Air-bearing Simulator Research Articles

Dynamic equivalence conditions for an air-bearing simulator emulating scaled drag-free control dynamics

Dynamic equivalence conditions for an air-bearing simulator emulating scaled drag-free control dynamics

A distributed predictive formation control strategy for cyber-physical multi-agent systems under communication constraints

This paper focuses on the formation control problem under communication constraints for leader-follower cyber-physical multi-agent systems (CPMASs). The introduction of a leader-follower structure motivates the design of a distributed predictive formation control (DPFC) protocol for CPMASs, which features active compensation for constraints in the network with the aim of achieving formation consensus and stability. The cost functions are designed separately for leader and followers, enabling the output coordination of the leader and followers under the consideration of the formation configuration. The necessary and sufficient condition for stability and consensus is derived through the detailed analysis of closed-loop CPMASs with DPFC scheme. The control performance of the designed DPFC scheme is validated by the presented numerical simulations, which is extended to a formation control experiment of three-degree-of-freedom air-bearing-simulator (ABS) systems.

Development and evaluation of a space robot prototype equipped with a cable-driven manipulator

This research focuses on developing and evaluating a free-flying space robot equipped with a cable-driven manipulator and an adaptive gripper. First, a transmission joint comprising a pair of gears and pulleys is designed and actuated by motors located in the first link of the manipulator. Afterward, based on the kinematics and dynamics models of the robot, a mission distribution control scheme is proposed for the robot to drive its end-effector to achieve the desired position and attitude for capturing space targets. Furthermore, exploiting this strategy, considerable comparison simulations between two space robots equipped with a traditional manipulator and a cable-driven arm are conducted. Wherein, the goal position and attitude are selected through a uniform sampling method. For the same capture mission, energy consumptions of the base and manipulator as well as state errors of the base are taken as cost functions for performance evaluation. Finally, a planar target capture case study using the adaptive gripper and a spatial motion test with the help of an air-bearing simulator are carried out to demonstrate the efficiency of the presented cable-driven space robot.

Proportional Integral Predictive Control of High-Order Fully Actuated Networked Multiagent Systems With Communication Delays

This research is devoted to the cooperative control of high-order fully actuated networked multiagent systems (HOFA-NMASs) with communication delays between network node and sensors, and network node and actuators. A proportional integral (PI) predictive control scheme is developed to effectively implement the cooperation among HOFA-NMASs and actively compensate the communication delays. In this scheme, a local PI feedback controller is applied to stabilize the closed-loop nominal HOFA-NMASs, then a Diophantine equation is presented to establish an incremental HOFA prediction model rather than a reduced-order one, so that the optimization of cost function considered cooperative performance and the compensation of communication delays are completed via multistep output predictions, thus the optimal cooperative controllers are constructed. The further discussion provides a simple condition of simultaneous stability and output consensus of closed-loop HOFA-NMASs, which is easy to verify and extend in practice and is independent on communication delays. An experiment of formation control of air-bearing simulators is shown to prove the availability of the proposed PI predictive control scheme.

Coordinated Control of High-Order Fully Actuated Multiagent Systems and Its Application: A Predictive Control Strategy

This research is devoted to the coordinated control of high-order fully actuated multiagent systems (HOFA-MASs). A predictive control strategy is developed to realize the coordination of HOFA-MASs and simultaneous stability and output consensus. In this strategy, a Diophantine equation is introduced to construct an incremental HOFA prediction model rather than a reduced-order one, then a cost function focused on coordinated relationship is minimized by the design of predictive control such that the optimal coordination controllers can be achieved with simple and easy computation. Further discussion derives a simple criterion to guarantee the simultaneous stability and output consensus of the closed-loop HOFA-MASs. Two experiments of formation control of three air-bearing simulators are given to demonstrate the availability of the predictive control strategy.

The Analysis and Compensation of Elastic Unbalance Torque of the Three-axis Air-bearing Simulator

The most important interfering torque of a three-axis air-bearing simulator is the displacement of the center of mass in the gravity field caused by structural elasticity. In order to characterize the torque, a mathematical model of the interference moment was established. Based on the model, it is suggested that the vertical stiffness and horizontal stiffness of the structure should be equal as far as possible during the structural design, and the elastic unbalance moment can be compensated by the vertical offset of the center of mass of the air floating platform relative to the rotation center after the initial attitude leveling. ABAQUS was used to build a simulation model of the air floating platform, and the changes of the structure’s centroid before and after the gravitational field was applied were extracted by software to simulate the centroid deviation caused by the elastic deformation of the structure, which was used as the characterization to conduct discrete optimization of the structure. The optimal structural parameters were obtained. Then the disturbance torque curve and the corresponding initial centroid offset after initial centroid compensation were calculated by mathematical model. The results are of positive guiding significance to the design of three-axis air-bearing simulator.

Automatic Balancing Control of Air-bearing Simulator Based on Firefly Algorithm Improved Neural Network

In order to accurately reproduce the multi-satellite networking technology and simulate the multi-mode high-resolution imaging process on the ground, the three-axis air-bearing test bed was the key device of simulation. In this paper, a fast automatic balance adjustment control algorithm was proposed based on firefly algorithm improved BP (Back Propagation) neural network PID (Proportion Integration Differentiation) control. Aiming at the problem of long adjustment time and easy to obtain a non-optimal solution, the firefly algorithm was introduced to optimize the initial weight and threshold value of the BP neural network, and improve the algorithm performance in convergence rate and stability. Based on the kinematics and dynamics model of the three-axis air-bearing simulator platform, the simulation results show that the optimized algorithm reduces the <italic>x</italic>-axis centroid offset to 2.3×10^-7 m in 3.1 s. The algorithm has faster and higher stability on air-bearing simulator automatic balancing control, and satisfies the demand for multi-satellite imaging process simulation.

Automatic Balancing Control of Air-bearing Simulator Based on Firefly Algorithm Improved Neural Network

摘要: 为了利用气浮台在地面精准演示分布式多星组网技术及验证多模式高分成像过程，提出一种基于改进型BP神经网络PID控制的气浮台快速自动调平衡算法.针对以往算法调平时间较长、容易得到非最优解的问题，引入仿生萤火虫算法对神经网络初始权值进行优化，提高了算法的收敛速度和稳定性.基于构建的三轴气浮台运动学和动力学模型，通过仿真实验验证了优化算法对自动调平衡具有良好的控制效果，满足多星地面仿真的调平衡要求. 关键词: 气浮台 / 自动调平衡 / BP神经网络 / PID控制 / 萤火虫算法 / 多星地面仿真

自由飞行机器人气浮式模拟器设计

自由飞行机器人气浮式模拟器设计

Ground-based experiment of capturing space debris based on artificial potential field

An enabling debris capturing concept is experimentally demonstrated using an air-bearing testbed. To facilitate on-board implementation, the idea of artificial potential field is employed for the controller design of the debris capturing task. In particular, the artificial potential function is constructed such that all of its stable minima stratify the capturing condition, thereby avoiding the possibility of trapping into unwanted local minima. To experimentally simulate the mission of capturing space debris on ground, two air-bearing simulators are designed and developed, in which the first one is equipped with a single-degree-of-freedom robotic arm and the second one serves as a mock-up of the debris to be captured. The location and attitude of the simulators are measured by binocular cameras for control feedback. Experimental studies are performed to verify the results of the theoretic analysis.

Verification of Spin Magnetic Attitude Control System using air-bearing-based attitude control simulator

This paper accomplishes one goal and it was to verify and to validate a Spin Magnetic Attitude Control System (SMACS) program and to perform Hardware-In-the-Loop (HIL) air-bearing experiments. A study of a closed-loop magnetic spin controller is presented using only magnetic rods as actuators. The magnetic spin rate control approach is able to perform spin rate control and it is verified with an Attitude Control System (ACS) air-bearing MATLAB® SIMULINK® model and a hardware-embedded LABVIEW® algorithm that controls the spin rate of the test platform on a spherical air bearing table. The SIMULINK® model includes dynamic model of air-bearing, its disturbances, actuator emulation and the time delays caused by on-board calculations. The air-bearing simulator is employed to develop, improve, and carry out objective tests of magnetic torque rods and spin rate control algorithm in the experimental framework and to provide a more realistic demonstration of expected performance of attitude control as compared with software-based architectures. Six sets of two torque rods are used as actuators for the SMACS. It is implemented and simulated to fulfill mission requirement including spin the satellite up to 12degs−1 around the z-axis. These techniques are documented for the full nonlinear equations of motion of the system and the performances of these techniques are compared in several simulations.

Research on Optimal Sliding Mode Pose Control for a Six-DOF Air-Bearing Simulation Platform System

According to the requirements of the ground experiment table which is designed to simulate the lunar orbiter’s docking and the sample transferring processes for the 3rd step of China’s Lunar Exploration Program, a 6-DOF air-bearing simulation platform system is designed. We also proposed an optimal pose control method which method combines the sliding mode control with the optimal control theory in this paper. By introducing an integral compensation term, the optimal regulator is robust and the reaching mode of the sliding mode control is eliminated. This control methods could also eliminate the influence that the big load inertia ratio and the uncertain factors of the air-bearing pose control system had on the control precision. The experimental results indicate that the control accuracy of the system meets the task requirements and the correctness and feasibility of this scheme are verified.

Simulation of cross-talk between thermal track positioning control and thermal flying height control

In this study, a coupling analysis of thermal-structural simulation and air-bearing simulation has been performed to investigate the cross-talk effects between thermal track positioning control (TPC) and thermal flying height control (TFC) on the static flying attitude of a TPC-TFC slider. Simulation results show that the TPC heating induced head protrusion towards disk is comparable to the head actuation stroke along the cross-track direction. By optimizing the distance of TPC heater to air bearing surface, and the distance of TPC heater to the slider center line, it can obtain a large TPC actuation stroke and a small head protrusion towards disk. Moreover, it is found that the TPC heating will cause large protrusion of the side edge of trailing pad and change the flying characteristics significantly. A trade-off performance between cross-talk effects and TPC actuation stroke along cross-track direction is needed.

Parametric simulation of piezoelectric flying height control slider using shear-mode deformation

The piezoelectric flying height control slider has recently been implemented in magnetic recording disk drives to reduce the flying height. This paper performs the electromechanical simulation and air-bearing simulation to investigate the effects of the shear-model deformation on the static flying attitude of PZT slider. The location of PZT sheet and air bearing surface of slider are investigated to achieve a low flying height and robust head-disk interface. The results show that a short distance of the PZT sheet to the trailing edge of the slider can help to achieve a low flying height. A small center-trailing pad of the slider can also help to achieve a low flying height, but cannot prevent the reduction in pitch angle. The depth of the center-trailing pad does not change the reduction ratio of the pitch angle when increasing the drive voltage. A big pitch angle value is needed to avoid the pitch angle falling below zero at a high drive voltage.

Simulation of Piezoelectric Flying Height Control Slider Using Shear-Mode Deformation

The piezoelectric flying height control slider has recently been implemented in magnetic recording disk drives to reduce the flying height. This paper has examined the piezoelectric flying height control slider using shear-model deformation of piezoelectric transducer (PZT). A finite element model of the PZT slider using shear-model deformation has been built, and the electromechanical simulation and air-bearing simulation have been performed to investigate the effects of the shear-model deformation on the static flying attitude of the PZT slider. The results show that the flying height and pitch angle of the PZT slider can be significantly reduced with an increase in the drive voltage on the PZT sheet. However, beyond the drive voltage of 80V for the proposed PZT slider, the reduction in the flying height of PZT slider is limited owing to the high air bearing stiffness at low flying height region. Furthermore, the PZT slider can be rotated and balanced at a negative pitch angle.

Air Bearing Simulation for Bit Patterned Media

Air Bearing Simulation for Bit Patterned Media

Effects of Radial and Circumferential Disk Features on Slider Dynamics

As the head-disk spacing is reduced in order to achieve higher areal density, dynamic stability of the slider is compromised by a variety of proximity interactions. One of the key factors is the disk topography, which provides dynamic excitation to the low-flying sliders and strongly influences the dynamics and stability of the slider. Several experimental and numerical studies have been done on the fly height modulation caused by the disk topography along the track (circumferential) direction. In this paper, we investigate the effect of the disk topography in the circumferential as well as the radial directions and use a new method to measure the 2-D (true) disk topography for disks with three different kinds of roughness and waviness features. We used a dynamic air-bearing simulator to simulate the slider dynamics over the measured topographies. Simulations used 1-D topographies along the track direction as well as the actual 2-D topographies. Comparison of the slider dynamics over the different 1-D disk topographies indicates a strong dependence on the circumferential roughness and waviness features. Further, the comparison of slider dynamics and frequency content over 1-D and the 2-D disk topographies indicates that the radial features, which have not been studied intensively until now, are also very important in determining the actual slider dynamics, as they dictate the variation of the adjacent tracks in the circumferential direction. The simulations with 2-D disk topography are more realistic than the 1-D simulations. Further, the effect of the radial features can be reduced through effective air-bearing system design.

Air Bearing Simulation of Discrete Track Recording Media

Sliders flying over patterned or discrete track media are exposed to an entirely different pressure field from the air bearing than in the case of present day "smooth" disks. In this first study, we investigate the influence of discrete track media parameters such as groove width, groove pitch, and groove depth on the steady-state flying characteristics of five different slider designs using a finite-element-based air bearing simulator

Effect of van der Waals Force on Air-Bearing Flying Characteristics at Ultra-Low Fly Height

In order to increase recording density for magnetic recording systems, the fly height of slider, as part of head-media magnetic spacing, has to remain ultra-low through proper air-bearing designs. At these ultra-low fly heights, the presence of interfacial forces, such as van der Waals (vdW) force, can significantly affect air-bearing flying characteristics. In this paper, one air-bearing design has been studied at ultra-low fly heights with a proprietary air-bearing simulation code, where a Lifshitz-theory-based fully retarded vdW force model was applied on the multilayered head-disk interface (HDI), in contrast to most studies with a “nonretarded” single-layer approach. This results in a lower static fly height and a higher touch down/take-off velocity, which clearly demonstrates the necessity of performing the fully retarded calculation on a realistic layered model of the HDI for accurate vdW force predictions. A further breakdown of the vdW force components shows a dominant pitch moment contribution. This is attributed to a nonuniform Hamaker function distribution, which is highly dependent on air-bearing designs.

Van der Waals interactions between the air-bearing surface and a lubricated glass disk: A comparative study

Lifshitz theory has been used to calculate the van der Waals (vdW) force between a magnetic storage read-write head over both a lubricated glass disk and a magnetic disk. These forces were then incorporated into an air-bearing simulation that calculates the flying height of the slider as a function of disk revolutions per minute (rpm) for both types of media. A sharp decrease in the flying height of the slider over the magnetic disk was calculated at approximately 1950 rpm, whereas a similar decrease is observed at 150 rpm slower over the glass disk. These differences were ascribed to a significantly larger vdW force acting between the slider and the magnetic media, when compared to the glass disk. The magnitude of the vdW force, acting on the slider, over both glass and magnetic media, is described and its relevance to the reliability of the head-disk interface is discussed.