User experience and capability improvements for portable arm and scanning measurements include: Guided Portable Execution — PC-DMIS will now guide the user through the measurement process, highlighting the measurement points with red dots, turning them green when the point is captured.
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The CMM may be attached to a frame of robotic surgical system to ensure that the CMM and the robotic surgical system have the same coordinate reference system. However, the CMM and robotic surgical system may also be separated and the use of a standard or other non-portable CMM may be used which can be aligned with the coordinate system of robotic surgical system Two exemplary calibration methods are provided in FIGS.
Robotic surgical system includes a support to which an articulated arm is coupled. The articulated arm has several joints having position encoders therein. In one embodiment, the robotic arm has six joints with six corresponding position encoders to define six axes of movement. In the illustrated representation, articulated arm includes three movable links , , and Link is movably coupled to support through a first joint First joint is one of a rotational joint, whereby link is rotatable relative to support ; a translational joint, whereby link is translatable relative to support ; or a combination of rotational joint and a translational joint.
The movement of link relative to support is controlled by a motor An exemplary motor is an electric motor. Link is movably coupled to link through a second joint Second joint is one of a rotational joint, whereby link is rotatable relative to link ; a translational joint, whereby link is translatable relative to link ; or a combination of rotational joint and a translational joint.
The movement of link relative to link is controlled by a motor Link is movably coupled to link through a third joint Third joint is one of a rotational joint, whereby link is rotatable relative to link ; a translational joint, whereby link is translatable relative to link ; or a combination of rotational joint and a translational joint. Motors , , and are controlled by a robot control system Robot control system , in one embodiment, includes a computing device executing software to control the operation of robotic surgical system including the movement of support An exemplary robot control system is control unit of robotic surgical system The movement of support may locate an end of support at a point in a working volume Working volume is shown as a cube, but may take on any shape based on the kinematics of robotic surgical system A tool may be coupled to end Robot control system by knowing the offset of a tool portion such as sphere of tool may locate the tool portion of tool in the robot coordinate system In addition to a location in working volume , robot control system may control an orientation of link , such that not only is the location of end or the tool portion of tool controlled, but also the direction link takes in placing end or the tool portion of tool at that location.
Robot control system records the location end or the tool portion of tool and the direction of link in a robot coordinate system Robot coordinate system is shown as a Cartesian coordinate system, but may be any type of coordinate system. Of course, robot control system may also keep track of the location of joint , joint , and joint along with the direction of link and link Also represented in FIG. CMM includes an articulated arm and a CMM control system which records the position of an end effector of articulated arm CMM coordinate system is shown as a Cartesian coordinate system, but may be any type of coordinate system.
The robotic surgical system may move the joints , , and according to a desired location of the tool portion of tool using information acquired during a landmarking procedure. To ensure the robotic surgical system can accurately and repeatably identify the location of the tool portion of tool , the articulated arm is subjected to a calibration routine to verify that the desired location of the tool portion of tool is accurate. In the representation illustrated in FIG.
The movement from A, B, C, and to D is a trajectory of the tool portion of tool The reference positions, illustratively A, B, C, D, represent a theoretical point cloud in the robot coordinate system in which the articulated arm is intended to position itself. At each reference position, the location of the tool portion of tool is characterized using the CMM system The measurements taken by the CMM at each reference position represent an actual point cloud in the CMM coordinate system Point cloud is a measurement of the actual position of the tool portion of tool and is used to characterize the error in point cloud This error may be used to better calibrate robotic surgical system to reduce the error in future movements of articulated arm This error may be determined by a comparison of point cloud and point cloud wherein one or more of a translation of robot coordinate system along one or more of its axes is identified, a rotation of robot coordinate system is identified, a scale difference is identified, or a combination thereof.
Further, an iterative mathematical algorithm which uses D-H Denavit-Hartenberg parameters, as are well-known in the field of robotics, to optimize the kinematics model of the robotic surgical system D-H parameters may be used to define the coordinate space around a robotic arm having multiple joints with multiple degrees of freedom and thereafter used to calibrate the joint offsets of the joints of the robotic arm.
In one embodiment, point cloud is communicated to robot control system which characterizes the error in point cloud In order to evaluate the accuracy of robotic surgical system , point cloud and point cloud must be resolved to share the same coordinate system. In one example, this shared coordinate system is coordinate system In one embodiment, point cloud is fit to point cloud to determine the error in the position of the tool portion of tool through a closed form method.
One closed form method of determining the error in the position of the tool portion of tool is disclosed in Berthold K. In alternative embodiment, other methods may be used including iterative least squares methods. Once point cloud and point cloud have been resolved, given knowledge of the base kinematic model generally referred to as D-H Parameters , the robot kinematic model may be optimized to minimize for example, the positional inaccuracy.
The new kinematic model updated parameters may then be used to correct the robot systems joint values to effectively further correct the accuracy of the robot.
Once these steps have been taken, the robot system may again be tested through the same trajectory with the external measuring device. In one embodiment, forty points as opposed to the illustrated 4 points are provided as trajectory points. Appendix A provided in U. In one embodiment, calibration tool is used as tool and sphere is the tool portion of calibrating tool Robot control system attempts to position calibrating tool such that a center of sphere is positioned at the respective points A, B, C, and D.
When CMM system is used to determine the actual location of center , end effector digitizes multiple positions on the exterior of sphere A sphere is then fit to digitized points to produce a determined point for center The diameter of sphere is a known value. As such, by digitizing sphere and determining the center and thus also the diameter with CMM system the accuracy of CMM system may also be checked.
For instance, if it is known that sphere has a diameter of 0. In this situation, CMM system should be recalibrated. In the case wherein the direction of link is also important, a direction of link may be determined by CMM system with calibrating tool being used as tool CMM system is used to digitize each of spheres separately to determine centers The three centers define a plane which is at a known orientation relative to end face of calibrating tool , illustratively parallel.
As such, by knowing the orientation of plane a direction of link is readily determinable. In one embodiment, calibrating tool is used as tool and sphere is the tool portion of calibrating tool However, by having sphere a greater distance away from base portion than sphere is from base portion angular errors in the positioning of link are magnified and hence easier to detect.
In one embodiment, instead of digitizing a calibration tool to determine the location of the robotic system , a center position of end face is digitized to determine the location of robotic system In one example, end face includes a divot or other feature that is digitized to determine a center position of end face Referring to FIGS. In FIG. Also represented is a calibration template is shown.
Calibration template includes a plurality of calibration spots see FIG. In the illustrated embodiment, plurality of calibration spots are generally spherical divots which are sized to generally match a diameter of sphere of calibrating tool
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