Case study

Medical patient simulator

  • Patient simulator for first-aid cardiac arrest training.
  • Precision vibration motor to haptic simulate ‘heartbeat’.
  • Precision motor with CNC enclosure, and very robust EMI / EMC protection.
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Challenge

  • Medical customer who had very specific requirements on quality and product performance.
  • They wanted to add haptic feedback to their ‘medical dummies’, to simulate the feeling of a patient’s heartbeat.
  • They were seeking a reliable manufacturing partner with rigorous design, validation, testing and quality procedures.
  • Precision Microdrives was asked to progress a prototype design using a custom vibration motor, and prepare the design for mass production.

Solution

  • A bespoke vibration motor with a custom winding tuned to operate at a specific speed (frequency).
  • Provided the necessary torque to reach operating speed for an unusually large eccentric mass within 400mS.
  • A CNC machined brass weight and aluminum enclosure with internal harmonics dampening.
  • PCB backpack and wireset, that contained very high performance EMI / EMC filters, to prevent disruption to medical equipment in a hospital environment.

Results

  • Powerful and realistic patient simulation now adopted world-wide.
  • Successfully managed our client’s risk with verified and reliable technology.
  • Carefully optimised for in-house manufacturing by in-house design-for-manufacturing teams.
  • Carton packing arrangement designed to optimise air freight shipping charges.

Project scope

Haptic feedback solution to simulate heartbeat in CPR training ‘dummy’

Haptics is often associated with touchscreens, but in this application, our customer introduced haptic feedback with a very different goal – to simulate the feeling of a patient’s heartbeat!  Our customer is a medical devices company with high expectations, and strict requirements on quality consistency and product performance. We were asked to progress a prototype that they had developed, design in a suitable vibration motor, and prepare the assembly suitable for mass production. 

The customer had the budget, volume and quality needs to justify the use of automated CNC manufacturing processes for several major components. Vibration resonance harmonics were an issue, requiring the addition of dampening inside the enclosure.

They also specified tight EMC interference limits, to avoid impacting nearby medical equipment. The complete unit also had to be IP rated requiring a suitable enclosure sealing method. Finally, we added a twisted pair wire-set and a Molex connector.

A medical profession practicing CPR on a patient simulator dummy.
Patient Simulation for CPR practice

STAGE 1

Designing for application

  • We designed the vibration motor with a custom winding to provide the necessary torque to drive the unusually large eccentric mass.
  • To generate the vibration G-forces for an accurate heartbeat simulation we optimised the motor windings and mass weight, which was then CNC machined in brass.
  • We added a PCB backpack for the motor onto which the high performance EMI filters were fitted.
  • The customer mapped out the envelope of the vibrating assembly so it could fit into the end product.

STAGE 2

Technical specifications

  • The enclosure was machined from aluminium alloy, with a carefully designed set of hooks to locate the assembly into the final application.
  • The split enclosure is held together by an integrated thread and IP67 sealed, with a silicon washer and suitable tightening torque.
  • The thread was introduced as part of the design for manufacture process making manufacturing more efficient and consistent.

STAGE 3

Precision manufacturing

  • We manufactured a large number of jigs and fixtures to aid assembly on our lines. We also built an end of line tester to ensure the vibration frequency and amplitude was optimal.
  • We understood our customer’s challenges and provided an effective solution to a very high standard, whilst reducing their risk.
  • We optimised the shipping for the customer, before they asked, by designing a carton packing arrangement suitable for air freight.

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