208 research outputs found
Multirobot heterogeneous control considering secondary objectives
Cooperative robotics has considered tasks that are executed frequently, maintaining the
shape and orientation of robotic systems when they fulfill a common objective, without taking
advantage of the redundancy that the robotic group could present. This paper presents a proposal
for controlling a group of terrestrial robots with heterogeneous characteristics, considering primary
and secondary tasks thus that the group complies with the following of a path while modifying its
shape and orientation at any time. The development of the proposal is achieved through the use
of controllers based on linear algebra, propounding a low computational cost and high scalability
algorithm. Likewise, the stability of the controller is analyzed to know the required features that have
to be met by the control constants, that is, the correct values. Finally, experimental results are shown
with di erent configurations and heterogeneous robots, where the graphics corroborate the expected
operation of the proposalThis research was funded by Corporación Ecuatoriana para el Desarrollo de la Investigación
y Academia–CEDI
Mobile Formation Coordination and Tracking Control for Multiple Non-holonomic Vehicles
This paper addresses forward motion control for trajectory tracking and
mobile formation coordination for a group of non-holonomic vehicles on SE(2).
Firstly, by constructing an intermediate attitude variable which involves
vehicles' position information and desired attitude, the translational and
rotational control inputs are designed in two stages to solve the trajectory
tracking problem. Secondly, the coordination relationships of relative
positions and headings are explored thoroughly for a group of non-holonomic
vehicles to maintain a mobile formation with rigid body motion constraints. We
prove that, except for the cases of parallel formation and translational
straight line formation, a mobile formation with strict rigid-body motion can
be achieved if and only if the ratios of linear speed to angular speed for each
individual vehicle are constants. Motion properties for mobile formation with
weak rigid-body motion are also demonstrated. Thereafter, based on the proposed
trajectory tracking approach, a distributed mobile formation control law is
designed under a directed tree graph. The performance of the proposed
controllers is validated by both numerical simulations and experiments
Formation control of nonholonomic mobile robots: the virtual structure approach
PhDIn recent years, there has been a considerable growth in applications of
multi-robot systems as opposed to single-robot systems. This thesis
presents our proposed solutions to a formation control problem in
which mobile robots are required to create a desired formation shape
and track a desired trajectory as a whole.
In the first instance, we study the formation control problem for unicycle
mobile robots. We propose two control algorithms based on a
cascaded approach: one based on a kinematic model of a robot and
the other based on a dynamic model. We also propose a saturated
controller in which actuator limitations are explicitly accounted for.
To demonstrate how the control algorithms work, we present an extensive
simulation and experimental study.
Thereafter we move on to formation control algorithms in which the
coordination error is explicitly defined. Thus, we are able to give conditions
for robots keeping their desired formation shape without necessarily
tracking the desired trajectory. We also introduce a controller
in which both trajectory tracking and formation shape maintenance
are achieved as well as a saturated algorithm. We validate the applicability
of the introduced controllers in simulations and experiments.
Lastly, we study the formation control problem for car-like robots. In
this case we develop a controller using the backstepping technique.
We give conditions for robots keeping their desired formation shape
while failing to track their desired trajectories and present simulation
results to demonstrate the applicability of the proposed controlle
Controlling rigid formations of mobile agents under inconsistent measurements
Despite the great success of using gradient-based controllers to stabilize
rigid formations of autonomous agents in the past years, surprising yet
intriguing undesirable collective motions have been reported recently when
inconsistent measurements are used in the agents' local controllers. To make
the existing gradient control robust against such measurement inconsistency, we
exploit local estimators following the well known internal model principle for
robust output regulation control. The new estimator-based gradient control is
still distributed in nature and can be constructed systematically even when the
number of agents in a rigid formation grows. We prove rigorously that the
proposed control is able to guarantee exponential convergence and then
demonstrate through robotic experiments and computer simulations that the
reported inconsistency-induced orbits of collective movements are effectively
eliminated.Comment: 10 page
Distributed formation tracking control of multiple car-like robots
In this thesis, distributed formation tracking control of multiple car-like robots is studied. Each vehicle can communicate and send or receive states information to or from a portion of other vehicles. The communication topology is characterized by a graph. Each vehicle is considered as a vertex in the graph and each communication link is considered as an edge in the graph. The unicycles are modeled firstly by both kinematic systems. Distributed controllers for vehicle kinematics are designed with the aid of graph theory. Two control algorithms are designed based on the chained-form system and its transformation respectively. Both algorithms achieve exponential convergence to the desired reference states. Then vehicle dynamics is considered and dynamic controllers are designed with the aid of two types of kinematic-based controllers proposed in the first section. Finally, a special case of switching graph is addressed considering the probability of vehicle disability and links breakage
Leader-Follower Control with Odometry Error Analysis
In this paper we present a leader-follower control law that enables a mobile robot to track a desired trajectory, and allows us to specify the position in the plane of the follower robot with respect to the leader robot. We first describe the dynamic model of the plant, including input torques, and friction forces. Then the control law is developed using backstepping, and it is proved to asymptotically stabilize the tracking error to the origin. Simulation and experimental results of the closed loop system are presented, highlighting its potential application to formation control. The special case of pure tracking (without bi-dimensional position information use) is analyzed, showing that it can be applied to particular classes of non-feasible trajectories. Finally, motivated by some observations on the experiments, the effects of odometry errors are analyzed, revealing that boundedness of the tracking errors can be guaranteed if absolute position information becomes available periodically
Autonomous Behaviors With A Legged Robot
Over the last ten years, technological advancements in sensory, motor, and computational capabilities have made it a real possibility for a legged robotic platform to traverse a diverse set of terrains and execute a variety of tasks on its own, with little to no outside intervention. However, there are still several technical challenges to be addressed in order to reach complete autonomy, where such a platform operates as an independent entity that communicates and cooperates with other intelligent systems, including humans. A central limitation for reaching this ultimate goal is modeling the world in which the robot is operating, the tasks it needs to execute, the sensors it is equipped with, and its level of mobility, all in a unified setting. This thesis presents a simple approach resulting in control strategies that are backed by a suite of formal correctness guarantees. We showcase the virtues of this approach via implementation of two behaviors on a legged mobile platform, autonomous natural terrain ascent and indoor multi-flight stairwell ascent, where we report on an extensive set of experiments demonstrating their empirical success. Lastly, we explore how to deal with violations to these models, specifically the robot\u27s environment, where we present two possible extensions with potential performance improvements under such conditions
Heterogeneous robots: Model Predictive Control for bearing-only formation and tracking
openMulti-agent systems are systems composed by more than one autonomous robots which usually work under the assumption that they can communicate sending and receiving positions of other robots that operate in the network.
The introduction of this kind of systems is due to the fact that in many situations it is preferable to use more than one robot in order to reach more complex goal without the help of the humans, especially in dangerous situations.
In this thesis, the focus is on the heterogeneous robots which are robots whose components are heterogeneous in terms of actuation capabilities, even if it is assumed they can receive bearing information with respect to the other agents in the network.
Hence, it is developed an heterogeneous MAS composed by 2 UGVs and 2 UAVs.
The goals of the thesis is that the formation has to be maintained and the four agents has also to track a desired trajectory through a leader follower approach based on bearing-only implemented using MPC controllers.
The role of the leader is to track the desired trajectory while the followers have to form and maintain the formation also during the tracking.
The followers do not know the trajectory to be tracked, nor the distance to the other agents and the leader. The approach is based on decentralized leader follower control with bearing-only.
The controllers used are the Model Predictive ones since this type of control allow to prevent the critical situations, solving an online optimization problem at each time instant to select the best control action that drives the predicted output to the reference.
The proposed approach is implemented in Matlab and Simulink and the results obtained by the simulations will be discussed.Multi-agent systems are systems composed by more than one autonomous robots which usually work under the assumption that they can communicate sending and receiving positions of other robots that operate in the network.
The introduction of this kind of systems is due to the fact that in many situations it is preferable to use more than one robot in order to reach more complex goal without the help of the humans, especially in dangerous situations.
In this thesis, the focus is on the heterogeneous robots which are robots whose components are heterogeneous in terms of actuation capabilities, even if it is assumed they can receive bearing information with respect to the other agents in the network.
Hence, it is developed an heterogeneous MAS composed by 2 UGVs and 2 UAVs.
The goals of the thesis is that the formation has to be maintained and the four agents has also to track a desired trajectory through a leader follower approach based on bearing-only implemented using MPC controllers.
The role of the leader is to track the desired trajectory while the followers have to form and maintain the formation also during the tracking.
The followers do not know the trajectory to be tracked, nor the distance to the other agents and the leader. The approach is based on decentralized leader follower control with bearing-only.
The controllers used are the Model Predictive ones since this type of control allow to prevent the critical situations, solving an online optimization problem at each time instant to select the best control action that drives the predicted output to the reference.
The proposed approach is implemented in Matlab and Simulink and the results obtained by the simulations will be discussed
- …