Advanced Calculation Model of V-Belt Temperature Field

In the process of continuous high-strength operation of the harvester, structure aging, surface hardening, brittle fracture, and other features appear on V-belt due to temperature rise, which seriously affects the service life of the belt and stability of the whole machine. To predict the temperature distribution of V-belt and improve its service life, an advanced calculation method of temperature field suitable for multiwheel is proposed. First, on the basis of analysing the heat source of the transmission belt, the values of internal friction and external friction are calculated based on AVL Excite Timing Drive (AVL Excite TD). Secondly, two-dimensional temperature field finite element calculation model is established by analysing the heat balance equation, determining the heat flow distribution coefficient and heat convection conditions. Then, to verify the calculation model of the temperature field, the experimental setup and instrumentation are built based on Controller Area Network-bus (CAN-bus) technology. At last, multi-condition tests are designed in this paper. The experiment results show that the maximum difference between the model calculated value and experiment is 4.77 ℃ in unsteady state, and 0.15 ℃ in steady state. Therefore, the multiwheel V-belt temperature field calculation model developed in this paper can realize the accurate calculation of the temperature field under steady state conditions. It has a very important guiding significance for reasonable selection of operating parameters and improvement of service lifetime of belt.

Design of a Low Noise Area Array CCD Imaging System for Exoplanet Search

The search for exoplanets is a focal topic in astronomy. Since the signal from the detected target is very weak, the imaging system needs to have ultra-low readout noise. Therefore, a low noise charge-coupled diode (CCD) imaging system for exoplanet search (LNCIS) is proposed. Based on the area array CCD (TH7888A), the circuit and timing drive of LNCIS are designed. Especially, the application of correlation dual sampling (CDS) and asynchronous first-in, first-out (FIFO) memory can effectively suppress the correlation noise of the image signal. Moreover, this article proposes a fully differential double correlation sampling method, which can achieve better sampling effect and can better eliminate common-mode noise, improve dynamic range, and achieve high-quality image signal output. In addition, an independent counting method for adjusting the exposure time is proposed, which satisfies the requirements of the long exposure time of the imaging system, so that the CCD can be provided an independent and adjustable exposure time in the photosensitive stage. The LNCIS uses the FPGA (ZYNQ7000) as the core control device to produce the timing according to the function of the system. Finally, the experimental results show that the real-time image acquisition is achieved under the condition that the CCD readout clock frequency is 20 MHz. It is verified that the circuit and timing drive of the imaging system can meet the design requirements.

Power loss reduction in timing chain drives by adjusted tensioning and surface structuring

Purpose Energy losses in a timing chain drives are caused by friction in chain-rail contacts. To improve the efficiency, the Chair of Machine Elements and Transmission Technology at the University of Kaiserslautern developed various experimental and simulative analysis tools as a part of the German Research Foundation (DFG)-funded 1551 priority program and the DFG Collaborative Research Centre CRC 926. With these tools, various approaches for improving the efficiency were investigated. This paper aims to illustrate the approaches and present the results achieved within the framework of the above-mentioned priority program. Design/methodology/approach A towed cylinder head test rig is used for efficiency tests on timing chain drives. In addition to the experiments, a multi-body simulation model of the timing drive was developed and used. Findings It was possible to find positive approaches to reduce friction power by adapting the chain tensioning force as required. This was ensured for both the stationary operating points and the transient operating processes. An efficiency improvement of up to 10 per cent could be detected. Furthermore, a possibility was found to improve the frictional power by a targeted lubrication of the chain-rail contact. Here, the efficiency could be improved by 5-6 per cent. In addition, various structures were examined on a microscopic and macroscopic level. Neutral to negative results were achieved here. Originality/value This paper makes a contribution to improve the energy efficiency of timing chain drives. Different approaches have been investigated and evaluated.

Investigations of the Friction Losses of Different Engine Concepts. Part 1: A Combined Approach for Applying Subassembly-Resolved Friction Loss Analysis on a Modern Passenger-Car Diesel Engine

This work presents the application of a combined approach to investigate the friction losses in a modern four-cylinder passenger-car diesel engine. The approach connects the results from engine friction measurements using the indication method and the results from journal-bearing simulations. The utilization of the method enables a subassembly-resolved friction loss analysis that yields the losses of the piston group, crankshaft journal bearings, and valve train (including the timing drive and crankshaft seals). The engine and engine subassembly friction losses are investigated over the full speed and load range, covering more than 120 engine operation points at different engine media supply temperatures ranging from 70 to 110 ∘ C. The subsequently decreasing lubricant viscosity due to higher engine media supply temperatures allow for the identification of friction reduction potentials as well as possible risks due to an onset of mixed lubrication. Furthermore, additional strip-tests have been conducted to determine the friction losses of the crankshaft radial lip seals, the timing drive, and the crankshaft journal bearings, thus enabling a verification of the calculated journal-bearing friction losses with measurement results. For the investigated diesel engine, a friction reduction potential of up to 21% could be determined when increasing the engine media supply temperature from 70 to 110 ∘ C, at engine speeds higher than n = 1500 rpm and part load operating conditions. At low engine speeds and high load operations, the friction loss reduction potential is considerably decreased and below 8%, indicating mixed lubrication regimes at the piston group and valve train.

Motor control by precisely timed spike patterns

A fundamental problem in neuroscience is understanding how sequences of action potentials (“spikes”) encode information about sensory signals and motor outputs. Although traditional theories assume that this information is conveyed by the total number of spikes fired within a specified time interval (spike rate), recent studies have shown that additional information is carried by the millisecond-scale timing patterns of action potentials (spike timing). However, it is unknown whether or how subtle differences in spike timing drive differences in perception or behavior, leaving it unclear whether the information in spike timing actually plays a role in brain function. By examining the activity of individual motor units (the muscle fibers innervated by a single motor neuron) and manipulating patterns of activation of these neurons, we provide both correlative and causal evidence that the nervous system uses millisecond-scale variations in the timing of spikes within multispike patterns to control a vertebrate behavior—namely, respiration in the Bengalese finch, a songbird. These findings suggest that a fundamental assumption of current theories of motor coding requires revision.

Motor control by precisely timed spike patterns

SummaryA fundamental problem in neuroscience is to understand how sequences of action potentials (“spikes”) encode information about sensory signals and motor outputs. Although traditional theories of neural coding assume that information is conveyed by the total number of spikes fired (spike rate), recent studies of sensory [1–5] and motor [6] activity have shown that far more information is carried by the millisecond-scale timing patterns of action potentials (spike timing). However, it is unknown whether or how subtle differences in spike timing drive differences in perception or behavior, leaving it unclear whether the information carried by spike timing actually plays a causal role in brain function [1]. Here we demonstrate how a precise spike timing code is read out downstream by the muscles to control behavior. We provide both correlative and causal evidence to show that the nervous system uses millisecond-scale variations in the timing of spikes within multi-spike patterns to regulate a relatively simple behavior – respiration in the Bengalese finch, a songbird. These findings suggest that a fundamental assumption of current theories of motor coding requires revision, and that significant improvements in applications, such as neural prosthetic devices, can be achieved by using precise spike timing information.

Analysis and Research of Dynamic Characteristics of Synchronous Belt of a Diesel Using Multi-Body Dynamics

The dynamic tension of synchronous belt and pulleys forces are obtained by analyzing the dynamic characteristics of timing drive system of a diesel based on muti-body dynamics. The effects of crankshaft speed fluctuation and other excitations on the dynamics characteristics of synchronous belt are illustrated. After the analysis, it is found that crankshaft speed fluctuation has a great influence on the linear and transversal vibrations of synchronous belt. Comparing the simulation results of the original timing system and the one optimized, it is found that the modal frequency of synchronous belt depends on its span. Therefore it is important to control the span of belt and arrange the tensioner pulley properly for timing system design.