Actuation Design Methodology for Haptic Interfaces and Rehabilitation Systems

This paper introduces a methodology and a software framework intended to optimize and speed up the design process of a haptic interface or a rehabilitation system. Starting from an initial mechanical design the procedure allows to export the kinematic and dynamic properties of the robotic system in a simulation environment. The software receives as additional input the Cartesian or joints trajectories and generates as output the required torques at the joints. From the recorded measurements the program extracts the torque ranges necessary to choose a suitable actuation system for the robot. The possibility to run the simulation in batch modality allows also to define different optimization techniques that may be used to reduce the overall system weight or increase its payloa

Modular and Analytical Methods for Solving Kinematics and Dynamics of Series-Parallel Hybrid Robots

While serial robots are known for their versatility in applications, larger workspace, simpler modeling and control, they have certain disadvantages like limited precision, lower stiffness and poor dynamic characteristics in general. A parallel robot can offer higher stiffness, speed, accuracy and payload capacity, at the downside of a reduced workspace and a more complex geometry that needs careful analysis and control. To bring the best of the two worlds, parallel submechanism modules can be connected in series to achieve a series-parallel hybrid robot with better dynamic characteristics and larger workspace. Such a design philosophy is being used in several robots not only at DFKI (for e.g., Mantis, Charlie, Recupera Exoskeleton, RH5 humanoid etc.) but also around the world, for e.g. Lola (TUM), Valkyrie (NASA), THOR (Virginia Tech.) etc.These robots inherit the complexity of both serial and parallel architectures. Hence, solving their kinematics and dynamics is challenging because they are subjected to additional geometric loop closure constraints. Most approaches in multi-body dynamics adopt numerical resolution of these constraints for the sake of generality but may suffer from inaccuracy and performance issues. They also do not exploit the modularity in robot design. Further, closed loop systems can have variable mobility, different assembly modes and can impose redundant constraints on the equations of motion which deteriorates the quality of many multi-body dynamics solvers. Very often only a local view to the system behavior is possible. Hence, it is interesting for geometers or kinematics researchers, to study the analytical solutions to geometric problems associated with a specific type of parallel mechanism and their importance over numerical solutions is irrefutable. Techniques such as screw theory, computational algebraic geometry, elimination and continuation methods are popular in this domain. But this domain specific knowledge is often underrepresented in the design of model based kinematics and dynamics software frameworks. The contributions of this thesis are two-fold. Firstly, a rigorous and comprehensive kinematic analysis is performed for the novel parallel mechanisms invented recently at DFKI-RIC such as RH5 ankle mechanism and Active Ankle using approaches from computational algebraic geometry and screw theory. Secondly, the general idea of a modular software framework called Hybrid Robot Dynamics (HyRoDyn) is presented which can be used to solve the geometry, kinematics and dynamics of series-parallel hybrid robotic systems with the help of a software database which stores the analytical solutions for parallel submechanism modules in a configurable and unit testable manner. HyRoDyn approach is suitable for both high fidelity simulations and real-time control of complex series-parallel hybrid robots. The results from this thesis has been applied to two robotic systems namely Recupera-Reha exoskeleton and RH5 humanoid. The aim of this software tool is to assist both designers and control engineers in developing complex robotic systems of the future. Efficient kinematic and dynamic modeling can lead to more compliant behavior, better whole body control, walking and manipulating capabilities etc. which are highly desired in the present day and future robotic applications

The Development of a Multi-arm Mobile Robot System for Nuclear Decommissioning Applications.

This PhD thesis is based in the field of robotics and introduces a case study of the design and development of a multi-arm mobile robot system for nuclear decommissioning (MARS-ND). A key premise underlying the research was to develop intelligence in the robot that is similar to the cooperation and communication between the human brain and its two arms; hence the human body was adopted as the starting point to establish the size and functionality of the proposed system. The approach adopted for this research demonstrates the development, integration and configuration of a multi-arm robot system which consists of two human armlike off-the-shelf manipulators whose joints are controlled using potentiometer sensors and hydraulic actuators. Using the manipulators' sensor feedback, a wide variety of complex tasks found in the rapidly expanding field of nuclear decommissioning can be undertaken. The thesis also considers the issue of collaboration, collision detection and collision avoidance between the two arms of MARS-ND. As part of the final stage of this research the author participated in a collaborative research project with the Sugano Laboratory at Waseda University, Tokyo, Japan. The three major research issues addressed in this thesis are: 1. The selection and integration of off-the-shelf hardware in the development of MARS-ND using the latest technology available for robotic systems 2. The creation of a suitable control system for the robot arms; and the building of an advanced, user-friendly interface between the robot system and the host computer 3. The investigation and implementation of collaboration, coordinated motion control and collision detection & avoidance techniques for the robot arms The hardware and software integration for the whole robotic system is explained with the proposed software architecture and the use of National Instruments (NI) functions and tools to control the movement of the arm joints and the performance of a selected decommissioning task. This thesis also examines the operational software applied within the research through its discussion of four interlinked areas: 1. The control software and hardware interface for the MARS-ND and the controller architecture 2. The application of an NI Compact FieldPoint controller and FieldPoint I/O modules to facilitate wireless communication between the Multi-Arm Mobile Robot system and the user interface in the host PC 3. The use of Measurement and Automation Explorer (MAX) and LabVIEW software tools for calibration and the building of user interfaces required for sending and receiving the signals needed to control the robot arm joints accurately 4. The application of a PID toolkit in LabVIEW for the design of a simple PID controller for the individual arm joints with a potentiometer sensor fitted inside each joint in order to provide a feedback signal to the controller The thesis concludes that MARS-ND is a good example of a robotic system specifically designed for hazardous nuclear decommissioning applications. It demonstrates the complexity of such a system from a number of aspects such as the need for mobility, control, sensor and system design, and integration using modem tools that are available off-the-shelf. In addition the use of these modern tools allows a single mechatronics engineer to design, integrate, interface and build a motion control system for MARS-ND as compared to the traditional way of building a similar robot by a team of specialised engineers. The contribution this research makes to the design and building of multi-arm robot system for nuclear decommissioning industry concerns its size and mobility using a mobile platform to transport the multi-arm robot system. In addition links have been made between Lancaster University and Waseda University in the context of the development of multi-arm robot systems

Robot Manipulators

Robot manipulators are developing more in the direction of industrial robots than of human workers. Recently, the applications of robot manipulators are spreading their focus, for example Da Vinci as a medical robot, ASIMO as a humanoid robot and so on. There are many research topics within the field of robot manipulators, e.g. motion planning, cooperation with a human, and fusion with external sensors like vision, haptic and force, etc. Moreover, these include both technical problems in the industry and theoretical problems in the academic fields. This book is a collection of papers presenting the latest research issues from around the world