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This paper studies the trajectory tracking control of nonholonomic wheeled mobile robots, and only measurements for Cartesian position and velocity are used. A full-order observer is proposed to estimate the unmeasurable attitude and filter the position signal. Its effectiveness relies on the persistent excitation (PE) condition of non-zero linear velocity. Using the observer states, we design a local tracking controller that guarantees: (a) the linear velocity input is positive, and (b) the position tracking error is convergent to zero locally asymptotically. Experiments performed on a robot built in-house illustrate the control algorithm. [ABSTRACT FROM AUTHOR]

In this paper we solve the problem of trajectory tracking control of an underactuated autonomous aerial vehicle in the presence of unknown time-varying dynamics. We begin our approach with the design of a Kalman filter for the linear motion subsystem under non-vanishing perturbations. The filter attenuates the noise of position measurements, and simultaneously estimates the linear velocity of the vehicle as well as an unknown term of lumped dynamics, which includes model parametric uncertainty and exogenous perturbations. The output and residual of the filter are then fed to a nonlinear controller whose thrust actuation is bounded with respect to the position and velocity errors. The total error stemming from the closed-loop system is shown to be uniformly ultimately bounded. Experimental results and comparison data are presented to showcase the performance of our strategy in different real-world applications using a quadrotor vehicle. [ABSTRACT FROM AUTHOR]

This paper addresses the attitude estimation problem of wheeled mobile robots (WMRs) with nonholonomic constraints moving in a plane. We consider the case that only the robot's Cartesian position and linear velocity are available from sensor measurements. Based on the kinematic model, three attitude observers are proposed. The first observer is designed directly on the Special Orthogonal group S O (2) and guarantees that for almost all initial conditions, the estimated attitude converges to the actual one with an exponential convergence rate. The second observer estimates the heading direction of the mobile robot, i.e. , its dynamics evolves on the unit circle S 1. The first and second observers rely on linear velocity measurements. On the other hand, the third observer presents a globally exponentially stable error dynamics and requires only Cartesian position measurements but does not evolve on S 1. Additionally, a control-observer algorithm is proposed to solve the trajectory-tracking problem of WMRs. Finally, the performances of the proposed attitude observers and control law were evaluated by a set of experiments on a commercial WMR. [ABSTRACT FROM AUTHOR]

This paper investigates the circular formation control problem of multiple nonholonomic vehicles of unicycle type. The measurement of each vehicle is based on its local coordinate frame and the communication network among vehicles is modeled by a directed cycle graph. A distributed dynamic control law is designed by only using the local measurement of each vehicle and information of its neighbors in the network. The proposed control law guarantees that all vehicles move with a prespecified angular velocity along a common circle with the given center and radius, and maintain evenly spaced along the circle. Furthermore, the velocity constraint including positive-minimum linear velocity of each vehicle is explicitly taken into account. [ABSTRACT FROM AUTHOR]

An advanced nonlinear observer for rigid bodies evolving in 3D-space relying on measurement data provided by an IMU and linear velocity measured in the body-fixed frame has been recently proposed, but without specifying its domain of convergence and stability. With respect to conventional attitude observers, which do not involve linear velocity measurements, this observer is better adapted for vehicles subjected to sustained accelerations. This paper presents further modifications yielding two velocity-aided attitude observers, with rigorous almost global convergence and stability analysis. Moreover, the estimation of the gravity direction is globally decoupled from magnetometer measurements. [ABSTRACT FROM AUTHOR]

This paper addresses the image-based control problem of vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs). Specifically, we propose a control scheme allowing the aircraft to track a moving target captured by an onboard camera where the orientation and angular velocity of the vehicle are assumed available for feedback. The proposed approach relies on appropriate image features, defined based on perspective image moments along with a useful projection, and the design of a bounded adaptive translational controller without linear velocity measurements in the presence of external disturbances. Estimates of the target’s acceleration and the disturbances as well as some auxiliary variables are used to simplify the control design and guarantee the stability of the overall closed loop system. Simulation examples are provided to show the effectiveness of the proposed theoretical results. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of full state estimation for vehicles navigating in a three dimensional space. We assume that the vehicle is equipped with an Inertial Measurement Unit (IMU) providing body-frame measurements of the angular velocity, the specific force, and the Earth's magnetic field. Moreover, we consider available sensors that provide partial or full information about the position of the vehicle. Examples of such sensors are those which provide full position measurements (e.g., GPS), range measurements (e.g., Ultra-Wide Band (UWB) sensors), inertial-frame bearing measurements (e.g., motion capture cameras), or altitude measurements (altimeter). We propose a generic semi-globally exponentially stable nonlinear observer that estimates the position, linear velocity, linear acceleration, and attitude of the vehicle, as well as the gyro bias. We also provide a detailed observability analysis for different types of measurements. Simulation and experimental results are provided to demonstrate the effectiveness of the proposed estimation scheme. [ABSTRACT FROM AUTHOR]

This paper considers the problem of simultaneous estimation of the attitude, position and linear velocity for vehicles navigating in a three-dimensional space. We propose two types of hybrid nonlinear observers using continuous angular velocity and linear acceleration measurements as well as intermittent landmark position measurements. The first type relies on a fixed-gain design approach based on an infinite-dimensional optimization, while the second one relies on a variable-gain design approach based on a continuous–discrete Riccati equation. For each case, we provide two different observers with and without the estimation of the gravity vector. The proposed observers are shown to be exponentially stable with a large domain of attraction. Simulation and experimental results are presented to illustrate the performance of the proposed observers. [ABSTRACT FROM AUTHOR]