system, enhancing its ability to absorb intermittent vibrations. As an example, Chinese patent ZL202420316396.X provides a C-arm X-ray machine shock absorption device and a C-arm X-ray machine, wherein the C-arm X-ray machine shock absorption device includes a first walking bracket, suitable for connection with the main body of the C-arm X-ray machine; a second walking bracket, arranged opposite to the first walking bracket and hinged to the first walking bracket; an energy absorption mechanism, arranged between the first walking bracket and the second walking bracket; the energy absorption mechanism can absorb the vibration energy of the main body and convert it into kinetic energy of the rotation of the second walking bracket, thereby converting the large amplitude vibration of the main body into the small amplitude vibration of the second walking bracket, and finally releasing the vibration energy through the energy storage and release process of the energy absorption mechanism, thereby achieving shock absorption. Specifically, the energy absorption mechanism may include a first elastic member and a second elastic member, and the first elastic member and the second elastic member complete elastic energy absorption by undergoing elastic deformation; at the same time, the energy absorption mechanism also includes a vibration absorbing pad to protect the entire shock absorption device.

[0005] However, both rubber shock absorbers and spring damping systems rely on passive energy dissipation due to material deformation and cannot achieve active shock absorption. They also have the following defects: they usually focus on low-frequency shock absorption and can only cope with low-frequency vibrations of less than 10 Hz (such as inertial vibrations during C-arm movement). They have poor shock absorption effects on high-frequency vibrations of more than 100 Hz (such as collisions of surgical instruments), meaning that they are difficult to cover the entire frequency range of vibration energy. At the same time, there is mechanical wear, as rubber or springs will age and deform after long-term use, resulting in a gradual decrease in the shock absorption effect. Moreover, the response speed is slow, as the deformation of the mechanical shock absorber takes time and cannot offset instantaneous vibrations in real time (such as when a doctor suddenly adjusts the angle of the C-arm).

[0006] Electromagnetic levitation, an active vibration control technology, uses electromagnetic force to achieve contactless coupling between electromagnets and the underlying mechanical structure. This technology offers excellent vibration reduction, active adjustment of stiffness and damping, and adaptability to complex operating environments. Consequently, existing technologies offer magnetic levitation vibration reduction solutions for high-precision equipment, including various magnetic levitation shock mounts and anti-shake devices.

[0007] Based on the current magnetic levitation shock absorption solution, how to combine the shock absorption requirements of mobile C-arm machines to provide a contactless, fast-response, real-time closed-loop control adaptive dynamic shock absorption system is a technical problem that urgently needs to be solved. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings of the prior art by providing a magnetic levitation shock absorption system for a mobile C-arm and a shock absorption control method thereof. The magnetic levitation shock absorption system provided by the present invention is installed between the frame and base of the mobile C-arm for active vibration reduction. It includes magnetic levitation shock absorption units distributed at the four corners of the bottom of the C-arm frame, position sensors, and a shock absorption control circuit. The position sensors are used to detect the vibration displacement of the C-arm frame in real time, and the shock absorption control circuit is used to run a real-time dynamic algorithm (such as a PID algorithm) to dynamically adjust the current of the electromagnetic coil, implementing a closed-loop control method of detection-calculation-adjustment. The frame displacement recovery time can be controlled to less than 15ms. The contactless, real-time closed-loop control adaptive dynamic shock absorption system provided by the present invention can significantly improve the accuracy and imaging quality of projection data from mobile C-arms.

[0009] To achieve the above objectives, the present invention provides the following technical solutions: A magnetic suspension vibration reduction system for a mobile C-arm machine is provided between a frame and a base of the mobile C-arm machine for active vibration reduction. The system comprises: A magnetic levitation damping unit is distributed at the bottom of the C-arm frame. The total load of the magnetic levitation damping unit meets the gravity requirement of the mobile C-arm machine. The magnetic levitation damping unit includes a permanent magnet and an electromagnetic coil. The permanent magnet is arranged at the bottom of the C-arm frame, and the electromagnetic coil is arranged on a base and is coaxially opposite to the permanent magnet. When current is passed through the electromagnetic coil, it can generate a magnetic field in the same direction as the permanent magnet. At this time, a repulsive force is generated between the electromagnetic coil and the permanent magnet to form a suspension gap, so that the C-arm frame is suspended. A position sensor is provided corresponding to the permanent magnet and electromagnetic coil of the magnetic suspension damping unit, and is used to detect the displacement change of the suspension gap in real time to obtain the vibration displacement information of the C-arm frame, and send the detected displacement signal to the damping control circuit; The shock absorption control circuit is used to receive the displacement signal sent by the position sensor, calculate and output the adjustment current according to the displacement signal to control the change of the magnetic field strength of the electromagnetic coil, thereby adjusting the aforementioned repulsive force so that the C-arm frame returns to its initial position.

[0010] Furthermore, the shock absorption control circuit is arranged in a control box of the mobile C-arm machine, and is connected to a main control system of the mobile C-arm machine for linkage control.

[0011] Furthermore, there are four magnetic levitation damping units, one at each of the four corners of the bottom of the C-arm frame; the four electromagnetic coils of the four magnetic levitation damping units are distributed based on an XY rectangular coordinate system, with two of them facing each other to form an X-direction electromagnetic coil pair and a Y-direction electromagnetic coil pair. The X-direction electromagnetic coil pair is used to control the X+ direction and the X-direction, and the Y-direction electromagnetic coil pair is used to control the Y+ direction and the Y-direction. The input current of the X-direction electromagnetic coil pair and / or the Y-direction electromagnetic coil is controlled by the vibration reduction control circuit to stabilize the suspended C-arm frame in a two-dimensional plane position.

[0012] Furthermore, the width ratio or diameter ratio of the cross-sectional dimension of the electromagnetic coil to the cross-sectional dimension of the permanent magnet is 1.05-1.3, so that the magnetic field generated by the electromagnetic coil can cover the area where the permanent magnet is located; The permanent magnet is axially magnetized, and the direction of its magnetic field is consistent with the axis of the electromagnetic coil; The suspension gap between the permanent magnet and the electromagnetic coil is between 2-5 mm.

[0013] Furthermore, the position sensor is a Hall sensor, which is fixedly installed between the electromagnetic coil and the permanent magnet to detect the displacement change of the suspension gap formed therebetween.

[0014] Furthermore, the damping control circuit is configured as follows: Obtain the displacement signal detected by the position sensor, which is the deviation Δx of the current position of the rack relative to the initial position. Calculate the corresponding adjustment current ΔI based on the aforementioned deviation Δx; The current value currently required to be passed into the electromagnetic coil is calculated based on the adjustment current ΔI and the aforementioned initial current I0, so that the aforementioned deviation Δx can be adjusted to 0.

[0015] Furthermore, the damping control circuit adopts PID control algorithm to perform real-time dynamic damping. The formula for calculating the dynamic adjustment current ΔI is as follows: ; Where Δx represents the deviation corresponding to the displacement signal; K p Indicates the proportional coefficient, which is used for fast response; K i Indicates the integral coefficient, which is used to eliminate steady-state error; K d Indicates the differential coefficient, which is used to reduce overshoot; the proportional coefficient K p , integral coefficient K i and differential coefficient K d The value is obtained through debugging.

[0016] The present invention also provides a magnetic suspension damping control method for a mobile C-arm machine, which is used to achieve active damping between a frame and a base of the mobile C-arm machine. The method includes: Vibration detection step: Using position sensors corresponding to the permanent magnets and electromagnetic coils of the magnetic suspension damping unit, the displacement change of the suspension gap is detected in real time to obtain vibration displacement information of the C-arm frame; Shock absorption execution steps: calculate and dynamically output an adjustment current based on the displacement signal detected above, the adjustment current acts on the electromagnetic coil above, controls the change in the magnetic field strength of the electromagnetic coil to adjust the repulsive force between the permanent magnet and the electromagnetic coil above, so that the C-arm frame returns to its initial position.

[0017] Furthermore, in the vibration detection step, the position sensor outputs a corresponding analog signal after detecting the displacement signal; The damping control circuit executes the damping execution steps, including: Signal acquisition: collect analog signals through the ADC interface and convert them into digital quantities; PID calculation: Run the PID algorithm and adjust the current according to the displacement digital value; Current adjustment: The current driver is driven by PWM output to input the adjusted current into the electromagnetic coil; Shock absorption execution: The magnetic field strength of the electromagnetic coil changes, the repulsive force changes, and the C-arm frame is adjusted to the initial position so that the displacement deviation is adjusted to 0.

[0018] Furthermore, the parameters required by the aforementioned PID control algorithm are adjusted through step response testing. The steps are as follows: The proportionality coefficient K p , integral coefficient K i and differential coefficient K d The value of is assigned to 0; Get the user's proportional coefficient K p Configure the initial parameter values, give the rack a sudden upward displacement, and monitor its return to the initial position; When the displacement recovery time does not reach the preset time threshold requirement, it is judged that the response is slow and the proportional coefficient K is increased based on the aforementioned initial parameter value. p to speed up the response; When the displacement recovery time meets the preset time threshold requirement, continue to determine whether there is overshoot, that is, the deviation of the rack displacement from the initial position exceeds the preset distance; When it is determined that there is overshoot, increase the differential coefficient K d to reduce the overshoot until the overshoot meets the preset requirements; In the differential coefficient K d After debugging, set the integral coefficient K i to eliminate steady-state errors.

[0019] Based on existing magnetic levitation technology, this invention provides a contactless, highly responsive, and long-life adaptive dynamic vibration reduction solution for mobile C-arms. Compared to existing technologies, this invention offers the following advantages and positive effects: The magnetic levitation vibration reduction system provided by this invention is installed between the frame and base of a mobile C-arm for active vibration reduction. It comprises magnetic levitation vibration reduction units located at the four corners of the C-arm frame, position sensors, and a vibration reduction control circuit. The position sensors detect the vibration displacement of the C-arm frame in real time, and the vibration reduction control circuit runs a real-time dynamic algorithm (such as a PID algorithm) to dynamically adjust the current in the electromagnetic coil, achieving closed-loop control based on detection, calculation, and adjustment. This allows for frame displacement recovery time to be controlled to under 15ms. This contactless, real-time, closed-loop adaptive dynamic vibration reduction system can significantly improve the accuracy and imaging quality of projection data from mobile C-arms. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the module structure of the magnetic suspension shock absorption system for mobile C-arm machine provided by the embodiment of the present invention Figure 1 .

[0021] Figure 2 This is a schematic diagram of the arrangement of four magnetic levitation shock absorption units in the magnetic levitation shock absorption system provided in an embodiment of the present invention.

[0022] Figure 3 Schematic diagram of the module structure of the magnetic suspension shock absorption system for mobile C-arm machine provided by the embodiment of the present invention Figure 2 .

[0023] Figure 4 This is a flow chart of the magnetic levitation shock absorption control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following is a further detailed description of the magnetic levitation shock absorption system for a mobile C-arm machine and its shock absorption control method disclosed in the present invention, in conjunction with the accompanying drawings and specific embodiments. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated, and they can be combined with each other to achieve better technical effects. In the drawings of the following embodiments, the same reference numerals appearing in each drawing represent the same features or components, which can be applied to different embodiments. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0025] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not intended to limit the conditions under which the invention can be implemented. Any structural modification, change in proportional relationship, or adjustment of size should fall within the scope of the technical content disclosed in the invention without affecting the efficacy and purpose of the invention. The scope of the preferred embodiments of the present invention includes alternative implementations, in which the functions can be performed in a non-described or discussed order, including performing the functions in a substantially simultaneous manner or in a reverse order according to the functions involved, which should be understood by those skilled in the art of the art to which the embodiments of the present invention belong.

[0026] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values. Example

[0027] The magnetic suspension shock absorption system provided by the present invention is arranged between the frame and the base of the mobile C-arm machine to perform active shock absorption and offset vibration.

[0028] Magnetic levitation, or magnetic suspension, is a method of floating an object in midair using the attraction and repulsion of magnets, independent of external forces. Modern magnetic levitation control methods include analog circuit control and single-chip microcomputer control, with both pull-up and push-down suspension types. The magnetic levitation shock absorption system of the present invention utilizes a push-down magnetic levitation scheme controlled by a single-chip microcomputer. Its principle is to maintain stability using magnets with opposite polarity. A large magnet is placed below the float. The magnetic force between the magnet and the float (both of which have the same polarity) lifts the float, creating a delicate equilibrium point. Because this equilibrium point has weak resistance to interference, an electromagnetic coil is introduced.

[0029] Specifically, the magnetic levitation shock absorption system includes a magnetic levitation shock absorption unit, a position sensor and a shock absorption control circuit.

[0030] The magnetic levitation damping units are located at the four corners of the C-arm frame. The total load of the magnetic levitation damping units meets the weight requirements of the mobile C-arm. By way of example and not limitation, for example, four magnetic levitation damping units are evenly distributed at the bottom of the C-arm frame to support it. Each magnetic levitation damping unit has a load capacity of greater than or equal to 50 kg, and the total load capacity is greater than or equal to 200 kg, meeting the weight requirements of the mobile C-arm.

[0031] The magnetic levitation damping unit can include a permanent magnet and an electromagnetic coil. The permanent magnet is fixedly mounted on the bottom of the C-arm frame, and the electromagnetic coil is fixedly mounted on a base and arranged coaxially with the permanent magnet. When current is passed through the electromagnetic coil, it generates a magnetic field in the same direction as the permanent magnet. At this time, a repulsive force is generated between the electromagnetic coil and the permanent magnet, forming a suspension gap, achieving and maintaining the levitation state of the C-arm frame.

[0032] In this embodiment, the width ratio or diameter ratio of the cross-sectional dimensions of the electromagnetic coil to the cross-sectional dimensions of the permanent magnet is 1.05-1.3, so that the magnetic field generated by the electromagnetic coil can cover the area where the permanent magnet is located, thereby improving the efficiency of the repulsive force. Preferably, the cross-sectional dimensions of the electromagnetic coil and the cross-sectional dimensions of the permanent magnet are circular, and the diameter ratio is 1.2.

[0033] The permanent magnet is axially magnetized, and the direction of its magnetic field is consistent with the axis of the electromagnetic coil, thereby maximizing the repulsive force.

[0034] The suspension gap between the permanent magnet and the electromagnetic coil is between 2-5 mm, and the permanent magnet and the electromagnetic coil are non-contact, thus avoiding contact wear.

[0035] By way of example, and not limitation, the electromagnetic coil can be made of copper enameled wire, which offers excellent conductivity and rapid heat dissipation. The coil is designed to have 1000 turns, with a wire diameter of preferably 0.5 mm. The coil dimensions are φ60 mm (cross-sectional outer diameter) x 20 mm (length), matching the dimensions of the permanent magnet. The coil resistance is approximately 5 Ω, and when the current is 1-5 A, the power is ≤ 25 W to avoid overheating.

[0036] The permanent magnet can be made of neodymium iron boron, such as N35, which provides a high magnetic field strength. The permanent magnet measures φ50 mm (diameter) x 30 mm (length) and is coaxially mounted with the electromagnetic coil. The magnetic field strength is approximately 1.2 T, which, in conjunction with the electromagnetic coil, generates sufficient repulsive force.

[0037] The levitation and vibration reduction of the magnetic suspension damping unit is achieved based on the repulsive force between the permanent magnet and the electromagnetic coil. When the electromagnetic coil is energized, the coil generates a magnetic field in the same direction as the permanent magnet, generating a repulsive force F between the two.

[0038] The calculation formula of the repulsive force F is as follows: ; Where μ0 represents the vacuum magnetic permeability, which is taken as ; N is the number of turns of the electromagnetic coil; I is the current of the electromagnetic coil, the unit is A; A is the area of ​​the electromagnetic coil, the unit is m 2 ; d represents the suspension gap, in m.

[0039] The corresponding magnetic field repulsion force and closed-loop control mechanism are as follows: when the C-arm gantry displaces downward due to vibration, the suspension gap d decreases, the repulsive force F increases, and the C-arm gantry is pushed upward by the repulsive force, d increases, and the C-arm gantry returns to its initial position. When the gantry displaces upward due to vibration, the suspension gap d increases, the repulsive force F decreases, and at this time, the C-arm gantry moves downward under the action of gravity, d decreases, and the C-arm gantry returns to its initial position.

[0040] As a preferred typical embodiment, there are four magnetic levitation damping units, one at each of the four corners of the C-arm gantry's bottom. The four electromagnetic coils of these units are arranged according to an XY rectangular coordinate system, with pairs of them forming X-direction electromagnetic coil pairs and Y-direction electromagnetic coil pairs. The X-direction electromagnetic coil pair controls the X+ direction (positive X-axis direction) and the X-direction (negative X-axis direction), while the Y-direction electromagnetic coil pair controls the Y+ direction (positive Y-axis direction) and the Y-direction (negative Y-axis direction). In other words, two electromagnetic coils arranged 180 degrees apart control the X+ and X-directions, while another two electromagnetic coils arranged 180 degrees apart control the Y+ and Y-directions. The electromagnetic coils exert repulsion or attraction on the deflected C-arm gantry above, stabilizing the C-arm gantry in a two-dimensional plane and allowing it to return to a balance point after deflection, thereby achieving magnetic levitation stability control.

[0041] The position sensor is arranged corresponding to the permanent magnet and electromagnetic coil of the magnetic levitation shock absorption unit, and is used to detect the displacement change of the suspension gap in real time to obtain the vibration displacement information of the C-arm frame - including the offset information in the up and down and left and right directions, and send the detected displacement signal to the shock absorption control circuit.

[0042] In specific settings, the position sensor can be set between the four magnetic suspension damping units, see Figure 1 and Figure 2 As shown, at this time, the position sensor can be used to detect the displacement signal of the suspension gap of each magnetic suspension damping unit in real time, thereby obtaining the vibration displacement information of the C-arm frame.

[0043] A position sensor can also be provided between the permanent magnet and the electromagnetic coil of the magnetic suspension damping unit, see Figure 3 As shown, the position sensor detects the displacement change of the suspension gap of the corresponding magnetic suspension damping unit in real time, thereby obtaining the vibration displacement information of the C-arm frame.

[0044] Preferably, the position sensor is a Hall effect sensor, fixedly mounted between multiple electromagnetic coils and a permanent magnet, to detect changes in the suspension gap formed therebetween. Specifically, the Hall effect sensor can be an A3144 sensor, which offers a detection accuracy of 0.01mm and can detect suspension gap changes in real time. Its response time is less than 1ms, making it resistant to high-frequency vibrations.

[0045] The damping control circuit is used to receive the displacement signal sent by the position sensor, calculate and output an adjustment current based on the displacement signal to control the change in the magnetic field strength of the electromagnetic coil, thereby adjusting the aforementioned repulsive force and increasing the speed at which the C-arm frame returns to its initial position, that is, reducing the displacement recovery time.

[0046] Preferably, the shock absorption control circuit is directly arranged in the control box of the mobile C-arm machine, and is connected to the main control system of the mobile C-arm machine for linkage control.

[0047] In this embodiment, the damping control circuit is configured to: obtain a displacement signal detected by a position sensor, where the displacement signal is a deviation Δx of the current position of the frame relative to the initial position, which is also a change in the suspension gap; calculate a corresponding adjustment current ΔI based on the aforementioned deviation Δx; and calculate a current value that needs to be passed into the electromagnetic coil based on the adjustment current ΔI and the aforementioned initial current I0 so that the aforementioned deviation Δx can be adjusted to 0.

[0048] Specifically, the vibration reduction control circuit may include a main control chip module, an interface module, a PWM (pulse width modulation) module, and a UART (serial communication) module. To achieve real-time dynamic vibration reduction, a PID (proportional-integral-differential) control algorithm is used to calculate the adjustment current ΔI based on the displacement signal Δx detected by the position sensor (i.e., the deviation between the actual rack position and the initial position). The formula is as follows: ; Wherein, Δx represents the deviation corresponding to the displacement signal.

[0049] K p Represents the proportional coefficient, which is used to ensure fast response. The larger the displacement, the larger the current adjustment value, and the faster the adjustment (change) of the repulsive force needs to be.

[0050] K i represents the integral coefficient, which is used to eliminate steady-state errors. If the displacement persists, the current is gradually adjusted by accumulating the integral term until the displacement is zero.

[0051] K d The differential coefficient is used to reduce overshoot. It is used to adjust the current in advance according to the displacement change rate to prevent the rack from oscillating back and forth.

[0052] In specific implementation, debugging can be performed through a step response test (giving the rack a sudden upward displacement and observing the process of it returning to the initial position) to obtain the parameter values ​​required by the aforementioned PID control algorithm.

[0053] The specific steps for debugging parameters are as follows: Set the proportional coefficient K p , integral coefficient K i and differential coefficient K d Assign the value of 0; obtain the user's proportional coefficient K p Configure the initial parameter value, give the rack a sudden upward displacement, and monitor its return to the initial position; when the displacement recovery time does not reach the preset time threshold requirement (for example, 20ms), it is judged that the response is slow, and the proportional coefficient K is increased based on the aforementioned initial parameter value p to speed up the response; when the displacement recovery time meets the preset time threshold requirement, continue to judge whether there is overshoot, that is, the deviation between the displacement of the rack and the initial position exceeds the preset distance; when it is determined that there is overshoot, increase the differential coefficient K d The value of K is used to reduce the overshoot until the overshoot meets the preset requirements; d After debugging, set the integral coefficient K i to eliminate steady-state errors.

[0054] As an example and not limitation, for example, the initial K p =0.3, the detected displacement recovery time is greater than the preset time threshold requirement. For example, if the displacement recovery time is 50ms, which is greater than the preset time threshold of 20ms, it is judged that the response is slow and K needs to be increased. p Based on this, we can make K p =0.5 to speed up the response. If the detected displacement recovery time is less than 20ms, which meets the response requirements, continue to determine whether there is overshoot. If there is overshoot, such as the deviation from the initial position exceeds 0.1mm, the differential coefficient K can be increased. d To reduce the overshoot, adjust the value until the overshoot meets the preset requirements. For example, increase K d The value of K d =0.05, then the overshoot disappears and the displacement recovery time is less than 20ms (for example, the recovery time is less than 15ms). d After debugging, set the integral coefficient K i To eliminate the steady-state error, let K i =0.1 to eliminate the steady-state error. After the parameter values ​​are debugged, adjust the input current of the electromagnetic coil according to the adjustment current calculation formula until the displacement finally returns to 0.

[0055] That is, the proportional coefficient K obtained after debugging p , integral coefficient K iand differential coefficient K d The values ​​of are 0.5, 0.1 and 0.05 respectively.

[0056] In this embodiment, the main control chip module can use an STM32F407 chip, which has a 32-bit ARM Cortex-M4 core and a processing speed of 168MHz, which is sufficient to run the PID algorithm. The interface includes an ADC for acquiring analog signals from the position sensor. The PWM module is used to control the current of the electromagnetic coil. The UART module is used to communicate with the C-arm main control system.

[0057] The closed-loop control workflow mainly includes five steps, as follows: Vibration detection: The position sensor (Hall sensor) detects the displacement Δx of the C-arm frame in real time, such as the offset in the up and down directions, and outputs an analog signal (0-3.3V, corresponding to a displacement of 0-5mm).

[0058] Signal acquisition: The vibration reduction control circuit collects analog signals through the ADC interface and converts them into digital quantities (12 bits, accuracy 0.0008mm).

[0059] PID calculation: The control circuit runs the PID algorithm and adjusts the current ΔI based on the displacement digital value.

[0060] Current regulation: The control circuit drives the current driver (L298N) through PWM output (e.g., 10kHz frequency), which inputs the regulated current into the electromagnetic coil. The diversion current I = I0 + ΔI, where I0 is the initial current, approximately 2A.

[0061] Shock absorption execution: The magnetic field strength of the electromagnetic coil changes, the repulsive force changes, and the C-arm frame is pulled back to the initial position, that is, Δx is adjusted to 0.

[0062] The total adjustment time for executing the above steps can be reduced to less than 10ms, meeting the shock absorption requirements of high-frequency vibrations.

[0063] The technical solution provided by the present invention features a contactless coaxial design for the magnetic levitation damping unit (a permanent magnet is fixed to the bottom of the C-arm frame, and an electromagnetic coil is fixed to the base, with their axes aligned). This allows for a controlled suspension gap of 2-5mm, eliminating the mechanical wear associated with mechanical dampers (such as rubber or springs), extending the service life to five years or more. Furthermore, the four-unit redundant design enhances the reliability of the damping system. Four magnetic levitation damping units are located at the four corners of the C-arm frame, each operating independently. Even if one unit fails, the remaining three maintain vibration transmissibility, ensuring the proper operation of the mobile C-arm.

[0064] On the other hand, a real-time closed-loop PID control active vibration reduction method has been proposed. This method uses a position sensor (Hall sensor, response time <1ms) to detect the C-arm gantry's vibration displacement (such as the vertical offset Δx) in real time. The control circuit runs a PID algorithm and dynamically adjusts the current of the electromagnetic coil, achieving a closed-loop control of detection-calculation-adjustment. This method can keep the gantry displacement recovery time below 15ms. Furthermore, for high-frequency vibrations (10-500Hz) such as those caused by surgical instrument collisions and the doctor adjusting the C-arm angle, the combination of the high response speed of the position sensor and the rapid adjustment of the PID algorithm (adjustment time can reach less than 10ms) enables adaptive processing of high-frequency vibrations. This solution can accurately offset small displacements (0.1-0.5mm), keeping projection data offsets below 0.05mm and maintaining imaging resolution above 2.3lp / mm, significantly improving imaging resolution.

[0065] Another embodiment of the present invention further provides a magnetic levitation vibration reduction control method for a mobile C-arm machine, which is used to achieve active vibration reduction between the frame and base of the mobile C-arm machine.

[0066] See also Figure 4 As shown, the method includes the following steps: S100, vibration detection step: using position sensors provided corresponding to the permanent magnets and electromagnetic coils of the magnetic suspension damping unit, the displacement change of the suspension gap is detected in real time to obtain vibration displacement information of the C-arm frame.

[0067] S200, shock absorption execution step: calculating and dynamically outputting an adjustment current based on the aforementioned detected displacement signal, wherein the adjustment current acts on the aforementioned electromagnetic coil to control the change in the magnetic field strength of the electromagnetic coil to adjust the repulsive force between the aforementioned permanent magnet and the electromagnetic coil, so that the C-arm frame returns to its initial position.

[0068] In this embodiment, in the vibration detection step, the position sensor outputs a corresponding analog signal after detecting the displacement signal.

[0069] Furthermore, the aforementioned damping execution steps are executed by the damping control circuit, specifically as follows: S210, signal acquisition: collect analog signals through the ADC interface and convert them into digital quantities.

[0070] S220, PID calculation: Run the PID algorithm and adjust the current based on the displacement digital value.

[0071] S230, current adjustment: driving the current driver through PWM output to input the adjusted current into the electromagnetic coil.

[0072] S240, shock absorption execution: the magnetic field strength of the electromagnetic coil changes, the repulsive force changes, and the C-arm frame is adjusted to the initial position so that the displacement deviation is adjusted to 0.

[0073] In this embodiment, the parameters required by the PID control algorithm are adjusted through step response test. The specific steps are as follows: p , integral coefficient K i and differential coefficient K d Assign the value of 0; obtain the user's proportional coefficient K p Configure the initial parameter value, give the rack a sudden upward displacement, and monitor its return to the initial position; when the displacement recovery time does not reach the preset time threshold requirement (for example, 50ms), it is judged that the response is slow, and the proportional coefficient K is increased based on the aforementioned initial parameter value p to speed up the response; when the displacement recovery time meets the preset time threshold requirement, continue to judge whether there is overshoot, that is, the deviation between the displacement of the rack and the initial position exceeds the preset distance; when it is determined that there is overshoot, increase the differential coefficient K d The value of K is used to reduce the overshoot until the overshoot meets the preset requirements; d After debugging, set the integral coefficient K i to eliminate steady-state errors.

[0074] Other technical features are described in the previous embodiments and will not be repeated here.

[0075] In the above description, the disclosure of the present invention is not intended to limit itself to these aspects. Rather, within the scope of the intended protection of the present disclosure, the components can be selectively and operationally combined in any number. In addition, terms such as "including", "encompassing" and "having" should be interpreted as inclusive or open by default, rather than exclusive or closed, unless they are explicitly defined to the contrary. All technical, scientific or other terms have the meaning understood by those skilled in the art unless they are defined to the contrary. Common terms found in dictionaries should not be interpreted too idealistically or too impractically in the context of relevant technical documents, unless the present disclosure explicitly defines them as such. Any changes and modifications made by a person of ordinary skill in the field of the present invention based on the above disclosure are within the scope of protection of the claims.

Claims

1. A magnetic suspension shock absorption system for a mobile C-arm machine, which is arranged between the frame and the base of the mobile C-arm machine for active shock absorption, characterized in that include: The magnetic suspension shock absorption unit is distributed at the bottom of the C-arm frame. The total load of the magnetic suspension shock absorption unit meets the gravity requirements of the mobile C-arm machine; The magnetic suspension damping unit includes a permanent magnet and an electromagnetic coil. The permanent magnet is arranged at the bottom of the C-arm frame, and the electromagnetic coil is arranged on the base and is coaxially opposite to the permanent magnet. When current is passed through the electromagnetic coil, it can generate a magnetic field in the same direction as the permanent magnet. At this time, a repulsive force is generated between the electromagnetic coil and the permanent magnet to form a suspension gap, so that the C-arm frame is suspended. A position sensor is provided corresponding to the permanent magnet and electromagnetic coil of the magnetic suspension damping unit, and is used to detect the displacement change of the suspension gap in real time to obtain the vibration displacement information of the C-arm frame, and send the detected displacement signal to the damping control circuit; The shock absorption control circuit is used to receive the displacement signal sent by the position sensor, calculate and output the adjustment current according to the displacement signal to control the change of the magnetic field strength of the electromagnetic coil, thereby adjusting the aforementioned repulsive force so that the C-arm frame returns to its initial position.

2. The system according to claim 1, wherein: The shock absorption control circuit is arranged in a control box of the mobile C-arm machine, and is connected to a main control system of the mobile C-arm machine for linkage control.

3. The system according to claim 1, wherein: There are four magnetic levitation shock absorption units, one at each of the four corners of the bottom of the C-arm frame; the four electromagnetic coils of the four magnetic levitation shock absorption units are distributed based on the XY rectangular coordinate system, with two pairs of them facing each other to form an X-direction electromagnetic coil pair and a Y-direction electromagnetic coil pair. The X-direction electromagnetic coil pair is used to control the X+ direction and the X-direction, and the Y-direction electromagnetic coil pair is used to control the Y+ direction and the Y-direction; The input current of the X-direction electromagnetic coil pair and / or the Y-direction electromagnetic coil is controlled by the vibration reduction control circuit to stabilize the suspended C-arm frame in a two-dimensional plane position.

4. The system according to claim 1, wherein: The width ratio or diameter ratio of the cross-sectional dimension of the electromagnetic coil to the cross-sectional dimension of the permanent magnet is 1.05-1.3, so that the magnetic field generated by the electromagnetic coil can cover the area where the permanent magnet is located; The permanent magnet is axially magnetized, and the direction of its magnetic field is consistent with the axis of the electromagnetic coil; The suspension gap between the permanent magnet and the electromagnetic coil is between 2-5 mm.

5. The system according to claim 1, wherein: The position sensor is a Hall sensor, which is fixedly installed between the electromagnetic coil and the permanent magnet and is used to detect the displacement change of the suspension gap formed between the two.

6. The system according to any one of claims 1 to 5, characterized in that The damping control circuit is configured to: Obtain the displacement signal detected by the position sensor, which is the deviation Δx of the current position of the rack relative to the initial position. Calculate the corresponding adjustment current ΔI based on the aforementioned deviation Δx; According to the adjustment current ΔI and the aforementioned initial current I0, the current value that needs to be passed into the electromagnetic coil is calculated so that the aforementioned deviation Δx can be adjusted to zero.

7. The system according to claim 6, characterized in that The damping control circuit adopts PID control algorithm to perform real-time dynamic damping. The formula for calculating the dynamic adjustment current ΔI is as follows: ； Where Δx represents the deviation corresponding to the displacement signal; K p Indicates the proportional coefficient, which is used for fast response; K i Indicates the integral coefficient, which is used to eliminate steady-state error; K d Indicates the differential coefficient, which is used to reduce overshoot; the proportional coefficient K p , integral coefficient K i and differential coefficient K d The value is obtained through debugging.

8. A magnetic suspension damping control method for a mobile C-arm machine, for achieving active damping between the frame and base of the mobile C-arm machine, characterized in that include, Vibration detection step: Using position sensors corresponding to the permanent magnets and electromagnetic coils of the magnetic suspension damping unit, the displacement change of the suspension gap is detected in real time to obtain vibration displacement information of the C-arm frame; Shock absorption execution steps: calculate and dynamically output an adjustment current based on the displacement signal detected above, the adjustment current acts on the electromagnetic coil above, controls the change in the magnetic field strength of the electromagnetic coil to adjust the repulsive force between the permanent magnet and the electromagnetic coil above, so that the C-arm frame returns to its initial position.

9. The method according to claim 8, characterized in that In the vibration detection step, the position sensor outputs a corresponding analog signal after detecting the displacement signal; The damping control circuit executes the damping execution steps, including: Signal acquisition: collect analog signals through the ADC interface and convert them into digital quantities; PID calculation: Run the PID algorithm and adjust the current according to the displacement digital value; Current adjustment: The current driver is driven by PWM output to input the adjusted current into the electromagnetic coil; Shock absorption execution: The magnetic field strength of the electromagnetic coil changes, the repulsive force changes, and the C-arm frame is adjusted to the initial position so that the displacement deviation is adjusted to 0.

10. The method according to claim 9, characterized in that Adjust the parameters required by the aforementioned PID control algorithm through step response testing. The steps are as follows: The proportionality coefficient K p , integral coefficient K i and differential coefficient K d The value of is assigned to 0; Get the user's proportional coefficient K p Configure the initial parameter values, give the rack a sudden upward displacement, and monitor its return to the initial position; When the displacement recovery time does not reach the preset time threshold requirement, the response is judged to be slow, and the proportional coefficient is increased based on the aforementioned initial parameter value. K p to speed up the response; When the displacement recovery time meets the preset time threshold requirement, continue to determine whether there is overshoot, that is, the deviation of the rack displacement from the initial position exceeds the preset distance; When it is determined that there is overshoot, increase the differential coefficient K d to reduce the overshoot until the overshoot meets the preset requirements; In the differential coefficient K d After debugging, set the integral coefficient K i to eliminate steady-state errors.

Images