727 research outputs found
Efficient and secure real-time mobile robots cooperation using visual servoing
This paper deals with the challenging problem of navigation in formation of mobiles robots fleet. For that purpose, a secure approach is used based on visual servoing to control velocities (linear and angular) of the multiple robots. To construct our system, we develop the interaction matrix which combines the moments in the image with robots velocities and we estimate the depth between each robot and the targeted object. This is done without any communication between the robots which eliminate the problem of the influence of each robot errors on the whole. For a successful visual servoing, we propose a powerful mechanism to execute safely the robots navigation, exploiting a robot accident reporting system using raspberry Pi3. In addition, in case of problem, a robot accident detection reporting system testbed is used to send an accident notification, in the form of a specifical message. Experimental results are presented using nonholonomic mobiles robots with on-board real time cameras, to show the effectiveness of the proposed method
Hamiltonian Dynamics Learning from Point Cloud Observations for Nonholonomic Mobile Robot Control
Reliable autonomous navigation requires adapting the control policy of a
mobile robot in response to dynamics changes in different operational
conditions. Hand-designed dynamics models may struggle to capture model
variations due to a limited set of parameters. Data-driven dynamics learning
approaches offer higher model capacity and better generalization but require
large amounts of state-labeled data. This paper develops an approach for
learning robot dynamics directly from point-cloud observations, removing the
need and associated errors of state estimation, while embedding Hamiltonian
structure in the dynamics model to improve data efficiency. We design an
observation-space loss that relates motion prediction from the dynamics model
with motion prediction from point-cloud registration to train a Hamiltonian
neural ordinary differential equation. The learned Hamiltonian model enables
the design of an energy-shaping model-based tracking controller for rigid-body
robots. We demonstrate dynamics learning and tracking control on a real
nonholonomic wheeled robot.Comment: 8 pages, 6 figure
Sensor-based control of nonholonomic mobile robots
The problem of tracking a moving target with a nonholonomic mobile robot, by using sensor-based control techniques, is addressed. Two control design methods, relying on the transverse function approach, are proposed. For the first method, sensory signals are used to calculate an estimate of the relative pose of the robot with respect to the target. This estimate is then used for the calculation of control laws expressed in Cartesian coordinates. An analysis of stability and robustness w.r.t. pose estimation errors is presented. The second method consists in designing the control law directly in the space of sensor signals. Both methods are simulated, with various choices of the control parameters, for a unicycle-type mobile robot equipped with a camera. Finally, experimental results are also reported
Self-Triggered Formation Control of Nonholonomic Robots
In this paper, we report the design of an aperiodic remote formation controller applied to nonholonomic robots tracking nonlinear, trajectories using an external positioning sensor network. Our main objective is to reduce wireless communication with external sensors and robots while guaranteeing formation stability. Unlike most previous work in the field of aperiodic control, we design a self-triggered controller that only updates the control signal according to the variation of a Lyapunov function, without taking the measurement error into account. The controller is responsible for scheduling measurement requests to the sensor network and for computing and sending control signals to the robots. We design two triggering mechanisms: centralized, taking into account the formation state and decentralized, considering the individual state of each unit. We present a statistical analysis of simulation results, showing that our control solution significantly reduces the need for communication in comparison with periodic implementations, while preserving the desired tracking performance. To validate the proposal, we also perform experimental tests with robots remotely controlled by a mini PC through an IEEE 802.11g wireless network, in which robots pose is detected by a set of camera sensors connected to the same wireless network
Vision based leader-follower formation control for mobile robots
Creating systems with multiple autonomous vehicles places severe demands on the design of control schemes. Robot formation control plays a vital role in coordinating robots. As the number of members in a system rise, the complexity of each member increases. There is a proportional increase in the quantity and complexity of onboard sensing, control and computation. This thesis investigates the control of a group of mobile robots consisting of a leader and several followers to maintain a desired geometric formation --Abstract, page iii
Sliding Mode Control for Trajectory Tracking of an Intelligent Wheelchair
This paper deal with a robust sliding-mode trajectory tracking controller, fornonholonomic wheeled mobile robots and its experimental evaluation by theimplementation in an intelligent wheelchair (RobChair). The proposed control structureis based on two nonlinear sliding surfaces ensuring the tracking of the three outputvariables, with respect to the nonholonomic constraint. The performances of theproposed controller for the trajectory planning problem with comfort constraint areverified through the real time acceleration provided by an inertial measurement unit
Coordinated multi-robot formation control
Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201
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