Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Dr. Ayanna M. Howard; Committee Member: Dr. Charles Kemp; Committee Member: Dr. Magnus Egerstedt; Committee Member: Dr. Patricio Vela. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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

No description available.

A comparison of robotic positional control strategies was done using computer simulation on a three degree-of-freedom manipulator. The manipulator was subjected to different payloads, trajectories at different velocities, varying different controller sample rates and different motor saturation levels. The control schemes studied were the proportional plus integral plus derivative (PID) method, computed torque method, resolved motion rate control (RMRC) method and the model-referenced adaptive control (MRAC) method. These schemes were representative of three categories of robotic positional controllers - Joint Space control, Cartesian Space control and adaptive control. The criteria used for comparison were the maximum trajectory error, the maximum electrical controller. / M.S.

M.S.

In this thesis, forward and inverse kinematic equations are developed for a parallel, closed-loop manipulator known as the Variable Geometry Truss or VGT for short. Widely recognized as adaptive or collapsing structures for space and military applications, VGTs have not received due consideration as robotic manipulators. VGTs undoubtedly represent an important sector of future manipulator applications. VGTs are typically constructed using repeating identical cells or modules and they have exceptional stiffness to weight ratios. The data obtained from solving the forward kinematic equations is used for animation of the VGT. For animation, three dimensional graphics software, graPHIGS is used. Additionally, the kinematic analysis equations are used to map out workspace of the VGT. An experiment is also carried out to verify the computational results. / Master of Science

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.

Vision systems are widely used in robot workcells for sensory feedback. The resolution of a vision system is usually good enough to locate an object so that it can be grasped, but not good enough to accurately locate an insertion hole. Tactile probes are used to accurately locate objects. However, they require a data base containing the approximate location of an object in order to be used effectively. This thesis presents the development of a robot workcell which utilizes a vision system and tactile probe to identify, locate, and orientate two types of circuit board fixtures. The vision system approximately locates the corner points of each fixture in the robot workcell. The tactile system uses the data base created by the vision system to conduct a tactile search for each fixture and to accurately define the coordinates of each corner point. After a fixture is accurately located, a region (sub-coordinate system) is defined about the fixture. The location of each insertion hole within a fixture is defined relative to the region and the robot subsequently inserts the tactile probe into each hole. The vision system developed can define any two dimensional object and can locate the corner points of any straight edged object, whose adjacent sides have an included angle greater than 90 degrees. The tactile system is self calibrating and has a repeatability of 0.009 inches. A probe insertion error analysis was conducted on the system. The average probe insertion error for the system was determined to be 0.0337 inches. In addition, it was determined that probe insertion error increases with the distance between a hole and the origin of its defining region, and that the major source of probe insertion error is the robot language's (AML/E Verion 4.0) inability to accurately define points within a region. / M.S.

The applicability and productivity of industrial robots have been limited partly because of positioning errors. In this thesis, two causes of positioning errors are identified: link deflection and gear transmission errors. Positioning errors due to the effect of link deflection and gear transmission errors are discussed and an iterative scheme is introduced to compute the deflected end-effector position. Validity of the scheme is verified by using Castigliano’s method on the same two-link hypothetical robot. Numerical integration of the integral equations of deflections is compared with analytical integration A correction method is then proposed and an error corrector is constructed. Effectiveness of the error corrector is demonstrated with a hypothetical RRRS robot, a 3-link robot with revolute joints and a spherical hand. / Master of Science