Mekanik süspansiyonlu kamyonlarda otomatik dingil indirme sistemi altyapısının oluşturulması
Development of automatic axle drop system for trucks with mechanical suspension
Yazar: OSMAN UĞUR ACAR
Danışman: DOÇ. DR. ERDİNÇ ALTUĞ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kontrol ve Otomasyon Mühendisliği Ana Bilim Dalı / Kontrol ve Otomasyon Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2013
Konu: Mekatronik Mühendisliği = Mechatronics Engineering
Dizin: Dingil = Axle ; Dingil yükü = Axle load ; Kamyon = Truck ; Otomatik hareket düzeneği = Automatic workbench ; Otomatik sistemler = Automatic systems

Özet:
Aşırı ve/veya yanlış yüklenmiş bir ağır yük taşıtının karayollarına ve köprü geçitlerine zarar verdiği ve ömrünü kısalttığı bilinmektedir ve bu durum bir çok araştırmanın sonucunda da ispatlanmıştır. Dingil yükleriyle ilgili her ne kadar karayolları üzerinde denetim noktaları oluşturulsa da ağır taşıtların tamamının denetlenmesi mümkün olmamaktadır. Ağır taşıt sürücülerinin bilinçlendirilmesi ve yasal yaptırımlarla yaşanabilecek olumsuzlukların büyük bir kısmının azaltılabilecek olması ile birlikte dingillere düşen yüklerin kullanıcı inisiyatifine bırakılması olası sorunları da hiç kuşkusuz beraberinde getirecektir. Bu gibi sebeplerden dolayı kamyonlarda dingil ağırlıklarını düzenleyecek sistemlerin bulunmasının bir ihtiyaç haline geldiği düşünülmektedir. Avrupa Komisyonu tarafından hazırlanan Kütle ve Boyutlar yönetmeliği ile ilişkili olarak ülkemizde 2014 yılında, kamyonlarda otomatik dingil indirme sistemlerinin bulunmasının yasal bir zorunluluk haline gelmesi beklenmektedir. Otomatik dingil indirme sistemlerinin ana amacı dingillere düşen yükleri düzenleyerek, dingil yüklerinin yasal sınırların altında kalmasını sağlamaktır. Otomatik dingil indirme sistemi, dingillere düşen yükleri kullanıcıdan bağımsız olarak düzenler. Yasal sınırlara göre düzenlenmiş bir otomatik dingil indirme sisteminin kullanıcı hatalarını ve ihmallerini en aza indirmesi beklenebilir.
Otomatik dingil indirme sisteminin dünya genelinde birçok uygulaması vardır. Yaygın olmasından dolayı genellikle havalı süspansiyona sahip sistemlerde uygulanmaktadır. Havalı süspansiyonu oluşturan bileşenlerin yapısal özelliklerinin hesaplanabilir ve tahmin edilebilir bir karakteristiğe sahip olması otomatik dingil indirme sistemlerinin uygulanabilirliğini artırmakta ve var olan sistemlere uyarlanabilmesini  kolaylaştırmaktadır. Mekanik süspansiyona sahip kamyonlarda ise durum biraz daha farklıdır. Bu tip süspansiyona sahip kamyonlarda yük taşıma kapasitesinin yüksek olmasından ve dayanıklılığından dolayı üst üste dizilmiş yaprak yaylardan oluşan bir yapı yaygın olarak kullanılmaktadır. Ağır yük altında çalışacak dingillere yakın konumlandırılan bir başka dingil, farklı yol koşullarında yük dağılımının daha orantılı yapılabilmesi için terazi benzeri bir yapıyla süspansiyon yapısına dahil olabilir. Bu şekilde oluşan bir süspansiyon sisteminin sahip olduğu karakteristik, bir otomatik dingil indirme sisteminin sahip olması gereken en kritik özelliklerden biri olan ağırlık tahmin mekanizmasını olumsuz etkilemektedir. Bu durum, mekanik süspansiyona sahip araçlarda otomatik dingil indirme sistemi uygulamasının bulunmamasını açıklayabilir.  
Türkiye'nin de dahil olduğu bir çok ülkede, mekanik süspansiyonlu araçların kullanımı daha yaygın olduğundan böyle bir sistemin hayata geçirilmesi hem stratejik açıdan hem de ticari açıdan büyük önem kazanmaktadır. Bu çalışmada mekanik süspansiyona sahip kamyonlar için otomatik dingil indirme sistemi altyapısı oluşturulmuş, simulasyon ve donanım içeren simulasyon gerçekleştirilmiş ve 8x2S dingil düzenine prototip araç üzerinde uygulaması yapılmıştır. 
Otomatik dingil indirme sisteminin deneysel altyapısını oluşturmak için gerçek test prosedürlerinin benzetimi simulasyon ortamında hazırlanmıştır. Uygulamada yapılabilecek veri toplama ve değerlendirme işlemleri  bilgisayar ortamında hazırlanan simulasyon ile yapılmış, algoritma testleri de burada elde edilen ve değerlendirilen verilerden yola çıkılarak donanım içeren çevrim uygulamasıyla hazırlanan simulasyon ortamında gerçekleştirilmiştir. Otomatik dingil indirme sisteminin prototip araca entegre edilebilmesi için gerekebilecek veri toplama yazılımı, yardımcı elektronik devreler gibi bazı ek bileşenler de çalışmaya  paralel olarak tasarlanmış ve birbirine entegre edilmiştir. Bu çalışmanın birden çok disiplini bir araya getirmesi ve otomatik dingil indirme sisteminin mekanik süspansiyona sahip kamyonlara uygulanabilirliğini göstermesi açısından ileride yapılabilecek çalışmalar için faydalı olabileceği göz önünde bulundurulabilir.

Abstract:
In our country and all over the world, highway has a great portion on transportation. Highway is an expensive investment and being protected is important with regard to security and comfort. Deterioration of highways leads to loss of comfort and safe, besides its economical cost. The vehicles loadaed inaccurately and/or transporting heavy load are remarkable factor over deterioration of highways. Overloading these vehicles lead to excessive pressure over unit area of the road and eventually deterioration. To give an example, there exists a study about lowering legal limit of the axles from 13t to 11.5t that may increase durability of the highways up to 32%. 
Mass and Dimension Policy with number of 1230/2012 published by European Commission(EC) is expected to be a legal obligation in our country. Mass and Dimension Policy which will come into force in our country in 2014, is a regulation taking  into consideration safe and environmentally sensitive driving for heavy-duty commercial vehicles. This regulation brings regulations and restrictions to axle loads with respect to dimensions and number of axles of the heavy-duty vehicles. In same regulation, there are some definitions and restrictions for lift axle, as well. Mass and Dimension Policy aims to prevent tire wear when the vehicle is unloaded or lightly loaded and mechanical deformation when the vehicle is fully-loaded besides decreasing deterioration of highways. According to this regulation, maximum load quantity of each axle is limited moving the appropriate liftable axle automatically to shift self position in order to obtain acceptable load distribution as an obligation. 
In the transportation systems having more than two axles, number of axle brings additional cruise cost when the vehicle is unloaded or lightly loaded while increasing cargo capacity. For this reason some manufacturers have presented a system called Lift Axle for the transportation systems like heavy trucks, tractors and trailers. Thus on unnecessary conditions, driver can prevent extra tire wear and fuel consumption caused by friction by lifting related axle(s). However, letting only the driver to control the system may leads to defective usage in some conditions. Some drivers do not drop the axle(s) even weights of the fixed axles exceed limits specified by related policies. Overloading trucks leads to deformation over chassis as well as wearing out suspension system. As a result of that mechanic deformations on the system and deterioration of highways might increase. A similar circumstance can occur by result of inaccurate or unbalanced loading. In this condition, weight of the fixed axles may exceed limits although total weight is under the specified limits. Automatic axle drop system is designed in order to eliminate these negations and aims providing the axle loads are under the specified limits by taking control of the system from driver except some conditions.
Moving the axles automatically with respect to load condition yields to prevents mistakes caused by user. For instance, some drivers do not drop available axles despite load quantity is more than specified value, by asserting tire wear and fuel consumption. This leads danger in mechanical manner and creates concern about cruise safety. Considering the mass and dimensions policy, liftable axles can be lifted position only when the vehicle is unloaded or lightly loaded except on slippery surfaces. This implementation reduce fuel consumption and emission value while prevent tire wear. Likewise, appropriate liftable axles should be lowered (unlifted) position according to load distribution when the vehicle is loaded so that load quantity of each axles will be in the safety limit.  Thus, deterioration of highways can also be reduced while mechanical deformation is reduced, thereby loss of comfort and safe due to deterioration can be reduced. 
Lift axle system comprises air compressor, air bags, valves and some mechanical coupling elements. In such a this system, air compressor provides pressured air to air bags in order to  push or pull the axle so that positioning  in lifted or lowered condition. Valves control the air flow between air bag and air compressor and also air exhausted from air bag. Mechanical elements are inserted appropriately so that the system works properly. 
The user controls this system by controlling valve with a dedicated button which sends to valve convenient electrical signal. Automatic drop axle system steps in at this point to maintain working of the system automatically. Automatic drop axle system includes a controller which decides to whether the axle(s) is required to drop, or not. This decision stage needs to axle loads be calculated. Axle loads can be obtained easily by air pressure of the pneumatic system of trucks having air suspension system. . However this is different in trucks with mechanical suspension. Weight information can be obtained from sensors such as strain gauge, force sensor and some kind of displacement sensors. But these sensors give indirect information and need to extra calculation to implement to the system. Displacement sensors are cheaper than the others but more difficult to calculation because axles are related with other ones and all affected by displacement of chassis. 
There are some applications for the systems having pneumatic suspension; however a solution does not exist in mass production for heavy trucks with mechanical suspension.  In this study, realizing an application of the Automatic Drop Axle System for heavy trucks with mechanical suspension is aimed. 
Automatic Drop Axle System can be applied to trucks with pneumatic suspension easily because of behaviour and characteristics of the components forming pneumatic system. Due to having calculable and predictable structure of the pneumatic suspensions, applicability and adaptivity of the automatic drop axle system  is considerably high. On the contrary, circumstances are quite different on trucks with mechanical suspension. The trucks having such this suspension system leaf springs and its derivates are used commonly because of durabilities and higher capacities. An another axle located nearly with the axle working under heavy load conditions can be included with a libra structure in order to achieve well balanced load distribution. The characteristic of the suspension system such a this structure has negative effect over weight prediction which is one of the most critical properties of the automatic drop axle system. This may be explain the reason why automatic drop axle system does not exist on trucks with mechanical suspension all over the world.    
In many countries including Turkey, trucks with mechanical suspension are commonly used widespread area so that implementing a system such an automatic drop axle system to trucks having mechanical suspension getting more importance in terms of both commercial and strategic manner.
In this study, a backround of automatic drop axle system for trucks with mechanical suspension was constituted, simulation and simulation with hardware in the loop (HIL) system was realized and implemented on a prototype truck having 8x2S axle structure.   
In order to constitute experimental backround of the automatic drop axle system, a simulation has been prepared to simulate real test procedure. In order to estimate the weights of the axles from displacements of the axles with respect to chassis, it is needed to obtain test data comprising displacements and weights of the axles on some different conditions.  Desired test data is getting while loading the vehicles with load having variable weight, recording the amount of displacement of each axle. Data acquisition and evaluation which can be implemented with on prototype vehicle, has realized with a simulation prepared on computer environment. Quantity and coordinates of the load are entered to simulation as input, then axle weights of the vehicle are taken as output from the simulation. 
Data acquisition software has been developed to get test data from the prototype vehicle. In order to implement automatic drop axle system to prototype vehicle some electronical circuit including microcontroller and auxillary electronical circuits have been developed and integrated each other correspondingly.  
Algorithm has tested with hardware in the loop simulation with data acquisited from results of  these simulations. Simulations has been realized with MATLAB/Simulink and TruckMaker software cooperating with a dedicated development electronical circuit. TruckMaker is a vehicle simulation program and used to model the truck all of the aspects, including kinematics and dynamical model besides some environmental details. In test simulation, TruckMaker provides real-time data from the selected vehicle to Simulink and then microcontroller respectively. Simulink  is  used  to modelling vehicle parameters, taking external inputs from a signal resource like a joystick and communicate with TruckMaker software and microcontroller circuit. 
A racecourse has created on TruckMaker in order to test the automatic drop axle algorithm providing rules of Mass and Dimension Policy. Algorithm has tested with hardware in the loop system comprising a microcontroller and joystick. Load conditions and some signals such as button signal of the axles controlling by the driver in real systems has simulated with joystick inputs. Dedicated microcontroller unit decides the axle position(s) of the vehicle considering data getting from TruckMaker through Simulink.     
In the light of the results obtained from this study, it may be said that an automatic axle drop system can be implemented to trucks with mechanical suspension and adapt to various heavy vehicles having different mechanical structures.