Rotary Wing Micro Air Vehicle Endurance Klaus-Peter Neitzke

1. Rotary Wing Micro Air Vehicle Endurance Klaus-Peter Neitzke University of Applied Science Nordhausen Nordhausen, Germany IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

2. Index • Motivation • Quadrocopter ‚Ninja‘ and ‚Wanze‘ • Battery • Propeller • Possible flight time • Optimal battery mass • Selection of the battery • Conclusion IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

3. Motivation One of the first questions to pilots of rotor based electric MAV‘s is the possible flight time of the system. The answer is not easy sometimes. This presentation provides an answer based on theoretical investigations and peformed flight tests. The author in the year 1991 IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

4. Quadrocopter ‚Ninja‘ and ‚Wanze‘ D = 200 mm D = 100 mm The vehicles were used during IMAV 2011 and IMAV 2012. The ‚Ninja‘ dimension is two times the ‚Wanze‘ dimension. They are very similar from the technical point of view. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

5. Battery Lithium polimer (LiPo) batteries were used presently. The main parameters are mass and specific power of the battery. To have an impression of the energy content of a LiPo batteriy we can do a thought experiment. The energy content can be used to lift the battery only. Example: Thought experiment IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

6. Battery Relation between the mass (m) and the energy content (E) of the battery. Example: A battery with 3 cells and a capacity of 10 Ah will have a mass of 0.9 kg. Overview on several LiPo batteries For further calculations we suppose an average specific power (D) of the battery of 444 kJ/kg. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

7. Propeller Equation to calculate the necessary power for the hover flight. The necessary power is a function of the mass of the vehicle, the acceleration of gravity, the density of the air and the rotor area. Bla bla The induced flow velocity near to the propeller plane Induced velocity IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

8. Possible flight time The flight time (T) can be calculated by the energy content (E) and the necessary power (P), see equation: Now we have an equation for the flight time (T). IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

9. Possible flight time Comparison to flight tests. The results fits well if we consider an efficiency factor for the ‚Ninja‘ of 0.35. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

10. Possible flight time Comparison to flight tests. The results fits well if we consider an efficiency factor for the ‚Wanze‘ of 0.19. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

11. Optimal battery mass Is there an optimum for the battery mass in the equation? Yes, there is... The flight time has the maximal value when the battery mass is twice as high then the empty air vehicle mass. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

12. Selection of the battery Mission A: Hobby flights without special needs A small battery is a good selection (costs, crash mass, mechanical loading). The battery mass should be 50% of the mass of the empty air vehicle. (‚Ninja‘: 1.5 Ah - 16 min. ‚Wanze‘: 0.8 Ah - 9 min.) Mission B: Pylon races or speed / climb competitions There we need power and a low mass of the air vehicle. The best solution is the smallest battery, who is able to fulfil the mission. Maybe the necessary flight time is 1 to 2 minutes only. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

13. Selection of the battery Mission C: Fly the maximum possible time The battery mass should be 200% of the empty air vehicle mass. With a 100% battery the flight time is 92% of this maximum. (‚Ninja‘: 8 Ah - 30 min. ‚Wanze‘: 2 Ah - 14 min.) Mission D: Stable flights under windy conditions There we need a higer mass of the quadrocopter. With a high mass of the air vehicle we reach a high induced flow velocity near to the rotor plane. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

14. Induced flow at the propeller blade If there is an additional gust based on the weather turbulence, then there is a change of the incoming flow at the propeller blade. The change in the angle of attack is bigger for lower velocities, see figure. A high induced flow velocity is a good basis for stable flights. It can be used a mass higher than for mission C (200% of the empty air vehicle). The flight time will be smaller. But the flight will be more stable. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

15. Conclusion • To reach long flight times there is the need to select all components of the air vehicle carefully. • For long flight times the battery mass should be 200% of the empty air vehicle mass. • For different flight mission there is the recommendation to use different batteries. IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance

16. my new flight area my new office Thank you for your attention. Contact: neitzke@fh-nordhausen.de IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance