Mariangela Manti

Stiffening in Soft Robotics: A Review of the State of the Art

The need for building robots with soft materials emerged recently from considerations of the limitations of service robots in negotiating natural environments, from observation of the role of compliance in animals and plants [1], and even from the role attributed to the physical body in movement control and intelligence, in the so-called embodied intelligence or morphological computation paradigm [2]-[4]. The wide spread of soft robotics relies on numerous investigations of diverse materials and technologies for actuation and sensing, and on research of control techniques, all of which can serve the purpose of building robots with high deformability and compliance. But the core challenge of soft robotics research is, in fact, the variability and controllability of such deformability and compliance.

Soft assistive robot for personal care of elderly people

The authors focus on the possibility to adapt technologies and basic concepts of Soft Robotics for building a new generation of soft modular manipulator for assistive robotics that can safely come into direct contact with humans in a challenging scenario which is the bathing activity. This paper starts with the presentation of the concept of the modular manipulator and then moves toward a detailed description of one of its modules. The idea is to develop a manipulator which counts on an actuation system based on McKibben-based flexible fluidic actuators combined with motor driven cables, by addressing technological issues related to effectiveness and reliability. Shortening, elongation and bending capabilities have been assessed by testing different patterns of activations. These measures allowed the estimation of the single module performances and its workspace. These outcomes represent the starting point for the development of a novel modular manipulator to be used as a shower arm for bathing activities.

Towards the development of a soft manipulator as an assistive robot for personal care of elderly people

Manipulators based on soft robotic technologies exhibit compliance and dexterity which ensures safe human–robot interaction. This article is a novel attempt at exploiting these desirable properties to develop a manipulator for an assistive application, in particular, a shower arm to assist the elderly in the bathing task. The overall vision for the soft manipulator is to concatenate three modules in a serial manner such that (i) the proximal segment is made up of cable-based actuation to compensate for gravitational effects and (ii) the central and distal segments are made up of hybrid actuation to autonomously reach delicate body parts to perform the main tasks related to bathing. The role of the latter modules is crucial to the application of the system in the bathing task; however, it is a nontrivial challenge to develop a robust and controllable hybrid actuated system with advanced manipulation capabilities and hence, the focus of this article. We first introduce our design and experimentally characterize its functionalities, which include elongation, shortening, omnidirectional bending. Next, we propose a control concept capable of solving the inverse kinetics problem using multiagent reinforcement learning to exploit these functionalities despite high dimensionality and redundancy. We demonstrate the effectiveness of the design and control of this module by demonstrating an open-loop task space control where it successfully moves through an asymmetric 3-D trajectory sampled at 12 points with an average reaching accuracy of 0.79 cm ± 0.18 cm. Our quantitative experimental results present a promising step toward the development of the soft manipulator eventually contributing to the advancement of soft robotics.

Design and development of a bio-inspired, under-actuated soft gripper

The development of robotic devices able to perform manipulation tasks mimicking the human hand has been assessed on large scale. This work stands in the challenging scenario where soft materials are combined with bio-inspired design in order to develop soft grippers with improved grasping and holding capabilities. We are going to show a low-cost, under-actuated and adaptable soft gripper, highlighting the design and the manufacturing process. In particular, a critical analysis is made among three versions of the gripper with same design and actuation mechanism, but based on different materials. A novel actuation principle has been implemented in both cases, in order to reduce the encumbrance of the entire system and improve its aesthetics. Grasping and holding capabilities have been tested for each device, with target objects varying in shape, size and material. Results highlight synergy between the geometry and the intrinsic properties of the soft material, showing the way to novel design principles for soft grippers.

An Under-Actuated and Adaptable Soft Robotic Gripper

Development of soft robotic devices with grasping capabilities is an active research area. The inherent property of soft materials, to distribute contact forces, results in a more effective robot/environment interaction with simpler control. In this paper, a three-finger under-actuated adaptable soft gripper is proposed, highlighting the design and manufacturing process. A novel design and actuation principle have been implemented to obtain the desired grasping abilities, from mechanical properties of materials and structures. Soft materials have been used to make each finger, for a high adaptability of the gripper to different shapes. We implemented an under-actuated mechanism through a wire loop actuation system, that helps achieving passive adaptation during grasping. Passive adaptability allows to drive the device with a reduced number of control parameters. The soft gripper has been lodged into an experimental setup endowed with one actuation unit for the synchronous flexion of its fingers. Grasping and holding capabilities have been tested by evaluating the grasp stability with target objects varying in shape, size and material. Adaptability makes this soft device a good application of morphological computation principles in bio-inspired robots design, where proper design of mechanical features simplifies control.

Contest-Driven Soft-Robotics Boost: The RoboSoft Grand Challenge

This paper reports the design process, the implementation and the results of a novel robotic contest addressing soft robots, named RoboSoft Grand Challenge. Application-oriented tasks were proposed in three different scenarios where soft robotics is particularly lively: manipulation, terrestrial and underwater locomotion. Starting from about sixty expressions of interest submitted by international teams distributed across the world, nineteen robots were eventually selected to participate in the challenge in two of the initially proposed scenarios, i.e. manipulation and terrestrial locomotion. Results highlight both the effectiveness and limitations of state of the art soft robots with respect to the selected tasks. The paper will also focus on some of the advantages and disadvantages of contests as technology-steering mechanisms, including what we called “reductionist design”, a phenomenon in which simplistic solutions are devised to purposely tackle the proposed tasks, possibly hindering more general and desired technological advancements.

Multiobjective Optimization for Stiffness and Position Control in a Soft Robot Arm Module

The central concept of this letter is to develop an assistive manipulator that can automate the bathing task for elderly citizens. We propose to exploit principles of soft robotic technologies to design and control a compliant system to ensure safe human–robot interaction, a primary requirement for the task. The overall system is intended to be modular with a proximal segment that provides structural integrity to overcome gravitational challenges and a distal segment to perform the main bathing activities. The focus of this letter is on the design and control of the latter module. The design comprises of alternating tendons and pneumatics in a radial arrangement, which enables elongation, contraction, and omnidirectional bending. Additionally, a synergetic coactivation of cables and tendons in a given configuration allows for stiffness modulation, which is necessary to facilitate washing and scrubbing. The novelty of the work is twofold: 1) Three base cases of antagonistic actuation are identified that enable stiffness variation. Each category is then experimentally characterized by the application of an external force that imposes a linear displacement at the tip in both axial and lateral directions. 2) The development of a novel algorithm based on cooperative multiagent reinforcement learning that simultaneously optimizes stiffness and position. The results highlight the effectiveness of the design and control to contribute toward the development of the assistive device.

A biorobotic model of the human larynx

This work focuses on a physical model of the human larynx that replicates its main components and functions. The prototype reproduces the multilayer vocal folds and the ab/adduction movements. In particular, the vocal folds prototype is made with soft materials whose mechanical properties have been obtained to be similar to the natural tissue in terms of viscoelasticity. A computational model was used to study fluid-structure interaction between vocal folds and the airflow. This tool allowed us to make a comparison between theoretical and experimental results. Measurements were performed with this prototype in an experimental platform comprising a controlled air flow, pressure sensors and a high-speed camera for measuring vocal fold vibrations. Data included oscillation frequency at the onset pressure and glottal width. Results show that the combination between vocal fold geometry, mechanical properties and dimensions exhibits an oscillation frequency close to that of the human vocal fold. Moreover, computational results show a high correlation with the experimental one.

Exploiting Morphology of a Soft Manipulator for Assistive Tasks

The idea of using embodied intelligence over traditional well-structured design and control formulations has given rise to simple yet elegant applications in the form of soft grippers and compliant locomotion-based robots. Real-world applications of soft manipulators are however limited, largely due to their low accuracy and force transmission. Nonetheless, with the rise of robotic appliances in the field of human-robot interaction, their advantages could outweigh their control deficiencies. In this context, the embodied intelligence could play an important role in developing safe and robust controllers. In this paper, we present a three module soft manipulator to experimentally demonstrate how its morphological properties can be exploited through interactions with the external environment. In particular, we show how to improve the pose accuracy in an assistive task using a simple control algorithm. The soft manipulator takes advantage of its inherent compliance and the physical constraints of the external environment to accomplish a safe interactive task with the user. There exists a continuous and mutual adaptation between the soft-bodied system and the environment. This feature can be used in tasks where the environment is unstructured (e.g. specific body region), and the adaptability of the interaction is entirely dependent on the morphology and control of the system. Experimental results indicate that significant improvements in the tracking accuracy can be achieved by a simple yet appropriate environmental constraint.