Visual-tactile sensory map calibration of a biomimetic whiskered robot

© 2016 IEEE. 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

Biohybrid control of general linear systems using the adaptive filter model of cerebellum

© 2015 Wilson, Assaf, Pearson, Rossiter, Dean, Anderson and Porrill. The adaptive filter model of the cerebellar microcircuit has been successfully applied to biological motor control problems, such as the vestibulo-ocular reflex (VOR), and to sensory processing problems, such as the adaptive cancelation of reafferent noise. It has also been successfully applied to problems in robotics, such as adaptive camera stabilization and sensor noise cancelation. In previous applications to inverse control problems, the algorithm was applied to the velocity control of a plant dominated by viscous and elastic elements. Naive application of the adaptive filter model to the displacement (as opposed to velocity) control of this plant results in unstable learning and control. To be more generally useful in engineering problems, it is essential to remove this restriction to enable the stable control of plants of any order. We address this problem here by developing a biohybrid model reference adaptive control (MRAC) scheme, which stabilizes the control algorithm for strictly proper plants. We evaluate the performance of this novel cerebellar-inspired algorithm with MRAC scheme in the experimental control of a dielectric electroactive polymer, a class of artificial muscle. The results show that the augmented cerebellar algorithm is able to accurately control the displacement response of the artificial muscle. The proposed solution not only greatly extends the practical applicability of the cerebellar-inspired algorithm, but may also shed light on cerebellar involvement in a wider range of biological control tasks

Cerebellar-inspired algorithm for adaptive control of nonlinear dielectric elastomerbased artificial muscle

© 2016 The Author(s) Published by the Royal Society. All rights reserved. Electroactive polymer actuators are important for soft robotics, but can be difficult to control because of compliance, creep and nonlinearities. Because biological control mechanisms have evolved to deal with such problems, we investigated whether a control scheme based on the cerebellum would be useful for controlling a nonlinear dielectric elastomer actuator, a class of artificial muscle. The cerebellum was represented by the adaptive filter model, and acted in parallel with a brainstem, an approximate inverse plant model. The recurrent connections between the two allowed for direct use of sensory error to adjust motor commands. Accurate tracking of a displacement command in the actuator's nonlinear range was achieved by either semi-linear basis functions in the cerebellar model or semi-linear functions in the brainstem corresponding to recruitment in biological muscle. In addition, allowing transfer of training between cerebellum and brainstem as has been observed in the vestibulo-ocular reflex prevented the steady increase in cerebellar output otherwise required to deal with creep. The extensibility and relative simplicity of the cerebellar-based adaptive-inverse control scheme suggests that it is a plausible candidate for controlling this type of actuator. Moreover, its performance highlights important features of biological control, particularly nonlinear basis functions, recruitment and transfer of training

Control-focused, nonlinear and time-varying modelling of dielectric elastomer actuators with frequency response analysis

Current models of dielectric elastomer actuators (DEAs) are mostly constrained to first principal descriptions that are not well suited to the application of control design due to their computational complexity. In this work we describe an integrated framework for the identification of control focused, data driven and time-varying DEA models that allow advanced analysis of nonlinear system dynamics in the frequency-domain. Experimentally generated input–output data (voltage-displacement) was used to identify control-focused, nonlinear and time-varying dynamic models of a set of film-type DEAs. The model description used was the nonlinear autoregressive with exogenous input structure. Frequency response analysis of the DEA dynamics was performed using generalized frequency response functions, providing insight and a comparison into the time-varying dynamics across a set of DEA actuators. The results demonstrated that models identified within the presented framework provide a compact and accurate description of the system dynamics. The frequency response analysis revealed variation in the time-varying dynamic behaviour of DEAs fabricated to the same specifications. These results suggest that the modelling and analysis framework presented here is a potentially useful tool for future work in guiding DEA actuator design and fabrication for application domains such as soft robotics

Dataset for paper entitled "A Frequency Modulation-Based Taxel Array: A Bio-Inspired Architecture for Large-Scale Artificial Skin."

Datalogs acquired during experiments related the article "A Frequency Modulation-Based Taxel Array: A Bio-Inspired Architecture for Large-Scale Artificial Skin." These datasets contains both raw data e.g. FM mixed signals generated by the electronic architecture and processed signals e.g. reconstructed demodulated signal. The files are similarly named in pairs e.g. File1XX.txt and FileFM1XX.txt containing the processed data and mixed FM respectively. Another file per pair complements these files providing the list of main variable used (e.g. sampling rate, filters, decimation) and are named as Metadata_File1XX.txt. Two other files are included File1static8k.txt and File1static23k.txt used to generate the input/reconstruction image of the article. These data are collected to assess the performances of the proposed architecture.The hardware used comprises of Hall-effect sensors, FM encoding architecture, NI compact rio acquisition module and Labview processing. A magnet was used to trigger sensor response and the encoding architecture modulated the signal into FM. The NI 9775module was used to sample this analogue signal that was then modulated using realtime system built-in in the Compact RIO. FM and demodulated signal were logged (datasets)

Dataset For "Assessing a new Frequency Modulation architecture for artificial large area skin-like sensory array deployment in robotic platforms"

Evaluation of FM architecture reconstruction accuracy at varying Frequencies using I/Q method. The data input is a constant sinusoildal for all channels from a function generator. The Hardware converted in FM and all channel where mixed together. The software reconstructed each signal tuning to individual channels.The data are a log from the acquisition/processing software

Assessing a new Frequency Modulation architecture for artificial large area skin-like sensory array deployment in robotic platforms

This work presents a new architecture to deploy large-area artificial skin to enhance the spatial awareness of robotic and prosthetic platforms. Adding sensing information will improve robots’ safety both around humans and in unstructured environments. Unlike biological systems, current artificial platforms lack a fully-integrated skin-like layer that would significantly improve dexterity and capabilities. However, artificial skin is limited by the technical issues of scaling power to and communication from many sensors. Many current solutions are either relatively low-power with limited sensor type e.g. contact only, or capable of multiple sensor type readings at the expense of requiring higher power. Their data acquisition and sampling rates are also constrained by the technique used to transfer them. The solution to address these problems uses frequency modulation (FM) to encode many signals on a single wire. This solution is applied as an internal robotic communication protocol. This work describes the design rational and experimentally validates the concept within the frequency range of tactile mechanoreceptors. The proposed architecture has the potential to enable large-area skin deployment

The Role of Cell-Specific Tropism in the Pathogenesis of Rhesus Cytomegalovirus Infection

The 40-year quest for a vaccine against human cytomegalovirus (HCMV) infection has been partially met by targeting the major envelope glycoprotein B (gB). However, the complex natural history of HCMV and the virus ability to infect a wide range of host cell types illustrate the central role cellular tropism plays in HCMV pathogenesis and emphasize the need for a vaccine that targets additional viral determinants of cellular tropism. Multiple genes located within the UL/b' region (UL128-UL154) of the HCMV genome have been implicated in regulating virus entry into epithelial and endothelial cells and modulating several host immune responses mounted against HCMV infection. We utilized virological, histopathological, and epidemiological tools to characterize the relationship between rhesus cytomegalovirus (RhCMV) cellular tropism and the pattern of viral infection in vivo and illustrated the potential of targeting products of genes within the UL/b' region in future vaccine developments. To address this, we inoculated rhesus macaques with three RhCMV strains that vary in their UL/b' coding content. RhCMV UCD52 and UCD59 encode a full complement of open reading frames (ORF) in the UL/b' region; RhCMV 68-1 lacks the UL128 complex essential for endothelial/epithelial tropism, and alpha-chemokine-like ORFs; and RhCMV 180.92 tropic for endothelial/epithelial cells but lacks viral determinants of host immune evasion. Two histopathological hallmarks were observed with the acute infection with RhCMV UCD52 and UCD59 strains: neutrophilic inflammation and infected endothelial cells, both of which were observed during recurrent RhCMV disease in animals coinfected with wild-type RhCMV and simian immunodeficiency virus (SIV). In contrast, animals inoculated with RhCMV 68-1 were noted for an absence of neutrophilic infiltrates and infected endothelial cells, demonstrating the role of UL128 complex in epithelial/endothelial tropism in vivo and further suggest that the long-term pattern of viral infection is determined in large part by the earliest virus-host interactions. Further investigations using RhCMV 180.92 demonstrated lower levels of plasma viremia, limited systemic dissemination, low levels of tissue virus titers, and absent or low level of viral shedding in urine and saliva, compared to the in vivo pattern of a minor RhCMV 180.92 variant present in the virus stock potentially carrying the full complement of UL/b' region. These results demonstrate the possibility that other ORFs, independent of UL128 complex, within the UL/b' region may determine in vivo viral replication, dissemination, and shedding of RhCMV. Finally, RhCMV neuromuscular disease was identified in 10.5% of all SIV-infected animals and 6% demonstrated direct RhCMV infection of skeletal muscles. HCMV has been implicated by association in the pathogenesis of HIV-associated myopathies. However, in vivo studies failed to demonstrate a direct evidence of HCMV infection of skeletal muscle cells. Our results indicate that RhCMV is linked to skeletal myositis and suggest that human HCMV may be a causative agent for similar pathologies in HIV-infected humans

High speed switched, multi-channel drive for high voltage dielectric actuation of a biomimetic sensory array

Electro-Active Polymers (EAP) have been described as artificial muscles due to their composition andmuscle-like dynamics [1]. Consequently they have attracted a lot of attention from the biomimetic robotics research community and heralded as a potential alternative to conventional electromagnetic, pneumatic or hydraulic actuation technologies [2]. However, in practice there are a number of technical barriers to overcome before they gain widespread acceptance as robotic actuators [3]. Here we focus on overcoming one of those limiting factors for a type of EAP referred to as Dielectric Electro-Active Polymers (DEAP). © 2014 Springer International Publishing