Asymmetric dual end effector robot arm

Abstract

To provide a robot arm having asymmetric end effectors having substrate holding areas that are skewed relative to each other.SOLUTION: An apparatus 10 includes a driving unit 16 having a plurality of coaxial driving shafts, an arm assembly 12 having a first arm 20 and a second arm 24, and a controller 11. The first arm contains a first upper arm, a first front arm, a first end effector, and a first transmission device. The first transmission device contains a non-circular pulley, and the first upper arm and the first forearm have unequal effective lengths. The second arm contains a second upper arm, a second forearm, a second end effector 26, and a second transmission device. The second upper arm and the second forearm have substantially equal effective lengths. The controller is configured to cause the driving unit to extend and retract the arms to move an upper substrate 14b and a lower substrate 14a on substrate holding areas such that the arm assembly and the upper substrate do not travel over the lower substrate.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] Exemplary and non - limiting embodiments generally relate to robots, and more particularly to robotic arms having an asymmetric end - effector with substrate - holding areas that are diagonal to each other. Brief Description of the Related Art

[0002] Processes for the manufacture of semiconductors, LEDs, solar, MEMS, or other devices utilize robotics and other forms of automation to transport substrates and carriers associated with the substrates to, from, and between storage locations, processing locations, or other locations. Such substrate transport can involve moving individual substrates or groups of substrates with a single arm that transports one or more substrates, or multiple arms each of which transports one or more substrates. For example, most of the manufacturing associated with semiconductor manufacturing is performed in a vacuum environment where floor space and volume are limited. Further, most automated transport is performed to achieve maximum - efficiency substrate movement within the volume of the workspace. Thus, there is a need to provide substrate - transport automation that utilizes a minimum floor space and workspace volume for a given range of transport applications with maximized movement efficiency. Summary

[0003] The following summary is intended to be merely exemplary and not intended to limit the claims.

[0004] According to one aspect, an exemplary embodiment provides an apparatus comprising a drive unit having a motor and a plurality of coaxial drive shafts, an arm assembly connected to the coaxial drive shafts and having a first arm and a second arm, and a controller configured to control the motor. The first arm includes a first upper arm connected to a first coaxial drive shaft of the coaxial drive shafts, a first forearm connected to the first upper arm, a first end effector connected to the first forearm, and a first transmission for rotating the first end effector on the first forearm. The first transmission includes at least one non-circular pulley. The first end effector includes a first substrate holding area. The first upper arm and the first forearm have unequal effective lengths. The second arm includes a second upper arm connected to a second coaxial drive shaft of the coaxial drive shafts, a second forearm connected to the second upper arm, a second end effector connected to the second forearm, and a second transmission for rotating the second end effector on the second forearm. The second end effector includes a second substrate holding area. The second upper arm and the second forearm have substantially equal effective lengths. The controller is configured to extend and retract the arms of the drive unit so as to move the upper substrate and the lower substrate on the substrate holding areas such that the arm assembly and the upper substrate do not move above the lower substrate.

[0005] According to another aspect, an exemplary method is provided. The method includes extending and retracting a first arm of an arm assembly between a retracted position and an extended position, extending and retracting a second arm of the arm assembly between the retracted position and the extended position, and controlling the extension and retraction of the first and second arms such that the arm assembly and an upper substrate do not move above a lower substrate during the extension and retraction of the first and second arms between their respective retracted and extended positions. The first arm is connected to a first coaxial drive shaft of a robot drive unit. The first arm includes a first end effector having a first substrate holding area that holds the lower substrate thereon. The second arm is connected to a second coaxial drive shaft of the robot drive unit. The second arm includes a second end effector having a second substrate holding area that holds the upper substrate thereon.

[0006] According to another aspect, an exemplary embodiment provides a machine-readable non-transitory program storage device. The non-transitory program storage device actually embodies a program of instructions executable by the machine to perform operations. The operations include moving a first arm of an arm assembly to a robot drive unit by extending and retracting the first arm between a retracted position and an extended position, moving a second arm of the arm assembly to the robot drive unit by extending and retracting the second arm between the retracted position and the extended position, and controlling the extension and retraction of the first and second arms such that the arm assembly and an upper substrate do not move above a lower substrate. The first arm is connected to a first coaxial drive shaft of the robot drive unit. The first arm includes a first end effector having a first substrate holding area that holds the lower substrate thereon. The second arm is connected to a second coaxial drive shaft of the robot drive unit. The second arm includes a second end effector having a second substrate holding area that holds the upper substrate thereon.

Brief Description of the Drawings

[0007] The foregoing aspects and other features will be described in the following description together with the accompanying drawings.

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[0051] Referring to FIGS. 1A and 1B, the overall apparatus for moving a substrate is indicated at 10 and will hereinafter be referred to as "apparatus 10". Apparatus 10 includes, for example, a robot having a substrate transfer device or arm assembly 12 (hereinafter, "transfer device 12") configured to transfer substrates 14a, 14b between a substrate processing chamber and a load lock. Apparatus 10 also includes a drive unit 16 configured to drive the arms and a plurality of end effectors of transfer device 12, thereby transferring substrates. As an example, a robot having a plurality of end effectors is described in U.S. Patent Application No. 15 / 897,374, filed Feb. 15, 2018, now U.S. Patent No. 10,580,682, entitled "Material-Handling Robot With Multiple End-Effectors", the entire disclosure of which is incorporated herein by reference. Apparatus 10 may include or be connected to a controller 11. Controller 11 may include one or more processors 13 and one or more memories 15. Memory 15 may include software or computer code 17 configured to control motor movement in drive unit 16 and to receive sensor signals from sensors in drive unit 16 or transfer device 12. It should be understood that all of the embodiments described herein are connected to a certain type of controller, such as controller 11, to control movements of the arms, such as rotation about the central axis of drive unit 16 and extension and retraction of individual arms relative to the central axis of the drive unit. In alternative embodiments, other types of drive units may also be used.

[0052] The conveying device 12 includes a plurality of arms each of which is extendable and rotatable via a drive unit 16. The plurality of arms includes at least one non-circular pulley-driven uneven-link linkage mechanism or a first arm 20. The uneven-link linkage mechanism 20 in this example has an upper arm having a first effective length and a forearm rotatably connected to the upper arm with a second different effective length. The second effective length is shorter than the first effective length in this example. The effective length of the upper arm is measured between the axis of rotation of the upper arm at the drive unit 16 and the axis of rotation of the forearm on the upper arm. The effective length of the forearm is measured between the axis of rotation of the forearm on the upper arm and the axis of rotation of the end effector 22 on the forearm. Examples of non-circular pulleys and uneven link lengths are shown in U.S. Patent No. 9,840,004, which is hereby incorporated by reference in its entirety. The uneven-link linkage mechanism 20 includes a first end effector 22 for supporting the lower substrate 14a.

[0053] The plurality of arms also includes at least one equal-link linkage mechanism or a second arm 24. The equal-link linkage mechanism 24 includes a second end effector 26 for supporting the upper substrate 14b. The equal-link linkage mechanism 24 may include one or more circular pulleys instead of non-circular pulleys. The equal-link linkage mechanism 24 in this example has an upper arm having a third effective length and a forearm rotatably connected to the upper arm with a fourth effective length. The third effective length is substantially the same as the fourth effective length in this example. Thus, the term "equal-link" linkage mechanism is used to indicate the same or substantially the same effective lengths for the upper arm and the forearm in the same linkage mechanism.

[0054] The first end effector 22 and the second end effector 26 are asymmetric in this example. Thus, the apparatus 10 can be considered to have an asymmetric dual arm with stacked end effectors. As shown in FIG. 1B, the link mechanism 20 of unequal links is disposed at a distance D or more from the floor surface or reference surface 28. The configuration of the transfer device 12 provides the maximum radial reach from a given storage diameter. As an example, a robot having an arm with unequal link lengths is described in U.S. Patent No. 9,149,936, issued on October 6, 2015 (inventive name "Robot Having Arm With Unequal Link Lengths"), the entire disclosure of which is incorporated herein by reference.

[0055] Referring to FIGS. 2A-2C, the first position of the transfer device 12 is a retracted configuration in which a portion of the second end effector 26 is positioned over a portion of the first end effector 22 such that the upper substrate 14b is positioned over the lower substrate 14a (FIG. 2A). FIG. 2B shows that the first arm 20 is being moved from its retracted position in FIG. 2A toward its extended position shown in FIG. 2C. As the first end effector 22 supporting the lower substrate 14a extends, the wrist 30 on the link mechanism 20 of unequal links (first lower arm) passes along the side of the shoulder 40 on the link mechanism 24 of equal links (second upper arm). A similar movement occurs during the retraction of the same end effector. Without movement of the link mechanism 24 of equal links, when the first end effector 22 supporting the lower substrate 14a is fully extended (FIG. 2C), the length of the movement of the link mechanism 24 of equal links allows for storage and maximum movement of the wrist.

[0056] Referring also to FIG. 3, the entire substrate transfer apparatus for substrate processing having an angled end effector is indicated at 112 and will hereinafter be referred to as the "transfer apparatus 112". This example may also include a controller 11 as shown in FIG. 1, but has suitable software programming for driving the motor so that there is no movement above the substrate as will be described further below. This example shows an example of an asymmetric dual arm having an angled end effector. This example can be used to provide a system in which components or materials of the transfer apparatus 112 or the upper substrate 114b do not move above the lower end effector or the lower substrate 114a.

[0057] The transfer apparatus 112 includes a first lower arm having a link mechanism 120 of unequal links with a first end effector 122, and a second upper arm having an equal link mechanism 124 and a second end effector 126. The first end effector 122 is asymmetric with respect to the second end effector 126. The first end effector 122 has a substrate holding area, and this substrate holding area is also angled with respect to the substrate holding area of the second end effector 126. Thus, while in the initial rest position or retracted position, and also during movement of either or both of the lower and upper arms, the upper substrate 114b can be prevented from being positioned over the lower substrate 114a.

[0058] FIG. 4 shows a top view of the transfer device 112 shown in FIG. 3. In the example shown in FIGS. 3 and 4, (with respect to the link mechanism design shown by the stacked end effectors of FIGS. 1A, 1B, 2A-2C) the link mechanism design can rotate to move the upper wafer (substrate 114b) on the second end effector 126 away from the lower wafer (substrate 114a) on the first end effector 122. Similarly, in the example shown in FIGS. 3 and 4, (with respect to the link design in the equal-link link mechanism shown by the stacked end effectors of FIGS. 1A, 1B, 2A-2C) the link design in the equal-link link mechanism 124 can extend to place the elbow of the equal-link link mechanism 124 away from the wrist of the unequal-link link mechanism 120. The unequal-link link mechanism 120 can include a non-circular pulley and a belt or band. In certain examples, the software in the controller used for the example of FIGS. 3 and 4 to control the motor in the drive unit can be the same as the software in the controller used for the examples of FIGS. 1A, 1B, 2A-2C.

[0059] Referring also to FIG. 5A, in the stationary or retracted position, the configuration of the asymmetric and angled end effectors 122, 126 allows the wafer (substrate 114b) on the second end effector 126 not to be on top of the wafer (substrate 114a) on the first end effector 122. Referring also to FIG. 5B, when the unequal-link link mechanism 120 is extended, the first end effector 122 moves away from the second end effector 126. Referring also to FIG. 5C, when the unequal-link link mechanism 120 is further extended, the first end effector 122 moves further away from the second end effector 126. In these upper and lower arm structures, end effector shapes, and motor control by the controller 11, this example can be used to show that at any point during the extension and retraction of the unequal-link link mechanism 120 having the first end effector 122, no part of the transfer device 112 or the upper substrate 114b is placed on top of the lower substrate 114a.

[0060] Referring also to FIG. 6A, in the stationary or retracted position, due to the configuration of the end effector that is asymmetric and oblique, the upper wafer (substrate 114b) on the second end effector 126 is prevented from moving above the lower wafer (substrate 114a) on the first end effector 122 (see also FIG. 5A). Referring also to FIG. 6B, when the link mechanism 124 of the equal links is extended, the second end effector 126 moves away from the first end effector 122. Referring also to FIG. 6C, when the link mechanism 124 of the equal links is further extended towards its full extended position, the second end effector 126 moves further away from the first end effector 122. With these upper and lower arm structures, the shape of the end effectors, and the control of the motors by the controller 11, this example can be used to show that at any point during the extension and retraction of the link mechanism 124 with the equal links having the second end effector 126, no part of the transfer device 112 or the upper substrate 114b is placed above the lower substrate 114a or the substrate holding area of the lower end effector 122.

[0061] Referring to FIG. 7, a schematic top view of the transfer device 112 is shown with both arms in the retracted position. The link mechanism 120 of the unequal links includes a non-circular pulley and can be driven by this pulley. The other link mechanism 124 can include either an equal link link mechanism or an unequal link link mechanism having a non-circular pulley. Compared with the examples shown in FIGS. 1A and 1B, the design of the end effectors 122, 126 can rotate from the radial orientation to take additional spacing between them and between their respective elbows and wrists.

[0062] Referring to FIGS. 8A to 8C, regarding the extension of the link mechanism 124 of the equal links, in the first stage (FIG. 8A, the contracted position), the upper substrate 114b is not located on the lower substrate 114a. As shown in FIG. 8B, at the position where there is a link on the link when the upper substrate 114b is extended, the orientations of the end effectors 122 and 126 change as the center of the upper substrate 114b moves along a straight line. As shown in FIG. 8C, at the last stage where the substrate 114b is in the extended position, when the end effector 126 is further extended, the orientations of the end effectors 122 and 126 relative to each other are constant, and the center of the upper substrate 114b continues to move along a straight line. In this example, in the first stage of extension, the orientation of the end effector 126 changes while the center of the end effector moves along a straight line, and in the last stage of extension, the orientation of the end effector 126 remains constant while its center continues to move along a straight line.

[0063] Referring also to FIGS. 9A to 9C, regarding the extension of the link mechanism 120 of the unequal links, in the first stage (FIG. 9A, the contracted position), again, the upper substrate 114b is not located on the lower substrate 114a. As shown in FIG. 9B, at the position where there is a link on the link when the end effector 122 is extended, the orientations of the end effectors 122 and 126 change relative to each other as the center of the lower substrate 114a moves along a straight line. As shown in FIG. 9C, at the last stage where the lower substrate 114a moves toward its extended position, the orientations of the end effectors 122 and 126 relative to each other are constant, and the center of the lower substrate 114a continues to move along that straight line.

[0064] Features such as those described in this specification can provide a dual extension arm configuration that is diagonal. Referring also to FIG. 10A, an exemplary embodiment of a diagonal dual extension arm configuration is shown. In this example, the arm assembly 1012 includes a first arm 1014 and a second arm 1016. The two arms 1014, 1016 are connected to a drive unit such as the drive unit 16 shown in FIGS. 10B and 10C. The drive unit 16 can include coaxial drive shafts 1018, 1020, 1022, motors 1024, 1026, 1028 for rotating these drive shafts, and a vertical drive unit 1030. The first arm 1014 has an upper arm 1030, a forearm 1032, and an end effector 1034 configured to support the substrate A thereon. The second arm 1016 has an upper arm 1036, a forearm 1038, and an end effector 1040 configured to support the substrate B thereon. The arms 1014, 1016 include a pulley and a band as part of a transmission from the drive unit. FIGS. 10B and 10C show an example of a transmission having a band and a pulley. FIGS. 10B and 10C also show an exemplary mechanism of the links (upper arm, forearm, end effector) of the arms 1014', 1016'. FIGS. 10D and 10E show another alternative embodiment of the exemplary mechanism of the links (upper arm, forearm, end effector) of the arms 1014'', 1016''.

[0065] Referring also to FIGS. 11A to 11D, the movement of an exemplary embodiment of an arm assembly with a fixed wrist orientation is shown. In this example, it includes independent extension arm movement by a three-axis spindle, both link mechanisms 1114, 1116 of an equal link shape, and an end effector with a fixed orientation during extension and contraction.

[0066] Referring also to FIGS. 12A - 12D, the movement of an exemplary embodiment of an arm assembly with a fixed wrist orientation is shown. In this example, it includes an independent extensible arm movement, a 3 - axis spindle, link mechanisms 1214, 1216 of both unequal - link shapes, and an end - effector with a fixed orientation during extension and contraction. In this example, it has an overall L - shaped end - effector of 90 degrees. One or more of these end - effectors may be bent or curved at more than 90 degrees or less than 90 degrees, such as the bent end - effector shown in FIGS. 16A - 16D, for example.

[0067] Referring also to FIGS. 13A - 13D, the movement of an exemplary embodiment of an arm assembly with a fixed wrist orientation is shown. In this example, it includes an independent extensible arm movement, a 3 - axis spindle, one link mechanism 1314 of equal - link and the other link mechanism 1316 of unequal - link shape, and an end - effector with a fixed orientation during extension and contraction.

[0068] Referring also to FIGS. 14A - 14D, the movement of an exemplary embodiment of an arm assembly with a fixed wrist orientation is shown. In this example, it includes an independent extensible arm, a 3 - axis spindle, one link mechanism 1414 of unequal - link and the other link mechanism 1416 of equal - link shape, and an end - effector with a fixed orientation during extension and contraction.

[0069] Features as described herein may include a variable wrist orientation. This is shown by the example in FIG. 15. For example, the following features may be provided. · Independent extensible arm movement, 4 - axis spindle, link mechanisms of both equal - link shapes, end - effector with a variable orientation during extension and contraction · Independent extensible arm movement, 4 - axis spindle, link mechanisms of both unequal - link shapes, end - effector with a variable orientation during extension and contraction · Independent extension arm movement, 4-axis spindle, one link mechanism of equal links and the other link mechanism of unequal links (upper link mechanism of equal links, lower link mechanism of unequal links), end effector with variable orientation during extension and contraction

[0070] Referring also to FIGS. 16A - 16D, the movement of an exemplary embodiment of an arm assembly with variable wrist orientation is shown. In this example, it includes independent extension arm movement, a 4-axis spindle / drive unit, one link mechanism 1614 of unequal links and the other link mechanism 1616 of equal links (upper link mechanism of unequal links, lower link mechanism of equal links), and an end effector with variable orientation during extension and contraction. In this example, the end effector does not point radially in the retracted position.

[0071] Features as described herein may comprise a connected dual-arm mechanism. This is shown by the example shown in FIG. 17 having arms 1714 and 1716. FIG. 18 shows an example of the connection of the drive unit 16 to an exemplary embodiment of a connected dual-arm mechanism by pulleys and bands as part of the transmission in the arm assembly. FIG. 19 shows another example of the connection of the drive unit 16 to an exemplary embodiment of a connected dual-arm mechanism by pulleys and bands as part of the transmission in the arm assemblies 1714' and 1716'.

[0072] The connected dual-arm mechanism may include a fixed wrist orientation. FIGS. 20A-20D show an example including a connected dual arm (fixedly connected upper arm, left elbow and right elbow, left forearm and right forearm), a three-axis spindle / drive unit, link mechanisms 2014 and 2016 of both equal-link shapes, and an end effector with a fixed orientation during extension and contraction. FIGS. 21A-21D show an example including a connected dual arm (fixedly connected upper arm), a three-axis spindle, link mechanisms 2114 and 2116 of both unequal-link shapes, and an end effector with a fixed orientation during extension and contraction. FIGS. 22A-22D show an example including a connected dual arm (fixedly connected upper arm), a three-axis spindle, one link mechanism 2214 of equal-link and the other link mechanism 2216 of unequal-link shape, and an end effector with a fixed orientation during extension and contraction. FIGS. 23A-23D show an example including a connected dual arm (fixedly connected upper arm), a three-axis spindle, one link mechanism 2314 of unequal-link and the other link mechanism 2316 of equal-link shape, and an end effector with a fixed orientation during extension and contraction.

[0073] The connected dual-arm mechanism may include a variable wrist orientation. The following are examples. · A connected dual arm (fixedly connected upper arm, left elbow and right elbow, left forearm and right forearm), a three-axis spindle, link mechanisms of both equal-link shapes, an end effector with a variable orientation · A connected dual arm (fixedly connected upper arm), a three-axis spindle, link mechanisms of both unequal-link shapes, an end effector with a variable orientation · A connected dual arm (fixedly connected upper arm), a three-axis spindle, one link mechanism of equal-link and the other link mechanism of unequal-link shape, an end effector with a variable orientation · A connected dual arm (fixedly connected upper arm), a three-axis spindle, one link mechanism of unequal-link and the other link mechanism of equal-link shape, an end effector with a variable orientation

[0074] Features such as those described herein may include a single upper arm and a single elbow. An example having arms 2414 and 2416 is shown in FIG. 24. FIGS. 25A, 25B, 26A, and 26B show examples of the connection of drive unit 16 to an exemplary embodiment of a connected dual-arm mechanism by pulleys and bands as part of a transmission in an arm assembly similar to FIG. 24.

[0075] The single upper arm single elbow mechanism may include a fixed wrist orientation. FIGS. 27A-27D show examples including an arm with a common elbow (single upper arm, single elbow, stacked forearms), a 3-axis spindle, link mechanisms 2714 and 2716 of both equal-link shape, and an end effector with a fixed orientation during extension and contraction. FIGS. 28A-28D show examples including an arm with a common elbow (single upper arm, single elbow, stacked forearms), a 3-axis spindle, link mechanisms 2814 and 2816 of both unequal-link shape, and an end effector with a fixed orientation during extension and contraction. FIGS. 29A-29D show examples including an arm with a common elbow (single upper arm, single elbow, stacked forearms), a 3-axis spindle, one link mechanism 2914 of equal-link and the other link mechanism 2916 of unequal-link shape, and an end effector with a fixed orientation during extension and contraction. FIGS. 30A-30D show examples including an arm with a common elbow (single upper arm, single elbow, stacked forearms), a 3-axis spindle, one link mechanism 3014 of unequal-link and the other link mechanism 3016 of equal-link shape, and an end effector with a fixed orientation during extension and contraction.

[0076] The single upper arm single elbow mechanism may include a variable wrist orientation. The following are examples. · An arm with a common elbow (single upper arm, single elbow, stacked forearms), a 3-axis spindle, link mechanisms of both equal-link shape, and an end effector with a variable orientation · An arm with a common elbow (single upper arm, single elbow, stacked forearms), a 3-axis spindle, link mechanisms of both unequal-link shape, and an end effector with a variable orientation · An arm having a common elbow (a single upper arm, a single elbow, stacked forearms), a 3-axis spindle, one link mechanism of an equal link and the other link mechanism of an unequal link, an end effector with a variable orientation · An arm having a common elbow (a single upper arm, a single elbow, stacked forearms), a 3-axis spindle, one link mechanism of an unequal link and the other link mechanism of an equal link, an end effector with a variable orientation

[0077] Features as described herein may comprise a single upper arm with an offset elbow. An example having link mechanisms 3114 and 3116 is shown in FIG. 31. FIGS. 32A and 32B show examples of the connection of the drive unit 16 to an exemplary embodiment of a single upper arm having an offset elbow mechanism by means of pulleys and bands as part of the transmission in an arm assembly.

[0078] A single upper arm with an offset elbow mechanism may include a constant wrist orientation. FIGS. 33A - 33D show an example including an arm with an offset elbow (a single upper arm, two elbow joints), a 3-axis spindle, both link mechanisms 3314 and 3316 of an equal link shape, and an end effector with a constant orientation during extension and contraction. FIGS. 34A - 34D show an example including an arm with an offset elbow (a single upper arm, two elbow joints), a 3-axis spindle, both link mechanisms 3414 and 3416 of an unequal link shape, and an end effector with a constant orientation during extension and contraction. FIGS. 35A - 35D show an example including an arm with an offset elbow (a single upper arm, two elbow joints), a 3-axis spindle, one link mechanism 3514 of an equal link and the other link mechanism 3516 of an unequal link shape, and an end effector with a constant orientation during extension and contraction. FIGS. 36A - 36D show an example including an arm with an offset elbow (a single upper arm, two elbow joints), a 3-axis spindle, one link mechanism 3614 of an unequal link and the other link mechanism 3616 of an equal link shape, and an end effector with a constant orientation during extension and contraction.

[0079] A single upper arm with an offset elbow mechanism can include a variable wrist orientation. The following examples are given. · An arm with an offset elbow (single upper arm, two elbow joints), a 3-axis spindle, a link mechanism of both equal link shape, and an end effector of variable orientation · An arm with an offset elbow (single upper arm, two elbow joints), a 3-axis spindle, a link mechanism of both unequal link shape, and an end effector of variable orientation · An arm with an offset elbow (single upper arm, two elbow joints), a 3-axis spindle, a link mechanism of one equal link and a link mechanism of the other unequal link shape, and an end effector of variable orientation · An arm with an offset elbow (single upper arm, two elbow joints), a 3-axis spindle, a link mechanism of one unequal link and a link mechanism of the other equal link shape, and an end effector of variable orientation

[0080] According to one example, an apparatus may be provided. The apparatus includes a drive unit having a motor and a plurality of coaxial drive shafts, an arm assembly connected to the coaxial drive shafts and having a first arm and a second arm, and a controller configured to control the motor. The first arm includes a first upper arm connected to a first coaxial drive shaft of the coaxial drive shafts, a first forearm connected to the first upper arm, a first end effector connected to the first forearm, and a first transmission device for rotating the first end effector on the first forearm. The first transmission device includes at least one non-circular pulley. The first end effector includes a first substrate holding area. The first upper arm and the first forearm have unequal effective lengths. The second arm includes a second upper arm connected to a second coaxial drive shaft of the coaxial drive shafts, a second forearm connected to the second upper arm, a second end effector connected to the second forearm, and a second transmission device for rotating the second end effector on the second forearm. The second end effector includes a second substrate holding area. The second upper arm and the second forearm have substantially equal effective lengths. The controller is configured to extend and contract the arms of the drive unit so that the arm assembly and an upper substrate move the upper substrate and the lower substrate on the substrate holding area without moving above the lower substrate. The effective length is the length between the pivot axis positions at both ends of each link.

[0081] The controller may be configured to maintain the arm having the upper substrate in a stationary position relative to the drive unit while the controller extends and retracts the other arm. The controller may be configured to maintain the arm having the lower substrate in a stationary position relative to the drive unit while the controller extends and retracts the other arm. The second transmission device may include a pulley that is not a non-circular pulley. The first end effector may have a substantially bent shape, and the second end effector may have a substantially linear shape. The effective length of the first upper arm may be longer than the effective length of the first forearm. At the retracted positions of the first and second arms, the second end effector may be partially disposed on the first end effector, the second forearm may be partially disposed on the first forearm and the first end effector, and the first end effector may be partially disposed on the second upper arm. The controller, the structures of the first and second arms, and the transmission device may be configured to limit the movement of the first and second arms relative to each other so as to prevent the movement of the arm assembly and the upper substrate above the lower substrate for all locations of the end effector.

[0082] An exemplary method may be provided. The method includes extending and retracting a first arm of an arm assembly between a retracted position and an extended position, extending and retracting a second arm of the arm assembly between a retracted position and an extended position, and controlling the extension and retraction of the first and second arms such that the arm assembly and the upper substrate do not move above the lower substrate during the extension and retraction of the first and second arms between their respective retracted and extended positions. The first arm is connected to a first coaxial drive shaft of a robot drive unit. The first arm includes a first end effector having a first substrate holding area having the lower substrate thereon. The second arm is connected to a second coaxial drive shaft of the robot drive unit. The second arm includes a second end effector having a second substrate holding area having the upper substrate thereon.

[0083] The first arm may include a first upper arm connected to the first coaxial drive shaft, a first forearm connected to the first upper arm, a first end effector connected to the first forearm, and a first transmission device for rotating the first end effector on the first forearm. The first transmission device includes at least one non-circular pulley. The first upper arm and the first forearm have unequal effective lengths. The method includes rotating the first end effector on the first forearm when the first transmission device rotates the first upper arm by the first coaxial drive shaft. The second arm may include a second upper arm connected to the second coaxial drive shaft, a second forearm connected to the second upper arm, a second end effector connected to the second forearm, and a second transmission device for rotating the second end effector on the second forearm. The second upper arm and the second forearm have substantially equal effective lengths. The method includes rotating the second end effector on the second forearm when the second transmission device rotates the second upper arm by the second coaxial drive shaft. The second transmission device includes a pulley that is not a non-circular pulley. The control of the extension and contraction of the first and second arms may include the controller maintaining the second arm in a stationary position relative to the robot drive unit while the controller extends and contracts the first arm. The control of the extension and contraction of the first and second arms may include the controller maintaining the first arm in a stationary position relative to the robot drive unit while the controller extends and contracts the second arm. The first end effector may have a substantially bent shape, and the second end effector may have a substantially straight shape. The first arm may include a first upper arm and a first forearm. The effective length of the first upper arm is longer than the effective length of the first forearm. The second arm includes a second upper arm and a second forearm. The effective length of the second upper arm is longer than the effective length of the second forearm.In the retracted positions of the first and second arms, the second end effector may be partially disposed over the first end effector, the second forearm may be partially disposed over the first forearm and the first end effector, and the first end effector may be partially disposed over the second upper arm. The control of the extension and retraction of the first and second arms may include the controller, the structures of the first and second arms, and the transmissions within the arms restricting the movement of the first and second arms relative to each other so as to prevent the movement of the arm assembly and the upper substrate above the lower substrate for all locations of the end effectors.

[0084] In one example, a machine-readable non-transitory program storage device may be provided. This non-transitory program storage device actually embodies a program of instructions executable by the machine to perform operations. The operations include moving a first arm of an arm assembly to a robot drive unit by extending and retracting the first arm between a retracted position and an extended position; moving a second arm of the arm assembly to the robot drive unit by extending and retracting the second arm between a retracted position and an extended position; and controlling the extension and retraction of the first and second arms so that the arm assembly and the upper substrate do not move above the lower substrate. The first arm is connected to a first coaxial drive shaft of the robot drive unit. The first arm includes a first end effector having a first substrate holding area having the lower substrate thereon. The second arm is connected to a second coaxial drive shaft of the robot drive unit. The second arm includes a second end effector having a second substrate holding area having the upper substrate thereon.

[0085] The first arm may include a first upper arm connected to the first coaxial drive shaft, a first forearm connected to the first upper arm, a first end effector connected to the first forearm, and a first transmission device for rotating the first end effector on the first forearm. The first transmission device includes at least one non-circular pulley. The first upper arm and the first forearm have unequal effective lengths. The operation includes rotating the first end effector on the first forearm by the first transmission device when the first upper arm is rotated by the first coaxial drive shaft. The second arm may include a second upper arm connected to the second coaxial drive shaft, a second forearm connected to the second upper arm, a second end effector connected to the second forearm, and a second transmission device for rotating the second end effector on the second forearm. The second upper arm and the second forearm have substantially equal effective lengths. The operation includes rotating the second end effector on the second forearm by the second transmission device when the second upper arm is rotated by the second coaxial drive shaft. The second transmission device includes a pulley that is not a non-circular pulley.

[0086] An exemplary embodiment may be provided. This embodiment includes means for extending and retracting a first arm of an arm assembly between a retracted position and an extended position, means for extending and retracting a second arm of the arm assembly between a retracted position and an extended position, and means for controlling the extension and retraction of the first and second arms such that the arm assembly and an upper substrate do not move above a lower substrate during the extension and retraction of the first and second arms between their respective retracted and extended positions. The first arm is connected to a first coaxial drive shaft of a robot drive unit. The first arm includes a first end effector having a first substrate holding area that has the lower substrate thereon. The second arm is connected to a second coaxial drive shaft of the robot drive unit. The second arm includes a second end effector having a second substrate holding area that has the upper substrate thereon.

[0087] Exemplary embodiments can be provided. This embodiment includes a circuit configured to move a first arm of an arm assembly to a robot drive unit by extending and contracting the first arm between a retracted position and an extended position, a circuit configured to move a second arm of the arm assembly to the robot drive unit by extending and contracting the second arm between a retracted position and an extended position, and a circuit configured to control the extension and contraction of the first and second arms so that the arm assembly and an upper substrate do not move above a lower substrate. The first arm is connected to a first coaxial drive shaft of the robot drive unit. The first arm includes a first end effector having a first substrate holding area having the lower substrate thereon. The second arm is connected to a second coaxial drive shaft of the robot drive unit. The second arm includes a second end effector having a second substrate holding area having the upper substrate thereon.

[0088] Exemplary embodiments may provide an apparatus comprising at least one processor and at least one non-transitory memory including computer program code. The at least one memory and the computer program code are configured to, by the at least one processor, cause the apparatus to move a first arm of an arm assembly to a robot drive unit by extending and contracting the first arm between a retracted position and an extended position, move a second arm of the arm assembly to the robot drive unit by extending and contracting the second arm between a retracted position and an extended position, and control the extension and contraction of the first and second arms so that the arm assembly and an upper substrate do not move above a lower substrate. The first arm is connected to a first coaxial drive shaft of the robot drive unit. The first arm comprises a first end effector having a first substrate holding area having the lower substrate thereon. The second arm is connected to a second coaxial drive shaft of the robot drive unit. The second arm comprises a second end effector having a second substrate holding area having the upper substrate thereon.

[0089] Additional exemplary embodiments may provide a robot having two link mechanisms that can extend independently as described above and, in addition, may be able to rotate independently. The ability of the two link mechanisms to rotate independently allows the arm to transition between a configuration having stacked end effectors, which may be advantageous when high-speed material exchange is required, and a configuration having angled end effectors, which may be advantageous from the perspective of material contamination. Further, the ability of the two link mechanisms to rotate independently allows one of the link mechanisms to rotate towards the next workstation (or other destination) before the other link mechanism completes its operation at the current workstation (current location), thereby improving productivity (system throughput).

[0090] The robot drive unit may provide four coaxial drive shafts, such as one additional axis of motion compared to the above-described embodiments, and may be configured to drive a robot arm. The robot arm may be basically the same as the above-described one, but may be characterized by two link mechanisms having a structure that can rotate independently of each other.

[0091] Referring also to FIGS. 37A - 37C, an exemplary embodiment of a robot having a robot drive unit and a robot arm is shown. The robot drive unit may be composed of a spindle having a motor configured to drive four coaxial shafts (in order from the outermost shaft to the innermost shaft) T1, T2, T3, and T4. If desired, the drive unit may further include a vertical lifting mechanism (not shown in FIGS. 37A - 37C) composed of one or more linear rail bearing mechanisms and a motor-driven ball screw configured to move the spindle vertically up and down.

[0092] The robot arm may be composed of a right link mechanism 3714 and a left link mechanism 3716. The right link mechanism 3714 may be composed of a wrist assembly having an upper right arm 3730, a right forearm 3732, and an end effector 3740. The upper right arm 3730 may be connected to the shaft T3. The right forearm may be connected to the upper arm via a rotary joint (elbow joint) and may be driven by the shaft T4 using a transmission mechanism. This transmission mechanism may include a shoulder pulley that can be attached to the shaft T4, a first elbow pulley that can be attached to the right forearm 3732, and a band, belt, or cable that can transmit motion between the two pulleys. The wrist assembly having the end effector 3740 may be connected to the right forearm via another rotary joint (wrist joint) and may have its rotation restricted by another transmission mechanism. This transmission mechanism may include a second elbow pulley that can be attached to the upper right arm, a wrist pulley that can be attached to the wrist assembly having the end effector, and a band, belt, or cable that can connect these two pulleys.

[0093] The length between the joints of the right forearm may be equal to the length between the joints of the right upper arm. The transmission mechanism between the shaft T4 and the right forearm may be configured such that when the shaft T3 rotates while the shaft T4 remains stationary, the wrist joint moves along a substantially straight radial line (passing through the axis of rotation of the coaxial drive shaft). To achieve this, the shoulder pulley and the first elbow pulley may be circular, and the effective diameter of the shoulder pulley may be selected to be twice the effective diameter of the first elbow pulley. The transmission ratio of the transmission mechanism between the right upper arm 3730 and the wrist assembly having the end effector may be configured such that the orientation of the wrist assembly having the end effector remains substantially constant during this operation. To achieve this, the second shoulder pulley and the wrist pulley may be circular, and the effective diameter of the wrist pulley may be selected to be twice the effective diameter of the second elbow pulley.

[0094] Alternatively, the length between the joints of the right forearm may not be equal to the length between the joints of the right upper arm. For example, the length between the joints of the right forearm may be shorter or longer than the length between the joints of the right upper arm. The transmission mechanism between the shaft T4 and the right forearm may be configured such that when the shaft T3 rotates while the shaft T4 remains stationary, the wrist joint moves along a substantial straight line (parallel to the line passing through the axis of rotation of the coaxial drive shaft). To achieve this, at least one of the pulleys of the transmission mechanism may be characterized by a non-circular contour. In addition, the transmission ratio of the transmission mechanism between the right upper arm and the wrist assembly having the end effector may be configured such that the orientation of the wrist assembly having the end effector remains substantially constant during this operation. To achieve this, at least one of the pulleys of the transmission mechanism may be characterized by a non-circular contour.

[0095] The left link mechanism 3716 may be composed of a left upper arm 3736, a left forearm 3738, and a wrist assembly having an end effector 3741. The left upper arm 3736 may be attached to the shaft T1. The left forearm 3738 may be connected to the upper arm via a rotating joint (elbow joint). The wrist assembly having the end effector 3741 may be connected to the forearm 3738 via another rotating joint (wrist joint).

[0096] The length between the joints of the left forearm may be shorter than the length between the joints of the left upper arm. In particular, the length of the left forearm may be advantageously selected such that the wrist joint passes through the shoulder joint of the right link mechanism 3714 and thus enables a vertically compact arm package. The left forearm can be driven by a shaft T2 using a transmission mechanism. This transmission mechanism may include a shoulder pulley that can be attached to the shaft T2, a first elbow pulley that can be attached to the left forearm, and a band, belt, or cable that can transmit motion between the two pulleys. At least one of the two pulleys may feature a non-circular contour to provide a variable (position-dependent) transmission ratio. The wrist assembly having the end effector 3741 can have its rotation restricted by another transmission mechanism. This transmission mechanism may include a second elbow pulley that can be attached to the upper arm 3736, a wrist pulley that can be attached to the wrist assembly having the end effector 3741, and a band, belt, or cable that can connect these two pulleys. Again, at least one of the two pulleys may feature a non-circular contour to provide a variable (position-dependent) transmission ratio.

[0097] The transmission mechanism between the shaft T2 and the left forearm 3738 can be configured such that when the shaft T1 rotates while the shaft T2 remains stationary, the wrist joint moves along a substantial straight line (parallel to the line passing through the axis of rotation of the coaxial drive shaft). This can be achieved through the non-circular contour of at least one of the two pulleys within the transmission mechanism. The transmission ratio of the transmission mechanism between the left upper arm 3736 and the wrist and end effector assembly 3741 can be configured such that the orientation of the wrist assembly having the end effector 3741 remains substantially constant during this operation. Again, this can be achieved through the non-circular contour of at least one of the two pulleys within the transmission mechanism.

[0098] The T1, T2, T3, and T4 shafts of the robot drive unit can rotate so that the end effectors 3740 and 3741 can access various workstations.

[0099] For the entire robot arm to rotate, all drive shafts, namely T1, T2, T3, and T4, need to move the same amount in the desired direction of arm rotation. For the right link mechanism to rotate independently, drive shafts T3 and T4 need to move the same amount in the desired direction of arm rotation. Similarly, for the left link mechanism to rotate independently, drive shafts T1 and T2 need to move the same amount in the desired direction of arm rotation.

[0100] The ability of the two link mechanisms to rotate independently enables the arm to transition between a configuration having a stacked end effector (see FIG. 38A), which can be advantageous when rapid material exchange is required, and a configuration having an angled end effector (see FIG. 38B), which can be advantageous from the perspective of material contamination.

[0101] Also refer to FIGS. 38D - 38I, which show the arms of FIGS. 38A - 38C in different positions, orientations, and relative movements. For end effector 3740 to extend from the retracted position to the workstation along a substantially straight path, shaft T4 can remain stationary and shaft T3 can rotate counterclockwise. For end effector 3741 to extend from the retracted position to the workstation along a substantially straight path, shaft T2 can remain stationary and shaft T1 can rotate clockwise.

[0102] The above operations can be utilized to pick / place materials from / to the workstation. A series of operations where a pick operation by one end effector is followed by a place operation by the other end effector can be used to quickly exchange materials at the workstation (rapid exchange operation). As an example, end effector 3740 can extend to the workstation, pick up the material, and retract. Then, end effector 3741, which can transport another material, can extend to the same station, place the material, and retract.

[0103] Since the two link mechanisms can rotate independently (refer to FIG. 38C with respect to FIGS. 38A and 38B), one of the link mechanisms can rotate toward the next workstation (or other destination) before the other link mechanism completes its operation at the current workstation (current location), so productivity (system throughput) can be further improved. For example, considering the above example of a rapid exchange operation, the right link mechanism 3714 can start rotating toward the next workstation (or other destination) before the left link mechanism 3716 completes its placement operation.

[0104] Referring also to FIG. 39, in another exemplary embodiment, the transmission mechanism between the drive shaft T4 and the right forearm can also include a shoulder pulley that can be attached to the shaft T4, a first elbow pulley that can be attached to the right forearm, and a band, belt, or cable that can transmit motion between the two pulleys. However, unlike the embodiments of FIGS. 37 and 38, the two pulleys can be characterized by a conventional circular profile having a transmission ratio that does not depend on any fixed position. For example, the two pulleys can have the same effective diameter and a transmission ratio of 1:1. The wrist assembly having the end effector 3740 can be rotationally restricted by another transmission mechanism, which can be the same as that of the previous embodiment.

[0105] Similarly, the transmission mechanism between the drive shaft T2 and the left forearm can also include a shoulder pulley that can be attached to the shaft T2, a first elbow pulley that can be attached to the left forearm, and a band, belt, or cable that can transmit motion between the two pulleys. However, compared to the embodiments of FIGS. 37 and 38, the two pulleys are characterized by a conventional circular profile and can have a transmission ratio that does not depend on a fixed position. For example, the two pulleys can have the same effective diameter and a transmission ratio of 1:1. Alternatively, any suitable transmission ratio can be used. The wrist assembly having the end effector 3741 can be rotationally restricted by another transmission mechanism, which can be the same as that of the previous embodiment.

[0106] The transmission mechanism between the drive shaft T4 and the right forearm can have a transmission ratio that does not depend on any fixed position, for example, a transmission ratio of 1:1. Therefore, the shoulder pulley, and thus the shoulder joint, can have a smaller diameter. A smaller shoulder joint provides more space for the left forearm and allows the length between the joints of the left forearm to be greater, which can then provide a longer extension of the end effector 3741.

[0107] For the entire robotic arm to rotate, all drive shafts, namely T1, T2, T3, and T4, need to move the same amount in the desired direction of rotation of the arm. For the right link mechanism to rotate independently, the drive shafts T3 and T4 need to move the same amount in the desired direction of rotation of the arm. Similarly, for the left link mechanism to rotate independently, the drive shafts T1 and T2 need to move the same amount in the desired direction of rotation of the arm. This is the same as in the embodiments of FIGS. 37 and 38.

[0108] For the end effector 3740 to extend from the retracted position to the workstation along a predefined path such as a straight radial path, the drive shafts T3 and T4 can rotate in cooperation, respectively, in the counterclockwise and clockwise directions. The inverse kinematic equations for the right link mechanism 3714 can be utilized to determine the orientations of the drive shafts T3 and T4 according to the position of the right end effector 3740. The right end effector 3740 can be retracted by rotating the drive shafts T3 and T4 backward in a similar manner.

[0109] In the special case where the upper left arm and the left forearm have the same length between joints and the shoulder pulley and the first elbow pulley have the same effective diameter, the end effector can be extended and retracted along a straight radial path by synchronously rotating the drive shafts T3 and T4 in opposite directions by the same amount.

[0110] In order for the end effector 3741 to extend from the retracted position to the workstation along a predefined path such as a straight radial path, the drive shafts T1 and T2 can cooperate to rotate in the clockwise and counterclockwise directions respectively. The inverse kinematic equations for the left link mechanism can be utilized to determine the directions of the drive shafts T1 and T2 according to the position of the left end effector 3741. The left end effector 3741 can be retracted by rotating the drive shafts T1 and T2 backward in a similar manner.

[0111] The main functional differences between the embodiments of FIGS. 37C and 39 can be summarized as follows. In the embodiment of FIG. 37C, each link mechanism of the arm can be contracted and extended by rotating a single drive shaft. This is possible because the transmission mechanism between the drive shaft corresponding to the forearm is configured to automatically control the angular position of the forearm according to the angular position of the corresponding upper arm. This is different from the embodiment of FIG. 39 where the cooperative rotation of the drive shafts driving the upper arm and the forearm is required. However, in the embodiment of FIG. 39, the shoulder pulley, and thus the shoulder joint, can have a smaller diameter. A smaller shoulder joint can provide more space for the left forearm and can increase the length between the joints of the left forearm, which can then provide a longer extension of the end effector 3741.

[0112] The description of the above embodiments shows the right upper arm attached to the shaft T3 and the right forearm connected to the shaft T4 (the innermost shaft), but the right upper arm may be attached to the shaft T4 (the innermost shaft), and the right forearm may be connected to the shaft T3. Similarly, the left upper arm attached to the shaft T1 (the outermost shaft) is shown, and the left forearm connected to the shaft T2 is shown, but the left upper arm may be attached to the shaft T2, and the left forearm may be connected to the shaft T1 (the outermost shaft). Alternatively, the links of the link mechanism of the arm may be connected to the shafts of the drive unit in any suitable manner.

[0113] Note that the features of the above exemplary embodiments may be combined. For example, the right link mechanism may be configured according to the embodiment of FIG. 37C, and the left link mechanism may be configured according to the embodiment of FIG. 39, or the right link mechanism may be configured according to the embodiment of FIG. 39, and the left link mechanism may be configured according to the embodiment of FIG. 37C.

[0114] Also, the arm may be designed as a mirror image of the above exemplary embodiments, that is, the above mechanism as part of the right link mechanism 3714 may be used in the left link mechanism of the arm, and the above mechanism as part of the left link mechanism may be used in the right link mechanism of the arm.

[0115] Alternatively, the features of the above exemplary embodiments may be used in any suitable mechanism and combinations thereof.

[0116] It should be understood that the foregoing description is merely illustrative. Various alternatives and modifications may be devised by those skilled in the art. For example, the features recited in the various dependent claims may be combined with each other in any suitable combination(s). In addition, features from the different embodiments described above may be selectively combined into new embodiments. Accordingly, the foregoing description is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the appended claims.

Claims

1. a drive section having a motor and a plurality of coaxial drive shafts; an arm assembly connected to the coaxial drive shaft, the arm assembly having a first arm and a second arm; a controller configured to control the motor; An apparatus comprising: the first arm includes a first upper arm connected to a first one of the coaxial drive shafts, a first forearm connected to the first upper arm, a first end effector connected to the first forearm, and a first transmission for rotating the first end effector on the first forearm; the first transmission comprises at least one non-circular pulley; the first end effector comprises a first substrate holding area; the first upper arm and the first forearm have unequal effective lengths; the second arm includes a second upper arm connected to a second one of the coaxial drive shafts, a second forearm connected to the second upper arm, a second end effector connected to the second forearm, and a second transmission for rotating the second end effector on the second forearm; the second end effector comprises a second substrate holding area; the second upper arm and the second forearm have substantially equal effective lengths; the controller is configured to cause the actuator to extend and retract the arm to move the upper substrate and the lower substrate over the substrate holding area such that the arm assembly and the upper substrate do not move above the lower substrate; in a retracted position of the first and second arms, the second end effector is partially disposed over the first end effector, the second forearm is partially disposed over the first forearm and the first end effector, and the first end effector is partially disposed over a second upper arm; Device.

2. The apparatus of claim 1 , wherein the controller is configured to maintain the arm having the upper substrate in a stationary position relative to the drive while the controller extends and retracts the other arm.

3. The apparatus of claim 2 , wherein the controller is configured to maintain the arm having the lower substrate in a stationary position relative to the drive while the controller extends and retracts the other arm.

4. The apparatus of claim 1 , wherein the second transmission comprises a pulley that is not a non-circular pulley.

5. The apparatus of claim 1 , wherein the effective length of the first upper arm is greater than the effective length of the first forearm.

6. 2. The apparatus of claim 1, wherein the controller, the first and second arm structures, and the transmission are configured to limit movement of the first and second arms relative to each other to prevent movement of the arm assembly and upper substrate above the lower substrate for all locations of the end effector.

7. extending and retracting a first arm of the arm assembly between a retracted position and an extended position; extending and retracting a second arm of the arm assembly between a retracted position and an extended position; controlling the extension and retraction of the first and second arms such that the arm assemblies and upper base plate do not move above the lower base plate during the extension and retraction of the first and second arms between their respective retracted and extended positions; A method comprising: the first arm is connected to a first coaxial drive shaft of a robot drive; the first arm comprises a first upper arm, a first forearm, and a first end effector having a first substrate holding area having the lower substrate thereon; the second arm is connected to a second coaxial drive shaft of the robot drive; the second arm includes a second upper arm, a second forearm, and a second end effector having a second substrate holding area having the upper substrate thereon; in the retracted position of the first and second arms, the second end effector is partially disposed over the first end effector, the second forearm is partially disposed over the first forearm and the first end effector, and the first end effector is partially disposed over a second upper arm. method.

8. the first arm comprises the first upper arm connected to the first coaxial drive shaft, the first forearm connected to the first upper arm, the first end effector connected to the first forearm, and a first transmission for rotating the first end effector on the first forearm; the first transmission comprises at least one non-circular pulley; the first upper arm and the first forearm have unequal effective lengths; 8. The method of claim 7, further comprising: the first transmission causing the first end effector to rotate on the first forearm when the first upper arm is rotated by the first coaxial drive shaft.

9. the second arm comprises a second upper arm connected to the second coaxial drive shaft, a second forearm connected to the second upper arm, a second end effector connected to the second forearm, and a second transmission for rotating the second end effector on the second forearm; the second upper arm and the second forearm have substantially equal effective lengths; the method includes the second transmission rotating the second end effector on the second forearm when the second upper arm is rotated by the second coaxial drive shaft; The method of claim 8 , wherein the second transmission comprises a pulley that is not a non-circular pulley.

10. 8. The method of claim 7, wherein the controlling the extension and retraction of the first and second arms includes the controller maintaining the second arm in a stationary position relative to the robot drive while the controller extends and retracts the first arm.

11. 11. The method of claim 10, wherein the controlling the extension and retraction of the first and second arms includes the controller maintaining the first arm in a stationary position relative to the robot drive while the controller extends and retracts the second arm.

12. an effective length of the first upper arm is greater than an effective length of the first forearm; The method of claim 7 , wherein an effective length of the second upper arm is greater than an effective length of the second forearm.

13. 8. The method of claim 7, wherein the control of the extension and contraction of the first and second arms includes limiting movement of the first and second arms relative to one another such that a controller, structure of the first and second arms, and transmissions within the arms prevent the movement of the arm assembly and upper substrate above the lower substrate for all locations of the end effector.

14. A computer program comprising program instructions arranged, when executed by a processing means of an apparatus, to cause said apparatus to perform a method according to any of claims 7 to 13.

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