Mario Ziebuhr

The Integrated Operational Transportation Planning Problem with Compulsory Requests

Demand fluctuations and high fixed costs force freight forwarders to consider the integrated operational transportation planning problem, which consists in the combined usage of own transportation resources (self-fulfillment) and external carriers (subcontracting) for the fulfillment of requests. For high quality goods or because of reliability and trustiness, customers prohibit subcontracting for some of their requests (compulsory requests). In this paper we present an approach for solving the integrated problem in case of the existence of compulsory requests. The presented approach is based on an adaptive large neighborhood search and on a column generation procedure. By means of this approach we quantify the increase of fulfillment costs which is caused by different kinds of compulsiveness of transportation requests. A first benchmark study shows that our heuristic approach for the integrated problem with compulsion outperforms the only approach found in literature for that problem, and therefore justifies the investigation of our main study with 6960 test instances. In our main study more realistic and extended instances are used, which gives us the possibility to consider the impact of different kinds of compulsory requests.

Agent-Negotiation of Lot-Sizing Contracts by Simulated Annealing with Part-Way Resets

The distributed multi-level uncapacitated lot-sizing problem is a group decision problem which has to be solved by a set of self-interested and autonomous agents. The agents represent independent companies which have to agree on a joint production plan in a supply chain context. In order to solve the problem we extend a negotiation-based simulated annealing approach introduced by Homberger by a part-way reset procedure. The part-way reset procedure allows a negotiation based search which reaches a deadlock to continue with a different contract proposal and thereby offers a possibility of overcoming disagreements between agents more easily. A benchmark study shows that the approach is competitive on set of 80 medium sized instances from the literature in terms of solution quality, in particular 47 new best-known solutions were computed.

A Coordination Mechanism for a Collaborative Lot-Sizing Problem with Rivaling Agents

A distributed uncapacitated lot-sizing problem with rivaling agents (DULR) is introduced. The DULR considers concurrent items, i.e., items that can be produced by more than one agent. The agents are self-interested and have private information. They coordinate their local plans in order to find a joint global plan which minimizes total cost. The individual plans are coordinated by a collaborative planning approach based on simulated annealing. In addition to some well-known techniques a production responsibility assignment procedure and Shapley compensation payments computed by means of a modified characteristic function are incorporated. The proposed solution approach outperforms a reference value in 206 out of 272 new DULR instances. The approach is more efficient on small instances than on medium sized instances.

Transportation Planning with Forwarding Limitations

Small- and medium-sized forwarders are confronted with thin margins and high demand fluctuations in competitive transportation markets. In these markets forwarders try to improve their planning situation by using external resources besides their own resources. These external resources might belong to closely related subcontractors, common carriers or cooperating forwarders in horizontal coalitions. In recent publications, it is assumed that some transportation requests are prohibited to be fulfilled by certain external resources due to contractual obligations. These requests are known as compulsory requests. In this paper, a transportation planning problem including external resources is extended by the mentioned compulsory requests. It is proposed to consider different types of compulsory requests depending on the applicable external resources for fulfilling these requests. As a solution approach a column generation-based heuristic is applied, which uses a strict composition procedure and a strict generation procedure for handling compulsory requests. In a detailed computational study, the increase of transportation costs is analyzed.

Transportation Planning with Different Forwarding Limitations

In recent publications, it is assumed that there are transportation requests which have to be fulfilled by certain resources (e.g., own vehicle fleet or external carriers) due to contractual obligations. These requests are known as compulsory requests. The contribution of this publication is to identify the increase in transportation costs caused by a combination of compulsory requests with different contractual obligations. To evaluate the impact of compulsory requests, an existing column generation-based heuristic with two solution strategies for handling compulsory requests is applied and the generated results are analyzed.

Collaborative Transportation Planning with Forwarding Limitations

In collaborative transportation planning, independent forwarders align their transportation plans by exchanging requests within a horizontal coalition. The goal of the coalition members is to increase their profitability and flexibility in competitive markets with high demand fluctuations. In recent publications, it is assumed that each request can be fulfilled by any coalition member. However, in practice some requests are prohibited to be forwarded due to contractual agreements. These requests are known as compulsory requests. The contribution of this paper is to identify the increase of costs caused by compulsory requests of a collaborative pickup and delivery transportation planning problem. To analyze the impact of compulsory requests, an existing column generation-based heuristic with two solution strategies for handling compulsory requests is applied and investigated.

A Collaborative Lot-Sizing Problem with Production Limitations

Manufacturing companies are using collaborative planning for the coordination of lot-sizing decisions in inter-organisational supply chains. By using collaborative planning, the members of a supply chain try to identify a production plan which results in lower costs compared to individual plans by simultaneously preserving their autonomy. A distributed lot-sizing problem with rivaling agents (DULR) is studied where each item can be produced by more than one member of the coalition (agent). Thereby it occurs that agents compete for the production quotas of items. However, the goal of this contribution is to extend the DULR by considering two types of items. One type can be produced by more than one agent, while the other one can only be produced by a certain agent due to contractual obligations. We denote the former type of items as concurrent item and the latter one as compulsory items. To solve the DULR with different types of items, an existing negotiation mechanism based on a simulated annealing is applied and modified. A benchmark study shows that the modified solution approach even outperforms the best-known approach for the DULR. Based on this finding, a second study is applied where the impact of compulsory items is investigated for the DULR.