Patent Application
20100275718
Conventional devices which are used to perform very complex and/or physically demanding surgical procedures like neurosurgery, spine surgery, ear surgery, head and neck surgery, hand surgery and minimally invasive surgical procedures have a number of drawbacks as it relates to the dexterity of the surgeon. For example, the surgeon can easily become fatigued by the need to manually support the surgical device during its use. Additionally, the surgeon may have to orient his hands in an awkward position in order to operate the device. Furthermore, conventional devices used in such surgical procedures can produce angular magnification of errors. As a result, a surgeon has considerably less dexterity and precision when performing an operation with such surgical devices than when performing an operation by traditional techniques in which the surgeon grasps a tool directly.
Accordingly, there is an increasing interest in the use of powered manipulators, such as robotic and master-slave manipulators for supporting and manipulating surgical tools during medical procedures. Such manipulators can provide a number of advantages to both patients and medical practitioners. In particular, a master/slave controlled manipulator can enhance the dexterity of the surgeon/operator so as to allow the surgeon to manipulate a medical tool with greater dexterity than he could if he was actually holding the tool in his hands. A manipulator can also reduce the fatigue experienced by a surgeon, since it eliminates the need for the surgeon to physically support the medical tool or device during its use. Additionally, the surgeon can let go of the manipulator and perform other tasks without the medical tool undergoing movement, which increases the efficiency of the surgeon and can reduce the number of individuals that are necessary to perform a particular procedure. Thus, manipulators can allow medical procedures to be performed much more rapidly, resulting in less stress on the patient.
However, many manipulators, including those having six degrees of freedom, have some drawbacks in that, in certain orientations, the amount of torque that the manipulator can apply is limited. This restricts the work that can be done by the manipulator in such orientations. Moreover, some manipulators have singularity points within their operational envelopes. At these singularity points, two or more manipulator joints become redundant and fewer degrees of the freedom can be exercised. This can cause a manipulator mechanism to become locked or impeded such that it can no longer move freely.
The invention provides a manipulator, such as for use in medical procedures. The manipulator includes a body and a first actuator system connected to the body at a first attachment point and is capable of moving the first attachment point with at least three degrees of freedom. A second actuator system is connected to the body at a second attachment point and is capable of moving the second attachment point with at least three degrees of freedom. A third actuator system is connected to the body at a third attachment point and is capable of moving the third attachment point with at least one degree of freedom.
Referring now more particularly to
While the present invention is described in connection with performing complex medical procedures, the manipulator of the present invention is not limited to such applications. Rather, the manipulator of the present invention can be used in any application involving dexterous tasks. For example, it can be used in applications involving the remote manipulation of hazardous materials. It can also be used in complex assembly or repair operations to perform autonomous, but repetitive, tasks normally done by humans.
In order to provide dexterity enhancement for an operator/surgeon in performing surgical and certain interventional radiology procedures, the manipulator 10 can be used as a slave robot in a master-slave robotic system. The manipulator 10 can also be used as a master robot in such a system. In a master-slave robotic system, a surgeon/operator provides position input signals to the “slave” manipulator via a master or haptic interface which operates through a controller or control console. Specifically, with the manipulator 10 of the present invention serving as the slave robot, the surgeon indicates the desired movement of the tool held by the manipulator 10 through the use of an input device on the haptic interface such as a six degree of freedom tool handle with or without force feedback, joystick, foot pedal or the like. The haptic interface relays these signals to the controller, which, in turn, applies various desired predetermined adjustments to the signals prior to relaying them to the slave manipulator. Any haptic interface having an six or more degrees of freedom (DOF) can be used to control the manipulator 10 via the controller. Examples of haptic interfaces or masters which can be used with the present invention include the Freedom 6S available from MPB Technologies of Montreal, Canada, and other haptic interfaces commercially available from Sensable Technology of Cambridge, Mass. and MicroDexterity Systems of Albuquerque, N. Mex.
Based on the signals provided by the controller, the manipulator 10 executes the desired movement or operation of the tool. Thus, any desired dexterity enhancement can be achieved by setting up the controller to perform the appropriate adjustments to the signals sent from the haptic interface. For example, this can be accomplished by providing the controller with software which performs a desired dexterity enhancement algorithm. Software dexterity enhancement algorithms can include position scaling (typically downscaling), force scaling (up-scaling for bone and cartilage, downscaling for soft tissue), tremor filtering, gravity compensation, programmable position boundaries, motion compensation for tissue that is moving, velocity limits (e.g., preventing rapid movement into brain, nerve or spinal cord tissue after drilling through bone), and, as discussed in greater detail below, image referencing. These and other examples of possible algorithms are well known in the field of robotics and described in detail in published literature. The ZMP SynqNet® Series Motion Controllers which employ the SynqNet system and are available from Motion Engineering of Santa Barbara, Calif. are one example of a suitable controller for use with the present invention (see www.synqnet.org and www.motioneng.com). Another example of a suitable controller is the Turbo PMAC available from Delta Tau Data Systems of Northridge, Calif.
To effect movement of the support member 12 in space, the manipulator 10 includes first and second separate, independent three degree of freedom actuator systems 16, 18 each of which connects to the support member 12 at a respective attachment point. The manipulator further includes a separate third actuator system 19 that is at least one degree of freedom and attaches to the support member 12 at a separate third attachment point that is coplanar with the attachment points of the first and second actuator systems. The first, second and third actuator systems 16, 18, 19 are each supported on a solid mount. The first and second actuator systems 16, 18 can be any type of three degree of freedom actuator system. Likewise, the third actuator system 19 can be any type of actuator system that provides the desired degrees of freedom, although an actuator system with three or more degrees of freedom actuator is presently preferred. The use of a three degree of freedom actuator provides the manipulator with a total of nine degrees of freedom. One example of such a manipulator is shown in
As will be appreciated by those skilled in the art, six degrees of freedom are all that is required to define the position of the support member in space. Thus, the seventh, eighth and ninth degrees of freedom provided by the preferred embodiment of the invention are redundant degrees of freedom. The redundant degrees of freedom provide for good torque delivery in a wider variety of orientations as compared to a manipulator having just six degrees of freedom (i.e., no redundant degrees of freedom) and expands the operational envelope beyond what many six degree of freedom manipulators can achieve. In particular, the range of motion of all hybrid serial/parallel mechanisms is defined by a series of singularity points where the manipulator becomes locked and can no longer move freely. For example, these singularity points can happen when the manipulator is at full extension with the mechanical elements of the manipulator binding against one another in such a way that the manipulator cannot provide enough force or torque to move itself and whatever tool is being manipulated. The redundant degrees of freedom help solve this problem.
Various embodiments of seven degree of freedom manipulator systems in which the seventh degree of freedom is provided by a third actuator system that is integrated with the moving body are disclosed in commonly owned U.S. patent application Ser. No. 11/710,023 filed Feb. 23, 2007, the disclosure of which is incorporated herein by reference. As compared to those systems, the arrangement of the present invention provides the advantage that full six degree of freedom movement can be delivered directly at the moving body rather than through the use of the third actuator system attached to the moving body. In particular, as noted above, the arrangement of the present invention provides a third actuator system 19 that attaches to the support member 12 at a separate third attachment point rather than being integrated into the support member 12. This means that the arrangement of the present invention moves the heavy motors and reduction mechanisms associated with the third actuator system to a point away from the moving body. In most cases, this will advantageously reduce the inertial forces associated with the manipulator.
Conventional platform manipulators typically use six actuators each of which connects to the platform at a different attachment point. The actuators can have various configurations. Platform manipulators can experience problems when the platform is moved into a position in which the actuator link and the attachment point on the platform are, or are nearly, coplanar. In such a position, the actuator becomes useless and the manipulator can lock up. This is because the actuator can only push or rotate, but not both. When you replace the single degree of freedom actuators with three three degree of freedom actuators as in the preferred embodiment of the invention, you have the ability to generate any force vector in a three degree of freedom working space. For example, the three degree of freedom manipulators can be operated together to produce translation or rotation of the support member. Even if the attachment points and the actuator become coplanar, the actuator can produce a force vector that will still control the position of the attachment point. As a result, the manipulator of the present invention is much more dexterous and has fewer singularity points within the workspace than conventional six degree of freedom platform manipulators. The singularity points with the preferred nine degree of freedom embodiment are mostly defined by the points where actuator links are touching or where joints/links have reached a limit of their movement. Additionally, the extra degrees of freedom allow for a reduction or modulation of the motor power associated with the manipulator leading to better control of power consumption and heat.
In the
In the embodiment illustrated in
For sensing the positions of the various rotary joints 26, 27, 29 and, in turn, the support member 12 and/or tool mount, all or some of the rotary joints can be equipped with position sensors. Each of the drive systems of the manipulator can be in communication with the controller and the position sensors can provide position information in a feedback loop to the controller. It will be appreciated that any number of different conventional position sensors can be used such as, for example, optical encoders. Moreover, the various drive systems can also be equipped with force sensors for sensing the forces or torques applied by the actuators so as to enable a determination of the forces and torques applied to the support member and/or the tool mount. This information can again be provided in a feedback control loop to the controller, for example to allow force feedback to the input device of a haptic interface. Of course, any known method for measuring forces and/or torques can be used, including, for example, foil type or semiconductor strain gauges or load cells.
As noted above, the first, second and third actuator systems 16, 18 can be any type of three or more degree of freedom actuator systems. For example, an alternative embodiment in which three rotary joint/actuators 130, 131, 132 are employed in the first, second and third actuator systems 116, 118, 119 as opposed to linear joints/actuators is shown in
A further embodiment that employs three degree of freedom parallel, as opposed to serial, actuators as the first, second and third actuator systems is shown in
As shown in
In the embodiment of
As shown in the embodiment of
While the nine degree of freedom arrangements of
A manipulator with a total of seven degrees of freedom is shown in
In view of the foregoing, it will be appreciated that the present invention provides a manipulator that provides up to nine or more degrees of freedom. The redundant degrees of freedom provide improved performance by improving torque delivery in certain orientations and by helping to eliminate certain singularity points. Manipulators having first, second and third actuator systems with particular configurations are shown in the drawings and described herein. Of course, other types of three degree of freedom actuator systems could also be used for the first, second and third actuator systems. For example, one or more of the actuator systems could be based on a so-called r-theta mechanism, which is a two degree of freedom radial coordinate engine. A further actuator can then be connected to each r-theta mechanism which is able to independently move the corresponding r-theta mechanism out of its respective rotational plane. The result is that the actuator systems comprise independent three degree of freedom actuator systems. Other arrangements are also possible.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
