Sunday, November 08, 2009

Flying Robot Project

The HoverBot C
An Electrically Powered Flying Robot

This paper describes the development of a fully autonomous or semi-autonomous
hovering platform, capable of vertical lift-off and landing without a launcher, and capable of
stationary hovering at one location. The idea to build such a model-sized aerial robot is not new; several other research institutes have been working on aerial robots based on commercially available, gasoline powered radio-control model helicopters. However, the aerial robot proposed here, called the HoverBot, has two distinguishing features: The HoverBot uses four rotor heads and four electric motors, making it whisper-quiet, easy-to-deploy, and even suitable for indoor applications. Special applications for the proposed HoverBot are inspection and surveillance tasks in nuclear power plants and waste storage facilities.

Without a skilled human pilot at the controls, the foremost problems in realizing a model helicopter-sized flying robot are stability and control. It is necessary to investigate the stability and control problems, define solutions to overcome these problems, and builde a prototype vehicle to demonstrate the feasibility of the solutions. The proposed HoverBot will have eight input sensors for stability and control, and eight output actuators (4 motors and 4 servos for rotor pitch control). The resulting control system is a very complex, highly non-linear Multiple-Input Multiple-Output (MIMO) system, in which practically all input signals affect all output signals. A surprisingly simple experimental control method, called additive control, is proposed to control the system. This method was successfully used in the current experimental prototype of the HoverBot (although with fewer input signals). It is also proposed to investigate two alternative control methods, adaptive control and neural networks, both of which appear to be especially suitable for the Multiple-Input Multiple-Output control problem.
If successful, the project will result not only in a working prototype of a flying robot, but
it will also provide important insight into the functioning of various control methods for very
complex MIMO systems.

Control of the HoverBot
The control system of the HoverBot is designed to allow either fully autonomous operation or remote operation by an unskilled operator. To either, the HoverBot will appear as an
omnidirectional vehicle with 4 degrees of freedom: (1) up/down (2) sideways, (3) forward/backward, and (4) horizontal rotation.

Creation of a Learning, Flying Robot by Means of Evolution
We demonstrate the first instance of a real
on-line robot learning to develop feasible
flying (flapping) behavior, using evolution.
Here we present the experiments and results
of the first use of evolutionary methods for
a flying robot. With nature's own method,
evolution, we address the highly non-linear
fluid dynamics of flying. The flying robot is
constrained in a test bench where timing and
movement of wing flapping is evolved to give
maximal lifting force. The robot is assembled
with standard o®-the-shelf R/C servomotors
as actuators. The implementation is a conventional

steady-state linear evolutionary algorithm.

Five servomotors are used for the robot. They are
arranged in such a way that each of the two wings has
three degrees of freedom. One servo controls the two
wings forward/backward motion. Two servos control
up/down motion and two small servos control the twist
of the wings. The robot can slide vertically on two steel
rods. The wings are made of balsa wood and solar,
which is a thin, light air proof ¯lm used for model
aircrafts, to keep them lightweight. They are as large
as the servos can handle, 900 mm.

Energy-efficient Autonomous Four-rotor Flying Robot
Controlled at 1 kHz

—We describe an efficient, reliable, and robust fourrotor
flying platform for indoor and outdoor navigation. Currently,
similar platforms are controlled at low frequencies due
to hardware and software limitations. This causes uncertainty
in position control and instable behavior during fast maneuvers.
Our flying platform offers a 1 kHz control frequency and
motor update rate, in combination with powerful brushless
DC motors in a light-weight package. Following a minimalistic
design approach this system is based on a small number of lowcost
components. Its robust performance is achieved by using
simple but reliable highly optimized algorithms. The robot is
small, light, and can carry payloads of up to 350g.

Our flying robot has a classical four rotor design with
two counter rotating pairs of propellers arranged in a square
and connected to the cross of the diagonals. The controller
board, including the sensors, is mounted in the middle of the
cross together with the battery. The brushless controllers are
mounted on top of the booms. Figure I shows a photograph
of the flying robot. The weight without battery is 219g. The
flight time depends on the payload and the battery. With
a 3 cell 1800mAh LiPo battery and no payload the flight
time is 30 minutes. We measured the thrust with a fully
charged 3 cell LiPo (12.6V) at 330g per motor. With four
motors the maximum available thrust is 1320g. Since the
controllers need a certain margin to stabilize the robot also
in extreme situations, not all the available thrust can be used
for carrying payload. In addition, efficiency drops and as
a consequence flight time decreases rapidly with a payload
much larger than 350g. Because of this we rate our robot for
a maximum payload of 350g.

With a 350g payload, a flight time of up to twelve minutes
can be achieved. The maximum diameter of the robot without
the propellers is 36.5cm. The propellers have a diameter of
19.8cm each. The sensors used to stabilize the robot are very
small and robust piezo gyros ENC-03R from Murata [14].
The second design iteration of this robot is already functional
but not fully tested and characterized experimentally. This
second version additionally has a three axial accelerometer
and relies on datafusion algorithms, still running at 1kHz,
to obtain absolute angles in pitch and roll.

The ROBUR project: towards an autonomous
flapping-wing animat


Flapping-wing flight is not applicable to huge aircrafts, but has a great potential for micro UAVs - as demonstrated by real birds, bats or flying insects. The ROBUR project aims at designing a robotic platform that will serve to better understand the design constraints that this flying mode entails, and to assess its capacity to foster autonomy and adaptation. The article describes the major components of the project, the tools that it will call upon, and its current state of achievement.
Research on flapping flight maneuverability
A generic model of a flapping wing aircraft has been designed, in which lifting surfaces are
modelled by a set of articulated panels (figure 2). In a first stage, this model will be used to
design a simple periodic controller for such a platform by using evolutionary algorithms (figure
3). This controller is expected to generate a periodic, horizontal, flapping flight at a constant

Physical model used in this project.

Quad-Rotor Flying Robot

New German UAV – microdrone
A high technology very small UAV made in germany by microdrone GmbH. Can reach an altitude of 400m and stay in the sky for 30 minutes

QTAR: Quad Thrust Aerial Robot 2005

Buy Flying Robot

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