共查询到20条相似文献,搜索用时 625 毫秒
1.
复杂接触运动下非线性摩擦力的求解 总被引:1,自引:0,他引:1
提出了复杂接触运动下求解接触非线性摩擦力的数值轨迹跟踪方法,利用该方法对几种复杂接触运动下的非线性摩擦力进行了计算。计算结果表明:数值方法在分析二维接触椭圆运动时可以得到更准确的结果;计算接触面摩擦力时不能忽略法向运动与切向运动之间的相位差,该相位差对接触状态的转变、摩擦力的大小以及迟滞回线的形状都有很大的影响;对于接触面的三维运动,必须同时考虑法向运动与接触面内两个方向切向运动之间的耦合;数值轨迹跟踪方法可以方便地求解一维、二维以及三维接触运动下的非线性摩擦力,为求解带干摩擦阻尼结构的动态响应提供了一种实用算法。 相似文献
2.
High-precision magnetic levitation stage for photolithography 总被引:5,自引:0,他引:5
In this paper, we present a high-precision magnetic levitation (maglev) stage for photolithography in semiconductor manufacturing. This stage is the world’s first maglev stage that provides fine six-degree-of-freedom motion controls and realizes large (50 mm × 50 mm) planar motions with only a single magnetically levitated moving part. The key element of this stage is a linear motor capable of providing forces in both suspension and translation without contact. The advantage of such a stage is that the mechanical design is far simpler than competing conventional approaches and, thus, promises faster dynamic response and higher mechanical reliability. The stage operates with a positioning noise as low as 5 nm rms in x and y, and acceleration capabilities in excess of 1 g (10 m/s2). We demonstrate the utility of this stage for next-generation photolithography or in other high-precision motion control applications. 相似文献
3.
As permanent-magnet motors and generators produce torque, vibration occurs through the small air gap due to the alternating magnetic forces created by the rotating permanent magnets and the current switching of the coils. The magnetic force can be calculated from the flux density by finite element methods and the Maxwell stress tensor in cylindrical coordinates. The transition of the magnetic force with the rotation of rotor and the commutation of current, was analyzed by assuming the quasi static magnetic field. The cogging and the commutating torques were also investigated by integrating the magnetic shear force in a small air-gap. In addition, the characteristics of these forces and torques were also investigated by multi-dimensional spectral analysis, so that this paper makes it possible to predict the frequency spectrum of magnetic force and the torque in a brushless do motor. 相似文献
4.
BAO Gang SUN Zhongsheng WANG Zuwen Pneumatic Center Harbin Institute of Technology Harbin China 《机械工程学报(英文版)》2006,19(4):588-593
An exoskeleton force feedback dataglove is developed, which uses the pneumatic artificial muscles as actuators. On the basis of the simplified hand model, the motion equation is deduced according to the theory of Denavit-Hartenberg. The model of the equivalent contact forces exerted by the object on the finger is proposed. By the principle of virtual work, the static equilibrium of finger is established. The force Jacobian matrix of finger is calculated, and then the joint torques of the finger when grasping objects are obtained. The theory and structure of the force feedback datagolve are introduced. Based on the theory of motion stabilization of four-bar linkage, the flexion angles of joints are measured. The torques on finger joints caused by the output forces of pneumatic artificial muscles are calculated. The output forces of pneumatic artificial muscle, whose values are controlled by its inner pressure, can be calculated by the joint torques of the finger when grasping objects. The arms of force, driving torques and the needed output forces of pneumatic muscle are calculated for each joint of the index finger. The criterion of output force of pneumatic muscle is given. 相似文献
5.
为获得高精度大行程快速刀具伺服(Long-range fast tool servo,LFTS)系统,以柔性铰链为运动导向机构,提出一种基于洛伦兹电磁力与压电混合串联驱动的LFTS系统构成策略。对于该混合驱动,基于洛伦兹力的音圈电机用于实现大行程运动,而高频响压电则对其进行高精度动态补偿。针对压电驱动,为提高系统输出刚度及寄生运动抑制能力,提出一种改进的具有完全对称构型的桥式柔性放大机构。两种驱动的垂直布置构型及压电驱动的完全对称性有效降低了驱动间动力学耦合。基于试凑法和智能优化算法,结合机-电-磁理论模型分别优化获得了音圈电机及压电驱动系统关键参数,并采用有限元仿真验证了设计的正确性。为获得高精度运动跟踪,提出音圈电机开环逆动力学控制及压电驱动闭环补偿LFTS整体运动误差的控制策略,借助所辨识系统动力学模型最优设计了相应控制器。最终,通过试验样机开闭环性能测试,验证了系统设计与控制策略的有效性。 相似文献
6.
Torque Variations in Instrument Ball Bearings 总被引:1,自引:0,他引:1
E. P. Kingsbury 《摩擦学汇刊》2013,56(4):435-441
Disturbances in the torques and motions in angular contact instrument ball bearing pairs are described and analyzed. Among others, a motion of the ball retainer, analogous to dry friction whirl, is attributed to frictional coupling between balls and retainer, and an interaction between bearings, resulting in several low frequency perturbations, is explained in terms of ball errors. Experimental confirmation is obtained. 相似文献
7.
The modal characteristics of constrained multibody systems undergoing constant accelerated motions are investigated in this
paper. Relative coordinates are employed to derive the equations of motion, which are generally nonlinear in terms of the
coordinates. The dynamic equilibrium position of a constrained multibody system needs to be obtained from the nonlinear equations
of motion, which are then linearized at the dynamic equilibrium position. The mass and the stiffness matrices for the modal
analysis can be obtained from the linearized equations of motion. To verify the effectiveness and the accuracy of the proposed
method, two numerical examples are solved and the results obtained by using the proposed method are compared with those obtained
by analytical and other numerical methods. The proposed method is found to be accurate as well as effective in predicting
the modal characteristics of constrained multibody systems undergoing constant accelerated motions. 相似文献
8.
Kook-Jin Choi Dae Sun Hong 《International Journal of Precision Engineering and Manufacturing》2010,11(3):381-390
This study proposes a method of real-time posture optimization of humanoid robots using a genetic algorithm and neural network.
Here, the motion of a humanoid robot pushing an object is considered. When the robot starts pushing the object, the palms
of its hands and the soles of its feet are assumed to be fixed on the object and on the ground, respectively, and they sense
the reaction force from those surfaces. The reaction force results in changes of torques in the joints. This study determines
an optimized posture using a genetic algorithm such that either the torques are evenly distributed over all joints or the
torque of the weakest joint is rapidly reduced. Several different optimized postures are then generated by varying the reaction
forces at the palms and the soles. The data is used as training patterns for a multilayer perceptron neural network with a
back-propagation learning algorithm. Using the trained neural network, the humanoid robot can find the optimal posture for
different reaction forces in real time. Several simulations were conducted to confirm the effectiveness of the proposed method.
The simulation results showed that the proposed method can be used for real-time posture optimization of humanoid robots. 相似文献
9.
Optimization of throwing motion planning for whole-body humanoid mechanism: Sidearm and maximum distance 总被引:1,自引:0,他引:1
Joo H. Kim 《Mechanism and Machine Theory》2011,46(4):438-453
Throwing is a rapid coordinated movement with high configuration and actuation redundancies. Based on a previous work, this paper advances a numerical framework that optimizes the throwing motions and generates the associated dynamic features for a whole-body humanoid mechanism. To generate physically feasible throwing motions in a fully predictive manner, rigorous dynamic models, such as actuation, biped balance based on Zero-Moment Point (ZMP), and ground reaction loads, are associated with the constraints. The algorithm outputs include the motion, required actuator torques, release parameters, and object projectile. Realistic human-like motions of sidearm and maximum distance throwing are generated as optimized solutions, which demonstrate valid kinematic and dynamic cause-effect relations. The sidearm throw shows better optimality than the overarm throw in terms of actuator torques under the proposed mechanical model; it is characterized by the unique hand trajectory and effective utilization of torso axial rotation. The maximum distance throw is associated with active movement of the arm and torso with larger ranges of motion; it is the release height and speed that increase accordingly. 相似文献
10.
抓持接触力的子空间分解表示 总被引:2,自引:1,他引:1
研究了机器人灵巧手抓持物体时手指与物体间接触力的性质。通过将接触力空间分解成四个子空间,给出了接触力的一般表达式。该式即适用于灵巧抓持,也适用于退化抓持。在退化抓持情况下,接触力的某些分量可能不能由关节力矩提供,成为被动力。该法可以将这些被动力分量识别和分解出来,并进而将接触力表示成被抓物体所受外力和手指关节力矩的显函数。从此表达式出发对接触力进行优化可以保证所求接触力能够由关节力矩提供。给出了两个力分解的数值算例。 相似文献
11.
In dealing with the dynamics of a flexible body, the rigid-body motions and elastic vibrations are analyzed separately. However, rigidbody motions cause vibrations, and elastic vibrations affect rigid-body motions, indicating the inherent coupling between rigid-body motions and elastic vibrations. The coupled equations of motion for a flexible body can be derived by means of Lagrange’s equations in terms of quasi-coordinates. The resulting equations of motion are hybrid and nonlinear. This paper proposes a unified approach for the equations of motion for a flexible body based on the perturbation method and the Lagrange’s equations of motion in terms of quasicoordinates and Euler parameters to analyze a more general case maneuvering. The resulting equations consist of zero-order nonlinear equations of motion which depict rigid-body motions and first-order time-varying linear equations of motion which depict perturbed rigid-body motions and elastic vibration. Hence, the input-shaped maneuvering can be applied to the zero-order equation considering the induced vibrations. Since the input-shaped maneuvering alone cannot achieve vibration suppression, the vibration suppression controller combined with the input-shaped maneuvering is proposed in this study. As a numerical example, a hub with elastic appendages is considered. Numerical results show that the unified modeling approach proposed in this paper is effective in numerical simulation and control design. 相似文献
12.
Baer S Andrade MA Esen C Adamowski JC Schweiger G Ostendorf A 《The Review of scientific instruments》2011,82(10):105111
The use of acoustic levitation in the fields of analytical chemistry and in the containerless processing of materials requires a good stability of the levitated particle. However, spontaneous oscillations and rotation of the levitated particle have been reported in literature, which can reduce the applicability of the acoustic levitation technique. Aiming to reduce the particle oscillations, this paper presents the analysis of the particle stability in a new acoustic levitator device. The new acoustic levitator consists of a piezoelectric transducer with a concave radiating surface and a concave reflector. The analysis is conducted by determining numerically the axial and lateral forces that act on the levitated object and by measuring the oscillations of a sphere particle by a laser Doppler vibrometer. It is shown that the new levitator design allows to increase the lateral forces and reduce significantly the lateral oscillations of the levitated object. 相似文献
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深入研究了高频脉冲交流环节逆变器电路拓扑族及其双极性移相控制策略.借助周波变换器换流重叠和输出滤波电感电流极性选择,该双极性移相控制策略实现了变压器漏感能量和滤波电感电流的自然换流;解决了这类逆变器固有的电压过冲和换流重叠期间周波变换器的环流现象;实现了逆变桥功率器件的ZVS开关和周波变换器功率器件的ZCS开关.仿真与原理试验结果均证实了这种双极性移相控制策略的可行性和理论分析的正确性. 相似文献
15.
Quanliang Cao Liang Li Zhipeng Lai Zhongyu Zhou Qi Xiong Xiao Zhang Xiaotao Han 《The International Journal of Advanced Manufacturing Technology》2014,74(1-4):361-368
This paper presents a simple and efficient method for the analysis of dynamic behavior of the workpiece in the electromagnetic forming process. A two-dimensional (2D) axisymmetric finite element model with the equations of electrical equivalent circuit, electromagnetic field, and mechanical field has been developed for calculating the discharge currents through the forming coil, the magnetic forces acting on the workpiece, and the plastic deformation of the workpiece. By considering the effects of the sheet geometry and velocity on the above parameters, the method realizes the full coupling between the electromagnetic fields and the workpiece deformation, which should be more accurate than the existing loose coupling and sequential coupling simulation methods. 相似文献
16.
Uhn Joo Na 《Journal of Mechanical Science and Technology》2005,19(3):731-742
A magnetic bearing even with multiple coil failure can produce the same decoupled magnetic forces as those before failure
if the lemaining coil currents are properly redistributed This faulttolerant, force invariance control can be achieved with
simply leplacing the distribution matrix with the appiopnate one shortly after coils fail, without modifying feedback control
law The distribution gain matrix that satisfies the necessary constraint conditions of decoupling linearized magnetic foices
is determined with the Lagrange Multiplier optimization method 相似文献
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In order to improve the reliability and reduce power consumption of the high speed BLDC motor system, this paper presents a model free adaptive control (MFAC) based position sensorless drive with only a dc-link current sensor. The initial commutation points are obtained by detecting the phase of EMF zero-crossing point and then delaying 30 electrical degrees. According to the commutation error caused by the low pass filter (LPF) and other factors, the relationship between commutation error angle and dc-link current is analyzed, a corresponding MFAC based control method is proposed, and the commutation error can be corrected by the controller in real time. Both the simulation and experimental results show that the proposed correction method can achieve ideal commutation effect within the entire operating speed range. 相似文献