Twin Copter

Team- Scorpion Karthik Shenoy Sushant Khade Sachin Sharma Darshan Bang

Team Mentor Varun Sudarsanan

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Initial Idea Aim of this project is to build a VTOL twin prop helicopter, inspired by avatar scorpion gunship. We have done some ground work for the same. We plan to mount 2 brushless motors on a boom and tilt them independently, using servos with help of front wheel steering arm. The brushless motors and servos will be mounted on aluminum channel to make the structure sturdy. The remaining fuselage will be made from foams. The expected weight of the model is around 800gms. The team members have done a workshop on quad-rotor. We are familiar with the quad-rotor systems and will try to implement them on the twin copter. We also have components of the quad-rotor available with us and will use whichever possible. The KK control board and programmer of the quad-copter has inbuilt autopilot, IMU and has 6 channels. The control board is compatible with the twin-rotor design as per our groundwork. The main components needed would be 2 brushless motors with propellers, 2 Electronic Speed controllers, 2 3.8kgcm toque servos available on hobby-king, front wheel steering arm and batteries. We will be ordering the components from hobby-king as soon as possible after consulting the mentors about the specifications. We are planning to take up the project in the second phase of ITSP.

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Aim of this project is to build a VTOL twin prop helicopter

Introduction

It is an aircraft which generates lift and propulsion by way of one or more powered rotors (sometimes called  proprotors) mounted on rotating engine pods or nacelles usually at the ends of a fixed wing.

Theory

Roll

Roll is the simplest of the axis to control. By simply varying the thrust of either motor, a torque on the aircraft is created causing it to roll.

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Yaw

Yaw is also pretty straight forward. You tilt one motor forwards and the opposing motor backwards. With the motors tilted in opposite directions, part of the thrust of thrust vector creates torque on the aircraft. Pitch

If the motors are tilted a bit, a portion of the thrust turns into lift while another part of the thrust produces a torque on the aircraft, regardless of the motion or orientation of the airframe. Now as the airframe acts as a free body in space, the torque translates into angular acceleration. This is shown in the figure below.

Advantages of tilt-rotor At the expense of a slightly more complicated autopilot and mechanical complexity, a tilt-rotor has half  the motors, ESCs, connectors, propellers, and power as a quad-rotor. Essentially, a cheap tilt-rotor can be significantly cheaper than a comparable quad-rotor.

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Parts 2 x Turnigy 2213 20turn 1050kv 19A Outrunner 

1 x KKmulticontroller SMD v5.5 Blackboard 

2 x Turnigy Multistar 30 Amp Multi-rotor Brushless ESC 2-4S

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2 x Carson Acoms Servo AS-18 MG

1 x ZIPPY Compact 2700mAh 3S 25C Lipo Pack 

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Airframe

The airframe consists of 2 main parts boom and fuselage. The tilt mechanisms are mounted on the boom and the microcontroller is mounted on the fuselage. Aluminum sections and channels were used to construct the airframe to make the structure as light as possible.

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The tilt mechanism is shown in the figure below. The basic idea behind the tilt mechanism is a 4 bar linkage. It is made up of front wheel steering arms and linkage stoppers. This is actuated by the servos which are controlled by the microcontroller. This motion of servos makes pitch and yaw control possible. The battery is moved appropriately to balance the cg of the aircraft.

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The final design and model looks as-

Thank you

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