CN115776969A

CN115776969A - Assembly system

Info

Publication number: CN115776969A
Application number: CN202180043699.8A
Authority: CN
Inventors: 晴彦·哈里·浅田; 拉谢尔·霍夫曼
Original assignee: Massachusetts Institute of Technology
Current assignee: Massachusetts Institute of Technology
Priority date: 2020-04-20
Filing date: 2021-04-19
Publication date: 2023-03-10
Also published as: JP2023522105A; WO2021216473A8; WO2021216473A1

Abstract

An apparatus and method for positioning a first object into a beveled cavity of a second object is disclosed. In some embodiments, the first object is suspended from a plurality of flexible tethers such that the flexible tethers maintain the first object in an orientation suitable for insertion into the second object.

Description

Assembly system

Cross Reference to Related Applications

The benefit of U.S. provisional patent application serial No. 63/012,363, entitled "Apparatus and Method for Precision Assembly of Objects Suspended by Multiple Cables", filed 4/20/2020 by 35U.S. C. 119 (e), the entire contents of which are incorporated herein by reference.

Technical Field

The disclosed embodiments relate to assembly systems and methods, such as systems and methods for positioning objects using multiple tethers.

Background

When assembling objects in heavy industries (e.g., aerospace, shipbuilding, mining, etc.), heavy workpieces and subassemblies may need to be accurately positioned against other objects and/or structures. In general, precise positioning and/or mating of crane-suspended objects may require special training and/or experience, making typical object assembly highly dependent on skilled labor. Typically, the assembly may be performed by a worker who stands near the crane-suspended object and adjusts the position and orientation of the one or more objects by directly pushing and/or pulling the one or more objects, while adjusting the height of the crane.

Disclosure of Invention

According to one aspect, an assembly apparatus comprises: a support structure; a plurality of tethers suspended from the support structure, the plurality of tethers configured to suspend the first object from the support structure; and one or more actuators operatively coupled to at least one selected from the group consisting of a support structure and a plurality of tethers, the one or more actuators configured to lower a portion of the first object under the influence of gravity toward a cavity formed in a second object, the second object having a ramp formed along at least a portion of the cavity, and wherein the one or more actuators and the plurality of tethers are configured to control the lowering of the portion of the object such that the portion of the first object contacts and slides along the ramp as the portion of the first object is inserted into the cavity.

According to another aspect, a method of positioning an object in a cavity includes: a plurality of tethers suspending the first object to the assembly device; lowering a portion of the first object under the influence of gravity toward a cavity formed in a second object, the second object having a bevel formed along at least a portion of the cavity such that at least a portion of the first object is in contact with the bevel; sliding the portion of the first object along the ramp; and positioning the first object in the cavity of the second object.

It should be understood that the foregoing concepts, as well as the additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Furthermore, other advantages and novel features of the disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the drawings.

Drawings

Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated is typically represented by a like numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to enable those of ordinary skill in the art to understand the disclosure. In the drawings:

FIG. 1 is a front view of a passive assembly apparatus according to one illustrative embodiment;

FIG. 2A is a front view of a suspended object in contact with a sloped surface of a cavity of a stationary object, according to one illustrative embodiment;

FIG. 2B is a front view of a suspended object in point contact with one point of an inner wall of a cavity of a stationary object according to one illustrative embodiment;

FIG. 2C is a front view of a suspended object in two-point contact with an inner wall of a cavity of a stationary object, according to one illustrative embodiment;

FIG. 3A is a front view of an object suspended from a plurality of flexible tethers, according to an illustrative embodiment;

FIG. 3B is a front view of an object suspended from a plurality of flexible tethers, according to another illustrative embodiment;

FIG. 4 is a front view of an active assembly apparatus according to one illustrative embodiment;

FIG. 5 is a flow chart illustrating a method of passively positioning a first object in a cavity of a second object;

FIG. 6 is a flow chart illustrating a method of actively positioning a first object in a cavity of a second object;

FIG. 7 is a front view of an exemplary assembly apparatus, according to one illustrative embodiment;

FIG. 8 is a front view of an assembly apparatus according to an illustrative embodiment;

FIG. 9 is a graph illustrating the relationship between the coefficient of friction of the incline of a stationary object and the initial angle of the flexible tether of the assembly apparatus according to one experiment;

FIG. 10 is a graph showing an experimentally measured relationship between the initial angle of the flexible tether of the assembly apparatus and the depth at which two point contact between portions of the suspended object and the inner wall of the cavity of the stationary object can be achieved;

FIG. 11 is a graph showing experimentally measured relationships between travel depth and distance from the center of the suspended object and the center of the cavity;

FIG. 12 is a graph illustrating a relationship between a coefficient of friction of a slope of a stationary object and an initial angle of a flexible tether, according to one embodiment;

FIG. 13 is a graph showing a relationship between friction coefficients of slopes of stationary objects according to another embodiment;

FIG. 14 is a graph showing a relationship between friction coefficients of slopes of stationary objects according to still another embodiment;

FIG. 15A is a front view of an exemplary assembly apparatus, according to one illustrative embodiment;

FIG. 15B is a front view of the portion of the assembly device of FIG. 15A in contact with a surface and the force generated based on the location of the instantaneous center of rotation, according to one embodiment;

FIG. 15C is a front view of the portion of the assembly device of FIG. 15A in contact with a surface and the force generated based on the location of the instantaneous center of rotation according to one embodiment;

FIG. 15D is a front view of the portion of the assembly device of FIG. 15A in contact with a surface and the force generated based on the location of the instantaneous center of rotation, according to one embodiment; and

FIG. 15E is a front view of the portion of the assembly device of FIG. 15A in contact with a surface and the force generated based on the location of the instantaneous center of rotation, according to one embodiment.

Detailed Description

In heavy industries (e.g., aerospace, shipbuilding, mining, etc.), assembling objects is an important task. To assemble such objects, it may be necessary to accurately position and/or arrange heavy workpieces and/or subassemblies (e.g., workpieces and/or subassemblies that weigh more than 25 Kg) against other workpieces and/or subassemblies, which may prove to be a challenging task in many instances. In general, it can be particularly difficult to accurately position or mate the crane-suspended object. For example, a worker may assemble a heavy object by standing near a crane-suspended object and adjusting the position and/or orientation of the object by directly pushing and/or pulling the object while adjusting the height of the crane. The worker can stably push a specific portion of the object so that the orientation of the object can be aligned with the reference line without overshoot. In some cases, it can be particularly challenging to mate the suspended object with a second object, such as a stationary structure. The suspended object may be lowered in a specified position and orientation so that the object may be seated in the structure stably and with a high level of accuracy. This may involve a worker coordinating the crane to lower the suspended object while manipulating the position and/or orientation of the suspended object within the horizontal plane. Such precision assembly is employed in a variety of applications including turbine generators, marine and construction machinery and components thereof including large gear boxes and motors. To perform these operations quickly, workers may need to have years of experience and/or extensive training.

In view of the foregoing, the present inventors have recognized advantages associated with structures and systems that may help guide a suspended object to a desired position and/or orientation relative to a cavity of the object vertically below the suspended object when the objects are mated to one another. Thus, in some embodiments, the first suspended object may be suspended to the assembly device by a plurality of tethers. The first suspended object may then be lowered (e.g., by lowering the assembly apparatus) under the influence of gravity toward the second stationary object. In turn, the second stationary object may comprise a cavity for receiving the first suspended object having a ramp extending at least partially around a perimeter of the cavity. The suspended object may be roughly positioned such that a portion of the first suspended object is in contact with the sloped surface as the first suspended object is lowered toward the cavity. Once the first suspended mass is in contact with the ramp, the motion of the first suspended mass may be controlled such that the portion of the suspended mass contacting the ramp slides along the ramp in a direction that is directed inward toward the cavity at least partially along the ramp surface. The first suspended object may then be placed in the cavity of the second stationary object once the object is received in the cavity. For example, in some embodiments, the first hanging object may slide along a ramp toward the cavity before contacting the inner wall of the cavity at one point. After contacting the inner wall of the cavity at one point, the first suspended object may then contact the inner wall of the cavity at a second point, stabilizing the first object within the cavity before being further lowered into the cavity.

To achieve the above desired functionality, in some embodiments, an assembly apparatus according to the present disclosure may include a support structure and a plurality of flexible tethers extending from the support structure. The plurality of flexible tethers may be configured to suspend the first object from the flexible tethers in a desired orientation during insertion. Further, in some embodiments, the plurality of tethers may be configured to maintain a tension in each tether above a predetermined tension of each tether as the first suspended object is lowered toward the cavity of the second stationary object. This may be due to the tether having a predetermined length, according to a particular embodiment. However, in other embodiments, the tension in each of the tethers may be actively controlled by one or more actuators to maintain the tension in each tether above an associated predetermined tension such that the first suspended object is oriented substantially upright as it is lowered toward the cavity of the second stationary object and slides over the ramp surface into the cavity.

Depending on the desired application and object geometry, the systems and methods disclosed herein may be used to orient and position an object into a cavity within a two-dimensional reference plane and/or within a three-dimensional environment.

In view of the above, in some embodiments, it may be desirable to maintain the orientation of the first suspended object relative to the cavity of the second stationary object, which is disposed vertically below the first suspended object in two dimensions (e.g., a vertical dimension and a horizontal dimension) that are perpendicular to each other. In this case, the assembly device may comprise at least two flexible tethers, to which the first object may be suspended. The flexible tether may be used to maintain the first object in a desired orientation relative to the cavity as the first object is moved by the support structure and/or the tether. In particular, the support structure may raise or lower the first object while the tether maintains the orientation of the first object. Alternatively or additionally, the flexible tether may raise and/or lower the first object by changing the length of the tether, for example by extending and/or retracting the tether. In either case, the tether may be suitably tensioned (e.g., actively or passively tensioned, as described in more detail herein) to maintain a desired orientation of the first object relative to the lumen both prior to and during insertion.

As noted above, in some embodiments, it may be desirable to maintain the orientation of the first suspension in three dimensions with respect to three perpendicular axes. In this case, the assembly apparatus may include at least three flexible tethers to properly position and maintain the orientation of the first object in three-dimensional space (e.g., perpendicular X, Y, and Z axes). As described in further detail below, as the first hanging object is lowered into the cavity of the second object, the tension in the tether may be appropriately maintained and/or controlled to facilitate insertion of a portion of the first object into the cavity of the second object.

In various embodiments described herein, including the above-described embodiments, an assembly apparatus is described that includes two and three tethers. However, it should be understood that an assembly device according to the present disclosure may include any suitable number of tethers, may include four tethers, five tethers, six or more tethers, and/or may use any other suitable number of tethers depending on the application. However, using two tethers and three tethers to locate the object in the two-dimensional reference plane and three-dimensional space, respectively, may be advantageous because the increased number of tethers increases the constraint on the suspended object during assembly.

In some cases, the assembly device can perform the insertion process in any suitable manner (e.g., as described above). For example, in some embodiments, the insertion process is performed passively. In such embodiments, the assembly apparatus is configured such that the support structure moves to move the object, while the tether connected to the support structure maintains a desired tension under the influence of gravity to control the orientation of the object as it is inserted into the cavity. For example, in such embodiments, the first object may be suspended in a tether having a fixed length, the tether configured to control movement of the object relative to the cavity as the object is lowered. To lower the object, the support structure may be lowered, which lowers the tether and thus the first object. Depending on the application, such functionality may be performed using a crane, a movable gantry, or any other suitable system capable of controlling the vertical displacement of the support structure and the connection object.

Alternatively or in addition to the above, in some cases the assembly device can actively control the insertion process. In particular, in some embodiments, one or more actuators operatively coupled to the tethers may be used to actively control the tension and/or length associated with each of the flexible tethers while the assembly device inserts the first object into the cavity of the second object. For example, the tether may be connected to a displaceable arm, actuate a tether drum, or other actuation system capable of manipulating the length and/or tension of the tether extending from a support structure to which the tether is connected. In some embodiments, the length and/or tension of each tether of the plurality of tethers may be independently controlled, which may allow the assembly device to accommodate a wide range of applications. As will be appreciated by those skilled in the art, the tether may be actively controlled in any suitable manner during insertion depending on the application and as described in detail below.

In some cases, it may be desirable for the active control of each tether to be automated. For example, active control of the tether may be performed by the processor. In such embodiments, the one or more processors may be operatively coupled to the one or more actuators associated with the plurality of tethers to control operation of the one or more actuators. In particular, the one or more processors may be configured to control one or more parameters (e.g., length and/or tension) of the tether. In some embodiments, this may include active feedback control. For example, one or more sensors may be configured to sense the tension and/or length of each tether. In some embodiments, this may correspond to a separate sensor associated with each tether. In either case, the signals associated with the sensed parameters may be output to one or more processors. The one or more processors may then control the tension and/or length of the plurality of tethers based at least in part on the sensed parameters obtained from the one or more sensors.

The assembly device may employ any suitable type of sensor for sensing the above parameters. For example, the tension applied to the tethers of the assembly device may include one or more of a load cell, a force sensor, an extensometer, a strain gauge, and/or any other suitable sensor configured to sense the tension or load applied to an associated tether. With respect to the extension of one or more tethers, suitable sensors may include, but are not limited to, actuator encoders and/or any other suitable type of sensor configured to sense or otherwise determine the length of an associated tether extending from a corresponding support structure. Of course, while specific sensors are mentioned above, as will be appreciated by those skilled in the art, any suitable sensor or combination of sensors may be used with the disclosed system, as the present disclosure is not limited in this manner.

In some embodiments, the flexible tether may be angled in any suitable manner relative to a horizontal plane of the suspended object (e.g., a plane perpendicular to the direction of gravity). It should be appreciated that such a suitable angular range may be based at least in part on the geometry of the object suspended from the tether. In particular, the angle may be set such that the suspended object may be oriented to limit the degree to which the suspended object tilts as it moves toward (e.g., along a slope) and/or transitions into and toward a two-point contact state (e.g., as described in more detail herein) of the cavity of the stationary object. In some cases, configuring the tether at an appropriate angle may be used to prevent sticking and/or binding of the suspended object within the cavity and/or along the incline.

In view of the above, the angle may be set such that the flexible tether may momentarily rotate the suspended object about a predetermined rotation point to prevent binding and/or sticking. Without wishing to be bound by theory, the suspended object may tend to rotate about an instantaneous center of rotation defined by an imaginary point at which lines parallel and coaxial with the tether intersect one another. To prevent binding and/or stiction, the instantaneous center of rotation may be located a predetermined distance above or below a lower surface of the suspended object (e.g., a surface oriented toward a cavity of the stationary object).

Depending on the geometry of the suspended object, the angle of the tether with respect to a plane perpendicular to the direction of gravity may be any suitable value, depending on the desired application detailed below for several configurations. In particular, there may be upper and lower suitable ranges for the angles applied, since undesirable viscous and/or static behavior may occur over some range of tether angles. A particularly long suspended object may allow a larger suitable angular range, while a shorter object may have a smaller suitable angular range. The following provides exemplary ranges that may be used in some applications.

In some embodiments, the tether of the assembly device may exhibit an appropriate tether angle (e.g., an angle formed between the tether and a plane perpendicular to the direction of gravity) within the first operational angular range to avoid sticking and/or stationary behavior of the object during insertion. These tether angles may be less than or equal to 90 degrees, 85 degrees, 80 degrees, and/or any other suitable angle. Accordingly, the tether of the assembly device may have a suitable tether angle range that is greater than or equal to 75 degrees, 80 degrees, 85 degrees, and/or any other suitable angle. Combinations of the above ranges are contemplated, including but not limited to angles between 75 degrees and 90 degrees or angles equal to 75 degrees and 90 degrees. Of course, any suitable range of tether angles may be employed depending on the application.

Alternatively or additionally, in some embodiments, the tether of the assembly device may be arranged to operate within a second operational angular range to avoid viscous and static behaviour of the object during insertion. For example, depending on the geometry of the suspended object, suitable tether angle ranges may be less than or equal to 70 degrees, 60 degrees, 50 degrees, and/or any other suitable angle. Accordingly, the tether of the assembly device may have a tether angle that is greater than or equal to 1 degree, 10 degrees, 20 degrees, and/or another suitable angle. Combinations of the above ranges are contemplated, including but not limited to tether angles between 1 degree and 70 degrees or equal to 1 degree and 70 degrees. Of course, any suitable range of tether angles may be employed depending on the application.

In some embodiments, the tether angle may be set such that the tethers do not cross when the suspended object is suspended from the tether. Thus, tether angles between about 0 and 120 degrees or equal to 0 and 120 degrees are also contemplated in some embodiments.

In some embodiments, the appropriate tether angle range may depend on the total length of the suspended object. For example, in some embodiments including suspended objects having a relatively short overall length, tether angles less than or equal to 50 degrees or greater than or equal to 80 degrees may be employed. Alternatively or additionally, in some embodiments including suspended objects having a relatively long overall length, tether angles less than or equal to 80 degrees may be employed. Of course, embodiments having other suitable tether angles are also contemplated, depending on the geometry of the suspended object and/or other suitable factors.

It should be understood that while in some cases the angle of each of the plurality of tethers is the same, embodiments are also contemplated in which each tether takes on a different angle, as the present disclosure is not limited in this manner. Of course, any suitable combination of angles may be used depending on the application.

As described herein, the instantaneous center of rotation of the suspended object may be offset by a predetermined distance relative to the bottom surface of the suspended object in a direction parallel to the direction of gravity to prevent binding and/or stiction. Furthermore, in some embodiments, the instantaneous center of rotation of the object may be positioned such that it is above the center of mass of the suspended object or below the lowest surface of the suspended object with respect to the direction of gravity. In some embodiments, the offset may be a percentage of a maximum dimension of the suspended object parallel to the direction of gravity (e.g., a total length of the suspended object) before contacting the stationary object. In some embodiments, the offset distance may be greater than or equal to 50%, 60%, 70%, and/or another suitable percentage of the length of the suspended object parallel to the direction of gravity. Accordingly, the offset distance may be less than or equal to 200%, 100%, 90%, 80%, and/or any other suitable percentage of the maximum dimension of the suspended object parallel to the direction of gravity. Combinations of the above ranges are contemplated, including but not limited to percentages between 50% and 200% or equal to 50% and 200%. Of course, any suitable percentage of offset distance for the desired application may be employed, including smaller and larger percentages than those described above, depending on the application.

An assembly apparatus according to the present disclosure may include any suitable type of flexible tether configured to support an object to a support structure to which the tether is coupled. For example, the flexible tether may be a cable, wire, rope, chain, braid, combinations thereof, and/or any other suitable elongated flexible structure capable of suspending an object from a support structure. Thus, as will be understood by those skilled in the art, any suitable type or combination of types of flexible tethers may be employed depending on the application.

The assembly device according to the present disclosure may be used in any suitable application. For example, in some embodiments, the assembly apparatus may be attached to or otherwise be part of a gantry crane assembly, crane or other support structure for positioning a first object into a cavity of a second object. Alternatively or additionally, an assembly apparatus according to the present disclosure may be attached to or otherwise incorporated into an end effector for a robot. Thus, as will be understood by those skilled in the art, an assembly device according to the present disclosure may be used in any suitable application or combination of applications.

Turning to the drawings, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features and methods described with respect to these embodiments may be used alone and/or in any desired combination, as the present disclosure is not limited to the specific embodiments described herein.

FIG. 1 depicts an assembly apparatus 100 for positioning a suspended object 102 into a cavity 104 of a stationary object 106 according to one illustrative embodiment. The first object is positioned vertically above the cavity of the second object relative to the direction of gravity G applied to the system and the objects. Further, the portion of the first object oriented toward the cavity of the second object may be sized and shaped to be received in the cavity assembled therewith. The assembly apparatus 100 includes a support structure 110 to which two or more flexible tethers 108 are attached to the support structure 110. The two flexible tethers 108 are configured to attach to the suspended object 102 and support the suspended object 102 using any suitable connection to portions of the suspended object on opposite sides of the suspended object's center of gravity such that the suspended object 102 is suspended from the support structure 110 via the flexible tethers 108. Further, the support structure 110 can be moved (e.g., moved up and down) via an actuator 112 (e.g., a bridge crane) such that the support structure and supported object can be selectively lowered toward the cavity. In the depicted embodiment, the actuator is part of a gantry crane, such that the support structure can be moved in one or more horizontal directions relative to the depicted direction of gravity G to properly position the object relative to a cavity formed in a second object. Of course, it is also contemplated to include the assembly apparatus as part of another movable structure (e.g., a crane or other system) or a stationary structure.

In the illustrated embodiment, the assembly apparatus 100 is configured as a passive assembly system. In other words, the tension in the flexible tether 108 is maintained only by the gravitational force G and the length of the flexible tether 108 is fixed. Thus, when the actuator 112 moves the support structure 110 up and/or down, the suspended object 102 moves up and/or down relative to the underlying second object 106 and the cavity 104 formed therein, respectively. In particular, when the suspended object 102 is suspended from the flexible tether 108 and the flexible tether 108 remains taut (e.g., under gravity G), the suspended object 102 moves an equal distance upward and/or downward as the support structure 110 moves a distance upward and/or downward.

In this manner, the assembly apparatus 100 may lower the suspended object 102 toward the cavity 104 of the stationary object 106 while the length and tension of the tether 108 is maintained under the influence of gravity G. Further, the stationary object 106 includes features that can help guide a corresponding portion of the suspended object 102 into the cavity 104 during insertion. In particular, the chamfer 114 may be formed in the second object such that a chamfer corresponding to an inclined surface extending between the upper surface of the object and the inner surface of the cavity may extend at least partially, and in some cases completely, around an upper opening of the cavity 104 oriented toward and configured to receive a corresponding portion of the suspended object 102 into the cavity 104.

The interaction between the ramp 114 and the portion of the suspended object 102 contacting the ramp may help guide a portion of the suspended object into the cavity. For example, fig. 2A illustrates the suspended object 102 in the following positions: wherein the lower portion of the suspended object 102 first comes into contact with a portion of the ramp 114 that is below the portion of the object to be inserted into the cavity. When the suspended object 102 is in contact with the ramp 114, the force distribution between the flexible tethers 108 may change, resulting in a change in the angle of the associated tether as the orientation of the suspended object changes as the suspended object tilts to one side. At the same time, by appropriately controlling the length, angular orientation, and/or force applied to a given object, the portion of the suspended object 102 that is in contact with the ramp may slide along the ramp surface toward the cavity 104. In some cases, each of the tethers may be held in tension during this initial contact and sliding with a non-zero tension applied to each tether, in which case the suspended object 102 may act as if it were connected to the support structure 110 through a rigid linkage. For example, in the system shown in fig. 1A, the suspended object may move and rotate as if it were attached to the support structure by a rigid four-bar linkage, where the object itself acts as one of the linkages. However, embodiments are also contemplated in which one or more tethers may be relaxed, i.e., apply approximately zero tension. In either case, the suspended object 102 may be directed toward the cavity 104 by the ramp 114 and the flexible tether 108 such that the overall direction of motion of the portion of the suspended object 102 in contact with the ramp is at least partially oriented inward toward the cavity 104 of the stationary object 106, which may correspond to the contacting portion of the suspended object sliding inward toward the cavity along the ramp surface.

As described above, and as illustrated in fig. 2A-2C, the suspended object 102 may be placed in a final position within the cavity 104 by sliding along the surface of the ramp 114 into the cavity 104. In particular, as shown in fig. 2A, when the suspended object 102 contacts the sloped surface 114, the suspended object 102 slides along the sloped surface 114 until at least a portion of the suspended object 102 enters the cavity 104. As shown in fig. 2B, the suspended object 102 may initially contact the inner wall of the cavity 104 at a single point. As the suspended object 102 continues to be lowered into the cavity 104 (e.g., by lowering the support structure 110), the suspended object 102 may then contact the inner wall of the cavity 104 at two points, as shown in fig. 2C. Once the suspended object 102 is in contact with the cavity 104 at two points, the reaction force provided by the inner wall of the cavity 104 may be used to provide two points of orientation and insertion that constrain the portion of the suspended object to be inserted into the cavity. The cavity and corresponding portion of the suspended object may be sized and shaped to allow the object to slide into the cavity without binding while the suspended object continues to be lowered for insertion after the two-point contact engagement occurs. This may allow the suspended object 102 to be positioned in a final desired location within the cavity 104.

Once the suspended object 102 achieves a two-point contact state (e.g., as described herein), one of the flexible tethers 108 may relax while the other flexible tether 108 remains taut. Thus, the combination of the reaction force from the inner wall of the cavity 104 and the tension in the remaining taut tether may be used to control the lowering of the suspended object 102 into the cavity 104 until the suspended object 102 achieves a desired position within the cavity 104. In a satisfactory embodiment, tension is maintained in the remaining taut tether due to gravity G acting on the tether.

Alternatively or additionally, in some embodiments, the flexible tether 108 may be actively controlled (e.g., as described in more detail herein). In such embodiments, the one or more actuators may actively control the tension in the flexible tether 108 when the two-point contact condition is achieved so that the suspended object 102 may move toward a desired orientation. In such embodiments, the tension in the flexible tethers 108 may be controlled together or separately depending on the application. In some embodiments, the assembly device 100 may include the following features: this feature allows the assembly apparatus 100 to hold the hanging object 102 in a generally upright position when the hanging object 102 is inserted into the cavity 104. In particular, the flexible tether 108 may be used to minimize the angle between the longitudinal axis of the suspended object 102 relative to the vertical axis a during insertion. For example, as shown in fig. 2A, the suspended object may be generally in-line with the vertical axis a (e.g., when the flexible tether 108 remains taut under the force of gravity G). However, as shown in fig. 2B, when the suspended object 102 slides along the slope 114, the suspended object 102 may be angularly displaced relative to the central axis a by, for example, a first angle α 1. Furthermore, the suspended object 102 may be angularly displaced by a second angle α 2 with respect to the central axis a during final insertion into the cavity. The flexible tether 108 may be configured to orient the suspended object 102 such that the angular displacement of the suspended object 102 remains less than a threshold angle to facilitate sliding of the object along a sloped surface and insertion into a cavity without binding as described above.

To help avoid binding during insertion of a portion of an object into the cavity, the flexible tether may further be used to maintain the suspended object 102 in the following orientation: such that the suspended object 102 may fit within the cavity 104 when the suspended object 102 is lowered into the cavity 104. In particular, the flexible tether 108 may maintain the suspended object 102 in the following orientation: such that the horizontal lateral dimension of the suspended object 102 is less than or equal to the horizontal lateral dimension of the opening of the cavity 104 as the suspended object 102 slides along the ramp 114 and/or enters the opening of the cavity 104 oriented toward the suspended object. In particular, in the ramp contact position shown in FIG. 2A, the horizontal lateral dimension H1-A of the suspended object 102 is less than or equal to the horizontal lateral dimension H2 of the cavity 104. Relatedly, in the one-point contact position shown in FIG. 2B, the horizontal transverse dimension H1-B of the suspended mass 102 is less than or equal to the horizontal transverse dimension H2 of the cavity 104, such that a desired portion of the suspended mass can be inserted into the opening of the cavity. Further, in the two-point contact position shown in FIG. 2C, the horizontal lateral dimension H1-C of the suspended object 102 is less than or equal to the horizontal lateral dimension H2 of the cavity 104.

While the above considerations have been described with respect to a passive system having a tether that is not actively actuated, these concepts for facilitating partial sliding of a contact ramp of an object and eventual insertion into a cavity may be applicable to all embodiments described herein. Accordingly, actively controlled assembly devices may also be suitably controlled to provide the above-described functionality, as the present disclosure is not limited in this manner.

As will be appreciated from the above, the suspended object 102 may rotate (e.g., angularly displace) as the suspended object 102 contacts the surface of the ramp 114 and slides over the surface of the ramp 114 to reach a final position in the cavity 104. Such rotation may occur about an instantaneous center of rotation P1, which may be related to a corresponding angle of the flexible tether 108 relative to the suspended object 102, see P1 and P2 in fig. 3A-3B. The instantaneous center of rotation may correspond to an imaginary point at which lines parallel and coaxial with the tether intersect each other. Depending on the orientation of the tether, the instantaneous center of rotation may be above, below, or coincident with the bottom surface of the suspended object. In particular, in the configuration depicted in fig. 3A, a line coaxial with the flexible tether 108 intersects at a point P1, which point P1 may be positioned vertically below a bottom surface of the suspended object oriented toward a cavity of another object. Thus, the suspended object 102 will tend to rotate about point P1. Relatedly, in the configuration shown in fig. 3B, a line coaxial with flexible tether 108 intersects at point P2. Thus, the suspended object 102 will tend to rotate about point P2.

As previously described, in some cases, it may be desirable for the tether to be oriented within a particular angular range such that the instantaneous center of rotation of the object may be offset some predetermined distance relative to the bottom surface of the object to facilitate sliding contact of the object with the corresponding ramp and insertion into the cavity of the second object. For example, points P1 and P2 may be selected such that the respective suspended object in each figure may be properly oriented to fit within the corresponding cavity. In particular, the suspended object 102 may be oriented to fit within the cavity when the points P1, P2 are outside the lower regions a-b of the object. Thus, as shown in the figures, the pivot points P1, P2 may be positioned vertically above or below the lower regions a-b of the object.

Without wishing to be bound by theory, the position of the instantaneous centers of rotation P1, P2 of the suspended objects relative to the depicted regions a-b may be a function of the angle between the flexible tether 108 and the portion of the suspended object to which the tether is connected and the length of the suspended object 102 relative to a vertical direction parallel to the local gravity direction G. For example, in the configuration shown in FIG. 3A, the suspended mass 102 has a relatively small length L1, and the regions a-b extend along a majority of the length L1. Accordingly, the angle θ 1 between the flexible tether 108 and a horizontal plane perpendicular to the direction of gravity may be set relatively large (e.g., close to 90 degrees or another suitable angle as detailed above) such that the pivot point P1 falls outside of the areas a-b. Relatedly, in the configuration shown in fig. 3B, the suspended object 102 has a relatively long length L2 in the vertical direction, and the regions a-B extend along only a small portion of the length L2. Thus, the angle θ 2 between the flexible tether 108 and the horizontal plane may be set to various suitable values such that the pivot point P2 falls outside of the areas a-b. In particular, in the embodiment shown in FIG. 3B, the angle θ 2 is set relatively small such that the pivot point P2 is vertically above the areas a-B.

While the above embodiments show static tether lengths, it should be understood that tethers having lengths and/or angles that dynamically change during operation using one or more actuators are also contemplated. Thus, the discussion above relating to the instantaneous center of rotation and corresponding relationships may be applicable to both passively and actively actuated assembly devices, as the disclosure is not so limited.

Alternatively or in addition to the above, in some embodiments, the assembly device 100 includes features that allow for active control of one or more parameters of the flexible tether 108. For example, as shown in fig. 4, the assembly device may include one or more actuators 118 depicted as actuating arms configured to actively control the flexible tether 108. In particular, the actuator 118 can control the extension and retraction of the flexible tether 108 relative to the support structure 110 to which the actuator and tether are coupled. Thus, the actuator may be used to lower or raise the suspended object 102 relative to the support structure.

As described above, in some cases, it may be desirable to maintain a predetermined tension applied to a plurality of tethers for supporting an object as the object is lowered into a corresponding cavity. Accordingly, in some embodiments, the assembly apparatus 100 may include a plurality of sensors 116 configured to sense the tension and/or extension of the tether 108. In the depicted embodiment, the sensor is depicted as a sensor for positioning in line with or attached to the tether. Regardless of the particular configuration, the plurality of sensors may be operatively coupled to a processor 120 configured to control the one or more actuators 118, such that the sensors may output one or more sensed parameters to the processor. The processor may be operatively coupled with an associated non-transitory processor-readable memory comprising processor-executable instructions that, when executed by the processor, may perform any of the methods disclosed herein. The processor 120 may control the one or more actuators 118 based at least in part on one or more parameters sensed by the sensors. The processor 120 may then command the actuator to perform one or more functions on the flexible tether 108. For example, as the suspended object 102 is lowered relative to the support structure 110, the actuators may be controlled to maintain the tension in each tether greater than or equal to a predetermined tension. For example, the tethers may extend relative to the support structure while maintaining tension in each of the tethers, or the tethers may be operable to maintain a desired tension in each of the tethers while the support structure is lowered. In either case, during insertion of the object into the cavity, the suspended object may be lowered toward the cavity while maintaining tension in each of the tethers. However, embodiments are also contemplated that allow one or more of the tethers to relax during the insertion process, as the present disclosure is not so limited.

Fig. 5 depicts one embodiment that may be implemented as a method of positioning a first object into a cavity of a second object using an assembly apparatus, the method including a passive operation in which a tether length may be secured as the object is lowered toward a cavity of the object that includes a ramp extending at least partially around the cavity. In fig. 5, at step 500, a first object is suspended at a flexible tether of an assembly device in a desired orientation and horizontal position relative to a cavity of an object below the suspended object such that a portion of the suspended object inserted into the cavity is generally positioned and oriented toward the cavity. Once the object is suspended in the desired orientation and position, the object is lowered at step 502 until the object contacts the sloped surface of the cavity. Then, at step 504, a flexible tether (e.g., tension) facilitates rotation of the object and sliding of the portion of the suspended first object in contact with the ramp toward the cavity until the object is seated in the cavity. Finally, at step 506, the first object is slid over the surface of the ramp such that the object makes a first contact with one or more interior surfaces of the cavity before sliding to a desired final position within the cavity, and then makes a second contact. In such a passive arrangement, operation of the system may simply comprise lowering the following support structure: the tether extends from the support structure, and the overall configuration of the tether and object may help ensure that the object slides properly over various surfaces during insertion without binding, sticking, or moving in an undesirable direction.

FIG. 6 is a flow chart illustrating an exemplary method of actively controlling tension applied to a tether of a first suspended object when the first object is inserted into a cavity of a second object disposed vertically below the first object with respect to a direction of gravity. Similar to the embodiments described above, at step 600, the assembly device may be used to position and orient a first object, while suspended from the flexible tether, toward a corresponding cavity formed in a second object underlying the first object. This may be done manually and/or the support structure of the apparatus may be moved to a desired position and orientation using one or more corresponding actuators, as the present disclosure is not limited to how the first object is positioned and oriented relative to the second object. In either case, one or more actuators of the assembly device may be suitably controlled to extend (i.e., lengthen) the flexible tether to lower the first object toward the second object at step 602. As the first object lowers, tension in each of the tethers may be sensed at 604 such that a force-based control loop may be implemented to control the actuator associated with the tether. For example, in some embodiments, an actuator may be operated to extend an associated tether as long as the sensed tension in the tether is greater than or equal to a predetermined threshold. Accordingly, extension of a particular tether may be stopped, and in some cases, the tether may be retracted when the sensed tension is less than a predetermined threshold. In this manner, tension may be maintained in each of the flexible tethers as the object is lowered into the cavity, at 606. Also, this may help facilitate sliding of the portion of the first hanging object in contact with the sloped surface around the cavity towards the cavity and subsequent insertion of this portion of the first hanging object into the cavity.

Example 1: conditions for success of insertion without relaxation/without stickiness

Referring to fig. 15A, and without wishing to be bound by theory, in the depicted embodiment, the suspended object 102 is held by only two tethers 108. Thus, in the depicted embodiment, neither flexible tether 108 is slack (e.g., by angling the tethers so that each tether does not fall within regions a-B, as shown in fig. 3A-3B).

Without wishing to be bound by theory, under such "no-slack" conditions, the quasi-static motion of the suspended object 102 may be kinematically determined. Since both flexible tethers 108 are tensioned, the flexible tethers 108 may be considered a pair of rigid linkages. The support structure 100, the two tensioned flexible tethers 108, and the suspended object 102 form a four-bar linkage having only one degree of freedom in a vertical plane.

Fig. 7 and 15A show the insertion of such a suspended object 102 in the "no slack" condition described above. When the suspended object 102 is placed on the surface of the ramp 114, the suspended object 102 is constrained from contact with the ramp 114. Without wishing to be bound by theory, the position and orientation of the suspended object may be geometrically determined. As the support structure 110 is lowered, the position and orientation of the suspended object 102 may vary relative to the height of the support structure 110. After reaching the bottom edge of the cavity 104, the suspended object 102 may contact the edge of the cavity 114 at its side, making a point contact with a portion of the cavity 104. Without wishing to be bound by theory, in a point contact state, the position and orientation of the suspended object 102 may be determined kinematically. This continues until the suspended object 102 comes into two-point contact with the inner wall of the cavity 104, thereby achieving a two-point contact state. In a two-point contact condition, the suspended object 102 may be constrained on at least two sides of the cavity 104. Once the suspended object 102 is so constrained, the four-bar linkage is no longer formed. Without wishing to be bound by theory, in this case, the at least one flexible tether 108 may relax to satisfy the constraint of two-point contact. In this case, the unidirectional nature of the tension in the flexible tethers (e.g., the ability of the flexible tethers 108 to be tensioned by gravity) causes the tension in one or more of the flexible tethers 108 to release so that the suspended object 102 may not be over-constrained.

In the embodiment shown in fig. 7 and 15A, the "no slack" condition described above may be maintained throughout the insertion process until two point contact occurs, such that kinematic control of the motion of the suspended object 102 may be performed, as detailed above. By using an appropriate tether angle phi ₁ 、φ ₂ And tether attachment locations such that the instantaneous center of rotation P3 can be located away from the regions a-b, the suspended object 102 can be guided through a quasi-static process to achieve a two point contact condition at a depth within the cavity 104 sufficient for successful insertion.

This "no slack" condition can be satisfied over two ranges of tether orientations: small angles and large angles. In some cases, the use of a medium angle may result in the instantaneous center of rotation P3 falling within regions a-b, thereby violating the "no slack" condition.

Without wishing to be bound by theory, the selection of the tether angle may depend on the size of the suspended object 102. Fig. 3A-3B illustrate two such examples. If the suspended object 102 has a relatively short overall length L1, a large tether angle θ 1 may be employed, for example, to position the instantaneous center of rotation of the suspended object 102 below the regions a-b. On the other hand, if the suspended object 102 has a relatively long overall length L2, a smaller tether angle θ 2 may be employed, for example, to position the instantaneous center of rotation of the suspended object 102 above the regions a-b.

Turning to the insertion process, it may be desirable to prevent sticking of the suspended object 102 to the surface of the ramp 114. To control this fact, the inventors first considered the conditions required to glue the suspended object 102 to the surface of the slope 114. This may occur at the moment a portion of the suspended object 102 contacts the surface of the ramp 114 or as the suspended object 102 slides along the ramp 114. When the suspended mass 102 sticks to the surface of the ramp 114, the suspended mass 102 may lose two degrees of freedom. Without wishing to be bound by theory, in this case the suspended object 102 may only rotate around the contact point, which means that at least one tether is slack. Alternatively, if the flexible tether 108 is set at an appropriate angle such that the instantaneous center of rotation P3 does not fall within regions a-b, the suspended object 102 may not stick to the surface of the ramp 114 during insertion.

Using the parameter d defined in fig. 7, the slack-free condition with respect to the cable angle is given by the following equation:

without wishing to be bound by theory, the above equation may be used to determine two sets of tether angle ranges that may be associated with: stick on the surface of the ramp 114 during insertion and slide along the surface of the ramp 114 during insertion. Without wishing to be bound by theory, the static coefficient of friction may be used to determine the viscosity at the first contact with the ramp 114 and the dynamic coefficient of friction may be used when sliding down the ramp 114. A similar equation can be derived to determine the viscous condition during a point contact.

It should be noted, however, that the "no stick" condition described above alone does not guarantee that the suspended object 102 slides down the ramp 114. The suspended object 102 may rest on the sloped surface under certain kinematic conditions. For example, the case (B) shown in fig. 15B shows a case where the suspended object 102 may not slide but stay on the inclined surface 114.

In the configuration of case (B) of fig. 15B, the instantaneous center of rotation P3-B is located at the end of the suspended object 102 where the extensions of the two tethers 108 intersect. Without wishing to be bound by theory, it is assumed that the left corner of the suspended object 102, point a in fig. 7, contacts the bevel. When the suspended object 102 rotates around P3-B, point A moves upward. If this upward movement is equal to the downward movement of the support structure 110, the two displacements cancel and the suspended object 102 may not slide but remain stationary on the inclined surface 114. As shown in fig. 15A, this resting behavior may be a function of tether angle, the relative position of point a with respect to the instantaneous center of rotation, and/or the ramp angle a. Other conditions are determined with respect to the location of the instantaneous center of rotation P3-C located slightly above the bottom surface of the object in FIG. 15C, the instantaneous center of rotation P3-D located at a greater distance above the bottom surface of the object in FIG. 15D, and the instantaneous center of rotation P3-E at a location below the bottom surface of the object in FIG. 15E. As can be seen in these figures, the position of the instantaneous centre of rotation at a large distance above and below the bottom surface of the part of the object to be inserted into the cavity may result in a rotation of the part in contact with the bevel, which is directed towards the inside of the bevel where the cavity is located. Thus, the tether of the assembly device may be suitably configured and/or controlled such that the instantaneous center of rotation of the object may be suitably positioned to provide sliding movement of the portion of the object in contact with the ramp surface toward the opening of the cavity.

Without wishing to be bound by theory, it may be desirable for the suspended object 102 to slide along the ramp 114 if the "no-stick" and "no-rest" conditions described above are met.

After the suspended mass 102 passes over the ramp 114, the opposite side of the bottom surface of the suspended mass 102 (e.g., point B in fig. 7) may clear the width of the cavity 104 (e.g., H2 in fig. 2A-2C). Without wishing to be bound by theory, a four-bar linkage analysis may be employed to estimate the tilt angle of the suspended object 102 at the point where the suspended object 102 has reached the end of the ramp 114 and just prior to transitioning to the one-point contact state described herein. Without wishing to be bound by theory, as described by the following equation, if the predicted tilt angle of the suspended object 102 satisfies the specified constraint, the opposite sides of the bottom surface of the suspended object 102 can clear the corresponding edges of the cavity 104, as shown in fig. 7.

Subsequently, the suspended object 102 may reach a two-point contact state when at least opposite sides of the bottom surface of the suspended object 102 contact corresponding edges of the cavity 104. Without wishing to be bound by theory, the depth of the first two-point contact location may determine whether the suspended object 102 sticks inside the cavity 104, e.g., becomes wedged within the cavity 104. When the depth of the first two-point contact location is sufficiently deep within the cavity 104, wedging is unlikely to occur. Depending on the given geometry of the suspended object 102, certain tether angles may create a deeper depth of the first two-point contact location than other tether angles, making wedging less likely to occur. Such parameters may be selected so that the depth of the first two-point contact location is as deep as possible. Without wishing to be bound by theory, the depth of the first two-point contact location may be determined kinematically and geometrically.

Example 2: experimental verification

The analysis results associated with embodiments of the apparatus and methods disclosed herein are validated through experiments using both 2D and 3D scale models. For example, as shown in FIG. 8, a steel pin 126 (. 76 kg) is made to slide into a steel bore 132 having a bevel angle of 45 degrees. To avoid the non-linearity associated with sharp edges, the bottom corners of the pins 126 are given 0.6mm fillets. The pin 126 is connected to the mounting system via a low tension polyester cord 134 and the mounting system is attached to the linear guide 122 powered by the lead screw. A lune tag is attached to the mounting system, the pin 126 and the hole 132 to provide relative position data for calculation and to provide the angle of inclination of the pin. The indicator LED128 provides a trigger as to when a two-point contact condition is achieved (e.g., as described in more detail herein). Various types of materials are disposed on the ramp surface to change the coefficient of friction of the interaction between the pin and the ramp (e.g., material 130). The coefficient of friction is measured by placing a piece of material 130 on a steel block and resting the pin 126 on top of the surface. The angle of the block is raised until the pin 126 begins to slide along the surface. The angle at which sliding starts to occur is measured as the friction coefficient angle fs, where m = tan (fs). In this experiment, the length L of the pin 126 was set to 127mm, and the width d of the pin 126 was set to 50.8mm. This is achievedOutside, the bevel angle α is set to 45 degrees and the lengths l1, l2 of the flexible tether 134 are set to 203.2mm. Diameter D of the hole _h Is set to 51.82mm, which means that the clearance between the pin 126 and the hole is 1.02mm.

First, an experiment was conducted using three different coefficients of friction to verify successful slope intersection of the pin 126 when the flexible tether angle is in both the allowable region (e.g., such that the pivot point is outside of the region a-B, as described above with respect to fig. 3A-3B) and the unallowable region (e.g., such that the pivot point is within the region a-B, as described above with respect to fig. 3A-3B). As shown in fig. 9, the allowable initial angular range sharply decreases as the friction coefficient of the pin bore system increases. This experiment verifies that the pin 126 will slide within the allowable region.

Second, experiments were conducted comparing quasi-static bevel intersection simulation with actual pin crossing of the bevel under different initial pin level errors. Returning to FIG. 7, 1.27mm, 2.54mm and 5.08mm e were tested ₀ Values representing 2.5%, 5% and 10% of the diameter of the test pin, respectively. As shown in fig. 10, the data points indicate experimentally measured data, and the lines indicate predicted values from the simulation. A Root Mean Square Error (RMSE) between the measurement and the prediction is calculated. For horizontal error e ₀ =1:27mm, RMSE 0.5 degrees for e ₀ =2:54mm, RMSE 1 degree and for e ₀ =5:08mm, RMSE 2.4 degrees. This indicates that kinematic analysis can be used to predict that the final angle of the pin at the end of the ramp intersection is within 2.4 degrees for substantially all ranges of flexible tether angles.

Third, experiments were conducted in which the depth at the first two-point contact was measured based on different horizontal displacement errors of the pin and different flexible tether installation angles (e.g., as part of the trajectory associated with insertion, as described herein). A root mean square error between the measurement and the prediction is calculated. For e ₀ Horizontal error of =1 ₀ 4.2mm for rmse, and for e =2 ₀ =5, 08mm, rmse 8.6mm. This indicates the maximum amount that can be expected to be experienced for the pinHorizontal displacement error, a kinematic model may be used to predict that the first two-point contact depth is within 7.5% of the pin length. As shown in fig. 10, the depth/, associated with achieving two-point contact, decreases as the flexible tether angle increases. Further, as shown in fig. 10, the depth/, increases as the flexible tether angle approaches 90 degrees. This means that in order to configure the assembly device to insert pins such that a suitable two-point contact depth/, the flexible tether angle may be as small as possible (e.g., as shown in fig. 3B) or as close to 90 degrees as possible (e.g., as shown in fig. 3A).

Fourth, additional tests were performed using a 3D setup, as shown in fig. 11, including a 3.5kg aluminum round pin 101.7mm in diameter and 152.4mm long, an aluminum hole having an inner diameter of 101.85mm, low tensile polyester cords 457mm and 609.6mm long, and a mounting plate 203.2mm in diameter.

The test results depicted in fig. 11 indicate that for certain cable angles, the pin did not successfully clear the ramp and enter the hole. The lines depict travel trajectories where the cable installation angle is inside the disallowed region predicted for a particular pin geometry (e.g., regions a-B as shown in fig. 3A-3B). In these cases, the pin may tip forward and topple. Thus, fig. 11 shows the minimal variation in the distance from the center of the pin to the center of the hole and the depth of the pin within the hole in such a region. In particular, pin insertion was found to be successful when the flexible tether was outside of this range, particularly when the flexible tether was mounted at 76 degrees and/or 38 degrees relative to horizontal.

Example 3: study of parameters

Without wishing to be bound by theory, in some cases, the mechanical behavior of a suspended object, such as a pin, may be determined by applying the kinematic principles associated with a four-bar linkage. In particular, the effect of varying the length L of the suspended object 102, the width d of the suspended object 102, and the slope angle α was investigated. The trajectory of the suspended object 102 with varying geometric parameters and varying initial cable placement angles is determined and the instantaneous slope at the point of first contact with the ramp 114 is calculated. This configuration is considered permissible if the slope of the instantaneous trajectory facilitates sliding of the suspended object 102 down the incline. The results of the parametric study are depicted in fig. 12 to 14.

The inventors have observed that as the length L of the suspended mass 102 increases, the area where the pin will come to rest increases and the area where stiction may occur shifts towards areas of higher cable angles. Thus, the inventors understand that a small cable angle may be associated with insertion success (e.g., as shown in fig. 3B). Furthermore, the inventors have observed that as the width of the suspended mass 102 increases, the area where stiction may occur increases, while the area where the suspended mass 102 may be stationary appears to remain approximately the same. In addition, the inventors have observed that as the ramp angle α becomes less steep, the range of effective mounting configurations decreases.

The above-described implementations of the techniques described herein may be implemented in any of a variety of ways. For example, embodiments may be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer device or distributed among multiple computer devices. Such processors may be implemented as integrated circuits, wherein one or more of the integrated circuit components comprise commercially available integrated circuit components known in the art as, for example, a CPU chip, a GPU chip, a microprocessor, a microcontroller, or a coprocessor. Alternatively, the processor may be implemented in a custom circuit such as an ASIC or a semi-custom circuit resulting from configuring a programmable logic device. As yet another alternative, whether commercially available, semi-custom, or custom, the processor may be part of a larger circuit or semiconductor device. As a specific example, some commercially available microprocessors have multiple cores, such that one or a subset of the cores may constitute the processor. However, the processor may be implemented using circuitry in any suitable form.

Further, a processor may have one or more input devices and output devices. These devices may be used to present a user interface, among other things. Examples of output devices that may be used to provide a user interface include a display screen for visual presentation of output and a speaker or other sound generating device for audible presentation of output. Examples of input devices that may be used for the user interface include keyboards, individual buttons, and pointing devices, such as mice, touch pads, and digitizing tablets. As another example, the computing device may receive input information through speech recognition or in other audible format.

Such processors may be interconnected by one or more networks in any suitable form, including as a local area network or a wide area network, such as an enterprise network or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol, and may include wireless networks, wired networks, or fiber optic networks.

Further, the various methods or processes outlined herein may be coded as software that is executable on one or more processors that employ any one of a variety of operating systems or platforms. Additionally, such software may be written using any of a number of suitable programming languages and/or programming tools or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on an architectural or virtual machine.

In this regard, the embodiments described herein may be implemented as a computer readable storage medium (or multiple computer readable media) (e.g., a computer memory, one or more floppy disks, compact Disks (CDs), optical disks, digital Video Disks (DVDs), magnetic tapes, flash memories, RAMs, ROMs, EEPROMs, circuit configurations in field programmable gate arrays or other semiconductor devices, or other tangible computer storage media) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments discussed above. As is apparent from the foregoing examples, a computer-readable storage medium may retain information for a sufficient time to provide computer-executable instructions in a non-transitory form. Such computer-readable storage media or media may be transportable, such that the program or programs stored thereon can be loaded onto one or more different computer devices or other processors to implement various aspects of the present disclosure as discussed above. As used herein, the term "computer-readable storage medium" encompasses only a non-transitory computer-readable medium that can be considered a product (i.e., article of manufacture) or a machine. Alternatively or additionally, the disclosure may be embodied as a computer-readable medium other than a computer-readable storage medium, such as a propagated signal.

The terms "program" or "software" as used herein refer in a generic sense to any type of computer code or set of computer-executable instructions that can be employed to program a computer device or other processor to implement various aspects of the present disclosure as discussed above. In addition, it should be understood that according to one aspect of this embodiment, one or more computer programs that when executed perform methods of the present disclosure need not reside on a single computer device or processor, but may be distributed in a modular fashion amongst a number of different computers or processors to implement various aspects of the present disclosure.

Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments.

Various aspects of the present disclosure may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in this application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

Embodiments described herein may be embodied as methods for which examples have been provided. The actions performed as part of the method may be ordered in any suitable way. Thus, embodiments may be constructed which perform acts in an order different than shown, and may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

Further, some actions are described as being performed by a "user". It should be understood that a "user" need not be a single individual, and that in some embodiments, actions attributable to the "user" may be performed by a team of individuals and/or by the individual in conjunction with computer-assisted tools or other mechanisms.

Use of ordinal terms such as "first," "second," "third," etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

While the present teachings have been described in connection with various embodiments and examples, the present teachings are not intended to be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those skilled in the art. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. An assembly apparatus, comprising:

a support structure;

a plurality of tethers suspended from the support structure, the plurality of tethers configured to suspend a first object from the support structure; and

one or more actuators operatively coupled to at least one selected from the group consisting of the support structure and the plurality of tethers, the one or more actuators configured to lower a portion of the first object under the influence of gravity toward a cavity formed in a second object having a ramp formed along at least a portion of the cavity, and wherein the one or more actuators and the plurality of tethers are configured to control the lowering of the portion of the object such that the portion of the first object contacts and slides along the ramp as the portion of the first object is inserted into the cavity.

2. The assembly device of claim 1, wherein the one or more actuators are configured to maintain a predetermined tension in each of the plurality of tethers as the portion of the first object is lowered into the cavity.

3. The assembly device of claim 1, wherein the one or more actuators are configured to lower the support structure.

4. The assembly device of claim 3, wherein the one or more actuators include a plurality of actuators configured to extend the plurality of tethers to lower the first object.

5. The assembly device of claim 4, wherein the plurality of tethers comprise one or more sensors configured to sense tension of the plurality of tethers.

6. The assembly device of claim 5, wherein the one or more actuators are configured to change the tension of the plurality of tethers based at least in part on the sensed tension.

7. The assembly device of claim 6, wherein the one or more actuators are configured to be controlled by a processor based at least in part on the sensed tension.

8. The assembly device of claim 1, wherein the one or more actuators and the plurality of tethers are configured to hold the first object substantially upright when the first object is lowered into the cavity of the second object.

9. The assembly device of claim 1, wherein the plurality of tethers comprises two tethers configured to move the first object in two dimensions.

10. The assembly device of claim 1, wherein the plurality of tethers comprises three tethers configured to move the first object in three dimensions.

11. The assembly device of claim 1, wherein the one or more actuators are configured to move the objects such that a magnitude of movement of the portion of the first object toward the cavity of the second object is greater than a magnitude of movement of the portion of the first object away from the cavity of the second object as the first object slides along the sloped surface of the second object.

12. The assembly device of claim 1, wherein a line extending coaxially with the plurality of tethers intersects at an intersection point, and wherein the intersection point is offset by a predetermined distance in a vertical direction relative to a bottom surface of the portion of the first object oriented toward the cavity, wherein the vertical direction is parallel to a direction of gravity.

13. The assembly device of claim 12, wherein the predetermined distance is offset relative to the bottom surface by at least 50% of an overall length of the first object, wherein the overall length is parallel to a direction of gravity.

14. The assembly apparatus of claim 12, wherein the assembly apparatus further comprises a processor configured to control the one or more actuators such that a length of each tether of the plurality of tethers is set such that the intersection point phase is offset relative to the bottom surface by at least the predetermined distance.

15. A method of positioning an object in a cavity, comprising:

a plurality of tethers suspending the first object to the assembly device;

lowering a portion of the first object under the influence of gravity toward a cavity formed in a second object having the sloped surface formed along at least a portion of the cavity such that at least a portion of the first object is in contact with the sloped surface;

sliding the portion of the first object along the ramp; and

disposing the first object in the cavity of the second object.

16. The method of claim 15, wherein lowering the first object into the cavity of the second object comprises lowering the plurality of tethers.

17. The method of claim 16, wherein lowering the plurality of tethers comprises maintaining a predetermined tension in each tether of the plurality of tethers as the portion of the first object is lowered into the cavity of the second object.

18. The method of claim 15, wherein lowering the first object into the cavity comprises holding the first object substantially upright.

19. The method of claim 15, wherein sliding the portion of the first object along the ramp comprises moving the first object such that a magnitude of motion of the portion of the first object toward the cavity of the second object is greater than a magnitude of motion of the portion of the first object away from the cavity of the second object.

20. The method of claim 15, wherein suspending the first object from the plurality of tethers of the assembly device comprises suspending the first object such that lines extending co-axially with the plurality of tethers intersect at an intersection point, and wherein the intersection point is offset by a predetermined distance in a vertical direction relative to a bottom surface of the portion of the first object oriented toward the cavity, wherein the vertical direction is parallel to a direction of gravity.