Finite-time Sliding Mode Observer Research Articles

Chattering Free Sliding-Mode Controller Design for Underactuated Tower Cranes With Uncertain Disturbance

Tower cranes are widely used in various industrial sites and require a high level of anti-disturbance performance from the crane controller due to the variability of the application environment. Although sliding mode control is a typical anti-disturbance control method, most sliding mode controllers suffer from output chattering and do not reflect well under severe external disturbances. To address these issues from a practical application perspective, a finite time sliding mode control method using the super-twisting algorithm (STA) is proposed for underactuated tower cranes operating in the presence of external disturbances. The proposed method includes a finite-time chattering-free sliding mode controller that eases the output torque chattering problem and a finite-time sliding mode observer based on STA to observe the uncertain disturbances. The observed values are then applied to the controller through feedforward compensation. Experimental results show that the proposed control method effectively weakens output torque chattering, compensates for disturbance quickly, and accurately completes control tasks.

Output feedback backstepping control for non-linear systems using an adaptive finite time sliding mode observer

Abstract In this paper, a class of non-linear systems in normal form is considered, which is composed of internal and external dynamics. An adaptive finite time sliding mode observer is first designed so that the system states, unmatched uncertain parameters and matched uncertainties can all be observed in finite time. Then, the systematic backstepping design procedure is employed to develop a novel output feedback backstepping control (OFBC). The proposed OFBC method can stabilize the considered non-linear systems despite the presence of non-linear internal dynamics and unmatched uncertainties. A Lyapunov method is used to ensure that the closed-loop system is asymptotically stable. Two MATLAB simulation examples are used to demonstrate the method.

A Robust Fault Diagnosis for Quad-Rotors: A Sliding-Mode Observer Approach

This article presents the design of a fault diagnosis strategy to deal with faults in multiple actuators in a quad-rotor under the influence of external disturbances. The faults are modeled as partial loss of effectiveness. The proposed fault diagnosis strategy is based on a finite-time sliding-mode observer that estimates the full state and provides a set of residuals using only the output information. Moreover, such a strategy is able to detect, isolate, and identify faults in multiple actuators despite the presence of external disturbances. Experimental results on the Quanser’s QBall 2 platform show the performance of the proposed scheme.

Design of Robust Terminal Sliding Mode Control for Underactuated Flexible Joint Robot

Flexible joint robot (FJR) manipulators can offer many attractive features over rigid manipulators, including light weight, safe operation, and high power efficiency. However, the tracking control of the FJR is challenging due to its inherent problems, such as underactuation, coupling, nonlinearities, uncertainties, and unknown external disturbances. In this article, a terminal sliding mode control (TSMC) is proposed for the FJR system to guarantee the finite-time convergence of the systems output, and to achieve the total robustness against the lumped disturbance and estimation error. By using two coordinate transformations, the FJR dynamics is turned into a canonical form. A cascaded finite-time sliding mode observer (CFTSMO) is constructed to estimate states and lumped disturbance in a finite time based on two measurable states, which not only attenuates the measurement noise but also reduces the peaking phenomenon. The closed-loop stability and the finite-time convergence are rigorously proved by using Lyapunov theorem. The upper bound of the finite convergence time is derived for the reaching and sliding phase. Comparative study is conducted experimentally in real time on the FJR manipulator to verify the effectiveness of the proposed control method.

Dynamic Modeling and Control Law Design of a Fuel-electric Hybrid Multi-rotor UAV

In this paper, the design of control law for a new concept fuel-electric hybrid multi-rotor UAV with lift/attitude control separation is investigated. The remarkable feature of the UAV is that it has a large proportion of fuel weight. Firstly, based on the quasi-coordinate Lagrangian equation and sloshing equivalent model using the multi-mass-spring analogy, the non-linear dynamic model of the UAV considering the fuel slosh dynamics is established. Compared with the existing multi-rotor modeling method, it is more intuitive and accurate to describe the non-linear coupling process of sloshing and UAV's motion degrees of freedom. Secondly, the attitude control law is designed based on the finite-time sliding mode observer and cascaded continuous sliding mode controller to eliminate the adverse effects of fuel sloshing and mass changing, and only using the measurable angles. Furthermore, aiming at the problem of power redundancy of the altitude channel, a memoryless non-linear altitude authority assignment controller based on vertical acceleration is proposed for improving the control performance. Finally, the simulation results of the waypoint flight illustrate the feasibility and effectiveness of the proposed control strategy.

Formation Control for Heterogeneous Spatial Underactuated Vehicles Using Bearing Measurements

In this work, we solve the distributed formation control problem for heterogeneous spatial underactuated vehicles subject to switching topologies. We consider the spatial rigid body model of vehicles with one translational actuator for propulsion and three rotational actuators. A finite-time sliding mode observer is designed to estimate the ranges between vehicles based on the bearing measurements. A generalized Slotine-Li transformation is proposed to define continuous reference velocity trajectories under switching topologies. Based on the cascade structure, a distributed formation protocol is presented which guarantees the global asymptotic convergence for the closed-loop system. Numerical simulations on a group of spatial underactuated vehicles including quadcopters and underwater vehicles are presented.

Active vibration control for GyroWheel based on sliding mode observer and adaptive feedforward compensator

This article proposes an active vibration control method for the GyroWheel to ensure the attitude stability precision of the spacecraft. The method includes sliding mode disturbance observer and adaptive feedforward compensator. First, considering the disturbance torque caused by rotor imbalance, the dynamic equation adopting complex coefficients is derived with synchronous disturbances. To reduce the influence of model parameter perturbation, a finite time sliding mode observer is designed to estimate the rotor imbalance owing to its robustness. An integrator for the switching term is introduced in the sliding manifold, which attenuates the chattering phenomenon. Then, the observed unbalanced torque is utilized to generate the reference compensation tilting angle, which is fedforward to the command value to offset the synchronous frequency current. A variable step size seeking algorithm is adopted to tune the feedforward compensator gain adaptively. Finally, both numerical simulations and experiments have verified the effectiveness of the active vibration control scheme, achieving clean vibration torque.

Composite Speed Control of PMSM Drive System Based on Finite Time Sliding Mode Observer

The robust nonlinear speed control technique has been proposed for the speed regulation of permanent magnet synchronous motor (PMSM) by adopting a new fast terminal sliding mode control (FTSMC) based on the finite time sliding mode observer (FTSMO). The proposed technique can ensure the robustness against load disturbances, which has the capability of high tracking precision, fast finite time convergence and smooth dynamic operation in both transient and steady state conditions. Moreover, the requirement of high switching gain to reach the upper bound limit of total disturbances may produce the steady state error and chattering. To address this issue, one robust FTSMO based FTSMC is designed to alleviate those limitations aforementioned. The FTSMO can successfully estimate the total disturbances of the system, then the estimated disturbances can be compensated by the feed-forward compensation technique. The FTSMO based FTSMC should require the smaller switching gain to meet upper bound limit of the disturbances compared with the conventional SMC (CSMC) and FTSMC. The stability of the close loop control system is fully verified by the Lyapunov theory. Comprehensive simulation and experimental results have fully demonstrated that the proposed method is robust against load disturbances.

Finite‐time super twisting sliding mode controller based on higher‐order sliding mode observer for real‐time trajectory tracking of a quadrotor

The main focus of this study is to develop a finite-time super-twisting sliding mode control strategy for the quadrotor based on a higher-order sliding mode observer (HOSMO). 12 state variables are required to describe the motion of the quadrotor, of which six state variables, namely the position, altitude, and orientation, are assumed to be obtained from the sensors. The remaining state variables, i.e. the linear and angular velocities, are determined using the HOSMO. Besides, the HOSMO aids in determining the unknown bounded lumped disturbances acting on the quadrotor. The output of the HOSMO is utilised for implementing the finite-time super-twisting sliding mode controller (FTSTSMC). The proposed FTSTSMC ensures finite-time convergence of tracking error with chattering attenuation. The chattering analysis for a super-twisting algorithm is presented in this work. Moreover, the overall system stability is investigated using the Lyapunov theory, and an expression for the time of convergence of the tracking and estimation error is presented. The effectiveness of the proposed methodology is established using numerical simulations and its performance is compared to a finite-time sliding mode observer coupled with a combination of proportional–integral–derivative and continuous sliding-mode controller. This is then validated in real-time using the DJI Matrice 100.

Comparative analysis of continuous sliding-modes control strategies for quad-rotor robust tracking

This paper presents a comparative analysis involving four Continuous Sliding-Modes Control (Continuous-SMC) algorithms and a robustified PID control for a Quad-Rotor that can be used to deal with the tracking problem under the influence of external disturbances and uncertainties only by means of the measurable positions and angles. Such an approach is composed of a Finite-Time Sliding-Mode Observer (FT-SMO), which estimates the full state and identifies some type of disturbances, and a robust control strategy for underactuated systems. Several real-time experimental tests are carried out on the Quad-Rotor QBall2 platform by Quanser\\protect \\protect \\relax \\special {t4ht=©} under the influence of wind gusts and load disturbances. A quantitative comparison analysis is performed for all of the proposed controllers in order to illustrate their robustness properties.

Finite-Time Sliding Mode Observer for Uncertain Nonlinear Flexible Manipulators with Unknown Disturbance

Finite-Time Sliding Mode Observer for Uncertain Nonlinear Flexible Manipulators with Unknown Disturbance

Quad-Rotor robust time-varying formation control: a Continuous Sliding-Mode Control approach

ABSTRACT This paper deals with the robust tracking problem for a group of Quad-Rotors forming a time-varying geometric pattern, i.e. formation control, in the presence of external disturbances. Such a robust control strategy is able to deal with any formation scheme such that there exists a directed spanning tree from the leader agent to all other agents. The proposed output-control strategy is based on a Continuous Sliding-Mode Control (Continuous-SMC) approach which is composed of a Finite-Time Sliding-Mode Observer (FT-SMO) and hierarchical cascade Continuous-SMCs. It is assumed that only the positions and angles of each Quad-Rotor are available to measure. Despite the disturbances acting on all the Quad-Rotor dynamics, this control strategy provides uniform finite-time stability for the altitude and yaw angle tracking and formation errors, and uniform exponential stability for the forward and lateral tracking and formation errors. Moreover, four different types of Continuous-SMCs can be used in the proposed strategy. Numerical simulations illustrate the performance of the proposed strategy.

Adaptive output feedback integral sliding mode attitude tracking control of spacecraft without unwinding

This article studies an output feedback attitude tracking control problem for rigid spacecraft in the presence of parameter uncertainties and external disturbances. First, an anti-unwinding attitude control law is designed using the integral sliding mode control technique to achieve accurate tracking responses and robustness against inertia uncertainties and external disturbances. Next, the derived control law is combined with a suitable tuning law to relax the knowledge about the bounds of uncertainties and disturbances. The stability results are rigorously proved using the Lyapunov stability theory. In addition, a new finite-time sliding mode observer is developed to estimate the first time derivative of attitude. A new adaptive output feedback attitude controller is designed based on the estimated results, and angular velocity measurements are not required in the design process. A Lyapunov-based analysis is provided to demonstrate the uniformly ultimately bounded stability of the observer errors. Numerical simulations are given to illustrate the effectiveness of the proposed control method.

Super twisting algorithm-based step-by-step sliding mode observers for nonlinear systems with unknown inputs

This article highlights the interest of step-by-step higher order sliding mode observers for Multi-Input Multi-Output (MIMO) nonlinear systems with unknown inputs. A structural matching condition, commenting on the possibility to design such observers and to reconstruct the unknown inputs, is derived. A finite time sliding mode observer, based on the hierarchical use of the super twisting algorithm, is developed. Then, it is shown that this observer is of interest in the field of hybrid systems and systems with observability singularities. Lastly, it is shown through an example how to relax the usual matching condition by the means of this type of finite time sliding mode observer.