Design Considerations (continued)

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來自 University of Pennsylvania 的課程

Robotics: Aerial Robotics

1938 個評分

University of Pennsylvania

Robotics: Aerial Robotics

1938 個評分

課程 1（共 6 門，Specialization Robotics）

How can we create agile micro aerial vehicles that are able to operate autonomously in cluttered indoor and outdoor environments? You will gain an introduction to the mechanics of flight and the design of quadrotor flying robots and will be able to develop dynamic models, derive controllers, and synthesize planners for operating in three dimensional environments. You will be exposed to the challenges of using noisy sensors for localization and maneuvering in complex, three-dimensional environments. Finally, you will gain insights through seeing real world examples of the possible applications and challenges for the rapidly-growing drone industry. Mathematical prerequisites: Students taking this course are expected to have some familiarity with linear algebra, single variable calculus, and differential equations. Programming prerequisites: Some experience programming with MATLAB or Octave is recommended (we will use MATLAB in this course.) MATLAB will require the use of a 64-bit computer.

從本節課中

Introduction to Aerial Robotics

Welcome to Week 1! In this week, you will be introduced to the exciting field of Unmanned Aerial Robotics (UAVs) and quadrotors in particular. You will learn about their basic mechanics and control strategies and realize how careful component selection and design affect the vehicles' performance. This week also provides you with instructions on how to download and install Matlab. This software will be used throughout this course in exercises and assignments, so it is strongly recommended to familiarize yourself with Matlab soon. Tutorials to help you get started are also provided in this week.

Basic Mechanics4:27

Dynamics and 1-D Linear Control10:29

Design Considerations3:37

Design Considerations (continued)4:33

Agility and Maneuverability7:00

Component Selection4:24

Effects of Size4:38

Supplementary Material: Introduction3:19

Supplementary Material: Dynamical Systems3:15

Supplementary Material: Rates of Convergence3:20

與講師見面

Vijay Kumar
Nemirovsky Family Dean of Penn Engineering and Professor of Mechanical Engineering and Applied Mechanics
School of Engineering and Applied Science

So now we've studied the effect of thrust to weight ratio,

let's now look at the power consumption of each robot.

So in this picture I show you six different robots that

we've built in a laboratory.

Each one uses a different motor, has a different frame and

has a different payload.

So because of that the thrust to weight ratio is different, and

the power consumed is also different.

If you plot the power drawn as a function of thrust for a given robot,

you'll find that the slope of this curve is roughly 200 watts per kilo.

If you look at the power consumed and

the power delivered by different types of batteries, you'll find

the blue dots show the power consumption, which is around 200 watts a kilo.

And, thankfully, the batteries produce more than 200 watts per kilo.

So this gives you some idea of how to pick batteries so

that you can actually support the power consumption for

the motors and provide extended life for the quadrotor.

So when you think about system design, you have to think about battery selection, and

when you think about battery selection,

you have to think about the power consumption.

In addition to power consumption,

you also have to think about the total energy carried by the battery.

In this plot, we show the specific power

plotted against the specific energy for a variety of batteries.

On the y axis you see watts per kilo, on the x axis, you see watt hours per kilo.

You'll see that most lithium polymer

batteries produce around 200 watt hours per kilo.

There's really nothing on the right side of this band.

To contrast that with how humans perform,

if you look at a piece of adipose tissue or fat.

That carries about 10,000 watt hours per kilo.

This is several hours of magnitude more energy then is carried by batteries.

If you look at the power consumption,

robots consume about 200 watts per kilo per hour.

If you look at humans,

we consume a lot less than that to walk around, or even to run.

In fact, if you look at the fastest man on Earth,

Usain Bolt, he's estimated to consume about 20 watts per kilo.

So our robots are ten times more inefficient, than possibly the most

inefficient man on Earth, as he runs the hundred meters race in ten seconds.

Even if you look at bicyclists like Lance Armstrong,

he consumes about six watts per kilo.

So the moral of the story is our robots are inefficient, actually hovering

is an inefficient mechanism, so we needs lots of power to power our robots.

And if you look at lithium polymer batteries which represent the best choice

of batteries today, they don't carry a lot of energy.

So what do we do when we need a lot of power, and

we don't have batteries that carry a lot of energy?

Well, we can try to reduce our weight and go on a diet.

And that's what we try to do in the lab, we try to build smaller and

lighter quad-rotors.

If you at the mass distribution in a quad-rotor and

look at different components, how they contribute to the total mass,

you will see a lot of variability.

You'll see that the batteries contribute about 33% of the total mass and

the motors plus propellers contribute about 25% of the total mass.

Of course, if you add sensors like laser scanners and cameras,

the increases the total mass also.

If you take a laser scanner with a range of about 30 meters,

it consumes about 10 watts for operation, but

because it weighs 270 grams, it consumes another 50-60 watts for mobility.

Here's a camera system that weighs about 80 grams.

it costs us 1.5 watts to operate this camera plus an additional 15 watts for

mobility.

So when thinking about the payload we want to also think about

the power consumed in addition to the thrust to weight ratio.

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