基于SIRM的倒立摆模糊控制器

探讨了倒立摆控制中的一些方法和应用，指出了通常模糊控制规则过于复杂的问题，设计了基于SIRM(单输入规则模块)的模糊控制器，既解决了模糊控制规则复杂的问题，又实现了倒立摆的快速稳定。最后，通过仿真验证了控制系统的效果。     

Stabilization and tracking control of X-Z inverted pendulum with sliding-mode control

X-Z inverted pendulum is a new kind of inverted pendulum which can move with the combination of the vertical and horizontal forces. Through a new transformation, the X-Z inverted pendulum is decomposed into three simple models. Based on the simple models, sliding-mode control is applied to stabilization and tracking control of the inverted pendulum. The performance of the sliding mode control is compared with that of the PID control. Simulation results show that the design scheme of sliding-mode control is effective for the stabilization and tracking control of the X-Z inverted pendulum.     

自冷却摩擦式缓降器能量耗散研究

根据自冷却摩擦式缓降器的工作原理及结构特点,分析了运动传递过程中的能量耗散过程.应用工程力学的方法,分别推导出缓降器运动传递过程中各个阶段的能量耗散公式.通过实例及实验验证,得到了计算公式中的相关参数的确定方法.为进一步研究缓降器的性能提供了理论支持.     

Mechanism of energy dissipation in mechanical system with dry friction

Determination of the energy dissipative mechanism in a mechanical system composed of two elastic structures in dry contact is presented. The analysis is based on the measurement of displacement ratio of the contacting elastic structures as a function of frequency due to light impulse excitation at a single point on any of the two elastic structures. The theoretical analysis depends on a very simple model of a two-degree-of-freedom system where two solid friction models are adopted in the analysis of the mathematical model. Several experiments are presented to illustrate the dominant friction mechanism of contacting surfaces within the micro slip regime in a frequency range of oscillation up to 400 Hz. It was shown experimentally that the solid friction model behaves in a way that is described as structural (hysteretic) damping. In other words, the energy dissipated due to dry friction during micro slip regime does not depend on the relative velocity between the two contacting surfaces but it is proportional to their relative displacements. The determination of the contact stiffness and damping loss factor in addition to their variation with the applied normal load was also shown.     

The relationship between AE and dissipation energy for fretting wear

This paper describes the behavior of acoustic emission (AE), especially the correlation between the AE output and the dissipation energy under the fretting conditions. Fretting tests are conducted with a ball contacting with a flat disc in air. The specimens used are a bearing steel for a ball, and a bearing steel or an aluminum alloy for a flat disc. The results show that the behavior of the AE output and the dissipation energy during each fretting cycle is not so similar to each other throughout the test, but the total AE root-mean-square and the total dissipated energy during the test have a good correlation between them.     

Reducing the stabilizing control order for a double inverted pendulum

The problem of stabilization of an unstable plant by a reduced-order single-channel controller is considered. The possibility of compensating small deviations of a double inverted pendulum on a cart by acting on the cart is studied. An algebraic method for finding the extreme locations of the poles through the construction of root simplexes is proposed. Using this, the Hurwitz stability boundaries for various reduced-order controllers are calculated. It is shown that robust stabilization of the pendulum system in the class of reduced-order controllers is impossible.     

Vibroplatform modeling with allowance for tribological aspects

A vibroplatform model has been presented, which is used in industry for the separation and transportation of granular materials. An analysis of the results of theoretical and experimental studies of the coefficient of friction between the screen and sand granules has been carried out in real operating conditions of the vibroplatform.     

Long stroke energy dissipation in splitting tubes

A passive crashworthy system that dissipates impact energy by fracture and plastic deformation of metal tubes is analysed. The energy dissipating component is a square tube that is pressed axially against a die where it splits at the corners and curls outward. Experiments on the effect of die radius have shown that a remarkably constant force causes this rate-independent deformation in a dural tube. Tubes which both split and curl can be designed for energy absorbing systems requiring large stroke to length ratio and good specific energy absorption.     

Atomic-scale study of friction and energy dissipation

This paper presents an analysis of the interaction energy and various forces between two surfaces, and the microscopic study of friction. Atomic-scale simulations of dry sliding friction and boundary lubrication are based on the classical molecular dynamics (CMD) calculations using realistic empirical potentials. The dry sliding of a single metal asperity on an incommensurate substrate surface exhibits a quasi-periodic variation of the lateral force with two different stick-slip stage involving two structural transformation followed by a wear. The contact area of the asperity increases discontinuously with increasing normal force. Xe atoms placed between two atomically flat Ni surfaces screen the Ni-Ni interaction, decrease the corrugation of the potential energy as well as the friction force at submonolayer coverage. We present a phononic model of energy dissipation from an asperity to the substrates.     

Linear control of the flywheel inverted pendulum

The flywheel inverted pendulum is an underactuated mechanical system with a nonlinear model but admitting a linear approximation around the unstable equilibrium point in the upper position. Although underactuated systems usually require nonlinear controllers, the easy tuning and understanding of linear controllers make them more attractive for designers and final users. In a recent paper, a simple PID controller was proposed by the authors, leading to an internally unstable controlled plant. To achieve global stability, two options are developed here: first by introducing an internal stabilizing controller and second by replacing the PID controller by an observer-based state feedback control. Simulation and experimental results show the effectiveness of the design.     

Measurement of strain rate sensitivity of aluminium foams for energy dissipation

In this paper the structural performance of aluminium alloy foams have been investigated under both static and dynamic compression loads. Three foam typologies (M-PORE, CYMAT, SCHUNK) in a wide range of density (from 0.14 to 0.75 g/cm³), made by means of different process-routes (melt gas injection, powder metallurgy, investment casting) have been analysed. Foams microstructural characterization has been carried out through morphometric measurements by means of Scanning Electron Microscopy (SEM) and Computed Tomography (CT) and subsequent digital image processing in order to determine average cells size and cell distributions on different section planes. The experimental study aims to assess the strain rate sensitivity and energy absorption capability of commercially available metal foams and to point out the correlation between the mechanical behaviour and the physical and geometrical properties of the foam. It has been found that the specific energy dissipation of foams with similar density can be quite different: for the same volume of foam, average values of 1770, 1780 and 5590 J/kg at 50% nominal compression have been measured on M-PORE (0.19 g/cm³), CYMAT (0.28 g/cm³) and SCHUNK (0.28 g/cm³) foams, respectively. Impact tests showed that the dependence of the plateau stress on strain rate could be considered negligible for M-PORE and CYMAT foams while it is quite remarkable for SCHUNK foams. Moreover, it was found that the peak stress of CYMAT foams has a quite large sensitivity on the loading rate.     

Predictor-based control for an inverted pendulum subject to networked time delay

The inverted pendulum is considered as a special class of underactuated mechanical systems with two degrees of freedom and a single control input. This mechanical configuration allows to transform the underactuated system into a nonlinear system that is referred to as the normal form, whose control design techniques for stabilization are well known. In the presence of time delays, these control techniques may result in inadequate behavior and may even cause finite escape time in the controlled system. In this paper, a constructive method is presented to design a controller for an inverted pendulum characterized by a time-delayed balance control. First, the partial feedback linearization control for the inverted pendulum is modified and coupled with a state predictor to compensate for the delay. Several coordinate transformations are processed to transform the estimated partial linearized system into an upper-triangular form. Second, nested saturation and backstepping techniques are combined to derive the control law of the transformed system that would complete the design of the whole control input. The effectiveness of the proposed technique is illustrated by numerical simulations.     

Analysis of frictional energy dissipation on an annular surface with harmonic loading

Metallic mating surfaces in structural joints offer a good source of frictional energy dissipation resulting in a damped dynamic structural response. This paper reports the results of experiments where the energy dissipation per cycle occurring at a preloaded flat metallic annular interface subjected to cyclic tangential forces is measured. The effects of certain pertinent joint variables on this frictional energy dissipation are investigated by the application of Response Surface Methodology. A central composite rotatable design was utilized for developing empirical expressions for energy loss. The methodology presented suggests a useful technique for tribological research.     

Hydraulic jump and energy dissipation downstream stepped weir

Hydraulic jump can be defined as a sudden change or rise of water level because of changing the channel slope from steep to mild combined turbulent flow. This can be used for energy dissipation to reduce flow energy downstream hydraulic structure. Recent studies dealt with energy dissipation downstream hydraulic structures such as stepped weir by changing water level upstream and downstream to reduce flow energy. In this study, the focus was placed on the hydraulic jump formation downstream stepped weir and its characteristics, as well as used it as energy dissipation to reduce the residual energy that will be dissipated on stepped weir. 27 stepped weir models were tested with three different heights, slopes as well as changed number of steps for all models. It was found that the energy dissipation increased by increasing weir slope, the number of steps, and decreasing the height weir, by 20%, 20.6%, 21.8% respectively. It was also found that the energy dissipation increased when the hydraulic jump length increased, but this was not economy. The best model for energy dissipation in this study was that have lower height and greater slope and steps number. This model gives lower value of hydraulic jump length; this is more economy as it reduces the length of stilling basin which is reduces the cost of its construction downstream stepped weir or stepped spillway.     

倒立摆控制方法的比较研究

倒立摆系统作为典型的控制对象,不仅对控制设计提出了难题,同时为很多先进控制方法的研究和应用提供了一个很好的实验平台。该文分别用PID控制法、优化控制策略的LQR及极点配置法等3种方法对单级倒立摆系统进行控制,并利用MATLAB仿真对3种控制算法的效果进行了对比,讨论了3种方法之间的优缺点。仿真实验表明:PID法与极点配置法具有较好的瞬态性,LQR法具有较好的鲁棒性。在实际应用中,可根据控制系统的具体指标要求选择适合的控制方法,具有一定的指导意义。     

Error calculation for corrective machining with allowance requirements

Electroforming copper from the copper sulfate baths or the pyrophosphate baths is one of commonly used methods for manufacturing electro-discharge machining (EDM) tool electrode, in particular for the fabrication of micro- and meso-scale tool electrodes with complex cross-section, but few literature on the electrode-wear performance of electroformed copper electrode has been available until today. To better select copper tool electrode materials, the wear resistance of the macroscopic and tiny copper tool electrodes deposited from the copper sulfate baths and the pyrophosphate baths were investigated comparatively with the same micro-EDM parameters. The optimal electrodeposition parameters in which the deposited copper had the lowest electrode-wear ratio were first obtained from the two baths, respectively. And then, the wear resistance of the micro-featured copper tool electrode electroformed using the optimal deposition conditions from the two baths were evaluated comparatively. Experimental investigations showed that, both at the macro-scale level and at the micro-scale level, the copper tool electrode electroformed from the pyrophosphate baths (the smallest electrode-wear ratio was 10% for the macro-electrode and 12.8% for the micro-electrode) exhibited better wear resistance than that deposited from the copper sulfate baths (the smallest electrode-wear ratio was 11.95% for the macro-electrode and 17.3% for the micro-electrode).     

单级倒立摆模糊控制研究

单级倒立摆系统包括四个输入变量,经典模糊控制算法同时对四个输入变量进行模糊推理,容易造成模糊规则数过多。根据增加模糊控制器个数来减少输入变量维数的思想,设计了串联模糊控制器和并联模糊控制器,有效控制了单级倒立摆系统的运动,但稳定时间和稳态误差不够理想。故提出了一种基于单一输入规则群(SIRMs)动态加权模糊推理模型的模糊控制器,实现了单级倒立摆的稳定控制,该控制器通过引入输入变量重要度因子,保证摆杆控制优先于小车控制。实时控制实验表明:系统跟踪速度快,具有较强的鲁棒性和良好的动静态特性,验证了该模糊控制器的有效性。     

单级倒立摆的两种控制方法的仿真研究

针对多变量、非线性、强耦合性的倒立摆系统,运用牛顿-欧拉方法建立了倒立摆的数学模型。然后对该模型分别进行LQR控制和模糊控制,并在MATLAB环境下进行仿真,其对比结果对该方向的研究具有理论指导意义。     

An improved backstepping design for the control of an underactuated inverted pendulum

This paper presents an improved backstepping design (IBD) for the control of a new type of underactuated inverted pendulum. The characteristics and possible applications of the inverted pendulum are presented. Nonlinear models and a linearized model are given for a straightforward explanation of its dynamic features. The conventional backstepping design (CBD) is revisited for this plant. The IBD is then used to reduce the complexity of the design and to allow the specification of transient characteristics, to improve the system’s performance. Experimental studies are conducted to investigate the effectiveness of the proposed scheme.