Abstract
PurposeThis study improves the robustness of the model-free controller based on a virtual structure. Additionally, the adverse interference between the proof-mass actuator resonance and a controlled object is investigated as it is not clarified in the previous studies.Methods and ResultsA virtual structure modeled as a SDOF system was inserted between the actuator and the actual controlled object. This achieved the indirect damping of the actual controlled object and model-free control. Vibration control simulations were conducted for various finite element models with a model-free {H}_{infty } controller based on a virtual structure. The results demonstrate that the actuator resonance adversely affects the stability of the control system when the controlled object has a mode whose natural frequency is too close to that of the actuator. Therefore, a notch filter was applied to the model-free {H}_{infty } controller design approach to suppress the resonance without affecting the damping performance. The improved controller with notch filter is more robust to the resonance of the actuator than the previous one.ConclusionsThe resonance of the proof-mass actuator adversely affects the stability of the control system composed of the previous model-free {H}_{infty } controller when the low-order vibration mode of the actual controlled object is too close to the natural frequency of the actuator. Introducing a notch filter into the model-free approach based on a virtual structure effectively reduces the negative impact due to the resonance of the actuator and improves the robustness of the control system.
Highlights
Vibration control technology is indispensable to achieve mechanical systems that are lightweight and compact with a high performance
This study assumes various kinds of disturbances involving low-frequency components, which make the control system based on a virtual structure prone to oscillations due to the resonance of the proof-mass actuator, as shown in "Vibration Control Simulation with K1"
The vibration of the controlled object, which is equivalent to that of the virtual structure, is used as the observed output based on Eq (4) when constructing the feedback control system
Summary
Vibration control technology is indispensable to achieve mechanical systems that are lightweight and compact with a high performance. The model-free controller designed in the previous study [26] does not ensure robustness for the vibration modes of the actual controlled objects that are too close to the natural frequency of the actuator. The purpose of the notch filter is to improve the robustness of the controller by reducing the gain of the model-free controller near the natural frequency of the actuator while simultaneously damping the vibration modes of the actual controlled objects within the vibration control band. The improvement of the previous method is inductively clarified through vibration control simulations using different controlled structures In these cases, the closed-loop system with a model-free controller may become unstable when the low-order vibration mode of the controlled objects is too close to the natural frequency of the actuator. The frequency response of the actuator from the control input to the displacement indicates that the natural frequency of the actuator is around 20 Hz (Fig. 2)
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