匹配和不匹配干扰共存时电液伺服系统预设性能渐近跟踪控制

针对电液伺服系统匹配和不匹配干扰共存的特点,兼顾瞬态性能和稳态性能需求,提出一种新型高精度跟踪控制策略。以阀控电液位置伺服系统为例,建立了包含匹配和不匹配干扰的系统非线性数学模型,定义预设性能函数规划控制误差,基于规划后的转换误差设计反步控制器,并融合采用干扰上界估计的连续渐近控制技术处理匹配和不匹配干扰,获得了可预设的瞬态性能和渐近稳态性能,通过Lyapunov分析证明了稳定性。两种位置指令跟踪试验的结果表明,相比PID控制和反馈线性化控制,初始阶段跟踪精度提高超22.9%,相比仅引入预设性能函数的控制器,稳态跟踪精度提高超42.9%。     

含未知磁滞输入的机械臂系统预设性能控制

针对一类含有未知磁滞输入的单连杆机械臂系统，提出一种基于动态面的自适应预设性能控制方案。利用Bouc-Wen模型描述机械臂执行机构内的磁滞现象，通过RBF神经网络预估该系统内的未知函数，同时利用Funnel控制确保跟踪误差的最大超调量，据此按照动态面策略设计控制器以避免传统反演策略所固有的微分膨胀问题。理论分析表明该方案能有效消除未知磁滞的影响，能同时确保系统的瞬态及稳态性能，并能确保闭环系统内全部信号达到半全局有界。最后，通过仿真对该方案的有效性进行验证。     

卫星星间激光通信粗跟踪转台控制系统

为了满足卫星星间激光通信粗跟踪系统高的动态性能和稳态性能,针对普通PID控制存在阶跃响应超调量大、调节时间过长等问题,以永磁同步电动机为控制对象建立粗跟踪系统的三环控制模型,并进行matlab仿真分析.在普通PI控制的基础上提出一种自适应增益控制,为跟踪系统缩短调节时间改善超调等动态性能提供新的方法,在基于FPGA主控单元的控制下.地面实验表明,在187.25μrad(500码)阶跃信号的激励下,改进的自适应增益控制策略较普通PI控制,超调量由35.8％下降到10％,调节时间由100 ms缩短到70 ms,稳态精度保持在±2.247μrad(3码),控制性能得到了显著改善.在轨工况下,自适应增益控制策略能够实现星间激光通信跟踪转台的高精度控制,同时对其他高精度伺服系统设计具有借鉴意义.     

基于终端滑模控制器的高精度伺服系统设计

随着工业机器人与精密机床的发展,传统的三环控制策略无法满足伺服系统对动态响应速度、位置跟踪精度及超调量越来越高的要求。针对这一问题,结合已有的研究成果,提出微分前馈控制与终端滑模结合的控制策略,在负反馈基础上,添加位置前馈控制,实现位置信号的快速跟踪,将非奇异快速终端滑模控制方法应用到位置环与速度环,提高电机位置跟踪精度以及在电机出现较大位置误差时减小超调量。理论分析和仿真验证算法的可行性和有效性。     

光电跟踪平台的观测自适应控制器

为解决导引头稳态跟踪精度与快速目标跟踪能力难以兼容的问题,建立了导引头伺服系统模型,通过分析传统PID控制策略的优势和缺陷,提出了改进自适应控制算法的研究思路。首先,利用自适应方程调节控制器参数以满足对不同速度目标的跟踪能力,并且通过非连续性观测投影对自适应参数进行控制,保证自适应参数始终处于和当前状态匹配的范围内。此外,利用状态识别控制提高响应速度并抑制快速跟踪时带来的噪声放大问题,同时通过线性反馈保证系统对随机扰动的鲁棒性。最后,利用自抗扰控制的过渡函数解决跟踪环带给速度环的超调问题。通过某型号导引头的实验测试,跟踪12(°)/s的运动目标时,观测自适应控制器输出的视线角速度的动态误差为0.05(°)/s(标准差),相比比例制导减小了53%;跟踪10(°)/s以下的目标时,超调量控制在8%以内,动态误差小于0.046(°)/s。结果表明,该算法可以提高光电平台的自适应性和跟踪精度。     

基于非奇异终端滑模的电机伺服系统预设性能控制

针对电机伺服系统角度跟踪控制问题,提出非奇异终端滑模(Nonsingular terminal sliding mode,NTSM)与扩张状态观测器(Extended state observer,ESO)相结合的预设性能控制策略。利用性能预设函数(Prescribed performance function,PPF)将角度跟踪误差转化为一个变换误差,通过控制变换误差的有界性间接保证角度跟踪误差始终在预设范围内。构造ESO观测系统的模型不确定性,包括系统参数偏差、非线性摩擦和外部扰动等,并用于控制器的前馈补偿设计以提升跟踪性能;同时设计NTSM控制律保证系统的有限时间稳定性。通过Lyapunov稳定性理论证明了所提控制策略可以保证变换误差的有界性和闭环系统的稳定性。基于电机伺服系统试验平台的对比试验结果表明,所提控制策略在不同频率期望轨迹的条件下,均具备较好的控制精度,相较于NTSM+ESO控制器和NTSM控制器,控制性能分别提升了14%和37%左右,验证了所提控制策略的有效性。     

基于超稳定性理论的位置伺服系统自适应控制

建立了发动机节气门伺服系统的非线性模型,并进行了线性化处理,得到了简单有效的控制模型;以波波夫超稳定性理论为基础,设计了伺服系统的自适应控制律;通过计算机仿真验证,在保证伺服系统响应速度的同时,自适应控制算法有效地提高了伺服系统的控制精度和稳定性;采用微控制器进行了机载实验,实际超调量仅为0.1%,跟踪控制误差小于0....     

基于修正LuGre模型的自适应鲁棒控制在机电伺服系统中的应用

机电位置伺服系统是典型的非线性系统,且存在诸多不确定性,使得传统方法设计的闭环控制器往往不能满足系统的高性能需求。针对动态摩擦参数和系统负载特性未知的情况,为伺服系统设计一种基于动态面滤波法的自适应鲁棒跟踪策略。构造一个非线性观测器来估计摩擦力矩,利用动态面滤波器简化控制器的设计,设计自适应鲁棒控制器以提高系统的稳态控制精度及鲁棒性。基于Lyapunov稳定性定理证明闭环系统的所有信号半全局一致有界,通过适当选择设计参数及初始化误差变量,跟踪误差可收敛到原点的一个任意小邻域内。仿真和试验结果表明,该控制器能够能有效地抑制摩擦干扰对伺服系统的不利影响,显著提高了系统的控制精度,为提高伺服系统的动态跟踪性能奠定基础。     

大范围平动并联机器人运动学解耦与速度自适应规划

并联机器人是一种多支链、多关节、强耦合非线性系统,具有高速、高刚度和大负载等明显优势而被广泛应用到工业领域。然而,随着关节数量的增加导致该类机器人运动学解耦和高精度平稳控制的难度较大。为实现大范围平动3-RRRU并联机器人自动化轨迹跟踪和控制的平稳性,针对运动学解耦和速度自适应规划方法展开了系统、深入地研究。首先,应用DH法建立了机器人运动学模型,基于结构约束条件完成运动学解耦计算,并在S型控制策略中加入速度自适应修正机制,依据不同轨迹可自动计算并修正最大速度参数,实现自适应优化;其次,采用激光跟踪仪对机器人轨迹进行动态跟踪,对比分析了S型速度和梯型速度控制策略下的跟踪精度,梯型速度规划下其最大误差高达4.513 mm,是S型控制策略的3倍,且位置误差曲线出现多个尖峰值,说明因速度突变导致运动平稳性较差;最后,测试S型速度规划下采用自适应修正机制前、后机器人的平稳性以及轨迹跟踪精度。实验结果表明:当规划路径难以实现机器人加速到原预设最大速度时,在轨迹末端存在较大的惯性速度,产生位置尖峰误差为2.676 mm,是修正后最大误差的2.4倍,且伴随着明显的冲击效应。引入自适应修正机制后圆轨迹的起点和终点位置误差分别为0.722 mm和0.382 mm,二者相对位置偏差仅为0.34 mm,且末端定位误差相比修正前降低了一个数量级,有效解决了机器人存在惯性冲击效应的难题,大幅提高了机器人整体轨迹跟踪的精度和控制的平稳性。     

直驱泵控压力伺服系统自适应模糊PID控制

直驱泵控压力伺服系统属于典型的非线性时变系统,采用传统PID控制存在系统适应性差、压力波动幅度大以及跟踪控制精度低等问题。根据PID参数对压力伺服系统响应特性的影响规律,设计了根据系统误差和误差变化率在线自适应调整PID参数的自适应模糊PID控制器,分别采用传统PID控制和自适应模糊PID控制策略进行了直驱泵控压力伺服控制仿真与实验研究。结果表明,自适应模糊PID控制策略能大大改善PID控制的性能,使系统具有响应速度快、压力波动幅度降低、滞后与超调小的特点,提高了系统的动态品质和控制精度。     

Robust internal model control of servo motor based on sliding mode control approach

This paper proposes a robust internal model control (IMC) based on sliding mode control (SMC) approach for high-performance motion control of a servo motor subject to uncertainties and/or disturbances. The proposed control strategy considers not only the simplicity and intuition of the IMC-based controller for a prescribed tracking performance but also the effectiveness of the SMC scheme to guarantee the robustness of the servo system. Since the performance of the IMC-based controller can be analyzed via a SMC structure, a robust control law based on the SMC technique is introduced into the IMC scheme to decrease the sensitivity to uncertainties and enhance the resistance to disturbances. Moreover, the 2-degree-of-freedom IMC integrating the robust SMC scheme is developed to further improve the control performance. The stability is analyzed based on Lyapunov theory, and the theoretical results show that a prescribed transient tracking performance and a final tracking accuracy of the servo system can be guaranteed. Comparative simulations and experiments are investigated to verify the high performance nature of the proposed control strategy.     

电液伺服力控系统的自适应滑模控制

针对存在不确定性的非线性电液伺服力控系统的跟踪控制问题,基于等价控制的概念,提出了一种自适应滑模控制律综合方法,应用参数自适应的方法,消除不确定性对控制性能的影响,以达到鲁棒跟踪控制的目的。为了证明这种控制器可行性,利用微机实现的该控制器被应用于某疲劳试验机电液伺服系统,实时控制的结果验证了所提方法的有效性。     

Direct adaptive robust tracking control for 6 DOF industrial robot with enhanced accuracy

A direct adaptive robust tracking control is proposed for trajectory tracking of 6 DOF industrial robot in the presence of parametric uncertainties, external disturbances and uncertain nonlinearities. The controller is designed based on the dynamic characteristics in the working space of the end-effector of the 6 DOF robot. The controller includes robust control term and model compensation term that is developed directly based on the input reference or desired motion trajectory. A projection-type parametric adaptation law is also designed to compensate for parametric estimation errors for the adaptive robust control. The feasibility and effectiveness of the proposed direct adaptive robust control law and the associated projection-type parametric adaptation law have been comparatively evaluated based on two 6 DOF industrial robots. The test results demonstrate that the proposed control can be employed to better maintain the desired trajectory tracking even in the presence of large parametric uncertainties and external disturbances as compared with PD controller and nonlinear controller. The parametric estimates also eventually converge to the real values along with the convergence of tracking errors, which further validate the effectiveness of the proposed parametric adaption law.     

Robust adaptive precision motion control of hydraulic actuators with valve dead-zone compensation

This paper addresses the high performance motion control of hydraulic actuators with parametric uncertainties, unmodeled disturbances and unknown valve dead-zone. By constructing a smooth dead-zone inverse, a robust adaptive controller is proposed via backstepping method, in which adaptive law is synthesized to deal with parametric uncertainties and a continuous nonlinear robust control law to suppress unmodeled disturbances. Since the unknown dead-zone parameters can be estimated by adaptive law and then the effect of dead-zone can be compensated effectively via inverse operation, improved tracking performance can be expected. In addition, the disturbance upper bounds can also be updated online by adaptive laws, which increases the controller operability in practice. The Lyapunov based stability analysis shows that excellent asymptotic output tracking with zero steady-state error can be achieved by the developed controller even in the presence of unmodeled disturbance and unknown valve dead-zone. Finally, the proposed control strategy is experimentally tested on a servovalve controlled hydraulic actuation system subjected to an artificial valve dead-zone. Comparative experimental results are obtained to illustrate the effectiveness of the proposed control scheme.     

Adaptive Robust Tracking Control of Pressure Trajectory Based on Kalman Filter

When adaptive robust control(ARC) strategy based on backstepping design is applied in pneumatic servo control, accurate pressure tracking in motion is especially necessary for both force and position trajectories tracking of rodless pneumatic cylinders, and therefore an adaptive robust pressure controller is developed in this paper to improve the tracking accuracy of pressure trajectory in the chamber when the pneumatic cylinder is moving. In the proposed adaptive robust pressure controller, off-line fitting of the orifice area and on-line parameter estimation of the flow coefficient are utilized to have improved model compensation, and meanwhile robust feedback and Kalman filter are used to have strong robustness against uncertain nonlinearities, parameter fluctuations and noise. Research results demonstrate that the adaptive robust pressure controller could not only track various pressure trajectories accurately even when the pneumatic cylinder is moving, but also obtain very smooth control input, which indicates the effectiveness of adaptive model compensation. Especially when a step pressure trajectory is tracked under the condition of the movement of a rodless pneumatic cylinder, maximum tracking error of ARC is 4.46 kPa and average tracking error is 0.99 kPa, and steady-state error of ARC could achieve 0.84 kPa, which is very close to the measurement accuracy of pressure transducer.     

液压柔性机械臂等效模型的鲁棒控制

针对液压柔性机械臂的等效动力学模型——柔性负载电液位置伺服系统,提出了滑模控制和自适应反演控制相结合的鲁棒控制器设计方法。基于Lyapunov稳定性理论的系统稳定性分析,证明系统跟踪误差将收敛至零,同时控制了柔性负载的振动。仿真实例表明了设计方法的正确性。     

Robust inertia-free attitude takeover control of postcapture combined spacecraft with guaranteed prescribed performance

In this paper, a robust inertia-free attitude takeover control scheme with guaranteed prescribed performance is investigated for postcapture combined spacecraft with consideration of unmeasurable states, unknown inertial property and external disturbance torque. Firstly, to estimate the unavailable angular velocity of combination accurately, a novel finite-time-convergent tracking differentiator is developed with a quite computationally achievable structure free from the unknown nonlinear dynamics of combined spacecraft. Then, a robust inertia-free prescribed performance control scheme is proposed, wherein, the transient and steady-state performance of combined spacecraft is first quantitatively studied by stabilizing the filtered attitude tracking errors. Compared with the existing works, the prominent advantage is that no parameter identifications and no neural or fuzzy nonlinear approximations are needed, which decreases the complexity of robust controller design dramatically. Moreover, the prescribed performance of combined spacecraft is guaranteed a priori without resorting to repeated regulations of the controller parameters. Finally, four illustrative examples are employed to validate the effectiveness of the proposed control scheme and tracking differentiator.     

Adaptive robust motion trajectory tracking control of pneumatic cylinders with LuGre model-based friction compensation

Friction compensation is particularly important for motion trajectory tracking control of pneumatic cylinders at low speed movement. However, most of the existing model-based friction compensation schemes use simple classical models, which are not enough to address applications with high-accuracy position requirements. Furthermore, the friction force in the cylinder is time-varying, and there exist rather severe unmodelled dynamics and unknown disturbances in the pneumatic system. To deal with these problems effectively, an adaptive robust controller with LuGre model-based dynamic friction compensation is constructed. The proposed controller employs on-line recursive least squares estimation（RLSE） to reduce the extent of parametric uncertainties, and utilizes the sliding mode control method to attenuate the effects of parameter estimation errors, unmodelled dynamics and disturbances. In addition, in order to realize LuGre model-based friction compensation, the modified dual-observer structure for estimating immeasurable friction internal state is developed. Therefore, a prescribed motion tracking transient performance and final tracking accuracy can be guaranteed. Since the system model uncertainties are unmatched, the recursive backstepping design technology is applied. In order to solve the conflicts between the sliding mode control design and the adaptive control design, the projection mapping is used to condition the RLSE algorithm so that the parameter estimates are kept within a known bounded convex set. Finally, the proposed controller is tested for tracking sinusoidal trajectories and smooth square trajectory under different loads and sudden disturbance. The testing results demonstrate that the achievable performance of the proposed controller is excellent and is much better than most other studies in literature. Especially when a 0.5 Hz sinusoidal trajectory is tracked, the maximum tracking error is 0.96 mm and the average tracking error is 0.45 mm. This paper constructs an adaptive robust controller     

Robust adaptive integral backstepping control for opto-electronic tracking system based on modified LuGre friction model

This paper presents a robust adaptive integral backstepping control strategy with friction compensation for realizing accurate and stable control of opto-electronic tracking system in the presence of nonlinear friction and external disturbance. With the help of integral control term to decrease the steady-state error of the system and combining robust adaptive control approach with the backstepping design method, a novel control method is constructed. Nonlinear modified LuGre observer is designed to estimate friction behavior. Robust adaptive integral backstepping control strategy is developed to compensate the changes in friction behavior and external disturbance of the servo system. The stability of the opto-electronic tracking system is proved by Lyapunov criterion. The performance of robust adaptive integral backstepping controller is verified by the opto-electronic tracking system with modified LuGre model in simulation and practical experiments. Compared to the adaptive integral backstepping sliding mode control method, the root mean square of angle error is reduced by 26.6% when the proposed control method is used. The experiment results demonstrate the effectiveness and robustness of the proposed strategy.