A study on automatic gait parameter tuning for biped walking robots

Automatic gait parameter tuning for biped walking robots is the subject of this thesis. The biped structure is one of the most versatile ones for the employment of mobile robots in the human environment. Their control is challenging because of their many DOFs and nonlinearities in their dynamics. Open loop walking with offline walk pattern generation is one of the methods for walking control. in this method the reference positions of the foot centers with respect to the body center are generated as functionals. Commonly, the tuning process for the trajectory generation is based on numerous trial and error steps. Obviously, this is a time consuming and elaborate process. In this work, online adaptation schemes for one of the trajectory parameters, "z-reference asymmetry", which is used for the compensation of uneven weight distribution of the robot in the sagittal plane, is proposed. In one of the approaches presented, this parameter is tuned online. As an alternative to parameter tuning, a functional learning scheme employing fuzzy identifiers is tested too. Fuzzy identifiers are universal function approximators. Fuzzy system parameters are adapted via back-propagation. An on-line tuning scheme for biped walk parameters however can only be successful if there is sufficient time for training without falling. The training might last hundreds of reference cycles. This implies that a mechanism for keeping the robot in continuous walk, even when the parameter settings are totally wrong, is necessary during training. In this work, virtual torsional springs which resist against deviations of the robot trunk angles from zero, are attached to the trunk center of the biped. The torques generated by the springs serve as the criteria for the tuning and help in maintaining a stable and a longer walk. The springs are removed after training. This novel approach can be applied to a wide range of control systems that involve parameter tuning. 3-D simulation techniques using C++ are employed for the model of a 12-DOF biped robot to test the proposed adaptive method. in order to visualize the walking, simulation results are animated using an OpenGL based animation environment. As a result of the simulations, a functional for the desired parameter, keeping the system in balance while walking, is generated

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

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

Reflex based walking pattern adaptation for biped robots

Employing robots to replace humans in heavy and dangerous tasks is an important research area. Biped robots have advantages in obstacle avoidance and are therefore suitable to work in the human environment in such tasks. However, their control is a very difficult problem because of their nonlinear and unstable nature. Even very small disturbances can lead to instability. Disturbances can vary from slippery ground surfaces to collisions and unexpected contact with the environment to variations in the payload. For dynamically stable robots (walking on two or less feet), constraints on timing and foot placement increase the difficulty of designing controllers that can anticipate changes in the payload or react to errors. This thesis demonstrates the effectiveness of preprogrammed high-level responses to locomotion in a complex dynamic environment. A suite of responses allows a simulated, three dimensional, bipedal robot to recover from falling down due to a sudden change in the payload. Many environment contact errors would be avoided if the control system can respond fast to the errors that have already taken place and adapt the biped locomotion. In the case of the biped robot considered in this work, the controller might have less than a few tenths of a second in which to choose or plan an appropriate recovery. In this thesis reflexes are defined as responses with no explicit modeling and limited sensing. That is the robot can detect the payload change and makes no attempt to estimate the properties of the load to calculate a corresponding recovery plan. These reflexes are defined at high level because they involve changes of the biped body configuration and trajectory. Sensing elements are used just to detect the error and trigger the reflex. Explicit dynamic modeling of the biped robot is complicated and the controller cannot use it to compute precise and appropriate reactions. In addition, accurate and precise information on load addition is not available to the controller. The method presented changes the walk trajectory and shifts the center of gravity to keep the balance of the walk. Thereafter, the original trajectory is brought back by a smooth trajectory interpolation function. The reflex-adaptation technique considered is tested for a variety of payloads at different loading times. The method shows a good functionality by recovering the biped and allowing stable and balanced original walking pattern. The approach is successful and is a candidate for real applications

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

BIPED GAIT GENERATION FOR HUMANOID DYNAMIC WALKING

Ph.DDOCTOR OF PHILOSOPH

Design and control of a teleoperation system for humanoid walking

Master'sMASTER OF ENGINEERIN