Locomotion and balance control of humanoid robots with dynamic and kinematic constraints

Building a robot capable of servicing and assisting people is one of the ultimate goals in humanoid robotics. To realize this goal, a humanoid robot first needs to be able to perform some fundamental locomotion tasks, such as balancing and walking. However, simply performing such basic tasks in static, open environments is insufficient for a robot to be useful. A humanoid robot should also possess the ability to make use of the object in the environment to generate dynamic motions and improve its mobility. Also, since humanoid robots are expected to work and live closely with humans, having human-like motions is important for them to be human-friendly. This dissertation addresses my work on endowing humanoid robots with the ability to handle dynamic and kinematic constraints while performing the basic tasks in order to achieve more complex locomotion tasks. First, as a representative case of handling dynamic constraints, a biped humanoid robot is required to balance and walk on a cylinder that rolls freely on the ground. This task is difficult even for humans. I introduce a control method for a humanoid robot to execute this challenging task. In order for the robot to be able to actively control cylinder's motion, the dynamics of the cylinder has been taken into account together with the dynamics of the robot in deriving the control method. Its effectiveness has been verified by full-body dynamics simulation and hardware experiments on the Sarcos humanoid robot. Second, as an example of tasks with kinematic constraints, I present a method for real-time control of humanoid robots to track human motions while maintaining balance. It consists of a standard proportional-derivative tracking controller that computes the desired acceleration to track the given reference motion and an optimizer that computes the optimal joint torques and contact forces to realize the desired acceleration, considering the full-body dynamics of the robot and strict constraints on contact forces. By taking advantage of the property that the joint torques do not contribute to the six degrees of freedom of the floating base, I decouple the computation of joint torques and contact forces such that the optimization problem with strict contact force constraints can be solved in real time. In full-body simulation, a humanoid robot is able to imitate various human motions by using this method. Through this work, I demonstrate that considering dynamic and kinematic constraints in the environment in the design of controllers enables humanoid robots to achieve more complex locomotion tasks, such as manipulating a dynamic object or tracking given reference motions, while maintaining balance.Doctor of Philosoph

Dynamic Walking Models to Understand Asymmetric Gait Characteristics

Passive dynamic walking models remarkably predict gait behaviour such as walk-run transition speeds, preferred step length, stride frequencies and - with the inclusion of springs - ground reaction forces. Muscular or neurological conditions may lead to asymmetric walking characteristics that, in turn, come with long term health risks. Gait analysis may be used to understand an individual patient’s conditions to help rehabilitate them. However, people adapt their kinematic and kinetic walking patterns so it can be hard to distinguish the effects of gait alterations such as inertial imbalance or injury. In this thesis a compass walking model with no active controllers is explored to understand the dynamics of gait. To help us interpret the effects of mass imbalance with a prosthetic foot or orthotic device, asymmetric loading conditions are investigated. A simple spring-mass walking model is used to explore the effects of altered touch-down angles and effective leg stiffness to see if these are used as strategies to alter the characteristics of gait. Results show that an asymmetric touch-down angle alters step length while retaining a symmetric stance time. A hybrid model is then derived with springs to emulate human-like ground reaction forces and asymmetric inertial loading of the legs. Results support previous research that push-off from the trailing leg propels the leg mass more than the body mass. Higher rates of joint forces, larger step lengths and a longer stance time on the residual limb may be due to the prosthetic leg stiffness or the higher location of centre-of-mass. These results help us understand how the dynamic components affect gait characteristics such as step length, stance time and walking speeds. This work is motivated by the needs of persons with disabilities and by the desire to understand human walking

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

Applicable Solutions in Non-Linear Dynamical Systems

From Preface: The 15th International Conference „Dynamical Systems - Theory and Applications” (DSTA 2019, 2-5 December, 2019, Lodz, Poland) gathered a numerous group of outstanding scientists and engineers who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without great effort of the staff of the Department of Automation, Biomechanics and Mechatronics of the Lodz University of Technology. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our event was attended by over 180 researchers from 35 countries all over the world, who decided to share the results of their research and experience in different fields related to dynamical systems. This year, the DSTA Conference Proceedings were split into two volumes entitled „Theoretical Approaches in Non-Linear Dynamical Systems” and „Applicable Solutions in Non-Linear Dynamical Systems”. In addition, DSTA 2019 resulted in three volumes of Springer Proceedings in Mathematics and Statistics entitled „Control and Stability of Dynamical Systems”, „Mathematical and Numerical Approaches in Dynamical Systems” and „Dynamical Systems in Mechatronics and Life Sciences”. Also, many outstanding papers will be recommended to special issues of renowned scientific journals.Cover design: Kaźmierczak, MarekTechnical editor: Kaźmierczak, Mare