Utku Culha

Active sensing system with in situ adjustable sensor morphology.

Background Despite the widespread use of sensors in engineering systems like robots and automation systems, the common paradigm is to have fixed sensor morphology tailored to fulfill a specific application. On the other hand, robotic systems are expected to operate in ever more uncertain environments. In order to cope with the challenge, it is worthy of note that biological systems show the importance of suitable sensor morphology and active sensing capability to handle different kinds of sensing tasks with particular requirements. Methodology This paper presents a robotics active sensing system which is able to adjust its sensor morphology in situ in order to sense different physical quantities with desirable sensing characteristics. The approach taken is to use thermoplastic adhesive material, i.e. Hot Melt Adhesive (HMA). It will be shown that the thermoplastic and thermoadhesive nature of HMA enables the system to repeatedly fabricate, attach and detach mechanical structures with a variety of shape and size to the robot end effector for sensing purposes. Via active sensing capability, the robotic system utilizes the structure to physically probe an unknown target object with suitable motion and transduce the arising physical stimuli into information usable by a camera as its only built-in sensor. Conclusions/Significance The efficacy of the proposed system is verified based on two results. Firstly, it is confirmed that suitable sensor morphology and active sensing capability enables the system to sense different physical quantities, i.e. softness and temperature, with desirable sensing characteristics. Secondly, given tasks of discriminating two visually indistinguishable objects with respect to softness and temperature, it is confirmed that the proposed robotic system is able to autonomously accomplish them. The way the results motivate new research directions which focus on in situ adjustment of sensor morphology will also be discussed.

SVAS3: Strain Vector Aided Sensorization of Soft Structures.

Soft material structures exhibit high deformability and conformability which can be useful for many engineering applications such as robots adapting to unstructured and dynamic environments. However, the fact that they have almost infinite degrees of freedom challenges conventional sensory systems and sensorization approaches due to the difficulties in adapting to soft structure deformations. In this paper, we address this challenge by proposing a novel method which designs flexible sensor morphologies to sense soft material deformations by using a functional material called conductive thermoplastic elastomer (CTPE). This model-based design method, called Strain Vector Aided Sensorization of Soft Structures (SVAS3), provides a simulation platform which analyzes soft body deformations and automatically finds suitable locations for CTPE-based strain gauge sensors to gather strain information which best characterizes the deformation. Our chosen sensor material CTPE exhibits a set of unique behaviors in terms of strain length electrical conductivity, elasticity, and shape adaptability, allowing us to flexibly design sensor morphology that can best capture strain distributions in a given soft structure. We evaluate the performance of our approach by both simulated and real-world experiments and discuss the potential and limitations.

Soft Manipulators and Grippers: A Review

Soft robotics is a growing area of research which utilises the compliance and adaptability of soft structures to develop highly adaptive robotics for soft interactions. One area in which soft robotics has the ability to make significant impact is in the development of soft grippers and manipulators. With an increased requirement for automation, robotics systems are required to perform task in unstructured and not well defined environments; conditions which conventional rigid robotics are not best suited. This requires a paradigm shift in the methods and materials used to develop robots such that they can adapt to and work safely in human environments. One solution to this is soft robotics, which enables soft interactions with the surroundings whilst maintaining the ability to apply significant force. This review paper assess the current materials and methods, actuation methods and sensors which are used in the development of soft manipulators. The achievements and shortcomings of recent technology in these key areas are evaluated, and this paper concludes with a discussion on the potential impacts of soft manipulators on industry and society.

Design Principles for Soft-Rigid Hybrid Manipulators

In nature, manipulators have evolved into different morphologies with varying rigidity to accomplish different tasks. Soft and continuum tentacles of the octopus, rigid and strong pincers of the crab and ligamentous jointed fingers of the human demonstrate the relationship between the complexity of a host’s task space and the design of its manipulator. Thus, the purpose of use a robotic manipulator should be considered as an important design parameter which governs the choice of appropriate materials and design rules. For tasks which require delicacy and strength at the same time, such as human-machine interaction, agriculture or robotic surgery hybrid soft-rigid manipulator designs should be investigated. Here, we present four design principles for building hybrid robot manipulators which incorporate soft and rigid materials and demonstrate each principle with working examples.

A Biologically Inspired Soft Robotic Hand Using Chopsticks for Grasping Tasks

In this paper we investigate the dexterity of human manipulation capabilities by using a soft robotic hand. We built a robotic hand based on our inspiration from the real human’s, which is capable of handling chopsticks for grasping variations of objects. The robotic hand is made of soft structures, by using anthropomorphic configurations of bones, joints, ligaments, and tendons, that are connected to a minimum set of motor components, i.e. only four servomotors. By developing a minimalistic physics model of chopstick handling and its simulation experiments, we have identified one of the necessary conditions of actuation which enables the robot to grasp variations of small objects, those with different shape, size and weight.

Free-space locomotion with thread formation

The paper presents a new concept of locomotion for wheeled or legged robots through an object-free space. The concept is inspired by the behaviour of spiders forming silk threads to move in 3D space. The approach provides the possibility of variation in thread diameter by deforming source material, therefore it is useful for a wider coverage of payload by mobile robots. As a case study, we propose a technology for descending locomotion through a free space with inverted formation of threads in variable diameters. Inverted thread formation is enabled with source material thermoplastic adhesive (TPA) through thermally-induced phase transition. To demonstrate the feasibility of the technology, we have designed and prototyped a 300-gram wheeled robot that can supply and deform TPA into a thread and descend with the thread from an existing hanging structure. Experiment results suggest repeatable inverted thread formation with a diameter range of 1.1-4.5 mm, and a locomotion speed of 0.73 cm per minute with a power consumption of 2.5 W.

The Solving by Building Approach Based on Thermoplastic Adhesives

While, in nature, changes of morphology such as body shape, size, and strength play essential roles in animals’ adaptability in a variety of environment, our robotic systems today still severely suffer from the lack of flexibility in morphology which is one of the most significant bottlenecks for their autonomy and adaptability. With the ability to autonomously modify own body shapes or mechanical structures in surroundings, robotic systems could achieve a variety of tasks in flexible and simple manners. For this reason, we have been investigating technological solutions based on a class of unconventional material, the so-called Thermoplastic Adhesives (TPAs), with which the robots are able to construct their own body parts as well as connecting and disconnecting various mechanical structures. Based on our technological exploration so far, in this paper, we introduce the concept of “solving-by-building” approach, in which we consider how autonomous construction of mechanical parts can help robots to improve performances or to “solve” problems in given tasks. Unlike the conventional adaptive systems that can only learn motor control policies, the ability to change mechanical structures can potentially deal with a significantly more variety of problems. By introducing some of the recent case studies in our laboratory, we discuss the challenges and perspectives of the solving-by-building approach based on TPAs.

Modelling of continuous dragline formation in a mobile robot

A dragline-forming technology has been previously proposed to enable locomotion through an open-space where no solid surfaces present. The technology is intended for situations where payload requirements are unanticipated. In those situations, variability in draglines diameter can minimize the use of material hence increase self-sufficiency of the robot. In a previous study, a robot was designed, prototyped and proven to be able to descend through an open-space by forming a thermoplastic dragline with a diameter range of 1.1-4.5 mm. However, the speed of locomotion was rather low due to the lack of an adequate control method for thermoplastic dragline formation. In this paper, models of mass flow and thermodynamics along dragline formation pathway are presented. The models are validated in a newly prototyped robot which forms a dragline continuously. Experiment results show that, when compared to the previous prototype and control method which consists of repeated sequences of discrete events, the speed of descending locomotion is significantly increased and reaches 12.0 cm/min.