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Head and leg adjustments help insects and legged robots traverse cluttered, large obstacles
Department of Mechanical Engineering, Johns Hopkins University [email protected] https://li.me.jhu.edu
Wang, Othayoth, Li, J. Exp. Biol., in prep.
1. Background & Motivation
Animals integrate active sensory feedback and passive mechanical feedback to control locomotion
Potential energy landscape
Physical interaction (energy landscape) plays a major role during obstacle traversal
Model system Locomotor transition pathways
Transition barrier
Othayoth et al. (in press), PNAS
Dickinson et al. (2000), Science
Saddle
Awareness of landscapehelps find a lower barrier
Hypothesis: Cockroaches actively adjust body and appendages to overcome barrier and make transition
2. Experimental Observations
Leg sprawl
Head Bending
Pushing Leg Height
Supporting Leg Height
0
5
10
15
0
5
10
15
0
50
100
Leg sprawl angle (⁰) s.d. of head flexion (⁰)Leg height difference (mm)
Difference
*** *** ******
Frequent head flexionLeg sprawl Differential leg use
Run Push Roll
Beam obstacle traversal can be divided into three phases
Cockroaches actively adjust their head and legs to make locomotor transition
Beam obstacle layer
Cameras(100 fps)
3-D kinematics tracking setup
Reduces roll stability Generates roll torque Sense terrain (?)
Run Push Roll
0.30s 0.43s 1.06s 1.29s 1.97s 3.13s 3.44s
Tags
Beads
Beads
N = 8 animals, n = 64 trials
P < 0.05 ANOVA
P < 0.05 ANOVA
P < 0.05 ANOVA
Run Push RollRun Push Roll
Pitch
Saddle
Body roll (°)
`Body pitch (°)
`
>0.54
Energy(mJ)
50
-50
Roll
-50
-50
0
0.4
0.52
0.462
0
3. Energy Landscape ModelingEnergy landscape approach to understand physics of locomotor transitions
Proper head adjustment reduces energy barrier on landscape
Body pitch (º)
−80
−40
0
40−70
0
70
Body roll (º)
0
25
0
50Start
1
Start
Transition barriers
Roll
Start
1
Roll
Pitch Pitch
3
Energy (mJ)
iiiiii
Beams
Start
Pitch
Pitch
Start Start
Roll
Vertical vibration
3−80º
0
40−70
0
70
3
3
1
Start
i ii iii iii’
17
7
Energy (mJ)
11
8
Energy (mJ)
0
20
2
−80
−40
0
40−70
0
70
Barrier without head adjustment
Pitch
Roll
Saddle
Energy barrier comparison
Othayoth et al. (in press), PNAS
0
300
600
−40 −20 0 20 40
Traversalbarrier
(µJ)
x (mm)
Roll more favorable
K = 11.44 mN·m/rad
− Roll− Pitch
Body roll (º)
−90
0
9090
0 −90
Body pitch (º)
Potential energy (µJ)2.5
×104
2
1.5
1
0.5
With head bending(measured head angle)
Representative barrier profileHead adjustment lowers barrier
3-D reconstruction
Pitch
Saddle
Body roll (°)
`Body pitch (°)
`
>0.54
Energy(mJ)
50
-50
Roll
-50
-50
0
0.4
0.52
0.462
0
Without head bending(constant head angle)
Body roll (°)0 20 40 60 80
Barrier with head adjustment
Energy(mJ)
0.38
0.5
0.4
0.42
0.44
0.46
0.48
0 0.5 1 1.5 2 2.5Time (s)
0
0.1
0.2
0.3
0.4
No head bendingWith head bending
Barrier energy(mJ)
Start rolling Roll to max
Time (s)0 0.5 1 1.5 2 2.5
0
0.1
0.2
0.3
0.4
0 10 20 30 40 50 60
Trial NO.
-0.08
-0.06
-0.04
-0.02
0
0.02 Barrier is smaller with head bending than without
(mean change < 0)
(P < 0.05, ANOVA)
0.02
0
-0.02
-0.04
-0.06
-0.08
Change in energy barrier(mJ)
0 10 20 30 40 50 60
Trial No.
4. Robophysical Model & Future Work
Next steps
Beams
Retract Left Leg
Extend Right Leg
Head bending
Sprawlinward
Gap = 57% Body WidthInitial Pitch = 45°
Legged robot to systematically control and vary active adjustment of head and legsHead flexionLeg sprawl Differential leg useLegged robot
Preliminary result: all the three adjustments help the robot roll into the gap
Low cost 3-axis force sensor(designed by J. Krakauer’s group)
Y
Z
X
Embedded sensors at the neckRobot with force sensors
Force measurements to understand:• Relationship between contact forces and
potential energy landscape (slope?)• Transitions on landscape emerging from local
force sensing
Acknowledgements:Yuanfeng Han and Qiyuan Fu for help with imaging setup;Yuanfeng Han, Qiyuan Fu, QihanXuan and Xiao Yu for discussion;Xiao Yu for help with animal care.
5 trials5 trials5 trials
11
Yaqing Wang, Ratan Othayoth, Chen Li