About the project
The skidder is defined as a self-propelled, articulated forest vehicle for skidding trees or parts of trees. The skidding is the removal of entire trees or parts of the tree (trunk, wood assortment) from the felling and processing site to the roadside landing. skidders are an important part of the forestry machinery that is produced and used in Croatia.
Existing skidders are powered by diesel engines, and in order to reduce the cost of use and meet increasingly stringent emission standards, the project aims to offer a conceptual design of a hybrid skidder, which includes sizing of drive components, customization of tools and designing management using modern optimization procedures based on precise and computationally efficient mathematical models and real data of the modes of operation of skidders measured on hilly and mountain terrain. For this purpose, it is necessary to carry out field measurements on existing vehicles, and then to carry out an adequate analysis of the collected data, which is, after processing, used as a basis for the development of hybrid and electric forest vehicles.
The project envisages the development of an experimental setup of an electro-hydraulic winch in order to produce a precise mathematical model intended to select a suitable winch drive that will fit into the hybrid drive of the skidder and to design the operation of such a winch. Finally, the goal of the project is to offer a conceptual design of a hybrid skidder that will be the basis for a prototype that can be further marketed as an innovative product of high added value.
The use of forestry machinery in modern wood harvesting technologies involves some risk to the health of the operator and damage to the forest ecosystem in terms of soil compaction, erosion, damage to trees and root systems, air, soil, water resources pollution, etc. On the other hand, forestry machinery has to do heavy work and meet the demands for higher productivity while reducing operating costs. This applies primarily to forest vehicles moving on forest soil.
The skidder is, according to ISO 6814:2000 norm, defined as a self-propelled, articulated forest vehicle for skidding trees or parts of trees. The skidding is the removal of entire trees or parts of the tree (trunk, wood assortment) from the felling and processing site to the roadside landing. Due to the necessary technical requirements for performing the skidding operations in forest terrain, the skidder uses a forestry winch to skid parts of the trees from the felling and processing site to the skid road, and then, when traveling along the skid road, one end of the load is lifted off the ground and rested on the rear end of the vehicle while the other end of the load is dragged on the ground. Due to the use of winches in the skidding process, the skidder is mainly driven on the skid roads, which significantly reduces damage to forest soil and young trees.
There are increasing demands in terms of reducing the cost of running forest machines, together with regulatory pressures for lower emissions of exhaust gases and noise, which calls into question the future of a skidder that uses a diesel engine as its sole power source. Therefore, forestry machinery manufacturers are interested in the electrification of the propulsion, which can already be seen with the appearance of certain hybrid and electric forest vehicles (e.g. forwarders and harvesters), but for the time being, such propulsions are not present in the skidder. The hybrid drive, which is thought to be a solution that can meet the requirements for low exhaust emissions, can use a smaller diesel engine, with an additional power source (e.g. battery) allowing it to operate in a more favorable mode, while retaining high drive performance over fully electric drive, extended autonomy, and less energy storage requirements, resulting in lower mass and total cost.
The future development of electrified forest vehicles is a very important topic of scientific research in the field of forestry engineering. It is a prerequisite for the precise determination of the energy consumption of different types of forest vehicles at different work tasks and under different terrain conditions. For this purpose, it is necessary to carry out field measurements on existing vehicles, and then to carry out an adequate analysis of the collected data, which is, after processing, used as a basis for the development of hybrid and electric forest vehicles. The parameterization and verification of the mathematical models of the skidder’s drive are achieved on the basis of the processed measured data. Using mathematical drive models with defined working cycles obtained by measurement, the structure of the hybrid drive and the dimensions of the hybrid drive elements (internal combustion engine, electric motor, batteries…) are determined using modern optimization methods which, as a result, give the optimal hybrid drive of the skidder for the selected working cycles (e.g. for hilly or mountainous terrain, or for universal use). For the optimal operation of each drive component, an optimal control strategy for the proposed hybrid drive is designed.
For the optimal operation of each drive component, an optimal control strategy for the proposed hybrid drive is designed. The aforementioned forest winch is an important element in the operation of the skidder and is a significant energy consumer. Existing skidders use hydraulic or mechanical winch drive. The hybrid winch drive is designed to use an electric or electro-hydraulic winch for greater energy-saving potential due to a better degree of efficiency and greater control over its operation. The project envisages the development of an experimental setup of an electro-hydraulic winch in order to produce a precise mathematical model intended to select a suitable winch drive that will fit into the hybrid drive of the skidder and to design the operation of such a winch.
Finally, the goal of the project is to offer a conceptual design of a hybrid skidder that will be the basis for a prototype that can be further marketed as an innovative product of high added value. The hybrid skidder is a step up from the current state of the market, where only conventional-powered skidders are offered. In addition to the innovative skidder solution, other project goals are also being achieved like increasing the market-oriented activities of scientific organizations and strengthening the model of technology transfer to the business sector.
Some outcomes of project elements, such as the results of measuring and analyzing data of real working cycles in different terrains, a mathematical model of conventional and hybrid skidder propulsion, and management of hybrid skidder and winch are results that will be applicable to related areas and will have a scientific value.
Activity 1: Procurement and installation of measuring equipment on skidders
Activity 2: Determining the structure of work elements of skidder in different operating conditions
Activity 3: Determination and measurement of terrain factors on the energy consumption of the skidder
Activity 4: Measuring the energy consumption of the skidder under different operating conditions
Activity 5: Data analysis of the energy consumption of the skidder
Activity 1: Development of a mathematical model of the existing skidder drive and parameterization and verification of the model
Activity 2: Defining the structure of the hybrid drive of the skidder and analysis of the power flow
Activity 3: Development of a scalable mathematical model of a hybrid skidder drive
Activity 4: Development of laboratory setup of electrohydraulic winch
Activity 5: Optimal component selection and optimization of control variables of hybrid skidder drive systems
Activity 6: Comparative analysis of an optimized model of a hybrid drive with a classic skidder drive
Activity 7: Conceptual design of a hybrid skidder
Activity 1: Project workshops
Activity 2: Publication of papers in scientific journals indexed in Web of Science
Activity 3: Participation in scientific conferences
Activity 1: Preparation of a study on verification and protection of intellectual property over the results of the project
Activity 2: Applying for a patent on research results
Activity 3: Agreements on scientific-research cooperation with companies
V Promotion and visibility
PM Project management and administration
Description of the project
The project proposal will be implemented through the experimental development phase. The biggest obstacle to the development of a hybrid skidder drive is the lack of knowledge of the total energy consumption of the skidder’s work on skidding wood under different operating conditions. The project seeks to develop modern methods of determining the energy consumption of the skidder by work components, which include the acquisition of modern measuring devices with the development of remote data transmission. The research will be conducted at two different relief sites (a hilly area in the Bjelovar-Bilogora County and a mountainous area in the Lika-Senj County).
Investigations will be carried out on two skidders owned by Croatian Forests Ltd. Zagreb in the real work of skidding wood. This method will provide relevant data whose processing and analysis will form the basis for the development of computational models and algorithms by project partners. By forming a faithful mathematical model of the skidder drive and using modern optimization tools, the most suitable hybrid drive structure, machines (IC engine and electric motors) and energy storage media (batteries, possible combinations with ultracapacitors or flywheels) will be selected.
With regard to the work cycles of the skidder and the selected hybrid drive, hybrid drive management will be designed, which is a necessary condition for harnessing the energy savings potential of the hybrid skidder. As the operation of auxiliary tools such as winches has a significant role in the work cycle of the skidder, the project will also include their adaptation to a newly developed hybrid drive in terms of seeking an electro-hydraulic or electrical solution instead of an existing hydraulic or mechanical one.
Based on the technical designs of the existing domestic production skidder and the solutions found for the optimal configuration of the hybrid drive, a preliminary solution for the installation of the hybrid drive in the skidder will be developed and an analysis of the financial feasibility of the proposed solution will be conducted. The concept of a hybrid skidder with economic analysis is a necessary basis for the potential adoption of the production of a hybrid skidder. Measured and analyzed data of real work cycle of skidder in different terrains and newly developed methods based on this data, obtained mathematical models and control algorithms will be able to be used for the development of hybrid or other alternative drives of different types of vehicles and tools in forestry and in related fields.