C.D. Onal

Worcester Polytechnic Institute | WPI · Department of Mechanical Engineering

Objective: For transradial amputees, robotic prosthetic hands promise to regain the capability to perform daily living activities. Current control methods based on physiological signals such as electromyography (EMG) are prone to yielding poor inference outcomes due to motion artifacts, muscle fatigue, and many more. Vision sensors are a major sour...

Intelligent control of soft robots is challenging due to the nonlinear and difficult-to-model dynamics. One promising model-free approach for soft robot control is reinforcement learning (RL). However, model-free RL methods tend to be computationally expensive and data-inefficient and may not yield natural and smooth locomotion patterns for soft ro...

This paper aims to solve the contact-aware locomotion problem of a soft snake robot by developing bio-inspired contact-aware locomotion controllers. To provide effective contact information for the controllers, we develop a scale-covered sensor structure mimicking natural snakes' scale sensilla. In the design of the control framework, our core cont...

Robot grippers that lack physical compliance have a difficult time dealing with uncertainty, such as fragile objects that may not have well-defined shapes. Existing soft robotic grippers require a large empty workspace for their actuated fingers to curl around the objects of interest, limiting their performance in clutter. This article presents a t...

Snakes are a remarkable source of inspiration for mobile search-and-rescue robots. Their unique slender body structure and multiple modes of locomotion are well-suited to movement in narrow passages and other difficult terrain. The design, manufacturing, modeling, and control techniques of soft robotics make it possible to imitate the structure, me...

Supporting videos for the experiment part of the article draft "Reinforcement Learning of a CPG-regulated Locomotion Controller for a Soft Snake Robot", all videos are presented in 1x real time speed.

In this work, we present a learning-based goal-tracking control method for soft robot snakes. Inspired by biological snakes, our controller is composed of two key modules: A reinforcement learning (RL) module for learning goal-tracking behaviors given stochastic dynamics of the soft snake robot, and a central pattern generator (CPG) system with the...

The demining of landmines using drones is challenging; air-releasable payloads are typically non-intelligent (e.g., water balloons or explosives) and deploying them at even low altitudes (~6 meter) is inherently inaccurate due to complex deployment trajectories and constrained visual awareness by the drone pilot. Soft robotics offers a unique appro...

Soft robots, robots that are constructed out of soft materials or using compliant actuation methods, can operate safely in complex environments without fear of damaging their surroundings or themselves. However, the soft materials and structures can be imprecise and difficult to control. This thesis seeks to remedy this problem for reverse pneumati...

Purpose of Review Soft robotics enables unprecedented capabilities for mobile robots that could not be previously achieved using rigid mechanisms. This article serves as a reference for researchers working in soft robotic locomotion, provides classifications and trends in this field, and looks ahead to make recommendations for future developments....

In this paper, we present a model-free learning-based control scheme for the soft snake robot to improve its contact-aware locomotion performance in a cluttered environment. The control scheme includes two cooperative controllers: A bio-inspired controller (C1) that controls both the steering and velocity of the soft snake robot, and an event-trigg...

For lower arm amputees, robotic prosthetic hands offer the promise to regain the capability to perform fine object manipulation in activities of daily living. Current control methods based on physiological signals such as EEG and EMG are prone to poor inference outcomes due to motion artifacts, variability of skin electrode junction impedance over...

The COVID-19 pandemic is responsible for hundreds of thousands of deaths worldwide and remains a challenge that humanity must still overcome. As hospitals continue to admit critical patients, they face medical equipment shortages that may hinder life-saving treatments. We seek to combat this equipment shortage by presenting a proof-of-concept porta...

Limb deficiency severely affects the daily lives of amputees and drives efforts to provide functional robotic prosthetic hands to compensate this deprivation. Convolutional neural network-based computer vision control of the prosthetic hand has received increased attention as a method to replace or complement physiological signals due to its reliab...

Snake robotics is an important research topic with a wide range of applications, including inspection in confined spaces, search-and-rescue, and disaster response. Snake robots are well-suited to these applications because of their versatility and adaptability to unstructured and constrained environments. In this paper, we introduce a soft pneumati...

In this paper, we present a new locomotion control method for soft robot snakes. Inspired by biological snakes, our control architecture is composed of two key modules: A reinforcement learning (RL) module for achieving adaptive goal-tracking behaviors with changing goals, and a central pattern generator (CPG) system with Matsuoka oscillators for g...

Continuum robot arms, with their hyper-redundant continuously deformable bodies, show great promise in applications deemed impossible for traditional rigid robot arms with discrete links and joints, such as navigating tight corners without getting stuck. However, existing continuum robots suffer from excessive twisting when subjected to offset load...

It is important to investigate object perception for classification or recognition based on touch sensing, especially when robots are operating in darkness or the objects are difficult to capture by vision sensors. In this work, we present a new form of continuum manipulator equipped with sparse touch sensing, validate the effectiveness of automati...

In this paper, we present a new locomotion control method for soft robot snakes. Inspired by biological snakes, our control architecture is composed of two key modules: A deep reinforcement learning (RL) module for achieving adaptive goal-reaching behaviors with changing goals, and a central pattern generator (CPG) system with Matsuoka oscillators...

Soft continuum manipulators, inspired by squid tentacles and elephant trunks, show promise in allowing robots to safely interact with complex environments. One ongoing problem for these manipulators is torsional stiffness, as continuum manipulators are naturally compliant and cannot actively resist torsional strain. A hybrid actuator that combines...

Robot teleoperation is a transformative field that can enable workers to safely perform tasks in dangerous environments. In this paper, we present our work towards a teleoperation system with safe, realistic force feedback for intuitive control of a robotic arm and anthropomorphic robotic hand as its end effector. The system interfaces with the use...

In this paper, we present the mechanical design and control system of a new indoor and outdoor Quad-Tilt-Wing flying robot. The proposed flying robot can achieve vertical takeoff, hovering, and long duration horizontal high-speed flight. All of these flight modes can be achieved by simply changing the angle of the rotors and wings by a tilt mechani...

Limb deficiency severely affects the daily lives of amputees and drives efforts to provide functional robotic prosthetic hands to compensate this deprivation. Convolutional neural network-based computer vision control of the prosthetic hand has received increased attention as a method to replace or complement physiological signals due to its reliab...

In this work we present a framework that is capable of accurately representing soft robotic actuators in a multi-physics environment in real-time. We propose a constraint-based dynamics model of a 1-dimensional pneumatic soft actuator that accounts for internal pressure forces, as well as the effect of actuator latency and damping under inflation a...

Animals and insects evolved distinct traits over millions of years of natural selection, which enable them to adapt to, and perform reliably in, a variety of unstructured environments. Nature abounds in examples of such natural creatures that exploit features like softness, compliance, and configurability to achieve effective interactions with thei...

In this work we present a framework that is capable of accurately representing soft robotic actuators in a multiphysics environment in real-time. We propose a constraint-based dynamics model of a 1-dimensional pneumatic soft actuator that accounts for internal pressure forces, as well as the effect of actuator latency and damping under inflation an...

Soft pneumatic actuators promise simple, adaptable, and safe manipulation, but the nature of pneumatic circuits limits the scalability of this approach. This paper introduces a method to augment the degrees-of-freedom of soft pneumatic actuators without increasing the number of independent pressure sources or complex valving networks. Our method ac...

Despite offering many advantages over traditional rigid actuators, soft pneumatic actuators suffer from a lack of comprehensive, computationally efficient models and precise embedded control schemes without bulky flow-control valves and extensive computer hardware. In this article, we consider an inexpensive and reliable soft linear actuator, calle...

Data Availability File. This file contains the data used in this paper. (ZIP)

Advances in soft robotics provide a unique approach for delivering haptic feedback to a user by a soft wearable device. Such devices can apply forces directly on the human joints, while still maintaining the safety and flexibility necessary for use in close proximity to the human body. To take advantage of these properties, we present a new haptic...

We present a novel approach to achieve decentralized distribution of forces in a multirobot system. In this approach, each robot in the group relies on the behavior of a cooperative virtual teammate that is defined independent of the population and formation of the real team. Consequently, such formulation eliminates the need for interagent communi...

Recent advances in robotics promise a future where robots co-exist and collaborate with humans in unstructured environments, which will require frequent physical interactions where accurate tactile information will be crucial for performance and safety. This article describes the design, fabrication, modeling, and experimental validation of a soft-...

Snake robots offer a useful and unique mobility platform for search-and-rescue applications. However, existing prototypes made of rigid links and joints are hampered by a lack of flexibility that limits their utility in highly cluttered, maze-like environments, and their heavy weight limits their energy-efficiency and performance in 3-D tasks. To a...

The emerging field of soft robotics makes use of many classes of materials including metals, low glass transition temperature (Tg) plastics, and high Tg elastomers. Dependent on the specific design, all of these materials may result in extrinsically soft robots. Organic elastomers, however, have elastic moduli ranging from tens of megapascals down...

Real-world environments are complex, unstructured, and often fragile. Soft robotics offers a solution for robots to safely interact with the environment and human coworkers, but suffers from a host of challenges in sensing and control of continuously deformable bodies. To overcome these challenges, this article considers a modular soft robotic arch...

Soft pneumatic actuators enable robots to interact safely with complex environments, but often suffer from imprecise control and unpredictable dynamics. This article addresses these challenges through the use of model reference adaptive control, which modulates the input to the plant to ensure that it behaves similarly to a reference dynamic model....

We wish to develop robot systems that are increasingly more elastic, as a step towards bridging the gap between man-made machines and their biological counterparts. To this end, we develop soft actuators fabricated from elastomer films with embedded fluidic channels. These actuators offer safety and adaptability and may potentially be utilized in r...

This article covers details the design, fabrication, experimental analysis, and first flight tests of μPlane, an origami-inspired aerial vehicle. μPlane is a monoplane with a straight wing planform that has a wingspan of 580 millimeters and can reach a maximum linear velocity of 6.12 meters-per-second. The body of the μPlane is fabricated by foldin...

Nonlinearities, differential constraints, and input limitations preclude the use of regular feedback control algorithms in a range of complex dynamic systems. This article introduces the concept of Regionally Growing Random Trees (RGRT) as a powerful tool that synergistically combines motion planning and control tasks. RGRT is a forest of Dynamics-...

Last decade witnessed the revival of fluidic soft actuation. As pressure-operated soft robotics becomes more popular with promising recent results, system integration remains an outstanding challenge. Inspired greatly by biology, we envision future robotic systems to embrace mechanical compliance with bodies composed of soft and hard components as...

This article details the formulation of a decentralized controller for collective manipulation that does not require any communication between agents involved in the task. First, a centralized controller based on the complete system Jacobian is discussed as a benchmark. Then, the centralized controller is reformulated to obtain the algorithm for th...

Robots are complex systems, and their design requires detailed knowledge of diverse fields, including mechanics, electronics, software, and control theory. Thus, our ability to rapidly create robotic systems requires a synergy between these diverse disciplines. In the near future, new paradigms and tools will be needed for on-demand design generati...

This study demonstrates a new approach to autonomous folding for the body of a 3D robot from a 2D sheet, using heat. We approach this challenge by folding a 0.27-mm sheetlike material into a structure. We utilize the thermal deformation of a contractive sheet sandwiched by rigid structural layers. During this baking process, the heat applied on the...

As an emerging field, soft-bodied robots require profoundly different approaches to sensing and actuation compared to their rigid-bodied counterparts. Electro-mechanical design, fabrication, and operational challenges due to material elasticity significantly complicate embedded, modular and precise proprioceptive feedback. This work presents a nove...

In this paper, we describe unique thermally responsive polymer system based on nanotube-elastomers dispersed with core-shell expanding microspheres (phase-change material). Upon thermal or infrared stimuli, liquid hydrocarbon cores encapsulated within the microspheres vaporize, expanding the surrounding shells and stretching the matrix. Microsphere...

Our pressure-operated soft snake robot promises inherent flexibility and versatility to operate on complex and unpredictable environments compared to traditional snake robots made of rigid linkage chains. We previously presented a theoretical framework to describe its unique dynamic behavior and experimentally verified the accuracy of this model. T...

Soft actuators can be useful in human-occupied environments because of their adaptable compliance and light weight. We previously introduced a variation of fluidic soft actuators we call the reverse pneumatic artificial muscle (rPAM), and developed an analytical model to predict its performance both individually and while driving a 1 degree of free...

Origami-inspired folding enables integrated design and manufacturing of intricate kine-matic mechanisms and structures. Here, we present a hierarchical development process of foldable robotic platforms as combinations of fundamental building blocks to achieve arbitrary levels of complexity and functionality. Rooted in theoretical linkage kinematics...

Soft robotic snakes promise significant advantages in achieving traveling curvature waves with a reduced number of active segments as well as allowing for safe and adaptive interaction with the environment and human users. However, current soft robot platforms suffer from a lack of accurate theoretical dynamic models and proprioceptive measurements...

Robot manufacturing is currently highly specialized, time consuming, and expensive, limiting accessibility and customization. Existing rapid prototyping techniques (e.g., 3-D printing) can achieve complex geometries and are becoming increasingly accessible; however, they are limited to one or two materials and cannot seamlessly integrate active com...

Many pneumatic energy sources are available for use in autonomous and wearable soft robotics, but it is often not obvious which options are most desirable or even how to compare them. To address this, we compare pneumatic energy sources and review their relative merits. We evaluate commercially available battery-based microcompressors (singly, in p...

In this paper we describe the design, fabrication, control, and experimental validation of a soft and highly compliant 2D manipulator. The arm consists of several body segments actuated using bi-directional fluidic elastomer actuators and is fabricated using a novel composite molding process. We use a cascaded PI and PID computation and novel fluid...

This paper addresses the theoretical modeling of the dynamics of a pressure-operated soft snake robot. An accurate dynamic model is a fundamental requirement for optimization, control, navigation, and learning algorithms for a mobile robot that can undergo serpentine locomotion. Such algorithms can be readily implemented for traditional rigid robot...

For a mobile robot undergoing serpentine locomotion, an accurate dynamic model is a fundamental requirement for optimization, control, navigation, and learning algorithms. Such algorithms can be readily implemented for traditional rigid robots, but remain a challenge for nonlinear and low-bandwidth soft robotic systems. This article addresses the t...

This paper presents the development of a lightweight origami-inspired foldable hexapod robot. Using a single sheet of polyester and a laser cutter, the hexapod robot can be fabricated and assembled in less than one hour from scratch. No screw or other external tools are required for assembly. The robot has built-in polyester fasteners considered in...