Design and analysis of a smart power management system for ultracapacitor-powered robotic platform

Abstract

Capacitors are well known for their long lifetime and ability to rapidly charge and discharge. However, these attributes come at the expense of a lower energy density than current rechargeable battery chemistries (NiMH, NiCad, Lithium, etc). Recent advances in double-layer electrolytic capacitors have increased their energy storage capabilities, allowing for the possibility to power unmanned systems that have traditionally been powered by rechargeable batteries. Capacitive energy storage is particularly interesting for collaborative robotic networks, where small scouting robots are powered for short missions by ultracapacitors, then return to a mobile re charging station to rapidly recharge and return to their mission. A system implementing capacitive energy storage, unlike rechargeable battery storage, requires additional power conditioning circuitry to overcome the capacitor's disadvantages, including a DC-DC converter to draw power as the capacitor's voltage lowers and current limiting to overcome the nearly short-circuit initial charging conditions. A robotic platform implementing smart charge and discharge circuitry for one to several kJ of capacitive storage was built and the performance is analyzed and discussed.