Viorel Stoian

A variable structure controller for a tentacle manipulator

The paper presents a class of tentacle arms based on the use of flexible composite materials in conjunction with active-controllable electrorheological (ER) fluids. The model consists of a finite number of segments, each segment having a specific structure and control. The dynamic behaviour of the arm is obtained using Lagranges principle developed for infinite-dimensional systems. This model is represented by a set of integral-differential equations. An approximate model is then derived as a set of differential equations with variable coefficients. Two cases are discussed: the sliding mode with the bang-bang control; and the direct mode in which the controller is based on the use of the direct evolution of the system on the switching line by switching the fluid viscosity. The numerical simulations are presented. A nonlinear observer is introduced to estimate the inaccessible state variable distributed on the length of the arm. The conditions which assure the convergence to zero of the errors are proved.

A sequential distributed variable structure controller for a tentacle arm

The paper presents a new controller for a tentacle arm based on the viscosity control of the ER-fluids by an electrical field. The dynamic model of the arm is determined and an approximate model is proposed. The motion control is determined as a conventional control of the fluid pressure and as a viscosity control on the switching manifolds. The stability of the motion is proved and the conditions of the trajectory control on the switching manifolds are determined. Two viscosity control procedures are used: a lumped control and a sequential distributed control which allows the decomposition of the system in a finite number of a lower dimension problems. The numerical simulations are presented.

Using Artificial Potential Field Methods and Fuzzy Logic for Mobile Robot Control

This paper presents a new control method for mobile robots moving in its work field which is based on fuzzy logic and artificial potential field. First, the artificial potential field method is presented. The paper treats unconstrained movement based on attractive artificial potential field and after that discuss the constrained movement based on attractive and repulsive artificial potential field. A fuzzy controller is designed. Finally, some applications are presented.

A controller for hyper-redundant cooperative robots

This paper proposes a new method for multichain hyper-redundant robot models. A hyper-redundant model is a manipulator with a great flexibility-a tentacle model which can achieve any shape in space. We will discuss a system formed by hyper-redundant manipulators grasping a common object with hardpoint control. The two-level hierarchical control is adopted. The upper level coordinator gathers all the necessary information to resolve the force distribution. Then, the lower-level local control problem is treated as a open-chain redundant manipulator control problem. A closed loop control based on the inverse dynamic model and the direct sliding mode control (DSMC) procedure are proposed. The fuzzy rules are established. Simulation results are presented and discussed.

Robot Control by Fuzzy Logic

Fuzzy set theory, originally developed by Lotfi Zadeh in the 1960’s, has become a popular tool for control applications in recent years (Zadeh, 1965). Fuzzy control has been used extensively in applications such as servomotor and process control. One of its main benefits is that it can incorporate a human being’s expert knowledge about how to control a system, without that a person need to have a mathematical description of the problem. Many robots in the literature have used fuzzy logic (Song & Tay, 1992), (Khatib, 1986), (Yan et al., 1994) etc. Computer simulations by Ishikawa feature a mobile robot that navigates using a planned path and fuzzy logic. Fuzzy logic is used to keep the robot on the path, except when the danger of collision arises. In this case, a fuzzy controller for obstacle avoidance takes over. Konolige, et al. use fuzzy control in conjunction with modeling and planning techniques to provide reactive guidance of their robot. Sonar is used by robot to construct a cellular map of its environment. Sugeno developed a fuzzy control system for a model car capable of driving inside a fenced-in track. Ultrasonic sensors mounted on a pivoting frame measured the car’s orientation and distance to the fences. Fuzzy rules were used to guide the car parallel to the fence and turn corners (Sugeno et al., 1989). The most known fuzzy models in the literature are Mamdani fuzzy model and TakagiSugeno-Kang (TSK) fuzzy model. The control strategy based on Mamdani model has the linguistic expression (Mamdani, 1981):

A control system for cooperating tentacle robots

A control system is proposed to solve the local control for a multi-chain robotic system formed by tentacle manipulators grasping a common object with hard point contacts. The two-level hierarchical control is adopted. The upper level coordinator gathers all the necessary information to resolve the force distribution. The lower-level local control problem is then treated as an open-chain redundant manipulator control problem. A closed loop control based on the inverse dynamic model and the DSMC procedure are proposed. The fuzzy rules are established. Simulation results are presented and discussed.

Vehicle Steering Mechanism Elastodynamic Analysis

In this paper is performed an elasto-dynamic study of a steering mechanism from a road vehicle. Kinematical studies of the steering mechanism have been made especially on robots, their results being presented in scientific literature. The main purpose of this study is to reduce tires wear by optimizing the components of the steering mechanism.

Intelligent Live Environment Design with Assistive Robots for Vulnerable Persons

We present in this paper several ideas about the usability of the robotic arms and mobile robots as an assistive technology in a smart house where people with disabilities daily live. First, psychological and social aspects of smart home technology are presented and after that the modularity and standardization processes are discussed. Next we propose a smart house plan, equipped with a mobile robot which has a manipulator arm. This robotic system is used to help vulnerable persons, the handicapped men vehicle seat being equipped with a robotic arm which can manipulate objects by a hyper-redundant gripper. For the control of the processes in the smart house, we propose a hierarchical control system and for the mobile robot we use the artificial potential field method. Also, this paper points out the edutainment concept (EDUcation and enterTAINMENT) by robotics. Finally, some applications are presented.

Fuzzy Controllers by Unconventional Technologies for Tentacle Arms

A robust control system is proposed to solve the local control for a multi-chain robotic system formed by tentacle manipulators grasping a common object with hard point contacts. The two-level hierarchical control is adopted. The upper level coordinator gathers all the necessary information to resolve the distribution force. Then, the lower-level local control problem is treated as an open-chain redundant manipulator control problem. The stability and robustness of a class of the fuzzy logic control (FLC) are investigated and a robust FLC is proposed with uncertainties of the load. The fuzzy rules are established. Simulation results are presented and discussed.

Hyper-redundant Robot Control System in Compliant Motions

This aim of this paper is to present a hyper-redundant crawling robot movement. The authors present a new physical structure and a control algorithm for movement in narrow labyrinth spaces, by using walls touching. Collisions and contacts are part of the task. Support-points, where the robot touches the walls, are used for its movement. Subsequently, a hybrid force/position controller for hyper-redundant locomotion is presented. Ultimately, the paper presents simulations of locomotion, positioning hyper-redundant evolutions and force tracking errors. An HHR robot used for applying the algorithm is built of identical elements that are interconnected through swivel joints. The curvature of the robotic arm is created with a cable system, actuated by DC motors. The position control is established through a pneumatic system. Using actuation cables and an electro-pneumatic system for blocking the movement of desired elements, the position of the robotic arm is obtained.