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Generally, a low damping system has a small phase margin. One should deal with the problems of long time delay and unmodeled dynamics for active vibration control of a low damping system sometimes. For a pneumatic drive flexible manipulator system, time delay or phase lag and unmodeled nonlinear dynamics problems have raised the level of concern. It is vital but difficult to regulate the phase of vibration controller, to compensate for the time-varying phase lag or time delay due to the gas compression and parametric uncertainty of the pneumatic control system. The objective of this investigation is to formulate an active vibration control law with practical approach of phase adjusting for a pneumatic drive flexible manipulator system. A control strategy named adaptive phase adjusting control is designed and applied. The adaptive phase adjusting controller is implemented by using the phase angles as explicit parameters. These parameters are tuned online, depending on the corresponding control performance index. To evaluate the control performance of the designed adaptive phase adjusting technique, experiments are conducted on a pneumatic drive flexible manipulator experimental setup. The experimental results demonstrate the adaptive phase adjusting controller has the ability to optimize the phase angle accordingly. Vibration suppression is accomplished by using the designed adaptive phase adjusting controller, even with time delay and unmodeled dynamics in the system.

A pneumatic drive system is used as the actuator of a flexible manipulator to control its motion as a rigid body and suppress its vibration when consider its low stiffness. A pulse code modulation (PCM) valve is used to construct a single-input dual-output control system. Due to the time-varying and nonlinear properties of the system, an improved adaptive interactive PD controller is applied for positioning and vibration control. The system model is used in simulation. A description of an adaptive interactive controller and our modification is provided. Experimental setup of this pneumatic drive system is described. Experiments for positioning and vibration control are conducted. The simulation and experimental results show the feasibility of the actuator and the effectiveness of the control strategy.

In this paper, we propose a scheme for estimating the proportion of the incoming traffic that is not responding to congestion at a router. The idea of the proposed scheme is that if the observed queue length and packet drop probability do not match with the predicted results from the TCP model, then the error must come from the non-responsive traffic; it can then be used for estimating non-responsive traffic. The proposed scheme utilizes queue length history, packet drop history, expected TCP and queue dynamics to estimate the proportion. We show that the proposed scheme is effective over a wide range of traffic scenarios through simulations.