One-link Flexible Manipulator Research Articles

Event-triggered robust distributed output feedback model predictive control for nonlinear MASs against false data injection attacks

In this paper, an event-triggered distributed output feedback model predictive control scheme for the nonlinear disturbed multiagent systems with sensor–controller channel false data injection attacks is proposed. To provide valid system states to the controller in the event of cyber attacks, a robust multivariate observer is designed to realize the estimation and separation of uncompromised system states, false data injection attacks, and measurement disturbances, simultaneously. Based on these reconstructed signals and a newly-designed linear robustness constraint, the distributed predictive controller is established to achieve smooth cooperative stabilization among agents. Meanwhile, an event-triggered mechanism is applied to save computing resources, and it restricts the error of predictive states and estimated states to guarantee the feasibility of the optimization control problem. Theoretical analyses on robustness and security for the nonlinear multiagent systems under event-triggered distributed output feedback model predictive control are presented. Finally, a simulation on two pairs of one-link flexible joint manipulator systems verifies the theoretical results.

Adaptive contact-force control and vibration suppression for constrained flexible manipulator with unknown control direction and time-varying actuator fault

A contact-force control and vibration suppression problem for a constrained one-link flexible manipulator with unknown control direction and time-varying actuator fault is discussed in this paper. The manipulator is described by a Partial Differential Equation model. The Nussbaum function is used to solve the unknown control direction and time-varying actuator fault problems. A Nussbaum function provides an adaptive boundary controller constructed to control the contact force to a target and simultaneously eliminate the vibration of the flexible manipulator. The Variable Separation Technique is used along with system boundary conditions to prove the necessary existence and uniqueness of the system solution more concisely than using the common C 0 -semigroup contractions method. Because force sensors are not necessary, the noise caused by a force sensor can be avoided. Numerical simulations verify the effectiveness of the proposed controller-based solution.

Modeling of Flexible-Link Manipulators Under Uncertain Parameters Based on Stochastic Finite Element Method

Abstract This paper presents a novel approach to obtain the dynamic model of flexible-link manipulators based on the stochastic finite element method. The links and elements of flexible manipulators are affected by uncertainties. The main sources of uncertainties include the variation of mechanical properties. The present research study conveys the following contributions: (i) modeling the uncertain parameters such as the stiffness of the links as an extension of the finite element method based on stochastic fields and the stochastic finite element method, (ii) numerical method to simulate the dynamic response of flexible manipulation with uncertain parameters in the links based on the Monte Carlo simulation (MCS), and (iii) numerical application of the proposed method to the one-link flexible manipulator and two-link flexible manipulator. Numerical simulations illustrate the proposed approach in terms of joint responses and frequency response functions subject to uncertain parameters.

An Attempt to Energy-Saving Driving for a Flexible Manipulator by Utilizing MFC

This study deals with the positioning control problem of a one-link flexible manipulator consisting of two actuators which are a servomotor and a piezoelectric film, and then proposes a new feed-forward control method to suppress simultaneously the driving energy and residual vibration. Simulation and experiments were performed to verify the effectiveness of the proposed method. From this verification, it was confirmed that simultaneous optimization of the trajectory of servomotor and the input voltage of the piezoelectric film saves more energy than the only optimization of the trajectory. Therefore, we were able to establish an energy-saving feedforward control method by driving two actuators.

Modelling and State Variable Feedback Control with Proportional Action of a One-Link Flexible Manipulator Incorporating Payload

This paper presents a state variable feedback (SVF) control with proportional gain to control a one-link flexible manipulator incorporating payload. The dynamic model of a one-link flexible manipulator is developed through a finite element method. The system is uncertain due to the variation of payloads and numbers of elements. There is a challenge in designing a controller for each number of elements. To obtain the effectiveness of the controllers, a combination of SVF control-based LQR controls with proportional gain is developed for a flexible link manipulator with payload variations. An assessment is conducted to examine the input tracking controller capability of the hub angular position, deflection, hub velocity and end-point residual of the one-link flexible manipulator. The responses of the system are shown in domains of time and frequency, while the SVF control with proportional gain schemes is also discussed. This study finds that the payload effects on the response incorporating payload with SVF control and proportional gain schemes can provide input tracking performance with zero steady state error.

Bipartite Consensus and Distributed Boundary Control for Multiple Flexible Manipulators Associated With Signed Digraph

This article investigates the networked multiple one-link flexible manipulators system communicating through a signed digraph, in which the dynamic of each submanipulator is described by the PDE-ODE hybrid model. A distributed boundary control protocol is proposed to realize bipartite consensus of joint angles and vibration suppression. To overcome the flexible dynamics, novel variables are introduced in the protocol to suppress the vibrations. The single zero eigenvalue brought by the Laplacian matrix is ignored for avoiding singularity, and the exponential stability of the reduced-order system is strictly proven by means of semigroup theory. Based on the estimations of integral terms in the novel variables, the necessary and sufficient conditions are finally obtained. Numerical simulations are presented to illustrate the effectiveness of the proposed protocol.

Distributed Fault Estimation for a Class of Nonlinear Multiagent Systems

This paper is devoted to the problem of distributed fault estimation for multiagent systems with nonlinear dynamic. For each agent, an augmented system can be obtained by treating the possible fault as a special system state. Utilizing the output of the neighbor agents, the nonlinear fault estimation observer can be constructed in one agent. The possible faults in both this agent and its neighbors can be estimated by the observer. By solving linear matrix inequalities, the parameter matrices of the observer can be computed. The region pole constraint is considered, which can improve the estimation performance. At last, both a numerical simulation and a network of four one-link flexible joint manipulator systems are considered to verify the proposed fault estimation approach.

Flexible Manipulator State Reconstruction Using Luenberger and First Order Sliding Mode Observers Under Parametric Uncertainties

This paper deals with the problem of state reconstruction fora one-link flexible manipulator using Luenberger Observer (LO) and First Order Sliding Mode Observer (FOSMO) under parametric uncertainties.The design techniques and the comparison of the state observers are presented.The mechanical equations of the system are derived using the Lagrangian approach, and the elastic movement is approximated by the assumed modes method for an Euler-Bernoulli beam. The sliding mode observer is derived based on the available outputs, and it is compared to the classical Luenberger one. The simulation results included in the paper evaluate the observers’ ability to reconstruct the state, to lower the error of estimation and to shorten the required time for the error to converge.

Vision-based online vibration estimation of the in-vessel inspection flexible robot with short-time Fourier transformation

The vibration should be suppressed if it happens during the motion of a flexible robot or under the influence of external disturbance caused by its structural features and material properties, because the vibration may affect the positioning accuracy and image quality. In Tokamak environment, we need to get the real-time vibration information on vibration suppression of robotic arm, however, some sensors are not allowed in the extreme Tokamak environment. This paper proposed a vision-based method for online vibration estimation of a flexible manipulator, which is achieved by utilizing the environment image information from the end-effector camera to estimate its vibration. Short-time Fourier Transformation with adaptive window length method is used to estimate vibration parameters of non-stationary vibration signals. Experiments with one-link flexible manipulator equipped with camera are carried out to validate the feasibility of this method in this paper.

Finite element based model predictive control for active vibration suppression of a one-link flexible manipulator

This paper presents a unique approach for active vibration control of a one-link flexible manipulator. The method combines a finite element model of the manipulator and an advanced model predictive controller to suppress vibration at its tip. This hybrid methodology improves significantly over the standard application of a predictive controller for vibration control. The finite element model used in place of standard modelling in the control algorithm provides a more accurate prediction of dynamic behavior, resulting in enhanced control. Closed loop control experiments were performed using the flexible manipulator, instrumented with strain gauges and piezoelectric actuators. In all instances, experimental and simulation results demonstrate that the finite element based predictive controller provides improved active vibration suppression in comparison with using a standard predictive control strategy.

Modeling and nonlinear control of a flexible-link manipulator

The problem of modeling and controlling the tip position of a one-link flexible manipulator is considered. The proposed model has been used to investigate the effect of the open-loop control torque profile, and the payload. The control strategy is based on the nonlinear State Dependent Riccati Equation (SDRE) design method in the context of application to robotics and manufacturing systems. In this paper, an experimental test-bed was developed to demonstrate the concept of end-point position feedback on a single-link elastic manipulator, and the control strategy for a single-link flexible manipulator. The controller is designed based on the nonlinear SDRE developed by the authors and applied to a flexible manipulator. The experimental results are compared with conventional PD controller strategy. The results reveal that the nonlinear SDRE controller is near optimal and robustly; and its performance is improved comparing to the PD control scheme.

Refined Wave-Based Control Applied to Nonlinear, Bending, and Slewing Flexible Systems

The problem of controlling the position and vibration of open-chain flexible structures undergoing fast maneuvers is of wide interest. In this work, the general flexible structure is actuated by a single actuator at one end, which, depending on the case of interest, is capable of rotating, translating, or simultaneously translating and rotating the root of the flexible system. The goal is to control the motion of the entire flexible system from rest to rest. This needs a simultaneous synthesis of position control and active vibration damping. A new strategy is presented based on further developments of wave-based control. As before it views the actuator motion as simultaneously launching and absorbing mechanical waves into and out of the system. But a new simple method of resolving the actuator motion into two waves is presented. By measuring the elastic forces exchanged at the interface between the actuator and the rest of the system, a returning displacement wave can be resolved. This is then added to a set, launch wave to determine the actuator motion. Typically the launch wave is set to reach half the target displacement, and the addition of the return wave absorbs the vibration while simultaneously moving the system the second half of the target displacement, neatly achieving the two goals in one controlled motion. To date wave-based control has been applied to lumped, second-order, longitudinally vibrating systems. The refined method avoids a difficulty that previously arose in some contexts, thereby making wave-based control even more generic. It can easily control nonlinear elastic systems, laterally bending systems (in the sense of Euler–Bernoulli beams), and slewing systems where lateral translation and system rotation are strongly coupled. Numerical simulation results are presented for controlled, rest-to-rest maneuvers of representative flexible structures, all controlled using the same (linear) algorithm. The first case is control of a string of rigid bodies interconnected by nonlinear springs. The second problem is the rotational control of a very flexible one-link planar manipulator. Finally, in an extension of the previous system, the actuator both translates and rotates, slewing the flexible system to a target lateral displacement and a target rotation angle simultaneously. The strategy is found to be remarkably effective with many advantages. It seamlessly integrates position and vibration control. It is rapid, robust, energy efficient, and computationally light. It requires little sensing, little knowledge of the flexible system dynamics, and copes well with nonideal actuator behavior. It is generic and easily handles a wide variety of flexible systems. It can get the entire system to stop dead exactly at target with little vibration in transit.

Reference tracking versus path-following for a one-link flexible robot manipulator

This paper details two control approaches for a flexible manipulator system, where the non-minimum phase problem is treated. In the first approach, we use the motion planning technique. It searches for proper output trajectories with polynomial form, in order to cancel the effects of the unstable zeros. The second approach is called Path-Following with internal model control. Its primary objective is to steer a physical object to converge to a geometric path, and its secondary objective is to ensure that an object's motion along the path satisfies a given dynamic specification.

Active vibration control of a flexible one-link manipulator using a multivariable predictive controller

This article presents a new application of model-based predictive controller (MPC) for vibration suppression of a flexible one-link manipulator using piezoceramic actuators. Simulation and experimental studies were conducted to investigate the applicability of the MPC strategy to control vibration of the flexible structure having multiple inputs and multiple outputs (MIMO). The performance of the proposed technique was assessed in terms of level of vibration reduction. The results demonstrated that the proposed predictive control strategy is well suited for multivariable control of vibration suppression on flexible structures.

Output tracking control of a one-link flexible manipulator via causal inversion

Output tracking control is a challenging problem. This paper introduces a new design procedure for output tracking control of nonminimum phase systems. This new controller achieves stable /spl epsi/-tracking of a reference profile given in real time via a causal inversion approach. In this approach, the nonminimum phase system is first stably inverted on-line to obtain both desired (and stable) state and input trajectories. Then an H/sub /spl infin// optimal controller is used to stabilize the closed-loop system. In contrast to stable inversion, the causal inversion approach does not require precalculation. In contrast to nonlinear regulation, the causal inversion approach avoids the numerical intractability of solving nonlinear PDEs. As an example of the application, a causal inversion-based controller is designed for tip trajectory tracking of a one-link flexible manipulator. Simulation results demonstrate its effectiveness in output tracking.

1リンク柔軟マニピュレータの力制御問題と指数安定性

1リンク柔軟マニピュレータの力制御問題と指数安定性

Boundary stabilization of a flexible manipulator with rotational inertia

We design a stabilizing linear boundary feedback control for a one-link flexible manipulator with rotational inertia. The system is modelled as a Rayleigh beam rotating around one endpoint, with the torque at this endpoint as the control input. The closed-loop system is nondissipative, so that its well posedness is not easy to establish. We study the asymptotic properties of the eigenvalues and eigenvectors of the corresponding operator $\mathcal A$ and establish that the generalized eigenvectors form a Riesz basis for the energy state space. It follows that $\mathcal A$ generates a $C_0$-semigroup that satisfies the spectrum-determined growth assumption. This semigroup is exponentially stable under certain conditions on the feedback gains. If the higher-order feedback gain is set to zero, then we obtain a polynomial decay rate for the semigroup.

C03 1リンクフレキシブルマニピュレータの残留振動抑制のためのモデリングと軌道生成法(OS13-1 一般-1)

This paper presents the optimal trajectory planning for a one-link flexible manipulator to suppress the residual vibration. In the trajectory planning, we express the joint angle by cubic spline function, and then use the tabu search method to find an optimal trajectory. The optimal trajectory thus obtained has minimum vibration requirement. The manipulator is modeled by considering axial inertia based on inextensibility condition. The Lagrangian approach in conjunction with the assumed modes method is applied to obtain the equation of motion of the manipulator that is used in the trajectory planning. The effectiveness of the proposed method is verified by experiments.

1426 1リンクフレキシブルマニピュレータの残留振動抑制のための軌道生成法(GS-10 制御手法,研究発表講演)

This paper presents the optimal trajectory planning for a one-link flexible manipulator to suppress the residual vibration. In the trajectory planning, we express the joint angle by cubic spline function, and then use the tabu search method to find an optimal trajectory. The optimal trajectory thus obtained has minimum vibration requirement. The effectiveness of the proposed method is verified by experiments.

１リンク柔軟マニピュレータのダイナミクスベースト力制御

We discuss a force control problem for a constrained one-link flexible manipulator based on distributed parameter model. The proposed control law consists of bending moment at the root of the flexible manipulator and its derivative, which regulates simultaneously the force and the rotational angle of the motor without the angle and the force information. And it ensures the asymptotic stability of the closed-loop system. As the control law is derived based on the distributed parameter model, we can avoid the drawbacks resulting from finite dimensional approximation.