关键词： Space robot   dynamics modeling   active control   Jourdain's velocity variation principle   computed torque control method  

摘要： With the development of space exploration, researches on space robot will cause more attentions. However, most existing researches about dynamics and control of space robot concern planar problem, and the effect of flexible panel on dynamics of the system is not considered. In this article, dynamics modeling and active control of a 6-DOF space robot with flexible panels are investigated. Dynamic model of the system is established based on the Jourdain's velocity variation principle and the single direction recursive construction method. The computed torque control method is used to design point-to-point active controller of the space robot. The validity of the dynamic model is verified through the comparison with ADAMS software;the effects of panel flexibility on the system performance and the active controller design are studied in detail. Simulation results indicate that the proposed model is effective to describe the dynamics of space robot;panel flexibility has large influence on the dynamic behavior of space robot;the designed controller can effectively make the robot reach a specified position and the elastic vibration of the panels may be suppressed simultaneously.

关键词： Intelligent robotics   Machine learning   Model-based reinforcement learning   Robot learning   Policy search   Transition models   Reward functions  

摘要： Reinforcement learning is an appealing approach for allowing robots to learn new tasks. Relevant literature reveals a plethora of methods, but at the same time makes clear the lack of implementations for dealing with real life challenges. Current expectations raise the demand for adaptable robots. We argue that, by employing model-based reinforcement learning, the-now limited-adaptability characteristics of robotic systems can be expanded. Also, model-based reinforcement learning exhibits advantages that makes it more applicable to real life use-cases compared to model-free methods. Thus, in this survey, model-based methods that have been applied in robotics are covered. We categorize them based on the derivation of an optimal policy, the definition of the returns function, the type of the transition model and the learned task. Finally, we discuss the applicability of model-based reinforcement learning approaches in new applications, taking into consideration the state of the art in both algorithms and hardware.

关键词： Cable-driven robot   Kinematics model   Dynamics model   Positioning accuracy   End-effector attachment  

摘要： This paper tackles the problem of improving the connection between the fixed frame and the end-effector of planar and spatial cable-driven robots. A new design concept is detailed, which consists in adding pulleys to the attachment between the cables and the end-effector. These reflective pulleys must have the same radius as the ones at the frame in order to compensate their geometry. Without this modification in the end-effector, the usual simplification of the point-to-point method used to model the connection between frame and end-effector leads to significant errors in the Kinematics and Dynamics of the system due to the fact that the geometry of the frame pulleys is disregarded. By adding the reflective pulleys in the end-effector, the equations of the Kinematics and Dynamics of the real system are equivalent to those of the point-to-point model, and therefore, this simplified method can be used without inherent errors. This solution may be of great importance for computational issues because it leads to codes that may run at real time. An analytical proof of the equivalence of both models is presented. Finally, experimental results have been conducted for both, planar and spatial cable-robots, in order to illustrate the advantages of using this novel design concept for the connection between the end-effector and the fixed frame. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Cable-driven parallel robots   Wheeled mobile robots   Non-holonomic constraints   Gibbs-Appel formula   Input-output feedback linearization   Trajectory planning  

摘要： In comparison to the conventional parallel robots, cable-driven parallel robots (CDPRs) have generally superior features such as simple production technology, low energy consumption, large workspace, high payload to moving weight ratio, and also low cost. On the other hand, a wheeled mobile robot (WMR) which is capable of covering a vast area can be used when no specific space is designated for the stationary accessories of a robot. In this paper, the integration of a CDPR with a WMR is proposed to overcome some of the issues related to each of these robots. The kinematic equations of the robot are presented. To derive the dynamic equations, Gibbs-Appel (G-A) formulation is used, which in contrary to the Lagrange formulation benefits from advantages of quasi-velocities over generalized coordinates as well as not requiring Lagrange multipliers. The dynamic equations of the two parts are coupled, and the interacting effects are observable from the governing equations. By considering non-holonomic wheels for the robot, internal dynamics appears in the equations. However, based on some conditions, the equations are input-output linearizable via a static feedback. The platform trajectory is designed based on the given end-effector trajectory. The effectiveness of the controller is shown through simulations and experimental tests.

关键词： MEMS   stress-driven   aluminum nitride   silicon nitride   piezoelectric   piezoresistive   tactile sensing   flow sensing  

摘要： The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, SixNy/Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described.

关键词： Discrete-time system   Neural networks   Robot manipulator   Adaptive control   Dynamics uncertainties  

摘要： In this paper, a novel optimal adaptive radial basis function neural network (RBFNN) control has been investigated for a class of multiple-input-multiple-output (MIMO) nonlinear robot manipulators with uncertain dynamics in discrete time. To facilitate digital implementations of the robot controller, a robot model in discrete time has been employed. A high order uncertain robot model is able to be transformed to a predictor form, and a feedback control system has been then developed without noncausal problem in discrete time. The controller has been designed by an adaptive neural network (NN) based on the feedback system. The adaptive RBFNN robot control system has been investigated by a critic RBFNN and an actor RBFNN to approximate a desired control and a strategic utility function, respectively. The rigorous Lyapunov analysis is used to establish uniformly ultimate boundedness (UUB) of closed-loop signals, and the high-quality dynamic performance against uncertainties and disturbances is obtained by appropriately selecting the controller parameters. Simulation studies validate that the proposed control scheme has performed better than other available methods currently, for robot manipulators.

关键词： loop structures   smart materials   smart textiles   soft morphing   soft robots  

摘要： A loop-linked structure, which is capable of morphing in various modes, including volumetric transformation, is developed based on knitting methods. Morphing flowers (a lily-like, a daffodil-like, gamopetalous, and a calla-like flower) are fabricated using loop patterning, and their blooming motion is demonstrated by controlling a current that selectively actuates the flowers petals.

关键词： micro and nanoscale devices   robotics   soft actuators  

摘要： This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer-to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

关键词： 清洗机器人   导管架   机器人动力学   运动规划   步态分析  

摘要： 针对海洋平台导管架结构的复杂性与工作环境的特殊性,研制了一种8自由度的海洋平台导管架清洗机器人,该清洗机器人具有沿导管架空间进行攀爬及定位功能,通过夹持机构携带高压水射流喷枪来实施对导管架的清洗。基于该清洗机器人的构型特征与机器人动力学原理,采用大功率关节分时单步驱动与小功率关节多轴联动相结合的控制策略,进行了机器人在导管架上的运动规划。利用Matlab语言对清洗机器人在导管架上的行走步态进行了仿真,详细分析了机器人在攀爬过程中各关节的扭矩与功率间的变化关系。

关键词： 可重构机器人   层序列数组   模块化动力学建模   牛顿-欧拉方法TP242.2  

摘要： 可重构模块化机器人系统具有单元模块种类多、结构复杂且构型种类多样等特点,由于每次重构其动力学方程随构型变化而发生改变,使得传统建模方法不适合直接应用到其建模过程中。针对这一问题,文章提出一种具有模块化思想的动力学模型自动生成方法。首先根据各模块的特点采用旋量理论建立单元模块运动学、动力学模型,然后利用层序列数组(Layer Sequence Array)对系统拓扑结构及构型信息进行表达,确定各模块之间的相互作用关系,并结合牛顿-欧拉公式给出了可重构机器人动力学自动生成算法。最后通过仿真计算验证建模方法的可行性和有效性。