1993 Fiscal Year Final Research Report Summary
Nonlinear Vibration of Hunting in a Closed-Engine-Governor Loop
| Project/Area Number |
03650215
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
機械力学・制御工学
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| Research Institution | Saitama Institute of Technology |
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Principal Investigator |
KAWAZOE Yoshihiko Saitama Institute of Technology, Dept.of Mechanical Eng., Professor, 工学部, 教授 (00102898)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Hunting / Vibration / Self-Excited Vibration / Diesel Engine / Governing / Speed Control / Nonlinear Vibration / Limit Cycle |
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| Research Abstract |
Most of the past research work on engine speed hunting has been devoted to discriminating the divergence of a small disturbance given at an equilibrium state, resulting in a hunting estimation different from that of the actual system. In the author's previous study, a numerical simulation was given, which showed a transient process of a small oscillation developing into a sustained oscillation with a large amplitude.
In order to explain analytically the mechanism of nonlinear damping force and limit cycle evolution, the present study derived an approximated differential equation of a single degree of freedom system with the closed-engine-governor loop, noting the phenomenon of very slow frequency. It gives a simple physical reasoning to the nonlinear negative damping force which causes an instability and a limit cycle evolution, resulting from a concept of the dynamic feedback-torque gain.
Results show that there is energy input during a cycle when the dynamic feedback-torque is larger t
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han the inertia torque. This increases the amplitude, and at the final amplitude the energy put in by the negative damping force is neutralized by the energy dissipated by the positive force because of the nonlinearity of the torque characteristics. The analytical solutions of the amplitude of limit cycle agree well with the experimental results and the results of direct numerical integration. It also gives insight into the effects of the various parameters of the closed loop.
On the other hand, it was left unsolved as to whether the linear theory predicts the hunting occurrence at lower speeds. It was found in the present study that the engine speed fluctuation diminishes at lower speeds because a stopped for the maximum value of rack movement constrains the higher frequency component of the fuel control rack fluctuation caused by the suction stroke of each piston. It was also found that both the computer simulation and the experiment yield the occurrence of hunting even at extreme lower engine speeds when the maximum stroke of the control rack is increased, and the limit cycle behavior can be explained well qualitatively by noting the higher frequency fluctuation of the fuel control rack and the nonlinearity of torque characteristics. Less
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