Robotic positioning system

Abstract

A microplate handling apparatus comprising: a base; and a robotic arm mounted on the base; wherein the base has at least one attachment mechanism for attaching a microplate storage device to the base; and wherein the base has at least one instrument alignment mechanism for defining a positional relationship between the robotic arm and an instrument. By providing for attachment of one or more microplate storage devices and one or more instruments to the base, the positional relationships between the robot and the microplate handling/storing devices (i.e. the microplate storage devices and the instruments) can be well-defined without having to secure any of the components (base, microplate storage devices or instruments) to a bench. The whole system can simply sit on top of a bench without any risk of relative movement between the various parts of the system. Instead the whole system is connected together and can be moved as one unit.

Claims

1. A microplate handling apparatus comprising: a base; and a robotic arm mounted on the base; wherein the base has at least one attachment mechanism for attaching a microplate storage device to the base; and wherein the base has at least one instrument alignment mechanism for defining a positional relationship between the robotic arm and an instrument

2. A microplate handling apparatus as claimed in claim 1, wherein the or each attachment mechanism is arranged to position a corresponding microplate storage device within the work envelope of the robotic arm.

3. A microplate handling apparatus as claimed in claim 1, wherein the or each alignment mechanism is arranged to position a corresponding instrument within the work envelope of the robotic arm.

4. A microplate handling apparatus as claimed in claim 1, wherein the or each attachment mechanism and the or each alignment mechanism is arranged to position a centre of a microplate nest of each corresponding microplate storage device and instrument at an equal distance from a primary rotational axis of the robotic arm.

5. A microplate handling apparatus as claimed in claim 1, wherein the base has a substantially circular perimeter and wherein the or each alignment mechanism is provided on the circular perimeter.

6. A microplate handling apparatus as claimed in claim 1, wherein the robotic arm has no more than 3 degrees of freedom.

7. A microplate handling apparatus as claimed in claim 6, wherein the robotic arm has no more than two rotational pivots.

8. A microplate handling apparatus as claimed in claim 7, wherein one of said pivots is for rotating a gripper device on a distal end of the arm.

9. A microplate handling apparatus as claimed in claim 6, wherein the robotic arm comprises a rigid bar pivotally mounted at its proximal end around a central axis and wherein the rigid bar comprises no further pivots between said proximal end and a distal end.

10. A microplate handling apparatus as claimed in claim 9, wherein a microplate gripper is pivotally mounted on the distal end of the rigid bar.

11. A microplate handling apparatus as claimed in claim 1, wherein all robot joints comprise DC stepper motors arranged to effect movement of said joints.

12. A microplate handling apparatus as claimed in claim 1, wherein the alignment mechanism is adjustable so as to permit adjustment of the relative position of the robotic arm relative to an instrument aligned on the alignment mechanism.

13. A microplate handling apparatus as claimed in claim 12, wherein the alignment mechanism comprises at least one adjuster connecting the base to the alignment mechanism such that rotation of the adjuster adjusts the separation of the alignment mechanism and the base.

14. A microplate handling apparatus as claimed in claim 13, wherein the alignment mechanism comprises at least two adjusters, each connecting the base to the alignment mechanism and the at least two adjusters being horizontally separated from each other so as to permit adjustment of the distance of the alignment mechanism from the base as well as the angle of the alignment mechanism relative to the base.

15. A microplate handling apparatus as claimed in claim 1, wherein the instrument alignment mechanism comprises a first part attached to the base and a second part removably attached to the first part for alignment contact with an instrument.

16. A microplate handling apparatus as claimed in claim 15, wherein the instrument alignment mechanism further comprises a third part removably attached to the first part for alignment contact with the instrument.

17. A microplate handling apparatus as claimed in claim 1, further comprising a slot formed in the instrument alignment part for receiving an instrument securing strap.

Description

[0038] Preferred embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0039] FIG. 1 shows an embodiment of a robotic arm with a microplate nest attached and an instrument alignment mechanism attached;

[0040] FIG. 2 shows a top view of a the robotic arm of FIG. 1 aligned with an instrument;

[0041] FIG. 3 shows a close-up of the robotic arm;

[0042] FIG. 4 shows a close-up of an adjustment mechanism; and

[0043] FIG. 5 shows an example of an instrument foot holder.

[0044] FIG. 1 shows a microplate handling apparatus 100. A robotic arm 2 is mounted on a base 4. The robotic arm 2 has a central vertical rotary shaft 6 which can rotate around its central axis 8 (this being the primary axis of rotation for the robotic arm 2). A rigid bar 10 extends horizontally from the central shaft 6. The rigid bar 10 is mounted to a slot 12 in the shaft 6 and is vertically movable relative to the shaft 6, i.e. vertically movable parallel to the rotation axis 8.

[0045] The proximal end 14 of the rigid bar 10 is mounted to the slot 12. The distal end 16 of the rigid bar 10 has a gripper 18 mounted thereto. The rigid bar 10 is shown in more detail in FIG. 3. The gripper 18 is rotationally mounted to the distal end 16 of the rigid bar 10 such that it can rotate around a secondary rotation axis 20 (although it will be appreciated that in some embodiments the gripper 18 need not be mounted in a rotary fashion and could therefore be fixed in a non-rotary manner to the distal end 16 of the rigid bar 10). The gripper device 18 is typically used to grip the sides of a microplate (or the lid of a microplate when the lid is to be removed from the microplate) between two gripping claws. The gripping claws can be moved together to grip and hold or moved further apart to release.

[0046] Although not shown in the figures, each of the robotic arm's joints (e.g. the joint where the central shaft 6 pivots on the base 4, the joint where the rigid bar 10 slides up and down the central shaft 6 and the joint where the gripper 18 rotates relative to the rigid bar 10) are driven by DC stepper motors. These are much less expensive than the servo motors used in more complex robotic arms, but with the simplified structure of this apparatus, the DC stepper motors are sufficiently accurate, thus greatly reducing the overall cost of the apparatus 100.

[0047] The robotic arm 2 has three degrees of freedom, the first being rotation about the primary rotation axis 8 of the central shaft, the second being translation of the rigid bar 10 vertically up and down the shaft 6 in slot 12, and the third being rotation of the gripper device 18 on the distal end 16 of rigid bar 10.

[0048] The robotic arm 2 is mounted to a base 4 that provides a stable support structure and is the central structure to which all other bits of equipment are connected. The base 4 is generally circular in this embodiment, having a circular perimeter 20, although it will be appreciated that other shapes may be used. A benefit of the circular design is that the robotic arm 2 can be mounted concentrically with the circular base so that other pieces of equipment attached to the base 4 will have a definite and consistent relationship with the work envelope of the robotic arm 2 regardless of their angular position of attachment to the base 4. The work envelope of the robotic arm 2 may be defined as the locus of positions at which the gripper 18 can pick up or deposit a microplate. With the arrangement described here, the work envelope is a cylinder, centred on the primary rotation axis 8 with a radius equal to the distance of the centre of the gripper device 18 from the primary rotation axis 8 and with a vertical extent defined by the vertical range of motion of the rigid bar 10 in the slot 12.

[0049] Around the perimeter 20 of the base 4, there are several (six in this embodiment) attachment points (or attachment mechanisms) 22 at which other pieces of equipment may be attached. As an example, a microplate storage nest 24 is shown attached to one of the attachment mechanisms 22 in FIG. 1. The nest 24 is a simple type of storage device capable of storing either a single microplate or a stack of microplates simply stacked one on top of the other. Such nests 24 may be used for temporary storage of a single microplate or lid, e.g. for a lid removal or lid storage operation, or just to store a plate close to the next piece of processing or analysis equipment. Alternatively, a nest 24 may be used as an input stack or an output stack, the plates in an input stack being processed sequentially from top to bottom and stored sequentially from bottom to top to form an output stack. Several such nests 24 may be attached to the base 4 at the various attachment points 22 as required. In a typical simple installation only two or three attachment points 22 may be used, but providing six allows for flexibility in terms of selecting positions that are convenient for a particular laboratory setup (e.g. where the installation space is small or constrained in shape), as well as the flexibility to use a larger number of stations (e.g. two or more input stacks and two or more output stacks, and/or temporary storage points).

[0050] It will be appreciated that more complicated storage equipment may be attached instead of simple nests 24. For example plate storage systems that have their own internal microplate picking system can be attached so as to serve up a chosen microplate within the work envelope of the robotic arm 2.

[0051] Each attachment point 22 in this embodiment comprises two slots 22a, 22b, each having a T-shaped cross-section and being open at the top. A piece of equipment may be attached by being provided with appropriately sized and positioned T-shaped projections that can be slotted in to the twos lots 22a, 22b from above. As can be seen in FIG. 1, the nest 24 is also curved at its connecting end so as to mate against the circular perimeter 20 of the base 4. This provides a secure and solid connection such that the position of the microplate(s) held in the nest 24 is well-defined with respect to the robotic arm 2.

[0052] Around the perimeter of the base 4, a number of cable channels 26 are formed to allow for power and/or communications leads to reach the robotic arm 2 and associated control circuitry. In this embodiment these are conveniently arranged so that there is one channel 26 for each attachment point 22, centrally located with respect thereto. The provision of a number of such channels 26 again allows flexibility in the setup of the equipment so that it can readily be adapted for a particular laboratory.

[0053] An instrument alignment mechanism 28 is also connected to base 4. The instrument alignment mechanism 28 is shaped so as to receive a microplate processing instrument 30 (which can be seen in FIG. 2, but not in FIG. 1) in such a way that the positional relationship between the instrument 30 and the robotic arm 2 is well-defined, i.e. such that when the instrument 30 and the instrument alignment mechanism 28 together define a certain positional relationship. When duly engaged, a microplate nest 32 of the instrument 30 is positioned within the work envelope of the robotic arm. This means that the centre of the nest 32 is aligned with the centre of the gripping device 18 sufficiently well that the robotic arm 2 can reliably and accurately pick up a microplate 34 from the nest 32 and deposit a microplate 34 in the nest 32. It will be appreciated that there is some tolerance in these actions in that the gripper can hold a microplate 34 slightly off centre and the nest 32 can allow for a slight disparity between the centre position of the gripper 18 and the centre position of the nest 32, e.g. by providing slightly sloped sides that guide the microplate 34 into the nest 32. However, the aim is to minimise such misalignments so as to improve the reliability and consistency of operation with reduced chances of misplacing or dropping a microplate 34 (with associated spillage and/or disruption to the processing workflow).

[0054] While the base 4 has a substantially circular perimeter 20, the instrument alignment mechanism 28 is attached to a flattened part of the perimeter of the base 4. In other words the base 4 has a flat edge forming a chord across the generally circular shape of the base 4. The embodiment shown in the figures is only designed for a single instrument alignment mechanism 28 to be attached to the base 4. This is preferred for simple setups where a single complex processing or analysis machine is required. However, it will be appreciated that where more than one such machine is required, it may be possible to attach a further instrument alignment mechanism to one or more of the attachment points 22, or to form an additional flat section (chord) on the base 4 for a second instrument alignment mechanism 28.

[0055] The instrument alignment mechanism 28 is formed from a number of parts and can be readily adapted to a number of different instruments 30. A flat base part 36 is common to all configurations and provides an attachment surface for various other parts that are specific to each configuration. In this embodiment a first part 38 is attached to the base part 36 and provides a connection mechanism for connecting the instrument alignment mechanism 28 to the base 4. The first part 38 may be attached to the base part 36 in any suitable way, but for convenience and ease of assembly and adaption, the first part 38 is preferably attached to the base part 36 by means of removable fixing means such as screws 40. The first part 38 has two adjuster mechanisms 42 each of which connects the first part 38 to the base 4 in an adjustable manner. Each adjuster 42 is a thumb wheel in this embodiment. One adjuster 42 is shown in more detail in FIG. 4. Each adjuster 42 has a thumb wheel 44 that is held captive in the first part 38 such that it can rotate with respect to the first part 38, but cannot move axially with respect to it. The thumb wheel 44 has a central axial hole which is internally threaded and receives an externally threaded bolt (not visible) which is fixedly attached to the base 4 and projects towards and partially into the first part 38. As the thumb wheel 44 is rotated, the mated thread portions of the wheel 44 and the bolt cause axial displacement of the wheel 44 along the rod and thus adjust the separation distance of the base 4 and the first part 38.

[0056] As two adjusters 42 are provided, spaced apart from one another and connected to the base 4 at different points, both the spacing and orientation of the instrument alignment mechanism can be adjusted relative to the base 4. For example by adjusting both adjusters 42 in the same direction and by the same amount, the instrument alignment mechanism 28 can be moved towards or away from the base 4 (in a generally radial direction), while adjustment of the two adjusters 42 in opposite directions by equal amounts will rotate the instrument alignment mechanism 28 relative to the base 4. Thus by careful adjustment of both adjusters 42 the instrument alignment mechanism 28 (and thus an instrument 30 that is aligned with the instrument alignment mechanism 28) can be adjusted such that the nest 32 of the instrument 30 is accurately placed in the work envelope of the robotic arm 2 for optimal operation (i.e. with minimal risk of microplate pick-up or placement errors).

[0057] In this embodiment the base part 36 is L-shaped so that it forms a corner between the two straight sections of the L. The second part 46 of the instrument alignment mechanism 28 is an extension of the L-shape of the base part 36 and is attached thereto by screws 40. The corner shape is useful for ensuring correct placement and alignment of an instrument 30 against the alignment mechanism 28 by settling a corner of the instrument 30 into the corner of the L-shape. As the L-shape contacts two sides of the instrument 30, its relative orientation is defined as well its relative position. In some cases, if the instrument 30 has a suitable corner shape close to the bench, the second part 46 may not be necessary (the corner shape of the base part 36 serving the alignment function). However, in other embodiments the base part 36 may not have an L-shape or it may not extend high enough to contact the instrument side walls (e.g. if the instrument is raised off the bench on feet). For best alignment, the L-shape could extend a significant distance in each direction so as to provide significant contact between the second part 46 and the instrument walls. However, to keep the size of the second part 46 small, the L-shape may be asymmetrical, only providing enough surface to ensure accurate positioning without ensuring accurate orientation. To ensure accurate orientation, a third part 48 is then provided to contact the instrument side wall closest to the base 4 at another position along the base part 36. Again the third part 48 may be fixed to the base 36 by screws 40 or similar.

[0058] It can be seen that this design allows significant flexibility for aligning a number of different instruments with the robotic arm 2. Each instrument has a nest 32 that needs to be aligned with the robotic arm 2 so that it is placed accurately within the work envelope of the robot (thus avoiding the need for more degrees of freedom in the robot). Thus each instrument needs a suitably formed instrument alignment mechanism 28. This can be formed using inexpensively molded plastic parts that are dimensioned so as to engage the instrument 30 at suitable corners and/or walls to place its nest 32 radially in line with the robotic arm 2 (i.e. radially in line with the rigid bar 10). The alignment mechanism also ensures a coarse positional alignment of the nest 32 along the radial direction so that the centre of the nest 32 aligns with the centre of the gripper 18 on the distal end 16 of the rigid bar 10. Fine adjustment to provide the optimal spatial alignment of the nest 32 with the gripper 18 is achieved by means of the adjusters 42.

[0059] It will be appreciated that each configuration of the various parts 36, 38, 46, 48 of the alignment mechanism 28 may be re-usable for several different instruments 30. For example the first part 36 is the most complicated to mold and is preferably re-usable for all instruments 30. Of the simpler shaped (and easier to mold) parts, these may be designed specifically for a certain instrument 30, but they are preferably also re-usable for multiple instruments where possible. For example the base part 36 may be a suitable basic mounting platform for several instruments 30. Specific versions of the second part 46 will most likely be required for each instrument 30 as this part locates the instrument corner. The third part 48 can likely apply to several different instruments as it merely provides additional bracing for correct orientation.

[0060] In some embodiments, instead of locating a corner of an instrument 30 (e.g. in cases where an instrument may not have a well-defined corner), location and orientation can instead be provided by cups arranged to locate and hold the instrument's feet. An example of such a cup 60 is shown in FIG. 5. For such embodiments, a dedicated base part 36 may be provided for the instrument 30 with suitably positioned mounting points for the foot cups 60.

[0061] Overall, the instrument-specific parts required for proper alignment are minimal and can be manufactured inexpensively, allowing this system to be used on a large range of instruments 30 at minimal expense to the end user.

[0062] With the arrangement described above, it will be appreciated that an instrument 30 and the robotic arm 2 can be positioned reliably with respect to one another without fixing anything to a laboratory bench and without having to go through a complex training or programming exercise to teach the robotic arm 2 where to pick up and place microplates in the various stores (e.g. input and output stacks) and instruments 30. Once in instrument 30 is positioned with the correct instrument alignment mechanism 28 and adjusted via adjusters 42, the positions are unlikely to change providing the instrument 30 and the base 4 are not knocked or vibrated out of alignment for some reason. However, if such misalignment is a significant risk then for additional security a strap may be used to hold the instrument 30 to the alignment mechanism 28. For this purpose a slot 50 is formed in the instrument alignment mechanism, passing behind at least one of the second and third parts 46, 48 (or both if they are both in use). A strap 52 (shown in FIG. 2) can be dropped into the slot 50, passed around the instrument 30 and brought into tension to hold the instrument 30 against the alignment mechanism 28. Any accidental knocks or vibrations should then not affect the relative position and alignment of the instrument 30 and the robotic arm 2.