Jonathan Rossiter

Swimming like algae: biomimetic soft artificial cilia

Cilia are used effectively in a wide variety of biological systems from fluid transport to thrust generation. Here, we present the design and implementation of artificial cilia, based on a biomimetic planar actuator using soft-smart materials. This actuator is modelled on the cilia movement of the alga Volvox, and represents the cilium as a piecewise constant-curvature robotic actuator that enables the subsequent direct translation of natural articulation into a multi-segment ionic polymer metal composite actuator. It is demonstrated how the combination of optimal segmentation pattern and biologically derived per-segment driving signals reproduce natural ciliary motion. The amenability of the artificial cilia to scaling is also demonstrated through the comparison of the Reynolds number achieved with that of natural cilia.

Bioinspired adaptive control for artificial muscles

The new field of soft robotics offers the prospect of replacing existing hard actuator technologies by artificial muscles more suited to human-centred robotics. It is natural to apply biomimetic control strategies to the control of these actuators. In this paper a cerebellar-inspired controller is successfully applied to the real-time control of a dielectric electroactive actuator. To analyse the performance of the algorithm in detail we identified a time-varying plant model which accurately described actuator properties over the length of the experiment. Using synthetic data generated by this model we compared the performance of the cerebellar-inspired controller with that of a conventional adaptive control scheme (filtered-x LMS). Both the cerebellar and conventional algorithms were able to control displacement for short periods, however the cerebellar-inspired algorithm significantly outperformed the conventional algorithm over longer duration runs where actuator characteristics changed significantly. This work confirms the promise of biomimetic control strategies for soft-robotics applications.

Microbial-powered artificial muscles for autonomous robots

We consider the embodiment of a microbial fuel cell using artificial muscle actuators. The microbial fuel cell digests organic matter and generates electricity. This energy is stored in a capacitor bank until it is discharged to power one of two complimentary artificial muscle technologies: the dielectric elastomer actuator and the ionic-polymer metal composite. We study the ability of the fuel cell to generate useful actuation and consider appropriate configurations to maximally exploit both of these artificial muscle technologies. A prototype artificial sphincter is implemented using a dielectric elastomer actuator. Stirrer and cilia mechanisms motivate experimentation using ionic polymer metal composite actuators. The ability of the fuel cell to drive both of these technologies opens up new possibilities for truly biomimetic soft artificial robotic organisms.

Euglenoid-inspired Giant Shape Change for Highly Deformable Soft Robots

Nature has exploited softness and compliance in many different forms, from large cephalopods to microbial bacteria and algae. In all these cases, large body deformations are used for both object manipulation and locomotion. The great potential of soft robotics is to capture and replicate these capabilities in controllable robotic form. This letter presents the design of a bioinspired actuator capable of achieving a large volumetric change. Inspired by the changes in body shape seen in the euglena Eutreptiella spirogyra during its characteristic locomotion, a novel soft pneumatic actuator has been designed that exploits the hyperelastic properties of elastomers. We call this the hyperelastic bellows (HEB) actuator. The result is a structure that works under both positive and negative pressure to achieve euglenoid-like multimodal actuation. Axial expansion of 450% and a radial expansion of 80% have been observed, along with a volumetric change of 300 times. Furthermore, the design of a segmented robot with multiple chambers is presented, which demonstrates several of the characteristic shapes adopted by the euglenoid in its locomotion cycle. This letter shows the potential of this new soft actuation mechanism to realise biomimetic soft robotics with giant shape changes.

Developing the Cerebellar Chip as a General Control Module for Autonomous Systems

Biological systems have evolved robust, adaptive control strategies to deal with a wide range of control tasks in time varying systems and environments. The cerebellum is the brain structure particularly associated with the control of skilled movements, the advantageous properties of the cerebellum can be exploited for robotic control applications. In this contribution we present a bioinspired cerebellar control algorithm. We extend the existing cerebellar inspired adaptive filter control algorithm, previously applied to plants of specific order, to the control of general (n^mathrm{th }) order plants. This is done by augmenting the existing cerebellar algorithm with a reference model, a technique used in model reference adaptive control. This augmented cerebellar controller is applied successfully to the simulated control of a general plant, and to the real time control of a dielectric electroactive polymer actuator. This augmented biomimetic control strategy has promise for the control of human-centred robots operating in unstructured environments.

Control-Oriented Nonlinear Dynamic Modelling of Dielectric Electro-Active Polymers

Electro-ActiveJacobs, Will Wilson, Emma D. Assaf, Tareq Rossiter, Jonathan Dodd, Tony J. Porrill, John Anderson, Sean R. Polymers (EAPs) are a rapidly developing actuation technology in the field of soft robotics. These soft actuators have the potential to replace existing hard actuator technologies for many applications, combining desirable features such as relatively large actuation strain, low mass, high response speed and compliance [1]. The characteristics of EAPs have drawn comparison to biological muscle [2], generating interest from the robotics community because of the potential for emulating the many versatile ways muscle is used in nature: as motors, brakes, springs and struts.

Sub-millilitre microbial fuel cell power for soft robots

Conventional rigid-body robots operate using actuators which differ markedly from the compliant, muscular bodies of biological organisms that generate their energy through organic metabolism. We consider an artificial stomach comprised of a single microbial fuel cell (MFC), converting organic detritus to electricity, used to drive an electroactive artificial muscle. This bridges the crucial gap between a bio-inspired energy source and a bio-inspired actuator. We demonstrate how a sub-mL MFC can charge two 1F capacitors, which are then controllably discharged into an ionic polymer metal composite (IPMC) artificial muscle, producing highly energetic oscillation over multiple actuation cycles. This combined bio-inspired power and actuation system demonstrates the potential to develop a soft, mobile, energetically autonomous robotic organism. In contrast to prior research, here we show energy autonomy without expensive voltage amplification.