Disturbance Observer-based Robust Control and Its Applications: 35th Anniversary Overview

Disturbance Observer has been one of the most widely used robust control tools since it was proposed in 1983. This paper introduces the origins of Disturbance Observer and presents a survey of the major results on Disturbance Observer-based robust control in the last thirty-five years. Furthermore, it explains the analysis and synthesis techniques of Disturbance Observer-based robust control for linear and nonlinear systems by using a unified framework. In the last section, this paper presents concluding remarks on Disturbance Observer-based robust control and its engineering applications.Comment: 12 pages, 4 figure

Central controller for hybrid control over network

In this paper, a central controller for position/force hybrid control over network is proposed. In the proposed method, the central controller receives position and force information from each plant. Then, the central controller generates acceleration references for each plant by using a hybrid controller and a dead time compensator. As an application, bilateral control with communication delay is implemented. And some simulations and experiments verify the validity of the proposed method

A Stability Analysis for the Acceleration-based Robust Position Control of Robot Manipulators via Disturbance Observer

This paper proposes a new nonlinear stability analysis for the acceleration-based robust position control of robot manipulators by using Disturbance Observer (DOb). It is shown that if the nominal inertia matrix is properly tuned in the design of DOb, then the position error asymptotically goes to zero in regulation control and is uniformly ultimately bounded in trajectory tracking control. As the bandwidth of DOb and the nominal inertia matrix are increased, the bound of error shrinks, i.e., the robust stability and performance of the position control system are improved. However, neither the bandwidth of DOb nor the nominal inertia matrix can be freely increased due to practical design constraints, e.g., the robust position controller becomes more noise sensitive when they are increased. The proposed stability analysis provides insights regarding the dynamic behavior of DOb-based robust motion control systems. It is theoretically and experimentally proved that non-diagonal elements of the nominal inertia matrix are useful to improve the stability and adjust the trade-off between the robustness and noise sensitivity. The validity of the proposal is verified by simulation and experimental results.Comment: 9 pages, 9 figures, Journa

Control of interconnected mechanical systems

In this paper control systems design approach, based on siding mode methods, that allows maintain some functional relation – like bilateral or multilateral systems, establishment of virtual relation among mobile robots or control of haptic systems - is presented. It is shown that all basic motion control problems - trajectory tracking, force control, hybrid position/force control scheme and the impedance control for the interacting systems- can be treated in the same way while avoiding the structural change of the controller and guarantying stable behavior of the system In order to show applicability of the proposed techniques simulation and experimental results for high precision systems in microsystems assembly tasks are presented.

Sliding modes in constrained systems control

Abstract—In this paper, a sliding-mode-based design framework for fully actuated mechanical multibody system is discussed. The framework is based on the possibility to represent complex motion as a collection of tasks and to find effective mapping of the system coordinates that allows decoupling task and constraint control so one is able to enforce concurrently, or in certain time succession, the task and the constraints. The approach seems naturally encompassing the control of motion systems in interaction, and it allows application to bilateral control, multilateral control, etc. Such an approach leads to a more natural interpretation of the system tasks, simpler controller design, and easier establishment of the systems hierarchy. It allows a unified mathematical treatment of task control in the presence of constraints required to be satisfied by the system coordinates. In order to show the applicability of the proposed techniques, simulation and experimental results for high-precision systems in microsystem assembly tasks and bilateral control systems are presented

Bilateralno upravljanje gibanjem za apstrakciju i reprodukciju stvarne sile

In recent years, skill preservation of an expert and skill education for young technical workers have been serious issues in medical and production fields. The best way which young technical workers learn the ripe skill is that an expert teaches them. However, unfortunately, experts have lessened in these years. So, if digital skill preservation like a haptic database is attained, it may become an innovative solution of the above problem. Thus, as the fundamental technology for development of the haptic database, this paper proposes abstraction and reproduction methods on bilateral control of real world force sensation, and reconstruction of real world environment as well. In the abstraction mode, a master-slave system is composed, and the action-reaction law is attained through bilateral control. Later, based on acceleration information, the force, position and velocity of both master and slave systems are estimated and obtained. In the reconstruction mode, an environmental model is reconstructed based on the obtained data from real-world. Next, by using reproduction mode on master side, the operator would feel the force sensation from the obtained environmental model. Here, the proposed system is able to store the bilateral real-world force sensation to a sensation database. Finally, the experimental results show the validity of the proposed method.Održavanje sposobnosti iskusnih operatera i uvježbavanje novih operatera postaje sve važnijim zadatkom u medicinskim i proizvodnim primjenama. Nove operatere najbolje uvježbavaju iskusni operateri, ali njih sve više nedostaje. Inovativno rješenje toga problema može biti pohranjivanje vještina iskusnih operatera u tzv. haptičku bazu podataka. U ovome se članku za razvoj haptičke baze podataka predlažu metode apstrakcije i reprodukcije stvarne sile u bilateralnom upravljanju te metoda rekonstrukcije udaljenoga stvarnoga prostora u kojemu djeluje prateći sustav. U apstrakcijskom načinu rada uspostavlja se bilateralno upravljanje između vodećeg i pratećeg sustava uz održavanje zakona akcije i reakcije između njih. Nakon toga estimiraju se sila, brzina i pozicija vodećeg i pratećeg sustava na temelju informacije o ubrzanju. U rekonstrukcijskom načinu rada rekonstruira se model udaljenoga stvarnoga prostora na osnovi podataka iz stvarnoga udaljenoga prostora. Na koncu, primjenom reprodukcijskog načina rada na strani vodećeg sustava operater bi trebao osjećati silu iz modela udaljenog prostora izgrađenog u rekonstrukcijskom načinu rada. Predloženi sustav omogućuje spremanje bilateralno prenošene sile u bazu podataka, što je potkrijepljeno eksperimentalnim rezultatima

Robusni sustav upravljanja gibanjem preko komunikacijske mreže zasnovan na rekonstrukciji poremećaja

The aim of this paper is to realize robust network motion control system. One of the most significant issues for network motion control realization is time delay during transmission. Obviously, most time delay systems are unstable. Additionally, time delay may cause control performance degradation in motion control system. In this paper, a modified disturbance observer with Smith predictor is proposed to compensate time delay. This modification realizes a robust two-degree-of-freedom control system ower network. The serial compensation of Smith predictor is utilized to compensate time delay. The validity of the proposed method is confirmed by the position control of linear motor over network experimentally. Experimental results show that the proposed control system has robustness against transmission delay fluctuation over network and external force.Cilj je ovoga članka realizacija sustava upravljanja gibanjem preko komunikacijske mreže. Jedan od najvećih problema u realizaciji sustava upravljanja gibanjem preko komunikacijske mreže jest kašnjenje u prijenosu podataka. To kašnjenje dovodi do narušavanja svojstava sustava upravljanja gibanjem, a može ga učiniti i nestabilnim. Za kompenzaciju kašnjenja u radu se predlaže modificirani rekonstruktor poremećaja zasnovan na Smithovu prediktoru. Predloženi rekonstruktor omogućuje izvedbu robusnog sustava upravljanja gibanjem s dva stupnja slobode. Valjanost predloženog sustava potvrđena je eksperimentalno na sustavu upravljanja pozicijom linearnog motora preko komunikacijske mreže. Dobiveni rezultati pokazuju robusno vladanje predloženog sustava u uvjetima promjenjivog kašnjenja prijenosa podataka preko mreže i pri djelovanju vanjske sile