This application report describes the integrated sensorless implementation of speed and position sensing using the current ripple of a brushed dc (BDC) motor. When an BDC motor application requires position and speed information of the motor, these are usually measured using encoders or hall effect sensors. Such designs are expensive, require more space, and are complex to design and maintain over the lifetime of an application. Texas Instruments DRV8214 and DRV8234 fully integrated BDC motor drivers eliminate the need for these external hall sensors and encoders. In addition to detailed description of the setup and tuning of this implementation, examples with test results are included. The accuracy of the test results under various test conditions is also analyzed.
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Brushed DC motors require the knowledge of real-time motor speed, voltage, position, temperature, etc. for functioning in a closed loop system. While existing drivers integrate current, voltage, and temperature sensing, speed and position sensing require the use of external sensors like optical encoders and hall effect based sensors. This leads to:
DRV8214 and DRV8234 implement an integrated ripple counting algorithm that enables sensorless speed and position sensing. This leads to significant system level benefits. Parameters can be tuned through I2C to achieve high accuracy results.