A system for resource efficient process planning for wire EDM

Efficient utilization of available resources for a particular machine tool technology is an important aspect of sustainable manufacturing. The objective of this paper is to present a method for efficient resource process planning for a Wire EDM Machine Tool System. For a given part information (required surface finish and workpiece height), the developed program automatically selects the feasible wires and generates the operation sequence and corresponding cutting conditions. The system then presents a multi objective framework consisting of both ecological criteria (waste generation, electricity consumption) and economic criteria (different costs and machining time) to suggest the wire which provides the best compromise solution for the considered criteria.

The MOVE System: Monitoring of waste collecting vehicles

Telmo Cunha, Phillip Tomé

Nowadays, efficiency and productivity are fundamental concepts, in any kind of business. Although one can easily accept this as a known fact, one cannot easily identify which steps must be taken to achieve these goals. One approach consists of taking full advantage of the assets already available in the company, be they manpower or equipment. One kind of business that is strongly exposed to this problem concerns urban waste collecting. In this case, the productivity of the company can increase substantially if good fleet management policies are followed. Being aware of this fact, GEONAV has developed a fleet management system, named MOVE (Vehicle Monitoring), which is based on GPS. Each vehicle is equipped with a small onboard computer that includes, in the less complex model, a 12 channel GPS receiver and a GSM module. To cope with the problems usually affecting GPS in urban environments, such as having few satellites in view and multipath due to urban canyons, the system can incorporate information from low cost dead-reckoning sensors, such as the vehicle odometer and a gyroscope. Furthermore, other features can be added to the system, by using information from sensors readily available in the vehicle or that are installed specifically for the task intended. For instance, through a keypad unit, the driver can identity itself, by inserting a specific code or input the amount of fuel supplied to the vehicle. In addition, the system can automatically count the number of waste bins emptied, the number of times the vehicle has disposed of its waste in the wasteland or determine in real-time the vehicle’s weight. All information is sent to a Control Center using GSM or is stored in the computer’s memory, for a later download. In this case, an alternative means of transmission besides GSM can be used, namely a short range radio. Since no costs are involved when using this radio system, the exploitation costs of the MOVE system are greatly reduced. The Control Center software is based on a client/server architecture. The server application is responsible for controlling the communications between the Control Center and the vehicles and for storing all data received in a central database. The client applications connect to the server application, using the intranet, and are based on the GIS ArcView 8.x platform. Using a client application, an operator can visually determine the fleet status over a map or other type of visual representation. To reduce exploitation costs of the system, the status of the fleet is obtained by using SMS messages to exchange data between the vehicles and the Control Center. However, the option to follow a particular vehicle, by establishing a GSM call, is also possible. In this case, the position of the vehicle is updated at 1 Hz. The information that is stored in the database is organized in such a way as to allow the calculus of several statistical parameters that are useful to the management and control of the fleet. For example, one can determine the amount of kilometers driven, the time to complete a particular waste collection circuit, the fuel consumption, the number of waste bins emptied and their location, the number of times the vehicle was emptied of its waste, the vehicle’s weight, etc. This information can be used to establish new and better policies to enhance the fleet’s productivity and to present a better service to the end customer. This paper describes in detail the architecture of the MOVE system and its functionalities, including both the equipment installed onboard the vehicles and the Control Center’s software. Emphasis is given to the system’s flexibility to be used in different case scenarios, besides the monitoring of waste collection vehicles.

2003

Méthodologie de la synthèse des systèmes énergétiques industriels

Raffaele Bolliger

This work presents a synthesis method that leads to the preliminary design of industrial energy systems. Such systems are composed of several technologies that transform, through a set of physical unit operations, raw materials and energy into products and energy services. The purpose of the preliminary synthesis is to define which technologies form the system, to calculate their technical characteristics, their operating conditions and their interactions, based on performance indicators such as for example the cost of the system or its environmental impact. This area is studied since a long time and many synthesis approaches are available. However, these methods have significant limitations, particularly in their ability to face the study of more and more complex systems. The main goal of the method presented in this work is to enable the study of large systems and promote the use of the experience gained from previous studies in the form of models and methodological approaches. The synthesis method of industrial energy systems is based on the overall system optimization using a model that is obtained by assembling several modules, representing each a set of physical unit operations and whose equations are formulated with the black box technique, and an integration model that can represent the possible interactions within the system. Optimization is performed using a multi-objective evolutionary algorithm, whose objective functions are defined on the basis of calculation of several performance indicators based on the model of the system. To simplify the resolution of this complex system, the optimization problem is decomposed into a master problem, responsible for calculating the characteristics of the units and their operating conditions, and an optimization slave subproblem, which selects the units being part of the system and their interconnections. To ensure its robustness, the slave subproblem is formulated as a mixed-integer linear optimization problem. The slave subproblem is formulated by using process integration techniques, which are extended in this work to allow the synthesis of multiple heat and mass transfer networks. The synthesis problem can thus be defined using an explicit superstructure or by one generated automatically, either implicit or explicit. This work also introduces a technique that greatly reduces the number of degrees of freedom of the integration model. Instead of separately optimizing each ΔTmin/2 associated with heat streams, a formula is applied to calculate their value from a reference case. The ΔTmin/2 optimization is thus reduced to the optimization of a single decision variable related to the reference case, regardless of the size of the problem. The proposed method uses a set of heterogeneous elements, including flowsheeting software for modeling physical unit operations, mathematical programming tools for the formulation of the integration problem, methods for calculating performance indicators and calculation tools such as the optimization algorithm. This work introduces new tools developed to systematically apply the proposed methodology and to automate recurring operations of data transfer and the call of the various used software. In particular, a syntax description is defined as an abstraction layer to describe and to structure the exchanged information. A computing platform has been created to support the application of the method and to ensure the data transfer between its components. Two case studies are presented to illustrate the various aspects of the synthesis method. A first case, involving the synthesis of two combined cycles, has been chosen to illustrate the different application stages of the method and to show the potential reuse of certain modules. Through the integration techniques, it has been possible to identify potential heat recovery that can increase the performance of one of the cycles beyond what had been expected by experts using conventional simulation techniques. The second case study is about the treatment of waste generated by an industrial site active in the field of fine chemicals. Waste treatment can recover different materials and energy services useful for process units, thereby reducing the quantities purchased in the market. The model of multi-network integration can easily solve the complexity of the problem of waste management in developing strategies for allocating waste to the various treatments available for different objective functions related to operating costs and environmental impact.

EPFL2010

Contribution à l'étude des modes de rayonnement acoustique d'une structure

Olivier Schevin

Noise radiated by different industrial structures that surround us in daily life are more and more considered as environmental pollution. Standards defining a tolerable sound level for each of these noise sources are regularly called into question and respecting them becomes an additional constraint for manufacturers. The last decades have seen the increasing development of means used to fight these noise disturbances. The wide diversity of noises perceived as harmful has contributed to the progressive increase in specificity and efficiency of solutions proposed to reduce the disturbances. For some applications, passive solutions, based on the use of materials capable of absorbing or deviating acoustic or vibratory waves, have progressively been replaced by "active" solutions, based on the generation of an acoustic wave of opposite phase to the disturbing one radiated by the noise source. Power transformers are sources for which passive solutions (anti-noise walls) are usually expensive and not very efficient, particularly at low frequency. Furthermore, characteristics of noise radiated by transformers (low frequency tone noise) are such that they are particularly well suited for the implementation of an active solution. Typically, an active control system dedicated to transformers (feedforward) is composed of actuators, used to generate the anti-noise and usually located near the tank, sensors, used to measure the attenuation obtained and to provide a reference signal, and a controller used to drive the actuators as a function of the information collected by the sensors. When the sensors are microphones, they are usually moved away from the noise source, in such a way that they pick up acoustic pressure that is representative of the noise propagated far away. In the vicinity of the source, local acoustic phenomena can occur which are not propagated far away. A microphone located near the noise source would therefore pick up an acoustic pressure that did not necessarily represent the one that effectively exists far away, the area where we are in fact seeking to reduce the noise. These phenomena, frequently grouped under the term "nearfield" tend to decrease the performance of the control system, owing to the fact that the controller seeks in this case to reduce an acoustic pressure which is not representative of the noise to be reduced. In practice, the significant amount of wiring required as a result of the positioning of the microphones in the far field, has a non-negligible effect on the cost of the system. The possibility of bringing the sensors closer to the source is sufficiently advantageous to envisage to studying the feasibility and the resulting consequences. The present approach consists in representing the primary field radiated by a vibrating structure in terms of a set of "acoustic radiation modes". The use of radiation modes to characterise the behaviour of a structure has received increasing attention since the beginning of 90's, especially for active control applications. Usually, this approach consists in representing the radiated power in terms of a set of surface velocity distributions, called radiation modes, that have the property of radiating independently of each other. Radiation modes result from diagonalization of a discrete expression of the radiation operator. We propose here to study the consequences on the radiation modes of a structure from bringing the microphones closer to it. We will study how the acoustic field varies with the distance and how this can be used to obtain a model, the complexity of which is adapted to the observation distance.

EPFL2001