Prepared by: Curtis J. Ostrander Dept. of Electrical and Computer Engineering

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: A Helicopter as an Actuator Prepared by: Curtis J. Ostrander Dept. of Electrical and Computer Engineering Utah State University E: cjostrander@cc.usu.edu; T: (435)797-; F: (435)797-3054 (ECE Dept.) W: http:// 3/7/2008

2. Outline • Reference list • To probe further • Major applications • Basic working principle illustrated • Controlling a Helicopter • Major specifications • Limitations • And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • http://en.wikipedia.org/wiki/Helicopter • http://en.wikipedia.org/wiki/Radio-controlled_helicopter • http://www.rcheliwiki.com/ • http://www.start-flying.com/new%20site/heli1.htm • http://wiki.answers.com/Q/How_does_a_helicopter_fly • http://www.rc-airplane-world.com/how-helicopters-fly.html • http://www.thaitechnics.com/helicopter/heli_intro.html • http://www.experiencefestival.com/a/Helicopter_-_Limitations/id/1292198 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To explore further (survival pointers of web references etc) • To explore general helicopter information refer to http://en.wikipedia.org/wiki/Helicopter • To learn how helicopters fly, refer to http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Major applications • Military Applications – Most branches of any nations armed forces employs helicopters. • Fire Fighting – Helicopters are employed to drop water or flame retardant. • Search and Rescue – Helicopters provide a stable air platform with which to support search and rescue operations. • Air Ambulance – A helicopter’s ability to land in small areas allow use as a fast medevac vehicle. • Construction – Large helicopters are able to lift large payloads and move them from one location to another. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Basic Working Principle • A typical drive train of a helicopter consists of an engine supplying power, a main rotor for lift, a tail rotor for torque compensation, and gearboxes to translate the engine power to the main rotor and tail rotor. Image copied from http://www.start-flying.com/new%20site/heli1.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Basic Working Principle (Continued) A helicopter is a rotary wing aircraft, where the wing of the aircraft is the rotor blade. A helicopter raises in the air using lift via the equation Where CL is the Lift Coefficient, d is the density of air, V is the velocity of air, and A is the wing area. Image copied from http://en.wikipedia.org/wiki/Helicopter_rotor ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Basic Working Principle (Continued) In understanding lift, it is important to understand Pitch. In a helicopter, the amount of lift is generated by the angle of the rotor blade, or pitch angle, and the speed of the rotor blade. Increasing the pitch angle causes an increased angle of “attack”, thereby increasing the airflow under the rotor blade causing an increase in lift. Image copied from http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Basic Working Principle (Continued) Since the rotor is spinning, there is a tendency for the body of the helicopter to rotate in the opposite direction the rotor is spinning. The tail rotor provides the anti-torque device needed to correct this tendency. Image copied from http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Controlling a Helicopter Once airborne a helicopter needs to be controlled. Helicopters have four controls: Throttle, Rotational (Yaw), Collective, and Cyclic. Image copied from http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Controlling a Helicopter (Continued) Controlling these four items are accomplished by use of the cyclic stick, tail rotor pedals, and the collective lever. The collective lever also contains the throttle control. Image copied from http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. Controlling a Helicopter (Continued) To move the helicopter up or down, the Collective is used to control the pitch angle of the rotor blades. This is accomplished using a swash plate to control all the rotor blades simultaneously. Raising the collective will cause the helicopter to lift, while lowering the collective will cause the helicopter to drop. Image copied from http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Controlling a Helicopter (Continued) The cyclic control allows the pilot to move the helicopter right, left, forward, backward, or hover. This is done by changing the pitch on individual rotor blades via the swash plate. Tilting the swash plate changes the pitch on individual blades as shown. Image copied from http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Controlling a Helicopter (Continued) When hovering or in motion, the helicopter can be made to turn using the foot pedals. When hovering, the foot pedals change the pitch of the tail rotor causing the helicopter to pivot or rotate. When the helicopter is in motion, changing the pitch of the tail rotor acts as a rudder causing the helicopter to turn. Image copied from http://www.rc-airplane-world.com/how-helicopters-fly.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Controlling a Helicopter (Continued) The last control of a helicopter is the throttle control. Unlike fixed wing aircraft, the engine speed of a helicopter does not need to be adjusted. Constant engine speed (RPM) is maintained during normal flight. However, yaw control is directly related to engine speed or power. At a higher rate of engine speed, more torque is generated requiring more yaw control. The throttle is a ‘twist-grip’ on the end of the collective lever. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Major Specifications • Main Rotor Length – This specification directly affects the helicopter’s lift ability. • Tail Rotor Length – This specification directly affects the helicopter’s rotational stability. • Engine – This specification affects the helicopter’s lift ability and cruising speed. • Maximum Gross Weight – The maximum weight of the helicopter plus payload (passengers, fuel, cargo, etc.) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Limitations • The most noticeable limitation of the helicopter is its slow speed. In motion, the ‘advancing’ rotor blade is travelling faster than the ‘retreating’ rotor blade. This causes a dissymmetry of lift. Exceeding the maximum designed velocity rating will cause the helicopter to travel faster than the ‘retreating’ rotor blade, causing the rotor to stall. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Limitations (Continued) • Noise - Helicopters are inherently noisy. The engine noise and the vibration of the rotor blades as they move through air turbulence creates noise. This causes complaints if helicopters are in an urban area. • Vibration – An unadjusted helicopter can actual tear itself apart by vibration. Rotor adjustments for height and pitch can reduce vibration. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Helicopter Pricing • Helicopters are an expensive investment. The cost of the helicopter can range from $290,000.00 to $5,300,000.00 for used helicopters. See www.Controller.com for examples. • Fuel costs are over $5.00 per gallon and fluctuate with the economy. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Helicopter Pricing (RC variety) Radio Controlled Helicopter prices are somewhat cheaper than your standard Bell Turbine Helicopter. • RC Helicopters range from $20.00 for micro indoor helicopters to $900.00 for 500 Series kits.refer to http://www.xheli.com for examples. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

21. Conclusion Helicopter controls are difficult at best. There is a phrase that aptly describes helicopter control – “You don’t fly a helicopter, you just stop it from crashing”! (author unknown) As an actuator, a helicopter is unique in that it has six degrees of freedom. There are three degrees of rotational freedom (Yaw, Pitch, and Roll) and three degrees of linear freedom (X, Y, and Z). This makes sensor measurements interesting. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators