Calibration and Open-Loop Control of Sunram 7: An MR Safe Robotic System for Breast Biopsy

Finished: 2022-07-25

BSc assignment

Sunram 7 is the latest prototype of robotic systems for breast biopsy. It has five degrees of freedom which are powered by 3D printed pneumatic stepper motors, making it safe for use within the MRI scanner. The envisaged workflow is that it inserts a biopsy needle and collect sample tissue from the suspicious lesion which can be examined later for malignancy.

The base and end-effector of Sunram 7 are (or can be) equipped with MRI-visible markers, retroreflective markers (for IR-based stereo vision), printed QR (or AR) codes for single-lens tracking, divots for probing needles, custom mounts for other trackers (e.g. NDI Aurora electromagnetic tracking system), dummy targets and so on. It is up to you to choose a suitable set of markers/trackers for your research.

In this BSc assignment the goal is to develop an open-loop controller with QR-based automatic calibration routine, and evaluate the needle tip placement accuracy.

The robot itself and 12-fold pneumatic valve manifold are given at the start of the project.

Some relevant questions associated with this system are:

- How are the valves and stepper motors controlled? (microcontroller (Arduino, Raspberry Pi?), transistors, quadrature waveforms, count steps, ...)
- How is the home position defined? (use forward and/or inverse kinematics)
- How can QR codes assist in automatic calibration? (OpenCV, ...)
- How can the needle placement accuracy be quantified?