A Pragmatic Approach to Exploiting Full Force Capacity for Serial Redundant Manipulators

Considering a set of robotic tasks which involve physical interaction with the environment, the theoretical knowledge of the full force capacity of the manipulator is a key factor in the design or development of an efficient and economically attractive solution. Carrying its own weight while countering forces may be too much for a robot in certain configurations. Kinematic redundancy with regard to a task allows a robot to perform it in a continuous space of articular configurations; space in which the payload of the robot may vary dramatically. It may be impossible to withstand a physical interaction in some configurations, while it may be easily sustainable in others that bring the end-effector to the same location. This becomes obviously more prevalent for a limited payload robot. This letter describes a framework for these kind of operations, in which kinematic redundancy is used to explore the full extent of a force capacity for a givenmanipulator and task (in this letter, the terms “force” and “wrench” may interchangeably refer to two-, three-, or six-dimensional forces depending on the dimension of the problem and on whether they may or may not include components of translational forces and/or moments. Their dimensional definition will be explicitly given whenever specifically needed). A pragmatic force capacity index (FCI) is proposed. The FCI offers a sound basis for redundancy resolution via optimization or complete redundancy exploration, and may provide good hints for end-effector design. A practical use case involving 7-DOFs KUKA LBR iiwa was used to demonstrate the relevance of the proposed method

On Increasing the Automation Level of Heavy-Duty Hydraulic Manipulators with Condition Monitoring of the Hydraulic System and Energy-Optimised Redundancy Resolution

Hydraulic manipulators on mobile machines are predominantly used for excavation and lifting applications at construction sites and for heavy-duty material handling in the forest industry due to their superior power-density and rugged nature. These manipulators are conventionally open-loop controlled by human operators who are sufficiently skilled to operate the machines. However, in the footsteps of pioneering original equipment manufacturers (OEMs) and to keep up with the intensifying demand for innovation, more and more mobile machine OEMs have a major interest in significantly increasing the automation level of their hydraulic manipulators and improving the operation of manipulators. In this thesis, robotic software-based functionalities in the form of modelbased condition monitoring and energy-optimal redundancy resolution which facilitate increased automation level of hydraulic manipulators are proposed.A condition monitoring system generally consists of software modules and sensors which co-operate harmonically and monitor the hydraulic system’s health in real-time based on an indirect measure of this system’s health. The premise is that when this condition monitoring system recognises that the system’s health has deteriorated past a given threshold (in other words, when a minor fault is detected, such as a slowly increasing internal leakage of the hydraulic cylinder), the condition monitoring module issues an alarm to warn the system operator of the malfunction, and the module could ideally diagnose the fault cause. In addition, when faced with severe faults, such as an external leakage or an abruptly increasing internal leakage in the hydraulic system, an alarm from the condition monitoring system ensures that the machine is quickly halted to prevent any further damage to the machine or its surroundings.The basic requirement in the design of such a condition monitoring system is to make sure that this system is robust and fault-sensitive. These properties are difficult to achieve in complex mobile hydraulic systems on hydraulic manipulators due to the modelling uncertainties affecting these systems. The modelling uncertainties affecting mobile hydraulic systems are specific compared with many other types of systems and are large because of the hydraulic system complexities, nonlinearities, discontinuities and inherently time-varying parameters. A feasible solution to this modelling uncertainty problem would be to either attenuate the effect of modelling errors on the performance of model-based condition monitoring or to develop improved non-model-based methods with increased fault-sensitivity. In this research work, the former model-based approach is taken. Adaptation of the model residual thresholds based on system operating points and reliable, load-independent system models are proposed as integral parts of the condition monitoring solution to the modelling uncertainty problem. These proposed solutions make the realisation of condition monitoring solutions more difficult on heavy-duty hydraulic manipulators compared with fixed-load manipulators, for example. These solutions are covered in detail in a subset of the research publications appended to this thesis.There is wide-spread interest from hydraulic manipulator OEMs in increasing the automation level of their hydraulic manipulators. Most often, this interest is related to semi-automation of repetitive work cycles to improve work productivity and operator workload circumstances. This robotic semi-automated approach involves resolving the kinematic redundancy of hydraulic manipulators to obtain motion references for the joint controller to enable desirable closed-loop controlled motions. Because conventional redundancy resolutions are usually sub-optimal at the hydraulic system level, a hydraulic energy-optimised, global redundancy resolution is proposed in this thesis for the first time. Kinematic redundancy is resolved energy optimally from the standpoint of the hydraulic system along a prescribed path for a typical 3-degrees-of-freedom (3-DOF) and 4-DOF hydraulic manipulator. Joint motions are also constrained based on the actuators’ position, velocity and acceleration bounds in hydraulic manipulators in the proposed solution. This kinematic redundancy resolution topic is discussed in the last two research papers. Overall, both designed manipulator features, condition monitoring and energy-optimised redundancy resolution, are believed to be essential for increasing the automation of hydraulic manipulators

Advanced Strategies for Robot Manipulators

Amongst the robotic systems, robot manipulators have proven themselves to be of increasing importance and are widely adopted to substitute for human in repetitive and/or hazardous tasks. Modern manipulators are designed complicatedly and need to do more precise, crucial and critical tasks. So, the simple traditional control methods cannot be efficient, and advanced control strategies with considering special constraints are needed to establish. In spite of the fact that groundbreaking researches have been carried out in this realm until now, there are still many novel aspects which have to be explored

Sterno-clavicular kinematics : a new measurement system

PhD ThesisThe study of the human motion as a discipline is ancient almost like the man. Early theories and observations on these topics can be found in Hyppocrates' and Galeno's work. More recently Duchenne de Boulogne (1867), Marey (1885), Braune and Fisher (1888), Sherrington (1933), Luria and finally Haken (1996) applied new techniques to the study of movement trying to understand and localise also the main areas of the brain involved during motion. Despite the richness of the literature produced, "man in motion" still represents a fascinating and partially unknown theme to deal with, particularly in the dynamic behaviour of the arms during the execution of specific tasks. Such movement, indeed individual expression of the complex interaction of biological subsystems (brain, muscles, skeleton, etc. ) against the surrounding environment, hides nowadays its features and very few data are available on its kinematic and dynamic response. This gap is largely due to the lack of knowledge on the dynamic movement of the "shoulder complex" and of the related muscles involved during motion. In fact, the large number of degrees of freedom to be measured and the high deformability of skin and soft tissues prevent the direct measurement of skeletal movements and contribute to increment the above described indetermination. Against this complex background, the rehabilitationist faces the pragmatic difficulties to decide which joints require attention as a priority or, in the case of biological damage, to assess the degree of impairment and subsequent recovery. As a result, clinical assessmentis performed by the use of relatively elementary test tasks, which can be monitored either by timing or by some indirect measurement of the success of the execution. The aim of the present research is then to provide new means of measurements to be used for gaining objective information on the motion particularly of "non visible" joints like the shoulder complex in order to characterise properly their motion and, in turn, the workspace of the arm