The study of robotics cannot be satisfactorily pursued without access to working robots. The inexpensive Rhino robot arm is one that academic institutions can easily obtain for educational purposes. This thesis presents a new controller that replaces the original Rhino controller, which in many ways was not suited, or was too limited, for experimentation. A comparison of the old and new controllers is given, but the primary purpose of this thesis is to provide complete details of the new controller, and its use. The conclusion discusses the performance of the new controller and areas of experimentation to which it might be applied. / Master of Science

The Control System Analysis and Design Package (CSADP) is a computer-aided design package for applying classical control system analysis and design tools to experimental frequency response measurements. CSADP allows the user to analyze and manipulate measured frequency response data, design control systems using these measurements, and determine the operational amplifier hardware required to implement the design. To perform these tasks, CSADP provides tools that allow the user to define problems using both frequency response data files and transfer function descriptions; generate Bode, Nyquist, and root-locus plots; and curve-fit frequency response data. The curve-fitting program uses novel data-scanning techniques for conditioning the data, and for predicting the model form and starting parameters. CSADP also allows the user to design compensators interactively using Bode and root-locus methods, and aids the user in selecting the required resistor and capacitor values needed for implementing the compensator using op-amp circuits. In addition, CSADP provides coefficients required to implement the compensator using selected digital algorithms. CSADP was used in the design of a velocity loop compensator for a precision diamond turning machine. Open loop frequency response data gathered from the machine was used as the basis for compensator design using Bode methods. The required compensator coefficients generated by the program were programmed into the servo for testing. Results showed that the closed loop response predicted by the program accurately matched the measured response. Estimates of natural frequencies provided by the model prediction program were within 5 percent of the actual values. Errors in estimates of the damping ratios for very lightly damped complex poles ranged from only 10 percent to 30 percent. CSADP is written in FORTRAN 77 and provides Tektronix (TEK) 4010/4014 compatible graphics output. / Master of Science

The overall purpose of this research is to develop a real-time ultrasound based system for controlling robotic weld quality by monitoring the weld pool. The concept of real-time weld quality control is quite broad, and this work focuses on weld penetration depth monitoring and control with laser ultrasonics. The weld penetration depth is one of the most important geometric parameters that define the weld quality, hence remains a key control quantity. This research focuses on the implementation and optimization of the laser phased array generation unit and the development of signal analysis algorithms to extract the weld penetration depth information from the received ultrasonic signals. The system developed is based on using the phased array technique to generate ultrasound, and an Electro-Magnetic Acoustic Transducer (EMAT) as a receiver. The generated ultrasound propagates through the weld pool and is picked up by the EMAT. A transient FE model is built to predict the temperature distribution during welding. An analytical model is developed to understand the propagation of ultrasound during real-time welding and the curved rays are numerically traced. The cross-correlation technique has been applied to estimate the Time-of-Flight (ToF) of the ultrasound. The ToF is then correlated to the measured weld penetration depth. The analytical relationship between the ToF and penetration depth, obtained by a ray-tracing algorithm and geometric analysis, matches the experimental results. The real-time weld sensing technique developed is efficient and can readily be deployed for commercial applications. The successful completion of this research will remove the major obstacle to a fully automated robotic welding process. An on-line welding monitoring and control system will facilitate mass production characterized by consistency, high quality, and low costs. Such a system will increase the precision of the welding process, resulting in quality control of the weld beads. Moreover, in-process control will relieve human operators of tedious, repetitive, and hazardous welding tasks, thus reducing welding-related injures.