Prof. Dr.-Ing. habil. Peter Nyhuis

Function:
Managing partner
Phone:
+49 (0)511 279 76-119
E-Mail:
info@iph-hannover.de
vCard:
vCard
ResearchGate:
http://www.researchgate.net/profile/Peter_Nyhuis

Publications

Resource depletion and climate change are the main drivers for the rapid change of power generation structures. The energy transformation is causing an increase in energy prices for manufacturing small and medium-sized enterprises (SMEs). Within the last decade energy prices in Germany have doubled and are expected to grow even further . Metal processing SMEs are already attributing 4.5 percent of their gross production value to electricity costs. The paper shows the possible savings potential of the use of inventory levels as energy storage and provides approaches to an efficient solution of the associated optimization problems.

production program planning, energy costs, inventory level, energy storage

In average, more than 1,275 wind turbines were installed annually since 1997 in Germany and more than 27,000 wind turbines are in operation today. The technical and economic life time of wind turbines is around 20 to 25 years. Consequently, dismantling of aging wind turbines will increase significantly in upcoming years due to repowering or decommissioning of wind farms and lead to millions of costs for operators. An option to supersede the costly and time-consuming dismantling of wind turbines entirely on-site is to establish a dismantling network in which partly dismantled wind turbines are transported to specialized dismantling sites for further handling. This network requires an optimization model to determine optimal locations and an appropriate distribution of disassembly steps to dismantling sites. The challenge is to consider the networks dependency on the trade-off between transportation and dismantling costs which, in turn, depends on the selection of dismantling depths and sites. Building on the Koopmans-Beckmann problem, we present a mathematical optimization model to address the described location planning and allocation problem. To permit a proof-of-concept, we apply our model to a case-study of an exemplary wind farm in Northern Germany. Our results show that the model can assist dismantling companies to arrange efficient dismantling networks for wind turbines and to benefit from emerging economic advantages.

dismantling, wind turbine, optimization model

Currently used methods for factory layout planning are limited in their evaluation methods. Factory evaluation is either qualitative or quantitative, but limited to a few objectives. These deficits were overcome by the development of a quantitative, multidimensional ad hoc factory evaluation method. On this basis, it is now possible to develop a method for factory layout planning that reduces the planning effort and significantly increases the quality of the solution.

facility layout planning, factory planning, operations research, mathematical modelling

Rising and increasingly volatile energy prices resulting from increased power feeds from renewable sources such as solar and wind energy are confronting manufacturers with new challenges. If these companies procure their power supplies at ?uctuating short-term prices from electricity exchanges or through energy purchasing pools, they can in?uence the result-ing energy costs through production control via its actuating variables while energy consumption remains constant. A form of sequencing that decides at short notice which order will be processed next shows particularly high potential. The energy price-oriented sequencing rule that is introduced in this article prioritises orders with a high energy requirement at times when energy prices are low and gives precedence to orders that require less energy at times when energy prices are high, without neglecting the scheduled completion deadline. However, this sequencing rule can only be applied e?ectively under certain preconditions. These are elaborated in this article by means of a simulation study that will con?rm the way the rule functions.

production planning and control, manufacturing control, sequencing, energy costs

As a result of the increasing feed-in of renewable energies, the volatility of the electricity price rises. Considering this, manufacturers can save energy costs by applying an energy price-oriented sequencing rule. Since the application of this sequencing rule does not only have an impact on the energy costs, a potential analysis is presented in this article which, in addition to the energy costs, also considers the schedule compliance cost of production orders.

cost accounting, manufacturing control, production planning and control

Work-related illnesses and their results may pose a threat to businesses' productivity. This may as well affect businesses' competitiveness for the worse. A workplace designed by methods of ergonomic workplace-design may counter some of the caused issues. But companies often lack knowledge or fear required financial resources to restructure workplaces. With this article technical requirements to an automated ergonomics assesment system are described.

ergonomics, evaluation, optimization, workplace design

The volatility of electricity prices is steadily increasing due to the growing expansion of renewable energies. This is particularly observable at the electricity exchange. Small and medium-sized enterprises (SMEs) in the manufacturing sector can save energy costs due to these fluctuations through targeted load management methods. To increase this potential, SMEs need to use smart meters and obtain their electricity at pricest as close to those at the electricity exchange as possible.

power procurement, electricity exchange, load management, electricity costs

The forecast of sales volumes represents a challenge for the production planning. Above all, sales forecasts that are difficult to predict, such as those caused by promotions, are obstructive. Often, additional information from macroeconomic indexes is not topical, the level of detail of products to be forecast too low and the forecast expenditure too high. Aim of a research project therefore is to develop a model based on search engine data to forecast sales volumes at product level. By the use of complementary application of search engine data to the sales forecast is expected that the forecast mistake can be reduced compared with conventional forecast models upon product level. In general it should be clarified whether and in which extend the logistical efficiency of an enterprise can be improved by search engine data based forecast of sales volumes in the production planning.

production planning, sales forecast, search engine data, forecast model

In production, product-based failure costs can be reduced by focusing the production factor „human“. Therefore, human performance fluctuations during the course of day have to be considered in the production planning and control. This paper presents an approach for quality-orientated flexible job shop scheduling, taking into account human performance fluctuations during the day.

production planning and control, performance curve, quality

Assembling large-scale products involves frequent process interruptions why in order to reduce the impact of interruptions, a short-term response is necessary to reduce delivery delays and idle times of resources. An approach to challenge this represents the flexibility of a production system. Regarding the environment of large-scale product assembly, it has to be shown which potentials of flexibility are able to be used in a short-term manner.

assembly, production management, disruption management

Considering production planning and control, lot sizing is a very important task. Lot sizes are usually resorted to lot size dependent order and storage costs. However, models for lot sizes ignore the aspect of lot size dependent maintenance costs. For forging companies the tool wear has a great economic importance, because the tooling costs represents a major factor in production costs.

production planning and control, lot sizing, process stability

Rising electricity prices for industrial companies result in increasing energy costs and thus lower international competitiveness. Due to increasing electricity price fluctuations, savings in energy costs without capital-intensive investments are possible by implementing specific organizational methods to process energy-intensive orders at times of low prices and energy-low orders at times of high prices.

energy costs, energy price, manufacturing control, sequencing

Disassembling of large-scale products (e. g. wind energy plants, crane and conveyor systems which are known as XXL-Products) becomes increasingly important, as the operating time is limited. The challenge is to optimize the positioning of the complex and expensive disassembling on the operation site on the one hand and the costly transportation of modules to the disassembling factories. For this reason the location and allocation problem will be pictured in a mathematical model within the research project “DemoNet”. This model supports companies to create a XXL-disassembly-network. The research hypothesis assumes: a disassembly under ecological, economical and logistical aspects constitutes the optimum. The extension of a location planning tool forms the basis of the mathematical optimization model for the disassembly of XXL-Products. For solving the problem a genetic algorithms will be used. The result helps companies to arrange disassembling networks for XXL-Products efficiently.

dismantling planing, dismantling networks, impact model

Controlling the time synchronicity of supply processes for assembly requires a quantitative measure. An existing controlling instrument, the supply diagram, already provides an effective way of assessing the supply situation. It incorporates different key figures which allow for an evaluation of a company’s supply process coordination. However, it lacks a key figure for describing the level of time synchronicity. Therefore, a quantitative evaluation of actions to improve the time synchronicity in supply processes is not possible. Based on an existing approach of approximating the completion of full assembly orders, a key figure for describing the level of time synchronicity is developed in this article: the synchronicity factor. As this new key figure is dependent on the average number of components required for one assembly order for the regarded time period, a second measure, the relative synchronicity factor, accounts for this number and can thereby be used to compare different time periods. As the numerical calculation of the synchronicity factors is a complex problem, the possibility of applying a simple hill climbing algorithm to accurately determine the synchronicity factor for a certain supply situation is examined.

Production planning and control, supply chain management, supply diagram, time synchronicity

The ongoing change from make-to-stock to make-to-order production and the increasing interaction in value creation networks lead to growing challenges for companies regarding delivery date and delivery quantity flexibility. This leads to increased work load scatter in the production systems of companies. This paper presents a simulation-based approach on how the work load scatter can be reduced to a lower level and how this influences logistical characteristic lines.

load scattering, load variation, quantification, batch splitting

Production companies are faced with an increasingly turbulent business environment, which demands very high production volumes and delivery date flexibility. If a decoupling by storage stages is not possible or undesirable from a logistical point of view, load scattering effects the production processes. This expresses itself in the form of heavy load scattering. What kinds of quantification of the load scattering exist and how these have been further developed is subject of the following article.

load scattering, load variation, quantification, production planning and control

Increasingly rising electricity prices endanger the competitiveness of the German industry. If fluctuating electricity prices resulting from renewable energy are used, a reduction of production-related energy costs is possible. Therefore the capacity control opens a new field of action. In this paper, a backlog control is introduced, which selects the time of adjusting the capacity in response to energy prices.

time variable electricity prices, fluctuating energy consumptions, manufacturing control, capacity c

Compliance with punctual delivery under the high pressure of costs can be implemented in the forge industry through the optimization of the in-house tool supply. Within the Transfer Project 13 of the Special Research Department 489, a mathematical model was developed which determines the minimum inventory of forging tools required for the production, considering the tool appropriation delay.

production planning and -steering, production management, tool inventory reduction, servicelevel, fo

Increasing electricity price fluctuations through the augmented integration of renewable energies require dynamic tariff plans in order to conform the energy demand on the energy offer for achieving network stability. If time-variable electricity tariffs taking account into the specific needs of small and medium enterprises (SME) can be developed, energy costs can be reduced significantly by freedom degrees of an adapted manufacturing control.

energy costs, electricity tariff, manufacturing control, renewable energy

Forging companies are often suppliers of the automotive industry, which has, by the implemented principles of Just-In-Time production, particularly high demands on the logistics performance of their suppliers. Moreover, the cost pressure in this industry is very high, so forging companies are striving to minimize their logistics costs. One of the factors influencing these logistics costs is the amount tools in a company’s tool inventory. Since the tooling costs have a high percentage of the product costs, strategic positioning between logistics performance and costs in the forging industry holds great potential. However, while a too low number of tools may cause delays in production and more frequent setting-ups caused by division of production lots and a concomitant increase of setting-up times of up to 30%, a possible consequence of too high tool inventories is the increase of process uncertainty by a prolonged and more stray tool circuit pass-through time. A structured approach to the positioning of the tool supply between logistics performance and costs is presented.

production planning and -steering, production management, tool inventory reduction, servicelevel, fo