面向精密调整的6-HTRT并联机器人

为实现光学精密调整,研制出了由交流伺服电机驱动的6-HTRT并联机器人,它具有6个自由度,其结构特点决定了该机器人可以完成高精度定位调整。分析了机器人的位置逆解,并对不同位姿下的工作空间进行了仿真。控制系统采用基于ISA总线的闭环控制方式,测试结果显示:该并联机器人工作空间较大、分辨率高、重复定位精度高,说明机器人结构和控制系统设计的合理性。最后应用此并联机器人成功完成了光学精密装配试验。     

A new revolute robot manipulator adapting the closed‐chain mechanism

Conventional robot manipulators actuated by motors with conventional speed reducers such as the harmonic drive or RV have weakness in the load capacity since the speed reducers are not stiff enough. To overcome this, we propose a four‐bar‐link actuator driven by the ball screw, which has a high stiffness and high torque transmission ability, and propose a new type of four degree‐of‐freedom revolute robot manipulator adapting the proposed actuators. The base joint of the robot is actuated by the motor with the conventional speed reducer, and the other joints are actuated by the proposed actuators. The kinematics and dynamics of the robot are analyzed in the joint coordinate and in the Cartesian coordinate. For the performance tests of the robot, a four degree‐of‐freedom revolute robot was built. Through the performance tests, the results of superior load capacity and positioning accuracy are presented. © 2005 Wiley Periodicals, Inc.     

TriM: An Ultra-Accurate High-Speed Six Degree-of-Freedom Manipulator Using Planar Stepper Motors

In this paper, we propose a novel six degree-of-freedom positioning system. This mechanism is a tripod structure with inextensible limbs actuated at the base by two-dimensional linear stepper motors (other types of actuators may also be utilized). This manipulator has a closed-chain kinematic structure. Both the direct and the inverse kinematics of the manipulator are presented in detail. While the inverse kinematics are obtained in closed form, the direct kinematics can not be solved in closed form and an algorithm is provided for numerically computing the direct kinematic solution. A detailed dynamic model of the positioning system is also provided. The dynamics of the actuators (Sawyer motors) are also included in the dynamic modeling. The design of the tripod manipulator (TriM) included a kinematic optimization of the system parameters to maximize the manipulator workspace. The proposed manipulator achieves large range of motion in all the 6 degrees of freedom. Furthermore, high resolution and high speed motion may be achieved in all axes due to the actuators used and the direct-drive nature of the manipulator. This work was supported in part by NSF under grants ECS-9977693 and ECS-0501539. An earlier version of this paper was presented at the 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems, Las Vegas, NV, Oct. 2003.     

Local input‐to‐state stabilization and ℓ ∞ ‐induced norm control of discrete‐time quadratic systems

This paper addresses the problems of local stabilization and control of open‐loop unstable discrete‐time quadratic systems subject to persistent magnitude bounded disturbances and actuator saturation. Firstly, for some polytopic region of the state‐space containing the origin, a method is derived to design a static nonlinear state feedback control law that achieves local input‐to‐state stabilization with a guaranteed stability region under nonzero initial conditions and persistent bounded disturbances. Secondly, the stabilization method is extended to deliver an optimized upper bound on the ? _∞ ‐induced norm of the closed‐loop system for a given set of persistent bounded disturbances. Thirdly, the stabilization and ? _∞ designs are adapted to cope with actuator saturation by means of a generalized sector bound constraint. The proposed controller designs are tailored via a finite set of state‐dependent linear matrix inequalities. Numerical examples are presented to illustrate the potentials of the proposed control design methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Robust control under worst‐case uncertainty for unknown nonlinear systems using modified reinforcement learning

Reinforcement learning (RL) is an effective method for the design of robust controllers of unknown nonlinear systems. Normal RLs for robust control, such as actor‐critic (AC) algorithms, depend on the estimation accuracy. Uncertainty in the worst case requires a large state‐action space, this causes overestimation and computational problems. In this article, the RL method is modified with the k‐nearest neighbor and the double Q‐learning algorithm. The modified RL does not need the neural estimator as AC and can stabilize the unknown nonlinear system under the worst‐case uncertainty. The convergence property of the proposed RL method is analyzed. The simulations and the experimental results show that our modified RLs are much more robust compared with the classic controllers, such as the proportional‐integral‐derivative, the sliding mode, and the optimal linear quadratic regulator controllers.     

Swing‐Stabilization Up for a Rotatory‐Elastic Pendulum Via Nonlinear Sub‐Optimal Control

This paper deals with the smooth control design for Swing‐Stabilization Up of underactuated pendular robot. The considered system has, at least, two different no actuated links, one of them is pendular like elbow, the other one is prismatic and elastic. Thus, the control aim is to swing‐up and stabilize the underactuated system by using non‐switched control algorithm. To this, the control algorithm summarizes the concept of sub‐optimal control, the energy based control and the Kalman's canonical decomposition to unify the Swing‐Up and Stabilization of the considered underactuated system. In order to test the designed control algorithm, experimental results are presented for the non‐conventional rotatory elastic‐pendulum system.     

小型高可靠分体式多冗余线位移传感器研制

为了满足新型战略导弹武器的研制需求,要求伺服机构结构紧凑,集成度高,并能够适应恶劣的工作环境和有限的空间结构,实现伺服作动器齿条位移的测量及反馈。一种小型高可靠分体式多冗余线位移传感器的研制,在传统的分体式线位移传感器的基础上,通过四冗余的结构设计,印制电阻膜的设计,零位输出可调的设计,多指型电刷受力的优化设计,实现了线位移传感器的结构小型化和紧凑化的冗余功能,能够耐高温,工作寿命长,线性精度高的性能。试验和仿真分析表明设计技术方案有效可行,能够满足伺服系统的要求。     

Sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner

This paper presents the sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner (Z, θ_x, θ_y). This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. In order to design the feedback controller, the open‐loop characteristics of this nanopositioner are investigated. Based on the results of the investigation, each pair of piezoelectric actuators and corresponding gap sensors is treated as an independent system and modeled as a first‐order linear model coupled with hysteresis. When the model is identified and the hysteresis nonlinearity is linearized, a linear system model with uncertainty is used to design the controller. When designing the controller, the sliding‐mode disturbance (uncertainty) estimation and compensation scheme is used. The structure of the proposed controller is similar to that of a proportional integral derivative controller. Thus, it can be easily implemented. Experimental results show that 3‐nm tracking resolution can be obtained. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

A coordinating approach for the solution of discrete linear servo‐mechanism problems with constraints

A discrete‐time linear servo‐mechanism problem with system constraints is considered. An approach is developed to solve such a problem using an idea borrowed from large‐scale systems theory, in which a coordinating variable is introduced and used to satisfy state constraints. Under the assumption that the system is stabilizable and has a feasible solution, it is shown that the proposed procedure leads to the optimal solution while satisfying system constraints. A convergence analysis of the algorithm is undertaken and illustrative examples are provided to show the performance of the proposed algorithm. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

基于TMS320LF2407A的节能型变频调速系统在电牵引采煤机上的实现

针对现有大功率电牵引采煤机能耗高的问题,提出了一种基于TMS320F2407A的"双逆变器-双电动机"节能型变频调速系统的设计方案,介绍了该系统的组成,分析了系统的工作原理,给出了系统的节能计算公式。该系统以交流异步电动机作为模拟负载,双逆变器在直流母线侧采用并联接线方式,应用DSP实时控制和跟踪随动系统,实现了电牵引采煤机电动机状态的改变,整个系统为能量的回馈提供了输送路径。Matlab仿真结果证明该系统原理正确,节能效果显著。     

A Novel Robust Constraint Force Servo Control for Under‐actuated Manipulator Systems: Fuzzy and Optimal

We consider the control design for under‐actuated manipulator systems. The task is to drive the system to be close to a prescribed constraint. The system contains uncertainty. It is bounded where the bounding information is prescribed by a fuzzy set (e.g., the bound is close to 1). The initial condition is also prescribed by a fuzzy set. A class of robust control is proposed, which guarantees a deterministic performance. On top of that, the choice of a control design parameter is cast into a fuzzy‐theoretic setting. A performance index, consisting of accumulated fuzzy‐based system performance and control cost, is proposed. The optimal control design parameters, which minimize the performance index, can be obtained by solving two algebraic quartic (fourth‐order) equations. As a result, the control design problem, which addresses both fuzzy and optimal characteristics, is completely solved.     

PSS 3-2-1正交并联机构动平台的位姿控制

提出了一种便于实现的,简单方便的控制策略,即基于新型正交六自由度并联机构动平台系统的运动学特性,首先对动平台的逆运动学进行分析,建立逆运动学方程,然后建立无刷电动机的数学模型,由给定的平台质心的预期轨迹,通过逆解解出各运动支链的位移矢量,将其作为由驱动电机和编码器构成的半位移闭环的系统输入量,设计了一个模糊PID自整定控制器,用控制器对支链杆长变化进行跟踪,最后进行仿真实验。结果表明了所设计的模糊PID自整定控制器比模糊PID控制器能明显地改善控制系统的动态性能,具有响应速度快,调节时间短,稳定性好,抗干扰能力强,可以快速跟踪给定杆长变化,提高了系统的动态性能,证明了该控制方法的有效性,为PSS 3-2-1正交并联机构动平台的控制奠定了基础。     

A novel contour error compensator for 3‐PRPS platform

Using a mathematical model to represent the nonlinear characteristics in dynamics of robot manipulators is rather difficult. To reduce the Cartesian space contour error, this study presents a novel contour error compensator influenced by the parameter and unstructured uncertainties in robot manipulators. The proposed compensator is based on the strategy of a Cartesian space cross‐coupled control and the transform relations between Cartesian space and joint space. In addition, the joint space compensated control effort derives reducing the Cartesian space contour error. Consequently, the contour error can be reduced via the theoretical analysis. Moreover, a PC based, 3‐PRPS platform control system is constructed to closely examine the effects of the controller. Experiment results indicate that the controller can reduce the contour error as expected. Furthermore, the forward and the inverse kinematics are derived, along with the forward kinematics solved using the numerical method. The work space of the platform is also described in a three‐dimensional Cartesian space. © 2000 John Wiley & Sons, Inc.     

Gpc‐Based Self‐Tuning PI Controller for Speed Servo System of PMSLM

In this paper, a generalized predictive control (GPC)‐based two degrees of freedom (2 DOF) proportional integral (PI) controller is proposed for the speed servo system of a permanent magnet synchronous linear motor (PMSLM). In this new approach, based on a dynamic model of a servo system, a simplified and high‐performance GPC supplies a 2 DOF PI controller with suitable control parameters, according to the varied operating conditions. In previous studies, GPC‐based proportional integral derivative (PID) controllers have been designed using a step‐type or ramp‐type reference input. In our work, however, the speed command for PMSLM usually is required to be a trapezium‐type signal because of the limited travel range. Hence, control performance of a speed servo system using a GPC‐based 2 DOF PI controller is enhanced for tracking a trapezium‐type command. The validity and usefulness of the proposed controller are verified through simulation and experiments.     

Stochastic Optimal Design for Unknown Linear Discrete‐Time System Zero‐Sum Games in Input‐Output form Under Communication Constraints

In this paper, stochastic optimal strategy for unknown linear discrete‐time system quadratic zero‐sum games in input‐output form with communication imperfections such as network‐induced delays and packet losses, otherwise referred to as networked control system (NCS) zero‐sum games, relating to the H_∞ optimal control problem is solved in a forward‐in‐time manner. First, the linear discrete‐time zero sum state space representation is transformed into a linear NCS in the state space form after incorporating random delays and packet losses and then into the input‐output form. Subsequently, the stochastic optimal approach, referred to as adaptive dynamic programming (ADP), is introduced which estimates the cost or value function to solve the infinite horizon optimal regulation of unknown linear NCS quadratic zero‐sum games in the presence of communication imperfections. The optimal control and worst case disturbance inputs are derived based on the estimated value function in the absence of state measurements. An update law for tuning the unknown parameters of the value function estimator is derived and Lyapunov theory is used to show that all signals are asymptotically stable (AS) and that the estimated control and disturbance signals converge to optimal control and worst case disturbances, respectively. Simulation results are included to verify the theoretical claims.     

Two‐Layer Terminal Sliding Mode Attitude Control of Satellites Equipped with Reaction Wheels

This paper addresses the global stability and robust attitude tracking problem of a near polar orbit satellite subject to unknown disturbances and uncertainties. It is assumed that the satellite is fully actuated by a set of reaction wheels (RW) as control actuators because of their relative simplicity, versatility and high accuracy. The terminal sliding mode control (TSMC) approach is utilized in a two‐level architecture to achieve control objectives. In the lower layer a detumbling‐like controller is designed which guarantees the finite‐time detumbling and tracking of the desired angular velocities and based on this result a robust attitude tracking controller is designed in the upper layer to achieve 3‐axis attitude tracking in the presence of unknown disturbances and bounded uncertainties. Robust stability and tracking properties of designed controllers are proved using the Lyapunov theory. Finally, a set of numerical simulation results are provided to illustrate the effectiveness and performance of the proposed control method.     

Dynamic intermittent Q‐learning–based model‐free suboptimal co‐design of ‐stabilization

This paper proposes an intermittent model‐free learning algorithm for linear time‐invariant systems, where the control policy and transmission decisions are co‐designed simultaneously while also being subjected to worst‐case disturbances. The control policy is designed by introducing an internal dynamical system to further reduce the transmission rate and provide bandwidth flexibility in cyber‐physical systems. Moreover, a Q‐learning algorithm with two actors and a single critic structure is developed to learn the optimal parameters of a Q‐function. It is shown by using an impulsive system approach that the closed‐loop system has an asymptotically stable equilibrium and that no Zeno behavior occurs. Furthermore, a qualitative performance analysis of the model‐free dynamic intermittent framework is given and shows the degree of suboptimality concerning the optimal continuous updated controller. Finally, a numerical simulation of an unknown system is carried out to highlight the efficacy of the proposed framework.     

Global Asymptotic Stability of PD Control for PM Stepper Motor Servo‐Systems

Commutation is a well‐known and successful strategy used in practice to control permanent magnet stepper motors. However, stability analysis has not been presented until now for this simple control strategy. In this note we prove, for the first time, that commutation achieves global asymptotic stability when used to regulate position in Euler–Lagrange systems actuated by permanent magnet stepper motors. Contrary to the traditional design methodology, this is accomplished by taking into account the electrical dynamics of the motors and, hence, we avoid the possibility of either performance degradation or instability due to the neglected electrical dynamics. We include high‐gain electric current loops and we introduce a saturated output feedback PD controller as the desired torque, i.e. velocity measurements are not required.     

Output feedback quantized observer‐based synchronization of linear multi‐agent systems over jointly connected topologies

The synchronization problem of linear over‐actuated multi‐agent systems with unmeasurable states is studied in this paper, under both limited communication data rate and switching topology flows. A class of adaptive quantized observer‐based encoding–decoding schemes and a class of certainty equivalence principle‐based control protocols are proposed. By developing the graph‐based space decomposition technique and analyzing the closed‐loop quantized dynamic equations, it is shown that if the network topology flow is jointly connected, the communication channels are periodic active, and the agent dynamics is observable, and with the orthogonal system matrix, the proposed communication and control protocols can ensure the closed‐loop system to achieve synchronization exponentially fast with finite bits of information exchange per step. Copyright © 2015 John Wiley & Sons, Ltd.     

INPUT‐STATE LINEARIZATION OF A ROTARY INVERTED PENDULUM

The aim of this paper is to design a nonlinear controller for the rotary inverted pendulum system using the input‐state linearization method. The system is linearized, and the conditions necessary for the system to be linearizable are discussed. The range of the equilibriums of the system is also investigated. Further, after the system is linearized, the linear servo controllers are designed based on the pole‐placement scheme to control the output tracking problem. The performance of the controller is studied with different system parameters. The computer simulations demonstrate that the controller can effectively track the reference inputs.