In this thesis, the redundancy resolution and failure analysis of Cable-Driven Parallel Manipulators (CDPM) are investigated. A CDPM consists mainly of a Mobile Platform (MP) actuated by cables. Cables can only apply force in the form of tension. So, to design a fully controllable CDPM, the manipulator has to be redundantly actuated (e.g., by using redundant cables, external force/moment or gravity). In this research, the redundancy resolution of planar CDPMs is investigated at the kinematic and dynamic levels in order to improve the manipulator safety, reliability and performance, e.g., by avoiding large tension in the cables that may result in high impact forces, and avoiding large MP velocities that may cause instability in the manipulator, or on the contrary, by increasing the cable tensions and the stiffness for high-precision applications. The proposed approaches are utilized in trajectory planning, design of controllers, and safe dynamic workspace analysis where collision is imminent and the safety of humans, objects and the manipulator itself are at risk. The kinematic and dynamic models of the manipulator required in the design and control of manipulators are examined and simulated under various operating conditions and manufacturing automation tasks to predict the behaviour of the CDPM. In the presented research, some of the challenges associated with the redundancy resolution are resolved including positive tension requirement in each cable, infinite inverse dynamic solutions, slow-computation abilities when using optimization techniques, failure of the manipulator, and elasticity of cables that has a significant role in the dynamics of a heavy loaded manipulator with a large workspace. Optimization-based and non-optimization-based techniques are employed to resolve the redundancy of CDPM. Depending on the advantages and disadvantages of each method, task requirements, the used redundancy resolution technique, and the objective function suitable optimization-based and non-optimization-based routines are employed. Methodologies that could combine redundancy resolution techniques at various levels (e.g., position, velocity, acceleration, and torque levels) are proposed. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2012-09-26 22:39:34.35

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This thesis outlines the evolution of computer hardware and software architectures which are suitable for the programming and control of modular robots and distributed manipulators. Fundamental aspects of automating manufacturing functions are considered and the use of flexible machines, constructed from components of a family of mechanical modules and associated control system elements, are proposed. Many of the features of these flexible machines can be identified with those of conventional industrial robots. However a broader class of manufacturing machine is represented in as much as the industrial user defines the kinematics and dynamics of the manipulator. Such flexible machines can be referred to as "modular robots" or, where the mechanical modules are arranged in concurrently operating but mechanically decoupled groups, as "distributed manipulators". The main body of the work reported centred on the design of a family of computer control system elements which can serve a range of distributed manipulator and modular robot forms. These control system elements, whose cost is commensurate with the size and complexity of the manipulator's mechanical configuration, necessarily have many of the features found in robot controllers but also require properties of reconfigurability, programmability, and control system performance for the considerable array of manipulator configurations which can be constructed.

10th IFAC Symposium on Robot Control International Federation of Automatic Control September 5-7, 2012. Dubrovnik, Croatia

Technology today has progressed to the point that the true potential of robotics is beginning to be realized. However, programming robots to be robust across varied environments and objectives, in a way that is accessible and intuitive to most users, is still a difficult task. There remain a number of unmet needs. For example, many existing solutions today are proprietary, which makes widespread adoption of a single solution difficult to achieve. Also, most approaches are highly targeted to a specific implementation. But it is not clear that these approaches will generalize to a wider range of problems and applications. To address these issues, we define the Interaction Space, or the space created by the interaction between robots and humans. This space is used to classify relevant existing work, and to conceptualize these unmet needs. GTax, a knowledge transfer framework, is presented as a solution that is able to span the Interaction Space. The framework is based on SysML, a standard used in many different systems, which provides a formalized representation and verification. Through this work, we demonstrate that by generalizing across the Interaction Space, we can simplify robot programming and enable knowledge transfer between processes, systems and application domains.

The process of forest harvesting is highly mechanized in most industrialized countries, with felling and processing of trees performed by technologically advanced forestry machines. However, the maneuvering of the vehicles through the forest as well as the control of the on-board hydraulic boom crane is currently performed through continuous manual operation. This complicates the introduction of further incremental productivity improvements to the machines, as the operator becomes a bottleneck in the process. A suggested solution strategy is to enhance the production capacity by increasing the level of automation. At the same time, the working environment for the operator can be improved by a reduced workload, provided that the human-machine interaction is adapted to the new automated functionality. The objectives of this thesis are 1) to describe and analyze the current logging process and to locate areas of improvements that can be implemented in current machines, and 2) to investigate future methods and concepts that possibly require changes in work methods as well as in the machine design and technology. The thesis describes the development and integration of several algorithmic methods and the implementation of corresponding software solutions, adapted to the forestry machine context. Following data recording and analysis of the current work tasks of machine operators, trajectory planning and execution for a specific category of forwarder crane motions has been identified as an important first step for short term automation. Using the method of path-constrained trajectory planning, automated crane motions were demonstrated to potentially provide a substantial improvement from motions performed by experienced human operators. An extension of this method was developed to automate some selected motions even for existing sensorless machines. Evaluation suggests that this method is feasible for a reasonable deviation of initial conditions. Another important aspect of partial automation is the human-machine interaction. For this specific application a simple and intuitive interaction method for accessing automated crane motions was suggested, based on head tracking of the operator. A preliminary interaction model derived from user experiments yielded promising results for forming the basis of a target selection method, particularly when combined with some traded control strategy. Further, a modular software platform was implemented, integrating several important components into a framework for designing and testing future interaction concepts. Specifically, this system was used to investigate concepts of teleoperation and virtual environment feedback. Results from user tests show that visual information provided by a virtual environment can be advantageous compared to traditional video feedback with regards to both objective and subjective evaluation criteria.

The wrench capability of a manipulator is defined as the maximum forces and moments that can be applied (or sustained) by the manipulator. Understanding these kinetostatic performances of a manipulator is crucial in design and control of manipulators. A novel analytical methodology for the determination of the force and moment capabilities of non-redundantly and redundantly actuated planar parallel manipulators is presented. This new methodology is compared to a previous methodology that used optimization and it is shown that the new methodology is computationally more efficient and yields more accurate results. Based on this methodology. five force and moment capability indices are proposed. The proposed indices are used to generate the wrench capabilities of nine different non-redundantly and redundantly actuated planar parallel manipulator architectures.

The subject of this thesis is the design and practical application of a model-based controller with variable structure control (VSC). Robot manipulators are highly non-linear systems, however they form a specific class in the non-linear group. Exact mathematical descriptions of the robot dynamics can be achieved and further, robot manipulators have specific useful properties that can be used for the design of advanced controllers. The inclusion of the inverse dynamic description of the robot manipulator as a feedforward term of the controller (model-based controller) is used to transform two non-linear systems i.e. the controller and the robot, into one linear system. The limitation of this technique arises from the accuracy of the inverse dynamic model. The linearisation only takes place if the model is known exactly. To deal with the uncertainties that arise in the model, a control methodology based on variable structure control is proposed. The design of the controller is based on a Lyapunov approach and engineering considerations of the robot. A candidate Lyapunov function of a pseudo-energy form is selected to start the controller design. The general form of the controller is selected to satisfy the negative definiteness of the Lyapunov function. The initial uncertainties between the actual robot dynamics and the model used in the controller are dealt with using a classical VSC regulator. The deficiencies of this approach are evident however because of the chattering phenomenum. The model uncertainties are examined from an engineering point of view and adjustable bounds are then devised for the VSC regulator, and simulations confirm a reduction in the chattering. Implementation on the SPRINTA robot reveals further limitations in the proposed methodology and the bound adjustment is enhanced to take into account the position of the robot and the tracking errors. Two controllers based on the same principle are then obtained and their performances are compared to a PID controller, for three types of trajectory. Tests reveal the superiority of the devised control methodology over the classic PID controller. The devised controller demonstrates that the inclusion of the robot dynamics and properties in the controller design with adequate engineering considerations lead to improved robot responses.