Residual Vibration Suppression Research Articles

Residual Vibration Suppression of Piezoelectric Inkjet Printing Based on Particle Swarm Optimization Algorithm.

Piezoelectric inkjet printing technology, known for its high precision and cost-effectiveness, has found extensive applications in various fields. However, the issue of residual vibration significantly limits its printing quality and efficiency. This paper presents a method for suppressing residual vibration based on the particle swarm optimization (PSO) algorithm. Initially, an improved PI model considering the nonlinear hysteresis characteristics of piezoelectric ceramics is established, and the model is identified through a strain gauge circuit to ensure its accuracy in describing the nonlinear hysteresis characteristics. Subsequently, a dynamic model of the piezoelectric inkjet printing system is constructed, with precise parameter identification achieved using the self-induction principle. This enables precise simulation of residual vibration. Finally, the driving waveform is optimized based on the PSO algorithm, with iterative calculations employed to find the optimal combination of driving waveform parameters, effectively suppressing residual vibration while ensuring sufficient injection energy. The results indicate that this method significantly reduces the amplitude of residual vibration, thereby effectively enhancing printing quality and stability. This research offers a novel solution for residual vibration suppression in piezoelectric inkjet printing technology, potentially advancing its applications in printing and biofabrication.

A Terminal Residual Vibration Suppression Method of a Robot Based on Joint Trajectory Optimization

Vibration problems have become one of the most important factors affecting robot performance. To this end, a terminal residual vibration suppression method based on joint trajectory optimization is proposed to improve the accuracy and stability of robot motion. Firstly, based on the characteristics of the friction nonlinearity due to joint coupling and physical feasibility of dynamic parameters, a semidefinite programming method is used to identify dynamic parameters with actual physical meaning, thereby obtaining an accurate dynamic model. Then, based on the result of the residual vibration time domain analysis, a joint trajectory optimization model with the goal of minimizing joint tracking error is established. The Chebyshev collocation method is used to discretize the optimization model. The dynamic model is used as the optimization constraint, and barycentric interpolation is used to obtain the optimized joint motion trajectory. Finally, industrial robot experiments prove that the vibration suppression method proposed in this article can reduce the maximum acceleration amplitude of residual vibration by 62% and the vibration duration by 71%. Compared with the input shaping method, the method proposed in this paper can reduce the terminal residual vibration more effectively and ensure the consistency of running time and trajectory.

Fast and Precise Positioning With Coupling Torque Compensation for a Flexible Lightweight Two-Link Manipulator With Elastic Joints

This study presents an effective two-degrees-of-freedom controller, considering coupling torque compensation, with the aim of achieving fast and precise positioning of a flexible lightweight two-link robot with elastic joints. Coprime factorization-based feedforward control and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_\infty$</tex-math></inline-formula> control are cooperatively applied to the quasi-full-closed-loop control structure, forming a fundamental control strategy with improved reference tracking and residual vibration suppression capability, compared with the original proportional–proportional integral control. However, satisfactory outcomes for control performance are not realized due to the coupling effect between the robot joints. Previous studies have often addressed the coupling issue for the semiclosed-loop control structure, based on the approximate rigid-body dynamics, but the existing methods are not applicable to the quasi-full-closed-loop control structure. In this research, a flexible three-mass model-based feedforward coupling torque compensation scheme appropriate for the quasi-full-closed-loop control structure is proposed, combined with a position reference filter design. The simulation and experimental results obtained confirm the superiority of the proposed method over the conventional methods, and the control specifications are consistent with those of the rigid manipulators. The proposed controller design is beneficial for industrial robotics applications that demand flexibility but without deterioration in control performance.

Dynamic modeling and residual vibration suppression of electrostatically driven soft dielectric elastomer minimum energy structures

Dielectric elastomers (DEs), a special class of soft electro-active polymers that undergo finite deformation under external electrical stimuli, offer a wide range of applications that include but are not limited to soft actuators, soft robots, and energy harvesters. Among the various configurations of dielectric elastomer-based soft mechanisms, DE-based minimum energy structures (DEMES) are elite due to their several advantageous characteristics, such as lightweight, an easy fabrication process, the ability to achieve a desirable complex 3-D shape, the capability of undergoing large out-of-plane actuation despite planar fabrication, fast response, and controllability. However, when a DEMES actuator is driven by an input voltage signal consisting of different Heaviside steps, the intrinsic residual vibrations exhibited by the actuator may restrict the motion precision required in real-world applications. In this work, a nonlinear dynamic model of the DEMES actuator is devised using the Euler–Lagrange equation of motion, and the neo-Hookean material model is utilized to describe the material behavior of the DE membrane. A feedforward control technique is developed to suppress the inherent residual vibrations exhibited by the DEMES actuator. The control technique relies on the balance of the electro-mechanical forces at the minimum point, characterized by zero velocity and minimum bending angle in an oscillation cycle. The capability of the proposed feedforward control technique is demonstrated by controlling the DEMES actuator to different desired positions without residual vibrations. A parametric study is performed to explore the dependence of the proposed control technique on several parameters, such as frame bending stiffness, pre-stretch of the membrane, and membrane damping. The feedforward control technique and the inferences obtained from the current research can be implemented effectively in the design and development of open loop controllers for electrostatically driven soft electro-active devices.

Research on the Residual Vibration Suppression of Delta Robots Based on the Dual-Modal Input Shaping Method

The Delta robot is a high-speed and high-precision parallel robot. When it is in function, the end effector generates residual vibration, which reduces the repeat positioning accuracy and positioning efficiency. The input shaping method has previously been shown to suppress the residual vibration of the robot, but the vibration suppression effect of the single-modal input shaper is not good for the delta robot, which has multiple dominant modes for the residual vibration. To solve this problem, this paper proposes an effective method for residual vibration suppression of Delta robots based on dual-modal input shaping technology. Firstly, the modal analysis of the Delta robot is performed using finite element software, and the dominant modal of its residual vibration is determined. Secondly, six dual-modal input shapers are designed according to the obtained modal parameters. Finally, Simulink is used for simulation analysis to verify the robustness and vibration suppression performance of the designed six dual-modal input shapers and traditional single-modal input shapers. The simulation results show that the designed ZVD-EI dual-modal input shaper has good robustness, can effectively suppress the residual vibration of the Delta robot, and can effectively improve the repetitive positioning accuracy and work efficiency of the Delta robot when it is running at high speed.

Research on the sensor for detection of carburized case depth based on nonlinear ultrasound

Carburized case depth may be characterized by using nonlinear ultrasound. However, the excitation and receiving sensors are difficult to control in the same conditions in each experiment and the operation process is complicated, therefore, a specialized sensor needs to be developed. In this work, the influence of the backing materials with different constituents and thickness on the characteristics of sensors is investigated. The structure of the specialized sensor is designed, applied, and verified in the detection of carburized case depth based on nonlinear ultrasound. The results show that the backing layer consists of three-dimensional graphene (3DG) 1wt%/tungsten powder 80wt%/epoxy resin has high acoustic impedance and attenuation characteristics, the backing layer with thicknesses of 8 mm has high sensitivity and residual vibration suppression, the specialized senor simplifies the detection procedure, and improves the efficiency and stability of detection.

Research on vibration suppression and trajectory tracking control strategy of a flexible link manipulator

Residual vibrations caused by point-to-point motions reduce the positioning accuracy and dynamic performance of flexible link manipulators, and the trajectory planning method, a well-known open-loop control strategy, has been proven to effectively suppress the residual vibration in point-to-point motion. However, this open-loop control method has limitations in dealing with model uncertainty and disturbance problems. In this paper, a control strategy based on dynamics-based trajectory planning and fuzzy self-tuning PD (FST PD) controller is proposed, and applied to achieve residual vibration suppression and trajectory tracking of a flexible link manipulator. To improve the trajectory tracking performance under external disturbances, this control strategy is combined with a linear extended state observer (LESO). Firstly, the dynamic model of the system is deduced using the floating reference frame and Lagrange equation. On this basis, the objective function to minimize the lateral deformation of the tip is constructed, and then the optimal trajectory is obtained by using the Crossbreeding PSO (CBPSO) algorithm. Secondly, the optimal trajectory is used as the desired trajectory to suppress residual vibration, and the FST PD controller combined with the LESO is used to achieve high-precision trajectory tracking control of the flexible link manipulator. Finally, the effectiveness and feasibility of the composite control strategy is verified through multiple simulations. The proposed method can provide support for vibration suppression of flexible link manipulators; meanwhile, the controller structure of this method is simple and easy to implement, and the use of sensors/actuators and other equipment in the system is reduced, which effectively reduces the economic cost.

A deep reinforcement learning-based optimization method for vibration suppression of articulated robots

To solve the vibration problem of articulated robots, a deep reinforcement learning-based optimization method for input shaping (RLIS) is proposed. The optimization method applies the arbitrary time-delay filter as the model and includes two main stages: determining the RLIS initial parameter ranges; and constructing and improving the RLIS optimization strategy. In the first stage, a post-adaptive method based on the recursive least squares algorithm is used to determine the RLIS initial parameter ranges. In the second stage, the input shaping optimization problem is modelled as a Markov decision process, and the RLIS optimization strategy is constructed using a deep reinforcement learning algorithm. Subsequently, a selection mechanism based on state value and a fuzzy reward system is proposed to increase the learning efficiency and simplify the design process. Finally, several groups of experiments are designed to demonstrate the effectiveness and stableness of the proposed method in residual vibration suppression.

Residual vibration suppression in uncertain systems: A robust structural modification approach to trajectory planning

In this paper a novel method to improve the residual vibration suppression in underactuated uncertain flexible systems through motion planning is proposed. The proposed technique relies on the concurrent use of input shaping and on the alteration of the mechanical properties of the system, which enables the enhancement of the robustness to uncertain parameters. Robustness is formulated through the parametric sensitivities of the natural frequencies that provide an analytical and non-probabilistic tool, which is embedded in the eigenstructure assignment algorithm developed in this work. The effectiveness of the proposed method is assessed through a benchmark testbed composed by a triple pendulum attached to a delta robot, that should execute rest-to-rest, residual vibration-free motion. Hence, residual vibrations of the pendulum are used to measure the accuracy and the sensitivity of the proposed combined shaper-IDSM approach. Both the numerical and experimental results confirm the advantages of the proposed technique for the suppression of the residual vibrations in uncertain systems over traditional techniques. In particular, robustness of the dominant tuning frequency is increased with respect to variations of the tip-end mass of the pendulum, representing a varying payload transferred by a robotic system.

Vision sensor based residual vibration suppression strategy of non-deformable object for robot-assisted assembly operation with gripper flexibility

PurposeIndustrial robots are extensively deployed to perform repetitive and simple tasks at high speed to reduce production time and improve productivity. In most cases, a compliant gripper is used for assembly tasks such as peg-in-hole assembly. A compliant mechanism in the gripper introduces flexibility that may cause oscillation in the grasped object. Such a flexible gripper–object system can be considered as an under-actuated object held by the gripper and the oscillations can be attributed to transient disturbance of the robot itself. The commercially available robots do not have a control mechanism to reduce such induced vibration. Thus, this paper aims to propose a contactless vision-based approach for vibration suppression which uses a predictive vibrational amplitude error-based second-stage controller.Design/methodology/approachThe proposed predictive vibrational amplitude error-based second-stage controller is a real-time vibration control strategy that uses predicted error to estimate the second-stage controller output. Based on controller output, input trajectories were estimated for the internal controller of the robot. The control strategy efficiently handles the system delay to execute the control input trajectories when the oscillating object is at an extreme position.FindingsThe present controller works along with the internal controller of the robot without any interruption to suppress the residual vibration of the object. To demonstrate the robustness of the proposed controller, experimental implementation on Asea Brown Boveri make industrial robot (IRB) 1410 robot with a low frame rate camera has been carried out. In this experiment, two objects have been considered that have a low (<2.38 Hz) and high (>2.38 Hz) natural frequency. The proposed controller can suppress 95% of vibration amplitude in less than 3 s and reduce the stability time by 90% for a peg-in-hole assembly task.Originality/valueThe present vibration control strategy uses a camera with a low frame rate (25 fps) and the delays are handled intelligently to favour suppression of high-frequency vibration. The mathematical model and the second-stage controller implemented suppress vibration without modifying the robot dynamical model and the internal controller.

Research on the Residual Vibration Suppression of a Controllable Mechanism Robot

The motors and reducers of traditional industrial robots are installed at the joints, which leads to large moment of inertia and difficult to effectively improve the dynamic performance of the robots. In particular, the residual vibration at the end of the robots will significantly reduce its working efficiency and fatigue life. Therefore, this paper proposes a new method to reinstall the motor and reducer near the frame, which can effectively suppress the residual vibration of the robots and simultaneously reduce the moment of inertia. Taking the series industrial robot as the research object, four types of CM robots are designed based on the theory of a multi-DOF controllable mechanism (CM). The motor and reducer of the robot are reinstalled near the frame through different branch chains, and their moments of inertia are calculated and compared. The dynamic equations of residual vibration of the four CM robots considering concentrated mass are established based on the finite element method (FEM) and Timoshenko space beam element (SBE) model, and the correctness of the equations are verified by experiments. The results show that the installation position of motor and reducer has a significant influence on the value of moment of inertia of the robot. The motor and reducer of configuration D are reinstalled near the frame by three branches, which can effectively reduce the attenuation time and amplitude of residual vibration at the end of the robot. The research provides a new idea for improving the dynamic performance of industrial robots.

Suppression of Residual Vibration in Nonlinear Systems With Temporal Variation and Uncertainty in Parameters by Elimination of the Natural Frequency Component

Abstract A systematic approach is developed for determining a control input for the point-to-point control of an overhead crane that exhibits temporal variation of rope length in addition to damping and nonlinearity, without inducing residual vibration. Complete suppression of the residual vibration is achieved by eliminating the natural frequency component of the cargo from the apparent external force, which is defined to include the effects of damping, nonlinearity, and parameter variation. Furthermore, an effective technique previously proposed by the authors for improving robustness to the modeling error of the natural frequency is extended. Numerical simulation results show that, even when cargo is hoisted up or down during operation, the proposed method realizes accurate positioning of the cargo without inducing residual vibration and sufficiently improves robustness. To the best of our knowledge, this is the first frequency-domain robust open-loop control strategy that ensures a theoretical zero amplitude for residual vibration in the absence of modeling error in nonlinear crane hoisting operation. The developed method is not only a contribution to the realization of low-cost and efficient crane hoisting operation, but is also applicable to the control of other nonlinear damped systems that include time-varying parameters.

A Review on Disturbance Analysis and Suppression for Permanent Magnet Linear Synchronous Motor

In high-end testing and manufacturing equipment, a trend exists whereby the traditional servo feed system with a ball screw and rotary motor will gradually be replaced by a direct drive system. The precision motion system driven by a permanent magnet linear synchronous motor (PMLSM) offers several advantages, including high speed, high acceleration, and high positioning accuracy. However, the operating precision of the feed device will be affected by the PMLSM robustness to nonlinear and uncertain disturbances, such as cogging force, friction, thermal effects, residual vibration, and load disturbance. The aim of this paper was to provide a survey on disturbance analysis and suppression approaches to improve the dynamic performance of PMLSM motion systems. First, the origin and inhibition methods of thrust ripple and friction are presented. Second, the mechanisms, modeling approaches, and mitigation measures of thermal effects are introduced. Additionally, the residual vibration characteristics and suppression methods are discussed. Finally, disturbance observers of periodic and aperiodic loads are introduced. These suppression methods from structural design and control compensation are then discussed in order to improve the dynamic response and steady-state accuracy of PMLSM.

The effect of preload force on damping in tendon-driven manipulator

Purpose The purpose of this paper is to study the preload range of tendon-driven manipulator and the relationship between preload and damping. The flexible joint manipulator (FJM) with joint flexibility is safer than traditional rigid manipulators. A FJM having an elastic tendon is called an elastic tendon-driven manipulator (ETDM) and has the advantages of being driven by a cable and having a more flexible joint. However, the elastic tendon introduces greater residual vibration, which makes the control of the manipulator more difficult. Accurate dynamic modeling is effective in solving this problem. Design/methodology/approach The present paper derives the relationship between the preload of the ETDM and the friction moment through the analysis of the forces of cables and pulleys. A dynamic model dominated by Coulomb damping is established. Findings The linear relationship between a decrease in the damping moment of the system and an increase in the ETDM preload is verified by mechanics analysis and experiment, and a curve of the relationship is obtained. This study provides a reference for the selection of ETDM preload. Originality/value The method to identify ETDM damping by vibration attenuation experiments is proposed, which is helpful to obtain a more accurate dynamic model of the system and to achieve accurate control and residual vibration suppression of ETDM.

Optimal Switching Time Control for Suppressing Residual Vibration in a High-Speed Macro-Micro Manipulator System

This brief studies a novel residual vibration suppression problem arising in a high-speed macromicromanipulator system designed for various precision positioning tasks. First, the dynamic of the macromicrosystem is mathematically modeled by a nonlinear partial differential equation (PDE). Subsequently, a new nonlinear vibration suppression and trajectory planning problem governed by a couple of ordinary differential equations (ODEs) are successfully formulated by using the assumed mode method (AMM) and Hamilton’s principle. Based on the developed model, an optimal switching time control strategy combined with control parameterization is proposed to realize the residual vibration suppression by trajectory planning. The gradients of the cost functional with respect to the unknown control variables and switching time variables are derived analytically by the sensitivity analysis method. Both numerical simulations and real experiments in the laboratory verify that the proposed method is superior to the classical fifth-order polynomial (FOP) approach for the vibration suppression problem.

Suppression of Residual Vibration Associated with Positioning by Optimization of JCTA Cam Curve

Suppression of Residual Vibration Associated with Positioning by Optimization of JCTA Cam Curve

Study on residual vibration suppression of flexible multibody system with large deformation

Study on residual vibration suppression of flexible multibody system with large deformation

Optimization of Generalized S-Curve Trajectories for Residual Vibration Suppression and Compliance With Kinematic Bounds

This article proposes a new optimization algorithm that assures the minimum possible duration of generalized S-curve trajectories compliant with kinematic limitations and capable of suppressing residual vibrations when tracked by a resonant plant. Thanks to the possibility of generating such kind of trajectories with a chain of filters, called smoothers, each one characterized by a single parameter, i.e., the duration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T_i$</tex-math></inline-formula> of its impulse response, the optimization process aims at minimizing the order of the trajectory, and accordingly the number of smoothers in the chain, and leads to rest-to-rest trajectories that, under the given specifications, cannot be made shorter in time. Therefore, the structure of the trajectory is not predetermined but is the outcome of the proposed algorithm together with the optimal parameters defining it. The effectiveness of the proposed approach is proven by applying the designed trajectories to an experimental setup based on a flexible link.

Residual vibration control of a single-link flexible manipulator with variable stiffness and damping magnetorheological joint

Residual vibrations of large flexible manipulator can be easily excited due to large inertia and low damping, which greatly reduces the efficiency of the tasks. This paper describes an approach for the use of smart materials, specifically, magnetorheological fluid, in vibration control of a single-link flexible (SLF) manipulator. Considering that the systems with variable stiffness and damping have demonstrated excellent performance, a compact variable stiffness and damping magnetorheological joint (VSD-MRJ) was designed. A mathematical model of the SLF manipulator with a VSD-MRJ was established. Two independent fuzzy controllers were designed and applied to the stiffness and damping control of the joint. Finally, a test platform was built and the experimental results verified that the residual vibration suppression performance of the manipulator with the VSD-MRJ is better than the traditional rigid manipulator.

Theoretical and experimental investigations on modified LQ terminal control scheme of piezo-actuated compliant structures in finite time

This study focuses on the open-loop dynamic shape control to realize a rapid and smooth morphing process for a flexible plate which is actuated by a macro fiber composite patch. A finite element model of the system is established and verified for theoretical investigations. Steady-state and dynamic analyses are carried out to satisfy the desired rest-to-test morphing requirement. Spurious oscillations and large overshoots are observed while applying some common voltage signals. The results imply that the voltage profile of the actuator plays a key role in the dynamic morphing behavior of the system. Therefore, a quantitative criterion is proposed to determine the critical voltage slope for evaluating the boundary between quasi-static and dynamic processes. An optimal finite-time feedforward control approach named “modified linear quadratic (LQ) terminal controller” is proposed to optimize the voltage profiles by simultaneously considering the suppression of transient and residual vibration. The superiority of the proposed open-loop control scheme is appreciated when it is compared with the standard LQ terminal controller. An experimental setup is designed for verification. The effectiveness of the theoretical model is validated through modal analysis, static deformation, and dynamic responses. It is indicated by the experiment results that rapid and smooth dynamic shape morphing processes with negligible vibration within a short period of time can be achieved using the optimized voltage profile.