EP2153083A1

EP2153083A1 - Vibration isolation

Info

Publication number: EP2153083A1
Application number: EP08727086A
Authority: EP
Inventors: Kurt Hallamasek
Original assignee: Ampex Corp
Current assignee: Ampex Corp
Priority date: 2007-03-20
Filing date: 2008-03-20
Publication date: 2010-02-17
Also published as: WO2008115589A1

Abstract

Systems and apparatuses are described for reducing shock and vibration experienced by a payload. In embodiments, a slender element, such as a blade made of spring steel, in its post-buckled state, supports or connects to a payload and reduces vibration effects on the payload. In embodiments, systems and apparatuses using buckled elements isolate or otherwise mitigate the effects of shock and/or vibration on a payload from forces in the vertical direction (i.e. the direction in line with the gravitational force), from forces in the horizontal direction, or both.

Description

VIBRATION ISOLATION

BACKGROUND

A. Technical Field

[0001] The present invention pertains generally to minimizing or isolating the effects of shock and/or vibration on an object (which includes without limitation, storage systems, electronic devices, mechanical devices, electro-optical devices, instruments, tools, equipment, and other items), and relates more particularly to systems and apparatuses for reducing vibration effects on a payload.

B. Background of the Invention

[0002] Many storage systems, electronic devices, instruments and other equipment are sensitive to vibrations and cannot operate correctly when exposed to excessive vibration levels. Environments that are especially susceptible to excessive vibration include mobile platforms such as aircraft, automotive vehicles and other vessels.

[0003] To improve the performance, to extend the operating life, and/or to improve the operating efficiency of such objects in environments where motion noises effects are present, vibration isolators are used to reduce the vibrations experienced by the object. Current vibration isolation products often rely on visco-elastic materials (such as rubber and rubber-like compounds), coils, or conventional springs to provide the vibration isolation for such equipment. These products have limitations which leave room for improved vibration isolation systems based on other technologies. SUMMARY OF THE INVENTION

[0004] Systems and apparatuses are described for reducing unwanted motion to a payload. It shall be understood that unwanted motions from vibrations shall be construed to mean vibration, shock, or both.

[0005] An aspect of the present invention is the use of constraints in connection with Euler springs to reduce unwanted motion. In embodiments, a system for reducing vibrations of a payload includes a payload mount and at least one Euler spring. The Euler spring is configured to connect at one end to the payload mount, and its other end is configured to be coupled to a supporting structure. The Euler spring is constructed to be in a post-buckled state that reduces vibrations of a payload attached to the payload mount by displacing. The system also includes one or more constraints configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a displacement stage of the Euler spring. The constraints may be configured to contact different Euler springs, different positions of an Euler spring, and/or contact at different displacement stages. In embodiments, a constraint may be configured to produce a non-linear spring behavior in the Euler spring.

[0006] In embodiments, vibration isolation systems may include a compensation system. The compensation system may comprise a sensor that detects a characteristic related to motion, (such as position, velocity, or acceleration), a compensator that provides an output that is at least in part based upon a detection from the sensor, and an actuator that, responsive to the output provided by the compensator, alters a configuration of a constraint. The configuration of the constraint that may be altered includes its position relative to the Euler spring and its shape. In embodiments, the constraint may be configured to affect an angle of departure of at least one of the first and second ends of an Euler spring. [0007] Embodiments of systems for reducing vibration effects on a payload include controllably altering one or more of the angle of departures of the ends of one or more Euler springs. For example, in embodiments, a system for reducing vibrations of a payload includes a payload mount connected to a first mounting connector and an Euler spring with its first end connected in a fixed position relative to the first mounting connector forming a first angle of departure of the Euler spring, and the Euler spring's second end connected in a fixed position relative to a second mounting connector forming a second angle of departure of the Euler spring. In the embodiments, at least one of the first and second mounting connectors is controllably alterable to change the angle of departure associated with the Euler spring end connected to the mounting connector.

[0008] Such embodiments may include a compensation system for altering one or more angles of departure or for altering one or more constraints, if present. An embodiment of a compensation system has a sensor that detects a characteristic related to motion (such as position, velocity, or acceleration), a compensator that provides an output that is at least in part based upon a detection by the sensor, and an actuator that, responsive to the output provided by the compensator, alters at least one of the first and second mounting connectors to change the angle of departure associated with the Euler spring end connected to the mounting connector.

[0009] In embodiments, the compensation system may be or may include a feedback system, hi an embodiment, the detection of the sensor is a measurement that indicates a position of the payload and the feedback compensator provides a feedback output to the actuator using a position setpoint and the measurement that indicates a position of the payload.

[0010] hi embodiments, the compensation system may be or may include a feedforward system. In an embodiment, the characteristic related to motion that the sensor detects is acceleration of a support structure that supports an assembly comprising the payload mount and Euler spring and the feedforward output provided by the feedforward compensator is at least in part based upon an acceleration measurement detected by the sensor.

[0011] In embodiments, the compensation system may include both feedback and feedforward systems. In embodiments, an adder sums the feedforward output with the feedback output to obtain the output provided to the actuator.

[0012] In embodiments, one or more constraints may also be utilized in a system that alters one or more angles of departure. Such a system may account for constraint contact with an Euler spring when determining an output for the actuator. In embodiments, a compensation system may alter a configuration of a constraint.

[0013] Aspects of the present invention also include embodiments utilizing a payload supported in an inverted pendulum configuration by one or more Euler springs that have one or more universal joint connections.

[0014] In embodiments, a system for reducing vibrations of a payload includes a payload connected to an Euler spring having a first end and a second end. The first end of the Euler spring is connected to a mounting connector of the payload and the second end connects to a second mounting connector which is configured to connect to a support structure. The Euler spring supports the payload in an inverted pendulum configuration and the Euler spring is constructed to be in a post-buckled state that reduces vibrations of the payload by displacing. In this system, at least one of the first and second mounting connectors is a universal joint. Such a system may include one or more additional Euler springs. In embodiments, at least one Euler spring is connected to the payload and is in a non-parallel configuration to the first Euler spring. For example, in an embodiment, the second Euler spring may be in a horizontal configuration relative to the first Euler spring that places the payload in an inverted pendulum position. In embodiments, one or more constraints and/or one or more compensation systems may also be employed in the system to help reduce vibration effects.

[0015] Some features and advantages of the invention have been generally described in this summary section; however, additional features, advantages, and embodiments are presented herein or will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims hereof. Accordingly, it should be understood that the scope of the invention shall not be limited by the particular embodiments disclosed in this summary section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

[0017] Figure IA illustrates a cross sectional schematic view of a vibration isolation system according to an embodiment of the invention.

[0018] Figure IB illustrates a vibration isolation system according to an embodiment of the invention.

[0019] Figure 1C illustrates a vibration isolation system according to an embodiment of the invention.

[0020] Figure ID illustrates a vibration isolation system according to an embodiment of the invention.

[0021] Figure 2 is a plot of Force (lbf) versus Displacement (inches) for a sample metal spring blade for a vibration isolation system according to an embodiment of the invention. Figure 2 also illustrates the shape of the blade for various forces.

[0022] Figure 3 A is a perspective view of a vibration isolation system according to an embodiment of the invention.

[0023] Figure 3B is a line drawing of the embodiment depicted in Figure 3 A.

[0024] Figure 4A is a perspective view of inner frame 120 with payload 150 according to an embodiment of the invention. [0025] Figure 4B is the perspective view of inner frame 120, with the front right support beam removed to show the pendulum structure according to an embodiment of the invention.

[0026] Figure 4C is a line drawing of the embodiment depicted in Figure 4A.

[0027] Figure 4D is a line drawing of the embodiment depicted in Figure 4B.

[0028] Figure 5 A illustrates an embodiment of a vibration isolation system in which the ends of the blades are fixed according to an embodiment of the invention.

[0029] Figure 5B is a line drawing of the embodiment depicted in Figure 5 A.

[0030] Figure 6 illustrates two blades comprising lower ends having different angles of departure from their mounting supports according to an embodiment of the invention.

[0031] Figure 7A illustrates a constraint 700 according to an embodiment of the invention.

[0032] Figure 7B is a graph of displacement versus force for a blade 130 which is first free to deflect and then be constrained in its deflection by a constraint 700 according to an embodiment of the invention.

[0033] Figure 8 illustrates a vibration isolation system for a single degree of freedom system in which the angle of departure 600 of an Euler spring 130 from its mounting connector is adjusted by an actuator 670 to vary the force the Euler spring exerts to address inertial forces when the system is mounted on a moving platform, according to an embodiment of the invention. DETAILED DESCRIPTION

[0034] Systems and apparatuses for vibration isolation are described. In this written disclosure, the term vibration (or vibrations) shall be construed to collectively and individually cover the various forms of unwanted motions from vibration and shock. Also, one skilled in the art shall recognize that the term "isolation" as used, for example, in "vibration isolation system" refers to a system that helps minimize unwanted motion. Because no system perfectly isolates unwanted motion effects from a payload, references to vibration isolation or vibration isolation systems shall not be construed to require complete isolation, but rather, shall be construed to encompass systems that reduce the effects of unwanted motion on a payload.

[0035] For purposes of explanation, specific details are set forth in order to provide an understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these details. Furthermore, one skilled in the art will recognize that embodiments of the present invention, described below, may be implemented in a variety of ways and constructed from a variety of materials. Accordingly, the figures described below are illustrative of specific embodiments of the invention and are meant to avoid obscuring the invention.

[0036] Reference in the specification to "one embodiment," "a preferred embodiment" or "an embodiment" means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention and may also be in more than one embodiment. Also, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment. [0037] Components, or modules, shown in the figures are illustrative of exemplary embodiments of the invention and are meant to avoid obscuring the invention. It shall be understood that throughout this discussion that components may be described as separate functional units, which may comprise sub-units, but those skilled in the art will recognize that the various components, or portions thereof, may be divided into separate components or may be integrated together. Furthermore, connections between components within the figures are not intended to be limited to direct connections. Also, additional or fewer connections may be used. In addition, signals between electrical components may be modified, re-formatted, or otherwise changed by intermediary components.

[0038] Many objects (such as, by way of example and not limitation, storage systems, electronic devices, mechanical devices, electro-optical devices, instruments, tools, equipment, and other items) are sensitive to undesired motions, which may affect the objects' performance, operation, lifespan, etc. However, there is often a desire to use such items in vibration-prone environments. For example, when operating disk drives in an aircraft to store information, excessive vibrations within the aircraft can cause the disk drives to function at reduced performance levels or to malfunction.

[0039] The present invention comprises systems and apparatuses that reduce the vibration experienced by a payload, which may be, by way of example and not limitation, a storage system, an electronic device, a mechanical device, an electro-optical device, an instrument, tool, equipment, and other item. The systems and apparatuses of the invention may be designed to isolate (which includes partially isolating) the payload from a range of vibration forces external to the system or apparatus. As a result, the motion of the payload is reduced, which allows the payload to operate reliably for the range of vibration forces. One skilled in the art will recognize that the range of acceptable motion will vary for a given payload.

[0040] Figure IA illustrates a cross-sectional schematic view of a vibration isolation system according to one embodiment of the invention. As noted above, the term vibration (or vibrations) shall be construed to collectively and individually cover the various forms of unwanted motions, including from vibration and shock. The reader is also reminded that the "isolation" as used herein does not require perfectly isolation from unwanted motion. The vibration isolation system provides isolation of a payload against vibrations exerted in both the vertical and horizontal directions. The system is comprised of an outer frame 110 serving to support a payload 150 and an inner frame 120 that forms part of the structure that supports the payload relative to the supporting outer frame so that the payload can move relative to the outer frame. One skilled in the art will recognize that the outer and inner frames may be constructed using a variety of materials, including but not limited to, metal, plastic, and/or composites. For clarity, Figure IA shows the constituent components of a two-dimensional system. One skilled in the art will readily be able to generalize this topology to a three-dimensional system. Figures 5 A and 5B show a three-dimensional realization of the type illustrated in Figure IA.

[0041] In one embodiment of the invention, the weight of the inner frame 120 and its payload 150 is supported within the outer frame by one or more spring blades 130. In Figure IA, two blades 130 are illustrated, one on each side of payload 150. While only one blade is illustrated on each side in this example, the invention is not so limited. A number of blades may be employed on each side of the payload to achieve the desired support conditions for the payload. Blades may be arranged to support the payload 150 and inner frame 120 so that inner frame 120 and payload 150 are balanced with respect to their center of gravity or center of percussion. Further, multiple blades may be used in parallel to achieve the desired spring behavior.

[0042] In one embodiment, a blade is a thin strip of material with a rectangular cross section. However, the invention is not limited to blades having a rectangular cross section. Rods with circular cross sections or other slender members with other shaped cross sections may be used instead. One skilled in the art will recognize that the blades may be made of a number of materials, including but not limited to metal, plastic, or composites.

[0043] In one embodiment, the geometric and material properties of the blade(s) are selected such that when the payload 150 and inner frame 120 are supported by the blade(s), the weight of the inner frame 120 plus the payload 150 exceeds the critical force at which buckling of the blade(s) occur. For example, as illustrated in Figure IA, the weight of the payload 150 and inner frame 120 are such that the blades 130 are buckled.

[0044] The buckling force for a slender compression element, a column, was first analyzed by Leaonhard Euler and is called "Euler buckling." For the case when both ends of the column are free to rotate, Euler buckling occurs when the critical force in the axial direction, P_cr, of the column exceeds P_cr = π²EI/L², where E is the modulus of elasticity, I is the area moment of inertia and L is the length of the column. J. Winterflood and D. G. Blair at the University of Western Australia, Perth, noted that the force-displacement characteristics of columns just after onset of buckling is spring-like for a useful range of motion and coined the term Euler spring, which is discussed in Winterflood, J., Blair, D. G. and Slagmolen, B., "High performance vibration isolation using springs in Euler column buckling mode." Physics Letters A, 300: pp. 122-130 (2002), which is incorporated by reference herein in its entirety. Also incorporated herein by reference in their entirety are: Winterflood, J., T. A. Barber, and D. G. Blair, "Mathematical analysis of an Euler spring vibration isolator." Physics Letters A, 300: pp. 131- 139 (2002); Winterflood, J., T. A. Barber, and D. G. Blair, "Using Euler buckling springs for vibration isolation." Classical and Quantum Gravity. 19: pp. 1639-1645 (2002); John Winterflood, High Performance Vibration Isolation For Gravitational Wave Detection (thesis presented for the degree of Doctor of Philosophy at the University of Western Australia, Department of Physics, 2001) LIGO-P020028-00-R. It shall be noted that herein the terms, blades, spring blades, and Euler springs are used interchangeably.

[0045] Since a buckled blade acts as a low-mass spring, it can be used to isolate against vibration and shock. Using one or more buckled blades, vibrations may be attenuated over a large range of frequencies, resulting in much lower vibration levels transmitted to the payload. In the configuration of Figure IA, the blades 130, when buckled, act as springs to isolate the inner frame 120 and payload 150 from much of the vibration forces acting in the vertical direction, which is in the direction of the force applied to the blades 130 by the supported payload 150. As the outer frame 110 moves in the vertical direction as a result of the vertical vibrations, the motion of the inner frame 120 and payload 150 in the vertical direction is reduced significantly relative to the vertical motion of outer frame 110.

[0046] Figure 2 is a plot of the Force (lbf) versus Displacement (inches) for a sample blade of spring steel that measures O.O15"xO.25"x6". hi this example, the end of the blade is pinned, which allows the blade to pivot as force is applied from the payload. Plotted is the displacement of the blade versus the axial force applied to it. The shape of the blade for various forces is also illustrated.

[0047] One skilled in the art will recognize that there are a number of ways to connect the blades 130 to the payload and to a support structure. In embodiments, the payload may be attached to a payload mount. In embodiments, the inner frame 120 may function as a payload mount. Alternatively, the payload mount(s) may be integrated with the payload, for example, as depicted in Figure IB. It shall be noted that the payload may be directly connected to the payload mount or may be indirectly connected to the payload mount. For example, in Figure IA and Figure 1C, inner frame 120 acts as payload mount in which a secondary vibration isolation mechanism (pendulum 170) connects to the payload 150. Whereas, in the embodiment depicted in Figure IB, the payload mount may be considered to connect directly to the payload.

[0048] It shall also be noted that a number of items may function as support member. In embodiments, the outer frame 110 acts as the support member or support structure. However, one skilled in the art shall recognize that a chassis, table, platform, base, or other support member may be used. For example, in embodiments, one or more Euler springs may be connected at one end to a payload via payload mounts and at the other end to a support structure.

[0049] Furthermore, one skilled in the art will recognize that there are a number of ways to connect the blades 130 to realize different end constraints for the blades 130. One skilled in the art will recognize that the shape of the blade 130 as it buckles in response to an axial force applied to the blade 130 varies depending on the way in which the blade 130 is connected. The shape of a blade 130 as it buckles influences the spring rate of the blade. For example, an end of blade 130 may be free to rotate at the point of attachment/mounting connection (i.e. "pinned"), or it may be clamped rigidly (i.e. "fixed").

[0050] In one embodiment, the blades 130 are connected to outer frame 110 and to railing 145 of the inner frame 120. In the embodiment illustrated in Figure IA, each end of the blade 130 is fixed to the outer frame 110 and the inner frame 120. Figures 5 A and 5B illustrate a realization of such an embodiment in which the ends of the blades 130 are fixed. This configuration leads to a lower natural resonance frequency, for the same blade length, compared to configurations in which blade ends are pinned. As a result, the isolation becomes effective for vibrations at a lower frequency.

[0051] In an alternative embodiment, illustrated in Figure 1C, each end of blade 130 is pinned. Figure 3A show an embodiment of this type of system. Figure 3B is a line drawing of the embodiment depicted in Figure 3A.

[0052] In an alternative embodiment, the attachment of the blade ends on the inner frame may be fixed while the attachment of the blade on the outer frame may be pinned. Conversely, the attachment of the blade ends on the inner frame may be pinned while the attachment of the blade ends on the outer frame may be fixed.

[0053] One skilled in the art shall also recognize that one or more combinations of the payload mounts, Euler springs, and support structures may be fabricated from a single item. For example, in an embodiment, an Euler spring and a support structure may be formed from a single piece of plastic wherein a compliant mechanism hinge forms the mounting connector between an end of the Euler spring and the support structure. Thus, it should also be noted that the mounting connector need not be limited to a separate component. One skilled in the art of complaint mechanisms shall recognize any of number of ways to implement such configurations. Furthermore, it shall be noted that the teachings of the present invention may be implemented in semiconductor devices/integrated circuits, such as for example, in Micro-Electro-Mechanical systems (MEMs). Accordingly, the payload mounts, Euler springs, and/or support structures may be formed using materials used in the fabrication of semiconductor devices/integrated circuits. [0054] In one embodiment, the spring rate can be tailored to increase as a function of displacement. Non-linear spring behavior can be designed by constraining the deflection of buckling members along loci of deflection. Figure 7A illustrates a constraint 700 according to one embodiment of the invention. As an increasing force is applied to the blade in a post- buckled state, the blade deflects until it comes into contact with the constraint surface 700. During this displacement stage, the constraint 700 restricts the blades movement and reduces the effective free length of the blade that acts as a spring. As the effective length decreases, the spring rate increases. Figure 7B is a graph of displacement versus force, and illustrates the two regions or displacement stages of blade deflection operation, namely, unconstrained operation before the blade contacts the constraint surface 700 and constrained operation after the blade has contacted the constraint surface. This can be an important design tool when designing vibration isolation system for shock performance, hi embodiments, it may be desirable to increase the spring rate of the Euler spring as the payload approaches the limits of its sway space. This also allows multiple springs to be combined in constructing a vibration isolation system that functions in any orientation (i.e. in which the direction of gravity or centrifugal force is not known or is variable).

[0055] Configuration of a constraint includes its position relative to a spring blade, its shape, or both. Furthermore, one skilled in the art shall recognize that constraints may be configured to increase or to decrease the spring force of a spring blade. Also, it shall be noted that multiple constraints and multiple configurations of constraints may be employed. For example, in an embodiment, a first constraint may contact a blade once a first displacement stage has been reached and a second constraint may contact the blade at a different location once a second displacement stage. In embodiments, the first and second displacement stages may be the same stage.

[0056] In one embodiment, payload 150 is supported within inner frame 120 using one or more pendulums. In the embodiment illustrated in Figure IA, pendulums isolate payload 150 from vibrations applied to the inner frame 120 in the horizontal directions. Although two pendulums are illustrated in Figure IA, one skilled in the art will recognize that any number of pendulums, including a single pendulum may be used to isolate payload 150 from vibrations applied to the inner frame 120 in the horizontal directions.

[0057] Each pendulum is comprised of a cable 170 that connects the upper surface of inner frame 120 to payload 150. In this configuration, the payload 150 is the weight of the pendulums. The pendulums isolate payload 150 from horizontal vibrations applied to inner frame 120. As the inner frame 120 moves in the horizontal direction as a result of horizontal vibrations, the motion of payload 150 in the horizontal direction is reduced significantly relative to the horizontal motion of the inner frame 120.

[0058] In one embodiment of the invention, secondary cable restraints 180 may be connected from the payload 150 to the bottom surface of the inner frame 120. The secondary cable restraints 180 further constrain the displacement of the payload relative to the inner frame to the limits of the sway space between the inner frame 120 and the payload 150. In one embodiment, secondary cable restraints 190 may also be used to further restrain the displacement motion of inner frame 120 relative to the outer frame. The secondary cable restraints 190, illustrated in Figure IA, prevent the inner frame 120 from tilting or rotating within outer frame 110. [0059] Figure 4A illustrates a perspective view of inner frame 120 with payload 150 according to one embodiment of the invention. In this embodiment, the weight of payload 150 is supported within inner frame 120 by four pendulums. Each pendulum is comprised of a cable 420 that is suspended from the upper surface of inner frame 120 and wraps around or other wise connects to a portion of the payload 150. In this configuration, the payload is the weight of the pendulum.

[0060] In one embodiment, the cable 420 wraps around a cylinder 450 protruding from the payload 150 and is held in place by a screw 430. In one embodiment cylinder 450 is made of a material, such as rubber that provides further vibration dampening. The pendulums isolate the payload 150 from horizontal vibrations applied to inner frame 120 and allow the payload 150 to be displaced relative to the inner frame 120 within the sway space between the payload 150 and the inner frame 120. As the inner frame 120 moves in the horizontal direction as a result of horizontal vibrations, the motion of the payload 150 in the horizontal direction is reduced significantly relative to the horizontal motion of the inner frame 120. In one embodiment, cable 420 further extends below the connection point with the payload and is connected to the bottom surface of inner frame 120. This portion of cable 420 acts as a secondary cable restraint which further constrains the displacement of the payload 150 relative to the inner frame 120 to the limits of the sway space between the inner frame 120 and the payload 150.

[0061] Figure 4B is an illustration of the inner frame 120 from Figure 4 A, omitting the support beam in the front right corner of the inner frame 120. This view shows the pendulum structure of the front right corner of the inner frame 120 which is used to support the payload 150. In one embodiment, each corner of the inner frame 120 comprises a similar pendulum structure. The four structures function to support the payload and isolate payload 150 from horizontal vibrations.

[0062] Figures 3 A and 3B illustrate a perspective view of a vibration isolation system according to one embodiment of the invention. In this embodiment, four blades 130 are used to support inner frame 120 within outer frame 110. Two of the blades 130 are illustrated, while the two additional blades 130 (not shown) are positioned out of view on the opposite side of the vibration isolation system.

[0063] In one embodiment, the blades 130 are connected to railing 340 of outer frame 110. The blades 130 are also connected to railing 345 of the inner frame 120. One skilled in the art will recognize that there are a number of ways to connect the blades 130 to the inner frame 120 and the outer frame 110. In one embodiment, railings 340 and 345 may comprise a number of teeth in which the blades 130 may be recessed. The teeth in the railing provide flexibility in positioning the blades so they support the payload effectively through the center of gravity.

[0064] In an alternative embodiment of the invention, illustrated in Figure IB, blades provide both horizontal and vertical vibration isolation to payload 150. In one embodiment, blades 130 are attached to the outer frame 110 and to the payload mounts of the payload 150 with universal joints 155. The ends of the blades 130 are fixed in the universal joint but allowed to tilt in all directions. In this way, the blades 130 function as inverted pendulums to isolate payload 150 from horizontal and vertical vibrations. Horizontal blades 135 and 136 stabilize the payload 150 in the presence of horizontal vibrations, kinetic and gravitational forces that the payload 150 may be experiencing on a mobile platform, for example, to keep payload 150 in a nominally upright position. When the payload 150 is in the upright position, the force exerted by blade 135 cancels the force exerted by blade 136 and the payload remains upright. If the payload inclines toward blade 135 due to horizontal vibrations or because of the acceleration of the mobile platform on which the system may be mounted, blade 135 will push the payload back towards the upright position. Similarly, blade 136 restores the payload 150 to the upright position when the payload tilts toward blade 136.

[0065] hi embodiments, a constraint surface 700 may be used to alter the spring force of blades 135 and/or 136 as a function of displacement so as to effectively counteract the gravitational force or other forces that may act to imbalance the inverted pendulum. As blade 135 or 136 deflects, it comes into contact with the constraint surface 700. The surface restricts that blades movement and reduces the free length of the blade that acts as a spring. This increases the spring rate of the spring and helps to prevent the payload from coming into contact with outer frame 110.

[0066] One skilled in the art will recognize that there are a number of configurations of blades that may be used to support payload 150. In one embodiment, blades may also be positioned in a similar manner perpendicular to the plane of Figure IB to provide further isolation of payload 150 within outer frame 110.

[0067] Figure ID illustrates an alternative vibration isolation system according to one embodiment of the invention. In this embodiment, horizontal vibration isolation of payload 150 is accomplished through pendulums 170A and 170B suspended from the outer frame 110 that are coupled to the payload 150 through bell cranks 175 A and 175B respectively. Bell cranks 175 A and 175B are coupled to payload 150 through at least one blade 130A and 130B respectively. The bell cranks 175 A and 175B also pivot around pivots 165 A and 165B which are coupled to payload 150. [0068] In one embodiment, the bell cranks 175 A and 175B in combination with blades 130A and 130B, respectively, isolate the payload from vibrations exerted in the vertical direction. The weight of the payload 150 creates a moment of force about pivot 165 A. This force is countered by the bell crank 175B in combination with blades 130B. Similarly, the weight of payload 150 creates a moment of force about pivot 165B, which is countered by bell crank 175 A in combination with blades 130A. Vibration forces exerted in the vertical direction may increase or decrease the moment of force created by the weight of payload 150. Blades 130A and 130B, when configured in a buckled state, act as springs to absorb these vibration forces.

[0069] In the embodiment illustrated in Figure ID, the two blades 130 (the two blades of 130A or the two blades of 130B) are buckled in opposing directions and are coupled between the bell crank 175 and payload 150. As a blade starts to buckle, the direction of the offset deflection of the blade can be in one of two directions. When mounted in a pivoted support structure as shown in Figure ID, the effect of the offset of the blade in one direction is different from the effect of the offset of the blade in the opposite direction. For example, if the blade buckles towards the pivot, then a low spring rate is obtained. If the blade buckles away from the pivot, then a higher spring rate is obtained. By matching a pair of blades to buckle in opposing directions, the net spring rate of the two is closer to what would be obtained if it were restrained to move linearly rather than in a rotating support structure.

[0070] One skilled in the art will recognize that alternative configuration of the bell cranks 175 and blades 130 are possible. For example, in one embodiment, the bell crank configuration illustrated in Figure ID may be implemented on each side of the payload 150. In an alternative embodiment, the bell crank configuration may be implemented on opposing sides of the payload 150. In yet another alternative, bell cranks 175 A and 175B may be positioned on opposing sides of payload 150. One skilled in the art will also recognize that there are other ways of using levers to use the buckled blades so they are not inline with the gravitational force while they still isolate vibration in that direction.

[0071] In one embodiment, the spring rate of a blade may be changed by adjusting the angle of departure of the blade. For example, if the ends of a blade are clamped or fixed at an angle, as opposed to being extending vertical from its mount, the force supported by the blade decreases. Figure 6 illustrates two sample blades 530 and 540, which have different angles of departure. The ends of blade 530 are fixed perpendicular to railings 550 and 560 respectively. By contrast, the angle of departure for the bottom end of blade 540 has been adjusted by an angle α away from perpendicular. By changing the angle of departure, the force supported by the blade 540 is decreased compared to the force supported by blade 530.

[0072] One skilled in the art will recognize that there are a number of ways to change the angle of departure of a blade. In the embodiments described previously in which the ends of a blade are recessed into teeth in a railing, the angle of departure for one end of a blade may be adjusted by simply recessing one end of the blade in-between a different set of teeth within the rail while leaving the opposite end of the blade in the same location. As another example, when using fixed blades, the clamp that fixes the blade to a surface may be angled relative to the surface to alter the angle of departure of the blade.

[0073] The angles of departure of the blade, at one or both of its mounting points, may be adjusted dynamically to vary the force applied to the payload in order to meet specific performance objectives. For example, when the vibration isolation system is installed on an aircraft, inertial forces must act on the payload during aircraft maneuvers such as takeoffs, landings and turns in order to move the payload along the trajectory of the aircraft. In other words, the payload must be accelerated with the aircraft, and in order to do so, forces must be applied to the payload. These forces may be allowed to act on the payload in a controlled manner by adjusting the angle of departure of the blade. The force which a blade exerts on the payload may be regulated with a compensation system, such as, by way of example and not limitation, a servo-controlled system. Figure 8 illustrates a vibration isolation/absorption system for a single degree of freedom system, according to an embodiment of the invention. For clarity, Figure 8 depicts the system only regulating motion in the vertical direction; however, the principles are readily extended to regulating motion in additional degrees of freedom. In Figure 8, the payload may be configured the same as or similar to the embodiment depicted in Figure IB.

[0074] hi the embodiment depicted in Figure 8, the position 610 of the payload 150 relative to the outer frame 110 is detected. The angle of departure 600 of the end of the blade 130 fixed to the outer frame 110 is adjusted by an actuator, which in the depicted embodiment is a motor 670, to regulate this detected position 610 around the position setpoint 620. The position setpoint would typically be in the center of the sway space. One skilled in the art shall recognize that any of number of actuators may be employed, included by way of example and not limitation, piezoelectric, voice coils, motors, pneumatics, hydraulics, and the like, and that no particular actuator is critical to the present invention. One skilled in the art shall also recognize that it may also be advantageous to detect acceleration or velocity of the payload and use the detection to regulate the payload position. It shall be noted that position, velocity, and acceleration are characteristics related to motion. Accordingly, embodiments of the present invention may include one or more sensors that detect one or more characteristics related to motion. One skilled in the art shall recognize that detecting a characteristic related to motion may be accomplished by measuring one or more of position, velocity, and acceleration.

[0075] The feedback compensation 640 shapes the loop dynamics. The loop dynamics would typically be adjusted to allow the payload to follow the low-frequency trajectory dynamics of the mobile platform to which the outer frame 110 or other spring supporting structure is attached - in this example the aircraft - while not tracking high-frequency vibrations - in this example the structural vibrations of the airframe. If the loop bandwidth of the compensation system includes the natural resonance of the payload/blade system, it will actively damp the payload. The feedforward compensation 650 would typically be designed so that the force applied by the Euler spring 130 to the payload 150 is commensurate with the inertial forces caused by the motion of the platform the outer frame 110 or other spring supporting structure is attached to. In practice, the signal producing the acceleration reference 630 would typically be produced by an accelerometer attached to the outer frame or other spring supporting structure, measuring the acceleration of the mobile platform. One skilled in the art shall understand that the compensation system may be implemented using servo design theory and the like. One skilled in the art shall also recognize that no particular implementation of either the feedback compensator 640 or the feedforward compensator 650 is critical to the present invention. Accordingly, either or both systems may be analog or digital, the feedback compensator may implement one or more modes of proportional, integral, and derivative (PID) control, or other type of control.

[0076] One skilled in the art shall recognize that a vibration isolation system that includes a compensation system may include feedback compensation, feedforward compensation, or both. Furthermore, one skilled in the art shall recognize that the active control provided by a compensation system may be applied to other elements of the system, including without limitation, to the number of constraints, the position of the constraints, the topology of a constraint, and to any of the mounting points in the system. In embodiments, a constraint may be actively used to adjust an angle of deflection of an Euler spring by effectively altering an end condition of the spring.

[0077] While the present invention has been described with reference to certain embodiments, those skilled in the art will recognize that the invention is not limited to the specific embodiments discussed. For example, though many of the embodiments illustrate single blades in a buckled state, one skilled in the art will recognize that multiple blades could be used in parallel or in opposing buckled states to achieve desired spring rates. Variations upon and modifications to the embodiments are provided for by the present invention.

Claims

CLAIMSI claim:

1. A system for reducing vibrations of a payload, the system comprising: a payload mount; a Euler spring having a first end and a second end opposite the first end, the first end connected to the payload mount and the second end configured to be connected to a supporting structure, the Euler spring constructed to be in a post-buckled state that reduces vibrations of a payload attached to the payload mount by displacing; and a constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a displacement stage of the Euler spring.

2. The system of claim 1 wherein the constraint is a first constraint and the system further comprises: a second constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a second displacement stage of the Euler spring; and wherein the second constraint contacts the Euler spring at a location between the first and second ends of the Euler spring that is different from that contacted by the first constraint.

3. The system of claim 1 wherein the constraint produces a non-linear spring behavior in the Euler spring.

4. The system of claim 1 further comprising a compensation system comprising: a sensor that detects a characteristic related to motion; a compensator that provides an output that is at least in part based upon a detection from the sensor; and an actuator that, responsive to the output provided by the compensator, alters a configuration of the constraint.

5. The system of claim 4 wherein the configuration of the constraint that is altered is its position relative to the Euler spring.

6. The system of claim 4 wherein the constraint alters an angle of departure of at least one of the first and second ends of the Euler spring.

7. A system reducing vibrations of a payload, the system comprising: a payload mount connected to a first mounting connector; and an Euler spring having a first end and a second end opposite the first end, the first end of the Euler spring connected in a fixed position relative to the first mounting connector that forms a first angle of departure of the Euler spring, and the second end connected in a fixed position relative to a second mounting connector that forms a second angle of departure of the Euler spring, the Euler spring constructed to be in a post-buckled state that reduces vibrations of a payload attached to the payload mount by displacing, and at least one of the first and second mounting connectors is controllably alterable to change the angle of departure associated with the Euler spring end connected to the mounting connector.

8. The system of claim 7 further comprising a compensation system comprising: a sensor that detects a characteristic related to motion; a compensator that provides an output that is at least in part based upon a detection by the sensor; and an actuator that, responsive to the output provided by the compensator, alters at least one of the first and second mounting connectors to change the angle of departure associated with the Euler spring end connected to the mounting connector.

9. The system of claim 8 wherein the compensation system comprises a feedback system comprising: a feedback compensator that provides a feedback output that is at least in part based upon a detection by the sensor and wherein the output provided to the actuator is, at least in part, based upon the feedback output.

10. The system of claim 9 wherein the detection of the sensor is a measurement that indicates a position of the payload and the feedback compensator provides a feedback output to the actuator using a position setpoint and the measurement that indicates a position of the payload.

11. The system of claim 8 wherein the compensation system further comprises a feedforward system comprising: a feedforward compensator that provides the output that is at least in part based upon a detection by the sensor.

12. The system of claim 11 wherein the characteristic related to motion that the sensor detects is acceleration of a support structure that supports an assembly comprising the payload mount and Euler spring and wherein the feedforward output provided by the feedforward compensator is at least in part based upon an acceleration measurement detected by the sensor.

13. The system of claim 9 wherein the compensation system further comprises a feedforward system comprising: a feedforward sensor that detects a characteristic related to motion a support structure that supports an assembly comprising the payload mount and Euler spring; a feedforward compensator that provides a feedforward output that is at least in part based upon a detection by the feedforward sensor; and wherein the compensator comprises an adder that sums the feedforward output with the feedback output to obtain the output provided to the actuator.

14. The system of claim 7 further comprising: a constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a displacement stage of the Euler spring.

15. The system of claim 14 wherein the output provided to the actuator is determined at least in part by whether the Euler spring contacts the constraint surface.

16. The system of claim 14 further comprising: a constraint compensator that provides an output that is at least in part based upon a detection from a sensor; and a constraint actuator that, responsive to the output provided by the constrain compensator, alters the position of the constraint.

17. A system for reducing vibrations of a payload, the system comprising: a payload having a first mounting connector; an Euler spring having a first end and a second end opposite the first end, the first end of the Euler spring connected to the first mounting connector and the second end connected to a second mounting connector which is configured to connect to a support structure, the Euler spring supporting the payload in an inverted pendulum configuration and the Euler spring constructed to be in a post- buckled state that reduces vibrations of the payload by displacing; and wherein at least one of the first and second mounting connectors is a universal joint.

18. The system of claim 17 wherein the Euler spring is a first Euler spring and the system further comprises at least one Euler spring connected to the payload that is in a non- parallel configuration to the first Euler spring.

19. The system of claim 17 further comprising: a constraint configured to contact at least a portion of the Euler spring between the first and second ends of the Euler spring during a displacement stage of the Euler spring.

20. The system of 17 further comprising a compensation system comprising: a sensor that detects a characteristic related to motion; a compensator that provides an output that is at least in part based upon a detection^by the sensor; and ator that, responsive to the output provided by the compensator, alters at least one of the first and second mounting connectors to change an angle of departure at which the associated Euler spring end extends from the connected mounting connector.