Smooth Acceleration Spectra for Pulse-Like Ground Motions

ABSTRACT Idealization of acceleration response spectra is the basis for construction of target spectra for seismic design and assessment of structures. The adequacy of current methods to reasonably idealize (or smooth) the acceleration spectra of pulse-like and nonpulse-like ground motions is examined in this study. The influence of separated pulses on different regions of acceleration response spectrum is first investigated using wavelet transform. One representative method is selected as the benchmark to examine the effectiveness of the Newmark–Hall-based methods to smooth the acceleration spectra of pulse-like and nonpulse-like ground motions. Presented are some important insights into why the plateau (or amplification factor) associated with the constant-acceleration branch may be underestimated and the ending cutoff period Tg be overestimated by Newmark–Hall-based methods. This study highlights the intrinsic characteristics and the importance of the constant-acceleration branch, based on which a two-step procedure is proposed to idealize the acceleration spectra. The results show that the proposed methodology can accurately identify the constant-acceleration branch regardless of the influence of pulses on the descending branch of acceleration spectra.

Assessment of efficiency of energy optimal driving mode for system of «pilot-free» movement of electric multiple units on the Moscow Central Ring

According to results of experimental studies within the framework of the Moscow Central Ring the authors revealed the best trips of drivers in terms of energy efficiency of train traction. The analysis of these trips allowed determining riding techniques that provide energy saving: smooth acceleration and braking at unconditional performance of the given train schedule. On the basis of the developed simulation model of the Moscow Central Ring it is established that the use of energy efficient techniques of riding with the on time train performance can reduce the power consumption on train traction by 13.3 %.

Analysis and Technology of the Bricard Linkage Kinematic Parameters Comparative Experiments

The article considers kinematic parameters of the 6R Bricard linkage characteristic point obtained analytically. Computer simulation of this mechanism resulted in diagrams of changes in the special orientation of the coordinate system of the characteristic point and a projection of its velocities to the basic coordinates system. In addition, we developed a prototype model for experimental studies. The difference between data obtained using the experimental model and the data obtained by computer analysis is less than 5%. This article describes the components of the experimental model. Using a stepper motor requires solving additional tasks: resonance, peaks at the first and the last steps, step dividing, ensuring the smooth acceleration of the motor shaft, smooth increasing of the shaft load, etc.

A Smooth Wave-Form Command Shaping Control

To avoid excitation of higher modes of flexible and multi-mode systems, it is important to eliminate sudden and jerky inputs. To achieve this goal, researchers tend to use different smoothing techniques to reduce the effect of the command roughness. In this work, a new smooth command-shaping technique for oscillation reduction of simple harmonic oscillators is proposed. A continuous smooth wave-form acceleration command-shaper is proposed. The shaper parameters are tuned to eliminate residual vibrations in rest-to-rest maneuvers. The performance of the proposed shaper is determined analytically, simulated numerically, and validated experimentally on a scaled model of an overhead crane. Results obtained show that the proposed smooth wave-form shaper is capable of eliminating travel and residual oscillations. Furthermore, unlike traditional step command shapers, the proposed command profiles have completely smooth acceleration, velocity, and displacement profiles. Experimental results demonstrate the ability of our proposed smooth wave-form commands to eliminate residual vibrations at the end of rest-to-rest maneuvers.

Strategy of Starting Sensorless BLDCM with Inductance Method and EMF Integration

In, conventional 3-stage start-up method of sensorless brushless direct current motor (BLDCM), the rotor is likely to jitter because rotor position cannot be obtained, and the motor is apt to lose step when it starts with load. These defects limit its use in engineering applications. In order to achieve smooth start in specific direction and guarantee start-up success rate with load, a start-up method based on improved inductance method and electromotive force (EMF) integration is proposed applying different voltage vectors according to rotor position interval judged by inductance method and determining integrator start-up time according to rotor initial position and the EMF. Experiments show that the method guarantees smooth acceleration and increases start-up success rate with load.

Realization of Target Position Changing On-The-Fly for Intelligent Motion Control Applications

This paper presents an algorithm of S-curve profile velocity planning with prediction of deceleration distance dynamically, extended functions including target position or target speed change on-the-fly, motion pausing and resuming are addressed. The algorithm is implemented for high performance multiple axes motion controller where complex paths must be employed for each axis to obtain smooth acceleration, speed, position shapes and target position or speed will be changed during moving to meet the requirement of processing. Application that requires the ability to change the endpoint or moving speed without completing the previous move are applied in varied industrial equipment such as SMT, AOI, product lines, etc.

Using MEMS Accelerometers to Improve Automobile Handwheel State Estimation for Force Feedback

This paper explores the possibility of combining solid state accelerometers with a low resolution position sensor to provide clean estimates of automobile handwheel position, velocity and acceleration for use in force feedback. Typically determining the acceleration and velocity of the handwheel requires differentiating a position sensor such as an encoder or potentiometer. Unless expensive high-resolution sensors are used, this differentiation leads to a noisy signal, requiring significant filtering which leads to significant phase lag. With a direct measurement of acceleration, we circumvent many of the problems associated with differentiation and filtering. This work uses a Kalman filter to combine a pair of MEMS accelerometers with a low-resolution potentiometer to estimate handwheel states. This measurement scheme is effective in this application because of the low frequency nature of the force feedback and because of the structural robustness of the handwheel system. Initial in-vehicle experimental results show the setup can provide smooth acceleration and velocity signals in a moving vehicle.