Current-saving sampling framework for the embedded implementation of positive position feedback

Battery powered embedded applications of active vibration control must conserve energy as much as possible, in order to prolongate effective service time between charging. Besides the power requirements of actuators and sensors, the microcontroller unit executing the feedback control algorithm drains the battery as well. Reducing the current drain of the microcontroller is possible by slowing down its clock frequency; or, sending the device into sleep mode when idle. This paper attempts to provide a definitive answer as to which of these strategies is better. A simple theoretical approximation derived here suggests that running the microcontroller at maximum frequency, then sending it to a low power mode is always preferable. We confirm this by laboratory experiments measuring the microcontroller power requirements of the positive position feedback algorithm. For this algorithm and choice of sampling time a five-fold current saving is possible on the Microchip (Atmel) ATmega 328p microcontroller unit, reducing its current draw from 15 mA to 3 mA. The experimental current and instantaneous power measurements shown in the paper confirm our prediction and general conclusion.