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Technology

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iSiOS
uses the native precision of the laser


The patented
functional principle of iSiOS
is based on scanning some precisely straight laser beam with the robot. When the robot hand is moved along the laser beam, smallest deviations from the straight line are detected easily. Measurements of these deviations yield a precise model of the robot by elaborate mathematical algorithms. The identified robot model contains all entities which influence the position of the robot hand. Deformations of the robot arm, zero offsets of the joints or gravity-induced displacements of the hand are compensated completely and sustainably in the whole workspace.
iSiOS uses this principle usually in reverse set-up: the compact, light-weight laser is carried by the robot and stationary sensors are placed near the workcell boundary.

Accuracy

Small errors of the robot are mapped in full size onto the sensor over the whole range of the laser beam. This is the foundation of the conceptually high sensitivity and precision of the system, which could easily be increased further if needed - e.g. for the calibration of micro-mechanisms. With two or three sensors placed and distributed properly on the boundaries of the workcell, iSiOS calibration provides maximum robot positioning accuracy throughout the complete workspace.

The fundamentally new approach yields decisive technical advantages which were reserved to costly laser trackers before

  • The large errors caused by gravitation-induced elasticities and deflections are identified and compensated precisely. This feature is a key component of  the superior absolute robot accuracy provided by the iSiOS calibration system.
  • The appropriately sized, patented iSiOS carbon fiber etalon with two cost-efficient sensors yields sufficient error dampening to determine absolute robot lengths precisely in contrast to measurements within a restricted area or at a single spot or at some single calibration-object which may be used by other approaches.
  • During set-up, iSiOS does not require the use of an additional laser tracker anymore, which was needed up to now to measure the exact poses of obligatory calibration-objects w.r.t the robot whenever demanding precision goals had to be met.
  • iSiOS is highly sensitive also to orientational errors. When the laser is mounted on the robot hand or tool, the laser beam functions as an immaterial lever, which amplifies orientation errors proportional to distance, yielding maximum orientational accuracy after calibration.
In all its accuracy statements, Isios always takes the user defined tooltip (TCP) into account. As an example, for certain types of universal, industrial 6-joint robots, absolute positioning errors at the tip of a tool of 200 mm length can be kept below 0,15 mm in the whole workspace including arbitrary changes in the joint-configuration (i.e. shoulder left or right, elbow up or down, handflip); the average error ranges around a minimum of 0,06 mm. Counter-examination with high precision measurement devices (laser tracker) yields highly similar calibration results.

Depending on type, the average overall accuracy of industrial robots with workspace radius below 3 m and payload below 500 kg can be raised up to the exceptionally high level of 0,2 mm and better. The overall accuracy is the effective accuracy at the workpiece when the hand pose is specified relative to the workpiece only. In this case, the absolute pose of the hand with respect to the world is unknown beforehand but is automatically identifed by the iSiOS system with the calibrated robot.


Cost-efficiency

The outstanding scalable sensitvity and high resolution of the system is founded in the technological concept of the system, not in costly measurement equipment.


Control of the calibrated robot

Once the parameters of the robot model are identified exactly, the robot can be controlled exactly. This only requires appropriate calculations
before each precision move of the robot - the so called inverse transformation - but no additional measurements during runtime. Calculation can be executed by the robot control unit. To obtain superior robot accuracies the extremely fast iSiOS realtime-precision-control module is used which may be executed on the robot controller or independently on a remote computer.


Compare iSiOS

  • iSiOS does not need elaborate, sensitive optics or precision measurement devices. The scalable sensitivity of the system and its particular technological concept guarantee maximum robot accuracy within the complete workspace - not only for typical articulated-joint robots but also for cartesian robots, SCARA-robots and special purpose gantry mechanisms with combinations of rotary and prismatic (linear) joints.
  • All compact components of iSiOS inline calibration systems remain installed in the workcell and are readily available when needed. Only the stationary installation of all components enables features like
    • instant, synchronous error-diagnosis of all robots of a production line within a matter of minutes,
    • permanent monitoring of all production devices including mechanisms like rotary tables,
    • automatic recalibration and restoration of maximum accuracy after minor collisions or exchange of robots within approx. 5 minutes, or
    • compensation of wear and tear or temperature effects concurrent with production.
  • Robustness and compactness as well as contactfree, seamless integration and function in rough obstructed environments and under low visibility conditions are decisive advantages in demanding industrial applications.
  • The system redeems a large part of its cost already during set-up and initial calibration of the original production line or workcell, resp. Teach-In costs become obsolete. iSiOS is laid out and priced for fast amortisation of stationary installations in all accuracy-critical cells of a production line.

Compare accuracy, advantages and cost

Are you planning benchmark tests? Isios appreciates to support a critical evaluation of iSiOS features and resulting robot accuracy as well as comparative tests with other calibration principles.


           
           
    DerThing Medienpool Isios GmbH