Nonlinear robust control of tendon–driven robot manipulators

This work addresses the position tracking control problem for tendon–driven robotic mechanisms in the presence of parametric uncertainty and additive external disturbances. Specifically, a full state feedback nonlinear robust controller is proposed to tackle the link position tracking problem for tendon–driven robot manipulators with uncertain dynamical system parameters. A robust backstepping approach has been utilized to achieve uniformly ultimately bounded tracking performance despite the lack of exact knowledge of the dynamical parameters and presence of additive but bounded disturbance terms. Stability of the overall system is proven via Lyapunov based arguments. Simulation studies performed on a two link planar robot manipulator driven by a six tendon mechanism are presented to illustrate the effectiveness and viability of the proposed approach.Scientific and Technological Research Council of Turkey (112E561

Nonlinear control of tendon driven robot manipulators: Elimination of actuator side position measurements

54th IEEE Conference on Decision and Control, CDC 2015; Osaka International Convention Center (Grand Cube)5-3-51 Nakanoshima, Kita-KuOsaka; Japan; 15 December 2015 through 18 December 2015In this study, a partial state feedback controller is proposed for the link position tracking control problem of flexible tendon driven robotic systems. Specifically; a nonlinear model based controller is formulated for tendon driven robot manipulators under the constraint that only the link position and tendon expansion force measurements are available. Despite the lack of link and actuator side velocity and actuator position measurements, the proposed controller ensures exponential link position tracking. To eliminate the need of actuator position and velocity measurements, a model based velocity observer has been utilized. Stability of the closed loop system and boundedness of system states are proven via Lyapunov based arguments. The performance of the purposed observer-controller couple is then verified by a set of numerical simulations

Nonlinear robust control of 3 phase inverter with output LC filter

19th IFAC World Congress on International Federation of Automatic Control, IFAC 2014; Cape Town; South Africa; 24 August 2014 through 29 August 2014Three phase inverters are commonly used to transfer energy from a source to the power grid. The quality of the power delivered to the grid, can be ensured via the use of an output LC filter. However inserting an output filter to an inverter circuitry would introduce new challenges to the controller design due to the additional parametric uncertainties imposed. In this study we present a new model based robust controller for a three phase inverter with output LC filter under the constraint that the output filter parameters are not exactly known. Specifically, d-q reference frame model of an inverter with output LC filter is used to develop a nonlinear robust controller that ensures the 3-phase output voltage with desired amplitude and frequency and with lowest harmonic distortion. Stability of the proposed method and the boundedness of the closed-loop system, is established via Lyapunov based tools in conjunction with a robust backstepping procedure. Simulation results are given in order to demonstrate performance and effectiveness of the proposed robust controller. © IFAC

Nonlinear adaptive partial state feedback trajectory tracking control of tendon driven robot manipulators

2014 IEEE Conference on Control Applications, CCA 2014; Juan Les Antibes; France; 8 October 2014 through 10 October 2014In this work, the link position tracking control problem of a tendon driven robotic system is studied in the presence of parametric uncertainty and lack of velocity measurements both of links and actuators. A partial state feedback nonlinear adaptive controller is proposed to deal with the unmeasurable states and uncertain dynamical system parameters. A backstepping approach has been utilized to develop the control strategy. The proposed nonlinear tracking controller utilizes online update laws to adapt for parametric uncertainties, and requires only link and actuator position measurements and tendon tension measurements. Need for link velocity measurements are eliminated by using a nonlinear filter, and a set of linear filters is designed to estimate the actuator velocities. Lyapunov based arguments have been applied to prove the stability of the closed-loop system and semi-global asymptotic link position tracking is achieved. © 2014 IEEE

Observer based output feedback control of thrust magnetic bearings

50th IEEE Conference on Decision and Control and European Control Conference, CDC-ECC 2011; Orlando, FL; United States; 12 December 2011 through 15 December 2011In this paper, we present an observer based output feedback controller for a thrust magnetic bearing system. A model independent variable structure like observer is used to determine the rotor velocity in order to remove the velocity dependency of the controller. The desired system dynamics have been utilized in the controller design and asymptotic stability of the observer-controller couple is guaranteed via Lyapunov based arguments. Experimental results are presented to illustrate the performance and feasibility of the proposed method. © 2011 IEEE