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Some relevant aspects of dynamics and control of heavy-duty hydraulic machines in a teleoperated mode were investigated. These machines, such as excavators and forest harvesters, are mostly used in primary industries. They have a manipulator-like structure with a nonlinear and coupled actuating system. The aim of the project is to investigate different approaches towards converting such machines, with minimum changes, into task-oriented human-supervisory control systems. This provides the opportunity to use both human supervision and robotic power in hazardous environments and for tasks for which human decision is necessary. A methodology was developed for fast and accurate simulations. Analytical, steady-state and numerical techniques were combined using Large-Scale Systems analysis. The inclusion of nonlinearities in the form of discontinuities (e.g., gear backlash and stick-slip friction) in the model was investigated. Numerical simplifications of the structural dynamics and alternative solutions for the hydraulic part were also studied. The model describing the performance of the machine has been written in ACSL (Advanced Continuous Simulation Language) on a VAX computer system. A modified version of the program is at present running close to real-time on a single processor in conjunction with high speed graphics in a manner similar to a flight simulator used for human interface studies and training. The model also evaluates the performance of the machine in a teleoperated mode and under different control strategies. As a result a velocity control algorithm has been developed which is applied in conjunction with the closed-loop components for teleoperation of heavy-duty hydraulic machines; it is basically a feedforward compensation which uses the measured hydraulic line pressures along with fluid-flow equations as criteria to control the joint velocities as well as to uncouple the interconnected actuating system. The control algorithm has been written in C language and is running on an IRONICS computer system, interfaced between the human operator and the machine. The simulation results are supported by the experimental evidence. The experiments were performed on a Caterpillar 215B excavator. Improved operator safety, extension of human capability, job quality and productivity increase are the advantages of a successful implementation of robotic technology to these industrial machines. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Novel algorithms in robot inverse kinematics and path planning are proposed. Emphasis is placed on real-time execution speed with multiprocessors and adaptability to unpredictable environments. The inverse kinematics algorithm is an iterative solution which is applicable to many classes of industrial robots, and is stable at and around singularities. The method is based on a simple functional analysis of each link of a manipulator and projecting vectors on the coordinate frame of each joint. Heuristic rules are used to control a mobile manipulator base and to guide the manipulator in the case of non-convergence caused by joint limits. The path planning algorithm uses a potential surface in a quantized configuration space. Paths are guaranteed to be collision-free for all parts of the robot. Local minimum regions on the potential surface are filled on demand by extending the obstacles. Arbitrarily shaped obstacles in 3-dimensions can be handled. Using a hierarchical collision detection technique, high execution speed can be maintained even with many complex shaped obstacles in the workspace. The path planning method can theoretically be applied to any manipulator with any degrees of freedom. The implementation of the inverse kinematics and path planning algorithms in a parallel hierarchical multiprocessor computer structure designed for the control of robots is proposed and investigated. Communication among the processors is by point-to-point message passing via asynchronous serial links with message buffers. Computer simulations are used to demonstrate the appropriateness and feasibility of this computer structure for robot control. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

With the current interest in the control of robots, the need for an industrial robot as a research tool has become preeminent. This thesis presents the concepts and the design for a microprocessor based development system for the P-50 Process Robot, in an effort to convert it into a Robot Control Development System. Various control philosophies were reviewed to arrive at a hierarchical control structure that provides maximum flexibility and control over every degree of freedom of the robot arm. The working of the original controller of the P-50 robot was studied in detail to facilitate design of interface circuits that transfer control of the arm to the augmented controller. All the hardware required for the controller was designed and tested. Guidelines for developing the software as well as schematics for constructing the remaining hardware circuits, are provided. The conclusion discusses modifications that could be made to this design and instructions for using the fully developed controller. / M.S.

Call number: LD2668 .T4 1985 S648 / Master of Science

In poultry plants in the United States, a water chiller is used to chill WOGs (de-feathered birds without giblets). After exiting the chiller these birds are manually transferred from a conveyor belt to shackles for further processing. The current process is less than ideal. The labor pool for jobs such as these is continuing to shrink and labor turnover is a constant problem. The rates of repetitive motion injury reported are high and are continuing to rise. In addition, many poultry producers see this as a bottleneck in the process. Automation has the potential to alleviate these problems. The high variability of this task, cost restrictions, and special design considerations associated with meat handling equipment make automation of this task challenging. Industrial robots have traditionally been limited to tasks with low variability. This task has high variability. They are presented on the conveyor belt in a wide variety of positions and orientations. Most robotic automation systems consist of a commercially available industrial robot, a specialized end effector and a control scheme. The economics of this task prohibit the use of a commercially available industrial robot, as there are no industrial robots on the market that will offer a short enough payback. Robots have not yet been adapted to meat handling processes, and existing robotic designs are not well suited to the task. In designing a low cost, high-speed robot for poultry processing the requirements of the robot are defined and a variety of robot architectures, constructions, and materials are explored. Simple modifications to the existing shackle and conveyor setup to make the task easier for a robot are also explored. After the robot requirements are defined a large group of possible designs are developed. The possible designs are systematically evaluated and/or eliminated until a single design is selected. The forward and reverse kinematics for this robot are developed. A singularity analysis is carried out. A proof of concept model is built. A prototype is modeled and a dynamic analysis of that prototype is carried out. The design is finalized based on the results of the dynamic analysis.

At a platform singularity, a parallel manipulator loses constraint. Adding redundant actuation in an existing leg or new leg can eliminate these types of singularities. However, redundant manipulators have been designed with little attention to frame invariant techniques. In this dissertation, physically meaningful measures for closeness to singularities in non-redundant manipulators are developed. Two such frameworks are constructed. The first framework is a constrained optimization problem that unifies seemingly unrelated existing measures and facilitates development of new measures. The second is a clearance propagation technique based on workspace generation. These closeness measures are expanded to include redundancy and thus can be used as objective functions for designing redundant actuation. The constrained optimization framework is applied to a planar three degree of freedom redundant parallel manipulator to show feasibility of the technique.