大客车局部优化造型对其使用性能的影响

随着车速的提高,汽车在行驶中受到的空气阻力便成为不可忽视的问题,因此与减阻节能相关的汽车优化造型也就显得越来越重要了。由于运动物体所受到的空气阻力系数的大小主要取决于它的头部的形状,因而我们对厢式大客车驾驶室前风窗区的几种不同造型在低速风洞中进行了测力的实验研究。实验结果表明,驾驶室前围不同形式的过渡是影响厢式客车空气阻力的重要因素。其中在适当的风窗倾角下,经过良好的圆化处理后,可使厢式大客车的空气阻力减小27%左右。这不仅节省了燃料的消耗,还可以提高汽车的最大行驶速度,改善其加速和爬坡能力。     

连杆位置综合的一种解析方法

本文根据半角转动的原理,提出了一种连杆位置综合的解析方法。此法概念清晰,计算比较方便。而且易于与图解法相沟通。列出了连杆五个位置综合问题的四个非线性方程。在解法上把上述问题化归为用优化方法求解。     

无线电遥测监视小直径刀具的工况过程

小直径刀具(φ6mm以下小钻头、铣刀)加工中产生的磨、破损信号难于检测。本文基于这一问题,研究采用无线电遥测技术来传输传感器信号,并建立了CIMS,FMS加工中心钻、铣用小直径刀具的工况监视系统。研究表明:用遥测技术传输的切削过程信息是可以用来识别刀具切削状态的;小直径刀具折断快速报警的成功率在90％以上。     

An Ideal Digital Frequency Translator

Many digital techniques are available for providing a desired shift in frequency of a given carrier signal, but the resulting output usually contains spurious harmonic content due to the digital means employed. This correspondence discusses a digital device which provides a variable shift in frequency of a given carrier signal, with the feature that no spurious harmonic content exists in the output.     

An Experimental Radar Facility

A coherent CW superheterodyne radar system operating at frequencies of 9, 17, 35, and 70 GHz is described. The radars are installed on a free-flight range to study backscattering from wakes of hypersonic-velocity projectiles. Each radar is equipped with a focused-lens antenna oriented at an angle of approximately 45° to the flight axis. Amplitude and phase of the received signal are recorded separately. Some typical results are given to demonstrate the capabilities of the equipment.     

Time-Optimal Control of a Bounded Phase-Coordinate Process II: High-Order Systems with Multiple Control Inputs

This paper considers the problem arising from the design of an autopilot for a large booster. The motion-controlling actuators of the booster have both position and rate limits. The problem is formulated as a bounded phase-coordinate problem and analyzed by the ``backing out of the target' procedure. A method of constructing the optimal control is presented. An example of an oscillatory system with two control inputs is given, and the optimal control is expressed as an explicit time function.     

Estimated Flight Time for Optimum Trajectories

Various methods are presented for estimating the flight time for vehicles which fly an optimum trajectory. A realistic example is considered in order to display the inherent accuracy of each of these methods. Numerical integration methods are found to be the most accurate. Simple formulas are derived for the case where a less accurate estimate is acceptable. All of these methods require less computation than would be required in order to solve the overall optimization problem. Thus any one of these methods can be applied to an onboard guidance scheme or control system which requires a real time estimate of the time-to-go.     

Comments on the Communication and Data Problems Associated with a Mars Trip During a Conjunction Phase

The analysis and comments presented in this paper are meant to establish the general communication parameters associated with Martian flyby probes and with lander and manned vehicles. Fundamental data transfer problems are reviewed to define comparisons and trends of tradeoffs for future studies. Selected focal points are based upon the long propagation path length, with inherent time delays, and the high noise produced by the sun. These problems are magnified because large quantities of data must be obtained to satisfy the needs of the scientific community and the curiosity of an interested public. A comparison of two communication systems is provided: the microwave spectrum and the optical spectrum, as represented by the microwaves at 2.3 GHz and the laser at 6328 ?. A method of cost effectiveness or value received from space missions (a criterion of power input for data quantity received) is also presented.     

Checkout: A Changing Technology

On-board/in-flight checkout of future aerospace systems will necessitate a fundamental departure from today's design and checkout activities. The interrelationship of checkout, incorporated into prime vehicular functions, man as a subsystem, and standardization Of hardware/software must be considered as a functional and integral entity if the efforts of today's long-range planning are to become tomorrow's reality. This paper will describe future systems checkout, maintenance and support considerations, and actions and tentative measures necessary for implementation. The realization of the implementation of these concepts into functional elements will depend, accurately and economically, upon the degree of government perceptiveness and the extent of industrial support.