Alberto J. Alvares

An integrated web-based CAD/CAPP/CAM system for the remote design and manufacture of feature-based cylindrical parts

This work describes the implementation of an integrated web-based CAD/CAPP/CAM system for the remote design and manufacture of feature-based cylindrical parts. This system, called WebMachining (http://webmachining.alvarestech.com), was developed in an e-manufacturing context, and the use of features allows the integration among the activities of collaborative design (WebCADbyFeatures), generative process planning (WebCAPP) and manufacturing (WebTurning). Through the WebCADby Features agent-based collaborative design module, cylindrical parts are modeled based on the synthesis of design features, in a Concurrent Engineering context. The WebCAPP generative CAPP module maps design features into machining features (including turning, milling, and drilling), and the mapping considers the setup, geometry, and operation. It uses a data structure similar to STEP-NC, and the generated process plans are nonlinear (i.e. they have alternatives). The WebTurning module performs the remote manufacture of the part, and it is based on a client–server architecture, where: (a) the servers are represented by the programs located at a workstation (Linux platform), which are connected to the machine tool through an Ethernet network interface; (b) the client is represented by a Java Applet. Some examples are provided in this paper, illustrating the remote design, process planning and manufacture of parts in a CNC turning center.

An internet-oriented management and control system in a distributed manufacturing environment

This work presents a methodology for web-based manufacturing management and control. It is a part of the WebMachining distributed manufacturing environment, which encompasses three manufacturing systems in Brazil: a Flexible Manufacturing Cell in Brasilia, a Flexible Manufacturing System in Joinville, and a Lathe in Florianopolis. The methodology includes planning, scheduling, control and remote manufacturing. The remote customer uses the environment to design and manufacture the parts, and an ERP software previews which manufacturing system will produce the ordered part. Also, the implementation aspects of a Web-based Shop Floor Controller for the FMC in Brasilia are presented in this paper.

Expert system for power generation fault diagnosis using hierarchical meta-rules

Rule processing and selection in forward chaining is a critical factor in the performance of expert systems. Considered the large quantity of information and rules in the hydroelectric generator unit, the rules were organized using hierarchical meta-rules. Meta-rules have been used to improve rule selection and increase the speed processing. This paper describes a method for improving rule selection automatically according with the device condition. The expert system developed in JESS (Java Expert System Shell) processes rules using rete algorithm. The FMEA (Failure Mode and Effect Analyze) is used as a tool to perform rules, that was implemented in CLIP language. The information required to perform FMEA is collected from past Work Order (WO), Maintenance Technical Instructions (MTI), Operation Technical Instructions (OTI) and Autonomous Maintenance Plan (AMP). This expert system assesses faults on power generation systems, subsystems and equipments. The diagnosis system processes online information acquires from fieldbus sensors and transmitters. This diagnosis method implemented can provide warning of failure; reduce the inspection cost, downtime and inventory. This expert system has been applied to hydroelectric power plant in Brazil. The results obtained along with their evaluations are satisfactory.

SIMPREBAL: An expert system for real-time fault diagnosis of hydrogenerators machinery

This paper proposes an expert system to aid plant maintainers and operators personnel for solving hydroelectric equipments troubleshootings. The expert system was implemented into intelligent maintenance system called SIMPREBAL (Predictive Maintenance System of Balbina). The SIMPREBAL knowledge base, the architecture and the inference machine are presented in detail. The knowledge base is based on experts empirical knowledge, work orders, manuals, technical documents and operation procedures. The predictive maintenance system architecture is based on the OSA-CBM framework that has seven layers. The software application has been successfully implemented in client-server computational framework. The data acquisition and intelligent processing tasks were develop in the server side and the user interface in the client side. The intelligent processing task is an expert system that use JESS inference machine. During two years, the SIMPREBAL has been used for monitoring and diagnosing hydrogenerators machinery malfunctions. The industrial application of the SIMPREBAL proved its high reliability and accuracy. Finally, satisfactory fault diagnostics have been verified using maintenance indicators before and after the SIMPREBAL installation in the hydroelectric power plant. These valuable results are been used in the decision support layer to pre-schedule maintenance work, reduce inventory costs for spare parts and minimize the risk of catastrophic failure.

A web-based STEP-NC-compliant architecture for low cost 3D part manufacturing

This paper presents an architecture of a computerised numerical controller (CNC) compliant with the ISO 14649 standard (STEP-NC) through an adapter that converts a program in the STEP-NC format to G-code. This architecture attempts to enable the implementation and dissemination of the STEP-NC standard in any company that performs numerically controlled machining operations. The STEP-NC controller is based on the open source LinuxCNC controller, which is compliant with the ISO 6983 standard (G-code). In order to validate the architecture a machine tool was built, having LinuxCNC on a personal computer. The controller is integrated with the STEP part 21 data model (ISO 10303 standard) using an adapter that reads a STEP-NC file generated by a software that models a 3D part via the internet. The LinuxCNC controller runs the STEP-NC file transparently, and the results are shown through a case study with the manufacture of an example part. [Received 6 June 2015; Revised 23 October 15; Accepted 2 December 2015]

PROGRESSES IN THE DEVELOPMENT OF A STEP-NC COMPLIANT ADDITIVE MANUFACTURING SYSTEM

The new standard of numerical control, known as STEP-NC, is categorized as the future of the advanced manufacturing systems. Greater flexibility and interoperability are some potential benefits offered by STEP-NC to meet the challenges of the new industrial landscape that is envisaged with the advent of Industry 4.0. Meanwhile, STEP-NC object-oriented programming has been partially applied and developed for machining processes (milling, turning...). But with the processes of additive manufacturing has not happened the same and the development is still incipient. This work presents the advances in the development of a new STEP-NC compliant additive manufacturing system, focusing particularly on the development of the information model. The application model activities in the IDEF0 nomenclature and application reference model in EXPRESS are presented. The AM-layer-feature concept has been introduced to define the manufacturing feature of additive processes based on material deposition layer-by-layer. Finally, a STEP-NC program generated from the EXPRESS model is presented, which can be implemented on an additive manufacturing system to validate the proposed model.

Real-time rate distortion-optimized image compression with region of interest on the ARM architecture for underwater robotics applications

AbstractThis paper proposes the use of a real-time progressive image compression and region of interest algorithm for the ARM processor architecture. This algorithm is used for the design of an underwater image sensor for an autonomous underwater vehicle for intervention, under a highly constrained available bandwidth scenario, allowing for a more agile data exchange between the vehicle and a human operator supervising the underwater intervention. For high compression ratios (smaller output size), execution time is dominated by the transformation algorithm, which plays a progressively smaller role as the compression ratio gets smaller (larger output size). A novel progressive rate distortion-optimized image compression algorithm based on the discrete wavelet transform (DWT) is presented, with special emphasis on a novel minimal time parallel DWT algorithm, which allows full memory bandwidth saturation using only a few cores of a modern multicore embedded processor. The paper focuses in a novel efficient inplace, multithreaded, and cache-friendly parallel 2-D wavelet transform algorithm, based on the lifting transform using the ARM Architecture. In order to maximize the cache utilization and consequently minimize the memory bus bandwidth use, the threads compete to work on a small memory area, maximizing the chances of finding the data in the cache. Their synchronization is done with very low overhead, without the use of any locks and relying solely on the basic compare-and-swap atomic primitive. An implementation in C programming language with and without the use of vector instructions (single instruction multiple data) is provided for both, single (serial) and multi-(parallel) threaded single-loop DWT implementations, as well as serial and parallel naive implementations using linear (row order) and strided (column order) memory access patterns for comparison. Results show a significant improvement over the single-threaded optimized implementation and a much greater improvement over both, the single- and multi-threaded naive implementations, reaching minimal running time depending on the memory access pattern, the number of processor cores, and the available memory bus bandwidth, i.e., it becomes memory bound using the minimum number of memory accesses. Due to memory saturation, the inplace 2-D DWT transform can be executed in the same time as a 1-D DWT transform or as an inplace memory block copy.

A Novel Minimum Time Parallel 2-D Discrete Wavelet Transform Algorithm for General Purpose Processors

A novel efficient inplace, multithreaded, and cachefriendly parallel 2-D wavelet transform algorithm based on the lifting transform is introduced. In order to maximize the cache utilization and consequently minimize the memory bus bandwidth use, the threads compete to work on a small memory area maximizing the chance of finding it in the cache and their synchronization is done with very low overhead without the use of any locks and relying solely on the basic compare-and-swap (CAS) atomic primitive. An implementation in the C programming language with and without the use of vector (single instruction multiple data - SIMD) instructions is provided for both single (serial) and multi (parallel) threaded single-loop DWT implementations as well as serial and parallel naive implementations using linear (row order) and strided (column order) memory access patterns for comparison. Results show a significant improvement over the single-threaded optimized implementation and a much greater improvement over both the single and multi threaded naive implementations, reaching minimum running time depending on the number of processor cores and the available memory bus bandwidth, i.e., it becomes memory bound using the minimum number of memory accesses. Given the simplicity and high speed of the lifting steps, an analysis based on the number of memory bus operations (read and write) is done for images that are larger than twice the shared cache size which establishes a lower bound for the running time of all linear memory access algorithms and also determines the maximum speed gains to be expected in relation to currently implemented parallel schemes based on the parallel execution of independent lifting steps. It also shows the optimality of the parallel algorithm presented. Finally, a comparison with currently available implementations shows the gains achieved by the proposed algorithm.

Progressive image compression and transmission with region of interest in underwater robotics

The increasing demand for underwater robotic intervention systems around the world in several application domains requires more versatile and inexpensive systems. By using a wireless communication system, supervised semi-autonomous robots have freedom of movement and, at the same time, allows the operator to get camera feedback and supervise the intervention. Moreover, the limited and varying bandwidth of underwater radio frequency (RF) and underwater acoustic modem channels is a major obstacle. This paper proposes the use of progressive (embedded) image compression and region of interest (ROI) for the design of an underwater image sensor to be installed in an Autonomous Underwater Vehicle, specially when there are constraints on the available bandwidth, allowing a more agile data exchange between the vehicle and a human operator supervising the underwater intervention.

A 2D-mapping strategy based on line segment extraction

This paper presents a strategy for a 2D-map building process for indoor environments. The strategy is conformed by two main processes: a line extraction phase based on a modified version of the Incremental algorithm, followed by a merging phase that grouped the extracted lines which represents the same real structure. This strategy is oriented for a sensory system configuration conformed by a set of range sensors. No a priori knowledge about the shape, or the number of the structures of the environment is necessary. The resulting map is a line-based representation in a global reference, without being necessary a previous construction of a local representation of the environment. The implemented algorithm is tested in both, simulated and real environments, with a robot platform equipped with a sensory system composed by 24 ultrasonic sensors in a ring configuration. Results show the viability of the proposed strategy.