A lightweight high-voltage boost circuit for soft-actuated micro-aerial-robots

Flight is an energetically expensive task. While aerial insects can effortlessly fly through natural environments, achieving power autonomous flights in insect-scale robots remains a major challenge. In prior works, we developed soft-actuated insect-scale aerial robots that demonstrated unique capabilities such as in-flight collision recovery and somersaults. However, the soft dielectric elastomer actuators (DEAs) have low efficiency (< 20%) and require a high driving voltage (>600 V). These properties represent formidable obstacles for soft aerial robots to achieve power autonomous flights. In this work, we developed a 127 mg boost circuit that can convert a 7.7 V DC input into a 600 V and 400 Hz output for driving a 120 mg DEA. It has an equivalent capacitance and resistance of 20 nF and 5 $\mathbf{k}\Omega$, respectively. The DEA is assembled into a 158 mg aerial robot, which can demonstrate liftoff while carrying the boost circuit as a payload. Although the robot remains tethered to an off-board power supply, this result represents a first step towards achieving power autonomy in soft aerial robots.

I. Introduction

Insects are ubiquitous in nature. Owing to their small sizes, insects can perform impressive and unique tasks such as climbing on walls, traversing the water surface, and pollinating flowers. While autonomous exploration of the natural environment seems effortless for insects, similarly sized robots struggle to achieve power autonomy due to a suite of major challenges. First, developing insect-scale (< 1 g) robots requires microscale (0.01 – 0.1 g) structures, transmissions, and actuators. Second, lightweight power electronic circuits are required for driving micro-actuators that often need high voltages (> 100 V). Third, compact energy sources such as batteries and solar cells need to be incorporated onboard. All these essential microrobotic components need to fit into an insect-scale system, which poses significant challenges in design, actuation, power electronics, and fabrication. In the past decade, advances in the abovementioned research areas have led to several power autonomous insect-scale robots. Huang et al. [1], [2] developed shape memory alloy (SMA) driven robots capable of terrestrial and aquatic locomotion. SMAs only require a low voltage (< 10 V) and low frequency (< 20 Hz) driving signal, hence it is easier to develop compact onboard electronics. However, the power density and controllability of SMAs are substantially smaller than that of insect muscles, which limit microrobot speed, maneuverability, and payload. To obtain higher bandwidth and power, other types of micro-actuators such as piezoelectric ceramics [3], polyvinylidene fluoride (PVDF) [4], and DEAs [5] have been applied in sub-gram terrestrial robots. Boost circuits capable of delivering 200 – 600 V driving signals have been developed for these high voltage actuators. These robots can carry a 0.5 – 1.0 g onboard battery and demonstrate power autonomous operation for 5 – 13 minutes [3]–[5]. Fig. 1.

An image of a 158 mg soft-actuated aerial robot that carries a 127 mg boost circuit. This insect-scale dea-driven robot can demonstrate liftoff flights while carrying the circuit.