Research ArticleBIOMIMETICS

AntBot: A six-legged walking robot able to home like desert ants in outdoor environments

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Science Robotics  13 Feb 2019:
Vol. 4, Issue 27, eaau0307
DOI: 10.1126/scirobotics.aau0307
  • Fig. 1 Homing trajectories of the desert ant Cataglyphis and the AntBot hexapod robot.

    (A) Path integration in the desert ant C. fortis. After a random-like outbound trajectory (thin line, 592.1 m long), the forager went straight back to its nest (thick line, 140.5 m long). The open circle marks the nest entrance, and the large filled one shows the feeding location. Small filled dots represent time marks (every 60 s). Adapted from (10) by permission of Taylor & Francis. (B) AntBot’s homing performances inspired by experiments on Cataglyphis desert ants in (A). After a 10-checkpoint outbound trajectory (gray line, 10.6 m long), AntBot went back to its starting point (gray cross) just like desert ants (black line, 3.2 m long). Solid points denote the checkpoints where AntBot stopped to determine its heading.

  • Fig. 2 Hardware used in the hexapod robot AntBot.

    (A) Structure of the robot with its sensors and electronic parts. (B) Hardware architecture of the AntBot robotic platform. To deal with the communications between the Raspberry Pi 2B board and the other electronic devices [the celestial compass, IMU (MinIMU-9 v3), M2APix OF sensor, and stepper motor], we developed a custom-made shield. (C) Side view and (D) top view of AntBot.

  • Fig. 3 The celestial compass.

    (A) 3D diagram of the pattern of polarization in the sky relative to the AntBot robot observer (O), at a given elevation of the Sun. The gray curves give the AoP all around the dome of the sky. The minimum DoLP occurs in the region of the Sun, and the maximum DoLP occurs 90° from the Sun (red curve). (B) Computer-aided design view of the celestial compass. (C) Photograph of the celestial compass. On the left, the top gear has been removed to show the UV light sensor and the Hall-effect sensor used to stop the sky scanning process after one full gear rotation. (D) An example of normalized raw (thin lines) and filtered (thick lines) signals UV0 (in blue) and UV1 (in red) during a sunny day in April 2017 in Marseille, France. (E) Raw (thin line) and filtered (thick line) log-ratio signals between UV0 and UV1. The AoP is located at the minimum values of the log-ratio output (here, the AoP is 118° and mod is 180°).

  • Fig. 4 AntBot’s ventral OF sensor.

    (A) The M2APix silicon retina. Adapted from (66). The OF sensor is composed of 12 Michaelis-Menten pixels. (B) Photograph of the M2APix OF sensor embedded onboard AntBot. The sensor (a) is connected to a Teensy 3.2 microcontroller (b) and topped with a Raspberry Pi NoIR defocused lens (c). (C) Schematic view of the 12 hexagonal Michaelis-Menten pixels, divided into two rows of 6 pixels. (D) Optic geometry of a local motion sensor: two adjacent pixels in a row, showing visual signal acquisition of a moving contrast, depending on the inter-pixel angle ∆ϕ between two adjacent pixels and the acceptance angle ∆ρ corresponding to the width of the Gaussian angular sensitivity of each pixel at half-height. (E) Example of raw signals generated by a black/white moving edge. The colors correspond to those used in (C). The time lag between two adjacent pixels (∆t) is computed using cross-correlation methods.

  • Fig. 5 Homing performances on a five-checkpoint trajectory.

    (A to E) Homing results on the five-checkpoint trajectory based on the PI mode. The trajectory was repeated 20 times. Blue lines give the outbound trajectory, and red lines give the homeward trajectory. The black cross symbolizes the home location, and the green cross is the average position of AntBot after homing. (F) Box and violin plots of the homing error as a percentage of the entire journey in each PI mode. Violin plots show the probability density corresponding to each error value.

  • Fig. 6 AntBot’s homing performances in five different five-checkpoint trajectories.

    (A to E) The five trajectories tested. Outbound trajectories are presented in thin lines, and homeward trajectories are presented in thick lines. (F) Box and violin plots of the five trajectories in all the PI modes tested. Violin plots show the probability density corresponding to each error value with each of the PI methods tested.

  • Fig. 7 AntBot’s homing performances involving a long trajectory.

    The black cross gives the starting point; the red crosses give the homing result in each of the PI modes tested. Outbound trajectories are presented in thin lines, and homeward trajectories are presented in thick lines.

  • Fig. 8 Homing performances of AntBot.

    (A) Homing success rate based on the homing success criterion defined as a fraction of the robot’s diameter (L). The criterion used in this study was L/2. (B) Homing errors as a percentage of the entire trajectory, depending on the PI modes described in Figs. 5 and 6. The mean errors and SDs were based on all the results obtained in the 26 experiments.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/4/27/eaau0307/DC1

    Text S1. The celestial compass

    Text S2. The robot’s odometer

    Text S3. The PI process

    Fig. S1. AntBot, an ant-inspired hexapod robot.

    Fig. S2. Exploded computer-aided design view of the UV-polarized light compass.

    Fig. S3. Characterization of the angular aperture of the celestial compass.

    Fig. S4. Noise measured in each POL-unit in the absence of UV-polarized light.

    Fig. S5. Effects of variable sky on the output of the celestial compass.

    Fig. S6. Characterization of the celestial compass.

    Fig. S7. Solar-based solution to the heading angle ambiguity.

    Fig. S8. Characterization of the M2APix OF sensor.

    Fig. S9. Photograph of the experimental setup.

    Fig. S10. Photographs of the textured panels.

    Fig. S11. Graph of the homing path.

    Fig. S12. AntBot’s walking drift analysis.

    Table S1. Walking parameters of the hexapod robot AntBot.

    Table S2. Empiric gain β used in the outdoor experiments.

    Table S3. Results obtained in the PI-ST mode.

    Table S4. Results obtained in the PI-OF-ST mode.

    Table S5. Results obtained in the PI-ST-FUSE mode.

    Table S6. Results obtained in the PI-POL-ST mode.

    Table S7. Results obtained in the PI-Full mode.

    Movie S1 (.mp4 format). AntBot’s homing performances in the PI-ST mode.

    Movie S2 (.mp4 format). AntBot’s homing performances in the PI-OF-ST mode.

    Movie S3 (.mp4 format). AntBot’s homing performances in the PI-ST-FUSE mode.

    Movie S4 (.mp4 format). AntBot’s homing performances in the PI-POL-ST mode.

    Movie S5 (.mp4 format). AntBot’s homing performances in the PI-Full mode.

  • Supplementary Materials

    The PDF file includes:

    • Text S1. The celestial compass
    • Text S2. The robot’s odometer
    • Text S3. The PI process
    • Fig. S1. AntBot, an ant-inspired hexapod robot.
    • Fig. S2. Exploded computer-aided design view of the UV-polarized light compass.
    • Fig. S3. Characterization of the angular aperture of the celestial compass.
    • Fig. S4. Noise measured in each POL-unit in the absence of UV-polarized light.
    • Fig. S5. Effects of variable sky on the output of the celestial compass.
    • Fig. S6. Characterization of the celestial compass.
    • Fig. S7. Solar-based solution to the heading angle ambiguity.
    • Fig. S8. Characterization of the M2APix OF sensor.
    • Fig. S9. Photograph of the experimental setup.
    • Fig. S10. Photographs of the textured panels.
    • Fig. S11. Graph of the homing path.
    • Fig. S12. AntBot’s walking drift analysis.
    • Table S1. Walking parameters of the hexapod robot AntBot.
    • Table S2. Empiric gain β used in the outdoor experiments.
    • Table S3. Results obtained in the PI-ST mode.
    • Table S4. Results obtained in the PI-OF-ST mode.
    • Table S5. Results obtained in the PI-ST-FUSE mode.
    • Table S6. Results obtained in the PI-POL-ST mode.
    • Table S7. Results obtained in the PI-Full mode.
    • Legends for movies S1 to S5

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). AntBot’s homing performances in the PI-ST mode.
    • Movie S2 (.mp4 format). AntBot’s homing performances in the PI-OF-ST mode.
    • Movie S3 (.mp4 format). AntBot’s homing performances in the PI-ST-FUSE mode.
    • Movie S4 (.mp4 format). AntBot’s homing performances in the PI-POL-ST mode.
    • Movie S5 (.mp4 format). AntBot’s homing performances in the PI-Full mode.

    Files in this Data Supplement:

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