Rotary Wing Micro Air Vehicle Endurance
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Rotary Wing Micro Air Vehicle Endurance Klaus-Peter Neitzke University of Applied Science Nordhausen Nordhausen, Germany. Index. Motivation Quadrocopter ‚Ninja‘ and ‚Wanze‘ Battery Propeller Possible flight time Optimal battery mass Selection of the battery Conclusion.

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Rotary wing micro air vehicle endurance klaus peter neitzke

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


Index

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


Motivation

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


Quadrocopter ninja and wanze

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


Battery

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


Battery1

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


Propeller

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


Possible flight time

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


Possible flight time1

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


Possible flight time2

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


Optimal battery mass

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


Selection of the battery

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


Selection of the battery1

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


Induced flow at the propeller blade

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


Conclusion

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


Rotary wing micro air vehicle endurance klaus peter neitzke

my new flight area

my new office

Thank you for your attention.

Contact: [email protected]

IMAV 2013: K.-P.Neitzke: Rotary Wing Micro Air Vehicle Endurance


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