Kontrollsystem för automatisk vagnföljning till skogsvagnar
Control system for automatic drawbar steering on forest trailers
Author
Summary, in English
A tractor with a forest trailer is a large vehicle combination. When it is driven in the woods there is not a lot of space. To make it possible to turn in limited spaces forest trailers are equipped with an extra joint on the drawbar. This is called drawbar steering. This joint changes the geometry of the trailer in order to make it take another path. This feature is very convenient in the forest as with the right settings, this makes the trailer follow the tractor’s tracks without requiring any extra space. This joint is currently manually controlled by the driver.
This master thesis investigates how the drawbar steering could be controlled by an automatic control system and remove this task from the driver. To do so, some different principles for trajectory detection is compared. This thesis is focusing on the principle that offers the easiest implementation on an existing forest trailer, even though this may not gives the most exact trajectory information.
The mathematical models and angle relations for the trailer and drawbar are analyzed to understand how the drawbar steering should be adjusted and how a control system could do that. To test and verify these models and assumptions, a simulation program is developed. The simulation tests show that the chosen principle for regulating the drawbar steering works - with just a minor deviation in difficult situations. This deviation results in a difference between the desired and the actual trajectory that reaches a maximum of a few centimeters.
A prototype system is developed and implemented on a full-scale forest trailer to verify the results.
Tests show that the system is able to regulate the drawbar steering to accomplish the desired result. The deviation found in the simulations is seen in the real test case as well, but it is so small that it does not affect the use of the automatization. One limitation that appeared during the tests is that, for the system to work properly it is required that the tractor is driven at low speed. This is because the drawbar steering, that is hydraulically controlled, is mowing slowly and will not have time to compensate otherwise. This is however not a problem since a forest trailer is always driven slowly in the woods.
This master thesis investigates how the drawbar steering could be controlled by an automatic control system and remove this task from the driver. To do so, some different principles for trajectory detection is compared. This thesis is focusing on the principle that offers the easiest implementation on an existing forest trailer, even though this may not gives the most exact trajectory information.
The mathematical models and angle relations for the trailer and drawbar are analyzed to understand how the drawbar steering should be adjusted and how a control system could do that. To test and verify these models and assumptions, a simulation program is developed. The simulation tests show that the chosen principle for regulating the drawbar steering works - with just a minor deviation in difficult situations. This deviation results in a difference between the desired and the actual trajectory that reaches a maximum of a few centimeters.
A prototype system is developed and implemented on a full-scale forest trailer to verify the results.
Tests show that the system is able to regulate the drawbar steering to accomplish the desired result. The deviation found in the simulations is seen in the real test case as well, but it is so small that it does not affect the use of the automatization. One limitation that appeared during the tests is that, for the system to work properly it is required that the tractor is driven at low speed. This is because the drawbar steering, that is hydraulically controlled, is mowing slowly and will not have time to compensate otherwise. This is however not a problem since a forest trailer is always driven slowly in the woods.
Department/s
Publishing year
2017
Language
Swedish
Publication/Series
CODEN:LUTEDX/TEIE
Full text
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Document type
Student publication for professional degree (Master's level)
Topic
- Technology and Engineering
Keywords
- Vagnstyrning
- skogsvagn
- kontrollsystem
- styrsystem
- canbus
Report number
5390
Supervisor
- Gunnar Lindstedt
- Johan Björnstedt (Integration of Non-synchronous Generation - Frequency Dynamics)
Scientific presentation