# New Wing Stroke and Wing Pitch Approaches for Milligram-scale Aerial Devices

## TL;DR

This paper introduces a simple, universal transmission mechanism for milligram-scale aerial devices that converts linear actuator motion into wing stroke and pitch, simplifying design and enabling post-fabrication adjustments.

## Contribution

It presents the simplest compliant, planar transmission mechanism for converting linear motion to wing stroke and a passive wing pitch system that reduces aerodynamic coupling.

## Key findings

- Mechanism can convert linear motion to ±60° wing stroke
- Passive wing pitch mechanism decouples wing kinematics from aerodynamics
- Design is universal, fabricable in a single step, and adjustable after fabrication

## Abstract

Here we report the construction of the simplest transmission mechanism ever designed capable of converting linear motions of any actuator to $\pm$60$^\circ$ rotary wing stroke motion. It is planar, compliant, can be fabricated in a single step and requires no assembly. Further, its design is universal in nature, that is, it can be used with any linear actuator capable of delivering sufficient power, irrespective of the magnitude of actuator displacements. We also report a novel passive wing pitch mechanism whose motion has little dependence on the aerodynamic loading on the wing. This exponentially simplifies the job of the designer by decoupling the as of yet highly coupled wing morphology, wing kinematics and flexure stiffness parameters. Like the contemporary flexure-based methods it is an add-on to a given wing stroke mechanism. Moreover, the intended wing pitch amplitude could easily be changed post-fabrication by tuning the resonance mass in the mechanism.