Integral Disturbance Observer Research Articles

Integrated Disturbance Observer-Based Robust Force Control

For robotic tasks that involve combined transmitting and contact force control, achieving high-performance motion control while ensuring stable environment contact is difficult. Among the factors that affect the quality of this force control, we may account vibrations due to misalignment in the mechanical components, actuator inaccuracies, non-linear effects of friction, and backlash. All the above factors can be collectively considered as force disturbances. Towards high-performance motion control and contact stability, a novel integrated disturbance observer (IDOB) is proposed. The IDOB uses force sensor measurements with position measurements and a plant model to isolate and robustly suppress the effects of force disturbances within the plant without compromising contact stability. This is applied here to a force control system to demonstrate the enhanced force control performance in free space and in contact. The passivity, robust stability, and disturbance rejection of the proposed IDOB are compared with those of existing force controllers, with and without force-based DOBs. Finally, actual experiments are conducted in free space and contact under various interaction conditions, showing that the IDOB improves transmitting force control and disturbance suppression performances. Moreover, peak collision force is reduced while maintaining contact stability with stiff environments.

Prescribed performance control for dynamic positioning vessels with a dynamic event-triggered mechanism

This paper addresses the problem of trajectory tracking control for dynamic positioning vessels in the presence of unknown sea loads. Firstly, an integral disturbance observer is introduced to estimate the unknown sea loads, which enhances the estimation accuracy by incorporating an integral term. Then, a novel second-order prescribed performance function combined with a tracking differentiator is proposed. Compared to traditional performance functions, this function can better enforce error constraints. As a starting point, a Non-full-state event-triggered control (NFSETC) scheme and a full-state event-triggered control (FSETC) scheme are designed to achieve trajectory tracking while addressing environmental uncertainty and limited communication resources. Furthermore, a novel full-state event-triggered mechanism, utilizing a dynamic threshold event-triggered strategy with a performance safety evaluation factor (PSEF), is employed for stable control input, low communication consumption, and improved tracking accuracy. It is also proven that both the event-triggered controller and the full-state event-triggered controller do not exhibit the Zeno phenomenon. Finally, numerical simulations are conducted to verify the theoretical findings and effectiveness of the proposed method.

Automatic carrier landing for UAV based on integrated disturbance observer and fault-tolerant control

PurposeAccurate glide path tracking is vital to the automatic carrier landing task of unmanned aerial vehicle (UAV). The purpose of this paper is to develop a reliable flight controller that can simultaneously deal with external disturbance, structure fault and actuator fault.Design/methodology/approachThe automatic carrier landing task is resolved into the glide path tracking problem and attitude tracking problem. The disturbance observer-based adaptive sliding mode control scheme is proposed for system stabilization, disturbance rejection and fault tolerance.FindingsBoth the Lyapunov method and exemplary simulations can prove that the disturbance estimation error and the attitude tracking error converge in finite time in the presence of external disturbances and various faults.Practical implicationsThe presented algorithm is testified by a UAV automatic carrier landing simulation, which shows the potential of practical usage.Originality/valueThe barrier function is introduced to adaptively update both the sliding mode observer gain and sliding mode controller gain, so that the sliding mode surface could converge to a predefined region without overestimation. The proposed flight controller ensures a secure carrier landing task.

An infinite-order integral disturbance observer for improved estimation of periodic disturbances in motion control systems

ABSTRACT In this paper, a disturbance observer is devised for motion control systems suffering unknown periodic disturbances. In the proposed scheme, the structure of a so-called integral disturbance observer is utilized for its error-feedback form, and the repetitive learning control theory is applied to the observer design, constituting an infinite-order integral disturbance observer to obtain an enhanced estimation of a periodic disturbance. A comparative study of different disturbance observers is performed, and experimental results are reported, practically showing the effectiveness of the proposed scheme.

Sliding Mode Control Approach with Integrated Disturbance Observer for PMSM Speed System

The research on high-performance vector control of permanent magnet synchronous motor (PMSM) drive system plays an extremely important role in electrical drive system. To further improve the speed control performance of the system, a fast non-singular end sliding mode (FNTSM) surface function based on traditional NTSM control is developed. The theoretical analysis proves that the FNTSM surface function has a faster dynamic response and more finite-time convergence. In addition, for the self-vibration problem caused by high sliding mode switching gain, an FNTSM control method with anti-disturbance capability was designed based on the linear disturbance observer (DO), i.e. the FNTSMDO method was employed to devise the PMSM speed regulator. The comparative simulation and experiment results with traditional PI control and NTSM control methods indicate that the FNTSMDO method could improve the dynamic performance and anti-interference of the system.

Event-Based Prescribed Performance Control for Dynamic Positioning Vessels

This brief investigates the problem of trajectory tracking control for dynamic positioning vessels under unknown and time-varying sea loads. A novel event-based prescribed performance control (PPC) scheme is proposed to address this problem. Firstly, an integral disturbance observer (IDO) is introduced to estimate the sea loads, and a new-type performance function (PF), which has advantages of flexible shape and appointed-time convergence, is proposed to form the funnel envelops for the trajectory tracking errors. Subsequently, by employing the IDO and the new-type PF, a dynamic event-triggered control policy is designed in the PPC framework to achieve the assigned trajectory tracking mission in an appointed-time with guaranteed performance bounds and less operating frequency of the actuator. The salient feature of the derived controller is that it can achieve a trade-off between the tracking performance and actuators’ operating frequency in a well-balanced way, which is of great importance for practical engineering applications. Finally, simulation results are given to show the effectiveness of the proposed method.

Integrated Disturbance Observer Attitude Controller for a Satellite with Rotating Solar Array

In this paper, the response of on-orbit satellite attitude under the influence of flexible satellite’s solar array rotation is analysed, and a robust attitude control method based on disturbance observer is proposed. The disturbance torque is estimated and compensated feedforward. The simulation results show that the proposed control method can effectively estimate the external disturbance, and significantly improve the attitude control accuracy and stability.

Event Trigger Super Twisting Sliding Mode Control for DC Micro Grid With Matched/Unmatched Disturbance Observer

In this paper a novel concept of event triggering control (ETC) for effective resource utilization is proposed for dc microgrid. Matched uncertainty elimination is possible through sliding mode control (SMC) itself as addressed in the literatures. This paper proposes a new approach for suppression of both matched and unmatched uncertainties in grid connected and islanded mode through an integral disturbance observer (IDO) which is designed with super twisting SMC to provide dual filtering phenomena pertaining to system perturbations. The IDO facilitates control algorithm to manage effective event counts during disturbance conditions. The proposed controller is designed in order to regulate DC bus voltage and enhance the microgrid capability to perform stable operation in presence of uncertainties. Chattering free finite time convergent SMC is designed with super twisting reaching law to obtain robust behavior of dc microgrid. Results are compared with power rate reaching SMC, Nonlinear disturbance observer (NDO) based controller and PI controller. In the proposed work event triggering condition is designed first time under super twisting reaching law. Comparative assessment is accomplished in lieu of demonstrating the superior performance of event trigger SMC through MATLAB/Simulink and Typhoon based controller hardware in loop (CHIL) platform.

Disturbance Observer-Based Adaptive Finite-Time Attitude Tracking Control for Rigid Spacecraft

This article proposes two kinds of terminal sliding mode control (TSMC) strategies for implementing the finite-time attitude tracking of spacecraft under environmental disturbances and model uncertainties. First, the integral disturbance observer (IDO) is designed to estimate the disturbances and uncertainties. Second, the IDO-based continuous TSMC (CTSMC) method is developed to achieve active disturbance rejection and better tracking performance. Third, to further mitigate the chattering, a modified TSMC (MTSMC) method is constructed by employing an adaptive method and incorporating a piecewise smooth function. Finally, simulations are performed to show the feasibility of the proposed TSMC laws.

DISTURBANCE COMPENSATION TECHNIQUES FOR CONTROLLING PNEUMATIC ACTUATOR SYSTEMS

In this paper, three disturbance compensation algorithms are experimentally evaluated considering the control problem of a rodless pneumatic cylinder. Despite its highly nonlinear dynamics, the pneumatic cylinder is modeled as a linear system including an unknown lumped disturbance. Three disturbance estimation algorithms are then employed to compensate for this lumped disturbance: the traditional linear disturbance observer (TDOB), the integral sliding-mode disturbance observer (I-SDOB) and the IMP-based SDOB (IMP-SDOB). Experimental results are presented to compare these three algorithms in terms of positioning accuracy.

A jerk-constrained time-optimal servo with disturbance compensation

For positioning servo-systems, this paper presents a jerk-constrained time- optimal control (JCTOC) scheme, augmented with an improved disturbance rejection method. In mechanical systems, the jerk that is the time derivative of acceleration may cause many unwanted results when too high. Thus, the JCTOC method is proposed to constrain the system׳s jerk and also obtain a time-optimal characteristic with the constrained jerk. However, because the JCTOC relies on the accuracy of the plant׳s model, system uncertainties and disturbances can adversely affect the output response. Thus, a disturbance observer (DOB) is added for compensation of the perturbation. The DOB used in this paper is in an integral form, and is thus referred to as an integral DOB (IDOB). The IDOB is further enhanced with a dynamic compensator to provide both better noise immunity and asymptotic compensation for disturbances of various orders.

Research on Theodolite Auto-Focus Motor Control Technology Based on a Disturbance Observer

The design of DC servo control system for focus motor is an important part to realize the electronic theodolites auto-focusing. Focus motor is seriously influenced by various disturbances, such as friction and torque fluctuation, in frequently reversing process. It is difficult to accurately locate. To solve these problems, a DC motor control method was put forward which combined the integral separation PID and disturbance observer. Based on the three closed-loop DC servo system, the integral separation PID controller was taken in position loop, in order to eliminate static error and improve the control precision. The methods of motor trajectory planning were analyzed, the 4-5-6-7 interpolation trajectory planning was used to decline or prevent the start-stop impact and oscillation. The effectiveness of the control strategy was verified by comparative simulation experiment. The robustness anti-disturbance and location precision performance is improved significantly.

Wideband Force Control by Position-Acceleration Integrated Disturbance Observer

Motion control is widely used in industry applications. One of its key components is the disturbance observer, which estimates a disturbance torque of a motion system and realizes a robust acceleration control. A disturbance observer observes and suppresses the disturbance torque within its bandwidth. Motion systems have started to spread in society and they are required to have the ability to interact with unknown environments. Such a haptic motion requires much wider bandwidth. However, since the conventional disturbance observer attains the acceleration information by the second-order derivative of a position response, the bandwidth is limited due to the derivative noise. To enlarge the bandwidth of a disturbance observer, this paper proposes a position-acceleration integrated disturbance observer (PAIDO). Since an acceleration sensor is implemented in it, the control performance of the PAIDO is superior to the conventional one. In this paper, the PAIDO is applied to force control and the viability of the proposed method is confirmed by fast Fourier transformation analyses. The experimental results show the viability of the proposed method.