Have you considered using back-emf observers for sensorless speed estimation? - Industrial - Technical articles - TI E2E support forums
![Figure I from Analysis of position and speed control of sensorless BLDC motor using zero crossing back-EMF technique | Semantic Scholar Figure I from Analysis of position and speed control of sensorless BLDC motor using zero crossing back-EMF technique | Semantic Scholar](https://d3i71xaburhd42.cloudfront.net/4b11c159945ad8baa0f13f4ab83694146f72d2ba/2-FigureI-1.png)
Figure I from Analysis of position and speed control of sensorless BLDC motor using zero crossing back-EMF technique | Semantic Scholar
![Electronics | Free Full-Text | Nested High Order Sliding Mode Controller with Back-EMF Sliding Mode Observer for a Brushless Direct Current Motor Electronics | Free Full-Text | Nested High Order Sliding Mode Controller with Back-EMF Sliding Mode Observer for a Brushless Direct Current Motor](https://pub.mdpi-res.com/electronics/electronics-09-01041/article_deploy/html/images/electronics-09-01041-ag.png?1592988957)