Tactile exploration of surfaces is a key component of everyday life, allowing us to make complex inferences about our environments even when vision is occluded. The emergence of biomimetic neuromorphic hardware in recent years has furthered our ability to create biologically plausible sensing solutions. While these platforms continue to improve in regards to latency and power consumption, within recent literature on tactile texture classification there is an emphasis on accuracy at the expense of real-time processing. In order for these tactile sensing systems to find use outside of experimental laboratory environments, it is key to design systems capable of capturing and processing data in real-time. Within this paper we present a system for the real-time classification of texture using a neuromorphic tactile sensor, a spiking neural network and a novel decision making algorithm. Our real-time system achieves classification accuracies of 94% on a dataset of 11 natural textile textures. Furthermore our system is capable of identifying textures at human-level performance in as little as 84ms. Additionally, benchmarking our system across CPU, GPU and Loihi2 hardware platforms resulted in a 96% reduction in power consumption on the neuromorphic platform. This system out-performed previous work by the authors and the state of art, both in terms of accuracy and classification speed.

Tactile feedback is necessary for closing the sen-sorimotor loop in prosthetic and tele-operable control, which would allow for more precise manipulation and increased acceptance of use of such devices. Pressure stimuli are commonly presented to users in haptic devices through a sensory substitution to vibration. The precise nature of this substitution affects pressure sensitivity, as well as the comfort and intuitiveness of the device for the user. This study determines the effects of different vibrational encodings for pressure on user-preference and performance in a 4-alternative absolute identification task. 4 different encoding patterns for pressure were examined: short pulse and long pulse amplitude modulation along with sine and square wave frequency modulation. Of the methods examined, frequency modulation methods led to the best discrimination of stimuli (p$p$= 0.098). This suggests that prostheses or teleoperated devices utilising vibrotactile feedback may benefit from implementing a discrete frequency-based sinusoidal pattern to indicate changes in grip force.

Identifying objects using sparse tactile sensor arrays requires movement across the surface and the integration of sensory information to support hypotheses. In this study we demonstrate a surface placement control strategy to orient and position a biomimetic tactile whisker array relative to the object surface. This reduces the variance in tactile view, or representation, of each region of the object surface thus relaxing the prior pose dependence for object recall. In addition we evaluate two regional search strategies in an attempt to further improve the robustness and speed of object classification.

Here we propose and investigate a novel vibrissal tactile sensor - the Tac Whisker array - based on modifying a 3D-printed optical cutaneous (fingertip) tactile sensor - the TacTip. Two versions are considered: a static Tac Whisker array analogous to immotile tactile vibrissae (e.g. rodent microvib-rissae) and a dynamic Tac Whisker array analogous to motile tactile vibrissae (e.g. rodent macrovibrissae). Performance is assessed on an active object localization task. The whisking motion of the dynamic Tac Whisker leads to millimetre-scale location perception, whereas perception with the static Tac Whisker array is relatively poor when making dabbing contacts. The dynamic sensor output is dominated by a self-generated motion signal, which can be compensated by comparing to a reference signal. Overall, the Tac Whisker arrays give a new class of tactile whiskered robots that benefit from being relatively inexpensive and customizable. Furthermore, the biomimetic basis for the Tac Whiskers fits well with building an embodied model of the rodent sensory system for investigating animal perception.

We present an adaptive filter model of cerebellar function applied to the calibration of a tactile sensory map to improve the accuracy of directed movements of a robotic manipulator. This is demonstrated using a platform called Bellabot that incorporates an array of biomimetic tactile whiskers, actuated using electro-active polymer artificial muscles, a camera to provide visual error feedback, and a standard industrial robotic manipulator. The algorithm learns to accommodate imperfections in the sensory map that may be as a result of poor manufacturing tolerances or damage to the sensory array. Such an ability is an important pre-requisite for robust tactile robotic systems operating in the real-world for extended periods of time. In this work the sensory maps have been purposely distorted in order to evaluate the performance of the algorithm.

A biomimetic mobile robot called “Shrewbot” has been built as part of a neuroethological study of the mammalian facial whisker sensory system. This platform has been used to further evaluate the problem space of whisker based tactile Simultaneous Localisation And Mapping (tSLAM). Shrewbot uses a biomorphic 3-dimensional array of active whiskers and a model of action selection based on tactile sensory attention to explore a circular walled arena sparsely populated with simple geometric shapes. Datasets taken during this exploration have been used to parameterise an approach to localisation and mapping based on probabilistic occupancy grids. We present the results of this work and conclude that simultaneous localisation and mapping is possible given only noisy odometry and tactile information from a 3-dimensional array of active biomimetic whiskers and no prior information of features in the environment.

Future robots may need to navigate where visual sensors fail. Touch sensors provide an alternative modality, largely unexplored in the context of robotic map building. We present the first results in grid based simultaneous localisation and mapping (SLAM) with biomimetic whisker sensors, and show how multi-whisker features coupled with priors about straight edges in the world can boost its performance. Our results are from a simple, small environment but are intended as a first baseline to measure future algorithms against.

Studies of decision making in animals suggest a neural mechanism of evidence accumulation for competing percepts according to Bayesian sequential analysis. This model of perception is embodied here in a biomimetic tactile sensing robot based on the rodent whisker system. We implement simultaneous perception of object shape and location using two psychological test paradigms: first, a free-response paradigm in which the agent decides when to respond, implemented with Bayesian sequential analysis; and second an interrogative paradigm in which the agent responds after a fixed interval, implemented with maximum likelihood estimation. A benefit of free-response Bayesian perception is that it allows tuning of reaction speed against accuracy. In addition, we find that large gains in decision performance are achieved with unforced responses that allow null decisions on ambiguous data. Therefore free-response Bayesian perception offers benefits for artificial systems that make them more animal-like in behavior.

Tactile sensing can be an important source of information for robots, and texture discrimination in particular is useful in object recognition and terrain identification. Whisker based tactile sensing has recently been shown to be a promising approach for mobile robots, using simple sensors and many classification approaches. However these approaches have often been tested in limited environments, and have not been compared against one another in a controlled way. A wide range of whisker-object contact poses are possible on a mobile robot, and the effect such contact variability has on sensing has not been properly investigated. We present a novel, carefully controlled study of simple surface texture classifiers on a large set of varied pose conditions that mimic those encountered by mobile robots. Namely, single brief whisker contacts with textured surfaces at a range of surface orientations and contact speeds. Results show that different classifiers are appropriate for different settings, with spectral template and feature based approaches performing best in surface texture, and contact speed estimation, respectively. The results may be used to inform selection of classifiers in tasks such as tactile SLAM.

Sensory signals are often caused by one's own active movements. This raises a problem of discriminating between self-generated sensory signals and signals generated by the external world. Such discrimination is of general importance for robotic systems, where operational robustness is dependent on the correct interpretation of sensory signals. Here, we investigate this problem in the context of a whiskered robot. The whisker sensory signal comprises two components: one due to contact with an object (externally generated) and another due to active movement of the whisker (self-generated). We propose a solution to this discrimination problem based on adaptive noise cancelation, where the robot learns to predict the sensory consequences of its own movements using an adaptive filter. The filter inputs (copy of motor commands) are transformed by Laguerre functions instead of the often-used tapped-delay line, which reduces model order and, therefore, computational complexity. Results from a contact-detection task demonstrate that false positives are significantly reduced using the proposed scheme.

In this paper, we present two versions of a hardware processing architecture for modeling large networks of leaky-integrate-and-fire (LIF) neurons; the second version provides performance enhancing features relative to the first. Both versions of the architecture use fixed-point arithmetic and have been implemented using a single field-programmable gate array (FPGA). They have successfully simulated networks of over 1000 neurons configured using biologically plausible models of mammalian neural systems. The neuroprocessor has been designed to be employed primarily for use on mobile robotic vehicles, allowing bio-inspired neural processing models to be integrated directly into real-world control environments. When a neuroprocessor has been designed to act as part of the closed-loop system of a feedback controller, it is imperative to maintain strict real-time performance at all times, in order to maintain integrity of the control system. This resulted in the reevaluation of some of the architectural features of existing hardware for biologically plausible neural networks (NNs). In addition, we describe a development system for rapidly porting an underlying model (based on floating-point arithmetic) to the fixed-point representation of the FPGA-based neuroprocessor, thereby allowing validation of the hardware architecture. The developmental system environment facilitates the cooperation of computational neuroscientists and engineers working on embodied (robotic) systems with neural controllers, as demonstrated by our own experience on the Whiskerbot project, in which we developed models of the rodent whisker sensory system.

Both a FPGA implementation of a rodent's tactile sensory system and a neural FPGA based hardware processor, mimicking the brainstem behaviour are presented. They have principally been designed using biological considerations. The two systems are being ported on a single FPGA platform and will ultimately be embedded on a mobile robot, which will operate in real world environments for object recognition and surface textural discrimination purposes

The implementation of a tactile sensory system for neuromorphic signal processing applications is presented. It has been developed by modelling the structure and behaviour of real rodent facial vibrissae. The primary afferents have been modelled using empirical data taken from electrophysiological measurements, and implemented in real time using hardware processors (DSP/FPGA). Pipelining techniques were employed to maximise the utility of the FPGA hardware. The system is to be integrated into a more complete whisker sensory model, including neural structures within the central nervous system, which can be used to orientate a mobile robot

A mobile robot is being built which utilize a biologically inspired whisker array as the primary sensor for both spatial exploration and surface textural analysis. The theme of biomimetry is being developed further by utilizing physiological and electro-physiological studies of the neural pathways involved in the processing and subsequent motor response of real rodents as they use their whiskers. The ABRG have experience in modelling brain function whilst the IAS laboratory are contributing by embedding some of these highly parallel neural algorithms directly into hardware using field programmable gate arrays (FPGA). This approach brings us closer to true, real-time, neurobiologically inspired processing, which is demonstrated by controlling a mobile robot to enact behaviors similar to those observed in rodents such as wall following, object recognition and textural discrimination. The research undertaken so far has identified the numerous neural structures principally involved in the whisker sensory system.

The implementation of a large scale, leaky-integrate-and-fire neural network processor using the Xilinx Virtex-II family of field programmable gate array (FPGA) is presented. The processor has been designed to model biologically plausible networks of spiking neurons in real-time to assist with the control of a mobile robot. The real-time constraint has led to a re-evaluation of some of the established architectural and algorithmic features of previous spiking neural network based hardware. The design was coded and simulated using Handel-C hardware description language (HDL) and the DK3 design suite from Celoxica. The processor has been physically implemented and tested on a RC200 development board, also from Celoxica.