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Autonomous Robot AKA Squirrel Chaser
Autonomous

Autonomous Robot Build Notes A.K.A. The Squirrel Chaser

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This page is authored by Charlie P. Last Updated February 5, 2014. We will be updating this page as the build progresses and time permits, so keep coming back for more updates...

The image to the left is the current status of the robot at the time of this post. As we continue to build, wire, and program the robot, we will post an updated picture. (Only the very sharp observers will notice the program changes by looking at the image.) For a full resolution pictures of of the robot, click this link.

The Project scope, kind of...

So we are going to get started on a new fun project! With this project we plan on documenting everything for the public and making all our code and schematics open available for any hobbyist, enthusiast, and/or student to have complete access to how to build and program an autonomous robot featuring the Arduino Mega and eventually a Android Tablet controlled and monitored over 4G LTE. There are a lot of different ways of doing this project and some of the things we are doing are just for fun. An important thing to remember when designing an autonomous robot is that the more methods of sensing your environment and position the better. If you only plan on using one type of sensor, you will be struggling to get the robot to do anything slightly complicated. Since this project is not for any specific purpose or to any set requirements, we are just going to have some fun and build something cool...

So, the first thing that needs to be decided is what you want the robot to do. This can be a lofty goal to drive to, or maybe a very specific goal. In our case its a loft goal with a lot of side diversions and our favorite term "feature creep" The first thought was to build a robot that would chase squirrels, raccoons, and other varmints out of my back yard, to make it even more complicated it would be neat to not chase my cats or dogs? - thought is to put RFID tags on the "friendlies" that should be ignored, but that may be a way future version... Need a GPS to keep it in bounds, otherwise the neighbors may complain if their animals get chased by a rogue robot. We will start with sonar as the main object detection. Then put some encoders on the wheels so we can track how far we have traveled. Add some current monitoring to look at the motor draw and make sure the motors are not working too hard. Just for some fun, lets add a methane sensor and CO sensor to see if we can scare the S**t our the varmints. So that is the basic idea, but we will start with getting it so it just runs around without crashing into things, then we will add the chasing features, perhaps do something with the android tablet and use the camera, 4G LTE connection for control, etc. Maybe add a paint-ball turret on the top, etc.

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The Bill of Materials

Below is the robot grocery list... When selecting the parts for your robot, you can use the list as a reference, but as mentioned this robot build can be done so many different ways. We also offer Programmable Robot Kits. These kits can be configured with options at the bottom of the page. Its a great way to get started. Or you can do it from scratch similar to what we did here with this robot build.

Main Robot Chassis:

Sensors:

Power Regulation:

Control System (The Brains):

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The Chassis

We wanted to keep the cost down along with the complication, so we went with a wheeled robot. A wheeled robot is much easier and less expensive than a tracked robot. Since we are primarily interested in the sensors and autonomy of the robot and don't plan on taking on any aggressive terrain, wheels it is. However to keep it cool looking and let it get over some curbs, etc. we selected 10 inch tires. For general help on building a robot please be sure to go through our How to Build a Robot Support Page. We did not want to spend a lot of money on batteries and weight is not a real big concern, so we just when with simple Sealed Lead Acid Batteries. We decided to dedicate one battery to controls and run two separate batteries in series for the 24V drive power. We designed a upper deck for protecting all the lower electronics and mounting all the sensors. We then put protection over the sensors in the event the robot flips over it won't be a complete disaster.

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The Control System

For the control system we went with the Arduino. Its a great controller, easy to use, powerful, and has a huge open source community. Be sure to check out our MicroController Support Page.. We will use a servo controller to take the burden off the Arduino for sending the required servo pulse train.

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The Build

Wiring the Robot

The electrical Wiring was fairly straight forward with a couple added features. For the Drive motors, we need 24VDC. So We just took two 12V Batteries and ran them in series. The Ground was put to a ground lug, that we made a stud for top and bottom of the chassis for easier routing of the wires. The +24V went to a fuse block, then to a switch, where we paralleled a charging plug. The normally off side of the switch then went through the current monitor, then to the terminal block. We new controls were going to be important on this robot, so we gave the control system its own 12V battery. It followed the same path: out the battery to a fuse, to the switch (DPST) paralleled with a charging cable, then trough a current monitor to the terminal block. The voltage regulators, motor controller, etc fed off the terminal block. The regulators: 5V for all the sensors (the SDR Arduino expansion board has a regulator on it, but with the amount of sensors we are running, we decided to add an additional 1.5A regulator run in parallel with the expansion board regulator), 6V for the servos were fed back to the terminal block so all the loads can be easily connected.

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Mounting the Sensors

It was obvious right out of the gates that we needed a upper deck to hold all the sensor, so we built one. We are starting with 5 sensors on servos up in the front, and one in the rear. The 5 front sensors will be used to provide a forward looking radar arc. The outer two sensors will pan to the sides when turning, etc. to see if its clear. The back sensor will be used for a rear look in the event of backing up. The IMU was mounted in the middle of the robot to provide the most accurate analysis of the robots acceleration, tilt, heading, etc. The GPS and gas sensors were mounted in the back above the rear sensors.

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Adding more Stuff!

We added a coupling chain to couple the right front to the right rear and the left front to the left rear. This makes the motors work together, which is ideal for autonomous operation and it provides better power too. This is a option is available for our heavy duty ATRs in the assembly. This robot is a standard IG42 ATR, which can also be modified with this modification, just let us know if you want this feature and we can install it or you can get your own chain and sprockets and do the coupling yourself.

We also decided to design and mount a TD-133-000, ATR Rigid Bumper Assembly on and the front and back of the robot. With an autonomous robot a bumper is critical. The wheels of the robot protrude out past the front of the chassis, which in some situations makes it great for climbing over obstacles, but with an autonomous robot that may go astray and drive into something like a wall, it will climb the wall and flip. The bumpers will help prevent this from happening.

Yet another accessory for an ATR, that we have put on many custom ATRs is a bottom skid plate to protect the motors, keep debris and water off the motors and electronics. We decided to make this a standard item. TD-134-000, ATR Bottom Skid Guard and Cover Assembly is our new item. It is not waterproof, but it will prevent water from splashing up, etc when going trough puddles or over wet grass and leaves, etc.

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Wiring the Sensors

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Programming the Robot

The first step is to download the Arduino programmer. Its a free download.

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Summary and remaining Tasks

-The End (for now...)

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Autonomous Robot Build Notes for a custom robot with the ultimate goal of chasing squirrels.
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