Rongjie Kang

Design, modeling and control of a pneumatically actuated manipulator inspired by biological continuum structures

Biological tentacles, such as octopus arms, have entirely flexible structures and virtually infinite degrees of freedom (DOF) that allow for elongation, shortening and bending at any point along the arm length. The amazing dexterity of biological tentacles has driven the growing implementation of continuum manipulators in robotic systems. This paper presents a pneumatic manipulator inspired by biological continuum structures in some of their key features and functions, such as continuum morphology, intrinsic compliance and stereotyped motions with hyper redundant DOF. The kinematics and dynamics of the manipulator are formulated and identified, and a hierarchical controller taking inspiration from the structure of an octopus nervous system is used to relate desired stereotyped motions to individual actuator inputs. Simulations and experiments are carried out to validate the model and prototype where good agreement was found between the two.

Dynamic model of a hyper-redundant, octopus-like manipulator for underwater applications

The octopus arm is a unique tool that combines strength and flexibility. It can shorten, elongate and bend at any point along its length. To model this behavior, a hyper-redundant manipulator composed of multiple segments is proposed. Each segment is a parallel robotic mechanism with redundant actuation. The kinematics and dynamics of this manipulator are analyzed and simulated utilizing a modular computational modeling method. Simulation results for some primitive movements are presented, and the effect of hydrodynamic forces is included.

A soft body as a reservoir: case studies in a dynamic model of octopus-inspired soft robotic arm

The behaviors of the animals or embodied agents are characterized by the dynamic coupling between the brain, the body, and the environment. This implies that control, which is conventionally thought to be handled by the brain or a controller, can partially be outsourced to the physical body and the interaction with the environment. This idea has been demonstrated in a number of recently constructed robots, in particular from the field of “soft robotics”. Soft robots are made of a soft material introducing high-dimensionality, non-linearity, and elasticity, which often makes the robots difficult to control. Biological systems such as the octopus are mastering their complex bodies in highly sophisticated manners by capitalizing on their body dynamics. We will demonstrate that the structure of the octopus arm cannot only be exploited for generating behavior but also, in a sense, as a computational resource. By using a soft robotic arm inspired by the octopus we show in a number of experiments how control is partially incorporated into the physical arms dynamics and how the arms dynamics can be exploited to approximate non-linear dynamical systems and embed non-linear limit cycles. Future application scenarios as well as the implications of the results for the octopus biology are also discussed.

Dynamic modeling and control of an octopus inspired multiple continuum arm robot

This paper proposes a dynamic model for a multiple continuum arm robot inspired by live octopuses. The kinematics and dynamics for a single arm are analyzed and formulated including the longitudinal muscles, radial muscles, isovolumetric constraints, and interaction between suckers and an object. The single arm model is then expanded to a multiple arm system that is capable of generating archetypal locomotion patterns such as crawling and swimming. A hierarchical controller based on octopus neurophysiology is used to achieve simple and reliable control of the multiple continuum arm system. Simulations for single arm movements and multiple arm locomotions are presented. The results of this work can be used in the study of control schemes for multiple continuum arm robots and live octopuses.

Dynamic continuum arm model for use with underwater robotic manipulators inspired by octopus vulgaris

Continuum structures with a very high or infinite number of degrees of freedom (DOF) are very interesting structures in nature. Mimicking this kind of structures artificially is challenging due to the high number of required DOF. This paper presents a kinematic and dynamic model for an underwater robotic manipulator inspired by Octopus vulgaris. Then, a prototype arm inspired by live octopus is presented and the model validated experimentally. Initial comparisons of simulated and experimental results show good agreement.

Timing-based control via echo state network for soft robotic arm

Soft robots are difficult to control because of their compliant and elastic body dynamics compared with robots made of rigid bodies. In this paper, we present a control scheme inspired by the octopus called timing-based control for soft robotic arms. This control scheme is motivated to positively exploit the natural dynamics of the soft body. We demonstrate a scheme for controlling an object-reaching task by using an echo state network on a 3D physical soft robotic arm simulator and show that this network can successfully perform the task. Detailed analyses and evaluations of the generalization capacity of the network and the performances to the reaching task are presented.

The Nonlinear Accuracy Model of Electro-Hydrostatic Actuator

The electro-hydrostatic actuator (EHA) is a kind of power-by-wire (PBW) actuator. In this paper, a typical architecture of EHA is described and the block diagram model of EHA is established directly from the mathematic equations without transfer functions, which is a nonlinear accuracy model. The influence of refeeding circuit on the EHA system is discussed based on the comparison with conventional linear model. A gain-variable PID controller is introduced to this model to compensate the friction.

Model Validation of an Octopus Inspired Continuum Robotic Arm for Use in Underwater Environments

Octopuses are an example of dexterous animals found in nature. Their arms are flexible, can vary in stiffness, grasp objects, apply high forces with respect to their relatively light weight, and bend in all directions. Robotic structures inspired by octopus arms have to undertake the challenges of a high number of degrees of freedom (DOF), coupled with highly flexible continuum structure. This paper presents a kinematic and dynamic model for underwater continuum robots inspired by Octopus vulgaris. Mass, damping, stiffness, and external forces such as gravity, buoyancy, and hydrodynamic forces are considered in the dynamic model. A continuum arm prototype was built utilizing longitudinal and radial actuators, and comparisons between the simulated and experimental results show good agreement.

Local information transfer in soft robotic arm

Recently, the information theoretic approach has been increasingly used in the robotics community as powerful quantitative measures for characterizing the dynamic coupling between the controller, the body, and the environment in embodied robots. This approach is effective and useful even if this interaction regime becomes complex and nonlinear as is often the case in soft robots. In this study, we propose a method for characterizing and visualizing the information transfer spa-tiotemporally through the robots body. This method is based on the framework called “local information transfer” proposed by Lizier et al. We extend it with the permutation-information theoretic approach, which makes it feasible for continuous time series data usually obtained in robotic platforms. To test the power of the proposed method, we performed experiments using a soft robotic arm simulator and a silicone-based soft robotic arm platform inspired by the octopus and showed that the external damage spreading is successfully and clearly visualized by the method. We also analyzed the robustness of the method to noise. Finally, we discuss future applications and possible extensions.

Octopus inspired walking robot: Design, control and experimental validation

This paper presents an Octopus inspired walking robot with pneumatic muscle actuator (PMA) driven continuum arms. Each arm is made up of 4 longitudinally arranged PMAs, consistent with octopus arm anatomy. We first present the design and construction of a single continuum arm followed by its modeling and experimental validation. The design of the walking robot is then presented followed by details of extended dynamic model describing the full walking robot with four arms. Basic control architecture is introduced for the robot to achieve walking motion and experimental results analyzed. Initial results show good agreement between the experimental results and simulation results.