IM2 – Intelligent Management of MicroPower

Significance 

Technological advances have enabled the development of microcontrollers that are vital for keeping computing devices alive for extended periods of time, with minimal energy consumption. Ultimately, by employing this notion for the case of a renewable energy source, it should be possible to power a low microcontroller indefinitely. But one may ask, why do such a thing? Basically, noteworthy literature has demonstrated the development of self-powered sensor nodes. More so, sensor nodes generally take infrequent measurements of data which are then logged for later use. The norm for such systems has been ‘run-deplete-replace’ approach using common batteries. In line with other global trends focusing on renewable energy, it would be prudent to develop an inexhaustible power system for microcontrollers. If a renewable resource is managed correctly, it is possible to charge and maintain an accumulator such as a Supercapacitor. Microcontrollers that have deep sleep modes can enter into very low power modes and consequently tailor their behavior to the resources available to them.

An obvious question is why keep the MCU alive at all, if the voltage dips below 1.8v just let it until sufficient energy becomes available again. Whilst this approach does have some merit, MCUs as they approach their operational voltage (from below) take significant amounts of current and may consume more energy than being generated without becoming operational. Low voltage lockout circuits exist which can prevent this but they often use more in standby than the MCU whilst operational. Consequently, in the event of under voltage the current program state is lost (in RAM) meaning that any long-term data needs to be written to ROM. In fact, in the event where no under voltage protection is employed, there is the very real possibility of ROM and program memory corruption as well. To address this shortfall, researchers from the School of Computer Science and Electronic Engineering at University of Essex in England; Mr. Michael Walton and Dr. John Woods, proposed to develop an intelligent algorithm to manage received wireless power to do useful work even though there is insufficient energy to do the work directly. Their work is currently published in the research journal, Nano Energy.

The basis of their approach was the addition of a microcontroller to a low power charging resource to maximize the work done for a given input source. Their assumption was that the resource is inadequate to drive the load directly; this being ubiquitous in energy harvesting systems. Specifically, the example ultralow power microcontroller they employed was the ATtiny85, although their approach is applicable to a whole family of similar micros.

The authors reported that their algorithm made intelligent decisions whether to sleep or wake according to the amount of received and stored energy. In other words, by using an ultralow power microcontroller that makes sleep and awake decisions in order to accumulate the maximum amount of usable energy, utilization was achieved. The two researchers further noted that at the appropriate time, the micro woke up and briefly ran the load, keeping sufficient power to allow it (the micro) to stay alive.

In summary, Walton and Woods study presented an algorithm to run a load with a source which has less energy than the load’s continuous requirements. This was inspired and motivated by the ideology that power management can be achieved by implementing intelligent control in the design of a wireless power transfer system, but has far reaching implications for other low power applications. The pros of the presented approach were the ease of realizing the code and the fact that it could achieve best case utilization from just two readings. In a statement to Advances in Engineering, the authors explained that by using an adaptive strategy of this kind, the amount of work can be precisely matched to the resources available to achieve maximum utilization with the objective of keeping the device alive for as long as possible subject to the satisfactory completion of a stated set of tasks. “Currently, energy is managed according to the requirements of the job, this work approaches from an opposite direction where the energy defines the job that can be performed or when it can be performed based on time dilation” said the first author, Michael Walton.

About the author

Michael Walton Has been working in the field of electronics and design for the past 20 years and is also employed as a lecturer at the University of Essex where he teaches Electronics and computer languages. Currently working on a PhD which focuses on energy harvesting, wireless energy transmission and efficient energy storage and utilization his interests allow him to actively participate in leading edge energy sensitive device design.

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About the author

Dr John Woods Has worked at the University of Essex for the last 25 years where he is a senior lecturer and currently the director of education in the CSEE department with over 1300 students. He has a variety of research interests including networking, image processing, artificial intelligence, human computer interaction but more recently renewable energy systems and the utilization thereof, this has led to a number of pieces of work which are looking at power utilisations in the nano watt range to power small robotic devices.

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Reference

Michael Walton, John Woods. Intelligent control of micro power – Immortal machine. Nano Energy; volume 72 (2020) 104699.

Go To Nano Energy

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