Here are the design elements:
- Tracked robot that moves on a variety of ground cover (including sand)
- Ability to raise and lower the metal detector boom for an optimal sensing height over uneven ground (sand dunes)
- Spray paint can triggered by servo to mark ground
- Wheel encoders help determine total distance traveled
- Robot moves in a pre-defined pattern covering a defined area based on the starting point and direction - configurable
- Long boom to keep the metal detector sensor out far enough that it does not pick up the metal or EMF put off by the robot
- Uses a high-end metal detector sensor that allows identification of different types of metals and allows notch filters to ignore non-precious metals like iron
- Robot moves slowly enough to allow for good detection, but also have enough power to climb small hills
- Text Long/Lat of metal detection as well as information about depth, and type of metal to mobile device
- Not waterproof - keep clear of water on beach
After much research, I think I've finally settled on the SuperDroid LT2 Tracked ATR Robot Platform for this project. Other tracked platforms were too small to meet the requirements, This one meets the requirements, but is a bit out of my price range. Now, how do I justify the $3500USD purchase??
I've also decided to use a Linear Actuator that I already own to keep the sensor close to the ground. It's specs: 100mm, 12V, feedback, 29mm/s.
I'm thinking of using a Lidar Lite module detect ground height to give feedback for adjusting the Linear Actuator. I've used the Lidar Lite module on another project and confirmed it works well in direct sunlight (unlike other IR range finders).
I'm thinking of using Carbon Fiber rods for the main horizontal beam. It's strong, light-weight and non-metallic so will not interfere with the metal detector sensor. I'll use a flange to mount a vertical carbon-fiber beam vertically on the robot chassis and attach the Linear Actuator and counter weight behind the pivot point for balance and adjustment.