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Thread: New Rover Project Bulit on ER-1 Platform

  1. New Rover Project Bulit on ER-1 Platform

    Hello All! I have been lurking for a while and I am about to start off on my first real robotics project. I am just starting the planning phase right now. ALL feedback and suggestions are welcome!

    Here is what I would like to accomplish:

    I would like a butler/assistant type of bot. He should be able to navigate around independently. I would like to have some speech recognition for issuing commands. Facial recognition would be nice to have. Some type of gripper would be nice too. I would like to be able to control the bot remotely as well.

    Here is what I have

    Evolution Robotics ER-1 The battery is dead, so I am not even sure that the controller works. Either way, I will probably scrap that and will be looking for a new one. The ER1 software is pretty limited. The stepper motors are pretty nice but I am not sure I will be able to get them working with another controller. If not, I'm just left with the makerbeam frame. I ordered a 900mm makerbeam to elevate the main camera to eye level(ish)

    Here is what I am thinking

    Kinect Camera for main vision
    2 additional cams to aid navigation mounted near the base facing rear and forward
    Several IR sensors for obstacle avoidance.
    Not sure what I should do for a controller. The ER1 was meant to carry a laptop but would be open to any advice here. I do have an old laptop that I could use. I also have a RasPi sitting around.
    I will need a battery - also need suggestions here.

    A little about me:

    I have been in IT for over 15 years and currently work as Virtualization Engineer. I have some programming experience but not in C or Python. I am a fast learner lol. I have some soldering and electronics skills. I also have a friend with a 3D printer.

    Thanks for taking the time to read this! Please let me know what you think.

    Here are some pics



    [IMG]www.bobnatale.com/public/er1-1.jpg[/IMG]
    [IMG]www.bobnatale.com/public/er1-2.jpg[/IMG]
    [IMG]www.bobnatale.com/public/er1-3.jpg[/IMG]

  2. #2
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    Re: New Rover Project Bulit on ER-1 Platform

    There are lots of mobile robots that use only the kinect/primesense to successfully navigate and interact (several on this forum, plus the TurtleBot, the cheaper PR1, and all UBR-1), so the extra cameras and distance sensors would probably not be necessary unless it operates in really tight and cluttered environments (PR2 and UBR-1 have laser rangefinders in their bases to ensure good navigation data, especially outside the kinect's sensing range). The RaspberryPi is not really great for handling USB cameras (webcams or the kinect), but not impossible to use. Most of those on the forum who have tried the RPi with kinect usually ran into the limitations quickly and upgraded to an Intel NUC or a Zotac Zbox.

    ROS has a high learning curve, but it is really well suited for the navigation and arm control, and it is really easy to add voice control and remote control. There are several similar robots on the forum using the kinect and dynamixel servos; the closest to yours are Maxwell (built by Willow Garage alum, now Unbounded Robotics member, also responsible for the arbotix) and PiRobot (builder wrote a book on learning ROS by example), but there are also several very awesome quads/hexs/octos.


    LiFePO4 batteries are great for safety and charge cycle endurance (>1000~2000 cycles), but can be a bit more expensive (initially) than LiPo because of different adoption rates. LiPo is usually inexpensive because of laptop and hobby use, but require careful charging/handling and have shorter endurance/lifetime (300~500 cycles). Pb-Acid is easy to charge, but really heavy and relatively short endurance/lifetime (~200 cycles). NiCd are not commonly available anymore, and NiMH is just crap. Lithium-Titanate are really cool, but not yet cheaply available in quantities required for a larger rover.


    Stepper motors are super easy to control, but getting really accurate fractional-step control requires fancy stuff. Unipolar steppers only need 4 transistors and a power supply (can control either high-side or low-side). Bipolar stepper motors require two H-bridge drivers to control them. Bipolar-hybrid steppers like those on the bot are very common in industrial spaces and CNC mills, so usually can get them cheap as used/surplus. Finding a dedicated controller for larger stepper motors like those can be a bit expensive because of the higher voltage and current, but I think CNC upgrade kits for mills might be a relatively inexpensive source.
    That said, stepper motors are not a very common wheel drive source and can be a bit loud (remember someone using the steppers in a makerbot printer to play music). It can simplify control since external sensors are not needed to know how much the wheel has rotated in a given time (just count the steps you've ordered the controller to take; assumes motor is not overloaded and slipping), but the expense of the motor controllers and size/weight of adequate stepper motors tends to limit their use in mobile robots.

    If searching for replacement motors, Pololu has several easily controlled DC gearmotors with quadrature encoders on the motor, as well as numerous motor driver boards. Not sure they would be sufficiently powerful for a larger bot, which is where FIRST-legal kits start to enter the fray (banebots and andymark make the gearheads and resell the motors). Unfortunately, they do not usually have encoders since the robots are mostly remote controlled. There are plenty of quadrature encoders available one could add on later.
    Last edited by tician; 03-07-2014 at 11:52 PM. Reason: somehow managed to write PR1 instead of
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  3. Re: New Rover Project Bulit on ER-1 Platform

    Wow. Thanks so much for the reply. Its gonna take me a while to digest all that Based on that i think i will go with ROS on the laptop (for now at least). First step will be to get it installed and start learning. I will start researching motors too. Thanks again! Any other feedback and advice is very much welcomed!

  4. #4
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    Re: New Rover Project Bulit on ER-1 Platform

    One thing to note here: if you want to leverage the ROS navigation stack (the off-the-shelf software that pretty much can handle driving from point to point collision free), you should really read the tutorials for that software before buying/designing the robot. There are certain assumptions involved in the navigation stack:
    • For localization, the system needs a horizontal laser scan -- you can create this with a kinect (it's not as good as having a laser on the base, but it is a whole lot cheaper, and in a typical home it can work pretty well). Note that you somewhat want this near the floor (note the height this sensor is mounted on the TurtleBot).
    • The local planner and localization require odometry from the robot base
    If you are looking to minimize the effort to get up and running, I would really recommend a modern x86 processor - you can then use prebuilt binaries of ROS (if you go the ARM route, you will probably have to build quite a bit of the software, and not everything even builds on ARM yet). Intel NUC, or a small i3-based laptop would be a good choice. The choice between laptop/headless-computer really comes down to preference and skill. If you're a network ninja and can easily administer the robot with a headless computer, it will reduce the amount of stuff the robot carries around (screen, keyboard, etc). On the other hand, it can make it easy to just pop the laptop open, and start typing/clicking to figure out what is wrong with the robot.

    -Fergs

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