Most robotic systems consist of heavy machine elements that help reduce the vibrations generated by motion and that support good positional accuracy. Large-sized actuators are needed for such systems. Energy consumption significantly increases in oversized robotic systems. The proposed solution to which is to design robotic systems in lightweight and flexible forms. This makes possible smaller overall structure and actuator sizes. However, such systems suffer from residual vibrations. One well-known control solution to residual vibration problem could be input shaping techniques. In this study, a new Fuzzy Logic-based intelligent input shaping selection technique has been proposed. With this proposed approach, it is possible to set optimum settling time, positioning accuracy of robotic systems, and minimum residual vibrations by implementing the crucial open-loop control approach. Comprehensive experience is needed to overcome design issues on command shaping and system modeling. Based on these design criteria constraints and extensive knowledge requirements, the recommended solution is a Fuzzy Logic-based intelligent input shaping technique for accurate modeling and parameter estimation of the systems. The proposed approach is a Fuzzy Logic-based intelligent input shaper selection and input shaper setting determination algorithm. The applicability of the proposed method was verified on the Quanser Flexible Link experimental setup.

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.

@article{maddalena_2018,
title = {Control with Sensor Fault Tolerance for an Underactuated Linear Positioning System Using the TFL/LTR Technique},
author = {Maddalena, E.T.; Kienitz, K.H.},
journal = {Journal of Control, Automation and Electrical Systems},
year = {2018},
month = {10},
volume = {29},
number = {5},
institution = {Insituto Tecnologico de Aeronautica Sao Jose dos Campos, Brazil},
abstract = {In this work, the applicability of a Lyapunov filter-based target feedback loop/loop transfer recovery controller to open-loop unstable plants is investigated on an underactuated linear positioning mechanism. Uncertainties in friction coefficients are taken into account. Lyapunov filter target loops yield robustly stable dynamics and tolerance to abrupt sensor faults, i.e., sensors affected by any attenuation in the interval [0, 1). Experimental results confirm the effectiveness of the proposed solution when compared to alternative control methods. },
issn = {2195-3880},
keywords = {Robust control, TFL/LTR controllers, Fault tolerance, Underactuated systems},
language = {English},
publisher = {Springer US}
}

In this work, the applicability of a Lyapunov filter-based target feedback loop/loop transfer recovery controller to open-loop unstable plants is investigated on an underactuated linear positioning mechanism. Uncertainties in friction coefficients are taken into account. Lyapunov filter target loops yield robustly stable dynamics and tolerance to abrupt sensor faults, i.e., sensors affected by any attenuation in the interval [0, 1). Experimental results confirm the effectiveness of the proposed solution when compared to alternative control methods.

@article{colombo_2016,
title = {Robust Model Predictive Control of a Benchmark Electromechanical System},
author = {Jose Roberto Colombo Junior; Rubens Junqueira Magalhaes Afonso; Roberto Kawakami Harrop Galvao; Edvaldo Assuncao},
journal = {J Control Autom Electr Syst},
year = {2016},
abstract = {This paper presents an experimental investigation concerning the use of robust model predictive control (RMPC) for a two-mass_spring system. This benchmark system has been employed as a numerical simulation example in several works involving RMPC formulations, but an actual experimental implementation has never been reported. Particular care was taken to solve the optimization problem with linear matrix inequalities within a small sampling period (15 ms). A discussion concerning the discretization of the uncertain model is presented to justify the use of the exact zero-order hold method. More specifically, the resulting loss of polytopic structure was found to be negligible with the adopted sampling period. Three experimental scenarios were considered, with different ranges for the uncertain spring stiffness coefficient. In all cases, the control task was successfully accomplished, with proper satisfaction of constraints on the input voltage and spring deformation. },
issn = {2195-3880},
keywords = {Predictive control, Robust control, Constrained control, Linear matrix inequalities, Two-mass_spring system},
language = {English},
publisher = {Springer-Verlag}
}

This paper presents an experimental investigation concerning the use of robust model predictive control (RMPC) for a two-mass_spring system. This benchmark system has been employed as a numerical simulation example in several works involving RMPC formulations, but an actual experimental implementation has never been reported. Particular care was taken to solve the optimization problem with linear matrix inequalities within a small sampling period (15 ms). A discussion concerning the discretization of the uncertain model is presented to justify the use of the exact zero-order hold method. More specifically, the resulting loss of polytopic structure was found to be negligible with the adopted sampling period. Three experimental scenarios were considered, with different ranges for the uncertain spring stiffness coefficient. In all cases, the control task was successfully accomplished, with proper satisfaction of constraints on the input voltage and spring deformation.

@article{piazzi_2000,
title = {Minimum-Time System-Inversion-Based Motion Planning for Residual Vibration Reduction},
author = {Piazzi, A.; Visioli, A.},
journal = {IEEE/ASME Transactions on Mechatronics},
year = {2000},
volume = {5},
number = {1},
abstract = {In this paper, we present a novel approach, based on system inversion, for the point-to-point motion planning of vibratory servosystems. The idea is to define a suitable parameterized motion law of the load which assures that no oscillations occurs during and at the end of the motion; then, by means of a noncausal system inversion, the command function of the system is determined with a continuous derivative of an arbitrary order. A procedure that minimizes the duration of the movement, taking into account actuator constraints, can then be performed. Comparisons with the well-known input shaping techniques have been performed via both a simulation example and an experimental setup. The proposed method, which is inherently robust to modeling errors, emerges as a very flexible and competitive technique. },
issn = {1083-4435},
keywords = {Open-loop control, system inversion, time optimization, vibratory systems},
language = {English},
publisher = {IEEE},
pages = {22-Dec}
}

In this paper, we present a novel approach, based on system inversion, for the point-to-point motion planning of vibratory servosystems. The idea is to define a suitable parameterized motion law of the load which assures that no oscillations occurs during and at the end of the motion; then, by means of a noncausal system inversion, the command function of the system is determined with a continuous derivative of an arbitrary order. A procedure that minimizes the duration of the movement, taking into account actuator constraints, can then be performed. Comparisons with the well-known input shaping techniques have been performed via both a simulation example and an experimental setup. The proposed method, which is inherently robust to modeling errors, emerges as a very flexible and competitive technique.