Przemyslaw Herman

Survey on methods of increasing the efficiency of extended state disturbance observers.

This survey presents various methods of improving the overall estimation quality in the class of extended state observers (ESO), which estimate not only the conventional states of the system, but the acting disturbance as well. This type of observers is crucial in forming the active disturbance rejection control structure (ADRC), where the precision of online perturbation reconstruction and cancellation directly influences the robustness of the closed-loop control system. Various aspects of the observer-based disturbance estimation/rejection loop are covered by this work and divided into three categories, related with observer: structure, tuning, and working conditions. The survey is dedicated to researchers and practitioners who are interested in increasing the efficiency of their ADRC-based governing schemes.

Sliding mode control of manipulators using first-order equations of motion with diagonal mass matrix

This paper presents a proposition of a sliding mode controller for a rigid manipulator expressed in terms of the generalized velocity components (GVC) vector. Introduction of GVC (Trans. ASME J. Appl. Mech. 62 (1995) 216) together with generalized positions leads to two first-order decoupled equations of motion instead of a single second-order equation. It is shown that the new controller, stable in the sense of Lyapunov, has different properties and can, according to Slotine and Li (Int. J. Robotics Res. 6 (1987) 49), give better performance than the classical sliding mode controller. Both control algorithms were tested on a 3 d.o.f., 3-D Yasukawa-like robot.

An experimental verification of ADRC robustness on a cross-coupled Aerodynamical System

This paper presents a robustness study of an Active Disturbance Rejection Control (ADRC) framework. An experimental verification is carried out on a Two Rotor Aerodynamical System (TRAS). The cross-couplings and highly nonlinear behavior of this complex system limit the performance of classical and linear controllers, widely-used in industrial practice. Additionally, the obtainment of a reliable mathematical model of TRAS is a challenging and tedious job. In ADRC, the unmeasured dynamics and external disturbance, associated with the 2-DOF motion of TRAS, are treated as an additional state variable. It is then estimated by a Nonlinear Extended State Observer (NESO) and compensated in the control signal. The obtained results showed the effectiveness of proposed ADRC-based controller in coping with dynamic and nonlinear variations, commonly seen in aerodynamical systems. It was noticed that due to disturbance estimation and its further cancellation a precise mathematical model of the plant is not required. The ADRC robustness was compared through experiment with other model-free method, i.e. the proportional-integral-derivative controller (PID). Better outcomes in terms of disturbance rejection have been reported for the ADRC approach.

On the usefulness of higher-order disturbance observers in real control scenarios based on perturbation estimation and mitigation

In this paper, a technique of increasing the effectiveness of estimating the overall system uncertainty with a class of high-gain disturbance observers is discussed. In theory, by introducing a particular set of additional, fictitious states to the system model, the considered observers can more effectively estimate wider variety of disturbances than in their classical forms. This work describes the verification of such theoretical statement also in practice. Both advantages and disadvantages of the proposed framework are pointed out in the paper using an Extended State Observer (ESO), that serves as an working example. An evaluation of the considered technique is carried out through a combination of numerical simulations and laboratory experiments.

Application of Active Disturbance Rejection Control to a reel-to-reel system seen in tire industry

In this paper an Active Disturbance Rejection Control (ADRC) scheme is used to solve a sag control problem that has been noticed in tire production process. Constant length of the rubber sag is crucial in order to achieve high quality of tire reinforcement, which has its direct impact on driver safety. The ADRC method was compared in this research with other model-independent controller, i.e. Proportional-Integral-Derivative (PID), widely used in engineering practice. Both of the techniques were implemented and experimentally verified on a model of tire reinforcement production stage that can be described with a reel-to-reel system (R2R). The effect of various radius in the rubber winding phase makes the R2R a nonstationary dynamic plant. The ADRC approach resulted in better performance both energetically and for tracking a square trajectory, even with the presence of artificially added external disturbance. Additional perturbation imitated unpredictable and surprisingly often phenomena, which are results of incidents that happen in other stages of the manufacturing process. The acquired results have potential importance to the tire industry.

Control of airship in case of unpredictable environment conditions

The article demonstrates how to generate the trajectory, taking into account the concept of the tunnel of error that ensures route trace with an error no greater than assumed, even in difficult to predict environmental conditions. The mathematical model of kinematics and dynamics using spatial vectors is presented in short. The theoretical assumptions are tested by simulation. The model used in the simulations takes into account the structure of the drives in the form of two engines placed symmetrically on the sides of the object.

Modified set-point controller for underwater vehicles

A modified PD (proportional-derivative) controller for autonomous underwater vehicles (AUVs) is presented in this paper. The controller is expressed in terms of first-order equations of motion with a unit inertia matrix. The main difference between the proposed controller and the classical one relies on that the dynamics of the system is taken into account. This property ensures fast error and force convergence to the end-value. The PD controller can be applied for fully actuated AUVs. It is worth noting that the regulator gain matrices are selected based on parameters of the tested vehicle. The stability of the presented control law is proved in the sense of Lyapunov. Moreover, some advantages and observations resulting from the use of the controller are given. The performance of the controller is shown via simulations on a 6-DOF underwater vehicle.

Control of Robot Manipulators in Terms of Quasi-Velocities

In this paper we present new control algorithms for robots with dynamics described in terms of quasi-velocities (Kozłowski, Identification of articulated body inertias and decoupled control of robots in terms of quasi-coordinates. In: Proc. of the 1996 IEEE International Conference on Robotics and Automation, pp. 317–322. IEEE, Piscataway, 1996a; Zeitschrift für Angewandte Mathematik und Mechanik 76(S3):479–480, 1996c; Robot control algorithms in terms of quasi-coordinates. In: Proc. of the 34 Conference on Decision and Control, pp. 3020–3025, Kobe, 11–13 December 1996, 1996d). The equations of motion are written using spatial quantities such as spatial velocities, accelerations, forces, and articulated body inertia matrices (Kozłowski, Standard and diagonalized Lagrangian dynamics: a comparison. In: Proc. of the 1995 IEEE Int. Conf. on Robotics and Automation, pp. 2823–2828. IEEE, Piscataway, 1995b; Rodriguez and Kreutz, Recursive Mass Matrix Factorization and Inversion, An Operator Approach to Open- and Closed-Chain Multibody Dynamics, pp. 88–11. JPL, Dartmouth, 1998). The forward dynamics algorithms incorporate new control laws in terms of normalized quasi-velocities. Two cases are considered: end point trajectory tracking and trajectory tracking algorithm, in general. It is shown that by properly choosing the Lyapunov function candidate a dynamic system with appropriate feedback can be made asymptotically stable and follows the desired trajectory in the task space. All of the control laws have a new architecture in the sense that they are derived, in the so-called quasi-velocity and quasi-force space, and at any instant of time generalized positions and forces can be recovered from order

A comparison of certain quasi-velocities approaches in PD joint space control

O({\cal N})

Model-Free Control or Active Disturbance Rejection Control? On different approaches for attenuating the perturbation

recursions, where