Showing papers in "Journal of System Design and Dynamics in 2013"

Robust Tracking Control of a Quad-Rotor Helicopter Utilizing Sliding Mode Control with a Nonlinear Sliding Surface

Abstract: This paper presents a sliding mode control using a nonlinear sliding surface (NSS) to design a robust tracking controller for a quad-rotor helicopter. An NSS is designed to provide a variable damping ratio for the closed-loop dynamics of the system to achieve a quick response and low overshoot performance. The dynamics of the quad-rotor helicopter is derived by the Newton-Euler formulation for a rigid body. The global stability of the proposed control strategy is guaranteed on the basis of the Lyapunov stability theory. The robustness and effectiveness of the proposed control system are demonstrated experimentally, providing comparative results with a conventional linear sliding surface. The NSS provides robust tracking control under significant wind gusts.

Optimal Motion Trajectory Generation and Real-Time Trajectory Modification for an Industrial Robot Working in a Rectangular Space

Abstract: This paper considers the time-optimal motion and obstacle avoidance trajectory generation for industrial robots. Although there are many previous works that had a similar objective, the generation of the trajectory for a general type of robot is still challenging because high computation time is required. This research focuses on a common type of robot that has a simple structure and moving environment. This limitation allows us to generate the trajectory in a much simpler and practical manner. In addition, oscillation suppression can be considered in the trajectory generation in the proposed approach. The real-time modification of the optimal trajectory is often required from a practical point of view. To avoid the recalculation of the trajectory that requires high computation time, we propose a real-time modification method of the trajectory. Simulation and experimental results demonstrate the effectiveness of the proposed methods.

Sound and Vibration Research of Rolling Bearings in Japan

Abstract: This article deals with the progress of the sound and vibration research of rolling bearings in Japan. The literature mainly cited is written in Japanese. The focus in sound research is the early research, characteristics and generating mechanism of ball bearings, cage sound, squeak in cylindrical roller bearings, sound of defective bearings, contamination noise and sound life. In the vibration research, the early research, rolling element (ball or roller) passage vibration, natural vibration of the outer ring, natural vibration of the cage, vibration caused by geometrical imperfections, nonlinear vibration, abnormal vibration of grease lubricated ball bearings, vibration of defective bearings, damping and squeeze film damper are explored.

DEVELOPMENT and ANALYSIS of a REGENERATIVE SHOCK ABSORBER for VEHICLE SUSPENSION

Abstract: Only10-16% of the fuel energy is used to drive the car-to overcome the resistance from road friction and air drag.One important loss is the dissipation of vibration energy by shock absorber of the vehicle suspension due to road irregularity, vehicle acceleration and deceleration.A prototype of regenerative shock absorber (RSA)was developed and its performance was studied.The prototype of RSA mainly consists of a gear transmission system, one way bearing and an electromagnetic generator.The RSA’s damping coefficient, its capacity to absorb energy and its ability to regenerate electrical energy were measured for various input frequencies, amplitudes and electrical loads. A quarter car model which consists of the developed RSA,a mass anda spring with specific damping ratio of ζ=0.6 and ζ=0.8 was tested. The test was done using a quarter car suspension test rig to investigate the performance of suspension which uses RSA and the generated electrical energy from RSA. The results are reported and discussed in this article.

Study on Vibration Characteristics of Mistuned Bladed Disk(Vibration Response Analysis by Reduced Model FMM)

Abstract: It is well known that the asymmetric vane spacing can result in decreased levels of the excitation at specific frequencies. In the previous paper, the resonant response reduction of the mistuned bladed disks due to the asymmetric vane spacing was studied by use of the equivalent spring-mass model. Although the mistuned bladed disk should be analyzed by FEA (Finite Element Analysis) to accurately evaluate the resonant response reduction effect of the asymmetric vane spacing, it is unrealistic due to enormous computational time. Therefore, in this study, the mistuned bladed disk is modeled by use of FMM (Fundamental Mistuning Model) to evaluate the resonant response reduction effect of the asymmetric vane spacing accurately and practically. First, the frequency response analysis of a simple mistuned bladed disk consisting of flat plate blades is carried out for the symmetric and asymmetric vane spacing, using both of FMM and the direct FEA, and the calculated results are compared to confirm the validity of FMM. Second, the frequency response analysis of a realistic bladed disk is carried out for the symmetric and asymmetric vane spacing, using FMM, to examine the effect of the resonant response reduction effect.

Force Redistribution Method for Compensating Actuator-Breakdown of Vibration-Isolation Tables Supported with a Redundant Number of Pneumatic Actuators

Abstract: A force redistribution method for compensating actuator breakdown of vibrationisolation tables is studied. The vibration-isolation table is supported by eight pneumatic actuators and has a redundant number of actuators with respect to the degrees of freedom of table motion. We propose a force redistribution method that utilizes the redundancy of the actuators. In the proposed method, when some of the actuators break down, their output forces are redistributed on the unbroken actuators. We construct a detailed mathematical model in view of the behavior of the vibration-isolation table when some of the actuators break down. A type 1 digital servo system is applied to control the vibration and position of the vibration-isolation table. We perform numerical simulations in which some of the actuators break down at a certain time and the pressure of the broken actuators decreases at a constant rate. The numerical simulations examine the effectiveness of the proposed method.

Target Level Setting Method for the Reference Signal of Operational TPA

Abstract: In the present study, a target level setting method for the reference signal of operational TPA was considered using the principal component regression method. A principal component having a high contribution to the response signal was selected and target levels of the reference signals were set through principal component sensitivity analysis. In addition, a method that can extract the behavior of a principal component having a high contribution to the response signal was considered for the countermeasure. In order to verify the e ffectiveness of these methods, operational TPA and the proposed methods were applied to a small model vehicle. In the experiment, floor vibration was set as the response signal and nine measurement points, such as motor attachment points, were used as the reference signals. Here, we set the target reduction level of the response point vibration as 5 dB. Next, the target levels of the reference signal were calculated by principal component sensitive analysis and the countermeasure was considered through the principal component behavior analysis. By referring to the analytical result, a countermeasure to reduce the floor vibration was sought. As a result, the floor vibration level was almost reduced to the target level (5 dB). These considerations and experiments indicate that operational TPA could have additional functionality, whereby the method could set reference signal targets and suggest countermeasure guidelines in addition to performing contribution separation.

Dynamical Modeling and Stability Analysis of a Gyroscopic Exercise Tool Considering Contact/Separation and Slide between the Rotor and the Case

Abstract: The gyroscopic exercise tool to train the hand muscle, which utilizes the gyroscopic effect caused by the whirling motion of the high speed rotating body is considered. This tool shows the contact phenomenon between the rotor and the case. When the input motion with several Hz is added to the case, the rotor spins in thousands rpm whirling with the slow precession motion. Conventional studies on this tool have assumed the continuous rolling motion of the rotor on the track in the case. This paper does not set this assumption, and develops the dynamical model of this tool considering the contact/separation conditions and the slide between the rotor and the case. Two kinds of motions are observed in the numerical simulation, one is the uniform precession synchronous to the input case motion which was observed in the conventional studies. The other is the periodically reverse precession asynchronous to the input motion, which was not observed in the conventional studies. These two motions are physically explained, their stabilities are clarified by the energy analysis. These motions are also observed in the experiment.

Fabrication of Power Saving Solar Magnetic Suspension System

Abstract: Copyright © 2013 by JSME Abstract Extra low-power magnetic suspension system is achieved using solely solar power. Presently, solar cells have become more efficient and cost-saving year by year. In this work, a solar power generation technique is combined with zero-power control magnetic suspension. The zero-power control is achieved by converging the control current to zero in the steady states where the bias force generated by a permanent magnet is balanced with the gravitational force. Therefore, the steady-states power consumption becomes virtually zero in this suspension system. However, peripheral devices including sensors and controllers need power in both transient and steady states. Hence, the power consumed in the peripheral devices becomes dominant. In this work, dedicated power-saving peripheral devices are fabricated. It is observed that the average power consumed by the electromagnet is 20[mW] for suspending a 90-gram mass, and the power consumed by the peripheral devices is 13[mW]. In contrast, a conventional system consumes a few watts to suspend a floator of the same dimensions. The solar cells used in the apparatus has a maximum power capacity of 2[W] under a typical summer sunlight (approximately 120[klx]). The fabricated system can achieve stable suspension even under a illuminance of a fluorescent lamp of 5[klx].

A Study on Comparison between Input Powers and Contribution Rates from Statistical Energy Analysis and Transfer Path Analysis on a Mechanical Structure

Abstract: This paper presents a method for comparing the input powers and contribution rates from a power source to a structure in machine operation determined by statistical energy analysis (SEA) and transfer path analysis (TPA). Identifying external forces and contribution rates from input power sources during machine operation is important for analyzing machine and equipment, and dynamic designs. SEA is used for systems with many resonant modes, and predicted results are based on spatial averages. In contrast, TPA is based on estimation of a frequency response function between an excitation point and a response point. In this study, a method is proposed for comparing SEA evaluated by the power injection method and TPA evaluated by the matrix inversion method. The proposed method is validated through numerical analyses, using a finite element method of a simple structure consisting of two flat plates connected in an L-shaped configuration and a partial car model consisting of four subsystems. As a result, the SEA input power is spatial averaged over each subsystem quantitatively agrees with the TPA input power expressed as the product of the force and velocity at the excitation point. Contribution rates from a power source, the SEA and TPA results are qualitatively similar without having to consider the phase.

Investigation of Efficiency Improvement in Digging Operation for Hydraulic Excavators

Abstract: Operations of hydraulic excavators require high operation skill and operators have possibilities to work in unsafe environment. To solve these problems, automatic digging control is often studied, but there are few studies focused on improvement of efficiency. A high efficiency digging algorithm for a hydraulic excavator has not been established because relationship between digging motion and digging performance is very complex. A simulation model which is able to consider interaction between soil and machine would help to establish a digging algorithm for improving energetic efficiency. In this paper, an example for improvement of digging efficiency is shown by our developed distinct element method (DEM) simulation. First, in order to improve the accuracy of the DEM simulation, the parameter identification test is carried out to identify damping ratio and friction coefficient between soil particles. Besides, accuracy of digging efficiency evaluation by the developed simulation is shown by a developed digging test device which can reproduces excavation by hydraulic excavator. Finally, digging simulations are conducted by our suggested automatic digging algorithm. Varying control parameters, the simulation estimates influences of control parameters. These simulation results show that the simulation is able to specified control parameters which improve digging efficiency. Our research evaluates effectiveness of model-based development for automatic digging which enhances efficiency.