Electromagnetic Calibration Test Fixture

Overview

Philips Ultrasound requested an improved design for their current transducer calibration test fixture. This fixture is used to calibrate transducers which use electromagnetic tracking. The new design must be modular and remove the need for the operator to measure each position manually. The pandemic had minimal effect on progress for the project. The team was able to transition to online communication using Skype and email. Philips was able to maintain access to their facility which allowed for minimal delays in prototyping and testing.

Objectives

Our objective was to design a new test fixture for the calibration of ultrasound transducers that consistently and precisely moves to five pre-determined positions, is simple to operate, is easy to assemble, and is more durable than the current design.

Approach

– The team met with Philips on site for a demonstration of the current calibration fixture. Questions were asked to clarify operational procedures, customer needs, and design change liberties.

– Philips requested the new design be either durable, or cheap and easy to replace. They offered to 3D print any prototypes with their FDM printer.

– Each team member generated new ideas or modifications for improvement to the current design for a selection process (covered in the final report along with relevant patents).

– CAD models were created using SolidWorks for the top two designs.

– Three prototype iterations were printed, and the final model was tested on the factory floor for comparison to the current fixture.

– The model was fully assembled next to the current fixture and both were set to each position for comparison. The reference sensors necessary for the new fixture to be tested with the electromagnetic generator are permanently attached to the current model. Extra reference sensors could not be located for testing.

– The design successfully replicated all but two of the positions due to an incorrect angle of the transducer holder.

– Future recommendations for the design include: using multiple pockets on the base instead of a rotating ratchet, changing the angles of the transducer holder to achieve all required positions, and lowering the EM generator to adjust for the shorter fixture design.

Outcomes

Some modifications are still required to perfect the new design, but should be achieved with one more iteration. The time deadline did not allow for testing of the final iteration, but as of now:

– The sponsor received the most updated model and is able to print and assemble the entire fixture.

– The fixture can be modified to accommodate different transducers by printing a new mold and base to adjust for the geometry changes.

– There is no longer need for approximation by the operator during testing, which will translate into more precise calibration.

– The new model’s design is more durable than the current model and has no small, unsupported pieces that are easily broken.

– The only customer need not directly addressed by the new design is cable management. Tests were not performed in the time frame to better address the issue.