Patrik Flisberg

Laps Care : an operational system for staff planning of home care

The health care system in Sweden and many other countries is facing increasing costs. The major reason is the changing age distribution of the population with more elderly people in need of support ...

A hybrid method based on linear programming and tabu search for routing of logging trucks

In this paper, we consider an operational routing problem to decide the daily routes of logging trucks in forestry. This industrial problem is difficult and includes aspects such as pickup and delivery with split pickups, multiple products, time windows, several time periods, multiple depots, driver changes and a heterogeneous truck fleet. In addition, the problem size is large and the solution time limited. We describe a two-phase solution approach which transforms the problem into a standard vehicle routing problem with time windows. In the first phase, we solve an LP problem in order to find a destination of flow from supply points to demand points. Based on this solution, we create transport nodes which each defines the origin(s) and destination for a full truckload. In phase two, we make use of a standard tabu search method to combine these transport nodes, which can be considered to be customers in vehicle routing problems, into actual routes. The tabu search method is extended to consider some new features. The solution approach is tested on a set of industrial cases from major forest companies in Sweden.

RuttOpt - A Decision Support System for Routing of Logging Trucks

We describe the decision support system RuttOpt, which is developed for scheduling logging trucks in the Swedish forest industry. The system is made up of a number of modules. One module is the Swedish road database NVDB which consists of detailed information of all the roads in Sweden. This also includes a tool to compute distances between locations. A second module is an optimization routine that finds a schedule i.e. set of routes for all trucks. This is based on a two phase algorithm where Linear Programming and a standard tabu search method are used. A third module is a database, storing all relevant information. At the heart of the system is a user interface where information and results can be viewed on maps, Gantt schedules and result reports. We also describe the characteristics of the general routing problem in forestry together with a focus on the planning process and systems in use in the Swedish situation. The system RuttOpt has been used in a number of case studies and we describe four of these. The case studies have been made in both forest companies and hauling companies. The cases range from ten to 110 trucks and with a planning horizon ranging from between one and five days. The results show that the system can be used to solve large case studies and that the potential savings are in the range 5-30%.

FuelOpt: a decision support system for forest fuel logistics

The use of forest fuel is increasing at heating plants in Sweden. Heating plants provide energy in the form of hot water for heating houses and apartments in local municipalities. Forest fuel are products obtained from harvesting in forests that cannot be used for further processing at sawmills and pulp and paper mills. Examples of such products are tree branches, tree tops and low quality logs. The optimization of the supply chain for round-wood (logs to sawmills, pulp and paper mills) and for forest fuel is similar but involves two main differences. First, forest fuel has to be converted into chips before delivery to the customer, and second, the demand for forest fuel varies over the year due to the temperature. To balance the chipping and transportation capacities over time, it is important to manage inventory levels at terminals. The optimization model developed provides decision support for questions regarding the choice of technology for chipping, where to perform the chipping operations, and the allocation of different assortments to heating plants. The system has been tested on a large case study from a Swedish forest energy company. The results show large savings and that the system is very useful for both planning and business development.

Optimization based planning tools for routing of forwarders at harvest areas

The forwarding of logs at harvest areas once the harvesting is done is planned manually by experienced operators. To improve their efficiency and simplify the planning we have developed and tested ...

Integrated harvest and logistic planning including road upgrading

This paper provides an integrated model for harvesting and logistic planning for tactical purposes over several years. The logistic planning includes both road upgrading and transportation between harvest areas and industries. The former is particularly important when dealing with problems when the accessibility of the road network is low due to, for example, thawing and heavy rains. The optimization model uses a detailed description of harvest areas including their spatial location, volume output of different assortment computations and net present value (NPV) for each year in the planning horizon. The model also uses a detailed description of the road network using the Swedish national road database. The model is very large and hard to solve, and hence, we are developing a solution approach based on an aggregation technique. An important part of the planning process is to select areas for the next 5 years, for example, and we analyze three different approaches. One approach is based on maximizing the NPV of the forest value, that is, the value at roadside. The second one is based on minimizing the logistic cost, and the third one combines NPV of the forest value at roadside and logistic. We analyze differences in a case study with over 6000 areas from the Swedish forest company Sveaskog. The results show that an integrated approach is necessary in order to avoid sub-optimal solutions.

Using Analytics in the Implementation of Vertical and Horizontal Curvature in Route Calculation

Determining the best route for logging trucks is difficult as many road features needs to be considered. There are methodologies to determine a good weight setting for these features based on inverse optimization, allowing them to be combined into one objective. The distance of the minimum-cost route on a network where the arc costs are determined by this weighted objective will then form the basis of invoicing. From detailed collected and agreed routes acting as the most preferred solutions, we can evaluate the quality of our proposed approach. Multiple sources of information are used, e.g., lidar, aerial photos, and GIS databases are collected and made available. There has been a demand from end-users to also include vertical and horizontal curvature as road features in the route selection. Since such values are not directly collected or stored in databases, they must be analyzed and estimated using geographical information. We propose a methodology for computing vertical and horizontal curvatures that represent the perception of such features, as well as processes to clean and complement inaccurate coordinates in the data. The proposed decision tools work very well in practice and are implemented in the intelligent transport planning system called calibrated route finder (CRF). CRF has been used on national level for distance calculation and route selection on since 2010, and the proposed use of vertical and horizontal curvatures was implemented during 2014. Today, over 50% of all forest sector transport invoicing in Sweden is based on the system.

A model approach to include wood properties in log sorting and transportation planning

ABSTRACT There is a trend that sawmills are more focused on particular valuable products in their production. This has led to an increased demand for sawlogs that are better adapted to the target products and production efficiency. Depending on the product being produced there are different log properties which are better adapted for certain products than others. Sawmills can require hard constraints on log properties such as length, diameter, internode length and sound knots. Some properties are not required but are desired as they make the production more efficient or increase the frequencies of preferred products. In these cases, we include an added value corresponding to what the industry is willing to pay for improved adaptation of the raw material. To achieve this, we propose an optimization model that integrates logging operations (bucking and forwarding) at harvest areas, transportation planning and flexible description of demand at sawmills. High flexibility for sorting at harvest areas may require additional piles of different properties to be generated. Instead of using a large number of special assortments, we allow many sorting alternatives depending on the requirements used at the industries. The transportation planning decides on the flows between harvest areas and sawmills while considering demand and supply. Even if many potential piles are used in the planning model, only a few may be used in practice. We present computational results based on 16 synthesized geographically distributed harvest areas, each representing all regional variation of mature sample trees from the Swedish National Forest Inventory and a number of sawmills.

Improvement of animal welfare by strategic analysis and logistic optimisation of animal slaughter transportation

The transportation of animals to slaughterhouses is a major welfare concern. The number of slaughterhouses has decreased over time in Europe due to centralisation. This is expected to increase tran ...

The Aftermath of Implementing Collaboration in a Network of Sawmills: A Retrospective Analysis on Logistics Costs

While usually collaborative logistics assures all partners are better off in coalition, a partner may in turn be composed by different sub-units. What is the effect of implementing collaboration for each of these sub-units? We study this problem motivated by a real-world case arising in a network of sawmills in Sweden. These sawmills have a common purchase and logistic organisation. The purchasing cost of forest areas is divided evenly among the mills even though the real purchasing costs differ between sawmills. The organisation looks for an approach to also split the logistic cost in a fair and transparent way. Moreover, the sawmills collaborate with an external company in wood bartering. Even if the organization as a whole benefits from the collaboration, the collaborative solution may leave some of the sawmills worse off, as the volumes they would use in absence of collaboration goes to the external company. The impact depends on the geographical location of mills, and the organisation wants to know how the negative impact can be balanced by a new allocation of the logistic costs. By using an optimization model implemented in a decision support system, we compute the logistics costs perceived by the organization in presence and absence of collaboration. We study a number of approaches to allocate the logistic cost and analyze how these approaches can serve as a basis for the process.