Uniaxial Harmonic Absorber for Cantilever Structure

Abstract

The system includes a cantilever structure and a harmonic absorber. The cantilever structure is anchored at an anchoring end and is connected at a distal end to the device. The use of the device imparts vibrations in the cantilever structure. The harmonic absorber is located at the distal end of the cantilever structure. The harmonic absorber is tuned to the structural frequency of the cantilever structure so as to damp the vibrations in the cantilever structure.

Description

Technical Field

[0001] The present invention generally relates to a uniaxial harmonic absorber for a cantilever structure. The harmonic absorber can be used, for example, to damp the vibrations of the structure caused by using a device connected to the cantilever structure. Background Art

[0002] Imaging scanners such as single photon emission computed tomography (SPECT) have a cantilever gantry display monitor assembly anchored at the top of the scanner. The cantilever gantry display monitor assembly holds a touch screen display that allows a user to interact with the scanner during scanner operation. However, user interactions with the touch screen display and other system movements cause long-term oscillations in the cantilever gantry display monitor assembly. In turn, these oscillations make it difficult to read and operate the touch screen display.

[0003] Conventional solutions to vibrations in cantilever structures on medical systems have mainly been addressed by changing the cross-sectional geometry of the cantilever or a supplementary gusset plate. These solutions only change the rigidity of the structure that only affects the nature of the vibration and do not cancel its propagation. Summary of the Invention

[0004] Embodiments of the present invention solve and overcome one or more of the above-mentioned deficiencies and drawbacks by providing methods, systems, and devices related to a uniaxial harmonic absorber for reducing vibrations in a cantilever structure.

[0005] According to some embodiments, the system includes a cantilever structure and a harmonic absorber. The cantilever structure is anchored at an anchor end and is connected to a device at a distal end. The use of the device imparts vibrations in the cantilever structure. The harmonic absorber is located at the distal end of the cantilever structure. The harmonic absorber is tuned to the structural frequency of the cantilever structure so as to damp the vibrations in the cantilever structure.

[0006] In other embodiments of the present invention, a system for damping vibrations in a cantilever structure includes a uniaxial harmonic absorber. The uniaxial harmonic absorber is positioned inside the cantilever structure and includes a mass block, a spring, and a guide rod for positioning the mass block relative to the center of the spring. The axial harmonic absorber is tuned to the structural frequency of the tubular cantilever structure so as to damp the vibrations in the tubular cantilever structure.

[0007] In other embodiments, the system includes an imaging device, a cantilever structure anchored to the imaging device, and a harmonic absorber connected to the cantilever structure. The harmonic absorber is tuned to the structural frequency of the cantilever structure so as to damp the vibrations in the cantilever structure.

[0008] Other features and advantages of the present invention become apparent from the following detailed description of illustrative embodiments to be taken in conjunction with the accompanying drawings. Brief Description of the Drawings

[0009] The foregoing and other aspects of the present invention are best understood from the following detailed description when read in conjunction with the accompanying drawings. For the purpose of illustrating the present invention, the presently preferred embodiments are shown in the drawings, but it should be understood that the invention is not limited to the specific means disclosed. The following drawings are included:

[0010] Figure 1 A conceptual view of how a harmonic absorber can reduce vibrations in a cantilever structure is provided;

[0011] Figure 2A An example cantilever structure anchored to an imaging system according to some embodiments is shown;

[0012] Figure 2B Provided is Figure 2A A more detailed view of the cantilever structure shown in

[0013] Figure 2C Illustrated is how Figure 1 Regarding the vibration characteristics described Figure 2A and Figure 2B are applied to the example cantilever structure shown in

[0014] Figure 3 A detailed internal view of the distal end of the cantilever structure shown in Figures 2A-2C according to some embodiments is provided; and

[0015] Figure 4 A mathematical model showing the displacement of the entire assembly as a function of time is shown. DETAILED DESCRIPTION

[0016] The following disclosure describes the present invention in accordance with various embodiments related to methods, systems, and devices for harmonic absorbers for cantilever structures. As generally understood in the art, mechanical structures inherently have mass, stiffness, and damping that can be calculated and / or measured to arrive at the natural frequency of an object. According to various embodiments described in detail below, a harmonic absorber (also referred to as a tuned mass damper) is integrated into a cantilever structure. In some embodiments, this harmonic absorber includes a mass block and a spring pair having a precise ratio of mass to stiffness that cancels out the frequency of the structure and thus reduces or eliminates vibrations in the structure. In other embodiments, other types of harmonic absorbers (e.g., the volume of liquid contained) may be used. In systems where the cantilever structure is connected to a user interface, the harmonic absorber reduces or eliminates vibrations in the interface, thereby improving the ergonomics and usability of the entire system.

[0017] Figure 1A conceptual view of how a harmonic absorber can reduce vibrations in a cantilever structure is provided. In this example, there are two spring-mass-damper systems. The first spring-mass-damper system is characterized by a mass m 1 , a stiffness k 1 , and a damping coefficient c 1 , while the second spring-mass-damper system is characterized by a mass m 2 , a stiffness k 2 , and a damping coefficient c 2 . The second spring-mass-damper system is herein referred to as a "tuned mass damper" or "harmonic absorber". The values of m 2 , k 2 , and c 2 are selected or "tuned" to cancel a specific resonance frequency of the mechanical vibrations that would occur in the first spring-mass-damper system. In the absence of the harmonic absorber, a force F(t) that displaces the first spring-mass-damper system will cause the first spring-mass-damper system to vibrate until the energy is completely dissipated. However, with the use of the harmonic absorber, these vibrations can be minimized or completely eliminated.

[0018] Continuing to refer to Figure 1 , the first spring-mass-damper system can be analogized to a cantilever structure. As understood in the art, a cantilever structure is a rigid structural element that is anchored to a support at one end. The natural frequency of a cantilever structure will depend on various factors such as the dimensions of the structure, the modulus of stiffness of the material used to construct the structure, the moment of inertia of the cross-section of the structure, etc. If a force is applied to the cantilever structure, the structure will attempt to vibrate at this frequency until the energy is dissipated. The harmonic absorber described herein acts in a manner similar to the harmonic absorber described above. That is, the harmonic absorber is tuned to the natural frequency of the cantilever structure so as to reduce or eliminate vibrations.

[0019] Figure 2A An example cantilever structure 200 anchored to an imaging system 202 is shown in accordance with some embodiments. In this example, the imaging system 202 is a single photon emission computed tomography (SPECT) system; however, it should be understood that any imaging system known in the art can be used for the cantilever structure 200, including but not limited to MRI, computed tomography (CT), and positron emission tomography (PET) imaging systems. As shown in the figure, a monitor assembly 225 is attached to the cantilever structure 200. During imaging, a subject is positioned on a bed 201. The bed 201 is then moved into the imaging system 202. An operator uses the monitor assembly 225 to input commands for performing imaging operations (e.g., start imaging, select imaging parameters, etc.).

[0020] Figure 2B There is providedFigure 2A A more detailed view of the cantilever structure 200 shown in. The anchoring section 205 is located at the anchoring end 203 of the cantilever structure 200 and extends in the vertical direction relative to the imaging system 202 (shown in Figure 2A ). This anchoring section is connected to the upper outer surface of the imaging system 202 at the anchoring point 230. The monitor assembly 225 is located at the distal end 213 of the cantilever structure 200. The user can rotate the cantilever structure 200 about the anchoring point 230 to position the monitor assembly 225 as needed during the operation of the imaging system 202.

[0021] Continuing to refer to Figure 2B , the horizontal section 210 is connected to the anchoring section 205 to allow the cantilever structure 200 to extend away from the imaging system 202 for easy access. The curved boom section 215 is connected to the horizontal section 210 and is located at the distal end 213 of the cantilever structure 200. The harmonic absorber 220 is positioned inside (i.e., within) the curved boom section 215.

[0022] Figure 2C Illustrated how these vibration characteristics described above are applied to the exemplary cantilever structure 200. Here, the vibration characteristics of the cantilever structure 200 (labeled as m Figure 1 , k 1 , c 1 ) are shown in the horizontal section 210. The vibration characteristics of the harmonic absorber 220 (labeled as m 1 , k 2 , c 2 ) are tuned to cancel the vibration characteristics of the cantilever structure 200 and thus reduce the amplitude and duration of the mechanical vibrations in the structure 200. More specifically, the values of m 2 and k 2 are selected such that the moving part of the harmonic absorber 220 (see the internal view in 2 , Figure 3 ) is tuned to a specific structural frequency of the cantilever structure 200. For example, in one embodiment, the harmonic absorber 220 is tuned to the first natural frequency of the cantilever structure. When a particular frequency is excited, the harmonic absorber 220 will produce a resonance out of phase with the structural motion, thereby canceling the vibrations in the cantilever structure 200.

[0023] It should be noted that the harmonic absorber can be easily tuned for changes between and within imaging systems. The techniques for tuning the harmonic absorber are generally well known in the art and are not specifically described herein. Generally speaking, the techniques for tuning will depend on the type of harmonic absorber used. For example, for a mass - spring harmonic absorber (see below Figure 3 ​), which can perform tuning by monitoring vibrations in the cantilever structure 200 while adjusting the characteristics of the mass and / or spring (e.g., wire diameter, outer diameter, length, and total number of coils).

[0024] Figure 3 A specific internal view of the distal end of the cantilever structure 200 according to some embodiments is provided. In such an example, the harmonic absorber 220 includes a mass 315 and a spring 320. The guide rod 325 positions the mass 315 relative to the spring 320. The harmonic absorber 220 is inside the curved boom section 215 and the hub 305, and the hub 305 is connected to the curved boom section 215 using a nut adapter 310. The hub 305 includes a knuckle adapter 330 that is connected to a knuckle ball joint 335 on the housing 340 of the monitor assembly 225. The two-piece harmonic absorber 220 (i.e., the mass and the spring) provides a simple modular solution that can be located inside the cantilever structure 200. Thus, it is possible to easily add vibration damping to an existing cantilever structure without substantial modification to its design. In other embodiments, all or part of the harmonic absorber 220 may be located outside and connected to the cantilever structure 200 (such as the curved boom section 215).

[0025] Figure 4 A mathematical model of the displacement of the entire assembly versus time is shown. The figure also shows the displacement envelope of the cantilever assembly without the harmonic damper. As Figure 4 shown, precisely tuning the harmonic absorber (adjusting the mass and stiffness) significantly reduces the amplitude and duration of the structural vibrations. Thus, the vibrations of the monitor assembly are significantly reduced and the user experience is improved.

[0026] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, and their true scope and spirit are indicated by the appended claims.

[0027] The systems and processes of the figures are not exclusive. Other systems and designs can be derived in accordance with the principles of the present invention to achieve the same objectives. Although the present invention has been described with reference to specific embodiments, it should be understood that the embodiments and variations shown and described herein are for illustrative purposes only. Various modifications to the current design can be made by those skilled in the art without departing from the scope of the present invention. None of the claim elements herein are to be construed according to the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase "means".

Claims

1. A system, comprising: a cantilever structure that is anchored at an anchoring end and connected at a distal end to a device, wherein use of the device imparts vibrations in the cantilever structure; and a harmonic absorber located at the distal end of the cantilever structure, wherein the harmonic absorber is tuned to a structural frequency of the cantilever structure so as to damp the vibrations in the cantilever structure.

2. The system according to claim 1, wherein the cantilever structure comprises: an anchoring section located at the anchoring end of the cantilever structure and extending in a vertical direction, a horizontal section connected to the anchoring section, and a curved boom section connected to the horizontal section and located at the distal end of the cantilever structure.

3. The system according to claim 2, wherein at least a portion of the harmonic absorber is positioned inside the curved boom section.

4. The system according to claim 2, wherein the anchoring section is connected to an upper outer surface of an imaging system.

5. The system according to claim 2, wherein a) the anchoring section of the cantilever structure is connected to the imaging system at an anchoring point, and b) the cantilever structure is rotatable about the anchoring point.

6. The system according to claim 2, wherein the cantilever structure further comprises: a hub section located at the distal end of the curved boom section, wherein at least a portion of the harmonic absorber is positioned inside the hub section.

7. The system according to claim 5, wherein the device is a monitor assembly that allows a user to interact with the imaging system.

8. The system according to claim 7, wherein the cantilever structure further comprises a hub section located at the distal end of the curved boom section, wherein at least a portion of the harmonic absorber is positioned inside the hub section, and wherein the monitor assembly includes a housing having a knuckle ball joint, and the hub section includes a knuckle adapter for connecting the hub section to the knuckle ball joint.

9. The system according to claim 1, wherein the device is a monitor assembly.

10. The system according to claim 1, wherein the harmonic absorber comprises: a mass, a spring, and a guide rod that positions the mass relative to a center of the spring.

11. The system according to claim 1, wherein the structural frequency is a first natural frequency of the cantilever structure.

12. A system for damping vibrations in a cantilever structure, the system comprising: a cantilever structure having a tubular structure that is anchored at an anchoring end and connected at a distal end to a hub configured to support a device from the cantilever structure, wherein use of the device imparts vibrations in the cantilever structure; a uniaxial harmonic absorber positioned inside the distal end of the cantilever structure and the hub, the uniaxial harmonic absorber comprising: a mass, a spring, and a guide rod that positions the mass relative to a center of the spring, The uniaxial harmonic absorber is tuned to the structural frequency of the tubular structure so as to damp vibrations in the tubular structure.

13. The system according to claim 12, wherein the structural frequency is the first natural frequency of the cantilever structure.

14. A system comprising: an imaging device; a cantilever structure that is anchored to the imaging device at an anchoring end and is connected at a distal end to a hub configured to support a device from the cantilever structure, wherein use of the device imparts vibrations in the cantilever structure; and a harmonic absorber connected to the cantilever structure and positioned inside the distal end and the hub of the cantilever structure, wherein the harmonic absorber is tuned to the structural frequency of the cantilever structure so as to damp vibrations in the cantilever structure.

15. The system according to claim 14, wherein the cantilever structure comprises: an anchoring section that is connected to the imaging device and extends in a vertical direction relative to an upper outer surface of the imaging device, a horizontal section connected to the anchoring section, and a curved boom section connected to the horizontal section and located at the distal end of the cantilever structure.

16. The system according to claim 15, wherein at least a portion of the harmonic absorber is positioned inside the curved boom section.

17. The system according to claim 14, wherein the device is a monitor assembly.

18. The system according to claim 14, wherein the harmonic absorber comprises: a mass, a spring, and a guide rod that positions the mass relative to a center of the spring.

19. The system according to claim 14, wherein the structural frequency is the first natural frequency of the cantilever structure.

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