Image-based control for cable-based robots

Some human robot interactive applications involved in tele-robotics, remote supervisory and unmanned systems require specific capabilities. This demand has promoted various interactive modes and high-level control techniques such as tele-manipulation, speech, vision, gesture, etc. Among these interactive modes, the image based control which is often named point and click control has proven to be the most appropriate one that offers multiple advantages. This mode consists of only and simply pointing in an appearing object of an image received from a remote site, to convert this click into a robot command towards the corresponding location in the real world space. This mode is suitable for remote applications, frees the human operator from being involved into the loop enabling him/her to use commands in the sense of click and forget. This paper presents, firstly, the design and the realization of an experimental planar cable-based robot constituted of four cables. Secondly, it presents the design and the implementation of a high-level image-based control. Some typical experiments which have been performed prove the simplicity and the effectiveness of the image-based control. Moreover, it opens perspectives for new applications with cable-based robots, particularity for rehabilitation applications.     

Real-time vergence control for binocular robots

In binocular systems,vergence is the process of adjusting the angle between the eyes (or cameras) so that both eyes are directed at the same world point. Its utility is most obvious for foveate systems such as the human visual system, but it is a useful strategy for nonfoveate binocular robots as well. Here, we discuss the vergence problem and outline a general approach to vergence control, consisting of a control loop driven by an algorithm that estimates the vergence error. As a case study, this approach is used to verge the eyes of the Rochester Robot in real time. Vergence error is estimated with the cepstral disparity filter. The cepstral filter is analyzed, and it is shown in this application to be equivalent to correlation with an adaptive prefilter; carrying this idea to its logical conclusion converts the cepstral filter into phase correlation. The demonstration system uses a PD controller in cascade with the error estimator. An efficient real-time implementation of the error estimator is discussed, and empirical measures of the performance of both the disparity estimator and the overall system are presented.     

Abstraction mechanisms for event control in program debugging

In the event-action model of interactions between the debugging system and the program being debugged, an event will occur on the evaluation of a conditional defined in terms of the program activity if the evaluation yields the value true, and an action is an operation performed by the debugging system on the occurrence of an event. This paper presents a set of mechanisms for expressing conditionals at different levels of abstraction. At the lowest level, the authors have the simple conditionals, which can be expressed in terms of the values of the program entities and of the execution of the program statements. Simple conditionals can be grouped to form higher-level compound conditionals, which can be expressed in terms of the state and flow histories. The paper shows that the proposed abstraction mechanisms are powerful tools for monitoring program activity. They adequately support different debugging techniques, and offer the user a considerable degree of control over the debugging experiment     

Design and control of tensegrity robots for locomotion

The static properties of tensegrity structures have been widely appreciated in civil engineering as the basis of extremely lightweight yet strong mechanical structures. However, the dynamic properties and their potential utility in the design of robots have been relatively unexplored. This paper introduces robots based on tensegrity structures, which demonstrate that the dynamics of such structures can be utilized for locomotion. Two tensegrity robots are presented: TR3, based on a triangular tensegrity prism with three struts, and TR4, based on a quadrilateral tensegrity prism with four struts. For each of these robots, simulation models are designed, and automatic design of controllers for forward locomotion are performed in simulation using evolutionary algorithms. The evolved controllers are shown to be able to produce static and dynamic gaits in both robots. A real-world tensegrity robot is then developed based on one of the simulation models as a proof of concept. The results demonstrate that tensegrity structures can provide the basis for lightweight, strong, and fault-tolerant robots with a potential for a variety of locomotor gaits.     

Design and control of mechanical hands for robots

This paper deals with connexions among researches on biomechanics and the design and realization of mechanical hands for robots. High complexity of systems may be reached by use of computer aided design techniques and by the optimized determination of parameters of models, which biomechanics may present to robot scientists and designers.     

Multiprocessor control system for industrial robots

This paper describes an advanced robot control system based on the three parallel processor boards. The controller has been designed as a general-purpose robot control system dedicated to controlling industrial robots with up to six degrees of freedom. The controller is based on a disk-oriented real-time operating system. The entire set of robot parameters can be monitored and changed by the user on-line. Source files, compilers, linkers and various utilities are provided as well.The main software layers include robot program interpreter, manipulator control facility, robot kinematics, dynamic feed-forward compensation, and digital servos. Basis, hand and joint coordinates are supported. Point-to-point and continuous path motions are provided. Digital and analog IO modules are included for synchronization with an environment. An acquisition system for monitoring and graphical presentation of robot coordinates, velocities and IO signals is provided. The paper ends with some experimental results for a six-degree of freedom robot.     

Gesture recognition for control of rehabilitation robots

This paper describes the development of a control user interface for a wheelchair-mounted manipulator for use by severely disabled persons. It explains the construction of the interface using tasks to define the user interface architecture. The prototype robot used several gesture recognition systems to achieve a level of usability better than other robots used for rehabilitation at the time. The use of neural networks and other procedures is evaluated. It outlines the experiments used to evaluate the user responses and draws conclusions about the effectiveness of the whole system. It demonstrates the possibility of control using a head mouse.

欠驱动机器人控制策略综述

欠驱动机器人是指独立控制输人量少于系统自由度的一类机器人,具有重量轻、成本低、能耗低等众多优点,目前已引起学者们的广泛关注,介绍了欠驱动机器人控制器设计的六类策略,分析了各类策略的应用及效果,如何将鲁棒控制与其它控制策略相结合,开发出更实用、性能更优越的控制策略,有待于进一步研究.     

HOJO-brain for motion control of robots and biological systems

The purpose of this research was to propose and develop a control method in the robotic and biomedical fields which is configured by a robotic/biological simulator, an analytical control frame which has phase sequences, sensory feedback, and an artificial central pattern generator (CPG) which is constructed by a recurrent neural network (RNN) and a genetic algorithm (GA). We call such a controller a “HOJO-brain”, which means a supplementary brain for motion control. We applied this method in the robotic and biomedical fields. In the robotic field, the HOJO-brain was applied to a 5-DOF legged-locomotion robot and a 32-DOF humanoid simulation model consisting of antagonistic muscles. In the biomedical field, it was applied to animals as the FES (functional electrical stimulation) controller. This FES control system with a HOJO-brain has the potential to give more effective and emergent motion control to severely physically handicapped people such as quadraplegics. With computer simulations and simple experiments using animals, we abtained performance indices which confirmed the fine adaptability and emergence for motion control. This work was presented, in part, at the Second International Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20, 1997     

Observer-based dynamic walking control for biped robots

This article presents a novel observer-based control system to achieve reactive motion generation for dynamic biped walking. The proposed approach combines a feedback controller with an online generated feet pattern to assure a stable gait. Using the desired speed of the robot, a preview control system derives the dynamics of the robot’s body, and thereby the trajectory of its center of mass, to ensure a zero moment point (ZMP) movement, which results in a stable execution of the calculated step pattern. Extending the control system by an observer, based on this knowledge and the measured sensor values, compensates for errors in the model parameters and disturbances encountering while walking.     

A path following control for unicycle robots

In this work we present a new path following control for unicycle robots that is applicable for almost all the possible desired paths and whose analysis is very straightforward. First we select the path following method that consists of two steps: choosing a “projection” that relates the actual posture to the desired path and imposing a “motion exigency” to ensure that the robot advances. A “projection” that considers all the error coordinates is selected and closed equations are obtained for it. The uniqueness projection is carefully analyzed and a necessary and sufficient condition is also presented. This condition shows that a slight bound on the curvature derivative of desired paths must be imposed to preserve uniqueness. It is remarkable that the selected path following is applicable for paths containing zero‐radius turns, a problem that has never been resolved as far as we know. In addition, an asymptotically stable control law is found using the closed form equation of the proposed path following and the second Lyapunov method. Finally, we show the behavior of the path following and the control law through several simulated and experimental results, using a computerized wheelchair built at our research facility. © 2001 John Wiley & Sons, Inc.     

Advanced methods for displays and remote control of robots

An in-depth evaluation of the usability and situation awareness performance of different displays and destination controls of robots are presented. In two experiments we evaluate the way information is presented to the operator and assess different means for controlling the robot. Our study compares three types of displays: a “blocks” display, a HUD (head-up display), and a radar display, and two types of controls: touch screen and hand gestures. The HUD demonstrated better performance when compared to the blocks display and was perceived to have greater usability compared to the radar display. The HUD was also found to be more useful when the operation of the robot was more difficult, i.e., when using the hand-gesture method. The experiments also pointed to the importance of using a wide viewing angle to minimize distortion and for easier coping with the difficulties of locating objects in the field of view margins. The touch screen was found to be superior in terms of both objective performance and its perceived usability. No differences were found between the displays and the controllers in terms of situation awareness. This research sheds light on the preferred display type and controlling method for operating robots from a distance, making it easier to cope with the challenges of operating such systems.     

Hybrid autonomous control for multi mobile robots

Reinforcement learning can be an adaptive and flexible control method for autonomous system. It does not need a priori knowledge; behaviors to accomplish given tasks are obtained automatically by repeating trial and error. However, with increasing complexity of the system, the learning costs are increased exponentially. Thus, application to complex systems, like a many redundant d.o.f. robot and multi-agent system, is very difficult. In the previous works in this field, applications were restricted to simple robots and small multi-agent systems, and because of restricted functions of the simple systems that have less redundancy, effectiveness of reinforcement learning is restricted. In our previous works, we had taken these problems into consideration and had proposed new reinforcement learning algorithm, 'Q-learning with dynamic structuring of exploration space based on GA (QDSEGA)'. Effectiveness of QDSEGA for redundant robots has been demonstrated using a 12-legged robot and a 50-link manipulator. However, previous works on QDSEGA were restricted to redundant robots and it was impossible to apply it to multi mobile robots. In this paper, we extend our previous work on QDSEGA by combining a rule-based distributed control and propose a hybrid autonomous control method for multi mobile robots. To demonstrate the effectiveness of the proposed method, simulations of a transportation task by 10 mobile robots are carried out. As a result, effective behaviors have been obtained.     

Sensor-based control systems for arc welding robots

Arc welding is one of the most important areas of application for industrial robots. In most manufacturing situations, uncertainties in dimensions of the part, geometry of the joint, and the welding process itself make the use of sensors essential to maintaining weld quality. In this paper three types of control systems for arc welding robots are described: (1) tracking systems for centering the weld puddle over the joint, (2) weld process controls for maintaining proper seam width and penetration, and (3) supervisory controls for sequencing welding operations. These control functions have been implemented successfully in production using a computer vision sensor integrated into the welding torch. Experimental results are presented demonstrating the capabilities of the system.     

Robust control laws for wheeled mobile robots

The paper deals with feedback control of wheeled mobile robots. The proposed controller is based on a tracking scheme where the real robot tracks a fictitious reference one with equivalent kinematical properties. A solution to the parking problem is derived from the basic tracking scheme by considering a reference vehicle which converges to the desired configuration. The goal achievement is analysed by the stability of the zero equilibrium point of the tracking state error. Simulation as well as experimental results illustrate these controllers' designs. Robustness with respect to errors in the state estimation is investigated. It is defined by the existence of a compact attractive domain around the zero error. A practical computation of such a domain is a result of this paper.     

非完整移动机器人的复合编队控制

主要研究了非完整自主机器人之间的队形保持和避障问题,提出了一种新的复合编队控制方法,该方法根据机器人的期望位置在其运动约束区域内外的不同,分别以一种灵活的反馈线性化算法和最优近似目标算法来建立控制规则,并提出了编队环境中存在静态障碍物时的队形控制策略,从而实现多机器人的稳定编队控制．该方法降低了传统线性反馈控制对编队初始误差范围的要求,并且解决了非完整机器人编队的避障问题．实验结果表明了该编队控制方法的可行性和有效性．     

Adaptive hybrid control strategies for constrained robots

The problem of adaptive hybrid controller design for constrained roots with the consideration of computational efficiency is addressed. Two efficient control schemes based, respectively, on Lagrange and Newton-Euler dynamics formulation are presented. Detailed analyses on tracking properties of joint positions, velocities, and constrained forces are derived for both the Lagrange approach and the Newton-Euler approach. Although control laws in these two approaches are developed independently, a tight connection between them is found, indicating a possible bridge between general adaptive approaches based, respectively, on the two dynamics formulations     

Reflexive stability control framework for humanoid robots

In this paper we propose a general control framework for ensuring stability of humanoid robots, determined through a normalized zero-moment-point (ZMP). The proposed method is based on the modified prioritized kinematic control, which allows smooth and continuous transition between priorities. This, as long as the selected criterion is met, allows arbitrary joint movement of a robot without any regard of the consequential movement of the ZMP. On the other hand, it constrains the movement when the criterion approaches a critical condition. The critical condition thus triggers a reflexive, subconscious behavior, which has a higher priority than the desired, conscious movement. The transition between the two is smooth and reversible. Furthermore, the switching is encapsulated in a single modified prioritized task control equation. We demonstrate the properties of the algorithm on two human-inspired robots developed in our laboratory; a human-inspired leg-robot used for imitating human movement and a skiing robot.     

非完整移动机器人全局路径跟踪控制

根据制导路径跟踪理论,提出了一种非完整移动机器人全局路径跟踪控制方法.这一方法首先在路径坐标系上计算实际位置与期望位置的误差,利用制导的路径跟踪理论,导出消除该误差所需的姿态角和路径参数更新律,然后据此求解角速度及实际控制.文中还给出了初始路径参考点的计算方法,分析了路径跟踪方向和反转方法.稳定性分析证明该方法没有控制奇异点,受控闭环系统全局一致渐近稳定.最后通过移动机器人典型路径跟踪实验验证了所提出方法的可行性.