On the power of enzymatic numerical P systems

We study the computing power of a class of numerical P systems introduced in the framework of autonomous robot control, namely enzymatic numerical P systems. Three ways of using the evolution programs are investigated: sequential, all-parallel and one-parallel (with the same variable used in all programs or in only one, respectively); moreover, both deterministic and non-deterministic systems are considered. The Turing universality of some of the obtained classes of numerical P systems is proved (for polynomials with the smallest possible degree, one, also introducing a new proof technique in this area, namely starting the universality proof from the characterization of computable sets of numbers by means of register machines). The power of many other classes remains to be investigated.     

Harmony search-based hybrid stable adaptive fuzzy tracking controllers for vision-based mobile robot navigation

In this paper the harmony search (HS) algorithm and Lyapunov theory are hybridized together to design a stable adaptive fuzzy tracking control strategy for vision-based navigation of autonomous mobile robots. The proposed variant of HS algorithm, with complete dynamic harmony memory (named here as DyHS algorithm), is utilized to design two self-adaptive fuzzy controllers, for $x$ -direction and $y$ -direction movements of a mobile robot. These fuzzy controllers are optimized, both in their structures and free parameters, such that they can guarantee desired stability and simultaneously they can provide satisfactory tracking performance for the vision-based navigation of mobile robots. In addition, the concurrent and preferential combinations of global-search capability, utilizing DyHS algorithm, and Lyapunov theory-based local search method, are employed simultaneously to provide a high degree of automation in the controller design process. The proposed schemes have been implemented in both simulation and real-life experiments. The results demonstrate the usefulness of the proposed design strategy and shows overall comparable performances, when compared with two other competing stochastic optimization algorithms, namely, genetic algorithm and particle swarm optimization.     

A continuous dynamic modeling approach for an omnidirectional mobile robot

MY wheel-II is one of switch omnidirectional wheel mechanisms. The omnidirectional mobile robot based on MY wheels-II is a switched non-linear system (i.e. discontinuous system). The aim of this paper is to propose a continuous modeling approach which can be employed to derive a continuous model from any given discontinuous robot dynamic model. This approach results in a continuous non-linear parameter varying (NLPV) model, and offers one solution for model-based control design. Firstly, our previously proposed average dynamic modeling approach is analyzed. We find that this modeling approach is effective only for a specific class of robot configurations. To overcome this problem, we first derive the switching conditions of MY wheel-II. Based on derived switching conditions, we then propose a simple continuous NLPV modeling approach. The new approach replaces the real discontinuous contact radius in the discontinuous dynamic model with an adaptive continuous curve. An illustrative example of the adaptive continuous curve design is provided. Both simulation and experimental results verify the effectiveness of the proposed NLPV modeling approach against the average modeling approach.     

Visual graph modeling for scene recognition and mobile robot localization

Image retrieval and categorization may need to consider several types of visual features and spatial information between them (e.g., different point of views of an image). This paper presents a novel approach that exploits an extension of the language modeling approach from information retrieval to the problem of graph-based image retrieval and categorization. Such versatile graph model is needed to represent the multiple points of views of images. A language model is defined on such graphs to handle a fast graph matching. We present the experiments achieved with several instances of the proposed model on two collections of images: one composed of 3,849 touristic images and another composed of 3,633 images captured by a mobile robot. Experimental results show that using visual graph model (VGM) improves the accuracies of the results of the standard language model (LM) and outperforms the Support Vector Machine (SVM) method.     

Using occupancy grids for mobile robot perception and navigation

An approach to robot perception and world modeling that uses a probabilistic tesselated representation of spatial information called the occupancy grid is reviewed. The occupancy grid is a multidimensional random field that maintains stochastic estimates of the occupancy state of the cells in a spatial lattice. To construct a sensor-derived map of the robot's world, the cell state estimates are obtained by interpreting the incoming range readings using probabilistic sensor models. Bayesian estimation procedures allow the incremental updating of the occupancy grid, using readings taken from several sensors over multiple points of view. The use of occupancy grids from mapping and for navigation is examined. Operations on occupancy grids and extensions of the occupancy grid framework are briefly considered     

Development of tethered autonomous mobile robot systems for field works

This paper describes the implementation details, advantages and potential applications of autonomous tethered mobile robot systems using the 'hyper-tether' concept. Hyper-tether is a new research area on tethered connections, which provide tethering among different mobile robot types, such as a robot with the environment and a robot with humans and animals. Its basic function is to actively control the tether's tension and/or length, but it also considers tether launching, anchoring, power delivery, data communication cabling and built-in trajectory command generation capabilities. Many of these features can be efficiently applied to build a tethered mobile robot system which remotely manipulates a working tool that can be useful for land-mine detection and removal, trimming of gardens and grass cutting of wide areas (e.g. golf courses, soccer and baseball fields), spraying of agricultural chemicals, forestry and construction works, etc. In this paper, a simple prototype of hypertether's winch-tether pair and a working tool equipped with a grass cutter was constructed, and basic experiments were performed to demonstrate the validity of the proposed system.     

Evolving controllers for autonomous robot search teams

Deploying autonomous robot teams instead of humans in hazardous search and rescue missions could provide immeasurable benefits. In such operations, rescue workers often face environments where information about the physical conditions is impossible to obtain, which not only hampers the efficiency and effectiveness of the effort, but also places the rescuers in life-threatening situations. These types of risk promote the potential for using robot search teams in place of humans. This article presents the design and implementation of controllers to provide robots with appropriate behavior. The effective utilization of genetic algorithms to evolve controllers for teams of homogeneous autonomous robots for area coverage in search and rescue missions is described, along with a presentation of a robotic simulation program which was designed and developed. The main objective of this study was to contribute to efforts which attempt to implement real-world robotic solutions for search and rescue missions.     

Development of membrane controllers for mobile robots

The main contribution of this paper is the introduction of the new concept of membrane controller based on the structure and functioning of a deterministic numerical P system. The procedure for developing a membrane controller and for using it to control a mobile robot is explained and several test cases are given in which membrane controllers are used to control both simulated and real mobile robots and to generate various desired behaviours (obstacle avoidance, wall following, and follow the leader). The experiments reported in this paper validate the concept and prove that the performance of a membrane controller is comparable to or better than that of other controllers (such as fuzzy logic controllers).     

Polynomial family of PD-type controllers for robot manipulators

This paper addresses the problem of position control for robot manipulators. A new polynomial family of PD-type controllers with gravity compensation for the global position of robots manipulators is presented. The previous results on the linear PD controller are extended to the proposed polynomial family. The classical PD controller can be found among this large class of controllers when its proportional gain is a diagonal matrix. The main contribution of this paper is to prove that the closed-loop system composed by full nonlinear robot dynamics and the proposed family of controllers is globally asymptotically stable in agreement with Lyapunov's direct method and LaSalle's invariance principle. Besides the theoretical results, a real-time experimental comparison is also presented to illustrate the performance of the proposed family with other well-known control algorithms such as PD and PID schemes on a three degrees of freedom direct-drive arm.     

Optimization of interval type-2 fuzzy logic controllers for a perturbed autonomous wheeled mobile robot using genetic algorithms

We describe a tracking controller for the dynamic model of a unicycle mobile robot by integrating a kinematic and a torque controller based on type-2 fuzzy logic theory and genetic algorithms. Computer simulations are presented confirming the performance of the tracking controller and its application to different navigation problems.     

A real-time responsiveness measurement method of linux-based mobile systems for P2P cloud systems

Linux-based mobile computing systems such as robots, electronic control devices, and smart-phone are the most important types of P2P cloud systems in recent days. To improve the overall performance of networked systems, each mobile computing system requires real-time characteristics. For this reason, mobile computing system developers want to know how well real-time responsiveness is supported; several real-time measurement tools have been proposed. However, those previous tools have their own measurement schemes and we think that the results from those models do not show how responsive those systems are. In this paper, we propose ELRM, a new real-time measurement method that has clear measurement interval definitions and an accurate measurement method for real-time responsiveness. We evaluate ELRM on various mobile computing systems and compare it with other existing models. As a result, our method can obtain more accurate and intuitive real-time responsiveness measurement results.     

未知环境下的移动机器人环境建模研究

环境建模技术是移动机器人自主导航研究中的一个关键问题。为了实现机器人在未知环境下的自主导航,本文在分析当前普遍采用的一些环境建模方法及其缺点的基础上,提出一种基于多传感器信息融合的环境建模方法。实验结果表明该方法有效地克服了传感器的累计误差,有效地提高了环境建模的准确性。此方法的可行性和有效性通过Pioneer3-DX移动机器人得到了实验验证。     

未知环境下的移动机器人环境建模研究

环境建模技术是移动机器人自主导航研究中的一个关键问题。本文给出一种基于多传感器信息融合的环境建模方法。实验结果表明该方法有效地克服了传感器的累计误差,有效地提高了环境建模的准确性。此方法的可行性和有效性通过Pioneer3-DX移动机器人得到了实验验证。     

Self-tuning controllers for nonlinear systems

Two new self-tuning control (STC) strategies for nonlinear control problems are proposed. These strategies are applicable to a broad class of nonlinear single-input, single-output systems which can include arbitrary nonlinear functions of the output and the old inputs as well as the products of these functions and any power of the most recent input. Simulation results for a stirred-tank chemical reactor demonstrate that the new nonlinear STC strategy provides significant improvement over conventional STCs based on linear models.     

Mean controllers for discrete systems

A controller, called the mean controller, is presented. The mean controller minimizes the supremum of the mean of the absolute value of the output for all time and all external inputs. A performance index and a random input space are proposed. The analysis, which is restricted to discrete-time single-input single-output stochastic systems, yields the mean controller and considers its stability. The simulations illustrate the operation of the mean controller.     

移动机器人无线局域网控制系统

设计了一种移动机器人无线局域网控制系统,采用0penWrt系统的无线路由器建立无线局域网,与FPGA进行数据转换,设计了系统的人机交互界面。通过WiFi,操作人员可以对移动机器人进行遥操作控制。通过整体设计使得系统能通过无线局域网将移动机器人控制器与上位机控制平台联系起来进行数据交流,实现上位机对移动机器人的遥操作控制功能以及对移动机器人的监测功能。     

Multipurpose controllers for multivariable systems

The primary purpose of this paper is to outline a new procedure for designing controllers which simultaneously achieve a variety of desired design goals in deterministic, unity feedback, linear multivariable systems. More specifically, we will present a new algorithm for the systematic design of a "three-part" multivariable controller which simultaneously ensures: 1) a noninteractive or decoupled closed-loop design, 2) complete and arbitrary closed-loop pole placement, which implies desired (single-loop) transient performance as well as closed-loop stability, 3) zero steady-state errors between the plant outputs and any nondecreasing deterministic inputs, 4) complete steady-state output rejection of nondecreasing deterministic disturbances, and 5) robustness with respect to stability, disturbance rejection, and zero error tracking for rather substantial plant parameter variations. Our development will employ the more "modern" (Laplace-transformed) differential operator approach for controller synthesis, which involves transfer matrix factorizations and the manipulation of polynomial matrices in the Laplace operators.     

A class of nonlinear PD-type controllers for robot manipulators

In this article we present the stability analysis of a class of PD-type controllers for position and motion control of robot manipulators. The main feature of this class of controllers is that the proportional and derivative gains can be nonlinear functions of the robot states. These controllers can be obtained from control strategies that adjust the controller gains depending on the robot states. It is shown that global asymptotic stability of the control system is achieved provided that the P and D gains have suitable structure. As an outcome, we propose a global regulator constrained to deliver torques within prescribed limits of the actuator's capabilities. Experimental results on a two degrees of freedom direct drive arm show the usefulness of the proposed scheme. © 1996 John Wiley & Sons, Inc.