Performance evaluation of pure-motion tasks for mobile robots with respect to world models

The evaluation of the performance of robot motion methods and systems is still an open challenge, although substantial progress has been made in the field over the years. On the one hand, these techniques cannot be evaluated off-line, on the other hand, they are deeply influenced by the task, the environment and the specific representation chosen for it. In this paper we concentrate on “pure-motion tasks”: tasks that require to move the robot from one configuration to another, either being an independent sub-task of a more complex plan or representing a goal by itself. After characterizing the goals and the tasks, we describe the commonly-used problem decomposition and different kinds of modeling that can be used, from accurate metric maps to minimalistic representations. The contribution of this paper is an evaluation framework that we adopt in a set of experiments showing how the performance of the motion system can be affected by the use of different kinds of environment representations.     

Planning for dynamic multiagent planar manipulation with uncertainty: a game theoretic approach

This paper addresses the planning problem for multiagent dynamic manipulation in the plane. The objective of planning is to design the forces exerted on the object by agents with which the object can follow a given trajectory in spite of the uncertainty on pressure distribution. The main novelty of the proposed approach is the integration of noncooperative and cooperative games between agents in an hierarchical manner. Based on a dynamic model of the pushed object, the coordination problem is solved in two levels. In the lower control level, a fictitious force controller is designed by using a minimax technique to achieve the tracking performance. The design procedure is divided into two steps. First, a linear nominal controller is designed via full-state linearization with desired eigenvalues assignment. Next, a minimax control scheme is specified to optimally attenuate the worst-case effect of the uncertainty due to pressure distribution and achieve a minimax tracking performance. In the coordination level, a cooperative game is formulated between agents to distribute the fictitious force, and the objective of the game is to minimize the worst-case interaction force between agents and the object. Simulations are carried out for two-agent and three-agent manipulations, results demonstrate the effectiveness of the planning method.     

A multi-agent based approach to dynamic scheduling with flexible processing capabilities

A multi-agent based system is proposed to simultaneous scheduling of flexible machine groups and material handling system working under a manufacturing dynamic environment. The proposed model is designed by means of \(\hbox {Prometheus}^{\mathrm{TM}}\) methodology and programmed in \(\hbox {JACK}^{\mathrm{TM}}\) agent based systems development environment. Each agent in the model is autonomous and has an ability to cooperate and negotiate with the other agents in the system. Due to these abilities of agents, the structure of the system is more suitable to handle dynamic events. The proposed dynamic scheduling system is tested on several test problems the literature and the results are quite satisfactory because it generates effective schedules for both dynamic cases in the real time and static problem sets. Although the model is designed as an online method and has a dynamic structure, obtained schedule performance parameters are very close to those obtained from offline optimization based algorithms.     

Adaptive tracking control for uncertain dynamic nonholonomic mobile robots based on visual servoing

The trajectory tracking control problem of dynamic nonholonomic wheeled mobile robots is considered via visual servoing feedback. A kinematic controller is firstly presented for the kinematic model, and then, an adaptive sliding mode controller is designed for the uncertain dynamic model in the presence of parametric uncertainties associated with the camera system. The proposed controller is robust not only to structured uncertainties such as mass variation but also to unstructured one such as disturbances. The asymptotic convergence of tracking errors to equilibrium point is rigorously proved by the Lyapunov method. Simulation results are provided to illustrate the performance of the control law.     

Grip force and force sharing in two different manipulation tasks with bottles

Abstract

Grip force and force sharing during two activities of daily living were analysed experimentally in 10 right-handed subjects. Four different bottles, filled to two different levels, were manipulated for two tasks: transporting and pouring. Each test subject’s hand was instrumented with eight thin wearable force sensors. The grip force and force sharing were significantly different for each bottle model. Increasing the filling level resulted in an increase in grip force, but the ratio of grip force to load force was higher for lighter loads. The task influenced the force sharing but not the mean grip force. The contributions of the thumb and ring finger were higher in the pouring task, whereas the contributions of the palm and the index finger were higher in the transport task. Mean force sharing among fingers was 30% for index, 29% for middle, 22% for ring and 19% for little finger.

Practitioner Summary: We analysed grip force and force sharing in two manipulation tasks with bottles: transporting and pouring. The objective was to understand the effects of the bottle features, filling level and task on the contribution of different areas of the hand to the grip force. Force sharing was different for each task and the bottles features affected to both grip force and force sharing.     

Modal sensitivity analysis of planar robots,based on a simplified CMS approach

The modal properties of industrial robots have become a major issue following the increasing demand for faster, lighter manipulators. In this article, the basic in-plane and out-of-plane modal analysis of a planar robot with revolute joints is conducted via component mode synthesis (CMS) using a limited number of low-order monomials as mode shapes for the different links, and an automatic coordinate reduction procedure in the assembly phase which accounts for the physical characteristics of the joints. This model is then used to study the effect of variations in configuration, payload and various physical parameters on the natural frequencies of the robot. As regards the influence of physical parameter variations, frequency sensitivity coefficients are evaluated in a straightforward manner requiring only one eigenvalue analysis, and allow to determine the eigenvalue variations. It is observed that relatively large variations of parameters can be accommodated using these sensitivity coefficients.     

An approximate dynamic programming based approach to dual adaptive control

In this paper, an approximate dynamic programming (ADP) based strategy is applied to the dual adaptive control problem. The ADP strategy provides a computationally amenable way to build a significantly improved policy by solving dynamic programming on only those points of the hyper-state space sampled during closed-loop Monte Carlo simulations performed under known suboptimal control policies. The potentials of the ADP approach for generating a significantly improved policy are illustrated on an ARX process with unknown/varying parameters.     

A dynamic scheme for scheduling complex tasks in manufacturing systems based on collaboration of agents

The characteristics of scheduling tasks in the real world is a dynamic and challenging issue as the processes and the companies involved may change from time to time. For small flexible enterprises to respond to business opportunities, an effective scheme to facilitate dynamic coalition, share the core competencies and resources and support inter-enterprise collaboration must be developed. Although multi-agent systems (MAS) provide a paradigm for modeling these characteristics, scheduling tasks in MAS is a complex problem due to the computational complexity involved, distributed architecture for scheduling tasks by individual agents and dependency of different agents’ workflows. How to develop a problem solver that can be applied in MAS to achieve coherent and consistent workflow schedules that can meet a customer’s order is an important issue. In this paper, we propose a solution methodology for scheduling workflows in MAS. Our solution combines the multi-agent system architecture to dynamically discover services, workflow and activity models to specify the capabilities of agents, contract net protocol to facilitate negotiation and coordination of agents and optimization theories to optimize the cost for fulfilling an order. A problem solver for scheduling tasks in MAS has been implemented. An application scenario has also been provided to verify our solution methodology.     

Adaptive dynamic locomotion of quadrupedal robots with semicircular feet on uneven terrain

This paper proposes an adaptive trajectory generation method for quadruped robots with semicircular feet to control body speed and heading, and to minimize power consumption on uneven terrain. The semicircular foot with single line of contact is easier to solve the kinematic problems than flat feet with active ankle joints. And its wheel-like rolling motion leads to improvement in power autonomy and reduction of impact forces. The adaptive gait patterns are changed by the sequential modulation of the locomotion period and the stride per step which are determined by the desired body speed and heading commands, and external environments. The efficiency and performance of the developed method are verified through computer simulations and experiments using a hydraulic actuated quadrupedal robot.     

基于动态过程模拟的定量化HAZOP分析方法

HAZOP分析是一种广泛使用的过程安全评价方法,但缺乏定量化的评价依据。为了有效地辨识过程工业中潜在危险,在传统HAZOP方法基础上,提出了基于动态过程模拟的定量化HAZOP分析方法。首先进行HAZOP分析,辨识偏差原因和后果,然后建立动态过程模拟模型,通过预制故障模拟不同程度偏差原因对偏差后果的动态影响,得到偏差原因与后果之间的量化关系,并且通过模拟获得偏差原因的安全操作极限数据,分析现有安全保护措施的有效性,最后对偏差的调节措施进行模拟优化分析。为了验证所提出方法的有效性,以某气体分馏装置脱丙烷单元作为应用实例,采用Unisim软件建立动态过程模拟模型,对HAZOP偏差—“脱丙烷塔顶压力过高”的危险场景进行了模拟。研究结果表明,所提出的方法是对传统HAZOP分析的补充和扩展,实现了HAZOP偏差的定量化,从而提高了HAZOP分析的准确性和可靠性,对过程安全管理具有重要指导意义。     

A neuro-genetic-simulated annealing approach to the inverse kinematics solution of robots: a simulation based study

In this study, a hybrid intelligent solution system including neural networks, genetic algorithms and simulated annealing has been proposed for the inverse kinematics solution of robotic manipulators. The main purpose of the proposed system is to decrease the end effector error of a neural network based inverse kinematics solution. In the designed hybrid intelligent system, simulated annealing algorithm has been used as a genetic operator to decrease the process time of the genetic algorithm to find the optimum solution. Obtained best solution from the neural network has been included in the initial solution of genetic algorithm with randomly produced solutions. The end effector error has been reduced micrometer levels after the implementation of the hybrid intelligent solution system.     

A simple approach to the control of locomotion in self-reconfigurable robots

In this paper we present role-based control which is a general bottom-up approach to the control of locomotion in self-reconfigurable robots. We use role-based control to implement a caterpillar, a sidewinder, and a rolling track gait in the CONRO self-reconfigurable robot consisting of eight modules. Based on our experiments and discussion we conclude that control systems based on role-based control are minimal, robust to communication errors, and robust to reconfiguration.     

A supervisory loop approach to fulfill workspace constraints in redundant robots

An approach based on geometric invariance and sliding mode ideas is proposed for redundancy resolution in robotic systems to fulfill configuration and workspace constraints caused by robot mechanical limits, collision avoidance, industrial security, etc. Some interesting features of the proposal are that: (1) it can be interpreted as a limit case of the classical potential field-based approach for collision avoidance which requires using variable structure control concepts, (2) it allows reaching the limit surface of the constraints smoothly, depending on a free design parameter, and (3) it can be easily added as a supervisory block to pre-existing redundancy resolution schemes. The algorithm is evaluated in simulation on a 6R planar robot and on the freely accessible 6R robot model PUMA-560, for which the main features of the method are illustrated.     

A dynamic priority based path planning for cooperation of multiple mobile robots in formation forming

Robots that work in a proper formation show several advantages compared to a single complex robot, such as a reduced cost, robustness, efficiency and improved performance. Existing researches focused on the method of keeping the formation shape during the motion, but usually neglect collision constraints or assume a simplified model of obstacles. This paper investigates the path planning of forming a target robot formation in a clutter environment containing unknown obstacles. The contribution lies in proposing an efficient path planner for the multiple mobile robots to achieve their goals through the clutter environment and developing a dynamic priority strategy for cooperation of robots in forming the target formation. A multirobot system is set up to verify the proposed method of robot path planning. Simulations and experiments results demonstrate that the proposed method can successfully address the collision avoidance problem as well as the formation forming problem.     

A novel approach to validate online signature using machine learning based on dynamic features

Neural Computing and Applications - This paper presents a new and mathematical method for online signature validation based on machine learning. In this way, the average values of the factors are...     

Provably safe navigation for mobile robots with limited field-of-views in dynamic environments

This paper addresses the problem of navigating in a provably safe manner a mobile robot with a limited field-of-view placed in a unknown dynamic environment. In such a situation, absolute motion safety (in the sense that no collision will ever take place whatever happens in the environment) is impossible to guarantee in general. It is therefore settled for a weaker level of motion safety dubbed passive motion safety: it guarantees that, if a collision takes place, the robot will be at rest.