磁力轴承刚度阻尼特性研究

叙述了磁力轴承系统的结构及刚度和阻尼特性的基本理论。分析了磁力轴承系统的刚度阻尼特性与系统结构参数及其控制器特性之间的关系，同时分析采用了PID控制的磁力轴承刚度阻尼与控制系统各参数之间的关系，提出一种简便的PID参数设计方法。     

基于结构动态特性的磁力轴承转子系统的设计

分析了径向磁力轴承动力学特性,计算了磁力轴承的刚度系数和阻尼系数。在此基础上,对磁力轴承的转子结构动态特性进行了有限元分析。提出了基于结构动态特性的磁力轴承转子控制系统的设计方法。     

主动磁力轴承非线性动刚度特性研究

通过对主动磁力轴承转子系统非线性动刚度的研究,揭示了系统控制器参数、机械结构参数与动刚度之间的耦合关系,并结合PID控制规律,研究了磁力轴承非线性动刚度的频域特性.研究表明,系统在低频与高频段具有较高的支承刚度,而中频段刚度较低,刚度幅频特性呈"浴盆"状.在系统稳定区域内,改变控制器参数可以灵活地设计系统的动刚度.     

自调整PID控制算法及其在磁悬浮平台中的应用

中建立了电磁悬浮平台的数学模型,提出了自调整PID算法。分析了系统的刚度阻尼与控制系统之间的关系,并利用它们之间的关系和稳态误差确定了PID参数。实验结果表明,该系统具有很好的刚度阻尼特性,鲁棒性能好。     

磁力轴承转子系统非线性支承特性的研究

通过对磁力轴承非线性支承力特性的分析,可以看出控制器参数与支承特性之间有非常强的非线性耦合关系。虽然其支承的刚度和阻尼都能够通过改变控制器参数进行调整,但控制器参数的选择受非线性因素的影响较大。当比例增益越大,则在转子平衡点处的线性刚度就越大,能提供的最大支承力也越大,但支承实现正刚度的转子位移区间越小,系统稳定的转子位移区间就越小。通过对主动磁力轴承转子系统非线性支承特性的研究,揭示了控制器结构参数、机械结构参数与支承特性之间的耦合关系。     

磁气负载比对箔片-磁力混合轴承支承特性及转子动力学特性的影响

箔片-磁力混合轴承是一种能降低箔片轴承起飞前的摩擦损耗且可改善磁轴承高速时的承载和动力学性能的新型高性能主动控制型轴承。提出了一种箔片-磁力混合轴承的设计方法,设计并搭建箔片-磁力混合轴承支承特性实验台和箔片-磁力混合轴承转子实验台,实验探究了磁气负载比(即气体箔片轴承和主动磁轴承之间的载荷分配比)对箔片-磁力混合轴承支承特性和转子动力学特性的影响。实验结果表明：箔片-磁力混合轴承比箔片轴承的总体静态刚度和刚度变化率有所提高。箔片-磁力混合轴承结构刚度随频率的提高而增大,等效黏性阻尼随频率的提高呈现先降后增的趋势。此外,合适的负载比可以降低起飞转速,改善摩擦损耗,抑制次频振,有利于提高转子的高速稳定性。     

主动磁力轴承支承刚度特性研究

以单自由度磁力轴承为研究对象,建立非线性支承力模型,通过对磁力轴承非线性支承力特性的分析,揭示出磁力轴承支承刚度与控制器参数之间的非线性关系,对磁力轴承结构设计以及控制器的设计具有指导作用.基于非线性支承力模型和线性支承力模型设计不同的控制器,对磁力轴承转子系统进行刚度试验,结果表明,基于非线性刚度模型设计的控制器具有较好的稳定性和较高的刚度,并满足系统的回转精度要求.     

电磁轴承刚度阻尼自动测试

针对电磁轴承刚度阻尼难以测量的问题,设计一套电磁轴承刚度阻尼测试系统,实现电磁轴承刚度、阻尼的自动测量.该系统激振器由自行研制的LabVIEW测试系统产生,电磁轴承传感器作为拾振器,自行研制的测量分析系统作为测量分析工具.给出电磁轴承的刚度和阻尼测量结果.根据本系统获得的电磁轴承支承转子的刚度、阻尼特性,对控制器的优化设计以及转子模型的优化设计有一定的指导意义.由于电磁轴承具有可控刚度和阻尼特性,因此可利用等效刚度和等效阻尼概念选择控制系统参数,简化设计过程.对实验室的样机台架进行具体分析,证实这种方法可行.分析结果还表明,若控制参数选择合理,将获得令人满意的减振效果.     

一种磁悬浮离心式心脏泵刚度与阻尼特性分析

针对一种磁悬浮离心式心脏泵系统的动态特性,需要分析其刚度与阻尼。为此,分析了径向永磁轴承和开关磁阻电机的径向力学特性,得到磁悬浮转子径向运动方程和控制系统框图; 并结合PD控制器,推导出系统径向刚度与阻尼数学表达式,最后通过实例仿真,得到径向刚度与阻尼特性曲线。研究表明,比例和滤波环节对系统动刚度、阻尼比和固有频率均有显著影响,且在低频段,微分系数与阻尼比近似成正比关系。上述研究为磁悬浮离心式心脏泵控制系统的设计和磁悬浮转子径向位移控制提供理论指导。     

电磁轴承刚度与阻尼特性的非线性研究

刚度与阻尼特性是电磁轴承重要的性能指标。对电磁轴承刚度与阻尼特性进行了非线性研究,建立了储能飞轮转子系统径向电磁轴承的非线性模型,推导了非线性情况下电磁轴承刚度与阻尼的计算公式,分析了电磁轴承刚度与阻尼的非线性特性,以及控制因数对刚度与阻尼的影响。研究结果表明,增大比例因数,可以使电磁轴承的刚度减小,达到正刚度时的转子位移范围同时减小。通过研究同时确认,电磁轴承阻尼受控制因数的影响较小。     

Dynamic characteristics of the rotor in a magnetically suspended control moment gyroscope with active magnetic bearing and passive magnetic bearing

For a magnetically suspended control moment gyroscope, stiffness and damping of magnetic bearing will influence modal frequency of a rotor. In this paper the relationship between modal frequency and stiffness and damping has been investigated. The mathematic calculation model of axial passive magnetic bearing (PMB) stiffness is developed. And PID control based on internal model control is introduced into control of radial active magnetic bearing (AMB), considering the radial coupling of axial PMB, a mathematic calculation model of stiffness and damping of radial AMB is established. According to modal analysis, the relationship between modal frequency and modal shapes is achieved. Radial vibration frequency is mainly influenced by stiffness of radial AMB; however, when stiffness increases, radial vibration will disappear and a high frequency bending modal will appear. Stiffness of axial PMB mainly affects the axial vibration mode, which will turn into high-order bending modal. Axial PMB causes bigger influence on torsion modal of the rotor.     

未知传递函数情况下主动电磁悬浮系统支承特性在线测量

分析了主动电磁悬浮系统支承的等效刚度和阻尼的理论计算方法。从闭环系统的角度出发,提出了一种不依赖于系统传递函数的等效刚度和阻尼的在线测量方法。以PID控制为例进行对比实验,分析了控制参数、激振幅度和激振频率对主动电磁悬浮系统支承等效刚度和阻尼的影响。结果表明,所提出的测量方法能够实时在线地对主动电磁悬浮系统支承的等效刚度和阻尼进行准确识别。     

Parameter estimation and statistical analysis on frequency-dependent active control forces

The active control forces of an active magnetic bearing (AMB) system are known to be frequency dependent in nature. This is due to the frequency-dependent nature of the AMB system, i.e. time lags in sensors, digital signal processing, amplifiers, filters, and eddy current and hysteresis losses in the electromagnetic coils. The stiffness and damping coefficients of these control forces can be assumed to be linear for small limit of perturbations within the air gap. Numerous studies have also attempted to estimate these coefficients directly or indirectly without validating the model and verifying the results.This paper seeks to address these issues, by proposing a one-axis electromagnetic suspension system to simplify the measurement requirements and eliminate the possibility of control force cross-coupling capabilities. It also proposes an on-line frequency domain parameter estimation procedure with statistical information to provide a quantitative measure for model validation and results verification purposes. This would lead to a better understanding and a design platform for optimal vibration control scheme for suspended system. This is achieved by injecting Schroeder Phased Harmonic Sequences (SPHS), a multi-frequency test signal, to persistently excite all possible suspended system modes. By treating the system as a black box, the parameter estimation of the “actual” stiffness and damping coefficients in the frequency domain are realised experimentally. The digitally implemented PID controller also facilitated changes on the feedback gains, and this allowed numerous system response measurements with their corresponding estimated stiffness and damping coefficients.     

磁悬浮支承振动半主动控制设计与仿真

利用DSP作为控制算法的核心器件,搭建了半主动减振系统,并将其应用于双层隔振系统中。通过调节PID控制器参数,改变电磁力从而获得系统的最佳刚度和阻尼。针对磁悬浮支承双层隔振系统的非线性和工作过程的复杂性,利用Simulink在非线性控制系统领域的仿真优势,建立磁悬浮支承的数学模型,将模糊控制、神经元控制分别和PID控制相结合进行仿真对比,仿真实验表明,神经元PID控制的动态性能和稳定性最佳,为磁悬浮浮筏隔振系统进行变刚度变阻尼控制提供可遵循的依据。     

Force control compensation method with variable load stiffness and damping of the hydraulic drive unit force control system

Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit (HDU), and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this paper has positive compensation effects on the load characteristics variation, i.e., this method decreases the effects of the load characteristics variation on the force control performance and enhances the force control system robustness with the constant PID parameters, thereby, the online PID parameters tuning control method which is complex needs not be adopted. All the above research provides theoretical and experimental foundation for the force control method of the quadruped robot joints with high robustness.     

Unbalance vibratory displacement compensation for active magnetic bearings

As the dynamic stiffness of radial magnetic bearings is not big enough,when the rotor spins at high speed,unbalance displacement vibration phenomenon will be produced.The most effective way for reducing the displacement vibration is to enhance the radial magnetic bearing stiffness through increasing the control currents,but the suitable control currents are not easy to be provided,especially,to be provided in real time.To implement real time unbalance displacement vibration compensation,through analyzing active magnetic bearings(AMB) mathematical model,the existence of radial displacement runout is demonstrated.To restrain the runout,a new control scheme-adaptive iterative learning control(AILC) is proposed in view of rotor frequency periodic uncertainties during the startup process.The previous error signal is added into AILC learning law to enhance the convergence speed,and an impacting factor influenced by the rotor rotating frequency is introduced as learning output coefficient to improve the rotor control effects.As a feed-forward compensation controller,AILC can provide one unknown and perfect compensatory signal to make the rotor rotate around its geometric axis through power amplifier and radial magnetic bearings.To improve AMB closed-loop control system robust stability,one kind of incomplete differential PID feedback controller is adopted.The correctness of the AILC algorithm is validated by the simulation of AMB mathematical model adding AILC compensation algorithm through MATLAB soft.And the compensation for fixed rotational frequency is implemented in the actual AMB system.The simulation and experiment results show that the compensation scheme based on AILC algorithm as feed-forward compensation and PID algorithm as close-loop control can realize AMB system displacement minimum compensation at one fixed frequency,and improve the stability of the control system.The proposed research provides a new adaptive iterative learning control algorithm and control strategy for AMB displacement minimum compensation,and provides some references for time-varied displacement minimum compensation.     

System modeling and robust control of an AMB spindle : part II a robust controller design and its implementation

This paper discusses an entire procedure for a robust controller design and its implementation of an AMB (active magnetic bearing) spindle, which is part II of the papers presenting details of system modeling and robust control of an AMB spindle. Since there are various uncertainties in an AMB system and reliability is the most important factor for applications, robust control naturally gains attentions in this field. However, tight evaluations of various uncertainties based on experimental data and appropriate performance weightings for an AMB spindle are still ongoing research topics. In addition, there are few publications on experimental justification of a designed robust controller. In this paper, uncertainties for the AMB spindle are classified and described based on the measurement and identification results of part I, and an appropriate performance weighting scheme for the AMB spindle is developed. Then, a robust control is designed through the mixedμ synthesis based on the validated accurate nominal model of part I, and the robust controller is reduced considering its closed loop performance. The reduced robust controller is implemented and confirmed with measurements of closed-loop responses. The AMB spindle is operated up to 57,600 rpm and performance of the designed controller is compared with a benchmark PID controller through experiments. Experiments show that the robust controller offers higher stiffness and more efficient control of rigid modes than the benchmark PID controller.     

Identification of the dynamic parameters of active magnetic bearings based on the transfer matrix model updating method

The stiffness and damping coefficients of Active magnetic bearings (AMBs) have a great impact on the dynamics of a high-speed rotor AMB system, from its bending critical speed to the modes of its vibration and stability. To accurately obtain the stiffness and damping coefficients of AMBs, this study proposes a new identification approach based on the transfer matrix model updating method. By minimizing the error between the unbalance response calculated through the transfer matrix approach and the experimental measurements, the stiffness and damping coefficients are obtained using the simplex optimization algorithm based on the updating method of the model. According to the experimental data, we identify the parameters from 20 Hz to 260 Hz (1200 rpm to 15600 rpm). To verify the identified results, a finite element rotor AMBs model is created, and the theoretical unbalance response is predicted using the identified parameters. The theoretical unbalance responses closely coincide with the experimental measurements, indicating the effectiveness of the proposed method.     

基于主动磁轴承的切削颤振稳定性分析及控制

提出了基于主动磁轴承的铣削颤振主动控制技术。用有限元法分析了主动磁轴承等效刚度与等效阻尼对铣削稳定性区域的影响,并对铣削过程中的颤振进行了主动控制。结果表明:主动磁轴承的等效刚度能够改变电主轴转子的临界转速,但对铣削的临界切削宽度影响很小;相反,主动磁轴承的等效阻尼能够较大幅度地增大铣削的临界切削宽度,但对电主轴转子的临界转速影响不大。颤振的控制效果表明,调节主动磁轴承的等效刚度和等效阻尼能够减小铣削过程中颤振的振幅。