Project Description

  1. Home
  2. HTIC Project

End Effector offset correction in 5-DoF CNC based surgical robot

📍 HTIC, Reseach Park IITM


  • OBJECTIVE: Minimizing end-effector offsets in ‘Maxio - 5 DoF spinal surgical robot’ during arm rotations.
  • OUTCOME: Zero Link offsets for rotation along any axis reducing the operating time and complexity.
  • DOMAIN: Robotics R&D, Reverse Engineering, CAD, motors, Electronics.

    • fig 1. IR depth tracker and the operating needle

    During my internship at Healthcare Technology and Incubation Centre in 2018, I worked on surgical robot Maxio by Perfint Healthcare, prototyping for a new design such that we retain zero offset at the end effector needle for any rotational movement at the joints.
    The robot had 5 degrees of freedom with translation along X,Y,Z and rotational freedom along Y,Z.


    fig 2. Maxio by Perfint Healthcare


    fig 3. Reverse Engineering protocol

    During the surgery planning for needle insertion we acquire the orientation and coordinates of the end effector w.r.t. the patient and the CT scans using CAD. The robot manipulation during a surgery involved two steps:
    1. Translation w.r.t. Robot coordinate frame to reach the target coordinates in the medical
    2. Rotations at the End-effector to achieve the target orientation of the needle insertion
    During the Rotational movements, the End-effector faces offset from the actual target position which need to be counter acted by additional translations. This adds extra time in planning, manipulations and errors in the whole process of the surgery. To solve this problem, reducing the errors and complexity of the procedure, we came up with a new design for the links of the manipulator. In the whole procedute metal balls awere used to track the position of the needle using a IR depth camera with accuracy of 0.1mm.


    fig 4. Prototype view 1


    fig 5. Prototype view 2
    I redesigned the links if the manipulator such that every rotation around the rotational joints are causes no offset to the end of the needle meaning every rotation occurs with the needle target as the origin. During the Rotational movements, the End-effector faces offset from the actual target position which need to be counter acted by additional translations. This adds extra time in planning, manipulations and errors in the whole process of the surgery.


    fig 6. Diagram for the implemented design

    During the Reserves engineering and configuring of the electronics the following were taken care of:
    1. Micro precision stepper motors and controls using Shield V3 CNC motor drivers.
    2. Limit switches and safety protocols for the surgery.
    3. IoT communication interfaces on RS438-USB.