Insect-controlled Robot: A Mobile Robot Platform to Evaluate the Odor-tracking Capability of an Insect

Summary

The capability to localize an odor source is necessary for insect survival and is expected to be applicable to artificial odor-tracking. The insect-controlled robot is driven by an actual silkmoth and enables us to evaluate the odor-tracking capability of insects through a robotic platform.

Abstract

Robotic odor source localization has been a challenging area and one to which biological knowledge has been expected to contribute, as finding odor sources is an essential task for organism survival. Insects are well-studied organisms with regard to odor tracking, and their behavioral strategies have been applied to mobile robots for evaluation. This "bottom-up" approach is a fundamental way to develop biomimetic robots; however, the biological analyses and the modeling of behavioral mechanisms are still ongoing. Therefore, it is still unknown how such a biological system actually works as the controller of a robotic platform. To answer this question, we have developed an insect-controlled robot in which a male adult silkmoth (Bombyx mori) drives a robot car in response to odor stimuli; this can be regarded as a prototype of a future insect-mimetic robot. In the cockpit of the robot, a tethered silkmoth walked on an air-supported ball and an optical sensor measured the ball rotations. These rotations were translated into the movement of the two-wheeled robot. The advantage of this "hybrid" approach is that experimenters can manipulate any parameter of the robot, which enables the evaluation of the odor-tracking capability of insects and provides useful suggestions for robotic odor-tracking. Furthermore, these manipulations are non-invasive ways to alter the sensory-motor relationship of a pilot insect and will be a useful technique for understanding adaptive behaviors.

Introduction

Autonomous robots capable of finding an odor source can be important for the safety and security of society. They can be used for the detection of disaster victims, of drugs or explosive materials at an airport, and of hazardous material spills or leaks in the environment. At present, we rely entirely on well-trained animals (e.g., dogs) for these tasks, and robotic odor source localization has been strongly expected to relieve the workload of these animals. Finding an odor source is a challenging task for robots because odorants are distributed intermittently in an atmosphere¹; therefore, continuous sampling of the odor concentration gradient is n....

Protocol

1. Experimental Animal

1. Prepare a plastic box to keep the pupae of male silkmoths (B. mori) until their eclosion. Put paper towels at the bottom and pieces of cardboard around the inner wall of the box (Figure 1A).
   Note: The pieces of cardboard are necessary for the adult moths to hold while extending their wings during eclosion (Figure 1A).
2. Put male silkmoth (Bombyx mori) pupae in the box and keep them in an incubator until eclosion under a 16-hr:8-hr light:dark cycle at 25 °C.
   NOTE: The male and female pupae can be discriminated by the sex markings on the abd....

Results

We present here the basic characteristics of the insect-controlled robot required for the successful localization of an odor source. The comparison between the robot and silkmoths, the effectiveness of the odor delivery system, and the significance of accurate bilateral olfactory and visual inputs are examined.

The comparison of odor-tracking behaviors between freely-walking moths and the insect-controlled robot is shown in

Discussion

The most important points for the successful control of the robot by a silkmoth are letting the moth walk smoothly on the air-supported ball and the stably measuring the ball rotation. Therefore, tethering the silkmoth and mounting it on the ball at the appropriate position are the critical steps in this protocol. Inappropriate adhesion of the moth to the attachment or inappropriate positioning of the moth on the ball will cause unnatural pressure on it, which perturbs its normal walking behavior and/or causes a failure .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Male adult silkmoth (Bombyx mori)			Rear from eggs, or purchase as pupae.
Incubator	Panasonic	MIR-254	Store pupae or adult silkmoths at a constant temperature, 238 L.
Plastic box	Sunplatec	O-3	Store pupae or adult silkmoths, 299 × 224 × 62 mm L × W × H.
Copper wire			2-mm diameter for the attachment. Any rigid bar can be used as an alternative for making the attachment to tether a silkmoth.
Plastic sheet	Kokuyo	VF-1420N	Sold as overhead projector film with thickness of 0.1 mm. Use at the tip of the attachment.
Forceps	As one	5SA	Remove scales on the thorax.
Adhesive	Konishi	G17	Bond a silkmoth to the attachment.
Insect-controlled robot	Custom		Bearing an air-supported treadmill, an optical sensor, custom-built AVR-based microcontroller boards, and two DC brushless motors. It is powered by 8 × AA and 3 × 006P batteries.
Microcontroller	Atmel	ATMEGA8	A component of the insect-controlled robot.
DC blower	Nidec	A34342-55	A component of the insect-controlled robot for floating a ball in an air-supported treadmill.
DC fan	Minebea	1606KL-04W-B50	A component of the insect-controlled robot for suctioning air containing an odor.
Optical mouse sensor	Agilent technologies	HDNS-2000	A component of the insect-controlled robot, obtained from an optical mouse (M-GUWSRSV, Elecom, Japan).
Brushless motor	Maxon	EC-45	A component of the insect-controlled robot for driving a wheel.
White polystyrene ball			A component of the insect-controlled robot. Diameter 50 mm, mass approximately 2 g.
Bombykol: (E,Z)-10,12-hexadecadien-1-ol	Shin-Etsu chemical		Custom synthesis.
n-hexane	Wako	085-00416	Solvent for bombykol.
Wind tunnel	Custom		Pulling-air type, sized 1,800 × 900 × 300 mm L × W × H.
BioSignal program	Custom		A program to establish serial communication between the insect-controlled robot and a PC via Bluetooth. Used for sending commands to start/stop the robot or configuring its motor properties.
Camcorder	Sony	HDR-XR520V	Capture robot movements.