The automatic landmark identification is very important in autonomous robotnavigation tasks. In this paper, we use a monocular omnidirectional visionsystem to extract the image features and the conformal geometric algebra tocompute the projective invariants from such features. We show how these featurescan be used to compute projective and permutationp2-invariants from any kind ofomnidirectional vision system. Thep2-invariants represent scenesublandmarks, and a set of them characterize a landmark. The advantage of thisrepresentation is that the landmarks are more robust than the singlecross-ratio.

This paper presents a performance comparison of different estimation and prediction techniques applied to the problem of tracking multiple robots. The main performance criteria are the magnitude of the estimation or prediction error, the computational effort and the robustness of each method to non-Gaussian noise. Among the different techniques compared are the well-known Kalman filters and their different variants (e.g. extended and unscented), and the more recent techniques relying on Sequential Monte Carlo Sampling methods, such as particle filters and Gaussian Mixture Sigma Point Particle Filter.

This research presents a comprehensive and useful survey of the kinematic models of wheeled mobile robots and their optimal configurations. The kinematic modeling of wheeled mobile robots with no-slip is presented, by considering four common types of wheels: fixed, orientable, castor, and Swedish. Next, the accuracy of the kinematic models is discussed considering their sensitivity or relative error amplification, giving rise to the isotropy concept. As practical application of the previous theory, all types of three-wheeled mobile robots are modeled and their optimal (isotropic) configurations for no error amplification are obtained. Finally, three practical examples of error amplification are developed for several types of wheeled mobile robots in order to illustrate the benefits and limitations of the isotropic configurations.

This paper presents simulation results for basic operation of CALUMA (CAssino Low-cost hUMAnoid robot). The new humanoid robot CALUMA is described with its characteristics of low-cost design and easy-operation behavior. A CALUMA model in ADAMS environment has been elaborated. The CALUMA ADAMS model has been used for a dynamic simulation of robot operation. Three modes for the dynamic simulation have been studied, namely straight walking, walking with a grasped object in the hand, and lifting an object. The results of simulating those basic operations show the feasibility of the proposed design for CALUMA robot and validate its operation. Improvements have been illustrated in the design evolution for the robot structure and operation as suggested by simulation results.

Developing 6-DOF isotropic manipulators using isotropic generators is simple and efficient, and isotropic generators can be employed to develop serial, redundant, or parallel isotropic manipulators. An isotropic generator consists of a reference point and six straight lines. The existing generators, however, have one common geometric constraint: the reference point is equidistant from the six straight lines. Some practical isotropic designs might not be obtained due to this constraint. This paper proposes methods for developing new isotropic generators. The generators thus developed are not subject to the constraint, and the new methods allow us to specify the location of the tool center point, the size of the platform or the base, or the shape of isotropic parallel manipulators. Many new generators are presented to develop 6-DOF parallel manipulators with different shapes or different types of kinematic chains.

A system including Global Positioning Systems (GPS) and digital cartography is a good solution to carry out vehicle's guidance. However, it has inconveniences like high sensibility to multipath and interference when the GPS signal is blocked by external agents. Another system is mandatory to avoid this error. This paper presents a cooperative system based on GPS and Inertial Navigation Systems (INS) for automated vehicle position. The control system includes a decision unit to choose which value is the correct. In case GPS is working at top precision, it takes the control. On the other part, GPS signal can be lost and inertial control system guides the car in this occasion. A third possibility is contemplated: we receive the signal from GPS but the accuracy is over one meter. Now, position value is obtained by means of both systems. Experimental results analyze two situations: guidance in an urban area where GPS signal can be occluded by buildings or trees during short time intervals and the possibility of loss of the signal in long time to simulate the circulation in tunnels. Good results have been observed in tests and it demonstrates how a cooperative system improves the automated vehicle guidance.

In this paper, dead-reckoning localization errors for automated guided vehicles (AGVs) in indoors quasi-structured environments are studied. Based on error ellipse localization analysis, dead-reckoning errors arising from mismatched AGV wheels radius are investigated. The dynamic model for a differential-drive AGV type with mismatched wheels radius is also derived. The developed rationale shows that sensor fusion is a key feature for minimizing AGV localization errors. Two simulation scenarios and one experiment are presented to show system performance under AGV proportional-derivative (PD)-type control.

A humanoid robot should be able to keep balance even in the presence of disturbing forces. Studies of human body reaction patterns to sudden external forces (impacts) are useful for developing balance control strategies. In this paper, we show how to implement two such reaction patterns, called ankle and hip strategy, using a small humanoid robot. Simple dynamical models in the sagittal plane are employed. The decision for invoking one of the reaction patterns is based on acceleration data measured during the impact. The experiments confirm that the robot is able to react swiftly, similar to a human.

This paper addresses the dynamic simulation and control of structural vibrations of a 3-PRR parallel manipulator with three flexible intermediate links, to which are bonded lead zirconate titanate (PZT) actuators and sensors. Flexible intermediate links are modelled as Euler–Bernoulli beams with pinned-pinned boundary conditions. A PZT actuator controller is designed based on strain rate feedback (SRF) control. Control moments from PZT actuators are transformed to force vectors in modal space and are incorporated in the dynamic model of the manipulator. The dynamic equations are developed based on the assumed mode method for the flexible parallel manipulator with multiple PZT actuator and sensor patches. Numerical simulation is performed and the results indicate that the proposed active vibration control strategy is effective. Spectral analyses of structural vibrations further illustrate that deformations from structural vibration of flexible links are suppressed to a significant extent when the proposed vibration control strategy is employed, while the deflections caused by inertial and coupling forces are not reduced.

This paper addresses the problem of contact force control for multiple contacts distributed over multiple links in a robot. This is of importance when performing complex tasks in unstructured environment, particularly in humanoid robot applications. The proposed multicontact control framework provides a new way of defining the operational space coordinates, which facilitates the specification of multiple contact control. The contact force space on multiple links is constructed as an operational space for the highest priority task. Motion control, given lower priority, can be executed using the rest of degree of freedom within the null-space of the force control. The dynamic control structure, then, provides a means to control each contact force and motion independently. This dynamic decoupling enables each contact force controller to utilize linear control theories. In particular, the contact force controllers adopt full state feedback control and estimation methods to produce robust performance with respect to modeling and parameter uncertainties. The effectiveness of the multiple contact control framework was demonstrated using a PUMA560 manipulator, with multiple contacts on the end-effector and third link. The demonstrated tasks involved controlling each of the contact forces with null-space motion.

The issue of motion planning for closed-loop mechanisms, such as parallel manipulators or robots, is still an open question. This paper proposes a novel approach for motion planning of spatial parallel robots. The framework for the geometric modeling is based on the visibility graph methodology. It is opted for a multiple-heuristics approach, where different influences are integrated in a multiplicative way within the heuristic cost function. Since the issue of singularities is a fundamental one for parallel robots, it is emphasized on the avoidance of such configurations. To include singularity-free planning within the heuristic approach, two heuristic functions are proposed, the inverse local dexterity as well as a novel defined “next-singularity” function, in such a way, well conditioned motions can be provided by a single planning procedure. The success of the method is illustrated by some examples.

We address the synthesis of controllers for a swarm of robots to generate a desired two-dimensional geometric pattern specified by a simple closed planar curve with local interactions for avoiding collisions or maintaining specified relative distance constraints. The controllers are decentralized in the sense that the robots do not need to exchange or know each other's state information. Instead, we assume that the robots have sensors allowing them to obtain information about relative positions of neighbors within a known range. We establish stability and convergence properties of the controllers for a certain class of simple closed curves. We illustrate our approach through simulations and consider extensions to more general planar curves.