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This paper presents two new algorithms for real-time calculation of the wheel angles and speeds of gantry tractor modules. In transport mode, the gantry tractor is, in a sense, a snakelike robot with passive joints and active wheels, with each module having autonomous four-wheel drive and four-wheel steering. The algorithms determine the wheel angles and speeds of each module with the prescription that the four wheels will have the same center of curvature, wheel speeds provide cooperative redundancy, and all hitching points follow the same path, thereby eliminating scuffing and minimizing off-tracking. Details of the analytical algorithm for a predetermined path were presented at the 2009 IEEE International Conference on Industrial Technology, together with a simulation for a single module. In this paper, we also present the results of a newly developed numerical algorithm which enables the gantry tractor to be steered online by an operator. We also show, by simulation, that this new numerical algorithm gives a good approximation to analytical solutions. The numerical algorithm is then used to calculate wheel angles and speeds for a three-module tractor with the results depicted graphically as functions of time. [ABSTRACT FROM AUTHOR]

A hybrid generator with a photovoltaic energy conversion system is proposed with supercapacitors and lead-acid batteries in a dc-coupled structure. The objective of this system is to supply the prescribed reactive and active power to the grid. This paper focuses on the strategy, which makes it possible to ensure a high battery state of charge and overcharge security by designing a dedicated local control system. A continuous dynamic model and a control design of the power system studied are proposed in this paper. Simulation and experimental results illustrate the performances obtained. [ABSTRACT FROM AUTHOR]

Antilock braking systems (ABSs) are usually designed based on controlling the wheel slip ratio so as to maintain each wheel in a presumed stable region. Since the optimal slip ratio (which results in maximum tire–road friction) varies with the type of road, current methods are not efficient in the sense of achieving the shortest possible stopping distance. This paper introduces an efficient ABS, in which the brake commands directly maximize the longitudinal component of tire–road friction at each wheel of the vehicle independently. The tire–road friction is estimated using a torque balance equation at each wheel, and within those equations, real-time estimates of the effective radius of tire are used. A step-by-step algorithm for computing the brake commands that maximize the tire–road friction is also presented. Three challenging braking scenarios were tested using the comprehensive CarSim simulation environment. The results show that, in comparison to conventional ABS, our method significantly reduces the stopping distance and improves the vehicle stability. [ABSTRACT FROM PUBLISHER]

Multirobot systems represent an enticing area of research with numerous real-world applications. Teams of multiple robots can achieve tasks that are more difficult or even impossible for a single robot, e.g., environment exploration, search and rescue, or surveillance operations. In a previous work, the authors developed a system for the single-operator manual control of a multirobot system. However, such teleoperation systems commonly suffer from inadequate perception of the remote environment. This paper extends the previously presented work by adding a fuzzy force-feedback (FFF) augmentation for the manual control of a multirobot system. The FFF augmentation delivers additional information to the operator. Moreover, it guides the operator toward the smooth control of the robotic group. The force feedback was generated by a system of fuzzy controllers monitoring the state of the multirobot group. The performance of the system was evaluated in a virtual environment, and the recorded forces were explored in various scenarios. The force-feedback augmentation demonstrated the following improvements: 1) operator's increased obstacle awareness and 2) improved maneuvering performance. [ABSTRACT FROM PUBLISHER]

This paper investigates the sampled-data control problem for spacecraft relative positional holding with limited thrust and thrust nonlinearity. The relative dynamic model is established based on the Clohessy–Wiltshire equations. Sector nonlinearity is employed to describe the nonlinear behavior of the chaser's thruster. The relative position holding problem is regarded as a sampled-data output tracking control problem, and the disturbance attenuation for the closed-loop system is considered. By a Lyapunov approach, the controller design is cast into a convex optimization problem. Simulation results show the effectiveness and advantage of the proposed controller design method. [ABSTRACT FROM PUBLISHER]

This paper presents a mathematical dynamic model of single-phase four-quadrant (4Q) converters employed at the input stage onboard high-speed trains. A new stability analysis capable of considering the time-variant nature of the system for the correct tuning of the feedback proportional-integral (PI) controller has been implemented. In particular, the innovation regards the application of a current-controlled modulation technique instead of the traditional PWM control currently used in high power traction converters. A dedicated model of a real converter installed onboard Italian high-speed trains has also been implemented in order to simulate its behavior and validate the theoretical analysis. Finally, a scaled-down prototype has been developed. [ABSTRACT FROM AUTHOR]