1 Challenge the future 1 1 Structural control method research for MAV application Yao Lu Chairman :...

1Challenge the future



Structural control method research for MAV application

Yao Lu Chairman : Prof. Dr. Fred van KeulenSupervisor: Dr. Hans Goosen, Hugo Peters




Content

• Introductions• Introduction to the concept of MAV• Introduction to the task

• Structural control methods and actuator screening

• Tests

• Conclusion and recommendation




Introduction to Micro Air Vehicle(MAV)




Introduction to the task

• The aim of this thesis is to investigate approaches to modify the structure stiffness




Requirement approximation

• The stiffness change requirement is done and it is supposed that the one that can serve more than 1% of stiffness modification

is satisfied

30




Introduction to the task

• It is hardly possible to investigate the problem on the vehicle currently

• The research is based on a simplified model

3

3EIF d

L

3

3EIk

L




Content

• Introductions


• Tests





Collection of stiffness change methods

• Various methods can be used for the beam stiffness change

• Before screening of these methods, actuators should be screened

dE

dI




Actuator screening

• Actuators can be grouped into four groups according to different mechanisms

Actuation

Electric field

Electro-Magnetic

Temperature

Magnetic field




Actuator screening

• The generation of magnetic field requires too much additional weight

2R

r




Actuator screening

• Two groups of actuators are not favored in MAV application for the generation of magnetic field requires too much weight

Actuation

Electric field

Electro-Magnetic

Temperature

Magnetic field




Criteria of methods screening

• Piezoelectric material and Shape-memory-alloy material are representatives of the remained two groups of active materials

• The stiffness change, the energy cost and the control time should be analyzed for each method.

Piezo Piezo Piezo Piezo passive or SMA-two-

state




Piezo passive stiffness method

• The piezo passive stiffness method uses the mechanism that the stiffness of a short circuited piezo is lower than that in open circuit condition

• The stiffness change is obtained by switching between two electrical conditions of electrodes.




SMA-two-state method mechanism

• The Young’s modulus of SMA material depends on temperature




Screening of the methods

• After screening using theoretical work and simulations, the piezo passive method is selected.

Methods Stiffness change

Energy cost

Control time

Schematic figure

Stressing method

Sandwich method

Curving method

SMA-two-state

method

1W 0.1s

Piezo passive stiffness

0W 0s

510

410

310

110

110




• For a simplified model, the stiffness change depends on the Young’s modulus ratio and thickness ratio between beam material and piezo material


bE

aE ah

bh

a

b

h

h a

b

E

E

F




• The stiffness change is about 20%






• However, there are effects that will reduce the effectiveness of this method such as the effect of glue.

2a

g

h

h

2a

g

E

E

bhghah

0.5 1.3





• The effect of this method is greatly reduced, from about 20% to about 4%. Experiments should be done to verify the effectiveness of this method in practice.




Content

• Introductions


• Tests





Experiment set-up

• Static test is performed




Experiment result

Deformation for open circuit(um)

38.17

Deformation for short circuit(um)

37.63

Stiffness change

1.44%




Experiment result

• Limited by piezo patch numbers, limited tests are done

• Tested stiffness change is less than expected

Sample No.

Material Thickness

(mm)

Stiffness change from test

Stiffness change from simulation

1,2,3 Aluminum

0.5,0.8,1.0

4 Brass 0.8 1.44% 4.38%

5 Steel 1.0 0.4% 4.2%




Content

• Introductions


• Tests





Conclusion and recommendation

• It shows that the passive stiffness method can induce more than one percent of stiffness change for certain material.

• For the future research, it is better to use material and manufacturing with more precision.

• The integration of piezo ceramic material to the structural material without glue can be researched.

• Future colleagues may work in the direction to enhance the effectiveness of the passive stiffness method by electronics.




人法地，地法天，天法道，道法自然Nature is a good teacher to human

beings ---Laozi (571-471BC)

1 Challenge the future 1 1 Structural control method research for MAV application Yao Lu Chairman :...

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