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.     

基于T—S模型的旋转式起重机稳钩保性能控制

基于T-S模型的保性能控制对控制带有不确定性系统（如旋转式起重机稳钩系统）有很好的鲁棒性,把系统可稳和保性能控制转化为解一系列矩阵不等式（LMI）的问题,得出最优的反馈矩阵,设计出基于T-S模型的最优保性能控制器,并对这种方法进行了仿真。结果表明,这种方法简单可行,并且具有很好的鲁棒性。     

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     

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 integral robust control of hydraulic systems with asymptotic tracking

In this paper, an adaptive integral robust controller is developed for high accuracy motion tracking control of a double-rod hydraulic actuator. We take unknown constant parameters including the load and hydraulic parameters, and lumped unmodeled disturbances in inertia load dynamics and pressure dynamics into consideration. A discontinuous projection-based adaptive control law is constructed to handle parametric uncertainties, and an integral of the sign of the extended error based robust feedback term to attenuate unmodeled disturbances. Moreover, the present controller does not require a priori knowledge on the bounds of the lumped disturbances and the gain of the designed robust control law can be tuned itself. The major feature of the proposed full state controller is that it can theoretically guarantee global asymptotic tracking performance with a continuous control input, in the presence of various parametric uncertainties and unmodeled disturbances such as unmodeled dynamics as well as external disturbances via Lyapunov analysis. Comparative experimental results are obtained for motion control of a double-rod hydraulic actuator and verify the high-performance nature of the proposed control strategy.     

Enhancing Design of Visual-Servo Delayed System

A robust adaptive predictor is proposed to solve the time-varying and delay control problem of an overhead crane system with a stereo-vision servo. The predictor is based on the use of a recurrent neural network (RNN) with tapped delays, and is used to supply the real-time signal of the swing angle. There are two types of discrete-time controllers under investigation, i.e., the proportional-integral-derivative (PID) controller and the sliding controller. Firstly, a design principle of the neural predictor is developed to guarantee the convergence of its swing angle estimation. Then, an improved version of the particle swarm optimization algorithm, the parallel particle swarm optimization (PPSO) method is used to optimize the control parameters of these two types of controllers. Finally, a homemade overhead crane system equipped with the Kinect sensor for the visual servo is used to verify the proposed scheme. Experimental results demonstrate the effectiveness of the approach, which also show the parameter convergence in the predictor.     

Fuzzy motion control of an auto-warehousing crane system

Fuzzy motion control of an auto-warehousing crane system is presented in this paper. Using the concept of linguistic variable, a fuzzy logic controller (FLC) can convert the knowledge and experience of an expert into an automatic control strategy. The designed FLC with a rule base and three sets of parameters is used to control the crane system in x, y, and z directions. The unloaded weight and the fully loaded weight of the crane system in discussion are 1.35×10⁴ kg and 1.5×10⁴ kg, respectively. For various loading conditions and varying distances, the FLC still controls the crane system very well with positioning accuracy less than 2×10 ^-3 m for all directions. The distance-speed reference curve for control of the crane system is designed to meet the engineering specifications of motion such as acceleration, deceleration, maximum speed, and creep speed in each direction, and is generated automatically according to varying distance. The method for designing the distance-speed reference curve can make the crane move at relatively high speed to approach the target position. Simulations of the motion control in the three directions are demonstrated     

Adaptive Fuzzy Controller of the Overhead Cranes With Nonlinear Disturbance

Overhead cranes are common industrial structures that are used in many factories and harbors. They are usually operated manually or by some conventional control methods, such as the optimal and PLC-based methods. The theme of this paper is to provide an effective all-purpose adaptive fuzzy controller for the crane. This proposed method does not need the complex dynamic model of the crane system, but it uses trolley position and swing angle information instead to design the fuzzy controller. An adaptive algorithm is provided to tune the free parameters in the crane control system. The ways to speed the transportation and reduce the computational efforts are also given. Therefore, the designing procedure of the proposed controller will be very easy. External disturbance, such as the wind and the hit, which always deteriorates the control performance, is also discussed in this paper to verify the robustness of the proposed adaptive fuzzy algorithm. At last, several experimental results with different wire length and payload weight compare the feasibility and effectiveness of the proposed scheme with conventional methods     

Trajectory generation of rotary cranes based on A* algorithm and time-optimization for obstacle avoidance and load-sway suppression

Rotary cranes are widely utilized for cargo handling of heavy objects in various construction sites by synchronizing two-dimensional boom rotations and rope motion. The crane’s motion is accompanied by undesirable load-sway and constrained by obstacles, which influence the crane motion and may cause collisions and accidents. Therefore, safe and fast motion for rotary cranes are a main demand for reducing operation time and suppressing residual load-sway. Moreover, avoiding collisions is highly required to guarantee safety during load transportation, while sudden acceleration/deceleration motions are basically prohibited. This paper proposes an optimal trajectory generation method for a large crane using a simple nonlinear dynamics to enhance load-sway suppression without collisions. The three-dimensional crane trajectory is generated by two different algorithms; the first one is the A* algorithm, which is used to generate a short-distance load path from a starting position to the destination with avoiding collision with not only the loads but also the crane body and the rope. Using the inverse kinematics of the crane, the shortest-distance paths for boom rotations and rope motion can be determined. The second algorithm is applied to obtain a time-optimal trajectory for the paths generated by the A* algorithm under crane dynamics and load-sway constraints. The proposed trajectory is represented by a polynomial function, which provides practical and smooth motion for the crane. Computational and experimental results confirm the effectiveness of the proposed approach for suppressing residual load-sway and obstacle avoidance.     

A novel pitch control system for a wind turbine driven by a variable-speed pump-controlled hydraulic servo system

The paper aims to develop a novel pitch control system for a large wind turbine driven by a variable-speed pump-controlled hydraulic servo system. To perform practical pitch control experiments, a full-scale test rig of the hydraulic pitch control system for a 2 MW wind turbine’s blade, including a novel pitch control mechanism, a variable-speed pump-controlled hydraulic servo system, a disturbance system and a PC-based control system, is designed and set up. The variable-speed pump-controlled hydraulic servo system, containing an AC servo motor, a constant displacement hydraulic piston pump two differential hydraulic cylinders and hydraulic circuits, achieved high response and high energy efficiency, so it is suitable for wind turbine applications. Besides, to implement the pitch control in the proposed novel pitch control system, an adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation (AFC-STFSMC) is developed to design the pitch controller. Finally, the developed variable-speed pump-controlled hydraulic servo system was built and verified for the path tracking control and path-positioning control of the pitch control of the wind turbines by practical experiments in a full-scale test rig under different path profiles, load torques, and random wind speeds.     

Sensorless load angle control for two-phase hybrid stepper motors

The widely used full-step open-loop stepping motor drive algorithms are characterised by a low torque/power ratio, large torque ripple and resonance problems. In order to use stepping motors in more demanding applications, closed-loop control is needed. In this paper, a previously described load angle estimation algorithm, solely based on voltage and current measurements, is used to provide the necessary feedback without using a mechanical position sensor. This paper introduces a novel closed-loop load angle controller which optimises the current level based on the estimated load angle. This approach is challenging as the current - load angle dynamics are highly nonlinear. However, in this research a linear model is proposed and used to tune a PI load angle controller. The controller reduces the current level to obtain the optimal load angle but does not change the way stepping-motor are driven by step command pulses. This results in a broad industrial employability of these algorithms. The proposed sensorless controller is validated trough both simulations and measurements.     

Advanced control of induction motor based on load angle estimation

An advanced control system with load angle adjustment is introduced. The method is based on the action of a phase-locked loop, in which a position synchronization of two vectors to obtain a constant command angle between them is realized. In the system presented, the vectors are stator current and rotor flux. The load angle is kept constant by changing the position of stator current vector as a result of tuning its pulsation. Proportional-integral and fuzzy logic controllers are used to control the load angle. Because of using the load angle controller and simple relations for state variables, the proposed idea does not require exact speed measurement. The discussed control system is not sensitive to motor resistance variations. This idea is realized on a fixed-point digital signal processor and field-programmable gate arrays. Experimental results for the control system fed by a voltage-source inverter and controlled using a predictive current controller are presented.     

Payload trajectory tracking of a 5-DOF tower crane with a varying-length hoist cable: A passivity-based adaptive control approach

This paper presents a passivity-based adaptive control method for a 5 degree-of-freedom (DOF) tower crane that guarantees robust payload trajectory tracking. The 5-DOF tower crane system considered in this work features three actuated degrees of freedom (including a varying-length hoist cable) and two unactuated degrees of freedom in the hoist cable sway. The proposed controller includes an adaptive feedforward-like control input that is used to ensure that the tower crane features an output strictly passive input–output mapping. The Passivity Theorem is invoked to guarantee closed-loop input–output stability for any output strictly passive negative feedback controller. A novel approach is developed to bound the time derivative of the system’s mass matrix, which is a critical aspect of the proof of passivity. Experimental tests are performed, which demonstrate the effectiveness of the control law on a small-scale three-dimensional tower crane.     

A low-cost driving simulator for full vehicle dynamics simulation

This paper describes the construction of a low-cost PC-based driving simulator that can perform five degree-of-freedom (DOF) motions similar to a road vehicle. The mathematical equations of vehicle dynamics are first derived from the 2-DOF bicycle model and incorporated with the tire, steering, and suspension subsystems. The equations of motion are then programmed by MATLAB, transferred into C++ code in the MIDEVA environment, and further developed into a motion platform control program by C++Builder. To achieve the simulator functions, a motion platform that is constructed by five hydraulic cylinders is designed, and its kinetics/inverse kinetics analysis is also conducted. Driver operation signals such as steering wheel angle, accelerator pedal, and brake pedal positions are measured to trigger the vehicle dynamics calculation and further actuate the cylinders by the motion platform control program. In addition, a digital PID controller is added to achieve the stable and accurate displacements of the motion platform. The experiments prove that the designed simulator is adequate in performing some special road driving situations discussed in this paper.     

Nonlinear coupling control laws for an underactuated overhead crane system

In this paper, we consider the regulation control problem for an underactuated overhead crane system. Motivated by recent passivity-based controllers for underactuated systems, we design several controllers that asymptotically regulate the planar gantry position and the payload angle. Specifically, utilizing LaSalle's invariant set theorem, we first illustrate how a simple proportional-derivative (PD) controller can be utilized to asymptotically regulate the overhead crane system. Motivated by the desire to achieve improved transient performance, we then present two nonlinear controllers that increase the coupling between the planar gantry position and the payload angle. Experimental results are provided to illustrate the improved performance of the nonlinear controllers over the simple PD controller.     

基于嵌入式的智能塔吊远程控制系统的设计

为提高塔吊操作的可靠性与安全性,解决操作人员高空作业问题,实现塔吊的远程智能化控制,借助于嵌入式技术,研究设计一个基于嵌入式的智能塔吊远程控制系统。系统分为处理器和无线控制器两部分,通过无线控制器中的PC机向塔吊操作人员显示塔机实时运行情况及工作参数等信息,同时位于塔吊上的处理器接收控制器发出的动作指令,通过驱动接口电路控制塔吊的运行。塔吊操作人员远离现场,施工作业的安全性和自动化都得到了极大地提高,减少安全事故发生。     

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.     

A Motor Control Strategy With Virtual Musculoskeletal Systems for Compliant Anthropomorphic Robots

This paper presents a full-body compliant motor control strategy with a virtual musculoskeletal system for anthropomorphic robots. This integrates a task-space control module and a joint stiffness control module on joint torque control implementation. The passivity-based task-space controller manages the Cartesian forces and provides the robot with full-body compliance and balancing ability, and the joint stiffness controller locally stabilizes the desired posture trajectories. We discuss the advantage of the proposed strategy from two practical computational points of view: computational cost in the postural maintenance and redundancy resolution to suppress the internal motions. The implementation issues of the torque controller with hydraulic actuators are also discussed. The effectiveness of the proposed method is empirically validated by four kinds of full-body motion control experiments on our hydraulic biped anthropomorphic robot.      

起重机轨道检测机器人激光姿态角变结构双闭环控制研究

针对起重机轨道检测机器人上的激光姿态角自动调节系统采用经典PID控制效果不佳,无法满足轨道检测要求的问题,提出采用滑膜变结构双闭环的控制方法。文中建立了激光姿态角自动调节系统的数学模型,基于指数趋近律的方法设计了滑膜变结构控制器,并搭建轨道检测机器人及其激光姿态角调节系统。通过仿真研究可知,滑膜变结构控制下激光姿态角调节的时间比PID控制下快0.11 s,超调量减小了0.3%,且运动平稳。仿真试验研究结果为起重机轨道检测机器人的研发与应用提供了依据。     

Transputer control of hydraulic actuators and robots

The paper reports and discusses results from a Danish mechatronic research program focusing on intelligent actuators for intelligent motion control. A mechatronic test facility with a transputer controlled hydraulic robot suitable for real-time experimentation and evaluation of control laws and algorithms is described. Concepts of intelligent motion control and intelligent hydraulic actuators are proposed. Promising experimental path-tracking results obtained from model-based adaptive control algorithms are presented and discussed. The experiments confirm that transputers have significant advantages in intelligent control of actuators and robots for high-speed and high-precision tasks. Further, research on learning controllers and hybrid controller architecture, including real-time switching between control algorithms, benefits from applying transputer technology