Open-Source Reference Board Accelerates Medical Ventilator Design
TRINAMIC Motion Control GmbH & Co. KG, now part of Maxim Integrated, today announced the TMC4671+TMC6100-TOSV-REF design board, a BLDC servo driver capable of 12V to 36V with up to 6A RMS to accommodate medical ventilator and respiratory system design. To shorten design cycles, the open-source module features a session border controller (SBC) connector in Raspberry Pi style and space for a pressure sensor add-on board.
Medical ventilator design must deploy sensor technology for monitoring and reacting to changes in pressure, flow, volume, respiration rate, and other parameters. For this reason, Trinamic’s reference design board includes a Hall sensor interface and connectors for an optional pressure sensor add-on board. As a result, important pressure data can be directly visualized on a Raspberry Pi with touch screen using the free firmware developed by Trinamic for the reference design board. Hardware and software are open-source, meeting the goals of the Trinamic Open-Source Ventilator (TOSV) project, which led to this reference design.
“The reference design shows engineers how to build medical ventilators using readily available components, bypassing the longer lead times of traditional components,” said Trinamic founder Michael Randt. “The design uses a dynamically controlled high-RPM turbine BLDC motor to allow the use of pressure and volume sensors to enable both pressure-controlled and flow-controlled ventilation modes. These important features enable engineers to address the immediate need for technologically advanced ventilators, which is being driven by the rapidly changing COVID-19 crisis.”
Trinamic’s previous experience with controlling CPAP device turbines showed that providing fast and dynamic control of low-induction BLDC motors can be exceptionally challenging. It requires careful consideration of the trade-off between high switching frequency and current ripples, and their consequent switching and stator losses, respectively.
Thanks to the embedded TMC4671 servo controller IC, the module generates a pulse-width modulation (PWM) frequency and a current controller clock of 100 kHz independent of the microcontroller. This approach reduces the system’s current consumption by up to 15 percent, compared with a frequency of 25 kHz, without compromising performance.
An add-on board for I2C and analog sensors supports pressure sensors offered by various manufacturers. The TMC4671+TMC6100-TOSV-REF plugs into a single-board computer to access the user interface and high-level control functions. Following the example of the TOSV project, the module uses Raspberry Pi with touch screen display.
The complete TMC4671+TMC6100-TOSV-REF reference board is available now through Trinamic’s distribution channels. All hardware, firmware, and software are open source under the MIT license.
Features and benefits:
- Single-axis BLDC servo driver for up to 6A RMS/phase
- Supply Voltage 12V to 36V
- Integrated overvoltage protection
- HALL sensor interface
- Onboard temperature sensor
- Digital I/O and analog inputs
- Addon board connector for standard or custom sensor interface board
- Raspberry Pi connector for external SBC