The objective of this thesis is to develop a model that represents the dynamics of a hydraulically operated forestry crane. The model was derived with the traditional Euler-Lagrange formalism and considers the crane mechanics, three double-acting hydraulic cylinders and the valve control unit. On the basis of the derived model we reproduced the entire crane model in MATLAB in order to run simulations herewith. This gave us the possibility to do parameter changes for further studies of the crane in motion. Another major goal within the thesis work was to estimate cylinder friction of the hydraulic actuators. We built up a test rig and used double-acting cylinders for determing their frictional behaviour. For this, we ran open-loop experiments in order to create velocity-friction maps that represented the static friction force of the cylinders. In this concern, we varied system pressure and cylinder load to study their influence on the friction force. By means of the derived static friction maps we approached the cylinder’s dynamic friction behaviour and applied both step and ramp control inputs to examine the spring-damping characteristics of the microspoic bristles in the contacting area. The dynamic friction experiments have been exerted in the fashion of the LuGre model. As a result we acquired different nominal friction parameters that we necessarily used to develope adequate friction models. A third objective of this thesis was to establish a crane-tip control. Instead of a traditional control, providing a direct relationship between joystick input and cylinder extension, the focus was to build up a control for the end-effector’s trajectory in a two-dimensional frame. This could be achieved by using inverse kinematics in order to determine the required joint angles that corresponded to the desired position of the crane-tip. The work also contains a CD including all developed MATLAB models that have been written within this project.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:vxu-1932 |
| Date | January 2008 |
| Creators | Heinze, Alexander |
| Publisher | Växjö universitet, Institutionen för teknik och design, Växjö : Institutionen för teknik och design |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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