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Thread: Adding Sharp GP2D12 sensors to robot platform

  1. Adding Sharp GP2D12 sensors to robot platform

    I have a robot platform(MMP8) that is run with JAVA thru a wireless link to a Lantronix WBX2100. I need to add in obstacle avoidance for forward and rear movement. Once a object is detected in the range that movement direction is halted and only the opposite movement is allowed until the object is out of range. I have considered the Arduino Diecimila with the Sharp GP2D12 sensors to accompish this. Is this a good setup or is there a better option? Any suggestions on this?

    Robot hardware,
    MMP8 6 wheel platform
    Lantronix WBX2100 wireless access
    Super Logics CP8200, A/D converter
    Servo8 board
    Dlink DCS-6620G camera
    Relays to control voltages to charging pads on bottom of platform( controlled from relay in Dlink camera). Docking/charging station, self design
    Last edited by cross1933; 03-26-2009 at 10:57 AM.

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    Re: Adding Sharp GP2D12 sensors to robot platform

    Wow that's an expensive setup! If you are going to connect the arduino to the Lantronix box then you will probably need an RS-232 to TTL converter. The arduino only accepts TTL level data on it's serial line if you aren't using the USB.

    The sharp sensors will work fine but with a machine that size you may want to consider adding sonar as well. If the sharp sensor misses a toddler wearing an all black ninja outfit you don't want to run him over and upset the toddler ninjas.
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    Re: Adding Sharp GP2D12 sensors to robot platform

    Quote Originally Posted by jes1510 View Post
    The sharp sensors will work fine but with a machine that size you may want to consider adding sonar as well. If the sharp sensor misses a toddler wearing an all black ninja outfit you don't want to run him over and upset the toddler ninjas.
    Second what jes said. The IR rangers have a very narrow field of view, probably about 2-5 degrees wide. Most sonar sensors have a cone of detection that is 30-40 degrees wide. There is also the issue of what each sensor type will pick up... the IR sensors may wash out in the sun, or not detect a highly shiny surface, they also have limited range. Sonar on the other hand, has a much longer range, but may not detect objects that are acoustically challenging (unfortunately, baggy or thick clothing often falls in this category).

    That said, you'll often hear me, jes, and adrenalynn yelling "One sensor is not enough!" and "One type of sensors is not enough!". It's especially true for bigger bots. I would use, at a minimum, a sonar, and several IR facing forward. I would also recommend some sort of a bumper, as a last resort... I always tell myself that my bots don't need bumpers, but eventually end up installing one, because even though you wont need it often, knowing that you are pushing a baby across the floor and are about to smush it against a wall is pretty important...

    -Fergs

  4. Re: Adding Sharp GP2D12 sensors to robot platform

    Quote Originally Posted by jes1510 View Post
    Wow that's an expensive setup! If you are going to connect the arduino to the Lantronix box then you will probably need an RS-232 to TTL converter. The arduino only accepts TTL level data on it's serial line if you aren't using the USB.

    The sharp sensors will work fine but with a machine that size you may want to consider adding sonar as well. If the sharp sensor misses a toddler wearing an all black ninja outfit you don't want to run him over and upset the toddler ninjas.
    Not sure about the cost, a coworker gave me the parts. The coworker had some units completed and wanted to get rid of some parts. The completed units were too large for my area of useage so I opted to assemble this one. The robot works well, the object avoidance is the only thing remaining.

    My idea was to add the arduino after the output from the servo8 board, then connect the output of the arduino to the PWm board in the MMP8 base. In essence add the arduino board between the servo8 board and the pwm board in the base. Input the sensor readbacks into the arduino board for position location. Once a set postion is reached stop movement in that direction. I plan on adding the outputs from the sensor to the JAVA control page. I have added readback from the logic and motor batteries to the Java console page

    I could add something into the JAVA control thru the a/d converter. The problem with this is when the wirless signal is lost the stop command is lost. I need to be able to stop the robot with wireless signal and without wireless signal.

    I should have given more detail on its usage. The usage will be to check for possible problems in a underground tunnel. The main issues of detection will be water leaks. The tunnel housed a particle accelerator which uses water cooling for magnets. We do have issues with ground water leaks after large rains. I have upgraded the antennas to increase maximum coverage, the final test will be running the robot.

    Any recommendations on a sonar sensor?

  5. Re: Adding Sharp GP2D12 sensors to robot platform

    Quote Originally Posted by lnxfergy View Post
    Second what jes said. The IR rangers have a very narrow field of view, probably about 2-5 degrees wide. Most sonar sensors have a cone of detection that is 30-40 degrees wide. There is also the issue of what each sensor type will pick up... the IR sensors may wash out in the sun, or not detect a highly shiny surface, they also have limited range. Sonar on the other hand, has a much longer range, but may not detect objects that are acoustically challenging (unfortunately, baggy or thick clothing often falls in this category).

    That said, you'll often hear me, jes, and adrenalynn yelling "One sensor is not enough!" and "One type of sensors is not enough!". It's especially true for bigger bots. I would use, at a minimum, a sonar, and several IR facing forward. I would also recommend some sort of a bumper, as a last resort... I always tell myself that my bots don't need bumpers, but eventually end up installing one, because even though you wont need it often, knowing that you are pushing a baby across the floor and are about to smush it against a wall is pretty important...

    -Fergs
    A majority of objects to avoid will be of some form of metal.The range I am concerned about is detecting a object from 1' to 3'. The sharp sensor starts detection at 4" from the sensor. My goal is to stop the making contact with a object, that could be a bad thing. For the most part the center of the tunnel is open with plus and minus 5' on each side. There is one area where the beam pipe crosses over the center at 3' above the ground. There is ample clearance on both sides to safely navigate under the pipe. As I stated above the main concern is if the wireless signal is lost the robot can go wandering.

    I had considered two forward and rear facing sensors angled slightly off center in opposite directions. My concern her is interference between the two sensors affecting the read back. The idea of bumpers is still a consideration and probably will happen, I can only control how I drive the robot. Maybe I need to issue drivers licenses for people who wish to use this?

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    Re: Adding Sharp GP2D12 sensors to robot platform

    Quote Originally Posted by cross1933 View Post
    My idea was to add the arduino after the output from the servo8 board, then connect the output of the arduino to the PWm board in the MMP8 base. In essence add the arduino board between the servo8 board and the pwm board in the base. Input the sensor readbacks into the arduino board for position location. Once a set postion is reached stop movement in that direction. I plan on adding the outputs from the sensor to the JAVA control page. I have added readback from the logic and motor batteries to the Java console page
    I'm fuzzy on what the servo8 is for in this case.
    "If A is a success in life, then A equals x plus y plus z. Work is x; y is play; and z is keeping your mouth shut."
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  7. Re: Adding Sharp GP2D12 sensors to robot platform

    If the majority of the objects you are avoiding are metal, I would caution against IR sensors. I have had very spotty results with them on reflective surfaces. Unless you hit the correct angle of reflection, the reflective surface is near invisible. You are probably best of using a bumper, or if physical contact is truly taboo, then a Sonar sensor is your best bet.

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    Re: Adding Sharp GP2D12 sensors to robot platform

    I'm just going to reiterate, since Fergs invoked me and the response:

    Never trust one type of sensor.

    It's gonna happen. It always happens. In 115% of the samples with an n= of infinity. Whatever sensor you pick won't detect the one thing you least want to smash into at 10+mph with a throttle stuck wide open and an emergency cut switch stuck closed.
    I Void Warranties´┐Ż

  9. Re: Adding Sharp GP2D12 sensors to robot platform

    Quote Originally Posted by jes1510 View Post
    I'm fuzzy on what the servo8 is for in this case.
    A chain of 8 pulses comes in (serial link)and the servo board sends out one pulse to each of the 8 outputs, ability to control 8 motors. In this case only two of the outputs are used, previous model used more for a arm. The pulses are then sent to the driver card in the base of the platform.

  10. Re: Adding Sharp GP2D12 sensors to robot platform

    Quote Originally Posted by WGhost9 View Post
    If the majority of the objects you are avoiding are metal, I would caution against IR sensors. I have had very spotty results with them on reflective surfaces. Unless you hit the correct angle of reflection, the reflective surface is near invisible. You are probably best of using a bumper, or if physical contact is truly taboo, then a Sonar sensor is your best bet.
    Bumping into one of the magnet power connections would be a big problem. An opinions on a sensor,http://www.trossenrobotics.com/store...ar&submit=true.Or do you know of different brand that you prefer?

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