Adaptive robust control for electrical cylinder with friction compensation using modified LuGre model

The position tracking control problem of an electrical cylinder in the presence of dynamic friction nonlinearities in its transmission process is addressed in this paper. First, a torque decou- piing approach is proposed to formulate the dynamic model. Secondly, to compensate the friction in the case of servo motion, a modified LuGre model is designed to make a continuous transition be- tween a static model at a high speed and a LuGre model at a low speed to avoid instability due to dis- cretization with a finite sampling rate. To accelerate the speed of estimating time-varying parame- ters, a fast adaption law is proposed by designing an attraction domain around a rough value related to the load force. Finally, a discontinuous projection based adaptive robust controller is synthesized to effectively handle parametric uncertainties for ensuring a guaranteed robust performance. A Lya- punov stability analysis demonstrates that all signals including tracking errors have the guaranteed convergent and bounded performance. Extensive comparative simulations with sinusoidal and point- point tracks are obtained respectively in low and high speeds. The results show the effectiveness and the achievable control performance of the proposed control strategy.     

基于简化非线性观测器的LuGre动态摩擦力补偿

针对机械手臂控制中使用LuGre模型进行动态摩擦力补偿时的内部摩擦力状态识别问题,在已有的非线性观测器和基于滑模的观测器的研究基础上,缩减非线性观测器中的冗余部分,提出简化非线性观测器.采用Lyapunov方法分析基于该观测器的自适应控制算法的稳定性,说明简化观测器的使用条件为加入合适的低通滤波器,消除速度采样高频波动对观测结果的影响.实验结果对比了3种内部摩擦力状态观测器在动态LuGre摩擦力补偿中对手臂控制效果的影响,采用3种观测器进行自适应跟踪控制时的位置跟踪精度分别可以达到0.010、0.009和0.004 rad.实验表明,采用简化观测器可以取得比前2种观测器更好的自适应控制效果.     

Parameter identification of inertially stabilized platforms using current command design

Accurate parameter identification is essential when designing controllers for inertially stabilized platforms (ISPs). But traditional identification methods suffer from observation measurement noise and operating restrictions of ISPs. To address this issue, a novel identification method based on current command design and multilevel coordinate search (MCS) algorithm without any higher order measurement differentiations was proposed. The designed current commands were adopted to obtain parameter decoupled models with the platform operating under allowable conditions. MCS algorithm was employed to estimate the parameters based on parameter decoupled models. A comparison experiment between the proposed method and non-linear least square method was carried out and most of the relative errors of identified parameters obtained by the proposed method were below 10%. Simulation and experiment based on identified parameters were conducted. A velocity control structure was also developed with disturbance observer (DOB) for application in disturbance compensation control system of an ISP. Experimental results show that the control scheme based on the identified parameters with DOB has the best disturbance rejection performance. It reduces the peak to peak value (PPV) of velocity error integral to 0.8 mrad which is much smaller than the value (10 mrad) obtained by the single velocity controller without DOB. Compared with the control scheme based on sweep model with DOB compensation, the proposed control scheme improves the PPV of velocity error integral by 1.625 times.     

基于卷积力矩观测器与摩擦补偿的机器人碰撞检测

针对常规工业机器人在未知环境下运行时可能产生碰撞的安全性问题,提出一种新型的机器人碰撞检测算法. 设计卷积力矩观测器,通过实时观测关节输出力矩与动力学估计力矩的偏差实现机器人碰撞检测. 为了避免机器人处于不同位姿、运动状态等情况下关节摩擦对机器人碰撞检测的干扰,采用静态LuGre模型对关节摩擦进行补偿. 通过对实际工业机器人的运动监测,辨识出更加准确的静态LuGre模型参数. 该碰撞检测算法无需加速度信息,避免了对位置反馈信息二次求导所带来的计算误差. 关节力矩基于关节伺服驱动的电流信息获取,无需安装专门的力/力矩传感器,从而在常规工业机器人无需额外配置的情况下,只需采集机器人关节驱动电机电流和位置信息即可实现碰撞检测. 通过人与机器人交互实验验证了该碰撞检测算法的有效性.     

基于观测器摩擦补偿的机电系统高精度控制

针对机电作动系统在低速阶段摩擦非线性明显且同时存在其他干扰,易导致系统跟踪精度、稳定性下降这一问题,设计基于非线性观测器摩擦补偿的自适应鲁棒控制器. 针对摩擦非线性,利用LuGre摩擦模型描述系统的摩擦现象,提出非线性观测器对模型的内部摩擦状态进行观测. 针对系统摩擦系数、转动惯量及其他不确定性参数,设计参数自适应律进行估计. 利用前馈补偿的方法,对摩擦非线性和参数不确定性进行补偿,设计鲁棒项克服系统的其他扰动. 利用Lyapunov稳定性定理证明了提出的控制器在存在扰动的情况下可以实现系统的有界稳定性. 实验结果表明,提出的控制器具有较高的控制精度与较强的鲁棒性,跟踪精度较传统的PID控制器提高了一个数量级.     

Adaptive high precision position control of servo actuator with friction compensation using LuGre model

Adaptive control of servo actuator with nonlinear friction compensation is addressed.LuGre dynamic friction model is adopted to characterize the nonlinear friction and a new kind of sliding-mode observer is designed to estimate the internal immeasurable state of LuGre model.Based on the estimated friction state,adaptive laws are designed to identify the unknown model parameters and the external disturbances,and the system stability and asymptotic trajectory tracking performance are guaranteed by Lyapunov function.The position tracking performance is verified by the experimental results.     

一种直流力矩电机系统的滞滑摩擦补偿方法

针对陀螺漂移测试转台直流力矩电机系统中存在的非线性滞滑摩擦,使转台在PD控制下存在稳态误差的问题,应用具有stick-slip摩擦的直流力矩电机系统模型,推导了一种非线性补偿方法．该方法设计了一种非连续非线性的比例反馈力矩,使在PD控制下的转台电机系统具有惟一的平衡点,从而消除了滞滑摩擦引起的稳态误差．仿真结果证明了该非线性补偿方法的有效性．     

一种直流力矩电机系统的自适应摩擦补偿方法

针对陀螺漂移测试转台直流力矩电机系统中存在的非线性动态摩擦和负载扰动,为提高转台位置跟踪精度,提出了一种新的自适应补偿方法.电机中摩擦模型采用摩擦参数为非一致性变化的 LuGre 动态模型.该方法控制器包含一个参数自适应律和等效 PD 控制律来估计未知 LuGre 模型参数和负载力矩参数并给与补偿.最后 Lyapunov 方法和仿真结果证明该自适应补偿方法保证了闭环系统全局稳定性和对期望位置信号的渐进跟踪,提高了转台摇摆跟踪精度.     

一种直流力矩电机系统的自适应摩擦补偿方法

针对陀螺漂移测试转台直流力矩电机系统中存在的非线性动态摩擦和负载扰动，为提高转合位置跟踪精度，提出了一种新的自适应补偿方法。电机中摩擦模型采用摩擦参数为非一致性变化的LuGre动态模型。该方法控制器包含一个参数自适应律和等效PD控制律来估计未知LuGre模型参数和负载力矩参数并给与补偿。最后Lyapunov方法和仿真结果证明该自适应补偿方法保证了闭环系统全局稳定性和对期望位置信号的渐进跟踪，提高了转台摇摆跟踪精度。     

基于摩擦自适应补偿的转台变结构控制器设计

针对摩擦直接影响飞行仿真转台跟踪和定位精度,还可能引起转轴的低速爬行,以某些飞行仿真转台的一轴为对象设计了基于摩擦自适应补偿的变结构控制器,在分析了摩擦模型及其对系统特性影响的基础上,通过摩擦补偿削弱了由于摩擦造成的系统滞滑现象。通过变结构控制器设计克服了不精确摩擦补偿的缺点,在不需要精确的摩擦模型条件下保证了系统的鲁性能。通过实验表明该方法的控制效果比常规ＰＩＤ大大提高,因此是一种较为实用和有效     

数控进给伺服系统摩擦补偿控制仿真

针对伺服系统传动机构中摩擦对系统控制精度的影响问题,提出了一种遗传算法与模糊控制复合方法.建立了Stribeck+静摩擦力模型,设计了一种基于遗传算法的模糊补偿控制器,并将模糊补偿控制器应用于伺服系统中进行仿真.仿真结果表明,此方法不仅可有效抑制摩擦力对数控进给伺服系统的非线性作用及系统的低速爬行现象,而且可提高进给伺服系统的动态性能.采用不同的初始控制规则进行分析后发现,设置的初始值对遗传算法的收敛速度和系统的摩擦补偿均具有良好效果.     

Model-based parameter identification of comprehensive friction behaviors for giant forging press

A new experimental apparatus was set up to investigate the actual fi-iction characteristics on the basis of speed control of the serve system.A modified friction model was proposed due to real time varying deformation resistance.The approach to identify the parameters of comprehensive friction behaviors based on the modified model was proposed and applied to the forging press.The impacts on parameters which the external load had were also investigated.The results show that friction force decreases with velocity in the low velocity regime whereas the friction force increases with the velocity in the high velocity regime under no external load.It is also shown that the Coulomb friction force,the maximum static friction force and the vicious friction coefficient change linearly with the external load taking the velocity at which the magnitude of the steady state friction force becomes minimum as the critical velocity.     

基于干扰观测器的惯性平台摩擦补偿方法

为研究摩擦对惯性平台跟踪性能的影响,根据摩擦力的Stribeck曲线建立了平台伺服系统中的摩擦力矩仿真模型,并提出用干扰观测器的方法来补偿其干扰.在介绍了干扰观测器的设计方法的基础上,建立了带有摩擦干扰的平台跟踪系统的控制模型.仿真结果表明,干扰观测器对摩擦干扰力矩有很好的补偿作用,使惯性平台的跟踪精度和抗干扰能力得到了提高.     

基于LuGre模型的气缸摩擦力特性研究

为满足高精度电-气比例/伺服控制系统设计时基于模型的摩擦力补偿需要,基于LuGre模型建立气缸的动态摩擦模型.搭建了一个新型的气缸摩擦力测试台,通过测量活塞匀速运动时摩擦力与活塞速度的关系辨识了模型中的静态参数;针对在时域估计模型动态参数存在诸多困难,提出将活塞的运动方程在平衡点附近线性化,通过测量活塞位移和驱动力之间的频率响应函数来间接估计动态参数值.测试了气缸在不同腔内压力下的摩擦力特性,结果表明：库伦摩擦力、最大静摩擦力和黏性摩擦系数与压力近似成线性关系,而Stribeck速度和模型动态参数基本不受气缸两腔压力变化影响.正弦变化力激励下的活塞位移计算曲线和实验结果对比表明,参数估计准确,该模型能很好的描述气缸的摩擦力特性.     

Control algorithm for vehicle height adjustable system of hydro-pneumatic suspension based on LuGre model

In order to control the vehicle body position precisely, 1/4 nonlinear mathematical model of hydro-pneumatic suspension is established, and the influence of the frictional force in a hydraulic cylinder is analyzed. The friction characteristics are described based on the LuGre model when the piston of a hydraulic actuator is operated at a low speed. Due to the fact parameters of the friction model are effected by the system condition, an adaptive friction compensation (AFC) controller is designed through the Backstepping method, and a dual-observer has been implemented to estimate the friction state. The global asymptotic convergence of a closed-loop system is proven by the Lyapunov theorem. The simulation results show that the positional accuracy of the adaptive friction compensation yiedls a significant improvement in the vehicle height adjustment as compared to the PID control, demonstrating the effectiveness of the adaptive fiction compensation method in the vehicle height adjustable system of the hydro-pneumatic suspension.     

板球系统的非线性摩擦补偿控制

为提高位置控制精度,提出了基于非线性观测器的板球系统摩擦非线性补偿控制方法。在扩展的系统状态空间中构造了非线性状态观测器估计摩擦力。由输入输出精确反馈线性化和最优控制理论设计了考虑摩擦补偿的镇定位置控制器。根据变结构控制理论设计了可精确消除摩擦的跟踪位置控制器。仿真结果说明了上述摩擦非线性补偿控制方法的可行性。镇定控制实验表明非线性摩擦补偿控制明显减小了稳态位置偏差。跟踪控制实验表明摩擦补偿控制明显提高了轨迹跟踪控制精度。     

直线驱动工作台系统中摩擦扰动补偿器设计

由于直线驱动的工作台滑动面存在着接触运动,所以滑动面之间不可避免地存在着非线性摩探。它严重影响着高精度微进给的特性。通过设计扰动观测器补偿非静态摩探。用其补偿摩探对系统的影响,可以得到精确的速度／位置控制,并且没有由于速度转换时的零速度间隙。     

无刷直流电动机系统的一种摩擦补偿方法研究

针对无刷直流电动机系统的非线性数学模型特点,提出了一种简单的摩擦补偿方法。该方法首先利用输入输出线性化方法将原系统模型转化为一种简单的线性模型,然后给出一种非线性摩擦估计器实时估计系统中的库仑摩擦值,最后利用摩擦前馈补偿方法对其进行补偿。仿真结果表明该方法可以有产地抑制无刷直流电动机系统中的摩擦影响。     

被动力伺服系统摩擦非线性控制

提出了一种用于补偿力伺服系统中摩擦力作用的基于非精确模型的非线性控制器。摩擦力是影响系统性能的一个重要因素,针对摩擦非线性对被动式电液力伺服系统跟踪性能的影响,提出一种用于力控制系统摩擦非线性补偿控制器。其基于Lyapunov稳定性定理,不需摩擦力矩的准确模型,只需参数上界值,是一种基于非精确摩擦模型的非线性控制器。仿真与实验结果表明:与一般的PID控制相比,该控制器能更好地消除摩擦非线性的影响。此算法对力控制系统的摩擦力抑制具有一定的借鉴作用。     

Effect of friction heat on tribological behavior of M2 steel against GCr15 steel in dry sliding systems

The tribological behavior depends significantly on friction heat under high sliding velocity. Many factors influence the conduction rate of friction heat, such as thermophysical properties of the pairs, the formation components of interface-film, environ- ment mediums, etc. Through theoretical and experimental studies on surface temperature, the heat partition approaches have been applied to the pairs of M2 steel against GCr15 steel to compare and discuss their tribological behavior in dry sliding contact. The re- sults indicate that the values of the contact pressure have little effect on the heat partition at a high sliding velocity of 40 m/s. Fur- thermore, the degree of correlation between the dynamic temperature and friction coefficient is obvious, and the correlation degree of parameters increases as the pressure grows. A close correlation exists among the temperatures measured from different points of the pin specimen. At last, X-ray diffraction analysis denotes that the carbides of secondary M6C are separated out during the process of friction.