A novel approach to user controlled ambulation of lower extremity exoskeletons using admittance control paradigm

The robotic lower extremity exoskeletons address the ambulatory problems confronting individuals with paraplegia. Paraplegia due to spinal cord injury (SCI) can cause motor deficit to the lower extremities leading to inability to walk. Though wheelchairs provide mobility to the user, they do not provide support to all activities of everyday living to individuals with paraplegia. Current research is addressing the issue of ambulation through the use of wearable exoskeletons that are pre-programmed. There are currently four exoskeletons in the U.S. market: Ekso, Rewalk, REX and Indego. All of the currently available exoskeletons have 2 active Degrees of Freedom (DOF) except for REX which has 5 active DOF. All of them have pre-programmed gait giving the user the ability to initiate a gait but not the ability to control the stride amplitude (height), stride frequency or stride length, and hence restricting users’ ability to navigate across different surfaces and obstacles that are commonly encountered in the community. Most current exoskeletons do not have motors for abduction or adduction to provide users with the option for movement in coronal plane, hence restricting user’s ability to effectively use the exoskeletons. These limitations of currently available pre-programmed exoskeleton models are sought to be overcome by an intuitive, real time user-controlled control mechanism employing admittance control by using hand-trajectory as a surrogate for foot trajectory. Preliminary study included subjects controlling the trajectory of the foot in a virtual environment using their contralateral hand. The study proved that hands could produce trajectories similar to human foot trajectories when provided with haptic and visual feedback. A 10 DOF 1/2 scale biped robot was built to test the control paradigm. The robot has 5 DOF on each leg with 2 DOF at the hip to provide flexion/extension and abduction/adduction, 1 DOF at the knee to provide flexion and 2 DOF at the ankle to provide flexion/extension and inversion/eversion. The control mechanism translates the trajectory of each hand into the trajectory of the ipsilateral foot in real time, thus providing the user with the ability to control each leg in both sagittal and coronal planes using the admittance control paradigm. The efficiency of the control mechanism was evaluated in a study using healthy subjects controlling the robot on a treadmill. A trekking pole was attached to each foot of the biped. The subjects controlled the trajectory of the foot of the biped by applying small forces in the direction of the required movement to the trekking pole through a force sensor. The algorithm converted the forces to Cartesian position of the foot in real time using admittance control; the Cartesian position was converted to joint angles of the hip and knee using inverse kinematics. The kinematics, synchrony and smoothness of the trajectory produced by the biped robot was evaluated at different speeds, with and without obstacles, and compared with typical walking by human subjects on the treadmill. Further, the cognitive load required to control the biped on the treadmill was evaluated and the effect of speed and obstacles with cognitive load on the kinematics, synchrony and smoothness was analyzed

Climbing and Walking Robots

Nowadays robotics is one of the most dynamic fields of scientific researches. The shift of robotics researches from manufacturing to services applications is clear. During the last decades interest in studying climbing and walking robots has been increased. This increasing interest has been in many areas that most important ones of them are: mechanics, electronics, medical engineering, cybernetics, controls, and computers. Today’s climbing and walking robots are a combination of manipulative, perceptive, communicative, and cognitive abilities and they are capable of performing many tasks in industrial and non- industrial environments. Surveillance, planetary exploration, emergence rescue operations, reconnaissance, petrochemical applications, construction, entertainment, personal services, intervention in severe environments, transportation, medical and etc are some applications from a very diverse application fields of climbing and walking robots. By great progress in this area of robotics it is anticipated that next generation climbing and walking robots will enhance lives and will change the way the human works, thinks and makes decisions. This book presents the state of the art achievments, recent developments, applications and future challenges of climbing and walking robots. These are presented in 24 chapters by authors throughtot the world The book serves as a reference especially for the researchers who are interested in mobile robots. It also is useful for industrial engineers and graduate students in advanced study

An Overview of Legged Robots

The objective of this paper is to present the evolution and the state-of-theart in the area of legged locomotion systems. In a first phase different possibilities for mobile robots are discussed, namely the case of artificial legged locomotion systems, while emphasizing their advantages and limitations. In a second phase an historical overview of the evolution of these systems is presented, bearing in mind several particular cases often considered as milestones on the technological and scientific progress. After this historical timeline, some of the present day systems are examined and their performance is analyzed. In a third phase are pointed out the major areas for research and development that are presently being followed in the construction of legged robots. Finally, some of the problems still unsolved, that remain defying robotics research, are also addressed.N/

Implementation of a robot platform to study bipedal walking

On this project, a modi cation of an open source, 3D printed robot, was implemented, with the purpose to create a more a ordable bipedal platform proper for studying Bipedal Walking algorithms. The original robot is a part of an open-source platform, called Poppy, that is formed from an interdisciplinary community of beginners and experts. One of the robots of this platform, is the Poppy Humanoid. The rigid parts of the Poppy Humanoid (as well as the rest of the Poppy platform robots) are 3D printed, a key factor of lowering the cost of a robot. The actuators used though, are expensive commercial DC-motors that increase the total cost of the robot drastically. This high cost of the actuators of Poppy, led this project to modify cheaper actuators while maintaining the same performance of their predecessors. Taking apart the components of the cheaper actuator, only the motor, the gears and the case that host them were kept, and a new design was made to control the motor and to meet the requirements set from the commercial motors. This new design of the actuator include a 12-bit resolution magnetic encoder to read the position of the shaft of the motor, a driver to run the motor, and also an embedded Arduino micro-controller. This feature of an Arduino as part of the actuator, gives the advantage over the commercial motor, as the user has the freedom to upload his own codes and to implement his own motor controllers. The result is a fully programmable actuator hosted on the same motor case. The size of this actuator though, is di erent from the commercial one. In order to mount the new actuators to the platform, Joan Guasch designed proper 3D printed parts. Apart of these parts, Joan also modi ed the leg design, in order to add another joint on the ankle (roll) as this Degree of Freedom (DoF) is important for Bipedal Walking algorithms and was missing from the original Poppy Humanoid leg design. The modi ed robot, is called Poppy-UPC and is a 12 DoF biped platform. For the communication between the motors and the main computer unit, a serial communication protocol was implemented based to the RS-485 standard. Multiple receivers (motors and sensors) can be connected to such a network in a linear, multi-drop con guration. The main computer unit of Poppy-UPC is an Odroid-C1 board. Essentially, this board is a Quad-core Linux computer fully compatible to run ROS. Odroid is acting as the master of the network and is gathering all the informations of the connected nodes, in order to publish them in ROS-topics. That way, the Poppy-UPC is connected to the ROS environment and ROS packages can be used for any further implementation with this platform. Finally, following the open-source spirit of the Poppy platform, all the codes and information are available at https://github.com/dimitris-zervas

Climbing and Walking Robots

With the advancement of technology, new exciting approaches enable us to render mobile robotic systems more versatile, robust and cost-efficient. Some researchers combine climbing and walking techniques with a modular approach, a reconfigurable approach, or a swarm approach to realize novel prototypes as flexible mobile robotic platforms featuring all necessary locomotion capabilities. The purpose of this book is to provide an overview of the latest wide-range achievements in climbing and walking robotic technology to researchers, scientists, and engineers throughout the world. Different aspects including control simulation, locomotion realization, methodology, and system integration are presented from the scientific and from the technical point of view. This book consists of two main parts, one dealing with walking robots, the second with climbing robots. The content is also grouped by theoretical research and applicative realization. Every chapter offers a considerable amount of interesting and useful information

Humanoid Robots

For many years, the human being has been trying, in all ways, to recreate the complex mechanisms that form the human body. Such task is extremely complicated and the results are not totally satisfactory. However, with increasing technological advances based on theoretical and experimental researches, man gets, in a way, to copy or to imitate some systems of the human body. These researches not only intended to create humanoid robots, great part of them constituting autonomous systems, but also, in some way, to offer a higher knowledge of the systems that form the human body, objectifying possible applications in the technology of rehabilitation of human beings, gathering in a whole studies related not only to Robotics, but also to Biomechanics, Biomimmetics, Cybernetics, among other areas. This book presents a series of researches inspired by this ideal, carried through by various researchers worldwide, looking for to analyze and to discuss diverse subjects related to humanoid robots. The presented contributions explore aspects about robotic hands, learning, language, vision and locomotion

ATRIAS 1.0 & 2.1 : enabling agile biped locomotion with a template-driven approach to robot design

Practical bipedal robots need to be simultaneously efficient, robust, and versatile machines, but designing robots dynamically capable of these demands has been a significant bottleneck. We designed ATRIAS to be a highly dynamic biped capable of both walking and running untethered in real environments. To meet these goals, ATRIAS is designed to approximate dynamically capable locomotion template, i.e. the spring-mass model. We enumerate the challenges of this template-driven design approach and our solutions to make ATRIAS a real-world-viable human-scale machine. We show that ATRIAS exhibits behaviors predicted by spring-mass models in fulfillment of our design approach. Particularly, ATRIAS reproduces the characteristic ground-reaction forces of human walking and running, a key dynamical feature of spring-mass locomotion. We also demonstrate ATRIAS' capacity to walk, hop on one leg, bound like a spring-mass hopper, and recover from an unseen plunge into a 6.5-inch-deep gravel pit. Further, by building efficient spring-mass dynamics into the mechanical system, ATRIAS, when pushed, walks several steps without its actuators replenishing lost mechanical energy. These combined hardware experiments validate ATRIAS' capability as a platform for spring-mass robot controllers and for agile and economical locomotion in general. This thesis is the combination of two journal papers that focus on the ATRIAS robot that focus on statements in the above paragraph. It also includes a summary of the objectives and considerations that went into the design, manufacture and testing phases of the robots. This includes the project deliverables and deadlines, methods for building these robots, control theory considerations for ATRIAS, engineering objectives and questions addressed by this work

Bio-Inspired Robotics

Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field