In this paper, we present the work related to the application of a visual odometry approach to estimate the location of mobile robots operating in off-road conditions. The visual odometry approach is based on template matching, which deals with estimating the robot displacement through a matching process between two consecutive images. Standard visual odometry has been improved using visual compass method for orientation estimation. For this purpose, two consumer-grade monocular cameras have been employed. One camera is pointing at the ground under the robot, and the other is looking at the surrounding environment. Comparisons with popular localization approaches, through physical experiments in off-road conditions, have shown the satisfactory behavior of the proposed strategy.

In this work, a vision-based control interface for commanding a robotic wheelchair is presented. The interface estimates the orientation angles of the user's head and it translates these parameters in command of maneuvers for different devices. The performance of the proposed interface is evaluated both in static experiments as well as when it is applied in commanding the robotic wheelchair. The interface calculates the orientation angles and it translates the parameters as the reference inputs to the robotic wheelchair. Control architecture based on the dynamic model of the wheelchair is implemented in order to achieve safety navigation. Experimental results of the interface performance and the wheelchair navigation are presented.

The aim of this work has been the implementation and testing in real conditions of a new algorithm based on the cell-mapping techniques and reinforcement learning methods to obtain the optimal motion planning of a vehicle considering kinematics, dynamics and obstacle constraints. The algorithm is an extension of the control adjoining cell mapping technique for learning the dynamics of the vehicle instead of using its analytical state equations. It uses a transformation of cell-to-cell mapping in order to reduce the time spent during the learning stage. Real experimental results are reported to show the satisfactory performance of the algorithm.

We present a new numerical optimal design for a redundant parallel manipulator, the eclipse, which has a geometrically symmetric workspace shape. We simultaneously consider the structural mass and design efficiency as objective functions to maximize the mass reduction and minimize the loss of design efficiency. The task-oriented workspace (TOW) and its partial workspace (PW) are considered in efficiently obtaining an optimal design by excluding useless orientations of the end-effector and by including just one cross-sectional area of the TOW. The proposed numerical procedure is composed of coarse and fine search steps. In the coarse search step, we find the feasible parameter regions (FPR) in which the set of parameters only satisfy the marginal constraints. In the fine search step, we consider the multiobjective function in the FPR to find the optimal set of parameters. In this step, fine search will be kept until it reaches the optimal set of parameters that minimize the proposed objective functions by continuously updating the PW in every iteration. By applying the proposed approach to an eclipse-rapid prototyping machine, the structural mass of the machine can be reduced by 8.79% while the design efficiency is increased by 6.2%. This can be physically interpreted as a mass reduction of 49 kg (the initial structural mass was 554.7 kg) and a loss of 496 mm3/mm in the workspace volume per unit length. The proposed optimal design procedure could be applied to other serial or parallel mechanism platforms that have geometrically symmetric workspace shapes.

An observation approach is proposed for determining the poses of the active/constrained wrench and the unified statics of some limited-DOF parallel manipulators (PMs) are studied systematically. First, a general PM model is constructed, and the unified inverse displacement is analyzed. Second, various types of acceptable legs are synthesized; the poses of the active/constrained wrench exerted on the various acceptable legs are determined by the observation approach. Third, a unified 6 × 6 Jacobina matrix and a unified statics equation are derived for solving active/constrained wrench of many limited-DOF PMs. Finally, two PMs are presented to illustrate this approach.

The motivation for this work is the state of modern structural mechanisms that are characterized by growing complexity and ever-increasing demands for rapid and accurate motion. These contradictory requirements are often achieved according to easier and easier structures characterized by flexibility segments. In most of cases, the elasticity of structures appears as an obstacle for a precise and rapid control of motion. The aim of this paper is to explore ways of implementation of structural properties of elasticity with the application of high fidelity models during synthesis and analysis of complex mechanisms. Precisely, the aim is to explore the possibility of using Euler–Bernoulli equation, if not in its original form, then to the same extent with the use of modern knowledge in robotics (based on the knowledge of classical mechanics), and to examine the affordability and confirmation of the method through simulation results for a typical robotic configuration.

Professor Miomir Vukobratović passed away on March 11, 2012 at the age of 81. However, his achievements in robotics will remain with us always.

Miomir Vukobratović was born in 1931. He graduated in 1957 from the Faculty of Mechanical Engineering, University of Belgrade, where he also obtained his first PhD in 1964. In January 1958 he joined the Aeronautical Institute in Belgrade. At the beginning of 1965 he moved to the Mihajlo Pupin Institute in Belgrade, where he became director of the Robotics Laboratory. In 1980, he became professor at the Production Engineering Department of the Faculty of Mechanical Engineering, University of Belgrade.

As every real mechanical hand has a limited accuracy, the grasp planning process must be prepared to cope with unavoidable positioning errors. The concept of independent contact regions (ICRs) was proposed to deal with this issue by computing for each finger an ICR on the object's boundary such that each finger can be placed anywhere in its ICR to guarantee a force closure grasp. Existing methods for computing ICRs of a polygon requires that each ICR must lie on a single edge of the polygon. This constraint severely limits the size of computed ICRs, especially when the input polygon contains only small edges (e.g., when the polygon is used for representing a curve object). This paper proposes a method for computing the optimal ICRs for frictional two-fingered grasp of a polygon such that each ICR is allowed to extend across consecutive edges of the polygon. The time complexity of the method is O(n2log n), where n is the number of edges of the polygon. Implementation results using several test polygons are presented to exhibit effectiveness of the method.

In this work, we discuss the design, construction, and testing of a cable-controlled motion simulator for a Virtual Reality (VR) hang gliding environment. The system comprises a cable-controlled motion simulator, a joystick, a Lego™ direction sensor, and a VR environment. The motion simulator and joystick are built out of motors, pulleys, cables, and aluminum beams. The VR environment and motion simulator interact haptically with each other to give a realistic feel to the operator. A dynamic analysis is performed on the simulator to show the effect of gravity and the directional motion on the operator. A series of experiments are then performed to test the effectiveness of the cable-controlled simulator, and the results were very encouraging despite minor glitches with high-speed maneuvers.

This paper deals with dynamic dimensional synthesis of the Delta robot using the pressure/transmission angle constraints. Two types of pressure/transmission angles are defined, with which the direct and indirect singularities can be identified in a straightforward manner. Two novel global dynamic metrics are proposed for minimisation, which are associated respectively with the inertial and centrifuge/Coriolis components of the driving torque. Various geometrical and performance constraints are taken into account in terms of workspace/machine volume ratio, pressure/transmission angles, etc. The effects of pressure/transmission angle constraints on the feasible domain of design variables are investigated in depth via an example, and a set of optimised dimensional parameters is obtained for achieving a good kinematic and dynamic performance throughout the entire task workspace.

In this paper, a numerical investigation of the Model Predictive Control strategy applied to flexible-link mechanisms is presented. The mechanisms used for all the tests are a planar five-link mechanisms. The tests are aimed at showing how the proposed control system can be used for the trajectory tracking and the vibration suppression. An analysis of the effects of the choice of tuning parameters is presented as well. The design of the predictive controller is based on a linearized version of an accurate nonlinear dynamic model. The effectiveness of the proposed approach is confirmed by extensive numerical results.

The paper introduces a novel general feedback control framework, which allows applying the motion controllers originally dedicated for the unicycle model to the motion task realization for the car-like kinematics. The concept is formulated for two practically meaningful motorizations: with a front-wheel driven and with a rear-wheel driven. All the three possible steering angle domains for car-like robots—limited and unlimited ones—are treated. Description of the method is complemented by the formal stability analysis of the closed-loop error dynamics. The effectiveness of the method and its limitations have been illustrated by numerous simulations conducted for the three main control tasks, namely, for trajectory tracking, path following, and set-point regulation.

In this paper, a planar 3-DOF XYγ parallel micromanipulator with monolithic structure is presented. The micromanipulator is driven by three piezoelectric (PZT) actuators. To achieve highly accurate control, a new approach investigating the relationship among input-force, payload, stiffness, and displacement (IPSD model) of the XYγ micromanipulator is proposed in analytical style, and the analytical expression of the relationship between driving voltages of PZT actuators and outputs of end-effector is deduced based on the IPSD model. Finally, in order to verify the IPSD model, the simulations by finite element method and experiment are performed. The micromanipulator can be used to do microtasks that need the manipulator perform only planar motion, such as microoperation and microassembly, and the proposed IPSD model is useful for both digital control and design of the XYγ micromanipulator.

This work proposes a teleoperation architecture for mobile robots in partially unknown environments under the presence of variable time delay. The system is provided with artificial intelligence represented by a probabilistic path planner that, in combination with a prediction module, assists the operator while guaranteeing a collision-free motion. For this purpose, a certain level of autonomy is given to the system. The structure was tested in indoor environments for different kinds of operators. A maximum time delay of 2s was successfully coped with.

In this paper, a dynamic task allocation and controller design methodology for cooperative robot teams is presented. Fuzzy-logic-based utility functions are derived to quantify each robot's ability to perform a task. These utility functions are used to allocate tasks in real time through a limited lookahead control methodology partially based on the basic principles of discrete event supervisory control theory. The proposed controller design methodology accommodates flexibility in task assignments, robot coordination, and tolerance to robot failures and repairs. Implementation details of the proposed methodology are demonstrated through a warehouse patrolling case study.

Existing sonar rings are limited in their refresh rate to the transmit echo rate, that is, waiting for maximum range echoes to arrive before transmitting again. This paper presents a sonar ring refreshing at 60 Hz for 5.7-m range, which is twice the transmit echo rate, and this leads to lower latency, denser measurements. Two custom Field Programmable Gate Array signal processors provide real time continuous match filtering with dynamic templates. A new method is implemented to select the transmit time from a random set based on minimizing interference. Experiments demonstrate the increased refresh rate, interference rejection, and maps generated by the sonar ring.

The recent developments in applications that have been designed to increase road safety require reliable and trustworthy sensors. Keeping this in mind, the most up-to-date research in the field of automotive technologies has shown that LIDARs are a very reliable sensor family. In this paper, a new approach to road obstacle classification is proposed and tested. Two different LIDAR sensors are compared by focusing on their main characteristics with respect to road applications. The viability of these sensors in real applications has been tested, where the results of this analysis are presented.

Matched filtering optimally estimates the arrival time for a sonar sensor by correlating received signals with templates. This paper presents a sonar ring with continuous matched filtering on 48 receiver channels sampled at 500kHz. The design dynamically switches the matched filter templates to account for pulse shape variations with range. To achieve real-time, low-latency and optimal performance, processing is implemented on an field-programmable gate array (FPGA) transmitting sonar pulses (2 periods of a 45kHz sine wave) at repetition rate of 30-Hz to 5.7-m range. The paper describes the removal of secondary peaks of the correlation output of matched filtering and template selection. Results include sonar maps, accuracy measurements and localization of weak targets.

A systematic method is developed for the type synthesis of 4-DOF nonoverconstrained parallel mechanisms with three translations and one rotation inspired by the design of H-4. First, the motion requirements of primary platform and secondary platform of the 4-DOF nonoverconstrained parallel mechanisms are analyzed, and the conflict between the number of actuators and the constraint system for nonoverconstrained parallel mechanism is solved. Then, the research topic of type synthesis of 4-DOF nonoverconstrained parallel mechanisms is transformed into the type synthesis of the secondary platform with three translational DOF linked by two chains. On the basis of the screw and reciprocal theory, all possible secondary limbs with 3-DOF, 4-DOF, and 5-DOF are synthesized, respectively. Finally, the configurations and spatial assembly conditions of all possible secondary limbs are provided and some typical mechanisms are sketched as examples.