ELASTIC LOAD SUSPENSION
Elastic load suspension systems and methods are disclosed. Embodiments include handles with springs to reduce peak forces and reduce the overall energy required to carry a load. Some embodiments include handles that connect to loads, where the effective spring length statically deflects at least 2.5 and at most 18 inches, and in some embodiments approximately 5 inches, when carrying the load. Alternate embodiments include elastic suspension handles that are lightly damped, such as those with a damping ratio of at most 0.5. Still further embodiments include elastic suspension handles that elastically suspend loads and have a natural frequency that is less than the locomotive frequency of the object carrying the handle, such a less than the typical human walking frequency of 2 Hertz.
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This application claims the benefit of U.S. Provisional Application No. 61/545,407, filed Oct. 10, 2011, the entirety of which is hereby incorporated herein by reference.
GOVERNMENT RIGHTSThis invention was made with government support under 1131423 awarded by the National Science Foundation. The government has certain rights in the invention.
FIELDEmbodiments of this disclosure relate generally to carrying loads, a particular example including suspending loads being carried in order to minimize the forces exerted on the individual carrying the load and/or to reduce the energy required to carry the load.
BACKGROUNDEnergy is required to move of an object and an objects being moved imparts forces to the device or person moving the object. As an example, a person carrying an object, such as a suitcase, expends energy to move the object. In addition to the energy required to move the object horizontally from place to place, additional energy is typically expended as the object moves up and down as the person walks. The object being moved, the suitcase in this example, also imparts forces onto the person while it is being moved, and these forces may vary with time reaching periodic maximum values, which may occur when the object reaches the bottom of its up and down motion while being carried.
SUMMARYEmbodiments of the present disclosure provide an improved elastic load suspension apparatuses and methods.
Embodiments of the present disclosure provide reduced peak forces and/or increased locomotive efficiency.
Some embodiments include handles with springs, where in some embodiments the effective spring length statically deflects at least 2.5 and at most 18 inches, at least 4 inches and at most 10 inches, and in some embodiments approximately 5 inches, when carrying the load.
Alternate embodiments include elastic suspension handles that are lightly damped, such as those with a damping ratio of at most 0.5, those with a damping ratio of at least 0.1 and at most 0.3, and those with a damping ratio of at least 0.01 and at most 0.1.
Still further embodiments include elastic suspension handles that elastically suspend loads and have a natural frequency that is less than the locomotive frequency of the object carrying the handle, such a less than the typical human walking frequency of 2 Hertz.
This summary is provided to introduce a selection of the concepts that are described in further detail in the detailed description and drawings contained herein. This summary is not intended to identify any primary or essential features of the claimed subject matter. Some or all of the described features may be present in the corresponding independent or dependent claims, but should not be construed to be a limitation unless expressly recited in a particular claim. Each embodiment described herein is not necessarily intended to address every object described herein, and each embodiment does not necessarily include each feature described. Other forms, embodiments, objects, advantages, benefits, features, and aspects of the present disclosure will become apparent to one of skill in the art from the detailed description and drawings contained herein. Moreover, the various apparatuses and methods described in this summary section, as well as elsewhere in this application, can be expressed as a large number of different combinations and subcombinations. All such useful, novel, and inventive combinations and subcombinations are contemplated herein, it being recognized that the explicit expression of each of these combinations is unnecessary.
Some of the figures shown herein may include dimensions or may have been created from scaled drawings. However, such dimensions, or the relative scaling within a figure, are by way of example, and not to be construed as limiting.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to one or more embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended; any alterations and further modifications of the described or illustrated embodiments, and any further applications of the principles of the disclosure as illustrated herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates. At least one embodiment of the disclosure is shown in great detail, although it will be apparent to those skilled in the relevant art that some features or some combinations of features may not be shown for the sake of clarity.
Any reference to “invention” within this document is a reference to an embodiment of a family of inventions, with no single embodiment including features that are necessarily included in all embodiments, unless otherwise stated. Furthermore, although there may be references to “advantages” provided by some embodiments, other embodiments may not include those same advantages, or may include different advantages. Any advantages described herein are not to be construed as limiting to any of the claims.
Specific quantities (spatial dimensions, temperatures, pressures, times, force, resistance, current, voltage, concentrations, wavelengths, frequencies, heat transfer coefficients, dimensionless parameters, etc.) may be used explicitly or implicitly herein, such specific quantities are presented as examples only and are approximate values unless otherwise indicated. Discussions pertaining to specific compositions of matter, if present, are presented as examples only and do not limit the applicability of other compositions of matter, especially other compositions of matter with similar properties, unless otherwise indicated.
Carrying loads during locomotion can be energetically costly. Load carrying has static and dynamic components and peak forces can be high due to dynamic loads. Compared to rigidly attached loads, elastically suspended loads, such as using a compliant spring, can reduce peak forces during locomotion, increase energy efficiency (especially for a walking or running person carrying a load), and reduce the forces acting on the load, which has advantages when carrying delicate items, such as babies, animals, and delicate equipment.
A double-mass coupled-oscillator model, such as the system depicted in
The equations of motion for the double-mass coupled-oscillator system are shown as follows.
Main mass M1 stance phase:
Load mass m2 stance and flight phase:
Where the parameters are as defined in Table 1.
Lift-off condition:
The parameter values M1=75 kg (main mass), K1=28,000 N/m (leg stiffness), and B1=950 Ns/m (leg damping) approximate those of an average human. The leg length forcing function L(t) used to simulate the effective springy-leg length when a person bends at the knee during locomotion is shown below.
L(t)=L0+A sin(ωt) (3)
The parameters I0=0.9 m (approximate unstretched leg length from foot to hip), A=0.025 m (amplitude of oscillation of the hip during locomotion, 5/2 cm), and ω=2π rad/s (approximate walking frequency, 1 Hz) were selected to approximate the motion of a person's center of mass during locomotion. One of ordinary skill can readily adapt this analysis for different walking frequencies by substituting the desired walking frequency in place of the 1 Hz (2π rad/s) that is used in the following paragraphs. For example, a more accurate approximation of the adult human walking frequency of 2 Hz (4π rad/s) may be substituted in for ω, while still other examples can use a frequency of locomotion of approximately 3 Hz (6π rad/s) to estimate the frequency for a running person. The load M2=25 kg is used to estimate a relatively heavy load (being one-third of the main mass M1), but other loads may also be analyzed.
Using these parameters, the system approximates a human walking with elastically-suspended loads. This model can provide valuable insight into locomotion with elastically-suspended loads from first principles.
The initial conditions of the simulation were adjusted for the system to achieve stable periodic motion. The effect of an elastically-suspended load versus a rigidly-attached load was determined by graphical and numerical comparison. The peak forces on the main mass M1 were calculated from the spring and damping forces acting on the main mass M1 as shown below.
Leg Spring Force=−K1(X1−(L0+A sin(ωt)))
Leg Damping Force=−B1({dot over (X)}1−ωA cos(ωt)))
Load Suspension Spring Force=−K2(X1−X2))
Load Suspension Damping Force=−B2({dot over (X)}1−{dot over (X)}2))
Peak Force on Main Mass M1=max(ΣFM
The energy cost of locomotion was estimated by determining the average positive power from the leg length forcing function required for the system to maintain a periodic motion at steady state. We only used the average positive power because we assume the leg length actuator cannot store and return energy for purposes of illustration.
P=FV
P=({dot over (X)}1−ωA cos(ωt)))(K1(X1−L0−A sin(ωt))+B1({dot over (X)}1−ωA cos(ωt))) (5)
Although presently not well understood, attempts have been made to understand the stability of the elastic-suspension handles to determine the effects of these handles on stability. While the analysis is ongoing, initial results appear to indicate that systems with elastic suspension handles can be rather stable, although potentially slightly less stable than systems with rigidly attached handles. Initial results also appear to indicate that elastic suspension handles may enhance stability, especially when the user is traversing rough terrain, such as when a user is carrying an elastically suspended load up or down stairs.
The stability of a system can be defined as the ability of a system to return to a stable limit cycle or equilibrium point after perturbation. To quantify the rate of recovery from a perturbation (the stability), a linearized version of the mapping function that maps all possible perturbations from one cycle to the next produces an n×n return map (the Jacobian), where n is the number of states. The eigenvalues of the n×n Jacobian matrix are stability values, or the percentage of the perturbation remaining after each cycle. For a discrete system, eigenvalues greater than one generally indicate that the cycle is unstable, eigenvalues equal to one generally indicate that the cycle is marginally stable, and eigenvalues less than one generally indicate that the cycle is stable. The stability of the system in this model was calculated by perturbing the initial conditions of the system (δx10, δ{dot over (x)}10, δx20, δ{dot over (x)}20), estimating the partial derivatives using finite differences for the mapping from the period x(p) to x(p+1), and calculating the eigenvalues of the resulting Jacobian matrix.
The suspension stiffness and damping parameters K2 and B2 were adjusted to find a parameter range such that the system with elastically-suspended loads exhibits reduced peak forces and reduced energy cost of locomotion compared to a rigidly attached load. The rigidly-attached load was simulated by setting the suspension parameters to large values (K2=10*K1 and B2=10*B1). For the given human parameters, the parameter range necessary for the system with elastically-suspended loads to exhibit both reduced peak forces and reduced energy cost of locomotion was K2<885 N/m. High suspension damping B2 reduces the effect of elastically-suspended loads because the motion of the load M2 is reduced, so the damping was kept low (B2<25 Ns/m). To illustrate the peak forces and energy cost in this low K2 region and compare them with those at higher K2 and B2 values, a parameter sweep of 25 N/m≦K2≦2000 N/m in increments of 25 N/m was chosen; B2 was simultaneously varied from 10 Ns/m to 50 Ns/m in increments of 0.5 Ns/m. The value of the suspension damping B2 was increased along with the suspension stiffness K2 to simulate how stiffer suspension springs may have larger damping values. Once the parameter range was established, the stability of the system over this range was calculated.
It was discovered that the peak forces and energy cost during locomotion with elastically-suspended loads are reduced for low K2 and B2 values compared to a rigidly-attached load. These values represent a load suspension with compliant springs and low damping. Low K2 values weakly-couple the motion of the elastically-suspended load M2 from the motion of the main mass M1. Weak-coupling corresponds to a maximum phase shift of approximately 180 degrees. This concept can be best viewed in the frequency domain with a Bode plot as depicted in
As can be seen in
Referring now to
The total peak forces and the energy cost during locomotion depend on the suspension damping B2. See
Increasing load M2 (
The stability of the system is somewhat reduced with an elastically-suspended load versus a rigidly-attached load over the low K2 and B2 parameter range in which the peak forces and energy cost of locomotion are reduced. See
For elastically-suspended loads to be effective, the motion of the load mass M2 should be weakly-coupled to the motion of the main mass M1. This requires a spring of sufficiently low stiffness K2 and low suspension damping B2. During periodic motion under these conditions, the load M2 oscillates with approximately the same amplitude as the main mass M1 and the motion of the load M2 is nearly 180 degrees out of phase with the motion of the main mass M1. In some embodiments, the compliant suspension stiffness K2 necessary to weakly-couple the load can be obtained with compliant coil springs or bungee cords and the damping B2 can be kept low by using low friction bearings and springs with low damping. Furthermore, in alternate embodiments where the static deflection of a load suspended with compliant springs is significant, large suspension spring travel is required.
It should be appreciated that the design objective for elastically-suspended loads is generally different than that of tuned vibration absorbers. The parameters of tuned vibration absorbers are adjusted such that the forcing function frequency ω is at the anti-resonance peak of the system to minimize the motion of the main mass M1. However, selecting a K2 value such that the leg length forcing function frequency ω is at the anti-resonance peak of the double-mass coupled-oscillator system is not desirable for some elastically suspended load embodiments. For the set of human walking parameters given above, the K2 value that adjusts the input frequency ω to the anti-resonance peak is 986 N/m. At this value, the motion of the main mass M1 is minimized, but the peak forces and energy cost of locomotion are increased, which may not be desirable in some embodiments of the present disclosure.
Reducing peak forces can be important in load carrying devices to reduce stress on humans, animals, and robots.
For a system with elastically-suspended load, the optimal value of the suspension stiffness that minimizes the total peak forces on the main mass M1 (e.g., K2=850 N/m) and an optimal value of the suspension stiffness that minimizes the energy cost during locomotion (e.g., K2=650 N/m) may be a different values. In these systems, the minimum total peak forces cannot simultaneously exist with the minimum energy cost during locomotion. This is a tradeoff inherent in the tuning of many systems with elastically-suspended loads. Some embodiments of the present disclosure minimize the energy cost of locomotion with some reduction in peak forces, which may have advantages over the embodiments that minimize peak forces while reducing the energy cost of locomotion.
Although minimal suspension damping B2 is generally desirable, it may be advantageous to have some damping in the system, such as a sufficient amount of damping to avoid detrimental resonance effects. For example, if the damping is too low, the resonance peak of the system can become significant and can potentially excite oscillations of the load M2, especially if the system is mistuned. This type of situation could reduce the effectiveness of elastically suspending a load and potentially cause damage to a compliant suspension system. In certain embodiments, some amount of damping B2 will be inherently present and advantages may be realized by minimizing the damping inherent in the system. In alternate embodiments, the damping ratio is at most 0.5. In other embodiments, the damping ratio is at least 0.1 and at most 0.3. In still further embodiments, the damping ratio is at least 0.01 and at most 0.1.
When walking with a standard backpack load, the mass-specific gross metabolic power increases curvilinearly with speed and is directly proportional to the load at any speed. The model results show the same trend when walking with a rigidly-attached load. When walking with an elastically-suspended load, the potential energy savings may increase with increasing load and speed. Furthermore, since changing the load M2 and locomotion frequency ω can shift the range of low K2 values sufficient to weakly-couple the load and increase the effectiveness of elastically-suspended loads, there exists an opportunity for the suspension stiffness K2 and damping B2 parameters of an elastically-suspended load to be dynamically tuned for optimal system performance based on knowledge of M2 and ω.
Preliminary analysis appears to indicate that the stability of a system with an elastically-suspended load may be somewhat reduced as compared to a rigidly-attached load over the low K2 and B2 parameter range. As such, a trade-off may exist for locomotion with elastically-suspended loads. A system with elastically-suspended loads can reduce the peak forces and peak power input during locomotion, but this may potentially be at the cost of slightly reduced stability. Although the reduction in stability may not be so significant that the system becomes unstable, the relative stability of a system with an elastically-suspended load appears to be marginally lower than a system with a rigidly-attached load.
Although the effects of elastically-suspended loads on stability are not fully understood, decreased stability can potentially have negative implications for the locomotion of systems with elastically-suspended loads, such as when traveling over rough terrain. If the relative stability of a system with an elastically-suspended load is reduced for locomotion over level terrain, the stability over rough terrain can be poor and can even result in locomotion failure. This may increase the difficulty of the control effort for a human or animal to maintain stable locomotion over rough terrain. However, as the terrain gets increasingly rough, the stability of a system with elastically-suspended loads appears to improve.
The maneuverability of a system is generally defined as a measure of how quickly a system can change direction, e.g., turn. Since increased maneuverability has been linked to decreased dynamic stability, elastically-suspended loads may increase the maneuverability of locomotion systems.
One can elastically-suspend a load on a human, animal, robot, or vehicle that has a vertical component of motion during locomotion. The motion of interest is generally in the vertical direction because the center of mass of humans, animals, and robots is displaced by some amount during locomotion. For instance, the center of mass (CoM) of a human is displaced by about 5-7 cm while walking. When a human, animal, or robot carries a load during locomotion, the load must undergo the same displacement as the center of mass (unless some actuation is used to control the load displacement, which costs energy). For such a rigidly-attached load, the human, animal, or robot must be able to lift the mass of the main body plus the mass of the load during every stride.
To elastically-suspend a load, one needs to couple a load to the main body with a spring. A spring (which may take different forms such as torsion springs, leaf springs, cantilevered springs, coil springs, volute springs, tension springs, air springs, compliant mechanism springs, etc.) can be used to achieve a phase difference of 90-180 degrees between the vertical motion of the load and the main body. With a spring at the interface, the main body and the load can be effectively decoupled (or “weakly-coupled”) from each other. Doing so can reduce the motion of the net center of mass of the system, reducing the amount of work required during each stride. Thus, the energy cost and peak forces of locomotion can be reduced. Moreover, since the vertical motion of the load can also be reduced, elastically-suspending a load can help protect sensitive packages inside the load. Depicted in
Depicted
By elastically-suspending a load, the handle increases the energy efficiency and decreases the peak forces during locomotion compared to a standard (rigid) handle. Both the gain in energy efficiency and the reduction in peak forces depend on the load. For increasing load, the relative energy efficiency gain increases and the relative reduction in peak forces decrease. Stated differently, increasing the load increases the effectiveness of elastically-suspended loads versus rigidly-attached load during locomotion.
Significant benefits can be achieved from elastically-suspending a load. For example, a backpack with a load suspension (27 kg load) was shown to reduce the energy cost of locomotion (increase the energy efficiency) by 6.2% and reduce the peak accelerative vertical force by 82% and the total peak vertical forces by 33% compared to a rigidly-attached load. Suspending a load (32% body mass) on a prototype robot with a weakly-damped elastic suspension system can reduce the energy cost (increased the energy efficiency) by up to 24%. Although a handle such as the one depicted in
Some embodiments include a compact handle mechanism. Since compliant springs are beneficial, a long suspension travel may be used to statically support a given load with linear springs (Hooke's Law). To accommodate the long suspension travel, the springs can be pre-stressed or rotation/torsion springs can be used. Rotational/torsion springs are particularly useful in some embodiments because they are compact and undergo rotational displacement instead of linear displacement. Various embodiments utilize various types of springs, such as elastic bands, coil springs, coiled metal watch springs, air springs, and/or compliant mechanisms.
Tuning of the springs can be useful. The double-mass coupled-oscillator model described above can help select the approximate spring stiffness required to realize, and to potentially optimize, the benefits of elastically-suspended loads.
The applications of the elastic handle are numerous. One embodiment includes a “universal” handle for elastic load suspension that can be used to pick up grocery bags, shopping bags, buckets, rugs, briefcases, laptop cases, purses, luggage, toolboxes, military cargo, salt bags, etc. In alternate embodiments, an “integrated” handle for elastic load suspension could be integrated into carrying cases, luggage, toolboxes, military cargo, baby seats/carriers, dog carriers, etc.
In still further embodiments, a weakly-coupled robot load suspension capable of elastically suspending loads inside of a robot (such as batteries, electronics, and fuel) as well as external loads. Such a suspension system can increase the energy efficiency and reduce the peak forces during robot locomotion compared to rigidly-attached loads. In one embodiment, the robot load suspension can use a linear spring and a rotational bell crank to change the direction of a suspension springs deflection. As such, the robot load suspension can utilize the length of a robot with a long horizontal suspension system rather than a tall vertical suspension system that could have a negative impact on the pitching dynamics of the robot during locomotion. This concept is particularly useful for robots that are long relative to their height.
In one embodiment, the elastic load suspension is attached to a hexapod robot as depicted in
The bell crank mechanism enables a load to be elastically suspended over the robot. The mechanism does not require a large amount of vertical space for the load to be statically supported and oscillate about the static equilibrium point. When the bell crank arm supporting the load is vertical, the elastic band does not support the load. As the bell crank arm supporting the load rotates toward the front of the robot, the elastic band supports an increasing proportion of the load. This results in a non-linear elastically-suspended load. For the small oscillations of a tuned elastically-suspended load that is nearly horizontal, the non-linear effect of the bell crank rotation is assumed to be negligible.
One aspect of embodiments of the present disclosure is the tuning of the elastic suspension system. Using, for example, a human that is walking or running carrying a load, the human's motion may be approximated by the action of a pogo stick. See
As previously mentioned, if a load can be elastically-suspended from the body with a compliant suspension, then the motion of the load can be decoupled from the motion of the body and reduce the peak forces and energetic cost of locomotion. Using a linear two degree-of-freedom vertical hopping model to investigate this phenomenon (see, e.g.,
A similar trend is observed with the peak dynamic forces on the body, but the tuning is different. As depicted in
Choosing such low suspension stiffness requires a large static deflection, which increases exponentially as the suspension stiffness is minimized (based on Hooke's law, F=kx). See
In some embodiments, the handle suspension is tuned for a given load such that the minimum effective linear static deflection is at least 2.5 inches and at most 18 inches. In other embodiments, the handle suspension is tuned for a given load such that the minimum effective linear static deflection is at least 4 inches and at most 10 inches. In still further embodiments, the handle suspension is tuned for a given load such that the minimum effective linear static deflection is approximately 5 inches. In some embodiments the extension of the load below the normal resting position of the handle may be at least 2.5 inches and at most 18 inches, at least 4 inches and at most 10 inches, or approximately 5 inches; while in other embodiments the effective spring length statically deflects at least 2.5 inches and at most 18 inches, at least 4 inches and at most 10 inches, or approximately 5 inches.
Different load masses may require different tuning. A 15 lb load will generally require one stiffness and a 30 lb load will generally require another stiffness. If the suspension is linear and a 15 lb load has 5 in of travel, then a 30 lb load could have 10 in of travel. If the 15 lb load instead has 10 in of travel, then the 30 lb load would have 20 in, which could be a problem for the mechanism to accommodate. As such, various embodiments tune the handle suspension for a particular load mass. Some embodiments may be able to accommodate only a certain range of loads (a typical range may include 15-30 lbs), although other embodiments incorporate a suspension with an adjustable tension that can accommodate multiple load masses, which may be accomplished manually or with an actuator.
Limiting the static load deflection of the handle spring can have adverse consequences. For example, if an elastic suspension mechanism results in a small static defection of the load, such as less than 2.5 inches, the natural frequency of the handle can inadvertently be higher than the natural frequency of locomotion and actually increase peak forces and decrease locomotive energy efficiency (increase locomotive energy cost).
Depicted in
Depicted in
Depicted in
Alternate embodiments of the present disclosure include an elastically-suspended satchel as a hip-supported load carrying device that can suspend a load with a compliant spring near the center of mass of a human, animal, or robot. Alternate embodiments can use linear spring deflection or rotational spring deflection, space saving advantages being realized with the latter. These embodiments It can increase the energy efficiency and reduce the peak forces during locomotion compared to a standard rigidly-attached satchel.
Alternate embodiments apply the concept of tuned elastically-suspended loads to vehicles. For large loads outside the optimal range of the vehicles suspension, additional elastic load suspension mechanisms can help improve the energy efficiency of the vehicles' motion.
Alternate embodiments include universal handles for carrying grocery/shopping bags, briefcases, laptop computer cases, purses, luggage, toolboxes, military cargo, etc. Still other embodiments include integrated handles for carrying briefcases, luggage, toolboxes, military cargo, baby seats/carriers, pet carriers, etc.
Still further embodiments utilize one or more torsion springs to suspend a load from a handle.
If there is some optimal range of load suspension stiffness values for different parameters of the locomotion system (load, speed, morphology), there is also an opportunity to dynamically tune the load suspension stiffness during locomotion. This can be accomplished with an actuator that can change the suspension stiffness during locomotion given a control signal input, maintaining the optimal load suspension stiffness.
The reference system used herein may refer generally to various directions (e.g., upper, lower, forward and rearward), which are merely offered to assist the reader in understanding the various embodiments of the disclosure and are not to be interpreted as limiting. Other reference systems may be used to describe various embodiments, such as referring to the direction of projectile movement as it exits the firearm as being up, down, rearward or any other direction.
While examples, one or more representative embodiments and specific forms of the disclosure have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive or limiting. The description of particular features in one embodiment does not imply that those particular features are necessarily limited to that one embodiment. Features of one embodiment may be used in combination with features of other embodiments as would be understood by one of ordinary skill in the art, whether or not explicitly described as such. One or more exemplary embodiments have been shown and described, and all changes and modifications that come within the spirit of the disclosure are desired to be protected.
Claims
1. A carrying handle, comprising:
- a grip portion;
- a connecting member for connecting the grip portion to a load; and
- a spring connected to the grip portion and to the connecting member, wherein the effective spring length statically deflects at least 2.5 and at most 18 inches when carrying the load.
2. The carrying handle of claim 1, wherein the effective spring length statically deflects at least 4 inches and at most 10 inches when carrying the load.
3. The carrying handle of claim 1, wherein the effective spring length statically deflects 5 inches when carrying the load.
4. The carrying handle of claim 1, wherein the spring is pretensioned and the physical displacement between the handle and the carried object is reduced.
5. The carrying handle of claim 1, wherein the natural frequency of the spring is less than 2 Hertz.
6. The carrying handle of claim 1, wherein the damping ratio of the carrying handle is at most 0.5.
7. The carrying handle of claim 1, wherein the stiffness of the spring is adjustable by the user.
8. The carrying handle of claim 1, wherein the spring is a nonlinear spring.
9. The carrying handle of claim 1, wherein the spring is a leaf spring, a torsion spring, a coil spring, an air spring, an elastic cord, an elastic band, or a compliant plastic mechanism.
10. The carrying handle of claim 1, comprising:
- a locking mechanism with at least two user selectable configurations including a rigid suspension configuration, wherein the spring is restrained from deflecting, and an elastic suspension configuration, wherein the spring deflects when carrying the load.
11. A method for carrying a load, comprising:
- extending the effective length of a spring connected to a handle and a load, the effective spring length extending at least 2.5 inches and at most 18 inches;
- suspending the load below the extended handle;
- lightly damping oscillations of the suspended load with a damping ratio equal to at most 0.5.
12. The method of claim 11, wherein said extending extends the effective length of the spring at least 4 and at most 10 inches.
13. The method of claim 11, wherein said extends the effective length of the spring 5 inches.
14. The method of claim 11, wherein said lightly damping is accomplished with a damping ratio equal to at most 0.1.
15. The method of claim 11, comprising:
- restricting non-vertical motion of the suspended load.
16. The method of claim 11, comprising:
- extending the load below the handle and reaching a static equilibrium point approximately 5 inches below the handle.
17. A method of manufacturing a handle, comprising:
- selecting an elastic member that will have an effective static deflection of at least 2.5 inches and at most 18 inches when a predetermined load is suspended by the elastic member;
- connecting the elastic member to a grip adapted for grasping; and
- connecting the elastic member to a load attachment portion, the load attachment portion including a mechanism for attaching to the predetermined load.
18. The method of claim 17, wherein said selecting includes selecting an elastic member that will have an effective static deflection of at least 4 inches and at most 10 inches when the predetermined load is suspended by the elastic member
19. The method of claim 17, wherein said selecting includes selecting an elastic member that will have an effective static deflection of approximately 5 inches when the predetermined load is suspended by the elastic member
20. The method of claim 17, comprising:
- selecting an elastic member that will have a damping ratio of at most 0.5 when connected to the grip and the load attachment portion and suspending the predetermined load.
Type: Application
Filed: Oct 10, 2012
Publication Date: Apr 25, 2013
Applicant: PURDUE RESEARCH FOUNDATION (West Lafayette, IN)
Inventor: Purdue Research Foundation (West Lafayette, IN)
Application Number: 13/648,994
International Classification: A45F 5/10 (20060101);