A distributed fuzzy logic controller for an autonomous vehicle

Autonomous vehicles can be used in a variety of applications such as hazardous environments or intelligent highway systems. Fuzzy logic is an appropriate choice for this application as it can describe human behavior well. This paper proposes two fuzzy logic controllers for the steering and the velocity control of an autonomous vehicle. The two controllers are divided into separate modules to mimic the way humans think while driving. The steering controller is divided into four modules; one module drives the vehicle toward the target while another module avoids collision with obstacles. A third module drives the vehicle through mazes. The fourth module adjusts the final orientation of the target. The velocity controller is divided into three modules; the first module speeds up the vehicle to reach the target and slows it down as it moves toward the target. The second module controls the velocity in the neighborhood of obstacles. A third module controls the velocity of the vehicle as it turns sharp corners. A method for automatic tuning of the first module of the velocity controller is proposed to stabilize the velocity of the vehicle as it approaches the target. Two examples to demonstrate the interaction among the seven control modules are included. Results of the simulation are compared with those in the literature. © 2004 Wiley Periodicals, Inc.     

An approach to analyzing biped locomotion dynamics and designing robot locomotion controls

An approach to analyzing biped locomotion problems is presented. This approach applies the principles of Lagrangian dynamics to derive the equations of motion of locomotion gaits, state-variable techniques to analyze locomotion dynamics, and multivariable feedback to design locomotion controls. A robot model which has no knee joints or feet and is constrained to motion in the sagittal plane is chosen as a sufficiently simple model of a biped to illustrate the approach. A goal of the analysis is the design of a locomotion control for the robot which produces a walking gait having a velocity and stride length similar to those of a human walking gait. The principle feature of the approach is a much deeper understanding of the dynamics of biped locomotion than previous approaches have provided.     

Bounded controllers for global path tracking control of unicycle-type mobile robots

This paper presents a design of bounded controllers with a predetermined bound for global path tracking control of unicycle-type mobile robots at the torque level. A new one-step ahead backstepping method is first introduced. The heading angle and linear velocity of the robots are then considered as immediate controls to force the position of the robots to globally and asymptotically track its reference path. These immediate controls are designed based on the one-step ahead backstepping method to yield bounded control laws. Next, the one-step ahead backstepping method is applied again to design bounded control torques of the robots with a pre-specified bound. The proposed control design ensures global asymptotical and local exponential convergence of the position and orientation tracking errors to zero, and bounded torques driving the robots. Experimental results on a Khepera mobile robot verify the proposed control controller.     

Design of neural networks for fast convergence and accuracy:dynamics and control

A procedure for the design and training of artificial neural networks, used for rapid and efficient controls and dynamics design and analysis for flexible space systems, has been developed. Artificial neural networks are employed, such that once property trained, they provide a means of evaluating the impact of design changes rapidly. Specifically, two-layer feedforward neural networks are designed to approximate the functional relationship between the component/spacecraft design changes and measures of its performance or nonlinear dynamics of the system/components. A training algorithm, based on statistical sampling theory is presented, which guarantees that the trained networks provide a designer-specified degree of accuracy in mapping the functional relationship. Within each iteration of this statistical-based algorithm, a sequential design algorithm is used for the design and training of the feedforward network to provide rapid convergence to the network goals. Here, at each sequence a new network is trained to minimize the error of previous network. The proposed method should work for applications wherein an arbitrary large source of training data can be generated. Two numerical examples are performed on a spacecraft application in order to demonstrate the feasibility of the proposed approach.     

欠驱动飞艇三维路径跟踪控制

针对欠驱动飞艇的路径跟踪控制问题,提出了一种基于制导向量场的三维路径跟踪控制方法.首先,引入向量场理论.接着基于牛顿–欧拉方程建立欠驱动飞艇动力学模型.基于所提模型和向量场理论构造制导向量场以获得期望姿态角和期望速度.然后结合反步法和PD控制设计路径跟踪控制器,用指令滤波器对控制器设计过程中虚拟控制的导数进行估计,避免了复杂的解析计算.所设计的控制器是由制导向量场子系统、姿态稳定环和速度跟踪环组成的内外环结构.稳定性分析证明了飞艇的路径跟踪误差最终一致有界.最后仿真结果验证了所提出方法的有效性.     

Flocking of multi‐agent dynamical systems with intermittent nonlinear velocity measurements

In this paper, the problem of flocking control in networks of multiple dynamical agents with intermittent nonlinear velocity measurements is studied. A new flocking algorithm is proposed to guarantee the states of the velocity variables of all the dynamical agents to converge to consensus while ensuring collision avoidance of the whole group, where each agent is assumed to obtain some nonlinear measurements of the relative velocity between itself and its neighbors only on a sequence of non‐overlapping time intervals. The results are then extended to the scenario of flocking with a nonlinearly dynamical virtual leader, where only a small fraction of agents are informed and each informed agent can obtain intermittent nonlinear measurements of the relative velocity between itself and the virtual leader. Theoretical analysis shows that the achieved flocking in systems with or without a virtual leader is robust against the time spans of the agent speed‐sensors. Finally, some numerical simulations are provided to illustrate the effectiveness of the new design. Copyright © 2011 John Wiley & Sons, Ltd.     

A system approach for control development of lower-limbs training machines

This paper presents the approach undertaken for the specification and design of the control system of a machine for training and rehabilitation of lower limbs. The resulting hybrid and hierarchical control system interprets the training specifications provided by a physiotherapist for a particular user to execute the corresponding sequence of switching (position, velocity and force) control laws. A generic model, based on the use of an object extension of Statecharts, is proposed for the sequential part of the controller. The design and synthesis of the switching control laws are illustrated for the case of the machine Multi-Iso. Some illustrative training results are also discussed.     

A systematic approach for generating velocity fields in shape optimization

Design velocity fields affect every stage of the shape optimization process. The progress of the optimization process, distortion of the finite element mesh, and final shape are sensitive to the quality of velocity fields. It is important to identify and generate effective velocity fields at the beginning of the process. This paper provides several criteria to determine the effectiveness of velocity fields. A systematic approach for generating these velocity fields using deformation fields is developed. The use of interactive procedures is shown to be indispensable for ensuring the effectiveness and quality of design velocity fields. General strategies and guidelines for generating velocity fields are given. Concepts of weight-reducing, stress-reducing, form-preserving, and smooth basis shapes are presented. Normalization of velocity fields is discussed. A method for controlling mesh distortion during the shape optimization process is given based on an explicit limit on the design change to prevent the Jacobian from vanishing. Two- and three-dimensional design problems are solved.     

A general analytical method for axisymmetric incompressible potential flow about bodies of revolution

A general analytical method is presented for calculating the flow field about bodies of revolution in incompressible potential flow as a sequence of elementary analytic functions (Fourier, Chebyshev and Legendre). For the cases of greatest interest to practical engineering (cusp and blunt trailing edges) comparison with an existing highly accurate numerical method shows that convergence is good. Only ten terms are required to give adequate accuracy for negligible computer usage on bodies with much more character than usually encountered. The theory can be used for design (inverse) operation to produce body shapes associated in a least squares sense with a desired input velocity. It is shown that, when used this way, again good results are obtained with remarkably few terms.     

Adaptive critic motion control design of autonomous wheeled mobile robot by dual heuristic programming

Autonomous wheeled mobile robot (WMR) needs implementing velocity and path tracking control subject to complex dynamical constraints. Conventionally, this control design is obtained by analysis and synthesis or by domain expert to build control rules. This paper presents an adaptive critic motion control design, which enables WMR to autonomously generate the control ability by learning through trials. The design consists of an adaptive critic velocity control loop and a self-learning posture control loop. The neural networks in the velocity neuro-controller (VNC) are corrected with the dual heuristic programming (DHP) adaptive critic method. Designer simply expresses the control objective by specifying the primary utility function then VNC will attempt to fulfill it through incremental optimization. The posture neuro-controller (PNC) learns by approximating the specialized inverse velocity model of WMR so as to map planned positions to suitable velocity commands. Supervised drive supplies variant velocity commands for PNC and VNC to set up their neural weights. During autonomous drive, while PNC halts learning VNC keeps on correcting its neural weights to optimize the control performance. The proposed design is evaluated on an experimental WMR. The results show that the DHP adaptive critic design is a useful base of autonomous control.     

满足故障隔离率指标的测试序列优化差分进化算法

最优测试序列的设计是故障诊断过程中必须解决的非确定多项式（Non-deterministic polynomial,NP）完全问题。基于自适应差分进化算法,提出一种惯性速度差分进化（Inertial velocity differential evolution,IVDE）算法,通过增加额外的惯性速度项求解复杂电子系统最优测试序列问题（Optimal test sequence problem,OTP）。为求解该优化问题设计了个体的状态与测试序列编码方式,构建了包含故障隔离率（Fault isolation rate,FIR）等指标的个体适应度函数,通过优化生成诊断决策树来减少测试设备和测试成本。仿真结果表明,IVDE算法可以求得既满足FIR要求,又减少测试成本的测试序列。与粒子群优化算法（Particle swarm optimizer,PSO）、遗传算法（Genetic algorithm,GA）等其他算法相比,IVDE可以求解OTP,得到更好的解。     

Isogeometric topological shape optimization using dual evolution with boundary integral equation and level sets

An isogeometric topological shape optimization method is developed, using a dual evolution of NURBS curves and level sets; the NURBS curves feature the exact representation of geometry and the level sets help to detect and guide the topological variation of NURBS curves. The implicit geometry by the level sets is transformed into the parametric NURBS curves by minimizing the difference of velocity fields in both representations. A gradient-based optimization problem is formulated, based on the evolution of the NURBS curves. The control points of NURBS curves are taken as design variables. The necessary response and design sensitivity are computed by an isogeometric boundary integral equation method (BIEM) using the NURBS curves. The design sensitivity is obtained on fixed grids and utilized as the velocity to update the Hamilton–Jacobi equation for the level sets. To obtain the whole velocity field on the fixed grids, an interpolation and velocity extension scheme are employed. The developed method provides accurate response and enhanced sensitivity using isogeometric BIEM. Also, additional post-processing is not required to communicate with CAD systems since the optimal design is represented as NURBS curves. Numerical examples demonstrate the accuracy of design sensitivity on fixed grids and the feasibility of shape and topological optimization.     

Fuzzy cognitive map based on structural equation modeling for the design of controls in business-to-consumer e-commerce web-based systems

Security and integrity of business-to-consumer e-commerce web-based systems (ECWS) is becoming a concern among ECWS adopters. The controls for ECWS are classified into controls for system continuity, access controls, communication controls, and informal controls. The control design for ECWS is not well structured and demands understanding of the complex causal relationships among environmental factors (infrastructure, organizational requirements for security), controls, implementation, and performance. In order to aid the design of ECWS controls, the application of a fuzzy cognitive map, ECFCM (EC-control design using a fuzzy cognitive map), was developed. Structural equation modeling was used to identify relevant relationships among the components and indicate their direction and strength. A standardized causal coefficient from structural equation modeling was then used to create a fuzzy cognitive map, through which the state or movement of one control component was shown to have an influence on the state or movement of others. Thus ECFCM provides a practical insight to IS auditors by addressing the applicability of soft approaches in capturing and illustrating the use of FCM in the design of ECWS controls.     

Formation Maneuvering and Target Interception for Multi‐Agent Systems via Rigid Graphs

In this paper, we introduce control laws for multi‐agent formation maneuvering and target interception problems. In the target interception problem, we consider that the target velocity is unknown. Using a single‐integrator agent model, the proposed controls consist of a formation acquisition term, dependent on the graph rigidity matrix, and a formation maneuvering or target interception term. The control laws are only a function of the relative position of agents in an infinitesimally and minimally rigid graph, and either the desired maneuvering velocity of the formation or the target's relative position to the leader. The target interception control includes a continuous dynamic estimation term to identify the unknown target velocity. A Lyapunov‐like stability analysis is used to prove that the control objectives are met.     

SymROP: ROP protein with identical helices redesigned by all-atom contact analysis and molecular dynamics

Experience has shown that protein redesigns (using the backbone from a known protein structure) are far more likely to produce well-ordered, native-like structures than are true de novo designs. Therefore, to design a four-helix bundle made of identical short helices, we here proceed by an extensive redesign of the ROP protein. A fully symmetrical SymROP sequence derived from ROP was chosen by modeling ideal-geometry side chains, including hydrogens, while maintaining the "goodness-of-fit" of side-chain packing by calculating all-atom contact surfaces with the Reduce and Probe programs. To estimate the probable extent of backbone movement and side-chain mobility, restrained molecular dynamics simulations were compared for candidate sequences and controls, including substitution of Abu for all or half the core Ala residues. The resulting 17-residue designed sequence is 41% identical to the relevant regions in ROP. SymROP is intended for construction by the Template Assembled Synthetic Proteins approach, to control the bundle topology, to use short helices, and to allow blocked termini and unnatural amino acids. ROP protein has been a valuable system for studying helical protein structure because of its simplicity and regularity within a structure large enough to have a real hydrophobic core. The SymROP design carries that simplicity and regularity even further.     

Optimal open- and closed-loop control of singularly peturbed linear systems

A simple method is given to obtain either an approximate open- or closed-loop control or an approximate solution to the linear quadratic fixed and free endpoint optimal control problems. This approximation is valid over the entire time interval, or with further computational reduction, only on the open interval. Emphasis is placed on use of control-oriented hypotheses, practical aspects of implementing the approximate controls, and interpretation of these controls. The approximating design procedure given is illustrated through examples which clarify and demonstrate it.     

Isokinetic strength characteristics in wrist flexion and extension

A laboratory experiment was conducted to measure strength characteristics in dynamic (isokinetic) wrist flexion and extension. Twenty four college-age males exerted their maximum torque in both concentric flexion and extension at 60, 120, and 180°/s of angular velocity through a ±60° range of deviation from wrist neutral. Results show that velocity and motion direction significantly effected both peak torque as well as the postural displacement of peak torque. The value of peak torque decreased with an increase in velocity and the wrist angle at peak torque generally moved to a more deviated, flexed posture (from neutral) with increasing velocity as well. Peak torque for all velocity and motion-type conditions tested occurred in a flexed posture relative to neutral. It is anticipated that these results may be of use as biomechanically based considerations in the evaluation and design of upper extremity tasks involving wrist flexion/extension as well as to perhaps give insight into functional characteristics of the wrist. Finally, regression equations were developed to aid in the prediction of peak torque based upon task, individual and/or population parameters.

Relevance to industry

Results from this study should enhance the overall understanding of wrist functioning. Specifically, motion type, velocity of movement and wrist posture are important ergonomic design considerations. These results can also be used to modify existing biomechanical models that do not consider wrist variables.     

A heuristic checklist for an accessible smartphone interface design

Smartphone technology has evolved into a multi-functional device with advanced capabilities, but this mobile technology remains inaccessible to many individuals with visual impairments or upper extremity disabilities. This paper provides a heuristic checklist for accessible smartphone interface design, developed through reviewing existing design standards and guidelines and validating these guidelines with user involvement. Specifically, a set of preliminary user requirements (59 items) was extracted from existing standards, guidelines, and user requirements regarding mobile handheld device accessibility. Subsequently, the requirement set was filtered using a participatory method and then integrated to create an operational version of design guidelines. These guidelines were then used in a heuristic evaluation and usability testing on high-fidelity prototypes produced by a commercial manufacturer. A heuristic checklist for designing accessible smartphones was formed, which may also be applicable to other touchscreen handheld devices (e.g., printer screen) in terms of accessibility features. The initial set of 59 user requirements was re-organized into 44 statements in six general categories: mechanical controls, display, speech and general operation controls, audio feedback controls, touch-operated controls, and others. Using results from both qualitative and quantitative methods provides support, though with some limitations, for this accessibility checklist. This checklist is intended as a practical design support tool for use in early design phases of handheld products. A number of challenges and limitations are discussed as well.     

从UML顺序图生成状态图的一个方法

UML (Unified Modeling Language) is a visual modeling language used for specifying,visualizing,constructing,and documenting the artifacts of software systems by various diagrams.It has been widely accepted as a standard modeling language in both academic and industrial areas.UML sequence diagrams are mostly used in specifying system requirements.By representing interactions,which are arranged in time sequence,between the objects in a system,sequence diagrams can construct scenarios indicating the system‘‘s functions.A UML statechart diagram is a graph shows the sequences of states that an object or an interaction goes through during its life in response to received stimuli,together with its responses and actions.It‘‘s useful in the design stage of system development.This essay discusses the computer-aided transformation from sequence diagrams to statechart diagrams,which can offer strong support for the transfering from requirement analysis to system design in the software development process.With OCL (Object Control Language) semantic constrain,a transform algorithm is provided in the paper.And the differences with the related works are also mentioned.     

Fast convergence of inviscid fluid dynamic design problems

A new procedure for robust and efficient design optimization of inviscid flow problems has been developed and implemented on a wide variety of test problems. The methodology involves the use of an accurate flow solver to calculate the objective function and an approximate, dissipative flow solver, which is used only in the solution of the discrete quasi-time-dependent adjoint problem. The resulting design sensitivities are very robust even in the presence of noise or other non-smoothness associated with objective functions in many high-speed flow problems. The design problem is solved using what we term progressive optimization, whereby a sequence of a partially converged flow solution, followed by a partially converged adjoint solution followed by an optimization step is performed. This procedure is performed using a sequence of progressively finer grids for the solution of the flow field, while only using coarser grids for the adjoint equation solution.This approach has been tested on numerous inverse and direct (constrained) design problems involving two- and three-dimensional transonic nozzles and airfoils as well as supersonic blunt bodies. The methodology is shown to be robust and highly efficient, with a converged design optimization produced in no more than the amount of computational work to perform from 0.5 to 2.5 fine-mesh flow analyses.