Reducing scrapping of gears by assessment of tip contact threshold torque

While striving for more competitive products as well as reaching the Global Sustainable Development Goals, automotive powertrain manufacturers increase the demands on gears, which translates to decreased manufacturing error tolerances. Too tight tolerances may, however, counteract the goal if it leads to increased material and energy consumption due to unjustified scrapping. This paper presents a method to prevent unjustified scrapping by comparing the severity of different manufacturing error tolerances by means of the tip contact threshold torque. Curve fits are shown to be accurate and helpful to assess the outcome of a produced batch of gears. A case study is made where the method is used with measured data from the industry. It can be concluded from the investigation that considerable amounts of scrapping can be avoided by consideration of the threshold torque.

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.

Study on a Horizontal Axial Flow Pump during Runaway Process with Bidirectional Operating Conditions

The ultra-low head pump stations often have bidirectional demand of water delivery, so there is a risk of runaway accident occurring in both conditions. To analyze the difference of the runaway process under forward runaway condition (FRC) and backward runaway condition (BRC), the whole flow system of a horizontal axial flow pump is considered. The Shear-Stress Transport (SST) k-ω model is adopted and the volume of fluid (VOF) model is applied to simulate the water surface in the reservoirs. Meanwhile, the torque balance equation is introduced to obtain the real time rotational speed, then the bidirectional runaway process of the pump with the same head is simulated. Additionally, the vortex transport equation is proposed to compare the contribution of vortex stretching and vortex dilatation terms. According to the changing law of the impeller torque, the torque curve can be divided into five stages: the drop, braking, rising, convergence and runaway stages. By comparison, the rising peak value of torque under FRC is significantly higher than that under BRC in the rising stage. Simultaneously, through the short time Fourier transform (STFT) method, the amplitude of torque pulsation is obviously different between FRC and BRC. The analysis reveals that the flow impact on blade surface increases the pressure difference between the two sides of the blade in braking condition, which leads to the torque increase in the rising stage. Moreover, the pulsation amplitude of torque is mainly affected by the integrity of the vortex rope.

Torque Curve Optimization of Ankle Push-Off in Walking Bipedal Robots Using Genetic Algorithm

Ankle push-off occurs when muscle–tendon units about the ankle joint generate a burst of positive power at the end of stance phase in human walking. Ankle push-off mainly contributes to both leg swing and center of mass (CoM) acceleration. Humans use the amount of ankle push-off to induce speed changes. Thus, this study focuses on determining the faster walking speed and the lowest energy efficiency of biped robots by using ankle push-off. The real-time-space trajectory method is used to provide reference positions for the hip and knee joints. The torque curve during ankle push-off, composed of three quintic polynomial curves, is applied to the ankle joint. With the walking distance and the mechanical cost of transport (MCOT) as the optimization goals, the genetic algorithm (GA) is used to obtain the optimal torque curve during ankle push-off. The results show that the biped robot achieved a maximum speed of 1.3 m/s, and the ankle push-off occurs at 41.27−48.34% of the gait cycle. The MCOT of the bipedal robot corresponding to the high economy gait is 0.70, and the walking speed is 0.54 m/s. This study may further prompt the design of the ankle joint and identify the important implications of ankle push-off for biped robots.

Comparative Analysis of the Steady-State Model Including Non-Linear Flux Linkage Surfaces and the Simplified Linearized Model when Applied to a Highly-Saturated Permanent Magnet Synchronous Machine—Evaluation Based on the Example of the BMW i3 Traction Motor

This paper presents a finite element method (FEM)-based model, which describes the magnetic circuit of the BMW i3 traction machine. The model has been reconstructed based on data available in the public domain. The reader is provided with numerical data regarding flux linkage surfaces in d- and q-axes, as well as with all the information needed to develop a space-vector model of the machine in steady-state, taking into consideration the non-linearity of the magnetic circuit. Hence, the data of a highly-saturated machine from a renowned product are provided, which can serve as a reference design for research. After that, torque curve and partial load operation points are calculated. Finally, the machine model is linearized and the calculations are repeated with the simplified linearized model. The results from both models are then compared with each other. This comparison is intended to assess the magnitude of the expected inaccuracies, when simplified analytical tools are applied to highly-saturated machines (which are the backbone of automotive electrical drivetrains). It is especially important with regard to preliminary design of electrical drivetrains, as at this stage detailed machine geometry and materials are not known.

Design and Implementation of Intelligent Agent Training Systems for Virtual Vehicles

This paper presents the results of the design, simulation, and implementation of a virtual vehicle. Such a process employs the Unity videogame platform and its Machine Learning-Agents library. The virtual vehicle is implemented in Unity considering mechanisms that represent accurately the dynamics of a real automobile, such as motor torque curve, suspension system, differential, and anti-roll bar, among others. Intelligent agents are designed and implemented to drive the virtual automobile, and they are trained using imitation or reinforcement. In the former method, learning by imitation, a human expert interacts with an intelligent agent through a control interface that simulates a real vehicle; in this way, the human expert receives motion signals and has stereoscopic vision, among other capabilities. In learning by reinforcement, a reward function that stimulates the intelligent agent to exert a soft control over the virtual automobile is designed. In the training stage, the intelligent agents are introduced into a scenario that simulates a four-lane highway. In the test stage, instead, they are located in unknown roads created based on random spline curves. Finally, graphs of the telemetric variables are presented, which are obtained from the automobile dynamics when the vehicle is controlled by the intelligent agents and their human counterpart, both in the training and the test track.

Polyoxymethylene/graphene nanocomposites: thermal, crystallization, melting and rheological behavior

Polyoxymethylene (POM) and graphene nanoplatelets (GNP) nanocomposites were produced and their thermal properties investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Torque rheology was used to evaluate melted nanocomposites behavior. As nanofiller, two commercial GNP grades were used and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), DSC and TGA showing great morphological and structural differences. Nanocomposites thermal stability has increased for additions up to 0.25 wt.% of both nanoparticles. However, for concentrations above 0.50 wt.%, severe matrix degradation was observed. The extent of the effect on the thermal stability of the materials also varied with the grade of GNP used and seems to be related with GNP’s extent of oxidation and defect density. The extrusion process was optimized in order to minimize secondary thermal degradation mechanisms, showing that the nanofiller nature is the most relevant factor in POM/GNP based systems. DSC analyzes showed that the addition of GNP interferes with the polymer crystallization process, alters the degree of crystallinity and increases the crystallization temperature, indicating that GNP acts as a nucleating agent for POM. The torque rheology showed that slope and level of the torque curve seems to be related with the stabilization or degradation effect observed in the thermal analysis, allowing immediate qualitative evaluation of degradation effect during extrusion process.

The Potential of Wobble Plate Opposed Piston Axial Engines for Increased Efficiency

Recent announcements regarding the phase out of internal combustion engines indicate the need to make major changes in the automotive industry. Bearing in mind this innovation trend, the article proposes a new approach to the engine design. The aim of this paper is to shed a new light on the forgotten concept of axial engines with wobble plate mechanism. One of their most important advantages is the ease of use of the opposed piston layout, which has recently received much attention. Based on several years of research, the features determining the increase in mechanical efficiency, lower heat losses and the best scavenging efficiency were indicated. Thanks to the applied Variable Compression Ratio (VCR), Variable Angle Shift (VAS) and Variable Port Area (VPA) systems, the engine can operate on various fuels in each of the Spark Ignition (SI), Compression Ignition (CI) and Homogeneous Charge Compression Ignition (HCCI)/Controlled Auto Ignition (CAI) modes. In order to quantify the potential of the proposed design, an initial research of the newest PAMAR 4 engine was presented to calculate the torque curve at low rotational speeds. The achieved torque of 500 Nm at 500 rpm is 65% greater than the maximum torque of the OM 651 engine of the same 1.8 L capacity. The findings lead to the conclusion that axial engines are wrongfully overlooked and can significantly improve research on new trends in pollutant elimination.

A General Modeling Methodology for the Quasistatic Behavior of Spiral Torsion Springs

Due to their robustness, compactness, simplicity, and the possibility of nonlinear torque curves, spiral springs are being increasingly contemplated for industrial application. Recent manufacturing technologies and materials allow for the creation of spiral springs of various shapes and geometries able to provide the required torque curves. Modeling the behavior of this kind of springs is highly complex due to the strong nonlinearities arisen from large deflections and the possibility of coiling of strip length around the spring barrel or arbor. For this reason, up to our knowledge, existing models only provide design features such as deflection and torque curve for the simplest strip geometries, and fewer models supply, only if no strip coiling occurs, reactions at the strip-barrel and strip-arbor clampings. In addition, to our knowledge, just semi-empirical models for strip-barrel, -arbor and -strip contact forces or friction torques were available. In this work, we introduce a novel general, an analytical quasistatic model for the calculation of all the above spring characteristics for any length-dependent strip material and initial geometry and strip cross-sectional shape and for any barrel and arbor radii. The strip deflection curvatures are calculated minimizing the sum of elastic and gravitational potential energies under geometrical constraints associated with eventual strip coiling. Once the curvatures are calculated, the spring internal, contact, and reaction forces can be straightforwardly calculated by solving the elastica differential equations. Friction is taken into account by evaluating the contact conditions at the strip coiled sections.

Advances in Diesel-LNG Internal Combustion Engines

Diesel-LNG internal combustion engines (ICEs) are the most promising light and heavy-duty truck (HDT) powering solution for a transition towards a mixed electric-hydrogen renewable energy economy. The diesel-liquid CH4 ICEs have indeed many commonalities with diesel-liquid H2 ICEs, in the infrastructure, on-board fuel storage, and injection technology, despite the fact H2 needs a much lower temperature. The paper outlines the advantages of dual fuel (2F) diesel-LNG ICEs developed adopting two high-pressure (HP) injectors per cylinder, one for the diesel and one for the LNG, plus super-turbocharging. The diesel-LNG ICEs provide high fuel energy conversion efficiencies, and reduced CO2, PM, and NOx emissions. Super-turbocharging permits the shaping of the torque curve while improving acceleration transients. Diesel-LNG ICEs may also clean up the air of background pollution in many polluted areas in the world. Computational results prove the steady-state advantages of the proposed novel design. While the baseline diesel model is a validated model, the 2F LNG model is not. The perfect alignment of the diesel and diesel-LNG ICE performances proven by Westport makes however the proposed results trustworthy.