Behnam Bahr

A real-time scheme of cubic parametric curve interpolations for CNC systems

Abstract In this paper, the popular finite forward differencing algorithm for fast evaluation of points on a cubic parametric curve is modified for its application to CNC systems so that the inherent accumulative error in the calculation of one piece of curve will not propagate to the whole composite curve. Using specified tolerances, a computationally non-intensive method of analysis for the computation of step size has been developed. Tolerance, velocity, acceleration and jerk analyses are conducted based on computer simulation results. The interpolation scheme method developed in this paper has been analyzed and proven to be accurate, adaptive to the curvature of a curve, reduces jerk, and can be easily implemented in CNC systems. Finally, the paper explains why the algorithm developed here is natural for cubic parametric curve interpolations.

Sensory guidance of seam tracking robots

The primary goal of a seam tracking robot, based on sensory feedback, is to maintain a prescribed relationship between the end effector and the workpiece throughout the whole motion of the manipulator along the nominal path. The purpose of this article is to present the essential conceptual and theoretical features of a high-speed seam tracking controller for sealant application. The general system configuration is discussed, followed by a brief account of the key aspects involved with the sensing of the seam location and subsequent correction command generation for the guidance of the robot. The theoretical considerations are followed by a detailed account of the physical implementation of the proposed system, with performance evaluation data obtained under actual working conditions.

Automated tool monitoring system using vision system for a robotic cell

Abstract Unattended machining of manufacturing parts is not attainable without the assistance of some type of automated tool monitoring capabilities. This paper describes the elements of an integrated manufacturing cell consisting of a vision system and a robot equipped with a drill. The vision system has a two-fold function: tool monitoring and part recognition. The developed algorithms and methodology for tool monitoring have been described with actual results of a drilling operation. In addition, a summary of the part recognition procedure is also included.

Effects of Slugger Drill Bits in Drilling of Composites

One of the problems in machining of composites is related with the fibers as reinforcement, due to their abrasiveness, causing fast tool wear and deterioration of machined surface. Among all the damages that can occur in the drilling of a composite plate, delamination is the most serious, as it can cause loss of mechanical strength of laminate plates. The main mechanism responsible for delamination is the axial thrust force exerted by the stationary center of the drill – chisel-edge – whose action is more similar to an extrusion that to a drilling. It can be shown that 40% to 50% of the thrust force is because of the chisel edge. Therefore, in this paper a new set of hollow drill bits is introduced and tested on the composite materials with different properties and drilled hole quality mainly, surface roughness, roundness, hole oversize and delamination investigated. With these hollow drill bits we were able to achieve lower thrust forces. Also drill bit geometry changed to be optimized for the best hole quality.Copyright

Fuzzy compensated computed torque control of a manipulator

A great deal of research has been done in fuzzy logic control (FLC) and its applications since Mamdanis pioneering papers in 1974 and 1977. FLC has also been applied to manipulator control which is a very challenging nonlinear control problem. Both classical and advanced robot controllers have problems because of high nonlinearity or uncertainties in robot dynamics. FLC, as an alternate, suffer from lack of analytical methods for design, tuning and stability analysis. A nonlinear controller which is robust in the presence of modeling errors and disturbances is presented in this paper. A computed torque controller can be designed based on an approximate model and FLC can be used to minimize the tracking error due to modeling errors and disturbance. Since the approximate model of the system reduces the overall nonlinearity, FLC works with very simple rules and it is easy to tune.

Microcomputer-based optical sensor for seam tracking robot

Abstract A continuous path robot used in welding or sealant spreading requires a sensor to detect the exact seam path of the object. This paper is to illustrate the principle of an innovative optical sensor designed to guide a robot in this type of application. A linear array detector served as the measuring device to provide lateral, vertical, and singular deviations of the seam path in real-time. This information was converted into robot control commands by a multiprocessor computer system to minimize the path following errors. Finally, the robotic system equipped with this sensing device was tested and the performance was evaluated.

Safety and Survivability Analysis of a Wall-Climbing Robot

In this paper, an explanation of the need for the climbing robot is given first. Second, a safety analysis is performed to illustrate how the robot is guarded against falling. This safety analysis is used to determine the design forces required on the suction cups that hold the robot in place. Finally, a survivability analysis was done to show that the robot can withstand a drop from a height of 1.3 meters if it were to fall. If the robot does fall, it would be desirable to minimize the amount of damage on the equipment mounted on the robot. The method presented in this paper proposes to swing the arms of the robot into the direction of the impact, using them to absorb the majority of the impact energy. For analysis of the fall protection system, a multibody model was developed to simulate its dynamics during a fall.

Development of decision support knowledge based system for tool wear diagnosis

Abstract This paper deals with the problems faced by small and medium sized metal cutting industries, with the perspective of tool monitoring. In a small or medium size metal cutting industry employing major metal cutting process, one of the primary problem is that of tool monitoring and wear diagnosis. The problem is of immediate concern especially in those industries where the processes or operations employed are flexible and production depends entirely on orders from customers. Due to a flexible manufacturing setup, almost all major metal cutting processers need to be carried out. However, it becomes increasingly difficult for such small or medium size metal cutting industries to employ skilled manpower for each operation as well as expert technicians to supervise the operation, and carry out fault diagnosis and tool monitoring. Also, the problem associated with tool monitoring is that human operator carrying out the monitoring has to rely either on observation such as ceasing of tool, rise in temperature, generation of fumes, noisy operation, vibrations, considerable change in shape etc, or by monitoring the quality of the finished product. Also, there can be instances where the operator does notice a symptom but does not have the expertise to identify the cause of the trouble. Errors in tool monitoring can lead to considerable damage both to the machine as well as the workpiece. On the other hand, if the tool is replaced before it reaches its useful life expectancy, it leads to unnecessary additional cost. A Decision Support Knowledge Based System (DSKBS) has therefore been developed in this paper with the above considerations. The DSKBS provides the user with a friendly environment to diagnose a particular tool wear and obtain the necessary repair or replacement instructions. The goal is to increase productivity, decrease cost of operation and enhance total quality and reliability of the operation.

A simulation system for a surface climbing robot

Abstract In order to reduce the cost of designing a new mechanism, it is desirable to use a simulation system that is able to provide a realistic representation of motions of the newly designed mechanism before actually manufacturing it. The modern computer graphics techniques have made it possible to realize this kind of simulation system. In this paper a simulation system with 2-D and 3-D was developed for design of a surface climbing robot with two legs, which can be used for inspections of nuclear power plants, ships, storage tanks, aircraft and tall buildings. This simulation/animation system was written in AutoLISP and implemented in a personal computer equipped with AutoCAD.

Design of a Wall-Scaling Robot for Inspection and Maintenance

This paper describes the design of a new wall-scaling robot for the inspection and maintenance of various structures, such as aircraft, or nuclear power plants is. This robot is capable of climbing straight or curved surfaces in two directions, up/down or left/right in strokes of 55 millimeters. The load carrying capability of this robot is about 100 kilograms. Thus, it can carry a variety of non-destructive testing devices for inspection, paint removal, and de-riveting devices for maintenance. The robot uses vacuum suction cups for sticking to the surface of an object and can be integrated with a vision sensor system for guidance and visual inspection. The positioning of the robot is achieved by the use of a joy-stick or a PC computer. With this portable robot, it is possible to a) inspect areas that are within easy reach, b) program the robot to follow a specified path while inspecting or maintaining the structures, and c) remotely guide it to desired locations. This robotic system will minimize human error, increase the productivity of an inspector, and reduce the cost of inspection and maintenance.