Vibration Suppression Of Flexible Manipulator Research Articles

A New Fuzzy Backstepping Control Based on RBF Neural Network for Vibration Suppression of Flexible Manipulator

A New Fuzzy Backstepping Control Based on RBF Neural Network for Vibration Suppression of Flexible Manipulator

Minimum-time Trajectory Planning for Residual Vibration Suppression of Flexible Manipulator Carrying a Payload

For the purpose of eliminating residual vibration of a two-link flexible manipulator as well as minimizing time consumption, a scheme of multi-objective trajectory planning in joint space is proposed in this paper. Piecewise polynomial is applied to generate a smooth joint trajectory. Lagrangian approach and the assumed modes method is used to derive motion equations of FMs. Finally, Multi-objective particle swarm optimization (MOPSO) algorithm is implemented to solve time of each polynomial. The effectiveness of proposed algorithm is demonstrated by simulation results.

Model-Free Composite Control of Flexible Manipulators Based on Adaptive Dynamic Programming

This paper studies the problems of tip position regulation and vibration suppression of flexible manipulators without using the model. Because of the two-timescale characteristics of flexible manipulators, applying the existing model-free control methods may lead to ill-conditioned numerical problems. In this paper, the dynamics of a flexible manipulator is decomposed into two subsystems which are linear and controllable at different timescales by singular perturbation (SP) theory and a model-free composite controller is designed to alleviate the ill-conditioned numerical problems. To do this, a model-free composite control strategy is constructed which facilitates in designing the controller in slow and fast timescales. In the slow timescale, the slow subsystem controller is designed by adaptive dynamic programming (ADP) based on the measurements of the slow inputs and the position, while the vibration in the slow timescale is estimated by the least square method. In the fast timescale, the vibration is reconstructed based on the measurements of vibration and its estimate in the slow timescale, by which the fast controller is designed using ADP. Stability of the closed-loop system is proved by SP theory. Finally, simulations are given to show the feasibility and effectiveness of the proposed methods.

Robust vibration control of a flexible manipulator in presence of payload uncertainty

This paper presents the results of hybrid vibration controllers applied for vibration suppression of flexible manipulator. The model of the manipulator is assumed to be uncertain due to varying payload. To cater for the model uncertainty the proposed hybrid controller combines robust input shaping for command input with μ-controller applied for active vibration suppression using smart materials. Dependence of hybrid controller performance on design frequencies of input shaper is also studied. Results showed that the performance of hybrid controller is strongly dependent on the parameters used for designing input shaper, and the effectiveness of the hybrid controller can be substantially increased by judiciously selecting the design frequencies of input shaper. Effectiveness of the proposed controller is demonstrated by comparative studies with hybrid controllers formed by robust input shaping and PPF (positive position feedback) controller. Results are compared for suppressing vibrations resulting from slewing motion of manipulator, where the slewing motion is controlled by the PD controller. Results of comparisons showed that the μ-controller gave better performance in terms of settling time and energy consumption than those using PPF.

Optimal Trajectory Planning and Linear Velocity Feedback Control of a Flexible Piezoelectric Manipulator for Vibration Suppression

Trajectory planning is an effective feed-forward control technology for vibration suppression of flexible manipulators. However, the inherent drawback makes this strategy inefficient when dealing with modeling errors and disturbances. An optimal trajectory planning approach is proposed and applied to a flexible piezoelectric manipulator system in this paper, which is a combination of feed-forward trajectory planning method and feedback control of piezoelectric actuators. Specifically, the joint controller is responsible for the trajectory tracking and gross vibration suppression of the link during motion, while the active controller of actuators is expected to deal with the link vibrations after joint motion. In the procedure of trajectory planning, the joint angle of the link is expressed as a quintic polynomial function. And the sum of the link vibration energy is chosen as the objective function. Then, genetic algorithm is used to determine the optimal trajectory. The effectiveness of the proposed method is validated by simulation and experiments. Both the settling time and peak value of the link vibrations along the optimal trajectory reduce significantly, with the active control of the piezoelectric actuators.

Active vibration control of flexible manipulator using auto disturbance rejection and input shaping

This paper presents a vibration control strategy for a flexible manipulator with a collocated piezoelectric sensor/actuator pair. A hybrid vibration controller is proposed by combining the input shaping technique with auto disturbance rejection controller. The parameters of the closed-loop system can be adjusted to the known values by disturbance compensation and linear feedback using the auto disturbance rejection controller. This way, input shaper can be designed without accurate parameters of the flexible manipulator. Both simulation and experiments are conducted to validate the proposed control algorithm. The results verified the effectiveness of the proposed controller in vibration suppression of flexible manipulator.

Lookup table control method for vibration suppression of a flexible manipulator with optimization of the minimum settling time and energy consumption

Active vibration suppression of flexible manipulators is important in many engineering applications, such as robot manipulators and high-speed flexible mechanisms. The demand for a short settling time and low energy consumption of vibration suppression requires consideration of optimal control. Under a wide range of operating conditions, however, the fixed optimal parameters determined for a control algorithm might not produce the best performance. Therefore, to enhance performance, this paper suggests a lookup table control method for a flexible manipulator. This method can tune itself to the optimal parameters on the basis of initial maximum responses to the controlled system. In this study, a multi-objective genetic algorithm is used to search for optimal parameters with regard to positive position feedback to the control algorithm. In turn, with the optimal parameters, the multi-objective functions of the settling time and energy consumption during the vibration control of a flexible manipulator can be minimized. The simulation and experimental results both indicate that the energy consumption can be reduced significantly if the settling time is slightly increased. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Vibration Mechanism of Constrained Spatial Flexible Manipulators.

For free motions, vibration suppression of flexible manipulators has been one of the hottest research topics. However, for constrained motions, a little effort has been devoted for vibration suppression control. Using the dependency of elastic deflections of links on contact force under static conditions, vibrations for constrained planar two-link flexible manipulators have been suppressed successfully by controlling the contact force. However, for constrained spatial multi-link flexible manipulators, the vibrations cannot be suppressed by only controlling the contact force. So, the aim of this paper is to clarify the vibration mechanism of a constrained, multi-DOF, flexible manipulator and to devise the suppression method. We apply a concise hybrid position/force control scheme to control a flexible manipulator modeled by lumped-parameter modeling method. Finally, a comparison between simulation and experimental results is presented to show the performance of our method.

Control of vibration of flexible manipulators

Flexible manipulator systems are receiving increasing attention due to their advantages over conventional rigid manipulators. The advantages of flexible manipulators are faster response, lower energy consumption, relatively smaller actuators, higher payload to weight ratio and, in general, less overall cost. However, due to their flexible nature, induced vibrations appear in the system during and after a positioning motion. This implies that in developing a control strategy for such systems, both the rigid body as well as flexible motion (vibration) have to be taken into account. A considerable amount of research work has already been carried out on the vibration control of flexible manipulators. These range from open-loop control to closed-loop control strategies of fixed and adaptive nature. This paper presents an investigation into the development of several approaches for vibration control of flexible manipulators. A single-link flexible manipulator is considered. Open-loop control techniques, including Gaussian-shaped and filtered command methods, and closed-loop control approaches of fixed and adaptive nature, including joint-based collocated control and hybrid collocated and non-collocated control, are developed. These are verified within simulation and practical rig-based environments. Finally, a comparative assessment of the performance of these strategies in vibration suppression of flexible manipulators is provided.

Integrated distributed sensing and active vibration suppression of flexible manipulators using distributed piezoelectrics

AbstractStructural oscillation of flexible robot manipulators would severely hamper their operation accuracy and precision. This article presents an integrated distributed sensor and active distributed vibration actuator design for elastic or flexible robot structures. The proposed distributed sensor and actuator is a layer, or multilayer of piezoelectric material directly attached on the flexible component needed to be monitored and controlled. The integrated piezoelectric sensor/actuator can monitor the oscillation as well as actively and directly constrain the undesirable oscillation of the flexible robot manipulators by direct/converse piezoelectric effects, respectively. A general theory on the distributed sensing and active vibration control using the piezoelectric elements is first proposed. An equivalent finite element formulation is also developed. A physical model with distributed sensor/actuator is tested in laboratory; and a finite element model with the piezoelectric actuator is simulated. The distributed sensing and control effectiveness are studied.