基于鲁棒开环解耦的系统逆二自由度控制

针对MIMO系统的轨迹跟踪,提出一种基于鲁棒开环解耦的系统逆二自由度（2DOF）控制方法．该方法通过鲁棒开环解耦解决MIMO系统的耦合问题,利用系统逆2DOF控制保证轨迹跟踪性能．首先提出一种保证预补偿器阶数最小和解耦系统鲁棒性的鲁棒开环解耦方法;然后结合鲁棒开环解耦和系统逆2DOF控制,给出系统逆前馈控制和H∞混合灵敏度鲁棒反馈控制器的设计方法;最后通过设计实例及仿真结果验证了该控制方法的有效性．     

直流位置伺服系统的二自由度分数阶控制

为提高直流位置伺服系统的控制性能,提出了一种2自由度（two degree-of-freedom,2DOF）分数阶控制方法．通过设计一种2DOF控制结构,实现了系统的跟随和抗扰特性的解耦控制;将内模控制（internal model control,IMC）与分数阶控制相结合,选用分数阶滤波器,推导出了跟随控制器和抗扰控制器设计方法;根据控制性能的要求,利用系统截止频率和最大灵敏度指标,实现了2DOF控制器参数的解析整定．仿真实验结果表明,2DOF分数阶控制方法具有良好的位置跟随特性和抗干扰能力．     

The design and empirical evaluations of 3D positioning techniques for pressure-based touch control on mobile devices

The previous three degrees of freedom (DOF) 3D touch translations require more than one finger (usually two hands) to be performed, which limits their usability on mobile devices that need one hand to be held in most occasions. Given that the pressure-sensitive touch screen will become ubiquitous in the near future, we presented a pressure-based 3DOF 3D positioning technique that only uses one finger in operating. Our technique collects the normal force of the touch pressure and uses it to represent the depth value in 3D translating. Then we conducted several groups of tightly controlled user studies to conclude (1) how different strategies of pressure recognition will affect 3D translating and (2) how is the performance of the pressure-based manipulation compared to the previous two-fingered technique. Finally, we discussed some guidelines to help developers in the design of the pressure-sensing technique in 3D manipulations.     

一类新的PPA型三连杆欠驱动机器人的控制策略

PPA型机器人是一类新型的三连杆欠驱动机械系统,具有3个自由度,但只有1个驱动装置.针对这类欠驱动机器人的运动控制,提出一种分区的控制策略,使之从垂直向下的位置摇起到垂直向上的位置,并实现稳定控制.首先,将系统的运动空间划分为摇起区和吸引区;其次,应用一种基于Lyapunov函数的控制方法来增加系统能量和控制驱动杆姿态,实现摇起操作;再次,采用最优控制方法设计平衡控制,实现稳定的平衡控制;最后,通过仿真实验验证了所提出控制方法的有效性.     

Design of the annular suspension and pointing system (ASPS) through decoupling and pole placement

This paper describes the decoupling and pole-placement design of the ASPS with continuous-data control and with digital control. The dynamics of the ASPS are represented by a simplified small-angle, small-displacement planar model with four degrees of freedom. The model includes a mount, a gimbal assembly, a pallet with magnetic actuators, and a payload. The pallet has one rotational degree of freedom relative to the mount, and the payload has two translational and one rotational degrees of freedom relative to the pallet. One of the translation degrees of freedom of the payload is not coupled to the other three degrees of freedom of the payload is not coupled to the other three degrees of freedom. The bandwidth requirements of the various degrees of freedom are specified. The continuous-data system with state feedback is designed through decoupling and pole placement. It was found that the digital ASPS cannot be completely decoupled. However, the bandwidth requirements were satisfied by pole placement and a trial-and-error method based on approximate decoupling. The time responses of the designed systems are investigated by computer simulation.     

基于系数图法的多输入多输出系统控制器设计方法

多输入多输出系统的交互作用会限制适用于单输入单输出系统的多种先进设计方法的使用,且多数关于多输入多输出系统控制研究只重视消除交互作用的影响,忽略系统控制问题,这样不但弱化系统的鲁棒性,且设计过程复杂,解耦后系统阶次也较高.鉴于此,提出一种基于系数图法的多入多出系统的控制器设计方法,将多输入多输出系统解耦问题转化为参数优化问题.首先,给出目标函数和两个线性约束条件,通过在频域基于粒子群算法优化目标函数,从而设计补偿器实现解耦;其次,基于系数图法确定控制器结构及参数整定,兼顾系统的稳定性和鲁棒性;最后,通过仿真实验验证所提出方法的有效性.     

Simultaneous stabilization and trajectory tracking of underactuated mechanical systems with included actuators dynamics

The paper deals with a novel control algorithm for simultaneous stabilization and trajectory tracking of underactuated nonlinear mechanical systems (UNMS) with included actuators dynamics. Simultaneous stabilization and trajectory tracking refer to arbitrary chosen actuated and unactuated degrees of freedom (DOF) of the system. The proposed control approach can be applied both to the second-order nonholonomic systems and the systems with input coupling, while a general model of actuators dynamics includes electrical, pneumatic, and hydraulic drives. Control law is based on linear combination of two control signals, where the first signal is designed to separately control only actuated DOF, and second to separately control only unactuated DOF. Simulation example of rotational inverted pendulum driven by electrical DC motor is presented, showing the effectiveness of the proposed approach.     

A combination of fuzzy logic and neural network controller for multiple-input multiple-output systems

Generally, the difficulty of multiple-input multiple-output (MIMO) systems control is how to overcome the coupling effects between the degrees of freedom. Owing to the computational burden and dynamic uncertainty of MIMO systems, the model-based decoupling approach is not practical for real-time control. A hybrid fuzzy logic and neural network controller (HFNC) is proposed here to overcome this problem and to improve the control performance. Firstly, a traditional fuzzy controller (TFC) is designed from a single-input single-output (SISO) systems viewpoint for controlling the degrees of freedom of a MIMO system. Secondly, an appropriate coupling neural network controller is introduced into the TFC for compensating the system coupling effects. This control strategy not only can simplify the implementation problem of fuzzy control but also can improve the control performance. The state-space approach for fuzzy control systems stability analysis is employed to evaluate the stability and robustness of this intelligent hybrid controller. In addition, a dynamic absorber with a twolevel mass-spring-damper structure was designed and constructed to verify the stability and robustness of a HFNC by numerical simulation and to investigate the control performance by comparing the experimental results of the HFNC with that of a TFC for this MIMO system.     

A new control method for MIMO first order time delay non-square systems

This paper proposes a new method using internal model control (IMC) to design Smith delay compensation decoupling controller for multivariable non-square systems with transfer function elements consisting of first order + time delay. This proposed method is applied to a shell control problem in multiple-input-multiple-output (MIMO) first order plus dead time non-square systems in which the number of input variables exceeds the number of output variables, with input and output variables being 3 and 2 respectively. This method does not only dynamically compensate for shortcoming caused by static decoupling but also overcomes the impact of model error on system performance caused by model approximation and uncertainty. In other words, the design method proposed in this paper is capable of significantly improving dynamic quality and robustness of the control system as can be seen from the simulation results. Moreover, this new method is simple and easy to implement. Integral of squared error (ISE) performance criterion is employed to quantitatively evaluate the design method.     

A differential evolution based neural network approach to nonlinear system identification

This paper addresses the effectiveness of soft computing approaches such as evolutionary computation (EC) and neural network (NN) to system identification of nonlinear systems. In this work, two evolutionary computing approaches namely differential evolution (DE) and opposition based differential evolution (ODE) combined with Levenberg Marquardt algorithm have been considered for training the feed-forward neural network applied for nonlinear system identification. Results obtained envisage that the proposed combined opposition based differential evolution neural network (ODE-NN) approach to identification of nonlinear system exhibits better model identification accuracy compared to differential evolution neural network (DE-NN) approach. The above method is finally tested on a one degree of freedom (1DOF) highly nonlinear twin rotor multi-input–multi-output system (TRMS) to verify the identification performance.     

带有控制受限的卫星编队飞行六自由度自适应协同控制

针对存在参数不确定性以及干扰的卫星编队飞行六自由度协同控制问题,提出了一种满足控制输入有界的自适应L2增益干扰抑制控制方法.该方法首先在不考虑干扰的条件下,针对卫星编队六自由度协同运动模型存在参数不确定性提出了一种自适应协同控制器;接着,考虑到系统存在干扰,进一步设计了具有L2增益干扰抑制能力且满足输入有界条件的自适应...     

Design and Control of Five-Fingered Haptic Interface Opposite to Human Hand

This paper presents the design and control of a newly developed five-fingered haptic interface robot named HIRO II. The developed haptic interface can present force and tactile feeling to the five fingertips of the human hand. Its mechanism consists of a 6 degree of freedom (DOF) arm and a 15 DOF hand. The interface is placed opposite the human hand, which ensures safety and freedom of movement, but this arrangement leads to difficulty in designing and controlling the haptic interface, which should accurately track the fingertip positions of the operator. A design concept and optimum haptic finger layout, which maximizes the design performance index is presented. The design performance index consists of the product space between the operator's finger and the hapic finger, and the opposability of the thumb and fingers. Moreover, in order to reduce the feeling of uneasiness in the operator, a mixed control method consisting of a finger-force control and an arm position control intended to maximize the control performance index, which consists of the hand manipulability measure and the norm of the arm-joint angle vector is proposed. The experimental results demonstrate the high potential of the multifingered haptic interface robot HIRO II⁺ utilizing the mixed control method.     

卫星光通信精确跟踪控制系统的参数化综合优化设计

精确跟踪对准控制系统在卫星光通信中起着至关重要的作用.我国已完成的墨子号量子科学实验卫星,是基于经典随动系统理论设计的跟踪与瞄准系统,并在实践中取得了圆满效果.面向未来更远距离的空间通信应用,对跟踪与瞄准系统提出了更高的精度要求,传统的控制方法很难满足.为此本文提出了精确瞄准系统的一种参数化设计方法,抛弃了传统方法的精、粗系统分别设计的思想,对两级子系统进行整体设计,充分地利用了系统中的设计自由度.通过综合优化这些设计自由度,实现了系统对阶跃干扰的解耦和复杂干扰的抑制、不敏感极点配置和控制增益极小化等各项设计要求,从而显著地提高了对准精度.仿真结果表明,对准精度由原来的微弧度量级提高到了纳弧度量级.     

ROBUST TWO‐DEGREE‐OF‐FREEDOM CONTROL OF AN ATOMIC FORCE MICROSCOPE

The performance of an atomic force microscope (AFM) is improved substantially by utilizing modern model‐based control methods in comparison to a standard proportional‐integral (PI) controlled AFM system. We present the design and implementation of a two‐degree‐of‐freedom (2DOF)‐controller to accomplish topography measurements at high scan‐rates with reduced measurement error. An H_∞‐controller operates the AFM system in a closed loop while a model‐based feedforward controller tracks the scanner to the last recorded scan‐line. Experimental results compare the actual performance of the standard PI‐controlled AFM and the 2DOF controlled system. The new controller reduces the control error considerably and enables imaging at higher speeds and at weaker tip‐sample interaction forces.     

一类非自衡对象的二自由度PID控制

针对一类典型的非自衡过程控制对象，根据内模控制理论提出一种二自由度PID调节器的设计方法，所设计的调节器仅有两个可调参数，而且被调参数与系统的性能直接相关，可使系统同时具有良好的目标值跟随特性和干扰抑制特性，仿真结果表明了它的有效性。     

Behavioral-model-based freehand tracking in a Selection-Move-Release system

The development of three dimensional (3D) freehand tracking is motivated by the need for 3D freehand-based human computer interface in the Selection-Move-Release (SMR) system. The high dimensionality of articulated hand models is one of the major obstacles for tracking 3D hand in real time. A practical Task-Phase-Trajectory-Mentality (TPTM) model for the SMR system is built and a novel freehand tracking algorithm is introduced by using a camera that is calibrated by a charge-coupled device. The TPTM model is proposed and explained based on the cognitive theory in the proposed method. The manner by which the TPTM model guides the realtime design of freehand tracking is also shown. The proposed method reduces the high dimensionality down to eight degrees of freedom (DOF), optimizes the dynamic number of particles for each frame, and achieves realtime hand tracking and high accuracy of 3D full DOF hand gestures. The algorithm presented in this paper is successfully applied to a 3D virtual teaching system.     

System gains configuration and coordination of redundant degrees of freedom by genetic algorithms for multi-axis machine system in manufacturing

In multi-axis machine tool systems, the configuration of system gains and the coordination of redundant degrees of freedom are often a problem of insurmountable difficulty. This study explores the use of a nontraditional scheme, the genetic algorithm, in the configuration of system gains and exploitation of redundant degrees of freedom. The off-line gains configuration functioned as a kind of system design which may serve as a starting point for on-line adaptation. The allocation of redundant DOF was done on-line. The success in this work inspired the idea of future on-line GA application and the possibility of integration of GA with other non-traditional algorithms for manufacturing.     

Active Disturbance Rejection Control System Design for a Morphing Wing Structure

Control system design for a morphing wing structure, which is proposed by NextGen Aeronautics, Inc., is investigated in this paper. The dynamic model of the morphing wing, developed based on the Euler‐Lagrange equation, is nonlinear, multivariable coupled, over‐actuated and uncertain. The allocation‐decoupling controller is designed based on control efficiency and decoupling matrices. For each decoupled subsystem, nonlinear and linear active disturbance rejection control (ADRC) systems are designed and compared. The time‐optimal property and the convergence of nonlinear ADRC are analyzed theoretically based on the isochronic region and Lyapunov theories. The simulation results of the developed control systems show satisfactory performances of decoupling and extreme tolerance of internal uncertainty and external disturbance. The comparison of nonlinear and linear ADRC systems demonstrate that the nonlinear system can provide a little better performance while the linear system can greatly simplify the design procedure. The results indicate that, the methods of control system design proposed in this paper are practical and effective for motion control of complex uncertain dynamical systems.     

Robust orientation control of multi‐DOF cell based on uncertainty and disturbance estimation

Multiple degrees‐of‐freedom (multi‐DOF) cell orientation control is a vital important technique involved in single cell surgery applications. Currently, few studies have been performed toward automation of multi‐DOF cell orientation control using robotically controlled optical tweezers. In this paper, a robust control framework is developed to perform multi‐DOF cell rotational control with consideration of model uncertainties and external disturbances. Both simulation and experimental studies are presented to illustrate the performance of the proposed control strategy. The main contributions of this work lie in that this is the first time to develop a unified framework to achieve multi‐DOF cell orientation control without the need for accurate dynamic model parameters and/or any knowledge about uncertainty characteristic, which greatly enhances the robustness of the overall system.     

The importance of the number of degrees of freedom for rotation of objects

In an experiment input methods for object rotation with differing degrees of freedom were assessed. The results are relevant for human- computer interfacing, not only for the finger tip controlled interface proposed in this paper but also for evaluation of existing approaches to rotation. When designing an interface with finger tip controlled rotation of virtual objects, for technical reasons the number of finger tips to be registered should be minimized. Performance of subjects who rotated real objects with different numbers of finger tips was assessed. Subjects rotated a transparent sphere encasing an object according to their personal preference, with three, two or one finger, and restricted to three orthogonal axes. The latter reflects rotation in much current 3D software, whereby only one rotational degree of freedom (DOF) is accessible at a time. Performance in the three and two finger conditions did not differ significantly from the free condition, whilst performance with one finger and orthogonally restricted was significantly lower. However, only the three finger condition was rated as comfortable as the free condition, whilst the two finger, one finger and orthogonally restricted conditions were rated as less comfortable. It is argued that the number of DOFS which can be accessed simultaneously is an important design consideration when quick and intuitive rotation is to be achieved.