project specification

BOLT

BOLT (or Bipedal Ornithopter for Locomotion Transitioning) is a small flapping wing micro-air vehicle (MAV) The robot has tiny legs that help it save energy by moving around on the surface before taking flight. In running modes, the wings also provide passive stability. Flapping flight provides the high maneuverability necessary for operation in a partially structured indoor environment. To achieve robust intelligence for tasks such as search and indoor navigation, the maneuverability of the ornithopter is combined with a learning approach which makes minimal assumptions about the nature of disturbances and obstacles.

Specifications

Length28 cm
Width17.5 cm
Depth15 cm
Weight11.4 g
Running speed2.5 m/sec
BatteryFull River 60 mAh lithium polymer
Micro-controllerMicrochip dsPIC33F
CommunicationsAtmel AT86RF231
AccelerometerAnalog Devices ADXL345
GyroscopeInvensense ITG-3200

Overview

The robot combines the gearbox and wings from a commercial ornithopter (Air  HogsTMV-wing AvengerTM) with a custom airframe, leg design, and electronics package. A single motor drives both the leg and the wings, allowing sufficiently high power density to maintain hoveringflight.

The integration of an electronics package allows two-way communication and the investigation  of the robot dynamics with a six-axis inertial measurement unit  (IMU).

Airframe Design 

BOLT’s airframe uses carbon fiber spars for structural rigidity. The lightweight properties of carbon fiber make it ideal for use in a flying platform. A rigid airframe is critical in preventing serial compliance from reducing the wing thrust. For the lightweight tail, carbon  fiber spars have been placed in a card board pattern and a film of polyethylene terephthalate (PET) is overlaid and attached to the spars with cyanoacrylate.

The center of mass location of the robot is important for determining the posture of the robot when it is in the air. The battery is placed at the very posterior of the robot on the tail, the controller board is placed within the airframe. This gives the robot a vertical posture, with the majority of the wing thrust directed downward. By adjusting the position of the controller board, the robot can be set to either hover in place or fly forward at a slow rate. The airframe of the robot also protects the controller board during operation. 

Leg Design 

BOLT has a bipedal leg design, with each leg going through a symmetrical motion 180 degrees out of phase with the another. The legs are built using the SCM process ,which  allows  the  implementation of a lightweight structure that transforms the output of the motor to the desired leg trajectory.   

Four layers of unidirectional carbon fiber pre-preg are sandwiched around PET to create the leg structure. The layers of the unidirectional carbon fiber are arranged crosswise to provide stiffness in two directions, and are mirrored across the flexure layer. The structure is designed to provide protection to the hips in case of high velocity impacts, while allowing the legs to still extend in front and below the body. 

Power, Communications, and Control

BOLT uses a custom electronics package that  incorporates a 40 MHz dsPIC processor with a motordriver, six-axis IMU, and 1 MB of Flash memory. In addition, the board has an Atmel 802.15.4 radio for communication with a laptop. A Python interface sends commands to the robot and receives data from the board’s sensors. A 60 mAh battery powers the electronics board and motor.

References

Describes the project, the mechanical design, airframe design, and leg design. Describes the power, communication, and control. Goes into the methods and results, followed up by a discussion.

Kevin Peterson and Ronald S. Fearing

This dissertation presents the development of DASH+Wings and BOLT.

Kevin Charles Peterson