Visualization robot with optimized kinematics for ophthalmic surgery

Abstract

The robotic system includes a base, a support column, and a selectively compliant articulated robotic arm (SCARA) connected to the base via the support column. The SCARA is configured with ophthalmic visualization intrinsic kinematics. The SCARA includes first, second, and third rotary joints. A first link is connected to the base via the first rotary joint. A second link is connected to the first link via the second rotary joint and has a distal end connected to the third rotary joint, configured as a four-bar mechanism. The second link is connectable to a microscope. A linear actuator is connected to the second link. In response to electronic control signals from an electronic control unit, the linear actuator controls the vertical movement of the SCARA. None of the rotary joints of the SCARA function in anti-gravity mode.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 488,083, filed March 2, 2023, and U.S. Provisional Patent Application No. 63 / 504,273, filed May 25, 2023, each of which is incorporated by reference herein in its entirety. [Background technology]

[0002] Introduction Serial robots are used in a wide range of industrial and medical applications. A typical serial robot includes an articulated arm with multiple rigid bars, segments, or links. The links are interconnected through revolute joints to form an open kinematic chain. As understood in the art, a robot arm with open chain kinematics includes a continuous arrangement of links and joints, the most distal of which are freely movable within a well-defined operating space. High stiffness is provided through the constituent joints, and each respective joint is either actuated (“actively driven”) or unactuated (“passively movable”) to control the joint angle and relative motion / orientation of the interconnected links.

[0003] In serial robotic arms of the type used to support digital or analog microscopes for visualization during ophthalmic procedures, the distal link of the serial robotic arm can be securely connected to such a microscope via a suitable end effector. For example, the serial robotic arm can be connected to the optical head of the microscope via a mounting bracket. Movement of the serial robotic arm through the available degrees of freedom of movement ultimately enables the end effector and connected microscope to reach a desired position and orientation in free space, such as when positioning the optical head relative to a patient's head or body in an ophthalmic operating room. Summary of the Invention [Means for solving the problem]

[0004] Disclosed herein is a robotic system having a serial robotic arm. In the illustrated embodiment, the robotic arm, having five degrees of freedom, is constructed according to predetermined surgical task-specific kinematics. In particular, the kinematics are optimized for supporting and positioning a digital or analog microscope for visualization of the ocular anatomical structures associated with ophthalmic procedures, such as cataract or vitreoretinal surgical applications. Typical serial robotic arms used in such environments can experience problematic singularities, potential instability, and payload limitations. Therefore, the optimized kinematics contemplated herein are specifically directed to solving the types of payload positioning problems frequently encountered by ophthalmic surgeons when positioning a microscope with the assistance of a serial robotic arm.

[0005] According to aspects of the present disclosure, a robotic system described herein includes a selectively compliant articulated robotic arm (SCARA) connected to a base. The SCARA in turn includes multiple links and joints. A first of the constituent links is connected to the base via a first of the joints (the "first rotary joint"). A second link, connected to the first link via a second of the joints (the "second rotary joint"), has a distal end connected to a third of the joints (the "third rotary joint"). The second link in this particular embodiment is configured as a four-bar mechanism, which is connectable to an ophthalmic microscope. A linear actuator, such as a non-back-driven vertical harmonic drive unit, may be connected to the second link to control the vertical movement of the second link and, therefore, the connected microscope. A defining characteristic of the SCARA is that none of the SCARA's rotary joints function in anti-gravity mode.

[0006] An embodiment of the robotic system may include multiple harmonic drive units, and at least one of the revolute joints of the SCARA is powered by a corresponding one of the harmonic drive units in response to an electronic control signal. For example, each of the revolute joints of the SCARA may be individually powered by a corresponding one of the harmonic drive units in response to an electronic control signal.

[0007] The robotic system may include a microscope and a bracket attached to the distal end of the second link. The microscope in such embodiments may be attached to the bracket. The microscope may be embodied as a digital or analog ophthalmic microscope having an optical head. In such a configuration, the base may be placed on the floor with the optical head having a pitch axis positioned parallel to the floor. The pitch and rotation of the optical head may be selectively lockable. A position sensor may be connected to the optical head and in communication with the ECU. In some implementations, an optional gas spring counterbalance device is operably connected to the second link.

[0008] One aspect of the present disclosure includes the first link and the second link being constructed of a suitable material, for example, a powder metallurgy alloy-like material made using cold isostatic pressing, and possibly containing aluminum and beryllium.

[0009] Also disclosed herein is a SCARA for use with a microscope and a base. This embodiment of the SCARA includes a first link connectable to the base via the first rotary joint, along with multiple rotary joints including a first rotary joint, a second rotary joint, and a third rotary joint. The second link is connected to the first link via the second rotary joint and has a distal end connected to the third rotary joint, configured as a four-bar mechanism. The second link is configured to connect to the microscope. In this embodiment, a linear actuator is connected to the second link and configured to control its vertical movement in response to electronic control signals from an ECU. The linear actuator includes a non-back-driveable vertical harmonic drive unit, and none of the SCARA's rotary joints function in anti-gravity mode.

[0010] The above-mentioned features and advantages of the present disclosure, as well as other possible features and advantages, will become apparent from the following detailed description of the best mode for carrying out the disclosure when taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram of an exemplary ophthalmic operating room having a robotic system configured as described herein. [Figure 2] FIG. 2 is a top view of a selectively compliant articulated robotic arm (SCARA) that can be used as part of the example robotic system shown in FIG. 1. [Figure 3] FIG. 3 is a side view of the exemplary embodiment of the SCARA shown in FIG. 2. [Figure 4] 4 illustrates an exemplary payload in the form of an ophthalmic microscope that can be connected to the distal end of the SCARA shown in FIGS. 2 and 3. DETAILED DESCRIPTION OF THE INVENTION

[0012] The solutions of the present disclosure may be modified or presented in alternative forms. Exemplary embodiments of the present disclosure are shown in the drawings by way of non-limiting examples and are described in more detail below. However, the inventive aspects of the present disclosure are not limited to the disclosed embodiments. Rather, the present disclosure is intended to encompass alternative forms that fall within the scope of the present disclosure as defined by the appended claims.

[0013] Embodiments of the present disclosure are described herein. However, it will be understood that the disclosed embodiments are merely exemplary, and that other embodiments may take various alternative forms. The drawings are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art how to employ the present disclosure in various ways.

[0014] Referring to the drawings, wherein like reference numerals refer to like components, a representative ophthalmic operating room 10 is shown generally in FIG. 1. The ophthalmic operating room 10 includes a robotic system 11 having a multi-axis visualization robot 12 and an operating table 14. During the performance of a vitreoretinal, cataract, or other ophthalmic surgical procedure in the operating room 10, a patient (not shown) may be positioned on the operating table 14 or another suitable platform, with a surgeon (not shown) seated on a stool 140. While omitted from FIG. 1 for ease of illustration, the respective heights of the operating table 14 and stool 140 may, in a typical implementation, be adjusted with the aid of automatic and / or manual knobs, levers, or foot pedals.

[0015] The visualization robot 12 includes a base 13 mounted or positioned relative to the floor 50 of the ophthalmic operating room 10, e.g., directly or via a mobile platform having lockable wheels 16 as shown. The base 13 in the exemplary embodiment of FIG. 1 is connected via an intervening support column 130 to a selectively compliant articulated robotic arm (SCARA) 15, which is constructed with visualization application-specific kinematics as described below with particular reference to FIGS. 2, 3, and 4. Generally, the SCARA 15 is configured as an articulated serial robotic arm with improved performance capabilities compared to typical serial robots when used to support visualization equipment in preparation for or in conjunction with ophthalmic surgery as it is performed within the operating room 10. At least some of the associated improvements include elimination of associated singularities, improved stability, and more robust handling of relatively heavy or bulky payloads, such as an ophthalmic microscope 17 and its attached optical head 170. Another important attribute is that the SCARA15 and any attached payload will not fall or tip over if power is lost or turned off.

[0016] A singularity commonly experienced in operating rooms, such as the exemplary ophthalmic operating room 10 of FIG. 1, can prevent a high-resolution display screen 20, e.g., a high-resolution medical display screen, from being positioned directly in front of the attending surgeon. This requires the surgeon to rotate their head to properly view the display screen 20 during visualization. Another common singularity results in interference with the free motion of a robotic arm. This is often caused by contact between the robotic arm and the patient's chest as the surgeon moves the robotic arm and thereby positions the optical head 170. Accordingly, the SCARA 15 described in detail herein is intended to address these and other positioning issues commonly associated with serial robotic arms, thus improving on the current state of the art in robot-assisted visualization.

[0017] In particular, the application-specific kinematics of the SCARA 15 of Figures 1-4 are specific to visualization efforts performed in assisting with cataract, glaucoma, corneal, and vitreoretinal ("VR") surgery, as contemplated herein. The distal end E1 of a typical serial robot (not shown) is securely connected to an optical head 170 through which the surgeon views the patient's ocular anatomy at high magnification. For example, using associated hardware and software, the surgeon can view high-magnification images 18 and 118 of, for example, the retina 25 via a display screen 20 after properly positioning the optical head 170. Smaller additional display screens 200 may be positioned elsewhere in the ophthalmic operating room 10 to facilitate viewing by other medical personnel when assisting the surgeon.

[0018] Thus, the optical head 170 in this example functions as a payload when the optical head 170 is securely connected to the distal end E1 of the SCARA 15, for example, via the camera bracket 19. Gravity (arrow GG) acts on the SCARA 15 and the connected optical head 170 when the digital microscope 17 is positioned above the operating table 14 as shown. As will be described below, a feature of this solution is that none of the various joints J1, J2, and J3 described below function in anti-gravity mode. That is, the rotation axis of each of the three rotation joints of the SCARA 15 is perpendicular to the floor 50, i.e., the horizontal plane. The optical head 170 of the microscope 17 described below with reference to FIG. 4 has a pitch axis A arranged parallel to the plane of the floor 50. P The pitch joint axis of the optical head 170 is located at the center of mass of the optical head 170, and therefore there is no rotational force due to gravity (arrow GG). The four-bar mechanism 400 described herein uses a non-rear-drivable linear actuator to move the optical head 170 up and down against gravity. If the three axes of the SCARA 15 are configured as passive axes, gas springs can be used for gravity compensation.

[0019] As understood in the art, an ophthalmic microscope, such as microscope 17 shown in FIG. 1, is comprised of several major components. Optical head 170 includes various lenses and optics for magnifying and illuminating a patient's eye during a given procedure. While omitted from FIG. 1 for ease of explanation, optical head 170 may include an objective lens and zoom section providing different magnifications, a pair of eyepieces through which the surgeon views a magnified image of the eye, and a controllable light source. The total weight of such lenses and other hardware in optical head 170 must be supported by SCARA 15 while achieving the desired movement and positioning functions contemplated herein, even during a loss of power to robotic system 11.

[0020] 1 is a cabinet 22 and an electronic control unit (ECU) 23. The ECU 23, e.g., one or more computing devices with computer-readable storage media, a processor, and other suitable hardware and software, is typically configured to coordinate the electronic features and settings of the optical head 170 and / or other equipment or payloads used within the operating room 10, e.g., foot pedals, hand controls, filters, video cameras, beam splitters, etc. Control of the robotic system 11 via the ECU 23 is controlled by electronic control signals (CC) 24, as described below. 11 ) to one or more actuators. Such a cabinet 22 may be constructed of lightweight, easily sanitized construction, such as painted aluminum or stainless steel, and may be used to protect the ECU 23 component hardware from the potential ingress of dust, debris, and moisture.

[0021] Referring now to Figure 2, SCARA 15 is shown in a top view and includes a plurality of revolute joints, first, second, and third revolute joints 30A (J1), 30B (J2), and 30C (J3), respectively. The first, second, and third revolute joints 30A, 30B, and 30C, collectively referred to as revolute joints 30 for simplicity, are included in the structure of SCARA 15, along with additional fourth and fifth revolute joints 30D (J4) and 30E (J5), as shown in Figure 3. SCARA 15 also includes respective first and second links 40A (L1) and 40B (L2), coupled together by second revolute joint 30B.

[0022] 1 is attached to the distal end E1 of the second link 40B, with the optical head 170 firmly attached to the bracket 19. Each of the first link 40A and second link 40B is fabricated using cold isostatic pressing and may be made of a powder metallurgy alloy-like material, possibly containing aluminum and beryllium, such as, but not limited to, commercially available AlBeMet® AM162. Such a material is advantageous because of its high elastic modulus-to-density ratio, approximately four times that of steel, aluminum, or titanium.

[0023] In the serial architecture shown in FIG. 2, a first link 40A of the SCARA 15 is connected to the base 13 via a first revolute joint 30A. A second link 40B is connected to the first link 40A via a second revolute joint 30B, as described above. Additionally, the second link 40B includes or terminates at the distal end E1 (see FIG. 1 ) described above, which in turn is connected to a third revolute joint 30C as shown. Unlike the first link 40A, the second link 40B of FIG. 2 is constructed as a 1-DOF, four-bar mechanism 400, an exemplary implementation of which will now be described with reference to FIG. 3.

[0024] Referring briefly to FIG. 3, a four-bar mechanism 400 contemplated herein for use as the second link 40B includes parallel horizontal links 40B-1 and 40B-2 coupled to parallel vertical links 40B-3 and 40B-4. In the orientation shown in FIG. 3, the horizontal links 40B-1 and 40B-2 are "horizontal" in the sense that they are disposed parallel to the floor 50 and parallel to each other. Similarly, the two vertical links 40B-3 and 40B-4 are "vertical" in the sense that they are disposed perpendicular to the floor 50, i.e., perpendicular to the horizontal links 40B-1 and 40B, and are also parallel to each other. The four constituent links 40A, 40B, 40C, and 40D of the four-bar mechanism 400 are joined together with four revolute joints 30, in this case, first and second revolute joints 30A and 30B, respectively, and two additional revolute joints, i.e., fourth and fifth revolute joints 30D and 30E. The revolute joints 30A, 30B, 30C, and 30D of the illustrated four-bar mechanism 400, i.e., joints J1, J2, J3, and J4, are constructed as understood in the art so that horizontal links 40B-1 and 40B-2 move together in parallel planes.

[0025] The up and down movement of the four-bar mechanism 400 is provided herein, in one or more embodiments, by a linear actuator 44, e.g., a non-reverse drive vertical harmonic drive unit. The linear actuator 44 may be coupled to the third rotary joints 30C and 30D (FIG. 3) such that the translational force imparted by the linear actuator 44, as indicated by the double-headed arrow LL, is used to help position the four-bar mechanism 400 and any connected load, such as the microscope 17 of FIG. 1. Advantages of using a linear actuator 44 include minimal backlash and reversibility, the latter being particularly beneficial in power failure conditions, during which the structure of the unpowered SCARA 15 must support the full weight of the microscope 17. The linear actuator 44 is configured to control the vertical movement of the microscope 17 when power is available, and such vertical movement relative to the surgeon's normal reference frame is indicated by the double-headed arrow VV. In the possible configuration, none of the revolute joints 30A, 30B, 30C, and 30D of the four-bar mechanism 400 function in the anti-gravity mode.

[0026] Referring again to FIG. 2 , an optional gas spring counterbalance 33 may be operatively connected to the second link 40B to compensate for gravity. Air or other gas spring counterbalances, also referred to in the art as pneumatic counterbalance systems, are mechanical devices that utilize compressed gas to counterbalance a load—in this case, the weight of the optical head 170 of the microscope 17 shown in FIG. 1 . To this end, the gas spring counterbalance 33 provides a counterbalance force to help hold the optical head 170 in a stationary position. In a possible configuration, the gas spring counterbalance 33 may include a pneumatic cylinder or gas spring 37 connected to the second link 40B and a compressed gas source 39. Thus, the gas spring counterbalance 33 may be used to support the position-controlled SCARA 15 by providing a smooth, consistent counterbalance force at a level sufficient to counterbalance the combined weight of the SCARA 15 and the optical head 170. Such counterbalance force is available throughout the SCARA 15's full range of motion.

[0027] According to one aspect of the present disclosure, the first three revolute joints 30A, 30B, and 30C, i.e., joints J1, J2, and J3, may be individually powered by corresponding harmonic drive units 55A, 55B, and 55C (labeled D1, D2, and D3, respectively). Each revolute joint 30A, 30B, and 30C rotates about a corresponding joint axis A1, A2, or A3. That is, harmonic drive units 55A, 55B, and 55C are configured to power each one of revolute joints 30A, 30B, and 30C in an optional actuated / actively driven manner, as opposed to the passive structure of SCARA 15. For example, revolute joints 30A, 30B, and 30C may be driven by one or more harmonic drive rotary actuators for high force and improved positional accuracy. In certain embodiments, one or more of the harmonic drive actuators may be configured as slotless brushless DC (BLDC) rotary motors, which in this or other embodiments may include neodymium iron boron (NdFeB) magnets or other suitable rare earth magnets or non-rare earth alternatives. As used herein, a harmonic drive unit may include a miniature precision mechanical reducer providing a high gear reduction ratio, for example, at least about 50:1 to 100:1 or more, in possible implementations of the SCARA 15.

[0028] By using flexible toothed components and integrated motor and bearing configurations, typical harmonic drive units can achieve smooth and precise motion control. Because such control occurs with minimal backlash, harmonic drive units 55A, 55B, and 55C shown in FIG. 2 are particularly well-suited for this surgical application. However, those skilled in the art will recognize that other actuators offering similar performance advantages may be used in alternative configurations of SCARA 15, and thus SCARA 15 of FIG. 2 is not limited to use with harmonic drive units 55A, 55B, and 55C for its actuation. For example, revolute joints 30A, 30B, and / or 30C could be powered using, for example, planetary, cycloidal, worm, or spur gearboxes, belt drive systems, rack-and-pinion arrangements, etc., without departing from the intended scope of this disclosure.

[0029] 4, the optical head 170 of the microscope 17 shown in FIG. 1 may be connected to or may integrally include a sensor 40, for example, an incremental or absolute encoder for position sensing. Measurements from such a sensor 40 or multiple such sensors 40 may be used by the ECU 23 of FIG. 1 to control the operation of either the harmonic drive unit 55 of FIG. 2 and / or the linear actuator 44 of FIG. 3. This is accomplished by the electronic control signals (CC) shown in FIG. 1. 11 ) is generated using the optical head 170. The optical head 170 is driven by a separate harmonic drive unit 155 along its pitch axis A P and is free to move about the pitch axis A P 1 is placed parallel to the plane of floor 50 as described above, and base 13 of FIG. 1 rests on floor 50 and is optionally fixedly attached to floor 50. Rotation of optical head 170 is driven by a separate harmonic drive unit 255 about rotation axis A R , another harmonic drive unit 255 being itself located on axis A3 of revolute joint 30C shown in FIG.

[0030] The pitch (PP) and rotation (RR) of the optical head 170 can be selectively locked, for example, using stops, brakes, and / or motorized harmonic drives (not shown). The pitch and rotation of the optical head 170 are adjusted as needed to achieve a desired imaging angle or orientation, and pitch, as used herein, refers to the rotation of the optical head 170 relative to the pitch axis A. P Pitch and rotation refer to angular movement of the optical head 170 about its optical axis (not shown). In contrast, rotation, as used herein, refers to angular movement of the optical head 170 about its optical axis (not shown), which axis coincides with the rotational moment of the optical head 170. Those skilled in the art will understand that mechanical adjustments can be made by the surgeon as needed to set the desired pitch and rotation angles.

[0031] The robotic system 11 of FIG. 1 , with its SCARA 15—i.e., the SCARA 15 and the four-bar mechanism 400—together provide 4-DOF, thus enabling improved 4-DOF serial implementation with kinematics specific to cataract and VR surgical applications. The SCARA 15 contemplated herein allows for large-amplitude, precise horizontal (xy) motion parallel to the floor 50. Using the four-bar mechanism 400 shown in FIG. 3 , vertical (z) motion is permitted while maintaining vertical orientation of all three axes of the SCARA 15 that define horizontal and vertical motion. Among the many attendant advantages of the present teachings, the SCARA 15, when configured as described above, avoids interference between the SCARA 15 and the surgeon or patient when the display screen 20 of FIG. 1 is positioned directly in front of the surgeon.

[0032] The non-backward drivable structure eliminates falling of the SCARA 15 in the event of a power failure, and the proposed pitch axis AP of the optical head 170 shown in Figure 4 is optimal for visualization during, for example, microinvasive glaucoma surgery (MIGS) procedures, and for examination and treatment of the retinal periphery. These and other attendant advantages will be readily apparent to those skilled in the art in light of the above disclosure.

[0033] As will be appreciated by those skilled in the art, various features shown and described with reference to any one of the figures can be combined with features shown in one or more other figures to produce embodiments not explicitly shown or described. The combinations of features shown provide representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of this disclosure may be desired for particular applications or implementations.

[0034] In the following description, certain terms may be used for reference purposes only and, therefore, are not intended to be limiting. For example, terms such as "upper" and "lower" refer to directions within the referenced drawings. Terms such as "front," "rear," "forward," "rearward," "left," "right," "rear," and "side" describe the orientation and / or location of a component or portion of an element within a consistent but arbitrary frame of reference that becomes clear by reference to the text and associated drawings that describe the component or element being discussed. Furthermore, terms such as "first," "second," and "third" may be used to describe separate components. Such terms may include those specifically mentioned above, derivatives thereof, and words of similar import.

[0035] The detailed description and drawings support and explain the disclosure, the scope of which is defined only by the claims. Although some of the best modes and alternative embodiments for carrying out the claimed disclosure have been described in detail, there are various alternative designs and embodiments for carrying out the disclosure as defined in the appended claims.

[0036] Furthermore, the features of the various embodiments shown in the drawings or described herein should not necessarily be understood as independent embodiments. Rather, each of the characteristics described in one example embodiment may be combined with one or more other desirable characteristics from other embodiments, resulting in other embodiments not described in words or by reference to drawings. Accordingly, such other embodiments are encompassed within the scope of the appended claims.

Claims

1. 1. A robotic system for use with a microscope, comprising: A base and a support column; a selectively compliant articulated robotic arm (SCARA) connected to the base via the support column, a plurality of rotary joints including a first rotary joint, a second rotary joint, and a third rotary joint; a first link connected to the base via the first rotary joint; a second link connected to the first link via the second rotary joint and having a distal end connected to the third rotary joint, the second link configured as a four-bar mechanism and configured to connect to the microscope; a linear actuator connected to the second link and configured to control vertical movement of the second link, wherein none of the rotary joints of the SCARA function in an anti-gravity mode; A selective compliance articulated robotic arm (SCARA) including: A robot system comprising:

2. an electronic control unit (ECU) configured to provide electronic control signals to the linear actuator to control the vertical movement of the linear actuator; The robotic system of claim 1 further comprising:

3. 2. The robotic system of claim 1, further comprising a plurality of harmonic drive units, wherein at least one of the rotary joints of the SCARA is configured to be powered by a corresponding one of the harmonic drive units.

4. The robotic system of claim 3 , wherein at least one of the harmonic drive units is configured as a brushless DC motor.

5. the microscope; a bracket attached to the distal end of the second link, the microscope being attached to the bracket; and The robotic system of claim 1 further comprising:

6. The robot system of claim 5 , wherein the base is disposed on a floor, and the microscope has an optical head with a pitch axis disposed parallel to the floor.

7. The robotic system of claim 6 , wherein the pitch and rotation of the optical head are selectively lockable.

8. a position sensor connected to the optical head and in communication with an electronic control unit (ECU); The robotic system of claim 6 further comprising:

9. The robotic system of claim 1 , wherein the linear actuator comprises a non-back-driveable vertical harmonic drive unit.

10. a gas spring counterbalance device operatively connected to said second link; The robotic system of claim 1 further comprising:

11. The robotic system of claim 1 , wherein the first link and the second link are constructed of aluminum and beryllium.

12. 1. A Selective Compliance Articulated Robotic Arm (SCARA) for use with a microscope and base, comprising: a plurality of rotary joints including a first rotary joint, a second rotary joint, and a third rotary joint; a first link connectable to the base via the first rotary joint; a second link connected to the first link via the second rotary joint and having a distal end connected to the third rotary joint, the second link configured as a four-bar mechanism and configured to connect to the microscope; a linear actuator connected to the second link and configured to control vertical movement of the second link in response to electronic control signals from an electronic control unit (ECU), the linear actuator including a non-back-driveable vertical harmonic drive unit, and none of the rotary joints of the SCARA function in an anti-gravity mode; A selectively compliant articulated robotic arm (SCARA), including:

13. a harmonic drive unit, wherein one of the rotary joints of the SCARA is powered by the harmonic drive unit; 13. The SCARA of claim 12, further comprising:

14. 14. The SCARA of claim 13, wherein the harmonic drive unit includes a plurality of harmonic drive units, and each of the rotary joints of the SCARA is individually driven by a corresponding one of the harmonic drive units.

15. a bracket attached to the distal end of the second link, a microscope being attached to the bracket; 13. The SCARA of claim 12, further comprising:

16. 16. The SCARA of claim 15, wherein the microscope is a digital or analog ophthalmic microscope with an optical head.

17. 17. The SCARA of claim 16, wherein the base is configured to be placed on a floor, and the optical head has a pitch axis disposed parallel to the floor.

18. a position sensor connected to the optical head and in communication with the ECU; 17. The SCARA of claim 16, further comprising:

19. a gas spring counterbalance device operatively connected to said second link; 13. The SCARA of claim 12, further comprising:

20. 1. A robotic system comprising: an ophthalmic microscope, a bracket attached to the microscope; A base and a support column; an electronic control unit (ECU) configured to output electronic control signals; a selectively compliant articulated robotic arm (SCARA) connected to the base via the support column, a plurality of rotary joints powered by one or more harmonic drive units, the plurality of rotary joints including a first rotary joint, a second rotary joint, and a third rotary joint; a first link connected to the base via the first rotary joint; a second link configured as a four-bar mechanism, the second link being connected to the first link via the second rotary joint and having a distal end connected to the third rotary joint, the second link being connectable to the microscope via the bracket; a gas spring counterbalance device operatively connected to the second link; a linear actuator connected to the second link and configured to control vertical movement of the second link in response to the electronic control signal, wherein none of the rotary joints of the SCARA function in an anti-gravity mode; A selective compliance articulated robotic arm (SCARA) including: A robot system comprising:

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