Level Of Vibration Reduction Research Articles

Aeroelastic Modeling of Trailing-Edge-Flap Helicopter Rotors Including Actuator Dynamics

The effect of actuator dynamics on a helicopter rotor with trailing-edge flaps for vibration control is investigated. Trailing-edge flap, actuator, and elastic rotor blade equations of motion are formulated using Hamilton’s variational principle. The coupled nonlinear, periodic equations are solved using finite elements in space and time. The baseline correlation study is based on wind-tunnel test data for a typical five-bladed bearingless rotor system. Good agreement is seen for the blade flap bending, chord bending, and torsion moments. It is shown that actuator dynamics cannot be neglected for a trailing-edge flap system with torsionally soft actuators. The parametric study performed using both coupled flap/actuator model and prescribed flap motion model indicated that the placement of trailing-edge flaps at 78% radius resulted in minimum flap input for this rotor. The vibration reduction level and trend are close between the predictions of both models at different forward speeds. Control inputs predicted by the coupled model show less sensitivity to the forward speed than that of prescribed model.

Command shaping techniques for vibration control of a flexible robot manipulator

This paper presents an investigation into development of feed-forward control strategies for vibration control of a flexible robot manipulator using command shaping techniques based on input shaping, low-pass and band-stop filtering. A constrained planar single-link flexible manipulator is considered and the dynamic model of the system is derived using the finite element method. An unshaped bang–bang torque input is used to determine the characteristic parameters of the system for design and evaluation of the control techniques. Feed-forward controllers are designed based on the natural frequencies and damping ratios of the system. Simulation results of the response of the manipulator to the shaped and filtered inputs are presented in time and frequency domains. Performances of the techniques are assessed in terms of level of vibration reduction at resonance modes, speed of response, robustness and computational complexity. The effects of number of impulse sequence and filter order on the performance of the system are investigated. Finally, a comparative assessment of the input shaping and input-filtering techniques is presented and discussed.

Hybrid control schemes for input tracking and vibration suppression of a flexible manipulator

This paper presents investigations into the development of hybrid control schemes for input tracking and end-point vibration suppression of a flexible manipulator system. The dynamic model of the flexible manipulator is derived using the finite element method. Initially, a collocated proportional-derivative (PD) controller utilizing hub angle and hub velocity feedback is developed for control of rigid-body motion of the system. This is then extended to incorporate a non-collocated proportional-integral-derivative (PID) controller and a feedforward controller based on input shaping techniques for control of vibration (flexible motion) of the system. Simulation results of the response of the manipulator with the controllers are presented in time and frequency domains. The performances of the hybrid control schemes are assessed in terms of input tracking and level of vibration reduction in comparison to the PD control. The effectiveness of the control schemes in handling various payloads is also studied. Finally, a comparative assessment of the hybrid control schemes is presented.

Hybrid control schemes for input tracking and vibration suppression of a flexible manipulator

This paper presents investigations into the development of hybrid control schemes for input tracking and end-point vibration suppression of a flexible manipulator system. The dynamic model of the flexible manipulator is derived using the finite element method. Initially, a collocated proportional-derivative (PD) controller utilizing hub angle and hub velocity feedback is developed for control of rigid-body motion of the system. This is then extended to incorporate a non-collocated proportional-integral-derivative (PID) controller and a feedforward controller based on input shaping techniques for control of vibration (flexible motion) of the system. Simulation results of the response of the manipulator with the controllers are presented in time and frequency domains. The performances of the hybrid control schemes are assessed in terms of input tracking and level of vibration reduction in comparison to the PD control. The effectiveness of the control schemes in handling various payloads is also studied. Finally, a comparative assessment of the hybrid control schemes is presented.

Vibration control of a single-link flexible manipulator using command shaping techniques

This paper presents experimental investigations into the development of feed-forward control strategies for vibration control of a flexible manipulator using command shaping techniques based on input shaping and low-pass and band-stop filtering. A laboratory-scale single-link flexible manipulator is used and various system responses are obtained. Initially, an unshaped bang-bang torque input is used to determine the dynamic response parameters of the system for design and evaluation of the control techniques. Feed-forward controllers are then designed based on the natural frequencies and damping ratios of the system. Experimental results of the response of the manipulator to the shaped and filtered inputs are presented in time and frequency domains. Performances of the techniques are assessed in terms of level of vibration reduction at the natural frequencies, time response specifications, robustness to natural frequency variation and processing time. The effects of the number of impulses and filter order on the performance of the system are investigated. Finally, a comparative assessment of input shaping and filtering techniques is presented.

Numerical simulation model of vibration responses of rectangular plates embedded with piezoelectric actuators

A numerical simulation model for random large amplitude vibration control of composite plate using piezoelectric material is presented. The H ∞ control design is employed to suppress the large amplitude vibrations of composites plates under random loading. The numerical simulation model is developed and based on the finite element method. The finite element governing equation includes fully coupled structural and electrical nodal degrees of freedom, and consider the von Karman large amplitude vibration. The modal reduction method using the structural modes is adopted to reduce the finite element equations into a set of modal equations with fewer degrees of freedom. The modal equations are then employed for controller design and time domain simulation. In the simulations without control, the value of the linear mode to the nonlinear deflection is quantified; and the minimum number of linear modes needed for accurate model is obtained. In the simulations with control, it is shown that the truncated modes, which are neglected in the control design, deteriorate the controller performance. Generally, the vibration reduction level is not monotonically increasing with the size of the piezoelectric actuator. The optimal piezoelectric actuator size depends on the excitation level. For higher excitation level, optimal actuator size is larger. The H ∞ controller based on the linear finite element formulation gives better vibration reduction for small amplitude vibration, but it still gives reasonable performance for large amplitude vibration provided that the piezoelectric actuator is big and powerful enough.

Selection of Sensor Locations for Active Vibration Control of Helicopter Fuselages

Vibration control has always been a challenging problem to the helicopter designer. This paper addresses the problem of the formulation and solution of an active vibration control scheme for helicopters, based on the concept of active control of structural response. First, using a mathematical procedure employing the Fisher information matrix, optimum sensor locations have been identified in a threedimensional model of a flexible fuselage structure. The reference parameters used in the selection process are the elements of a vector defined as the effective independence distribution vector and the condition number of the Fisher information matrix. It is observed that, irrespective of the excitation frequency, these optimally selected sensor locations experience relatively high levels of vibration. Then, using the measurement from these optimal sensor locations, a multi-input/mu lti-output control problem has been formulated and solved to obtain the active control forces required for vibration minimization in the helicopter fuselage. It is observed that sensor locations have a significant influence on the level of vibration reduction in a fuselage structure.

A NEW DUAL-REACTION MASS DYNAMIC VIBRATION ABSORBER ACTUATOR FOR ACTIVE VIBRATION CONTROL

A new passive/active dynamic vibration absorber is proposed for structural vibration control. The device consists of two reaction-masses attached to the primary structure through elastic elements. The active force pair is applied between these two reaction masses. This configuration should be contrasted to the traditional single reaction-mass system where the control force pair is implemented between the reaction-mass and the primary structure. The performance of the new device is evaluated by controlling the response of a cantilever beam subjected to white noise excitation. The control approach used is the feedforward algorithm. For purposes of comparison, the results are compared to the performance of an equivalent single reaction mass device. The results show that the proposed dual-mass dynamic vibration absorber actuator achieves the same level of vibration reduction using only half the control effort required by the single reaction-mass actuator. In addition, the concept of force transmissibility function is introduced. This function is the force applied by the hybrid dynamic vibration absorber onto an infinity impedance due to a unit control force. It is demonstrated that this function is an effective means to determine the potential of these devices.

A Hydraulic Absorber for Wideband Vibration Reduction in Ship Hulls

A vibration reduction of ship hulls by an active absorber system is proposed. In the scheme, a tuned mass is moved according to the hull vibration as measured by a multi-mode sensing system in order to generate a suitable active force for vibration reduction of hull girder. In order to supply the large amount of required power, a hydraulic servo system is implemented. Then the dynamic characteristic of the hydraulic system is considered for system design. Based on stochastic theory and optimal theory, the control law of the system is derived in order to approach the optimal level of vibration reduction. A 10-t absorber is applied to a 87,000-t oil tanker to demonstrate the feasibility of this scheme. The results show that the multi-peak values of resonance are suppressed in frequency response. Moreover, the vibration excited by propeller and engine is reduced to an extremely efficient level by this scheme.

位相半値幅法を用いた薄型光ディスク装置用駆動反力絶縁形対物レンズアクチュエータの開発

A new technique for reducing vibration of an objective lens actuator on a carriage is developed for optical disc drives. Phase disturbance at frequencies of several thousand hertz resulting from drive reaction forces is discussed. A practical method using only phase disturbance for evaluating modal damping in higher modes is proposed. Calculating modal damping in higher modes by this method is feasible for deciding the modal residue ratio and the level of vibration reduction. A simple structure for isolating the vibration of the drive reaction force of the actuator is designed. A new lens actuator which uses this vibration reduction technique has developed. And a thin-type optical disc drive has developed.