Quadcopter? Nope, Grabcopter!

It’s been a while since I built my quadcopter… nearly 2 years actually (December 2015 to December 2017). It has been great fun flying it, there are times when I took it over 120 feet into the air! I also broke my share of propellers along the way, but hey, that’s all part of the hobby! 🙂

I just bought a new “Orange LiPo” battery for it, from Robu.in (3000 mAh, 30C/40C), because I accidentally left one of my Turnigy LiPos fully charged for over 3 months (NEVER EVER DO THIS) – it increases the internal resistance of the battery and reduces the C rate down to 2C or less. I took the drone out for a couple of flights, and the new battery is splendid so far.

This year, Shaastra, IITM’s technical festival, has an event sponsored by Amazon called the Amazon AWS Drone Delivery Challenge. The problem statement involves picking up a package (weights of about 100 gm) of a given color, and then moving it to a pre-specified location. I thought it would be cool to have a fully robotic solution to this, so I began thinking of how I could automate this.

I attached an external micro controller (the ESP8266, which is actually a MCU with a full TCP/IP stack for WiFi connectivity) and used a color sensor for detecting the color of the parcel. For pick-up and drop, I thought of using a simple hook (like a clothes hanger), but for some reason, it seemed too simplistic and archaic. So I decided to use a robotic gripper, which could rotate from the horizontal position and then grab objects using a claw. I found a fantastic 2-DOF robotic arm assembly on Robu.in (again). It looks like this:

One of the servos will rotate the arm into position, and the second servo is used to actuate the claw. It looks really impressive when mounted and works as expected! I also connected the control inputs to the servos to the receiver input from my quadcopter remote control, so that I can control the gripper when the quadcopter is in the air! Here’s a short video of the robotic gripper mounted on the quadcopter:

It has become more difficult to get the quadcopter flying due to the extra weight, but my excellent Turnigy motors are able to handle it! It takes time to get the hang of it, flicking the switch to get the arm into position at the right time while keeping the quadcopter level and hovering over the package… but practicing is fun!


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