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Thursday, July 31, 2014

Hovercraft Micro H-shaped Quadcopter (MHQ) build.

Hey guys, JM again! I have a new project, I'm building the Hovercraft MHQ. This project is super cool for several reasons, first this is my first drone, second it is my first RC project period and third the entire chasis is 3d printed from ABS plastic on our Makerbot Replicator. I will be doing a video series following the different steps in the build and will be filming the portion regarding the 3d printing this coming weekend. For now heres a link to the Photo Album!

What is a quadcopter? A quadcopter is an aircraft that uses rotor wings (like a helicopter) to generate lift and thrust. A helicopter has one main rotor that produces both lift and thrust for the entire airframe while the second, smaller, rotor in the rear counteracts the torque generated by the main rotor and also allows for yaw or rudder right and left to steer flight. A quadcopter utilizes multiple rotors, four specifically, to do the same thing. The benefits of having four main rotors developing lift and thrust as opposed to one main rotor is stability! Torque is counteracted by spinning the rotors in opposite directions. Two spin clockwise and 2 spin counterclockwise. The drone pilot operates a radio transmitter with two sticks that correspond to yaw, pitch, roll and throttle. The radiosignal is transmitted to a receiver onboard the drone, the receiver passes the information to the flight controller or (FCS) the FCS has several extremely important functions. The flight controller has an array of sensors, including gyroscopes and a barometer in the case of the Tau Labs Sparky FCS that is being used for this project. Assuming the radio is set to some amount of throttle but otherwise the sticks are in a neutral position the FCS will adjust, in real time, the RPM of each individual motor so that the drone hovers as if it were sitting on top of a tripod. The FCS accomplishes this by sending signals to four Electronic Speed Controllers or ESCs that are each individually attached to a motor. The ESC acts as a flood gate holding back the considerable amount of current in the battery pack. As the ESC receives signals from the FCS it either gives or limits current to the attached motor increasing or decreasing RPM and thus lift. When a stick is moved out of its neutral position to make an adjustment in either pitch, yaw or roll or some combination of the 3 the FCS does some math and creates a difference between the RPM of the four motors. If the pilot wants more roll the difference is across the long axis of the aircraft, if the pilot wants pitch then the difference is along the short axis etc etc. To generate thrust to move forward the aircraft pitches forward, so that instead of lift being directed perpendicular to the ground it is directed at an angle. Costs for small quadcopter drones can vary greatly. The Hovership MHQ as I have it set up will have quite a few neat features including return to home RTH capabilities and waypoint to waypoint GPS navigation, also altitude hold and loiter mode. Additionally the drone will be fitted with FPV or first person video equipment so that it can be flown over long distances by camera. A downside to this build is that battery capacity being what it is flight time will range from 8-20 mins on one battery. Cost for this build to get it off the ground will be approx $300, with the addition of the FPV equipment it will likely be closer to $500-$700. Most of the equipment is modular and interchangeable so that it can be repurposed for other projects later.

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