Kablosuz ve akülü  mobil lift tasarımı
Design of wireless and battery powered mobil lift
Yazar: YUSUF TİTİZ
Danışman: DR. ÖĞR. ÜYESİ ATAKAN ALTINKAYNAK
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Mekatronik Mühendisliği Ana Bilim Dalı / Mekatronik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2018
Konu: Mekatronik Mühendisliği = Mechatronics Engineering
Dizin: Elektrohidrolik sistemler = Electrohydraulic systems ; Makine tasarımı = Machine design ; Otoliftleri = Autolifts ; PLC = Programmable logic controller

Özet:
Mobil lift;  karayolları, demiryolları ve savunma sanayi araçlarının bakımında en yaygın kullanılan kaldırma ekipmanıdır. Araçların alt donanımında tamir edilmesi gereken bir parçanın sökülme işi, süspansiyonların kontrolü veya aracın yağ değişimi aracın kaldırılmasına bağlıdır. Mobil liftler ile bir aracın her türlü bakım işleri yapılabilmektedir. Mobil lift, bakımı veya testi yapılacak aracın kaldırma noktası, aks sayısı ve ağırlığına göre farklı tasarımlarda üretilmektedir. Tüm mobil liftler, EN 1493 'Vehicle Lifts' ve EN 1494 'Mobile or movable jacks and associated lifting equipment' standartlarına uygun olarak tasarlanıp imal edilmektedir. 
Kaldırma ekipmanın tahriki, redüktöre bağlı sonsuz ( trapez ) bir mil veya hidrolik silindir ile gerçekleştirilmektedir. Araç; gövdeden veya tekerden kaldırılmasına göre, kaldırma noktası kadar birbirinden bağımsız, bir motor veya hidrolik üniteye sahip sütunların birbirleri ile eşzamanlı çalışması ile kaldırılır. Örneğin sekiz kaldırma noktası olan veya dört akslı bir araç toplamda dört adet mobil lift ile kaldırılmaktadır. Sekiz sütundan biri ana sütun olarak belirlenip, enerji beslemesi bu sütuna getirilir. Tüm güç ve iletişim kabloları bu sütunun sahip olduğu ana panodan diğer sütunların panolarına dağıtılmaktadır. 
Teknolojinin gelişmesi ile birlikte; mobil liftler, bu sütunlar arası kablo karmaşasını önlemek için her bir sütun kendi aküsüyle çalıştırılmakta ve iletişim için (senkronizasyon, yük alma, somun aşınma, kilit vs.) birbirleri ile kablosuz modül vasıtasıyla haberleşmektedir. 
Kablosuz çalışacak mobil liftlerde genelde tasarım hidrolik sisteme yoğunlaşmaktadır. Hidrolik liftler, mekanik ( trapez milli tahrikli) liftlere göre daha az enerji harcamaktadır. Otoblokajlı trapez millerin verimi %50'den düşük olduğundan ve inişte de motorun çalışmasından dolayı hidrolik mobil lifte nazaran daha fazla elektrik enerjisine ihtiyaç duymaktadır. Ayrıca sütun konstrüksiyonu mekanik liftlerde flambaja maruz kaldığından daha mukavemetli imal edilmek durumundadır. 
Bu çalışma; akülü ve kablosuz olarak çalışacak 4 sütunlu hidrolik mobil liftin, konstrüksiyon hesaplarını, hidrolik sistemini ve sistem yazılımını içermektedir. Liftin mukavemet hesapları ANSYS programında yapılıp, sütun ve taşıyıcı kesitleri belirlenmiştir. Hidrolik sistemin modellenmesi ise FLUIDSIM programı ile yapılmıştır. Liftin enerji beslemesi akü ve bunu şarj edecek bir akü şarj cihazı sağlanmıştır. Liftin kaldırma yüksekliği sinyal kodlayıcı (enkoder) ile takip edilirken, dört sütun arasındaki iletişim PLCler üzerinden ethernet modülünden sağlanmaktadır.

Abstract:
Mobile lift is one of the most widely used lifting equipment for road, railways and defense industry vehicles. In order to perform several maintenance operations such as dismantling a component from the underbody of vehicle to be maintained, controlling suspensions or as the simplest term, oil changing, the vehicle shall be lifted. Mobil lifts are manufactured with different designs varying to the extent of lifting points, axle numbers and weight of the vehicle to be maintained or tested. All kinds of maintenance operation of a vehicle can be performed with mobile lifts. All mobile lifts have to be manufactured by designing in accordance with EN 1493 'Vehicle Lifts' and EN 1494 'Mobile or movable jacks and associated lifting equipment' standards. 
The drive of mobile lifts can be accomplished by a 	worm spindle directly attached to motor reducer or a hydraulic cylinder. With regard to lifting vehicle from tires or lifting points located onto vehicle chassis, lifting vehicle is carried out by separately actuated by motor or hydraulic unit mobile lifts with equal number with lifting points or tires which have to be operated synchronously. For instance, a vehicle having eight lifting points or four axes has to be lifted with eight mobile lifts. One of these eight mobile lifts is determined as a master lift and main power supply is provided to this one. All power and communication cables are delivered to other lifts from the control panel of master lift. 
Mobile column lifts are being manufactured with different rated load varying from 2,5tons to 40tons. Thanks to its reliable and safe design, such a high rated load can be achieved to be lifted. Design can be customized according to the lifting point (tire or chassis), maintenance needs or user's requirements. With apparatus and accessories, different lifting style can be accomplished. With regard to lifting style, mobile column lifts can be divided into two design; tire lifting and chassis lifting. In tire lifting design, carrier has forks to grab tires of vehicle. In order to lift vehicles having different tire diameter, mobile column lift can be designed in such a manner that distance between forks can be aligned.  In chassis lifting, carrier has a pawl to contact with lifting point existing on vehicle chassis. Lifting pawl can be extended with a gear mechanism to reach lifting point which is too far from vehicle body. It is not required to change design for columns, drive mechanism and safety devices for lifting style. With slight changes in carriers, different lifting style can be accomplished. 
Mobile column lifts can be equipped with different safety devices. Limit switches, load sensing switch, pallet jack sensor, load nut wearing switch for lifts driven with worm spindle, overload switch, mechanical safety clutches are some safety devices to be used in mobile column lifts. Requirements of safety devices are specified within related standards. Thanks to these safety devices, inadvertent usage and improper operations can be inhibited. Before design stage, all possible risks shall be determined and required actions to remove those risks shall be propounded. Thereby, mechanically safe and reliable design is promoted with these safety devices against operator's errors and misuse. 
Synchronization can be considered the crucial point of operating mobile column lifts. Several mobile column lifts having their own drive units have to be operated as single machinery. A malfunction in synchronization may cause vehicle's overturning which may be concluded with death or severe damages. Electronically equipped mobile columns lifts for simultaneous operation also have to be observed by operator during their movement. In case of any doubt over simultaneous operation, mobile column lifts have to be stopped with emergency stop button provided on each column. 
Mechanical synchronization such as with rope, with hydraulic displacement or with a leveler cannot be applied to mobile column lifts due to that they are not stable. Accordingly, each column is provided with encoder tracking carrier height continuously. Lifting height can be counted and compared by logic controller. Should difference between carriers exceeds allowable value; leading carrier is stopped until other ones reach them. 
Information of heights, safety devices' cases and warnings between columns can be shared with communication cables. Up to number of information to be shared, cores of cable shall be determined. Cables of each column having power supply and safety signals are attached to control panel. With regard to safety devices and lifting height, power supply can be cut. 
With the improvement of technology; in order to remove muss of cables; mobile lifts can be manufactured as so they can be powered by its own battery and communicate with other columns via wireless module. Hence, a safe working environment is enabled. Cables laid on floor of workshop may pose a threat to operators and these cables can be squashed by vehicles, so that a malfunction in system may arise. 
The design of wireless mobile lifts tends to be hydraulic due to that hydraulic lifts spends less power than mechanical lifts (trapezoidal spindle system). Due to that efficiency of lifts having auto-blocking is less than %50 and spend power at lowering as well, mechanical lifts require more power than hydraulic lifts. Besides this, mechanical lifts are exposed to buckling, that's why columns are to be manufactured with section having more strength.
Present study consists of structural calculations in accordance with related standards. How to determine design load is indicated within this study. Practical structural calculation was compared with analyses performed with ANSYS Workbench. Both results are compared to allowable stress specified within standards.
Hydraulic system of design including practical calculations, valve block design and simulation of hydraulic scheme was explained in this study. Practical calculations and the results of simulation were compared too. Valves to be used in system were described and their duties in system were shown in hydraulic schemes. 
Power supplies and control of lift were addressed in the study. How to selecting batteries and auxiliary equipment promoting power supply is mentioned too. Working principle of system is discoursed. 
Safety devices and accessories including locking system, encoder system and pallet truck system were also addressed. Design criteria and requirement of them was examined in this study. 
How to associate physical components and controller of system was explained. Design allows system to be added with different physical components such as oil level sensor of hydraulic system, load cell, photocell etc. promoting unit more safe and reliable.  
Lifting height is controlled with an encoder and communication between four columns is achieved through ethernet modules of PLCs which is different application than usual market solution. PLC structure of design was given in this study, and how to create ladders of PLC for such a system was described. Sharing inputs, outputs and settings of PLCs were also shown. 
Design within this study enables a communication not intervened with signals of different equipment. Ethernet communication provides an isolated network for mobile column lifts. 
Study includes possible future workouts which can promote design of mobile columns lifts. With this design, purposes of simultaneous operation's hitches (pressure regulations, defects of manufacturing processes, frictions, backlashes)   can be examined.