Klizni režimi u sustavima upravljanja gibanjem

In this paper we discuss the realization of motion control systems in the sliding mode control (SMC) framework. Any motion control system design should take into account the unconstrained motion (generally perceived as a trajectory tracking) and motion of the system in contact with unknown environment (perceived as force control and/or compliance control.) In the SMC framework control is selected to enforce certain preselected dependence among system coordinates, what is interpreted as forcing the system state to stay in selected manifold in state space. In this paper it has been shown that such a formulation allows a unified treatment of the both unconstrained and constrained motion control and, due to the Lyapunov based design, it guaranty the stability of the motion. Moreover control design in this framework allows extension of the solution to control design in interconnected dynamical systems (like mobile robots or bilateral systems).U ovom se članku razmatra realizacija sustava upravljanja gibanjem zasnovana na kliznim režimima. Pri sintezi bilo kojeg sustava upravljanja gibanjem treba uzeti u obzir neometano gibanje, općenito tretirano kao slijeđenje trajektorije, i gibanje sustava u kontaktu s nepoznatom okolinom, tretirano kao upravljanje silom i/ili upravljanje prianjanjem. Kod upravljanja zasnovanog na kliznim režimima upravljački se signal odabire tako da održava unaprijed zadanu ovisnost među varijablama sustava, tj. sustav se giba po zadanoj hiperravnini u prostoru stanja. U ovom je članku pokazano da takva formulacija problema upravljanja omogućuje jedinstveno tretiranje i neometanog gibanja i gibanja u kontaktu s okolinom, a zbog sinteze zasnovane na teoriji Ljapunova jamči se stabilnost gibanja. K tome, sinteza sustava upravljanja zasnovana na predloženoj metodologiji može se proširiti i na međuovisne dinamičke sustave, kao što su mobilni roboti i bilateralni sustavi

Reinforcement Learning of CPG-regulated Locomotion Controller for a Soft Snake Robot

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 robots. In this work, we develop a bio-inspired design of a learning-based goal-tracking controller for a soft snake robot. The controller is composed of two modules: An RL module for learning goal-tracking behaviors given the unmodeled and stochastic dynamics of the robot, and a central pattern generator (CPG) with the Matsuoka oscillators for generating stable and diverse locomotion patterns. We theoretically investigate the maneuverability of Matsuoka CPG's oscillation bias, frequency, and amplitude for steering control, velocity control, and sim-to-real adaptation of the soft snake robot. Based on this analysis, we proposed a composition of RL and CPG modules such that the RL module regulates the tonic inputs to the CPG system given state feedback from the robot, and the output of the CPG module is then transformed into pressure inputs to pneumatic actuators of the soft snake robot. This design allows the RL agent to naturally learn to entrain the desired locomotion patterns determined by the CPG maneuverability. We validated the optimality and robustness of the control design in both simulation and real experiments, and performed extensive comparisons with state-of-art RL methods to demonstrate the benefit of our bio-inspired control design.Comment: 20 pages, 17 figures, 4 tables, in IEEE Transactions on Robotic

Technical Report: A Contact-aware Feedback CPG System for Learning-based Locomotion Control in a Soft Snake Robot

Integrating contact-awareness into a soft snake robot and efficiently controlling its locomotion in response to contact information present significant challenges. This paper aims to solve contact-aware locomotion problem of a soft snake robot through 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' \textit{scale sensilla}. In the design of control framework, our core contribution is the development of a novel sensory feedback mechanism of the Matsuoka central pattern generator (CPG) network. This mechanism allows the Matsuoka CPG system to work like a "spine cord" in the whole contact-aware control scheme, which simultaneously takes the stimuli including tonic input signals from the "brain" (a goal-tracking locomotion controller) and sensory feedback signals from the "reflex arc" (the contact reactive controller), and generate rhythmic signals to effectively actuate the soft snake robot to slither through densely allocated obstacles. In the design of the "reflex arc", we develop two types of reactive controllers -- 1) a reinforcement learning (RL) sensor regulator that learns to manipulate the sensory feedback inputs of the CPG system, and 2) a local reflexive sensor-CPG network that directly connects sensor readings and the CPG's feedback inputs in a special topology. These two reactive controllers respectively facilitate two different contact-aware locomotion control schemes. The two control schemes are tested and evaluated in the soft snake robot, showing promising performance in the contact-aware locomotion tasks. The experimental results also further verify the benefit of Matsuoka CPG system in bio-inspired robot controller design.Comment: 17 pages, 19 figure

Towards printable robotics: Origami-inspired planar fabrication of three-dimensional mechanisms

This work presents a technique which allows the application of 2-D fabrication methods to build 3-D robotic systems. The ability to print robots introduces a fast and low-cost fabrication method to modern, real-world robotic applications. To this end, we employ laser-engraved origami patterns to build a new class of robotic systems for mobility and manipulation. Origami is suitable for printable robotics as it uses only a flat sheet as the base structure for building complicated functional shapes, which can be utilized as robot bodies. An arbitrarily complex folding pattern can be used to yield an array of functionalities, in the form of actuated hinges or active spring elements. For actuation, we use compact NiTi coil actuators placed on the body to move parts of the structure on-demand. We demonstrate, as a proof-of-concept case study, the end-to-end fabrication and assembly of a simple mobile robot that can undergo worm-like peristaltic locomotion.United States. Defense Advanced Research Projects Agency (Grant W911NF-08-C-0060)United States. Defense Advanced Research Projects Agency (Grant W911NF-08-1-0228

Soft robot actuators using energy-efficient valves controlled by electropermanent magnets

This paper presents the design, fabrication, and evaluation of a novel type of valve that uses an electropermanent magnet [1]. This valve is then used to build actuators for a soft robot. The developed EPM valves require only a brief (5 ms) pulse of current to turn flow on or off for an indefinite period of time. EPMvalves are characterized and demonstrated to be well suited for the control of elastomer fluidic actuators. The valves drive the pressurization and depressurization of fluidic channels within soft actuators. Furthermore, the forward locomotion of a soft, multi-actuator rolling robot is driven by EPM valves. The small size and energy-efficiency of EPM valves may make them valuable in soft mobile robot applications.United States. Defense Advanced Research Projects Agency (Grant W911NF-08-C-0060)United States. Defense Advanced Research Projects Agency (Grant W911NF-08-1-0228)Boeing Compan

Autonomous Soft Robotic Fish Capable of Escape Maneuvers Using Fluidic Elastomer Actuators

In this work we describe an autonomous soft-bodied robot that is both self-contained and capable of rapid, continuum-body motion. We detail the design, modeling, fabrication, and control of the soft fish, focusing on enabling the robot to perform rapid escape responses. The robot employs a compliant body with embedded actuators emulating the slender anatomical form of a fish. In addition, the robot has a novel fluidic actuation system that drives body motion and has all the subsystems of a traditional robot onboard: power, actuation, processing, and control. At the core of the fish's soft body is an array of fluidic elastomer actuators. We design the fish to emulate escape responses in addition to forward swimming because such maneuvers require rapid body accelerations and continuum-body motion. These maneuvers showcase the performance capabilities of this self-contained robot. The kinematics and controllability of the robot during simulated escape response maneuvers are analyzed and compared with studies on biological fish. We show that during escape responses, the soft-bodied robot has similar input–output relationships to those observed in biological fish. The major implication of this work is that we show soft robots can be both self-contained and capable of rapid body motion.National Science Foundation (U.S.) (NSF IIS1226883)National Science Foundation (U.S.) (NSF CCF1138967)National Science Foundation (U.S.) (1122374

Klizni režimi u sustavima upravljanja gibanjem

In this paper we discuss the realization of motion control systems in the sliding mode control (SMC) framework. Any motion control system design should take into account the unconstrained motion (generally perceived as a trajectory tracking) and motion of the system in contact with unknown environment (perceived as force control and/or compliance control.) In the SMC framework control is selected to enforce certain preselected dependence among system coordinates, what is interpreted as forcing the system state to stay in selected manifold in state space. In this paper it has been shown that such a formulation allows a unified treatment of the both unconstrained and constrained motion control and, due to the Lyapunov based design, it guaranty the stability of the motion. Moreover control design in this framework allows extension of the solution to control design in interconnected dynamical systems (like mobile robots or bilateral systems).U ovom se članku razmatra realizacija sustava upravljanja gibanjem zasnovana na kliznim režimima. Pri sintezi bilo kojeg sustava upravljanja gibanjem treba uzeti u obzir neometano gibanje, općenito tretirano kao slijeđenje trajektorije, i gibanje sustava u kontaktu s nepoznatom okolinom, tretirano kao upravljanje silom i/ili upravljanje prianjanjem. Kod upravljanja zasnovanog na kliznim režimima upravljački se signal odabire tako da održava unaprijed zadanu ovisnost među varijablama sustava, tj. sustav se giba po zadanoj hiperravnini u prostoru stanja. U ovom je članku pokazano da takva formulacija problema upravljanja omogućuje jedinstveno tretiranje i neometanog gibanja i gibanja u kontaktu s okolinom, a zbog sinteze zasnovane na teoriji Ljapunova jamči se stabilnost gibanja. K tome, sinteza sustava upravljanja zasnovana na predloženoj metodologiji može se proširiti i na međuovisne dinamičke sustave, kao što su mobilni roboti i bilateralni sustavi

Origami-Inspired Printed Robots

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 components. We propose an alternative approach called printable robots that takes advantage of available planar fabrication methods to create integrated electromechanical laminates that are subsequently folded into functional 3-D machines employing origami-inspired techniques. We designed, fabricated, and tested prototype origami robots to address the canonical robotics challenges of mobility and manipulation, and subsequently combined these designs to generate a new, multifunctional machine. The speed of the design and manufacturing process as well as the ease of composing designs create a new paradigm in robotic development, which has the promise to democratize access to customized robots for industrial, home, and educational use.National Science Foundation (U.S.). Expeditions Program (Grant CCF-1138967

A Soft Robotic Wearable Wrist Device for Kinesthetic Haptic Feedback

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 wrist device using pressure-driven soft actuators called reverse pneumatic artificial muscles (rPAMs) mounted on four sides of the wrist. These actuators are originally pre-strained and release compressive stress under pressure, applying a safe torque around the wrist joints while being compact and portable, representing the first soft haptic device capable of real-time feedback. To demonstrate the functional utility of this device, we created a virtual path-following task, wherein the user employs the motion of their wrist to control their embodied agent. We used the haptic wrist device to assist the user in following the path and study their performance with and without haptic feedback in multiple scenarios. Our results quantify the effect of wearable soft robotic haptic feedback on user performance. Specifically, we observed that our haptic feedback system improved the performance of users following complicated paths in a statistically significant manner, but did not show improvement for simple linear paths. Based on our findings, we anticipate broader applications of wearable soft robotic haptic devices toward intuitive user interactions with robots, computers, and other users