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. Pipe IEEE Robotics & Automation – September Rakesh Gosangi PRISM lab Department of Computer Science and Engineering Texas A&M University

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

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

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. Pipe IEEE Robotics & Automation – September 2009.

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. Pipe IEEE Robotics & Automation – September 2009.

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

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

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

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. Pipe IEEE Robotics & Automation – September 2009.

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 Movement of whiskers of a head-restrained rat 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. Pipe IEEE Robotics & Automation – September 2009.

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. Pipe IEEE Robotics & Automation – September 2009.

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

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. Pipe IEEE Robotics & Automation – September 2009.

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

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

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

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. Pipe IEEE Robotics & Automation – September 2009.

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. Pipe IEEE Robotics & Automation – September 2009.

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. Pipe IEEE Robotics & Automation – September 2009.

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. Pipe IEEE Robotics & Automation – September 2009.

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. Pipe IEEE Robotics & Automation – September 2009.

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. Pipe IEEE Robotics & Automation – September 2009.

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

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

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

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