Rakesh Gosangi PRISM lab Department of Computer Science and Engineering Texas A&M University

1. Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active TouchTony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009. Rakesh Gosangi PRISM lab Department of Computer Science and Engineering Texas A&M University

2. Outline • Introduction • Rat’s vibrissal system • Neural Processing • Whisking Robots • Discussion and Future

3. Introduction • Mammals do a large part of their tactile sensing using vibrissae (whiskers) • Modern robotics fail to match the capabilities of mammals in tactile perception

4. Tactile perception in animals • Alerting stimulus to produce motor response • Perform complex perceptual tasks like • Determine shape, texture, position of objects in 3-D space • Guide motion for nocturnal species like rats and cockroaches Image – common rat (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

5. Tactile perception in animals • Etruscan shrew prey capture is guided by tactile cues • Seals can detect hydrodynamic trails left by fish with their whiskers  Images – water shrew, harbor seal (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

6. Tactile Sensors in robotics • The least trusted sensors • Used as a last line of defense when all the other sensing modalities fail • Passive in nature • Waiting to be deflected by an object

7. Outline • Introduction • Rat’s vibrissal system • Neural Processing • Whisking Robots • Discussion and Future

8. Rat’s vibrissal system • Long facial whiskers called macrovibrissae • Individually actuated and actively controlled by the rats • Shorter, densely packed microvibrissae on chin and lips • Non actuated • Mechanoreceptors in the hair follicles convert direction, velocity, duration and torque of whisker movements into electrophysiological signals

9. Use of macro and micro vibrissae Image – Use of macro and micro vibrissae (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

10. Whisking movements • Macro vibrissae are moved back and forth (whisking) at high speeds (5-25/sec) • The movement of the whiskers is controlled depending on head-body movement, recent sensory experience Image – Whisking control in rat (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009. Movement of whiskers of a head-restrained rat

11. Whisking movements • Whiskers move asymmetrically when the rat turns its head • Rats can control the speed of the individual whiskers • Whiskers have many degrees of freedom • Parallel and perpendicular to the plane of the head • Torsional rotation Image – Asymmetry in whisking movements (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

12. Outline • Introduction • Rat’s vibrissal system • Neural Processing • Whisking Robots • Discussion and Future

13. Neural Processing • Whisker deflections are converted into physiological signals. • These signals are processed in the thalamus and sensory cortex • There exists a one-to-one mapping between the whiskers and barrels in the sensory cortex Image – Vibrissal sensory processing pathway (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

14. Outline • Introduction • Rat’s vibrissal system • Neural Processing • Whisking Robots • Discussion and Future

15. Whisking Robots • Sensor transduction • Potentiometers – to measure torque • Electret microphones • Sensitive to deflection but cannot detect direction • Piezoelectric sensors • Cannot measure static deflections • Magnetic Hall-effect sensors • Robust, lightweight and sensitive

16. Whisking Robots • Actuation • Independently actuated whiskers • Uniform actuation of whiskers • Mechanical properties of the vibrissal shaft • Steel wires • Molded composites • Morphed like rat whiskers • Signal processing • Neuromorphic algorithms

17. aMouse • Rat whiskers were glued to electret microphones • ANNs and spectral analysis for signal processing Image – aMouse (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

18. Whisking sensobot • 4x1 array of whiskers with strain gauges • Extract radial distance • Estimate 3-D object shape Image – Whisking sensobot (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

19. Darwin IX • Whiskers detect deformation along their length • Employed neuromorphic computational methods • Texture discrimination Image – Darwin IX (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

20. Whiskerbot • Orienting to the detected targets Image – Whikserbot (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

21. Scratchbot • Increased degrees of freedom for moving and positioning the whiskers • Including a neck with three degrees of freedom • Hall-effect sensors Image – Scratchbot (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

22. BIOTACT • Modular vibrissal sensing units to be assembled into different configurations Image – Biotact (borrowed from - Whisking with Robots – From Rat Vibrissae to Biomimetic Technology for Active Touch - Tony J. Prescott, Martin J. Pearson, Ben Mitchinson, J. Charles W. Sullivan, and Anthony G. PipeIEEE Robotics & Automation – September 2009.

23. Outline • Introduction • Rat’s vibrissal system • Neural Processing • Whisking Robots • Discussion and Future

24. Discussion • Tactile sensing based navigation is useful in visually occluded environments • Also useful in texture and shape recognition • Construction of 3-D tactile maps of the environment • The transducers (receptors) are away from contact surface • No damage due to direct physical contact

25. Challenges • Better understanding of sensory motor loops in the vibrissal systems of mammals • Biomimetic algorithms for whisker control and processing vibrissal signals • Mapping whisker deflection signals to surface and shape properties

26. Questions / Comments