Decebal Popescu

A Variable Length Tentacle Manipulator Control System

The control problem of a class of tentacle arm, with variable length, that can achieve any position and orientation in 3D space and can increase the length in order to get a better control in the constraint operator space is presented. First, the dynamic model of the system is inferred. In order to avoid the difficulties generated by the complexity of the nonlinear integral - differential model, the control problem is based on the artificial potential method. Then, the method is used for constrained motion in an environment with obstacles. Numerical simulations for spatial and planar tentacle models are presented in order to illustrate the efficiency of the method.

Frequency criteria for the grasping control of a hyper-redundant robot

The paper focuses on hyper-redundant arms with continuum elements that perform the grasping function by coiling. First, there is concern with the dynamic model of the continuum arm for the position control during non-contact operations with the environment. A frequency stability criterion based on the Kahman - Yakubovich - Popov Lemma and P and PD control algorithms is proposed. Then, the grasping control of the arm in contact with a load is analyzed. The dynamics of the system are discussed and an extension of the Popov criterion is endorsed. The control algorithms based on SMA actuators are introduced. Numerical simulations and experimental results of the arm motion toward an imposed target are presented.

Position and force control of the grasping function for a hyperredundant arm

The grasping control problem for a hyperredundant manipulator is presented. The dynamic model is derived by using Lagrange equations developed for infinite dimensional systems. The algorithms for the position and force control are proposed. The arm fluid pressure control is inferred and the conditions that ensure the stability of the motion are discussed. Numerical simulations are presented.

Force observer-based control for a rehabilitation hand exoskeleton system

This paper is a component of a research project regarding the design and development of an Intelligent Haptic Robot-Glove for the rehabilitation of the patients that have a diagnosis of a cerebrovascular accident. In this paper, the control system for a rehabilitation hand exoskeleton is discussed. In order to avoid the complex problems given by a distributed sensor network, this paper treats the problem of the compliance force control by using observers: a velocity observer, a force observer and a disturbance observer. Two control solutions are discussed. First, the disturbance effects are eliminated by a cascade closed loop control with velocity and force observers. Then, a disturbance observer is used to compensate the compliance effects. The performance of the control systems is demonstrated by the simulation.

Modelling and control of wind turbines

Abstract As the world is currently facing an energy and climate crisis, the development and utilization of alternative sources of energy has become an important challenge. From all types of renewable energy sources, wind turbines proved to be one of the cleanest and most reliable solutions for energy production. Wind energy conversion systems have in the last decades been subject of a strong interest as they could offer a viable source of electrical energy. This is why, it is important to focus on complex algorithms that meet with multiple objectives such as speed regulation, blade load and mode stabilization with simultaneously maximizing energy capture. This paper starts with a state of the art of wind turbines and their problematic and continues with the presentation of a polynomial control method designed for the third functioning zone of a wind turbine.

Robust control for wind power systems

This paper presents an RST controller design applied to a horizontal wind turbine, functioning in the above rated wind speeds area. The controller presented here, is a robust digital controller which aims to regulate the wind turbine rotor speed through collective blade pitch control. The paper starts with a state of the art of wind turbines and their problematic and continues with the design of the controller. The robustness of the controller will be shown through the robustness indicators values and also will be tested through the variation of the models parameters. This control method provided a good response by eliminating the steady state error after a step input and has shown good robustness indicator values.

A decoupled sliding mode control for a continuum arm

The paper treats the control problem of a class of robots constituted by a chain of continuum segments. The technological model basis is a central, long and thin, highly flexible and elastic backbone. The segment control system is a decoupled one. The main parameters of the arm control are determined by the curvature and curvature gradient. The dynamic model is inferred. The primary benefit of the proposed method is that the dynamic equations are represented by a set of ODE’s in time instead of PDE’s in time and space, and the new curvature gradient lumped parameter model is used. A sliding mode control system is used in order to achieve the desired shape of the arm. The stability of the closed-loop control system is proven. Numerical simulations and an experimental platform are also provided to verify the effectiveness of the presented approach.

A Spatial Weight Error Control for a Class of Hyper-Redundant Robots

This paper treats the control problem of a class of hyper-redundant robots. The dynamic model of the arm is described by hyperbolic partial differential equations with uncertain components. By using a spatial weighted error control, the infinite dimensional system control becomes a finite-dimensional control problem. The stability analysis and the resulting controllers are obtained using the concept of boundary geometric control and a spatial weighted error control technique. A robust algorithm that is based on weighted error sliding mode control is discussed. The boundary tendon control determines the system evolution toward a prescribed switching surface, and in order to avoid the oscillations around the switching surface, a damping control determines a direct evolution, along the switching surface, toward the origin. Numerical simulations and experimental results are also provided to verify the effectiveness of the presented approach.

Coil function control problem for a hyperredundant robot

The paper focuses on the control problem of a hyperredundant robot that performs the coil function of grasping. First, the dynamic model of a hyperredundant arm with continuum elements produced by flexible composite materials in conjunction with active-controllable electro-rheological fluids is analyzed. Secondly, both problems, i.e. the position control and the force control are approached. The difficulties determined by the complexity of the non-linear integral-differential equations are avoided by using a basic energy relationship of this system. Energy-based control laws are introduced for the position control problem. A force control method is proposed, namely the DSMC method in which the evolution of the system on the switching line by the ER fluid viscosity is controlled. Numerical simulations are also presented.

Exoskeleton Design of an Intelligent Haptic Robotic Glove

This paper is based on the results of a research project regarding the design and development of an Intelligent Haptic Robot-Glove (IHRG) for the rehabilitation of the patients that have a diagnosis of a cerebrovascular accident. The IHRG is an exoskeleton that supports the human hand and hand activities by using a control architecture for dexterous grasping and manipulation. The five-fingered assistive robotic glove is designed with mechanical compliance of human finger. The biomechanical elements of the exoskeleton assistive hand are designed considering: motion in different planes, adapted to patients hand, possible to train pinch and grasp, opening/closing game. The actuation system is also studied and designed. The paper provides an overview of hand rehabilitation and evaluation techniques.