Skip to main content
main-content

Über dieses Buch

Introducing mobile humanoid robots into human environments requires the systems to physically interact and execute multiple concurrent tasks. The monograph at hand presents a whole-body torque controller for dexterous and safe robotic manipulation. This control approach enables a mobile humanoid robot to simultaneously meet several control objectives with different pre-defined levels of priority, while providing the skills for compliant physical contacts with humans and the environment.

After a general introduction into the topic of whole-body control, several essential reactive tasks are developed to extend the repertoire of robotic control objectives. Additionally, the classical Cartesian impedance is extended to the case of mobile robots. All of these tasks are then combined and integrated into an overall, priority-based control law. Besides the experimental validation of the approach, the formal proof of asymptotic stability for this hierarchical controller is presented. By interconnecting the whole-body controller with an artificial intelligence, the immense potential of the integrated approach for complex real-world applications is shown. Several typical household chores, such as autonomously wiping a window or sweeping the floor with a broom, are successfully performed on the mobile humanoid robot Rollin’ Justin of the German Aerospace Center (DLR).

The results suggest the presented controller for a large variety of fields of application such as service robotics, human-robot cooperation in industry, telepresence in medical applications, space robotics scenarios, and the operation of mobile robots in dangerous and hazardous environments.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
The robotics research in the recent past has led to the development of an increasing number of mobile humanoid robots. They can be employed in a great diversity of applications such as service robotics, the cooperation with humans in industry, or the autonomous operation in hazardous areas where humans would be in danger. All of these use cases involve dynamic, unpredictable, and partially unstructured environments, where physical contacts are inevitable and actually necessary for the task completion. The high requirements on the humanoid robots urge the designers to develop suitable whole-body control techniques in order to properly operate the systems.
Alexander Dietrich

Chapter 2. Fundamentals

Abstract
This chapter briefly reviews the basics that are required for the theoretical investigations and the practical implementations in this monograph. That comprises fundamentals in kinematics and dynamics (Sect. 2.1), active control for compliant interaction behavior (Sect. 2.2), and details on the hardware and modeling assumption on the wheeled humanoid robot Rollin’ Justin, which has been chosen as the platform for the experimental validations (Sect. 2.3).
Alexander Dietrich

Chapter 3. Control Tasks Based on Artificial Potential Fields

Abstract
Robots with a large number of actuated DOF are able to perform several control tasks simultaneously. Holding a glass of water in a particular position and orientation in space, for example, requires six DOF. If there are more DOF available, this remaining kinematic redundancy can be used to pursue further important objectives such as collision avoidance, observation of the environment, or pose optimization for increased energy efficiency.
Alexander Dietrich

Chapter 4. Redundancy Resolution by Null Space Projections

Abstract
Robots with many DOF and several simultaneous objectives necessarily require a redundancy resolution. In most state-of-the-art approaches, one solves optimization problems for a hierarchical arrangement of the involved tasks. The highest-priority task is executed employing all capabilities of the robotic system. The second-priority task is then performed in the null space of this highest-priority task. In other words, the task on the second level is executed as well as possible without disturbing the first level. The task on level three is then executed without disturbing the two higher-priority tasks, and so forth.
Alexander Dietrich

Chapter 5. Stability Analysis

Abstract
This chapter covers the aspect of stability in multi-objective whole-body impedance control. That involves both theoretical stability analyses and the experimental validation of the developed concepts.
Alexander Dietrich

Chapter 6. Whole-Body Coordination

Abstract
As a result of intensive research over the last decades, several robotic systems are approaching a level of maturity that allows robust task execution and safe interaction with humans and the environment. Besides humanoid robots such as ASIMO [SWA+02], Robonaut 2 [DMA+11], or HRP-4 [KKM+11], a variety of wheeled systems has been developed, e.g. Rollin’ Justin [BWS+09], ARMAR-III [ARS+06], TWENDY-ONE [IS09], PR2 [BRJ+11]. Regardless of the specific structure of the system, the requirement of handling several objectives simultaneously is a common property for robotic applications in these dynamic and often unstructured environments. The features range from precise task execution, collision avoidance, and the compliance with physical constraints, to objectives such as maintaining the manipulability or the realization of desired postures.
Alexander Dietrich

Chapter 7. Integration of the Whole-Body Controller into a Higher-Level Framework

Abstract
This chapter serves as an outlook to prospective challenges in robotics, where compliant whole-body control will act jointly with an Artificial Intelligence (AI). The field of service robotics, for example, puts high requirements on the systems due to the complexity of household chores: The environment is usually dynamic and unstructured, and a wide variety of tools with different contact properties exists. These aspects require an elaborate task planning, both from a logical and a geometric perspective. Moreover, the close cooperation of all modules in a robotic system is necessitated: A whole-body controller for soft physical contacts requires a proper parameterization, i.e. controller gains, a specified control task hierarchy, trajectories and goals, to perform the tasks. A non-deterministic, AI-based planner can provide these data while not necessarily being hard-real-time-capable itself. In case of local minima on the control level, the planner is able to reschedule to find feasible, global solutions. Other modules such as the vision system or the speech recognition may also be triggered.
Alexander Dietrich

Chapter 8. Summary

Abstract
The steady progress in humanoid robotics has recently generated impressive systems with a large number of actuated degrees of freedom. Consequently, that gave a strong impetus to research activities related to the whole-body control of this newly available class of mobile robots. The demand arises from various fields of application as sketched in Fig. 8.1. Industrial use cases are very relevant since robotic systems can be employed to perform dangerous and harmful tasks, or they could assist factory workers and cooperate with them. Another field concerns hazardous environments such as in space missions, deep see exploration, or disasters in nuclear reactors, e.g. Chernobyl or Fukushima Daiichi. Further applications are encountered in the emerging field of service robotics. Even simple household chores such as washing the dishes require a lot from the robotic systems because the considered environment is often dynamic, unstructured, and difficult to predict due to the presence of human beings.
Alexander Dietrich

Backmatter

Weitere Informationen