Simple rotary crane dynamics modeling and open-loop control for residual load sway suppression by only horizontal boom motion

To suppress two-dimensional load sway caused by the horizontal boom motion of a rotary crane, both horizontal and vertical boom motions are generally used. However, it would be more energy efficient and safer if a control scheme using only horizontal boom motion could be developed, eliminating the need for any boom vertical motion. In addition, if we can suppress load sway without the need to measure it, cost reduction of sensors can be achieved. Furthermore, the use of simple velocity trajectory patterns such as a trapezoidal velocity pattern and an S-curve acceleration/deceleration pattern, which are widely used in industrial automation systems, may provide cost-effective implementation of controllers. This paper presents a simple model of rotary crane dynamics that includes only significant centrifugal and Coriolis force terms. This simple model allows analytical solutions of the differential equations of the model to be derived. Thus, S-curve trajectory that considers residual vibration suppression without sensing it, using only horizontal boom motion, can be generated by solving only algebraic equations numerically. The effectiveness of the proposed method is demonstrated by numerical simulations and experimental results.     

Robust control of rotary crane by partial-state feedback with integrator

This paper deals with a simple design of robust control systems for rotary cranes. After deriving a simple linear model of crane dynamics, a constant gain partial state feedback controller is presented. Using information on the nominal natural frequencies of a load–rope system, the control system can be designed easily to be robustly stable for any rope length, without iterative computations. In addition, a method of including an integrator in the robust control system is proposed for reducing the positional error of the crane boom. The effectiveness of the proposed method is confirmed experimentally.     

Anti-swing control of a hydraulic loader crane with a hanging load

In this paper, anti-swing control for a hydraulic loader crane is presented. The difference between hydraulic and electric cranes are discussed to show the challenges associated with hydraulic actuation. The hanging load dynamics and relevant kinematics of the crane are derived to create the 2-DOF anti-swing controller. The anti-swing controller is added to the electro-hydraulic motion controller via feedforward. A dynamic simulation model of the crane is made, and the control system is evaluated in simulations with a path controller in actuator space. Simulation results show significant reduction in the load swing angle during motion. Experiments are carried out to verify the performance of the anti-swing controller, showing good suppression of the payload angle in practice.     

An energy exchanging and dropping-based model-free output feedback crane control method

For the overhead crane control problem, velocity-related terms (corresponding to full-state feedback) are generally required in the designed control systems for damping injection to achieve (asymptotic) stability. However, it is known that velocity signals may be noisy or even unmeasurable. Also, most existing controllers require full or partial plant physical parameters like rope length or load mass. To resolve these issues, a model-free energy exchanging and dropping-based control law is proposed to achieve output (only position/swing-angle) feedback control for overhead cranes. We synthesize a total energy function, consisting of the (generalized) crane energy and the controller energy, to render it to achieve its (local) minimum at the desired equilibrium point. The proposed control law is dynamically generated by an artificial block-spring system, which exchanges energy with the crane dynamics and then drops the energy via an elegant dropping mechanism to gradually attenuate the total energy. The corresponding stability and convergence analysis is implemented using some Lyapunov-like analysis. Simulation and experimental results suggest the effectiveness and feasibility of the proposed method for crane control, in terms of rapid swing suppression, efficient trolley positioning, as well as increased robustness.     

Fixed-order gain-scheduling anti-sway control of overhead bridge cranes

Acceleration and deceleration in overhead cranes may induce undesirable load swinging, which is unsafe for the surrounding human operators. In this paper, it is shown that such oscillatory behavior depends on the length of the rope and thus a gain-scheduling control law is proposed to reduce such an effect. Specifically, to take into account the technological limits in the controller implementation, a fixed-order controller is tuned, by also enforcing robustness and performance constraints. The proposed strategy is experimentally tested on a real bridge crane and compared to a time-invariant solution.     

Data-based error compensation for georeferenced payload path tracking of automated tower cranes

In order to increase the productivity on construction sites, a current topic of research is the automation of the payload transport by tower cranes. Thereby, a key requirement is to ensure that the tower crane precisely tracks the planned paths and positions the payload at the specified target location. Most of the state-of-the-art tower crane controllers damp load sway while moving each driving system to its desired position. However, the path error also consists of bending displacements of the tower crane’s mechanical structure, observer errors, or sensor offsets once the crane hook position is considered in a fixed georeferenced construction site system. These errors have not been addressed in literature on tower cranes so far. This paper introduces an approach to reduce the path error of automated tower cranes without permanently integrating additional sensors. A regression model is derived for predicting the path error and a least absolute shrinkage and selection operator (LASSO) is used to select the most important features. The predicted error is then used to compute a compensating hook path such that the measured hook path matches the desired hook path. The effectiveness of the approach is experimentally validated utilizing a real large-scale tower crane showing a reduction of the path error of more than 50% and a position accuracy of less than 16 cm.     

Quadrotor path planning using A* search algorithm and minimum snap trajectory generation

In this study, we propose a practical path planning method that combines the A* search algorithm and minimum snap trajectory generation. The A* search algorithm determines a set of waypoints to avoid collisions with surrounding obstacles from a starting to a destination point. Only essential waypoints (waypoints necessary to generate smooth trajectories) are extracted from the waypoints determined by the A* search algorithm, and an appropriate time between two adjacent waypoints is allocated. The waypoints so determined are connected by a smooth minimum snap trajectory, a dynamically executable trajectory for the quadrotor. If the generated trajectory is invalid, we methodically determine when intermediate waypoints are needed and how to insert the points to modify the trajectory. We verified the performance of the proposed method by various simulation experiments and a real-world experiment in a forested outdoor environment.     

Space‐Time Warp Curve for Synthesizing Multi‐character Motions

This paper introduces a new motion‐synthesis technique for animating multiple characters. At a high level, we introduce a hub‐sub‐control‐point scheme that automatically generates many different spline curves from a user scribble. Then, each spline curve becomes a trajectory along which a 3D character moves. Based on the given curves, our algorithm synthesizes motions using a cyclic motion. In this process, space‐time warp curves, which are time‐warp curves, are embedded in the 3D environment to control the speed of the motions. Since the space‐time warp curve represents a trajectory over the time domain, it enables us to verify whether the trajectory causes any collisions between characters by simply checking whether two space‐time warp curves intersect. In addition, it is possible to edit space‐time warp curves at run time to change the speed of the characters. We use several experiments to demonstrate that the proposed algorithm can efficiently synthesize a group of character motions. Our method creates collision‐avoiding trajectories ten times faster than those created manually.     

Antisway Tracking Control of Overhead Cranes With System Uncertainty and Actuator Nonlinearity Using an Adaptive Fuzzy Sliding-Mode Control

An adaptive fuzzy sliding-mode control (AFSMC) is presented for the robust antisway trajectory tracking of overhead cranes subject to both system uncertainty and actuator nonlinearity. First, a fuzzy sliding-mode control (FSMC) law is designed for the antisway trajectory tracking of the nominal plant. In association with a conventional trajectory tracking control law, this FSMC law guarantees asymptotic stability as well as improved transient response of the load sway dynamics while the trolley tracking error dynamics is rendered uniformly asymptotically stable. Second, a fuzzy uncertainty observer is designed to cope with system uncertainty as well as actuator nonlinearity present in an actual plant, and it is incorporated with the FSMC law for the development of the AFSMC law. In addition to stability analysis, the robust performance of the proposed AFSMC law is verified via numerical simulations and experiments.      

Safe and Distributed Kinodynamic Replanning for Vehicular Networks

This work deals with the problem of planning collision-free motions for multiple communicating vehicles that operate in the same, partially-observable environment in real-time. A challenging aspect of this problem is how to utilize communication so that vehicles do not reach states from which collisions cannot be avoided due to second-order motion constraints. This paper initially shows how it is possible to provide theoretical safety guarantees with a priority-based coordination scheme. Safety means avoiding collisions with obstacles and between vehicles. This notion is also extended to include the retainment of a communication network when the vehicles operate as a networked team. The paper then progresses to extend this safety framework into a fully distributed communication protocol for real-time planning. The proposed algorithm integrates sampling-based motion planners with message-passing protocols for distributed constraint optimization. Each vehicle uses the motion planner to generate candidate feasible trajectories and the message-passing protocol for selecting a safe and compatible trajectory. The existence of such trajectories is guaranteed by the overall approach. The theoretical results have also been experimentally confirmed with a distributed simulator built on a cluster of processors and using applications such as coordinated exploration. Furthermore, experiments show that the distributed protocol has better scalability properties when compared against the priority-based scheme. Part of the material presented in this paper has appeared in two conference publications: “A Decentralized Planner that Guarantees the Safety of Communicating Vehicles with Complex Dynamics that Replan Online” at IROS 2007 and “A Distributed Protocol for Safe Real-Time Planning of Communicating Vehicles with Second-Order Dynamics” at ROBOCOMM 2007.     

基于块A*正交匹配追踪的多传感器数据联合重构算法

 针对A*正交匹配追踪(A*OMP)算法计算复杂高,且不能利用信号的结构稀疏性这一缺陷,该文提出了块A*OMP算法并将其用于解决分布式压缩感知中的信号联合重构问题。该算法用原子块取代单个原子作为搜索树中的节点,在计算路径代价时用搜索树中所有路径的最大长度取代信号的稀疏度。然后在块A*OMP算法的基础上,选择与残差矩阵投影误差最小的原子块作为新的节点,得到了一种用于解决MMV(Multiple Measurement Vector, MMV)问题的块A*OMP算法,并利用该算法对相邻区域内的多个传感器所测的温度信号进行了联合重构。实验结果表明,该算法的重构性能优于MMV正交匹配追踪(OMPMMV)算法。     

基于编码技术的塔吊防碰撞系统设计

现代建筑工地环境复杂、规模庞大、机械化程度日益增高。建筑塔吊的普遍、高密度使用日显广泛,塔吊的安全越显重要。然而在塔吊防碰撞仍主要依靠司机的人工操作,不仅影响了施工效率,更难以保证塔吊的安全运行。针对上述问题,这里研究了塔吊防碰撞的原理,并采用数字传感、嵌入式处理、远程监控等技术设计一种塔吊防碰撞系统,该系统能够对塔吊之间的碰撞及塔吊与建筑物之间的碰撞进行预警。     

基于混合蛙跳算法的移动机器人路径规划

针对移动机器人路径规划中算法搜索能力不强且易陷入停滞的问题,文中提出了一种基于混合蛙跳算法的移动机器人路径规划方法。首先利用蚁群算法在栅格地图中生成一定数量的路径,然后引入混合蛙跳算法,子群内进行Memetic进化,最坏青蛙根据与子群最优青蛙或全局最优青蛙的路径交点栅格进行路径更新,并对最终生成的最优路径进行优化处理,以消除不必要的拐点,保证机器人路径运行的安全性。二维环境下的仿真实验表明,提出的混合蛙跳算法能在有效避开障碍物的同时快速地规划出一条通往目标点的优化路径,且效果令人满意。     

变频抓斗起重机的PLC程序优化

抓斗在抓完料后的上升过程中,必然出现开闭绳与起升绳不同步现象,这是变频抓斗起重机的通病。本文将分析其产生的原因,通过引入变频器的频率与电流这两个变量,详细介绍编写自动追速程序的动作原理,并经过调试优化了起重机的PLC程序,从而达到减少变频器与钢丝绳的故障率的目的。同时也可作为抓斗起重机变频改造的一个参照样本。     

利用概率天气预报的通航飞行路径规划

为解决实际天气与天气预报不一致时根据确定性天气预报所规划飞行路径效益低的问题,提出一种利用以概率方式给出的天气预报,对通用航空飞行路径进行规划的方法。该方法利用由集合数值天气预报得到的概率天气预报信息,构建空域概率天气模型,使用分阶段飞行路径规划方法保障预期规划目标的实现,将飞行路径规划分解为多个阶段,除第一阶段外,从每个阶段的每个起始点出发都分别规划绕飞和穿越可能的危险天气区域两条不同的路径,各阶段的不同路径采用A*算法进行搜索,得到包含多条飞行路径的规划飞行路径集合。实验结果表明,在保证安全性的前提下,该方法规划的飞行路径与其他典型算法规划的飞行路径相比,在统计意义上的期望飞行距离显著减小。      

Design and motion planning of hydraulically driven leg for maximum height jumping

This paper presents an optimized design and motion planning method of a hydraulically driven leg for jumping. The knee joint range was enlarged, and the desired torque profile was achieved using a four-bar linkage. The dynamics of the robot were considered during the motion planning, and the optimal trajectory was obtained by linear programming. Simulations and experiments showed that the leg could jump 1 m under a load of 50 kg.     

Adaptive robust motion control of single-rod hydraulic actuators:theory and experiments

High-performance robust motion control of single-rod hydraulic actuators with constant unknown inertia load is considered. The two chambers of a single-rod actuator have different areas, so the dynamic equations describing the pressure changes in them cannot be combined into a single load pressure equation. This complicates controller design since it not only increases the system dimension but also brings in the stability issue of the added internal dynamics. A discontinuous projection-based adaptive robust controller (ARC) is constructed. The controller takes into account not only the effect of parameter variations coming from the inertia load and various hydraulic parameters but also the effect of hard-to-model nonlinearities such as uncompensated friction forces and external disturbances. It guarantees a prescribed output tracking transient performance and final tracking accuracy in general while achieving asymptotic output tracking in the presence of parametric uncertainties. In addition, the zero error dynamics for tracking any nonzero constant velocity trajectory is shown to be globally uniformly stable. Experimental results are obtained for the swing motion control of a hydraulic arm and verify the high-performance nature of the proposed strategy. In comparison to a state-of-the-art industrial motion controller, the proposed algorithm achieves more than a magnitude reduction of tracking errors. Furthermore, during the constant velocity portion of the motion, it reduces the tracking errors almost down to the measurement resolution level     

Space-Variant Restoration of Images Degraded by Camera Motion Blur

We examine the problem of restoration from multiple images degraded by camera motion blur. We consider scenes with significant depth variations resulting in space-variant blur. The proposed algorithm can be applied if the camera moves along an arbitrary curve parallel to the image plane, without any rotations. The knowledge of camera trajectory and camera parameters is not necessary. At the input, the user selects a region where depth variations are negligible. The algorithm belongs to the group of variational methods that estimate simultaneously a sharp image and a depth map, based on the minimization of a cost functional. To initialize the minimization, it uses an auxiliary window-based depth estimation algorithm. Feasibility of the algorithm is demonstrated by three experiments with real images.     

基于滑模预测的三维起重机防摆控制方法研究

为了使起重机安全、高效运行,同时为了减少附加设备,达到节能减排的目标,运用电子防摆控制方法的研究成了国内外学者广泛关注的课题。本文主要针对桥式起重机三维模型,利用滑模预测的方法来设计控制器,使用预测控制中的滚动优化和反馈校正方法来优化滑模轨迹的到达过程,以最终达到削弱抖振和增强鲁棒性的目的。仿真结果表明,该控制方法可以较好地对起重机系统的大、小车及负载的摆角进行控制,高效的消除起重机的摆动,达到了设计的预期目的。     

Adaptive coupling control for overhead crane systems

Due to the requirements of high positioning accuracy, small swing angle, short transportation time, and high safety, both motion and stabilization control for an overhead crane system becomes an interesting issue in the field of control technology development. Since the overhead crane system is subject to underactuation with respect to the load sway dynamics, it is very hard to manipulate the crane system in a desired manner, namely, gantry position tracking and sway angle stabilization. Hence, in this paper, a nonlinear control scheme incorporating parameter adaptive mechanism is devised to ensure the overall closed-loop system stability. By applying the designed controller, the position error will be driven to zero while the sway angle is rapidly damped to achieve swing stabilization. Stability proof of the overall system is given in terms of Lyapunov concept. To demonstrate the effectiveness of the proposed controller, results for both computer simulation and experiments are also shown.