Giuseppe Fusco

A Fuzzy-Logic-Based Approach for Mobile Robot Path Tracking

One important problem in autonomous robot navigation is the effective following of an unknown path traced in the environment in compliance with the kinematic limits of the vehicle, i.e., bounded linear and angular velocities and accelerations. In this case, the motion planning must be implemented in real-time and must be robust with respect to the geometric characteristics of the unknown path, namely curvature and sharpness. To achieve good tracking capability, this paper proposes a path following approach based on a fuzzy-logic set of rules which emulates the human driving behavior. The input to the fuzzy system is represented by approximate information concerning the next bend ahead the vehicle; the corresponding output is the cruise velocity that the vehicle needs to attain in order to safely drive on the path. To validate the proposed algorithm two completely different experiments have been run: in the first experiment, the vehicle has to perform a lane-following task acquiring lane information in real-time using an onboard camera; in the second, the motion of the vehicle is obtained assigning in real-time a given time law. The obtained results show the effectiveness of the proposed method

A novel adaptive control law for underwater vehicles

This paper proposes an approach to the design of control laws for underwater vehicles that takes into account the hydrodynamic effects affecting the tracking performance. To this aim, a suitable adaptive action based on appropriate kinematic transformations between the earth-fixed frame and the vehicle-fixed frame is developed. The proposed control law adopts quaternions to represent attitude errors, thus avoiding representation singularities that occur when using instead Euler angles. The stability of the designed control law is demonstrated by means of a Lyapunov-based argument. In view of practical implementation, a simplified version of the developed control law is also proposed that compensates only the persistent hydrodynamic terms, namely, the restoring generalized forces and the ocean current. Finally, the tracking performance of the proposed control law is analyzed in comparison to that of other existing control laws available in the literature. The obtained simulation results confirm the effectiveness of the proposed technique.

A new on-line algorithm for inverse kinematics of robot manipulators ensuring path tracking capability under joint limits

The presence of joint velocity and acceleration limits must be taken into account by the inverse kinematics of robot manipulators, so as to avoid incorrect task execution when these are violated. To solve this problem, a novel algorithmic approach to kinematic control is presented in this paper, which guarantees that the joint variables do not overtake their limits. The proposed technique is based on a new second-order inverse kinematics algorithm, which enables the handling of velocity and acceleration constraints while tracking the desired end-effector path. The goal is achieved by suitably slowing down the task-space trajectory via a time warp when joints limits are encountered. The proposed method is designed for online applications, i.e., the desired trajectory is not known in advance, and requires a light computational burden. The application of the proposed approach is finally illustrated in experiments implemented on a six-degree-of-freedom industrial robot manipulator.

A novel adaptive control law for autonomous underwater vehicles

An adaptive control law for autonomous underwater vehicles (AUVs) is presented. Usually, the control laws are designed with respect to a mathematical model expressed either in the Earth-fixed frame or in the vehicle-fixed frame. These two approaches, however, do not take into account the different origin of the effects that can affect the steady state errors: namely, the restoring generalized forces and the ocean current. With the use of a suitable adaptive action those effects can be properly taken into account as is shown in the paper.

Real-time end-effector path following for robot manipulators subject to velocity, acceleration, and jerk joint limits

In this paper, an inverse kinematics algorithm for robot manipulators is developed which takes into account joint velocity, acceleration and jerk limits while ensuring tracking of the assigned end-effector path. The desired end-effector trajectory is supposed to be assigned online and the algorithm is suitable for real-time implementation on nonredundant robot arms. Numerical simulation results are reported to demonstrate the effectiveness of the proposed technique.

An odometry calibration method for mobile robots based on the least-squares technique

A method for odometry calibration of unicycle-like mobile robots is presented in this paper. The equations of motion are written so as to exploit linearity in a proper set of unknown parameters and the least-squares technique is then applied to estimate them. Experimental results show the effectiveness of the proposed technique in reducing the systematic odometric errors.

Kinematic Control of Redundant Manipulators with On-Line End-Effector Path Tracking Capability Under Velocity and Acceleration Constraints

Abstract Kinematic control techniques are based on an inverse kinematic transformation which feeds the reference values to the joints corresponding to the assigned end-effector trajectory. In this paper, a inverse kinematics algorithm for redundant robots is developed which takes into account joint velocity and acceleration limits while ensuring tracking of the assigned end-effector path. The desired end-effector trajectory is supposed to be given on-line. Numerical simulation results are reported to demonstrate the application of the proposed technique.

Experiments of fuzzy real-time path planning for unicycle-like mobile robots under kinematic constraints

This paper presents an experimental study concerning the application of a real-time motion planning algorithm to a unicycle-like mobile robot. The desired trajectory to be followed by the mobile robot in presence of bounds on the linear/angular velocities and accelerations is available online. Moreover, with the respect to the kinematic constraints, the desired path has to be kept as long as possible. The implemented algorithm is based on a discrete-time kinematic control which implements a warping of the time law based on the definition of a virtual time. In addition, a fuzzy inference system handles the additional information given by the difference between the virtual and real time in order to exploit the knowledge in advance of the desired path. The experimental results confirm the effectiveness of the adopted algorithm.

Real-time path tracking for unicycle-like mobile robots under velocity and acceleration constraints

A motion planning algorithm for unicycle-like mobile robots is presented. A desired trajectory is available in real-time to be followed by a nonholonomic mobile robot with bounds on the linear/angular velocities and accelerations. Moreover, in the respect of the kinematic constraints, the desired path has to be kept. The proposed algorithm is based on a discrete time kinematic control based on the definition of a virtual time. A fuzzy inference system is in charge of handling the additional information given by the difference between virtual and real time.

A MODULAR CONTROL LAW FOR UNDERWATER VEHICLE-MANIPULATOR SYSTEMS ADAPTING ON A MINIMUN SET OF PARAMETERS

Abstract The problem of controlling Underwater Vehicle-Manipulator Systems (UVMSs) is addressed in this paper. The serial-chain structure of such systems is exploited in order to formulate a control law based on the Virtual Decomposition approach. Each single body in the system is then controlled with a suitable adaptive control law based on a minimum number of parameters. The proposed approach results in a modular control scheme which simplifies application to multibody systems with a large number of links, reduces the required computational burden, and allows efficient implementation on distributed computing architectures. Furthermore, the occurrence of kinematic and representation singularities is overcome, respectively, by expressing the control law in body-fixed coordinates and representing the attitude via the unit quaternion. To show the effectiveness of the proposed control strategy, a full-degree-of-freedom simulation case study is developed for a vehicle in carrying a six-degrees-of-freedom manipulator.