Annemarie M. Kökösy

A novel higher order sliding mode control scheme

A higher order sliding mode control algorithm is proposed for a class of uncertain multi-input multi-output nonlinear systems. This problem can be viewed as the flnite time stabilization of a higher order input-output dynamic system with bounded uncertainties. The developed control scheme is based on geometric homogeneity and sliding mode control. The proposed procedure provides explicit conditions on the controller parameters and guarantees robustness against uncertainties. An illustrative example of a hovercraft vessel control demonstrates the advantages of the strategy.

Motion planning for cooperative unicycle-type mobile robots with limited sensing ranges: A distributed receding horizon approach

This paper presents a decentralized motion planner for a team of nonholonomic mobile robots subject to constraints imposed by sensors and the communication network. The motion planning scheme consists of decentralized receding horizon planners that reside on each vehicle to achieve coordination among flocking agents. The advantage of the proposed algorithm is that each vehicle only requires local knowledge of its neighboring vehicles. The main requirement for designing an optimal conflict-free trajectory in a decentralized way is that each robot does not deviate too far from its presumed trajectory designed without taking the coupling constraints into account. A comparative study between the proposed algorithm and other existing algorithms is provided in order to show the advantages, especially in terms of computing time. Finally, experiments are performed on a team of three mobile robots to demonstrate the validity of the proposed approach.

Autonomous navigation of a nonholonomic mobile robot in a complex environment

This paper presents a new path planning algorithm for the autonomous navigation of a nonholonomic mobile robot. The environment in which the robot evolves is unknown and encumbered by obstacles. The goal of the robot is to move towards the arrival point (which is known) by avoiding the obstacles. The path planning algorithm recomputes a new trajectory whenever a new obstacle is detected. The planned trajectory takes account of the physical constraints of the robot (speed saturation, kinematic robot model, nonholonomic constraint). The trajectory of the robot is obtained by optimizing a problem of optimal control under constraints. The resolution of this problem is done by using the flatness property of the system, which transforms the initial optimization problem into a nonlinear dynamic programming problem. The problems of the local minima are solved by using a supervisor. Our algorithm will be compared with another algorithm of the literature in order to highlight its effectiveness. Simulation results will be presented to illustrate the good performance of the algorithm for robot navigation in a complex environment.

Practical stabilization and tracking of a wheeled mobile robot with integral sliding mode controller

This paper is dedicated to the robust stabilization and tracking problems for a wheeled mobile robot. After the mobile robot dynamics have been transformed into an advantageous form, a robust integral sliding mode controller is designed to promulgate a practical stabilization in spite of the uncertainties. The performance of the proposed controller is experimentally demonstrated on a real robot.

Experimental Motion Planning and Control for an Autonomous Nonholonomic Mobile Robot

This paper presents an architecture for the navigation of an autonomous mobile robot evolving in an uncertain environment with obstacles. The proposed strategy consists in separating the path planning from the control algorithm. The path planning is done by computing the time optimal collision-free trajectory which takes into account the limitations on the linear and angular speeds of the vehicle. The position and shape of obstacles are computed by a vision algorithm using a single camera. A saturated controller based on integral sliding mode is designed to solve the tracking problem in the presence of input saturations and of the unknown disturbances. The effectiveness, perfect performance of obstacle avoidance, real-time and high robustness properties are demonstrated by experimental results.

A single landmark based localization algorithm for non-holonomic mobile robots

This paper proposes a single landmark based localization algorithm for non-holonomic mobile robots. In the case of a unicycle robot model, the localization problem is equivalent to the system observability. Based on this observation, the proposed localization method consists in finding a vector function which depends on the measurement vector and its derivatives. In order to compute estimates of the successive derivatives of the measurement vector, we will use a numerical differentiation method. When the robot is able to only measure the relative angle between itself and the landmark in 2D case, the algorithm estimates the posture of the robot, under the hypothesis that control inputs are known. But, sometimes it is also useful to be able to estimate the control input (for example when the robot slips). This is possible with the proposed algorithm by using a landmark in dimension three. The simulation results will be given in order to show the effectiveness of the proposed algorithm. Moreover, these results are compared with those obtained by an Extended Kalman Filter in order to underline the advantages of the new algorithm.

Localizability of unicycle mobiles robots: An algebraic point of view

A single landmark based localization algorithm for unicycle mobile robots was provided in [1]. It is based on the algebraic localizability notion and an efficient differentiation algorithm in noisy environment ([2], [3]). Let us stress that this localization algorithm do not need to know the linear and the angular velocities which are reconstructed by this algorithm using the kinematic model. In this paper, a sensibility study leads to a new fusion algorithm in the multi landmark case using as a basis our posture differentiation based estimator. Some simulations and experimental results are presented in order to prove the effectiveness of the proposed method compared to the well known EKF method.

A professional project based learning method in mobile robotics

Due to its high potential and encouraging results, project-based learning emerges as a highly interesting paradigm in the education systems worldwide. Moreover, robotics is an interdisciplinary field where students could learn and apply their skills in mechanics, electronics, computer science, mathematics and control engineering. This paper presents a robotics project-based learning methodology which focuses on collaborating with the industry to design, develop, evaluate, integrate and manage projects designated to be used in real-life applications. This learning method emphasizes and enables the students to apprehend the importance of fulfilling client requirements and the interactions with the client, the suppliers and with the other members of the team. The students, coached by a partner from industry, have the opportunity to apply and to improve their project management skills under a large-scale, highly complex project. This method is being applied since 2008 at ISEN Lille, France, with good results and significant impact.

Decentralized robust control for multi-vehicle navigation

This paper presents a decentralized architecture for the navigation of a formation of autonomous mobile robots evolving in an uncertain environment with obstacles. The motion planning scheme consists in decentralized receding horizon controllers that reside on each vehicle to achieve coordination among formation agents. The advantage of the proposed algorithm is that each vehicle only requires local knowledge of its neighboring vehicles. The main requirement for designing a conflict free trajectory that satisfy the coupling constraints, in a decentralized way, is that each robot do not deviate too far from its assumed trajectory designed without taking into account the coupling constraints. Having established an open loop control strategy for motion planning, an effective saturated closed-loop controller based on integral sliding mode for trajectory tracking is presented. Finally, some simulation results demonstrate the effectiveness, real-time and high robustness properties of the proposed architecture.

Design of an Arduino based low-cost error generator for PROFIBUS DP

This paper briefly discusses the design of a low-cost, versatile and configurable error generator for PROFIBUS DP. Using a PROFICORE ULTRA oscilloscope trigger pulse, a small circuit designed around an Arduino MEGA 2560 disrupts messages on the industrial network, without adding an extra slave.