1 Challenge the future 1 Challenge the future 1 Challenge the future Structural control method research for MAV application Yao Lu Chairman : Prof. Dr. Fred van Keulen Supervisor: Dr. Hans Goosen, Hugo Peters
Jan 01, 2016
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1Challenge the future
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Structural control method research for MAV application
Yao Lu Chairman : Prof. Dr. Fred van KeulenSupervisor: Dr. Hans Goosen, Hugo Peters
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Content
• Introductions• Introduction to the concept of MAV• Introduction to the task
• Structural control methods and actuator screening
• Tests
• Conclusion and recommendation
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Introduction to Micro Air Vehicle(MAV)
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Introduction to the task
• The aim of this thesis is to investigate approaches to modify the structure stiffness
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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
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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
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Content
• Introductions
• Structural control methods and actuator screening
• Tests
• Conclusion and recommendation
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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
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Actuator screening
• Actuators can be grouped into four groups according to different mechanisms
Actuation
Electric field
Electro-Magnetic
Temperature
Magnetic field
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Actuator screening
• The generation of magnetic field requires too much additional weight
2R
r
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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
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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
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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.
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SMA-two-state method mechanism
• The Young’s modulus of SMA material depends on temperature
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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
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• For a simplified model, the stiffness change depends on the Young’s modulus ratio and thickness ratio between beam material and piezo material
Piezo passive stiffness method
bE
aE ah
bh
a
b
h
h a
b
E
E
F
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• The stiffness change is about 20%
Piezo passive stiffness method
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Piezo passive stiffness method
• 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
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Piezo passive stiffness method
• 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.
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Content
• Introductions
• Structural control methods and actuator screening
• Tests
• Conclusion and recommendation
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Experiment set-up
• Static test is performed
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Experiment result
Deformation for open circuit(um)
38.17
Deformation for short circuit(um)
37.63
Stiffness change
1.44%
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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%
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Content
• Introductions
• Structural control methods and actuator screening
• Tests
• Conclusion and recommendation
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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.
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人法地,地法天,天法道,道法自然Nature is a good teacher to human
beings ---Laozi (571-471BC)