Exploring the integration of multi-speed gearboxes in electric vehicle (EV) drivetrains, this research presents a comprehensive analysis through detailed gearbox modelling, empirical traction machine testing, and analytical drive unit loss evaluations. The study utilizes two distinct automotive-grade electric machines – an axial-flux permanent magnet synchronous machine and an interior permanent magnet machine, the latter coupled with a single-speed gearbox – to demonstrate how multi-speed gearboxes can enhance drivetrain efficiency and performance for a subcompact EV. Extensive dynamometer testing, incorporating a variety of electrical and thermal conditions, characterizes both traction machines. Findings reveal that despite the incremental churning losses from additional gear pairs, two-speed gearboxes facilitate a more efficient operation of the electric machine, inverter, and gearbox, particularly when optimized through strategic gear ratio selection. Dynamometer testing under no-load conditions and at different temperatures underscores the impact of gearbox churning and bearing drag losses and the potential for their reduction. Detailed examinations of load-dependent and independent losses within the drive unit elucidate the interactions among drivetrain components across various gear ratios. Optimized two-speed gearboxes are shown to reduce vehicle energy consumption by up to 9% and increase driving range compared to conventional single-speed configurations, supported by strategic gear ratio selections and optimizations aimed at achieving vehicle performance targets, such as acceleration, gradeability, and top speed. This research contributes to advancing the field of electric vehicle technology by illustrating the complex trade-offs and potential enhancements achievable with multi-speed drivetrains, setting a precedent for future studies to refine gearbox performance and explore novel technologies to optimize powertrain performance across diverse operational landscapes. / Thesis / Doctor of Philosophy (PhD)

This report presents the development of a dynamic temperature model for an automatic transmission in a Volvo Cars passenger vehicle. The model should simulate the oil to cooler temperature and flow from the transmission. A mathematical approach to use lumped masses for different parts of the transmission was used. To tune the response of the lumped masses and heat transfer coefficients; temperature measurements were done on a vehicle in a chassis dyno. To verify the model, simple drive cycles were performed with temperature measurement in the same chassis dyno and on the same vehicle. The verification on the model shows that the model can simulate the behavior of a transmission with an error of 2.5 °C during normal behavior and 6.5 °C for a few minutes when a sudden change in the temperature from the cooler have a large transient increase. Because of this, the model is considered to be fairly accurate. However, in order to make the model compatible with Volvo Cars existing simulation software, Vsim, a "cooler model" has to be created.

<p><p>In order to be competitive in the markets of today, more and more companies try to make their production more effective by automation. Consequently more money is invested in robots and the operability of the robots becomes increasingly important. Undetected faults may result in damages, both to the robot itself and to the operator, which make detection and prediction of faults important.</p><p>The gearboxes responsible for controlling the motions of the robots are essential for their functionality. In order to increase the understanding about them this project focuses on creating a model of the stress distribution inside a gearbox.</p><p>First, the geometry of the gearbox is measured and digitalized using a vernier caliper, a protractor, a ruler and the CAD-program Solid Works. Then the geometry is imported into the finite element program Samcef.</p><p>In Samcef, the interaction between the parts in the gearbox is modeled and a dynamic simulation of the stresses inside the gearbox during a robot cycle performed.</p><p>Since there are almost no experience about Samcef at ABB SECRC, part of the project is to evaluate the program and comment the experiences received when using it.</p><p>Two main power transmission steps are identified, modeled and simulated. They are merged together into a big model where both steps are present. This model consists of all the essential power transmission inside the gearbox, from input to output. The load applied is a rotational movement on the input axle during a robot cycle.</p></p>

<p>This thesis work is an evaluation of journal bearings in manual transmissions in automobiles. Today both journal- and needle bearings can be positioned into the gearboxes and in order to reduce the power loss developed by friction when a relative angular velocity arises, the right type of bearing must be chosen.</p><p>In order to succeed, this work is aimed to develop a Matlab simulation model, which should be used as a tool in the design process of manual transmissions. The program development is later supposed to be followed by real tests of journal bearings, partly to cover things that can not be covered in the model but also to confirm how well the model reflects the reality. The absence of resources resulted in no performed real test and therefore was a comparison between theoretical-  and practical results not possible.</p><p>Here the plain journal bearings in full film lubrication will have an disadvantage compared to the needle bearings regarding the power lost. To reduce the drag below the values of the needle bearings a modified journal bearing in the area of boundary lubrication with a very low coefficient of friction may be an option. But problems with wear under this condition could most certainly be devastating and must be further investigated with real tests.</p><p>Out of a efficiency point of view the most suitable bearing position is the gear in the most frequently used area. Here it is assumed to be the 4^th gear.</p><p>A suitable journal bearing design should have a small sliding surface area in order to minimize the viscous drag. To achieve low friction the boundary lubricated area could be a good idea in cases when wear is not a critical factor. To longer the useful life nitrocarburizing is recommended, which both reduces wear and lower the coefficient of friction, in cases of asperites in contact. In order to work under the full film lubricated condition, with neglected wear, the sliding area needs to be large enough to create the required oil pressure.</p>

In order to be competitive in the markets of today, more and more companies try to make their production more effective by automation. Consequently more money is invested in robots and the operability of the robots becomes increasingly important. Undetected faults may result in damages, both to the robot itself and to the operator, which make detection and prediction of faults important. The gearboxes responsible for controlling the motions of the robots are essential for their functionality. In order to increase the understanding about them this project focuses on creating a model of the stress distribution inside a gearbox. First, the geometry of the gearbox is measured and digitalized using a vernier caliper, a protractor, a ruler and the CAD-program Solid Works. Then the geometry is imported into the finite element program Samcef. In Samcef, the interaction between the parts in the gearbox is modeled and a dynamic simulation of the stresses inside the gearbox during a robot cycle performed. Since there are almost no experience about Samcef at ABB SECRC, part of the project is to evaluate the program and comment the experiences received when using it. Two main power transmission steps are identified, modeled and simulated. They are merged together into a big model where both steps are present. This model consists of all the essential power transmission inside the gearbox, from input to output. The load applied is a rotational movement on the input axle during a robot cycle.

This thesis work is an evaluation of journal bearings in manual transmissions in automobiles. Today both journal- and needle bearings can be positioned into the gearboxes and in order to reduce the power loss developed by friction when a relative angular velocity arises, the right type of bearing must be chosen. In order to succeed, this work is aimed to develop a Matlab simulation model, which should be used as a tool in the design process of manual transmissions. The program development is later supposed to be followed by real tests of journal bearings, partly to cover things that can not be covered in the model but also to confirm how well the model reflects the reality. The absence of resources resulted in no performed real test and therefore was a comparison between theoretical-  and practical results not possible. Here the plain journal bearings in full film lubrication will have an disadvantage compared to the needle bearings regarding the power lost. To reduce the drag below the values of the needle bearings a modified journal bearing in the area of boundary lubrication with a very low coefficient of friction may be an option. But problems with wear under this condition could most certainly be devastating and must be further investigated with real tests. Out of a efficiency point of view the most suitable bearing position is the gear in the most frequently used area. Here it is assumed to be the 4th gear. A suitable journal bearing design should have a small sliding surface area in order to minimize the viscous drag. To achieve low friction the boundary lubricated area could be a good idea in cases when wear is not a critical factor. To longer the useful life nitrocarburizing is recommended, which both reduces wear and lower the coefficient of friction, in cases of asperites in contact. In order to work under the full film lubricated condition, with neglected wear, the sliding area needs to be large enough to create the required oil pressure.

The basis of the study lies with a newly patented gearbox by cardiologist and inventor Stig Lundbäck. Stig founded CorPower Ocean AB to further develop the gearbox to be used in a wave energy device. The purpose of this project is to develop a concept of a lifting system with CorPower Oceans gearbox that is more energy efficient than a hydraulic lifting system. The goal is to use technology from CorPower Oceans gearbox inversely to perform heavy lifting as an alternative to hydraulics. The project is limited to applying the gearbox and gear rack on a forklift with a lifting capacity of ten tons.The main tool in this project will be the product development process Systems Engineering where only the most relevant parts will be used to develop a concept. Calculations of the strength and dimensions of the gear racks are made to ensure the possibility of this solution.

Time-frequency methods are widely used tools to diagnose planetary gearbox fault under non-stationary conditions. However, the existing time-frequency methods still have some problems, such as smearing effect and cross-term interference, and these problems limit the effectiveness of the existing time-frequency methods in planetary gearbox fault diagnosis under non-stationary conditions. To address the aforementioned problems, four time-frequency methods are proposed in this thesis. As nowadays a large portion of the industrial equipment is equipped with tachometers, the first three methods are for the cases that the shaft rotational speed is easily accessible and the last method is for the cases of shaft rotational speed is not easily accessible. The proposed methods are itemized as follows: (1) The velocity synchronous short-time Fourier transform (VSSTFT), which is a type of linear transform based on the domain mappings and short-time Fourier transform to address the smear effect of the existing linear transforms under known time-varying speed conditions; (2) The velocity synchrosqueezing transform (VST), which is a type of remapping method based on the domain mapping and synchrosqueezing transform to address the smear effect of existing remapping methods under known time-varying speed conditions; (3) The velocity synchronous bilinear distribution (VSBD), which is a type of bilinear distribution based on the generalized demodulation and Cohen’s class bilinear distribution to address the smear effect and cross-term interference of existing bilinear distributions under known time-varying speed conditions and (4) The velocity synchronous linear chirplet transform (VSLCT), which is a non-parametric combined approach of linear transform and concentration-index-guided parameter determination to provide a smear-free and cross-term-free TFR under unknown time-varying speed conditions. In this work, simple algorithms are developed to avoid the signal resampling process required by the domain mappings or demodulations of the first three methods (i.e., the VSSTFT, VST and VSBD). They are designed to have different resolutions, readabilities, noise tolerances and computational efficiencies. Therefore, they are capable to adapt different application conditions. The VSLCT, as a kind of linear transform, is designed for unknown rotational speed conditions. It utilizes a set of shaft-rotational-speed-synchronous bases to address the smear problem and it is capable to dynamically determine the signal processing parameters (i.e., window length and normalized angle) to provide a clear TFR with desirable time-frequency resolution in response to condition variations. All of the proposed methods in this work are smear-free and cross-term-free, the TFRs generated by the methods are clearer and more precise compared with the existing time-frequency methods. The faults of planetary gearboxes, if any, can be diagnosed by identifying the fault-induced components from the obtained TFRs. The four methods are all newly applied to fault diagnosis. The effectiveness of them has been validated using both simulated and experimental vibration signals of planetary gearboxes collected under non-stationary conditions.

Performing condition monitoring related tasks on any machinery is an essential element of their rational maintenance. Endeavours to detect an incipient fault within a system serve multiple purposes from increasing the safety of people responsible for operating the machines through decreasing the running and operational costs, allowing time to plan for the inevitable repairs and making sure that the downtime of the machine is kept to an absolute minimum. All these tasks gain extra importance in a case when machines are operated in dangerous conditions putting people's lives in potential jeopardy - for instance in the field of operating a helicopter. The robust assessment of the condition of gearboxes used by helicopters has recently been given an increased attention due to a number of accidents which followed an undetected drive train component failure. The majority of the on-board mounted condition monitoring systems use vibration response signals which are specifically processed to obtain a single number which is representative of a condition of a given monitored drive train component. Those signal processing methods are called Condition Indicators (CIs). There are a number of such CIs which are already in use and they seem to adequately indicate faults in most of the cases. However in a number of instances it has been observed that the most popular parameters like Crest Factor or FM4 failed to dependably reflect the true condition of the gear causing serious accidents, some of which resulted in a number of lives being lost. For this reason the presented research is focused on investigating the limitations of the existing CIs and designing a set of improved CIs. The development process is based on overcoming the drawbacks of thetechniques used in existing CIs combined with the intelligence gathered while analysing the acceleration vibration signals which contained a gear or a bearing fault. Five new CIs are proposed and the details of their design are documented. Both the existing and the proposed CIs are applied on the available, uncorrelated datasets. The results of the comparison show that the newly developed CIs are capable of indicating a gear or a bearing fault in a more robust and dependable fashion. Each proposed CI alone may not be the most robust indicator of the actual condition of the monitored component hence the output from all proposed CIs is combined into a single indication through use of a novel data fusion model. The Combined CI created based on the data fusion model is observed to be more robust compared to each CI alone, hence it may increase the confidence level of the decision making routine and is expected to decrease the number of false alarms. The methods of the existing CIs, the proposed CIs and the data fusion techniques as well as the results of the comparison between the different approaches are present in this thesis.

La conception d’une boîte de vitesses impose le choix initial d’une architecture, solution de principe de l’objet à concevoir. Ce choix s’avère très structurant et a un impact très fort sur les critères de performance de la boîte de vitesse sans que l’ingénieur ait une visibilité claire sur cet impact. Une fois l’architecture choisie, il est possible par des techniques d’optimisation continue d’optimiser les critères de performance et le respect de contraintes vis-à-vis d’un cahier des charges. Ce genre d’optimisation a pour but de déterminer de manière optimale des dimensions structurantes de la boîte de vitesses comme par exemple les positions des axes de lignes d’arbres dans l’espace ou les diamètres des pignons. L’objectif de cette thèse est d’apporter des techniques scientifiques permettant de choisir l’architecture optimale vis-à-vis de ce cahier des charges. Le développement d’une telle méthode vise à obtenir des boîtes plus performantes, mais également de réduire les temps de développement d’ingénierie en s’assurant par des méthodes scientifiques du respect des contraintes exprimées dans le cahier des charges, et ce dès le choix de l’architecture, chose faite par essais-erreurs dans le cycle de conception habituel. / In the design process of a new gearbox, a choice has to be made between several competing technical solutions referred to as architectures. The purpose of multicriteria architecture optimization is to define the best technical solution in order to meet some given specifications. In the case of automotive gearboxes, the number of technical solutions is so high that it is humanly impossible for an engineer to test every possibility.It is more convenient to computationally generate all the gearbox architectures and select them with an automated analysis of performance and viability for the main criterion. These viable architectures are at this step only described by their kinematic functions, and a second stage considers the discrete spatial positioning of components in order to determine the viable ones for each architecture. Then, the design engineercan compare the viable architectures according to their performance and select the most interesting one.This PhD. propose a novel framework for gearbox synthesis from kinematic specifications and engineering rules and knowledge, using a specific graph as model for gearbox architectures.