Patent Description:
The invention is defined by the apparatus of independent claim <NUM>. Optional features of the apparatus are set out in the dependent claims. While methods are not explicitly claimed, the claimed apparatus may be used with, or usable in relation to, the methods described hereafter. Some embodiments described herein relate to an arm cart operable to transport a robotic arm to and/or from a surgical table. The robotic arm can be coupled to the arm cart via a connector. The connector can be slideably mounted to the arm cart such that the connector and the robotic arm, collectively, can move relative to the arm cart. For example, when the arm cart is adjacent to the surgical table, the connector and the robotic arm can be movable to provide final, fine adjustments to align the robotic arm with a coupling portion of the surgical table.

Apparatus and methods for providing an arm cart for transporting, delivering, and securing robotic arms to a surgical table having a table top on which a patient can be disposed are described herein; the described methods are not explicitly claimed, although the claimed apparatus may be used with, or usable in relation to, these methods. When a robotic arm is delivered to the surgical table, in some instances, the robotic arm may not be precisely aligned with the surgical table. Some embodiments described herein relate to methods and apparatus suitable adjust the robotic arm within the arm cart, which can allow fine adjustments to the surgical arm such that the robotic arm can be more closely aligned to the surgical table.

A surgical table and a robotic arm can be configured to matingly couple. For example, the surgical table and the robotic arm can include complementary coupling portions, such as link and socket mating portions. An arm cart operable to support and/or transport the robotic arm may be suitable to move the robotic arm such that the coupling portion of the robotic arm is approximately aligned with the corresponding coupling portion of the surgical table. Challenges may exist, however, in precisely aligning the arm cart with the surgical table such that the robotic arm can mate with the surgical table. For example, it may be difficult for an operator to steer an arm cart exactly into a precise horizontal position. Moreover, floor coverings, manufacturing tolerances, and the like may result in the robotic arm not precisely aligning with the surgical table. Some embodiments described herein relate to an arm cart having a connector configured to support the robotic arm. The connector can be slideably mounted to the arm cart such that a position of the robotic arm can be adjusted relative to the arm cart. In this way, fine adjustments can be made to the position of the robotic arm, without moving/adjusting the entire arm cart. Fine adjustments can facilitate mating the robotic arm to the surgical table.

Some embodiments described herein relate to a method that includes moving an arm cart containing a robotic arm from a storage location to a surgical table. The arm cart can support the robotic arm in a first position in which a coupling portion of the robotic arm can be approximately aligned with a corresponding coupling portion of the surgical table. Similarly stated, in some embodiments, when the arm cart is moved into proximity with the surgical table, a mating portion of the robotic arm can be within <NUM> - <NUM> of a corresponding mating portion of the surgical table. In other embodiments, when the arm cart is moved into proximity with the surgical table, the robotic arm can be within <NUM>, <NUM>, or any other suitable distance of a corresponding mating portion of the surgical table. The robotic arm can be moved within and/or while still coupled to the arm cart from the first position to a second position, in which the coupling portion of the robotic arm is exactly aligned with the coupling portion of the surgical table. After the robotic arm is exactly aligned with the surgical table, the robotic arm can be coupled to the surgical table and/or decoupled from the arm cart.

As shown schematically in <FIG>, a surgical table <NUM> includes a table top <NUM>, a table support <NUM> and a table base <NUM>. The table top <NUM> has an upper surface on which a patient P can be disposed during a surgical procedure, as shown schematically in <FIG>. The table top <NUM> is disposed on the support <NUM>, which can be, for example, a pedestal, at a suitable height above the floor. The support <NUM> (also referred to herein as a pedestal) may provide for movement of the table top <NUM> in a desired number of degrees of freedom, such as translation in the vertical, or Z axis (height above the floor), horizontal Y axis (along the longitudinal axis of the table), and/or horizontal X axis (along the lateral axis of the table), and/or rotation about the Z, Y, and/or X axes. The table top <NUM> may also include multiple sections that are movable relative to each other along / about any suitable axes, e.g., separate sections for each of the torso, one or both legs, and/or one or both arms, and a head support section. Movement of the table top <NUM> and/or its constituent sections may be performed manually, driven by motors, controlled remotely, or through any other suitable means. The support <NUM> for the table top <NUM> may be mounted to the base <NUM>, which can be fixed to the floor of the operating room, or can be movable relative to the floor, e.g., by use of wheels on the base <NUM>. In some embodiments, the height of the support <NUM> can be adjusted, which together with, for example, the motion (e.g., axial (longitudinal) or lateral motion) of the table top <NUM>, can allow for the table top <NUM> to be positioned at a desired surgical site at a certain height above the floor (e.g., to allow surgeon access) and a certain distance from the support <NUM>. This also can allow robotic arms (e.g., arms <NUM> discussed below) coupled to the table <NUM> to reach a desired treatment target on a patient P disposed on the table top <NUM>.

In a robotically-assisted surgical procedure, one or more robotic arms <NUM> (shown schematically in <FIG>) can be disposed in a desired operative position relative to a patient disposed on the table top <NUM> of the surgical table <NUM> (also referred to herein as "table"). The robotic arm(s) can be used to perform a surgical procedure on a patient disposed on the surgical table <NUM>. In particular, the distal end of each robotic arm can be disposed in a desired operative position so that a medical instrument coupled to the distal end of the robotic arm can perform a desired function.

As shown schematically in <FIG>, each robotic arm <NUM> can include a distal end portion <NUM> and a proximal end portion <NUM>. The distal end portion <NUM> (also referred to herein as "operating end") can include or have coupled thereto a medical instrument or tool <NUM>. The proximal end portion <NUM> (also referred to herein as the "mounting end portion" or "mounting end") can include the coupling portion to allow the robotic arm <NUM> to be coupled to the table <NUM>. The robotic arm <NUM> can include two or more link members or segments <NUM> coupled together at joints that can provide for translation along and/or rotation about one or more of the X, Y and/or Z axes (shown, for example, in <FIG>). The coupling portion of the robotic arm <NUM> can include a coupling mechanism <NUM>. The coupling mechanism <NUM> can be disposed at the mounting end <NUM> of the arm <NUM> and may be coupled to a segment <NUM> or incorporated within a segment <NUM>. The robotic arm <NUM> can be moved between various extended configurations for use during a surgical procedure, as shown in <FIG>, and various folded or collapsed configurations for storage when not in use, as shown in <FIG>.

<FIG> illustrate two embodiments of a surgical table with a robotic arm coupled thereto. As described above and in accordance with various embodiments disclosed in more detail below, the robotic arm may be suitable for use in performing a surgical procedure and may be releasably coupled to a surgical table. In some embodiments, robotic arms can be coupled at a fixed location on the table or can be coupled such that the robotic arms can be movable to multiple locations relative to the table top. For example, as shown schematically in <FIG>, robotic arms <NUM> can be coupled to a table top <NUM> of a surgical table <NUM>. The surgical table <NUM> can be the same or similar in structure and function to the surgical table <NUM> described above. For example, the table top <NUM> has an upper surface on which a patient P can be disposed during a surgical procedure. As shown schematically in <FIG>, in some embodiments, the robotic arms <NUM> can be coupled, in a fixed or movable location, to an arm adapter <NUM> that is coupled to or separate from the surgical table. The arm adapter <NUM> can be coupled to or separate from but engageable with or couplable to the table top <NUM>.

In preparation for a robotically-assisted surgical procedure in which one or more robotic arms are releasably coupled to the surgical table and/or to an arm adapter, as described with respect to <FIG>, each robotic arm may be delivered and connected to the surgical table and/or the arm adapter via an arm cart. As shown schematically in <FIG>, an arm cart <NUM> can be configured to support one or more robotic arms. The arm cart <NUM> includes a first robotic arm 330A and can include an optional second robotic arm 330B. Although two robotic arms <NUM> are shown, the arm cart <NUM> can be configured to contain, transport, and/or deliver any suitable number of robotic arms <NUM>, such as, for example, one robotic arm, three robotic arms, or four robotic arms.

The arm cart <NUM> can be configured for movement. For example a base <NUM> of the arm cart <NUM> can include wheels. In some embodiments, the arm cart <NUM> can be configured to move the robotic arm <NUM> between one or more positions and/or one or more orientations, including, for example, between a storage location and a surgical location. A surgical location (e.g., an operating room) can include a surgical table <NUM>. In this way, the robotic arm <NUM> can be brought into proximity (e.g., in contact with and/or within less than a <NUM>) of the surgical table <NUM>. As described in further detail herein, the robotic arm <NUM> can then be coupled to the surgical table <NUM>.

The surgical table <NUM> can include a table top <NUM>, a table support <NUM>, and a table base <NUM>. The table top <NUM> has an upper surface on which a patient P can be disposed during a surgical procedure. The table top <NUM> is disposed on the support <NUM>, which can be, for example, a pedestal, at a suitable height above the floor. The support <NUM> can be mounted to the base <NUM>, which can be fixed to the floor of the operating room or can be moveable relative to the floor, e.g., by use of wheels on the base <NUM>.

The surgical table <NUM> includes a coupling portion <NUM> configured to receive, be coupled to, and/or mate with a robotic arm (e.g., the robotic arm <NUM>). In some embodiments, the coupling portion <NUM> can be coupled to or separate from but engageable with or couplable to the table top <NUM> (e.g., the coupling portion <NUM> can be a portion of an adapter as shown and described with reference to <FIG>). In other embodiments, the coupling portion <NUM> can be integral with the table top <NUM> and/or the pedestal <NUM>.

The arm cart <NUM> can support the first robotic arm 330A (and the optional second robotic arm 330B) in a variety of configurations. In some embodiments, the first robotic arm 330A can be coupled to the arm cart <NUM> via a connector <NUM>. In embodiments in which the arm cart <NUM> contains (or is configured to contain) multiple robotic arms, the arm cart <NUM> can include multiple connectors <NUM> and/or each robotic arm can be connected and/or disconnected from one connector. In some embodiments, the connector <NUM> can be the sole support for the robotic arm <NUM> and, as described in further detail herein can be configured to move within the arm cart <NUM>. In this way, the connector <NUM> can couple the robotic arm <NUM> to the arm cart <NUM>, and the connector <NUM> and the robotic arm <NUM> can be operable to move within the arm cart <NUM>, for example to allow for fine adjustments of the position of the robotic arm <NUM>.

The robotic arm <NUM> includes a coupling portion <NUM>, which, as described in further detail below, is configured to connect to and/or mate with the coupling portion <NUM> of the surgical table <NUM>. In some embodiments, moving the arm cart <NUM> adjacent to the surgical table <NUM> can be suitable to move the coupling portion <NUM> of the robotic arm <NUM> near the coupling portion <NUM> of the surgical table. The coupling portion <NUM> of the robotic arm <NUM> can be approximately aligned with (e.g., vertically and/or laterally within <NUM> or any other suitable distance) of the coupling portion <NUM> of the surgical table <NUM>. In some instances, however, moving the arm cart <NUM> and/or the surgical table <NUM> may provide only gross or approximate alignment. Similarly stated, in some instances, moving the arm cart <NUM> and/or the surgical table <NUM> may be insufficient to precisely align the coupling portion <NUM> of the robotic arm <NUM> with the coupling portion <NUM> of the surgical table such that the robotic arm <NUM> can be matingly coupled to the surgical table <NUM>.

As described in further detail herein, the robotic arm <NUM> can be coupled to the arm cart <NUM> via the connector <NUM>. The connector <NUM> can permit the robotic arm <NUM> to move within the arm cart <NUM> such that fine adjustments to the alignment of the coupling portion <NUM> of the robotic arm <NUM> can be made (e.g., to bring the coupling portion <NUM> of the robotic arm <NUM> into alignment with the coupling portion of the surgical table <NUM>).

<FIG> is a schematic illustration of mating portions of a surgical table <NUM> and a robotic arm <NUM>, according to an embodiment. The surgical table <NUM> includes a post <NUM> configured to be received by a socket <NUM> of the robotic arm <NUM>. The robotic arm <NUM> is coupled to an arm cart <NUM> via a connector <NUM>. The connector <NUM> includes a spring <NUM> such that the connector <NUM> (and hence the robotic arm <NUM>) can move relative to the arm cart <NUM>. Similarly stated, a force applied to the robotic arm <NUM> and/or the connector <NUM> can cause the spring <NUM> to deform, allowing the robotic arm <NUM> to move. In this way, fine adjustments to position of the robotic arm <NUM> can be adjusted, for example to align the socket <NUM> to the post <NUM>.

In some embodiments, the post <NUM> can be chamfered and/or beveled such that, when the post <NUM> contacts the socket <NUM>, for example as the arm cart <NUM> is pushed towards the surgical table <NUM>, if the post <NUM> and the socket <NUM> are not precisely aligned, the chamfer of the post <NUM> can apply a force to the socket <NUM> urging the socket <NUM> into closer alignment with the post <NUM>. The spring <NUM> can deform in response to the force and the post <NUM> and the socket <NUM> can mate.

<FIG> is a schematic illustration of a connector <NUM>, according to an embodiment. The connector <NUM> can be structurally and/or functionally similar to the connectors <NUM> and/or <NUM> described above. The connector <NUM> can be operable to be connected to and/or support a robotic arm (not shown in <FIG>) within an arm cart <NUM>. The connector <NUM> can be operable to enable fine adjustments to the alignment of the robotic arm relative to the arm cart <NUM> and/or a surgical table (not shown in <FIG>) to be made such that the robotic arm can matingly coupled to the surgical table. As shown in <FIG> and described in further detail below, the connector <NUM> can provide two degrees of freedom, enabling the robotic arm to move in a horizontal and a vertical direction relative to the arm cart <NUM>. For movement in the third dimension, the arm cart <NUM> itself can be moved towards and/or away from the surgical table.

The connector <NUM> includes two orthogonal prismatic (or sliding) joints. A first block <NUM> is operable to slide vertically on two vertical posts <NUM>, each of which is fixedly coupled to the arm cart <NUM>. Similarly stated, the first block <NUM> can define a through hole corresponding to each vertical post <NUM>. The through hole and the vertical posts <NUM> can be sized such that a sliding clearance is defined. Although two vertical posts <NUM> are shown, any suitable number of vertical posts <NUM> can be used. It should be noted, however, that in some embodiments the presence of at least two vertical posts <NUM> and/or non-circular posts to constrain the first block <NUM> from rotating about the vertical axis can be desirable. Springs <NUM> are disposed over the vertical posts <NUM>, although in other embodiments, springs <NUM> can be coupled to the arm cart <NUM> and the first block <NUM> in any suitable location (e.g., not necessarily coaxial with the posts <NUM>). As shown, each vertical post <NUM> has two springs <NUM>, one above and one below the first block <NUM>, upper springs can resist movement of the first block <NUM> in one vertical direction, while the lower springs can resist movement of the first block <NUM> in the opposite vertical direction. In other embodiments, springs resisting movement of the first block <NUM> in the upward direction can be omitted, and the weight of the connector <NUM> and/or robotic arm against springs resisting movement of the first block <NUM> in the downward direction can maintain the first block <NUM> in a rest position.

A second block <NUM> is operable to slide horizontally on two horizontal posts <NUM>, each of which coupled to the first block <NUM>. In this way, the second block <NUM> has two degrees of freedom relative to the arm cart <NUM>. Again, in some embodiments, the presence of at least two horizontal posts <NUM> and/or non-circular horizontal posts can be desirable to constrain the second block <NUM> from rotating about the axis of the horizontal posts <NUM>. Thus, the second block <NUM> can be operable to move horizontally and vertically relative to the arm cart <NUM> while being constrained from any rotational movement. Springs <NUM> are disposed over the horizontal posts <NUM>, although in other embodiments, springs <NUM> can be coupled to the first block <NUM> and the second block <NUM> in any suitable location (e.g., not necessarily coaxial with the posts <NUM>). As shown, each horizontal post has two springs <NUM>, one on either side of the second block <NUM>. The opposing springs can be operable to resist movement of the second block <NUM> in opposite directions.

The second block <NUM> can include a latch, magnet, or other suitable coupling mechanism operable to be removably coupled to the robotic arm. Thus, the robotic arm can be removably coupled to the second block <NUM>, and the connector <NUM> can allow the robotic arm to move with two degrees of freedom relative to the arm cart <NUM>. The springs <NUM> and <NUM> can be operable to maintain the robotic arm in a rest position, but allow for limited movement (e.g., up to <NUM> in a vertical direction and up to <NUM> in a lateral direction, up to <NUM> in any direction, and/or any other suitable amount of movement) for fine adjustments of position and/or alignment while urging the robotic arm back to the rest position. The springs <NUM> and <NUM> have the added benefit of acting as shock absorbers cushioning the robotic arm during transit and/or impacts involving the arm cart <NUM>. In some embodiments, stops can be coupled to the vertical posts <NUM> and/or the horizontal posts <NUM> such that motion of the first block <NUM> and/or the second block <NUM> can be limited by the stops.

<FIG> is a schematic illustration of a connector <NUM>, according to an embodiment. The connector <NUM> is similar to the connector <NUM> described above and/or can be structurally and/or functionally similar to the connectors <NUM> and/or <NUM>. The connector <NUM> includes a first block <NUM> and a second block <NUM> that are slideably coupled to each other such that the connector <NUM> has two degrees of freedom. The first block <NUM> includes a first groove <NUM> slideably coupled to a rail <NUM> of the arm cart. The second block <NUM> includes a tongue <NUM> slideably disposed within a second groove <NUM> of the first block <NUM>. The second block <NUM> is configured to be coupled to a robotic arm. The connector <NUM> can be operable to be coupled to and/or support a robotic arm via the second block <NUM>. Thus, the robotic arm and the second block <NUM> can move relative to the arm cart <NUM>, which can permit fine adjustments as discussed above.

A first (e.g., vertical) set of opposed springs <NUM> and a second (e.g., lateral) set of opposed springs <NUM> are coupled to the second block <NUM> and the arm cart <NUM>. The springs <NUM> and <NUM> can maintain the second block <NUM> and/or the robotic arm in a rest position while allowing for limited movement.

<FIG> is flow chart of a method of coupling a robotic arm to a surgical table, according to an embodiment. At <NUM>, an arm cart containing a robotic arm can be moved to a surgical table, for example, from a storage location. Each of the robotic arm and arm cart can be similar to those described above. Moving the arm cart to the surgical table, at <NUM> can include orienting a coupling portion of the surgical arm adjacent to a corresponding coupling portion of the surgical table. For example, the arm cart can be placed near the surgical table (e.g., within a foot or less) such that the coupling portion of the surgical arm is approximately aligned with the corresponding coupling portion of the surgical table. For example, the arm cart can be positioned relative to the surgical table such that the coupling portion of the robotic arm is aligned (e.g., vertically and/or laterally) within less than <NUM> of the coupling portion of the surgical table. Similarly stated, when the arm cart is moved adjacent to the surgical table, the robotic arm can be in a first position in which springs (e.g., as shown in <FIG>) and the force of gravity on the connector and surgical arm are balanced. In the first position, the robotic arm may not be precisely aligned with the surgical table.

At <NUM>, fine adjustments of the position of robotic arm within the arm cart can be made, for example, by applying a force to the robotic arm and/or the coupler, the robotic arm can move vertically and/or laterally (horizontally) relative to the arm cart. For example springs (as shown in <FIG>) can deform but allow the robotic arm and coupler to move a sufficient distance to allow fine position adjustments (e.g., adjustments of <NUM>-<NUM> or any other suitable adjustments) to be made. In some embodiments, the coupler can be configured to allow the robotic arm (and the coupling portion of the robotic arm) to translate vertically and/or laterally, while constraining rotational movement. Constraining rotational movement, using, for example, tongue-and-groove prismatic joints (as shown, for example, in <FIG>) and/or two or more rods (as shown, for example, in <FIG>) can reduce or eliminate radial misalignment.

In some embodiments, fine adjustment of the position of the robotic arm, at <NUM>, can include pushing the arm cart towards the surgical table such that the coupling portion of the robotic arm contacts the coupling portion of the surgical table. As shown, for example, in <FIG>, the coupling portion of the surgical table can include a chamfer or similar structure configured to apply a force to the coupling portion of the coupling portion of the arm cart. In this way, as the arm cart moves towards the surgical table, the movement of the arm cart can cause the coupling portions of the surgical table and arm cart to move into exact alignment. Exact alignment, as used in the present application, refers to the coupling portions of the robotic arm and the surgical table having relative positions such that the robotic arm can mate with the surgical table.

Once aligned, the robotic arm can be coupled to the surgical table, at <NUM>. Then, the robotic arm can be decoupled from the connector and arm cart, at <NUM>. Subsequently, the arm cart can be moved away from the surgical table, for example, to a storage location, at <NUM>, and the arm can be prepared for use in a surgical procedure.

While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. For example, with reference to <FIG>, the coupling portion of the surgical table is shown and described as a post, while the coupling portion of the robotic arm is shown and described as a socket. It should be understood that in other embodiments, the coupling portion of the robotic arm can be a post and the coupling portion of the surgical table can be a socket.

As another example, in some embodiments, the coupling portions of the robotic arm and the surgical table can be directional, such as corresponding cruciform, star-shaped, or any other suitable coupling portions. In such an embodiment, constraining rotational movement of the robotic arm (e.g., using non-circular and/or multiple prismatic joints) can play an additional role in maintaining alignment of the coupling portions of robotic arm and the surgical table. As another example, although some embodiments describe the use of prismatic joints to permit fine adjustment of the robotic arm relative to the arm cart, any other suitable mechanism can be used. For example, rather than nested prismatic joints, two ball joints separated by a link can permit fine adjustment of the robotic arm with two degrees of freedom. As yet another example, although some embodiments describe vertical or horizontal (or lateral) structures (e.g. springs, rods, grooves, etc.) it should be understood that in other embodiments, springs, joints and the like can be in any orientation. For example, in some embodiments, rather than being oriented at <NUM> and <NUM> degrees, prismatic joints and/or springs can be oriented at <NUM> and <NUM> degrees.

As yet another example, some embodiments are described herein as containing springs. Springs can be operable to urge a connector and/or a robotic arm towards a rest position, while allowing fine adjustments of the connector and/or robotic arm. It should be understood, however, that in other embodiments, springs may be omitted and the connector and/or robotic arm can be movable relative to the arm cart but may not include springs to urge the connector and/or robotic arm towards a rest position. Furthermore, where springs are described, it should be understood that any suitable mechanism operable to allow the connector to move and/or exert a force to urge the connector and/or robotic arm towards a rest position, such as a mechanical spring (e.g., coil spring, leaf spring, compression spring, extension spring, etc.), gas springs, hydraulic springs, magnets, linear actuators, etc. can be used. Some embodiments can also include dampers in parallel with or in series with springs.

Where methods described above indicate certain events occurring in certain order, the ordering of certain events may be modified. Additionally, certain of the events may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. No methods are explicitly claimed, although the claimed apparatus may be used with, or usable in relation to, the described methods.

Claim 1:
An apparatus comprising:
a robotic arm (<NUM>, <NUM>, <NUM>, <NUM>) configured to be removeably coupled to a surgical table (<NUM>, <NUM>, <NUM>, <NUM>), the robotic arm (<NUM>, <NUM>, <NUM>, <NUM>) including a socket (<NUM>) configured to mate with a link of the surgical table (<NUM>, <NUM>, <NUM>, <NUM>);
an arm cart (<NUM>, <NUM>, <NUM>) configured to contain the robotic arm and transport the robotic arm (<NUM>, <NUM>, <NUM>, <NUM>) between the surgical table (<NUM>, <NUM>, <NUM>, <NUM>) and a storage location; and
a connector (<NUM>, <NUM>, <NUM>, <NUM>), the robotic arm coupled to the arm cart (<NUM>, <NUM>, <NUM>) via the connector, the connector (<NUM>, <NUM>, <NUM>, <NUM>) slideably mounted to the arm cart (<NUM>, <NUM>, <NUM>) such that the connector (<NUM>, <NUM>, <NUM>, <NUM>) and the robotic arm (<NUM>, <NUM>, <NUM>, <NUM>) are configured to collectively move relative to the arm cart (<NUM>, <NUM>, <NUM>),
characterized in that the apparatus further comprises:
a first plurality of springs (<NUM>, <NUM>), each spring from the plurality of springs being substantially horizontal, having a first end portion coupled to the arm cart (<NUM>, <NUM>, <NUM>), and having a second end portion coupled to the connector (<NUM>, <NUM>, <NUM>, <NUM>);
a second plurality of springs (<NUM>, <NUM>), each spring from the second plurality of springs being substantially vertical, having a first end portion coupled to the arm cart (<NUM>, <NUM>, <NUM>), and having a second end portion coupled to the connector (<NUM>, <NUM>, <NUM>, <NUM>);
the first plurality of springs (<NUM>, <NUM>) and the second plurality of springs (<NUM>, <NUM>) each configured to provide elastic resistance to moving the connector (<NUM>, <NUM>, <NUM>, <NUM>) relative to the arm cart (<NUM>, <NUM>, <NUM>).