Composite nonlinear bilateral control for teleoperation systems with external disturbances

This paper presents the design of a state convergence (SC)-based bilateral controller for a nonlinear teleoperation system, which has been approximated by a Takagi–Sugeno (TS) fuzzy model. The selection of SC is made due to the advantages offered by this scheme both in the modeling and control design stages. The modeling stage considers master/slave systems, which can be represented by the $n$ th order differential equations, while the control design stage offers an easy way to determine the control gains required for assigning desired closed loop dynamics to teleoperation system. After the master/slave systems are represented by TS fuzzy models, a stabilizing fuzzy law is adopted which allows deploying the SC scheme with all its benefits to design the fuzzy bilateral controller. In this way, not only the simplicity of the design scheme is ensured but also the existing SC scheme is able to control a nonlinear teleoperation system based on its TS fuzzy model description. As an additional advantage, the SC-based existing linear bilateral controller can be easily derived from the SC-based proposed fuzzy bilateral controller. Various cases of master/slave systems originally reported in terms of their linear model representation and communication in the absence/presence of time delay are all discussed in the corresponding fuzzy framework. The MATLAB simulations, considering a one-degree-of-freedom teleoperation system, are performed to validate the proposed methodology for controlling a nonlinear teleoperation system.

Sensor-based force decouple controller design of macro–mini manipulator

Composite nonlinear control with state and measurement feedback for general multivariable systems with input saturation

Many robotics researchers have focused on stability in free and constrained motions, but only a few of them have considered system stability in the transition between these phases. For a teleoperation system, due to delay effects, studying this concept is even more crucial. Recently, passivity-based controller stability has been studied in free motion and constrained mode of a teleoperation system in the presence of constant time delay. However, the controller does not guarantee arbitrary switching between these modes. In this paper, a hybrid system theorem was employed to treat delayed teleoperative tasks that involve phase transition or switching. Applying this theorem, the stability of passivity-based architecture in transition was studied. It was proved that this type of controller is stable even with arbitrary switching. Experiments on a two-degrees-of-freedom nonlinear teleoperation system were conducted to verify the approach. Experimental results have shown that passivity-based architecture, as expected in controller design, is well suited for delayed teleoperation in transition. Moreover, even without force sensing, the system’s force tracking in dealing with a hard environment is admissible.

Transportation electrification involves the wide utilization of power electronics based dc distribution networks and the integration of a large amount of power electronic loads. These power electronic loads, when tightly controlled, behave as constant power loads (CPLs) and may cause system instability when interacting with their source converters. In this paper, a composite nonlinear controller is proposed for stabilizing dc/dc boost converter feeding CPLs by integrating a nonlinear disturbance observer (NDO)-based feedforward compensation with backstepping design algorithm. First, the model is transformed into the Brunovsky's canonical form using the exact feedback linearization technique, to handle the nonlinearity introduced by the CPL. Second, the NDO technique is adopted to estimate the load power variation within a fast dynamic response, serving as a feedforward compensation to increase the accuracy of output voltage regulation. Then a nonlinear controller is developed by following the step-by-step backstepping algorithm with strictly guaranteed large signal stability. The proposed controller not only ensures global stability under large variation of the CPL but also features fast dynamic response with accurate tracking over wide operating range. Both simulations and experiments are conducted to verify the proposed strategy.

Dead-zone is one of the most common hard nonlinearities ubiquitous in master–slave teleoperation systems, particularly in the slave robot joints. However, adaptive control techniques applied in teleoperation systems usually deal with dynamic uncertainty but ignore the presence of dead-zone. Dead-zone has the potential to remarkably deteriorate the transparency of a teleoperation system in the sense of position and force tracking performance or even destabilizing the system if not compensated for in the control scheme. In this paper, an adaptive bilateral control scheme is proposed for nonlinear teleoperation systems in the presence of both uncertain dynamics and dead-zone. An adaptive controller is designed for the master robot with dynamic uncertainties and the other is developed for the slave robot with both dynamic uncertainties and unknown dead-zone. The two controllers are incorporated into the four-channel bilateral teleoperation control framework to achieve transparency. The transparency and stability of the closed-loop teleoperation system is studied via a Lyapunov function analysis. Comparisons with the conventional adaptive control which merely deal with dynamic uncertainties in the simulations demonstrate the validity of the proposed approach.

This paper concerns the finite time tracking control problem for the longitudinal model of an airbreathing hypersonic vehicle (AHV) with actuator faults and external disturbances. First, the dynamics of system outputs V and h are given by calculating the differentials. Next, combining external disturbances and actuator additive faults as lumped disturbances, a nonlinear disturbance observer (NDOB) is designed to estimate them. Then, two integral sliding mode manifolds are designed based on tracking errors. Finally, combining NDOB and integral sliding mode control (SMC) techniques, a composite fault tolerant controller is constructed for the longitudinal model of an AHV. This control approach can make the velocity and altitude track the reference signals in finite time and reduce chattering phenomenon caused by SMC. Simulation results are given to show the effectiveness of the proposed control method.

A novel position and force coordination approach in four channel nonlinear teleoperation

<span>In this article a novel composite control technique is introduced. We added a nonlinear disturbance observer to a nonlinear H_∞ control to form this composite controller. The quadrotor kinematics and dynamics is formulated using euler angles and parameters. After that, this nonlinear robust controller is developed for this flying robot attitude control for the outdoor conditions. Because under these conditions the flying robot, experiences both external disturbance and parametric uncertainty. Stability analysis is also presented to show the global asymptotical stability using a Lyapunov function. The simulation results showed that the suggested composite controller had a better performance in comparison with a nonlinear H_∞ control scheme.</span>

The random time delay brings great challenges to the controller design for the Internet-based teleoperation system, the worst case is that it can destabilize the Internet-based teleoperation system. This paper first gives a brief historical preview of bilateral passive control theory, and then a direct passive scattering transform method, extending the passive bilateral control method to the Internet-based random time delay teleoperation system, is advanced to guarantee the teleoperation system's stability with any non-symmetric random network time delay. Finally, a virtual master-slave manipulator bilateral control scheme is designed for mobile robot teleoperation based on the passive scattering transformation method, and simulations are carried out to verify the results at the end of this paper. © 2012 IEEE.

Nowadays the feedback linearization and backstepping techniques are introduced as methods for linearization of a system with coordinate transformation and nonlinear designing, respectively. The feedback linearization and backstepping techniques are robust methods, however this study indicates that combining of them and adding nonlinear disturbance observer increases the system robustness. In this paper, the system linearization with backstepping process has been studied. Combining of above mentioned techniques has been used for linearization in this method. The systems have been practically exposed to disturbances and uncertainties. Nonlinear disturbance observer has a good ability to estimate disturbances and nonlinear dynamics, so it is useful method for increasing performance of control methods, reducing the effects of disturbances and system uncertainties. The presented control method with nonlinear disturbance observer improves the system robustness against different types of uncertainties, so this method is a modified technique. The proposed design process consists of two steps: First, the nonlinear disturbance observer has been designed to estimate the uncertainties and external disturbances applied to system. Second, a controller has been designed using combined feedback linearization-backstepping method that used prior estimations to decrease the effects of external disturbances and uncertainties in the control input.

Dynamic event-triggered composite anti-disturbance fault-tolerant tracking control for ships with disturbances and actuator faults

In the large-area multidevice linkage-based laser processing, using the traditional control method cannot guarantee the processing accuracy of a permanent magnet linear motor (PMLM) system for a high-speed subject, due to unknown model uncertainties, backlash-like hysteresis, states constraints, and external disturbance. To address this shortcoming, this article develops a disturbance observe-based adaptive neural control for the PMLM system. First, aiming at the problem of unknown and uncertain system parameters, this study uses a radial basis neural network to estimate unknown functions of the system. Then, an adaptive variable is introduced to compensate for the effect of unknown backlash-like hysteresis, and the barrier Lyapunov function is used to restrict the motor from operating in a specified area. In addition, a nonlinear disturbance observer is constructed to adapt to the actual processing to reduce the influence of the external disturbance and the system load change. The proposed control scheme is verified experimentally, and the results indicate that when the proposed method is used, the PMLM system is consistently bounded by using the Lyapunov theorem. Finally, the simulation and experimental results verify the effectiveness of the proposed control strategy. The proposed method could be applied to laser-processing equipment.

An EPCH Control Strategy for Complex Nonlinear Systems with Actuator Saturation and Disturbances

This paper proposes a disturbance observer supported Takagi-Sugeno (TS) fuzzy model-based control scheme for uncertain systems. The baseline controller is a guaranteed performance fuzzy model based parallel distributed controller (PDC) which is constructed using the nominal system’s parameters. The model approximation error and parametric uncertainties are treated as a lumped disturbance and a nonlinear disturbance observer (NDOB) is introduced to counter the lumped disturbance. The applicability of the proposed scheme is demonstrated on the bilateral control of nonlinear teleoperation system in MATLAB/Simulink/QUARC environment through simulations as well as semi-real time experiments.