Conventional gearbox vibration monitoring techniques are based on the assumption that changes in the measured structural response are caused by deterioration in the condition of the gears in the gearbox. However, this assumption is not valid under fluctuating load conditions, since the fluctuating load will amplitude modulate the measured vibration signal and cause the rotational speed of the system to change. In general monitoring of machines subject to fluctuating load conditions is dealt with by considering the constant load conditions on gearboxes or during free rotational tests. The need to monitor the condition of large gearboxes in mineral mining equipment has attracted greater interest in order to improve asset management. An inherent need for signal processing techniques, with the ability to indicate degradation in gear condition, under fluctuating load conditions exist. Such techniques should enable the online monitoring of gearboxes that operate under fluctuating load conditions. A continued flow of up to date information should consequently be available for asset and production management. With this research, a load demodulation normalisation procedure was developed to remove the modulation caused by fluctuating load conditions, which obscures the detection of an incipient gear fault conditions. A rotation domain averaging technique is implemented which combines the ability of computer order tracking and time domain averaging to suppress the spectral smearing effect caused by the fluctuation in speed, as well as to suppress the amplitude of the vibration which is not synchronous with the rotation of the gear shaft. It is demonstrated that the instantaneous angular speed of a gearbox shaft can be utilised to monitor the condition of the gear on the shaft. The instantaneous angular speed response measurement is less susceptible to phase distortion introduced by the transmission path when compared to conventional gearbox casing vibration measurements. A phase domain averaging approach was developed to overcome the phase distortion effect of the transmission path under fluctuating load conditions. The load demodulation normalisation and rotation domain averaging signal processing procedures were applied to both the conventional gearbox casing vibration and instantaneous angular speed measurements prior to the calculation of a smoothed pseudo Wigner-Ville distribution of the data. Statistical parameters such as the energy ratio were calculated from the distribution. These parameters could be monotonically trended under different load conditions to indicate the degradation of gear conditions. / Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2005. / Mechanical and Aeronautical Engineering / unrestricted

A new invention has been developed by CorPower Ocean; a mechanical rack and pinion solution called a cascade gearbox. The primary function of the gearbox is transforming a linear motion into a rotational motion. The novelty is its unique properties; it is capable of combining heavy loads and high velocities, and at a high efficiency. CorPower Ocean is aiming at finding applications where the gearbox’s unique properties can be of use. If the gearbox is combined with a motor it forms an electromechanical actuator. Therefore, an investigation of applications using actuators has been targeted. More specifically, the master thesis assignment was to examine in which applications the transition of a cascade electromechanical actuator was technically viable. Research questions that derived was to answer if an implementation of an cascade electromechanical cylinder is technically feasible and if it implicates improved results regarding environmental related goals. The methodology executed to finalize the project included several stages. The first stage was the background study which consisted of reviewing trends and gathering technical data for case studies of targeted applications. The targeted applications were heavy lifting equipment and injection molding machines. With the help of CorPower software, gearbox dimensioning examples were drafted and could be evaluated from a size and weight perspective. To further evaluate potential applications, interviews were conducted with targeted equipment manufacturers. The selection of applications was completed by evaluating the interview responses and the drafted gearbox examples. Chosen applications were ultimately a nine tonnes forklift and an empty container handler, mainly due to good customer response, integration ability and potential of performance enhancement. An optimisation was performed to achieve a concept solution that satisfied customer needs such as low cost and a slim design. In order review the business cases in each application, energy savings and performance cases were conducted, benchmarking against the hydraulic solution. In the ECH case, the energy saved was 54% and the productivity increased with 9.6%. In the forklift case, the energy saved was 52% and the productivity increased with 1%. Both of applications have great potential of a transition from hydraulic cylinders to electromechanical cylinders in terms of implementation and technical feasibility. The final concept solutions exceeded the hydraulics in performance, retaining a slim and acceptable size and design. Furthermore, this sector of heavy lifting equipment had high potential for electrification which can contribute to reduced emissions and fuel savings. Keywords: electromechanical cylinders, concept development, cascade gearbox / En ny innovation har utvecklats av CorPower Ocean; en mekanisk rack och pinjonglösning kallad kaskadväxel. Dess primära funktion är att transformera en linjär rörelse till en roterande rörelse och vice versa. Nyhetsvärdet är växellådans unika prestanda; den kan hantera kombinationen av höga laster och höga hastigheter till en hög verkningsgrad. Nu önskar CorPower Ocean att hitta applikationer där kaskadväxelns unika prestanda kommer till användning. Om kaskadväxeln kombineras med en motor bildas en elektromekanisk aktuator, och därför har en utredning av applikationer som använder aktuatorer utsetts som en marknad att undersöka närmare. Mer specifikt var examensuppdraget att undersöka i vilka applikationer en sådan övergång skulle vara genomförbar ur ett tekniskt perspektiv. Forskningsfrågor som önskades besvaras var huruvida en sådan övergång är genomförbar ur ett tekniskt perspektiv och om en sådan implementation innebär förbättringar vad gäller miljörelaterade mål. Metodologin som användes för att slutföra projektet utgjordes av flera steg. Första steget var att genomföra en bakgrundsstudie om elektrifiering och produkttrender samt samla teknisk data på utsedda applikationer. De utsedda övergångsområdena var maskiner för tunga lyft samt plastformssprutningsmaskiner. Med CorPowers mjukvara kunde dimensioneringsexempel göras för kaskadväxellådor och utvärderas utifrån sin storlek och vikt. För en fortsatt utvärdering av applikationer genomfördes intervjuer med tillverkare av de utsedda applikationerna. Val av applikationer slutfördes genom att utvärdera svar från målkunder samt dimensioneringsexempel av växellådorna. De valda applikationerna blev slutligen en nio tons gaffeltruck och en tomcontainertruck. Valet baserades huvudsakligen på bra respons från kunder, bra integrationsmöjligheter samt potentiella prestandaförbättringar. Fokus låg på att byta ut lyftcylindrarna och bortse från övriga mindre cylindrar. Lösningarna optimerades för att matcha kundkrav så som kostnad och passform. Ett energibesparingscase utfördes för att jämföra kaskadlösningen med nuvarande hydrauliska lösning. I tomcontainertruckens fall sänktes energiförbrukningen med 54 % och produktiviteten ökade med 9.6%. I gaffeltruckens fall sjönk energiförbrukningen med 52 % och produktiviteten ökade med 1 %. Båda applikationerna uppvisade stor potential för ett byte från hydraulcylindrar till elektromekaniska cylindrar. De slutgiltiga koncepten överträffade hydraulikens prestanda medan de bibehöll en acceptabel storlek. Vidare fanns det en stor potential inom lyftindustrin att genom elektrifiering kunna minska utsläpp och bränsleförbrukning. Nyckelord: elektromekanisk cylinder, konceptutveckling, kaskadväxel

Nowadays Snecma focuses on new engine architectures in order to meet the future demands in civil aviation. One of these considered concepts is aircrafts powered by counter rotating fan engines which aim at tackling both noise and polluting emissions. A powerful way to reduce the perceived noise is to reduce the fan rotating speeds, which requires to lower fan pressure ratio. This thesis continues a study on an innovative counter rotating fan architecture carried out by Snecma from 2005 to 2010 for VITAL (European Commission funded project). It is a way to meet the noise target while maintaining acceptable engine dimensions and matching installation constraints since each fan has a smaller diameter than the current ones, and an individual low pressure ratio. Therefore the drag is decreased and less fuel is burnt. In order to fulfill these ambitious objectives, the first step of this thesis is to use the code of the VITAL model developed with Janus (Snecma in-house code) in order to create a new code for the PROOSIS software. When modeling two counter rotating fans, the key point is to take into account the influence from the first stage on the second one.  Since the aft fan “sees” a perturbed flow by the inlet fan wake, its characteristic map is not the usual one anymore. One major challenge was the new design of a two separated flow and three-spool counter rotating engine driven by a gearbox which meets the very high bypass ratio target. The model finally turned out to be operational for a relevant set of initialization parameters and thus makes now possible more accurate studies on counter rotating turbofan engines in the R&T unit.

Mississippi State University was selected for participation in the EcoCAR 3 Advance Vehicle Technology Competition. The team designed its architecture around the use of two UQM electric motors, and a Weber MPE 850cc turbocharged engine. To combine the three inputs into a singular output a custom gearbox was designed with seven helical gears. The gears were designed to handle the high torque and speeds the vehicle would experience. The use of this custom gearbox allows for a variety of control strategies. By optimizing the torque supplied by each motor, the overall energy consumption of the vehicle could be reduced. Additionally, studies were completed on the engine to understand the effects of injecting water into the engine’s intake manifold at 25% pedal request from 2000-3500 rpm. Overall, every speed showed an optimum at 20% water to fuel ratio, which obtained reductions in brake specific fuel consumption of up to 9.4%.

This master thesis has been performed by a request from Scania CV AB in Södertälje. Scania CV AB is a global company manufacturing heavy vehicles, such as busses and trucks. When developing a gearbox, an endurance test is made that shows failures, such as damaged gears or bearings. STP and delta-ANALYSER are used to discover this kind of failure. STP is developed by Scania CV AB, and it measures the vibration, oil pressure, temperature, etc. delta-ANALYSER is developed by Reilhofer. It is a measuring system that detects failures in the gearbox by comparing the vibrations with a reference. The main issue is that these tests are time consuming. The goal is to cut time and still be able to follow the results more accurately and in an early stage receive failure reports from bearings and gears. Accelerate the tests is not possible, because the test-rig is already heavily accelerated. The purpose of the thesis is to investigate existing methods for a more precise detection of a damage that has reached a certain size, also be able to isolate the source of a defect to a specific gear. In this thesis project different methods for detection of damages has been identified: vibration, thermography, acoustic emission, ultrasonic, oil analysis, etc. After an internal discussion, a combination of two methods: oil analysis and vibration, were chosen. Companies demonstrated their oil analysis systems. Advantages and disadvantages were discussed and it was decided to continue with an oil particle sensor, OPCom FerroS, from ARGO HYTOS, that detect the oil particles with a magnet in the flow of oil. The final system for detection of damages is a combination of OPCom FerroS and Scania’s current system: delta-ANALYSER and STP. The developed detection system was evaluated by the set system requirements, showing that the system meet 22 of the 33 tested requirements. All requirements could not be verified and needs more investigation and tests. / Detta examensarbete har utförts på uppdrag av Scania CV AB i Södertälje. Scania CV AB är ett globalt företag som tillverkar tunga fordon, såsom lastbilar och bussar. Vid utveckling av en växellåda, är ett livslängdsprov genomfört för att upptäcka typiska fel, t.ex. skadade kugghjul eller lager. Idag används två system, STP och delta-ANALYSER, för att upptäcka fel. STP har utvecklats av Scania CV AB, och det används för att mäta vibration, oljetryck, temperatur, etc. Delta-ANALYSER är framtaget av Reilhofer. Det är ett mätsystem som detekterar fel i växellådan genom att jämföra vibrationer med en referens. Det största problemet är att dessa system är tidskrävande. Målet är att förkorta provtiden men fortfarande erhålla tydliga resultat och i ett tidigt stadium erhålla en rapportering av skador på lager och kugghjul. Det är inte möjligt att accelerera proven eftersom provriggarna redan är kraftigt accelererad. Målet med examensarbetet är att göra en undersökning av befintliga system som kan tänkas vara användbara för tidig detektering av utfall kopplat till en viss storlek och kunna isolera felkällan till en viss del av växellådan. I detta examensarbete har flera tekniker för detektering av skador identifierats: vibration, termografi, akustisk emission, ultraljud, oljeanalys, etc. Efter en intern diskussion så valdes det att kombinera två olika tekniker, oljeanalys och vibration. Flera olika företag som jobbar med oljeanalys demonstrerade sina system. Fördelar och nackdelar diskuterades och det valdes att gå vidare med en oljepartikelsensor, OPCom FerroS, från ARGO HYTOS, som med hjälp av en magnet i oljeflödet kan detekterar oljepartiklar. Det slutgiltiga systemet för detektering av skador blev en kombination av OPCom FerroS och Scanias nuvarande system: delta-ANALYSER och STP. Det utvecklade detekteringssystemet utvärderades med de ställda kraven och det påvisade att systemet uppfyller 22 av de 33 testade kraven. Alla krav kunde inte verifieras och kräver vidare undersökningar och tester.

The reliable operation of planetary gearboxes is critical for the sustained operation of many machines such as wind turbines and helicopter transmissions. Hybrid methods that make use of the respective advantages of physics-based and data-driven models can be valuable in addressing the unique challenges associated with the condition monitoring of planetary gearboxes. In this dissertation, a hybrid framework for diagnostics and prognostics of planetary gearboxes is proposed. The proposed framework aims to diagnose and predict the root crack length in a planet gear tooth from accelerometer measurements. Physics-based and data-driven models are combined to exploit their respective advantages, and it is assumed that no failure data is available for training these models. Components required for the implementation of the proposed framework are studied separately and challenges associated with each component are discussed. The proposed hybrid framework comprises a health state estimation and health state prediction part. In the health state estimation part of the proposed framework, the crack length is diagnosed from the measured vibration response. To do this, the following model components are implemented: A first finite element model is used to simulate the crack growth path in the planet gear tooth. Thereafter, a second finite element model is used to establish a relationship between the gearbox time varying mesh stiffness, and the crack length in the planet gear tooth. A lumped mass model is then used to model the vibration response of the gearbox housing subject to the gearbox time varying mesh stiffness excitation. The measurements from an accelerometer mounted on the gearbox housing are processed by computing the synchronous average. Finally, these model components are combined with an additional data-driven model for diagnosing the crack length from the measured vibration response through the solution of an inverse problem. After the crack length is diagnosed through the health state estimation model, the Paris crack propagation law and Bayesian state estimation techniques are used to predict the remaining useful life of the gearbox. To validate the proposed hybrid framework, an experimental setup is developed. The experimental setup allows for the measurement of the vibration response of a planetary gearbox with different tooth root crack lengths in the planet gear. However, challenges in reliably detecting the damage in the experimental setup lead to the use of simulated data for studying the respective components of the hybrid method. Studies conducted using simulated data highlighted interesting challenges that need to be overcome before a hybrid diagnostics and prognostics framework for planetary gearboxes can be applied in practice. / Dissertation (MSc)--University of Pretoria, 2021. / Eskom EPPEI / Mechanical and Aeronautical Engineering / Msc / Unrestricted

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