Sway reduction of forest machine grapple using input shaping
Nieminen, Tomi (2023)
Nieminen, Tomi
2023
Automaatiotekniikan DI-ohjelma - Master's Programme in Automation Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2023-10-25
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202310118758
https://urn.fi/URN:NBN:fi:tuni-202310118758
Tiivistelmä
Fluent operation of forest machine is challenging task and requires plenty of training. Thus, development of partially or fully automated motions has become key interest. With automation, cognitive load of operators can be reduced and productivity and efficiency increased. Also, for inexperienced operators, the amount of training could be reduced. Furthermore, abrupt movements that cause swaying are typical for inexperienced operators, which may limit their productivity.
Input shaping is an open-loop method that prevents unwanted swaying by modifying the command signal before feeding it to the system. The performance of input shaping relies on the estimated values of natural frequency and damping ratio of the system. As a drawback, input shaping delays part of the operator command for attenuation purpose.
In this thesis, input shaping was implemented to a control system of a real forest machine and tested with slewing and crane tip near-far movements. The grapple model parameters, values of natural frequency and damping ratio were determined from measurements of the grapple swaying. According to measurements, grapple model was identified and input shaper designed to prevent swaying in the modelled frequency.
According to the test results, input shaping was capable of reducing major part of the swaying. However with slewing, it was noticed that performance is depending on how well actual velocity of specific movement is following the command velocity. Yet, the reduction of swaying with slewing movement was significant. With near-far movement, almost all of the swaying was attenuated.
Also, the effect of parameter uncertainty to swaying motion was tested by deviating the nominal values of natural frequency and damping ratio. In cases where ±10% error in natural frequency or five times smaller or higher damping ratio exists, input shaper was capable of reducing major part of the swaying and only small deterioration in performance was detected. In addition, the effect bof grapple opening and rotation was tested causing only minor changes to the modelled natural frequency and damping.
Input shaping is an open-loop method that prevents unwanted swaying by modifying the command signal before feeding it to the system. The performance of input shaping relies on the estimated values of natural frequency and damping ratio of the system. As a drawback, input shaping delays part of the operator command for attenuation purpose.
In this thesis, input shaping was implemented to a control system of a real forest machine and tested with slewing and crane tip near-far movements. The grapple model parameters, values of natural frequency and damping ratio were determined from measurements of the grapple swaying. According to measurements, grapple model was identified and input shaper designed to prevent swaying in the modelled frequency.
According to the test results, input shaping was capable of reducing major part of the swaying. However with slewing, it was noticed that performance is depending on how well actual velocity of specific movement is following the command velocity. Yet, the reduction of swaying with slewing movement was significant. With near-far movement, almost all of the swaying was attenuated.
Also, the effect of parameter uncertainty to swaying motion was tested by deviating the nominal values of natural frequency and damping ratio. In cases where ±10% error in natural frequency or five times smaller or higher damping ratio exists, input shaper was capable of reducing major part of the swaying and only small deterioration in performance was detected. In addition, the effect bof grapple opening and rotation was tested causing only minor changes to the modelled natural frequency and damping.