Multi‐template approach to realize central pattern generators for artificial locomotion control

Biologically inspired control of artificial locomotion often makes use of the concept of central pattern generator (CPG), a network of neurons establishing the locomotion pattern within a lattice of neural activity. In this paper a new approach, based on cellular neural networks (CNNs), for the design of CPGs is presented. From a biological point of view this new approach includes an approximated chemical synapse realized and implemented in a CNN structure. This allows to extend the results, previously obtained with a reaction‐diffusion‐CNN (RD‐CNN) for the locomotion control of a hexapod robot, to a more general class of artificial CPGs in which the desired locomotion pattern and the switching among patterns are realized by means of a spatio‐temporal algorithm implemented in the same CNN structure. Copyright © 2002 John Wiley & Sons, Ltd.     

Gait control for redundant legged biped robot at constant velocity and constant height of the waist

In this paper, we propose a gait control method for redundant legged biped robot based on leg center of mass (COM) position control at constant velocity and constant height of the waist. The developed biped robot has redundant legs, which have four degrees of freedoms (DOFs) on each in the sagittal plane. The redundant DOF enables movement of its leg tip position and its leg COM position independently. Therefore, the proposed robot has structural capability to control the leg COM position for maintaining the projection of the total COM inside the support polygon without upper body motion. Such capability enables the stable static walk in the arbitrarily desired velocity and height of the waist motion. The validity of the proposed method for the static walk at constant velocity and constant height of the waist in the leg COM position control for redundant legged biped robot is confirmed by several results of simulation and experiment. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 51–59, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20357     

Robot vision with cellular neural networks: a practical implementation of new algorithms

Cellular neural networks (CNNs) are well suited for image processing due to the possibility of a parallel computation. In this paper, we present two algorithms for tracking and obstacle avoidance using CNNs. Furthermore, we show the implementation of an autonomous robot guided using only real‐time visual feedback; the image processing is performed entirely by a CNN system embedded in a digital signal processor (DSP). We successfully tested the two algorithms on this robot. Copyright © 2006 John Wiley & Sons, Ltd.     

两足辅助行走机器人步态控制

智能两足辅助行走机器人,可以辅助残疾人在复杂环境中进行仿人行走.介绍了该机器人的机构和控制系统硬件,在机器人系统的步态特性基础上建立了人机一体的运动模型.运用零力矩点（ZMP）理论规划了机器人的行走步态,提出了局部步态调整与人体主动补偿运动相结合的实时步态稳定性控制策略.通过仿真实验对该控制策略进行了验证和分析.     

Formation control of multiple nonholonomic mobile robots

Tracking control problem of multiple mobile robots is considered. Our system is composed of a reference and follower robots of unicycle type. The robots are assumed to satisfy pure rolling and nonslipping conditions, which lead to nonholonomic constraints. The purpose is to control the followers so that the reference is tracked with arbitrary desired clearance and also to avoid interrobot collisions. To accomplish this goal, we first introduced a virtual robot (VR) tracking control to establish and maintain the formation when no collision is detected. VR is an ideal robot fixed with each follower and helps in simplifying the control, as the tracking error becomes zero in the final stage. During the process, if the possibility of collision is detected, a collision avoidance technique (l?ψ or l?l control) will be applied to the lower priority robot. The result of this control gives a monotonic convergence in an internal shape of distance variables, which enables us to predict the movement of the robots during this control and leads to collision‐free movement. These processes are repeated until the desired motion is accomplished. Simulation results prove the efficiency of our control techniques. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(3): 81–88, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20192 Copyright © 2006 Wiley Periodicals, Inc.     

Walking planning based on artificial vector field with prediction simulation for biped robot

This paper proposes a method for gait trajectory generation using an artificial vector field for stable walking for a biped robot. The tip of the robot while walking can often deviate from the desired trajectory as a result of the disturbances forced by unexpected outside factors. In our approach, though no prepared trajectory is specified a priori, the tip follows the artificial vectors designed in the workspace. Moreover, the prediction simulation is performed online. The simulator judges the stability under comparison with the present state and the prediction results, and then the gait parameters are adaptively improved in feedforward for the stable walk. The numerical and physical experimental results show the validity of the proposed method in a continuous walk. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 54– 61, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20547     

多运动方式移动机器人控制系统设计

为了实现适合于多运动方式移动机器人的分布式运动控制系统,在四足机器人控制系统总体设计方案的基础上,采用自下而上的设计思想设计了控制系统各功能模块,即伺服控制模块、协调控制模块和通信接口模块,并在多运动方式四足机器人试验平台上进行了验证。试验结果表明,整个控制系统结构灵活、功能强大、工作稳定可靠,提高了机器人的运动性能。     

The Development of Two Mobile Gait Rehabilitation Systems

The ability to walk without the help of a caretaker enhances the quality of life for those who are bed-ridden or confined to a wheelchair. At present, most of the available gait rehabilitation robot systems have been designed to support the body weight externally. For gait training to be effective, a mobile body weight support (BWS) mechanism is needed. In mobile gait training robot systems, functions such as patient path following and constant BWS are important issues, particularly in dynamic environments. In the present study, two types of robotic systems were developed for gait rehabilitation. The first is known as the mobile manipulator type and the second the mobile vehicle type. The differences between the two systems in design and control are discussed. A control algorithm based on a neural network was used to compensate for dynamic interactions, unmodeled dynamics, and disturbances by the user on the system. Both electrical and pneumatic BWS mechanisms were built and compared. The proposed BWS systems were tested experimentally for their effectiveness in gait rehabilitation while maximizing the therapeutic outcome.     

A new blind source separation method based on fractional lower‐order statistics

We proposed neural network structures related to multilayer feed‐forward networks for performing blind source separation (BSS) based on fractional lower‐order statistics. As alpha stable distribution process has no its second‐ or higher‐order statistics, we modified conventional BSS algorithms so that their capabilities are greatly improved under both Gaussian and lower‐order alpha stable distribution noise environments. We analysed the performances of the new algorithm, including the stability and convergence performance. The analysis is based on the assumption that the additive noise can be modelled as alpha stable process. The simulation experiments and analysis show that the proposed class of networks and algorithms is more robust than second‐order‐statistics‐based algorithm. Copyright © 2006 John Wiley & Sons, Ltd.     

Autonomous mobile robot based on behavior decision skill and control skill of the operator

This paper introduces a human skill base control algorithm using artificial neural networks and fuzzy reasoning for an autonomous mobile robot. Neural networks are used to select a suitable motion control pattern in actual environments. The back propagation algorithm adjusts the weights of the neural networks so that the selected motion control pattern corresponds to the action, which is obtained by the operator's behavior decision skill. To realize the selected motion control pattern, the orientation angle and the speed of the mobile robot are determined by fuzzy reasoning in which fuzzy rules are also automatically tuned so as to simulate the operator's control skill. We have implemented and tested the proposed control algorithm on an autonomous mobile robot and some experimental results demonstrate the effectiveness of the proposed control algorithm for the autonomous mobile robot. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 30–39, 2000     

Dynamical adaptive synchronization

The notions of dynamical synchronization and adaptive dynamical synchronization problems are introduced. The algorithm solving adaptive synchronization problem for a subclass of Lurie systems with exciting input is proposed. The performance and potentialities of proposed solutions are demonstrated by two examples related to formation control and self‐organization of swarm systems. Copyright © 2006 John Wiley & Sons, Ltd.     

Biologically Inspired Cooperative Routing for Wireless Mobile Sensor Networks

Biological systems present remarkable adaptation, reliability, and robustness in various environments, even under hostility. Most of them are controlled by the individuals in a distributed and self-organized way. These biological mechanisms provide useful resources for designing the dynamical and adaptive routing schemes of wireless mobile sensor networks, in which the individual nodes should ideally operate without central control. This paper investigates crucial biologically inspired mechanisms and the associated techniques for resolving routing in wireless sensor networks, including Ant-based and genetic approaches. Furthermore, the principal contributions of this paper are as follows. We present a mathematical theory of the biological computations in the context of sensor networks; we further present a generalized routing framework in sensor networks by diffusing different modes of biological computations using Ant-based and genetic approaches; finally, an overview of several emerging research directions are addressed within the new biologically computational framework.     

Development of Sensor and Control Systems of a Wearable Robot to Walk on a Step

The goal of our study is to develop a system for walking on a step using a wearable robot. Our system consists of (1) sensing of a step from the movement of the walker, (2) detection of the foot placement state related to the step, and (3) generation of gait patterns of climbing and stepping down for the step. In the generation of gait patterns for the step, toe trajectories are generated according to the height of the step to avoid collision of the swinging leg with the step. The hip trajectory is generated by an optimization technique that minimizes the sum of the joint angular jerk of the robot subject to constraints on the hip position and the velocity at toe liftoff. Each joint angle trajectory is calculated from the generated trajectories by means of inverse kinematic equations. We investigated the feasibility of the proposed sensor and control systems for two steps with different heights.     

Adaptive motion/force tracking control of holonomic constrained mechanical systems: a unified viewpoint

This paper proposes a robust adaptive motion/force tracking controller for holonomic constrained mechanical systems with parametric uncertainties and disturbances. First, two types of well‐known holonomic systems are reformulated as a unified control model. Based on the unified control model, an adaptive scheme is then developed in the presence of pure parametric uncertainty. The proposed controller guarantees asymptotic motion and force tracking without the need of extra conditions. Next, when considering external disturbances, control gains are designed by solving a linear matrix inequality (LMI) problem to achieve prescribed robust performance criterion. Indeed, arbitrary disturbance/parametric error attenuation with respect to both motion and force errors along with control input penalty are ensured in the L₂‐gain sense. Finally, applications are carried out on a two‐link constrained robot and two planar robots transporting a common object. Numerical simulation results show the expected performances. Copyright © 2006 John Wiley & Sons, Ltd.     

Study on voltage regulation methods for distribution systems with dispersed generators

Connection of a large number of the dispersed generators to distribution networks is not easy due to various technical considerations. Thus, we have been trying to devise a concept for future electrical distribution systems with many dispersed generators. In this work, it has been considered that each customer's load and each generator's active and reactive power should be controlled in order to stabilize and optimize the networks. Under this consideration, two control methods for future distribution systems are proposed, a cooperative control and an independent control. We have confirmed experimentally that the voltage regulation ability is higher with the cooperative control than with the independent control, especially in cases of an eccentric load profile in a feeder and a heavy load. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 154(4): 16–23, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20246     

Design of impulsive adaptive observers for improvement of persistency of excitation

The development of adaptive observer techniques for nonlinear systems in the output canonical form is proposed applying additional impulsive feedback in the observer equations. The stability of new impulsive adaptive observer is investigated. It is shown that under some conditions, the proposed impulsive feedback can improve the rate of the observer convergence or relax the requirement on persistency of excitation, which is usually introduced to ensure convergence of the parameter estimates. The proposed feasibility conditions include positivity of dwell time (boundedness of impulse frequency) and solvability of some Lyapunov‐like matrix inequalities. The results are illustrated by simulation for three examples (including a single link flexible joint robot example). Copyright © 2014 John Wiley & Sons, Ltd.     

Control using joint torque sensor of robot arm with two‐inertia resonance: Comparison with control using state‐estimation observer

Most industrial robots are driven through reduction gears such as Harmonic Drives and RV gears. Due to the flexibility of the drive system, vibratory behavior occurs during operation. When flexibility is considered, the drive system of the robot joint can be modeled as a resonant mechanical system called a two‐inertia system. Conventionally, studies of two‐inertia system have discussed semiclosed‐loop control using only motor information and a state observer. On the other hand, joint torque sensing of robots has been studied in the harmonic drives that are widely used in robot joints. The joint torque sensor is becoming available with higher performance. In this paper, we consider the control of a robot arm having two‐inertia resonance by using the joint torque sensor. The performance of the torque sensor and that of the observer are compared. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(2): 75–84, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20226     

Current‐input current‐output analog half center oscillator and central pattern generator circuits with memristors

The comparison of the memristor to the biological synapse has motivated the introduction of memristors to biomimetic circuits such as Central Pattern Generators (CPGs) and Half Center Oscillators (HCOs). The effects of the utilization of memristors in such systems have been investigated in this work. The HCO is a neural oscillator, and the CPG is made up of 4 HCOs producing oscillations corresponding to the locomotion of a 4‐limbed animal. Analog HCO and CPG circuits have been simulated using the Cadence Virtuoso platform and effects of using current‐driven and voltage‐driven memristors in different configurations with different parameters have been analyzed. Improvement in the stability of rhythm and variations in oscillation amplitudes have been observed.     

A class of adaptive regulators for robot manipulators

In this paper we propose a framework to adaptive regulator design of robot manipulators. A class of global regulators for robot is characterized for which we provide guidelines to derive adaptive versions. The class of regulators is described by control laws comprising the gradient of an artificial potential energy depending in a linear manner on the robot and payload unknown parameters plus a linear velocity feedback. We provide explicit sufficient conditions on the artificial potential energy which allow to obtain an adaptive regulator which yields a stable closed-loop system and global positioning. Using this framework we revise two previously proposed adaptive regulators and we suggest two new ones. © 1998 John Wiley & Sons, Ltd.     

A generalized global adaptive tracking control scheme for robot manipulators with bounded inputs

In this work, a generalized adaptive scheme for the global motion control of robot manipulators with constrained inputs is proposed. It gives rise to various families of bounded adaptive controllers defined through a general class of saturation functions. Compared with adaptive tracking control algorithms previously developed in a bounded input context, the proposed adaptive approach guarantees the motion control objective for any initial condition, avoiding discontinuities throughout the scheme, preventing the inputs to reach their natural saturation bounds, and permitting innovation on the saturating structure through its generalized form, giving a wide range of possibilities for performance improvement. Experimental results corroborate the efficiency of the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd.