ARASH:ASiST

ARASH:ASiST” is the name of the Haptic system for eye surgery training. That is an abbreviation of “Aras Haptics: a system for eye surgery training”. “ARASH” also refers to Arash the Archer, a heroic archer-figure of Iranian mythology. ARASH:ASiST includes two similar devices specially designed to operate as a training system for minimally eye surgery. These similar devices operate as a dual haptic-surgery robot. In minimally invasive vitreoretinal eye surgery, unlike a general surgery, it requires 3 degrees of freedom to cover a spherical workspace. ARASH:ASiST operates as a mechanically remote center of motion (RCM) mechanism to provide the required spherical workspace for vitrectomy eye surgery and provide a safe environment for robotic surgery process. In minimally-invasive eye surgery, the surgical instrument enters the patient’s eye through a small incision and surgery process take place around this pivot point.

ARASH:ASiST takes advantage of parallelogram structure to produce a remote center of motion mechanism designed especially for minimally invasive vitreoretinal eye surgery. Designing a surgery robot requires a lot of attention to many aspects of designing procedure. Especially in vireo-retinal robotic eye surgery due to the augmented sensitivity in this vital tissue, challenges in the design procedure become manifold. ARASH:ASiST is a dual surgery-haptic device specially designed for vitrectomy eye surgery training. Integration of a surgery robot and a haptic device in one platform increase designing challenges significantly. A brief description of the parts of these challenges provided here.

For providing the force feedback that would be felt in actual operations it is desirable to carefully control the apparent inertia of the ARASH-Asist robot. For this aim, there was a challenging design problem to reduce the moving part’s inertia as much as possible. By using light material and providing stress analysis besides organizing constant components such as force sensor and insertion actuator in an ideal configuration, the overall inertia of the robot has been reduced to the lowest amount. Inertia compensation can be used to relieve forces felt by the user during free-space motion, and it is necessary to compensate the inertia of the robot to provide an approximate real sense of traditional eye surgery which operates in a sensitive condition with forces lower than merely one newton. ARASH-Asist benefits of concentrated mass inertia compensation method to enhance the sense of touch in a teleoperation eye surgery training procedure.

Kinematics

Kinematics of the ARASH-Asist considered along with the fabrication limitations such as links intersection, troublesome inertia, and mechanical behavior of the system to cover the required workspace of the vitrectomy eye surgery. ARASH-Asist provides over 90 degrees in both roll and pitch directions and it provides 40mm in the insertion direction. In ARASH-Asist, smooth and accurate motions in roll and pitch directions provided using capstan-drive back-drivable transmission mechanism which is a zero-backlash cable driven transmission mechanism, and insertion direction actuated using a miniature cable driven mechanism. Due to the sensitivity of the eye surgery procedure, all of the components designed carefully to provide smooth and zero-backlash movements.
Along with the mechanical design of the ARASH-Asist; robot ergonomy considered during the designing procedure to prepare a condition which feels natural and does not interfere with robot operation.

Software

The software of robot consists of 5 modules:

  • Connection module

    Connection module has communication task with Maxon drives. With this module, we can command the position, velocity, or torque to the drives and get the motor’s current as a feedback. This module is provided in a dll file made by maxon motor company.

  • Control module

    In Control module, control and training strategy is implemented.

  • Communication module

    Communication module for connecting between two control boards is one of the most important parts of the robot’s software. Both TCP and UDP protocols are applicable but because the network is simple and short and the fact that the speed of communication is more important than the correctness of every single packet we prefer to use UDP protocol. In the UDP protocol, one of the control boards is server and the other one is client. The following figure shows the communication status.

  • Interface module

    Interface module allows the user to adjust the working mode of the training system and observe the progress of training.

  • Data base module

    Data base module, we store all the information we need to analyze the status of the progress of training.

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