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2KBS-3H Deposition machine2.1GeneralThe KBS-3H deposition machine is a prototype machine based on a water cushion technique for lifting andtransporting the Supercontainer in stepwise movements inside the drift. The lifting and pushing sequence isrepeated until the Supercontainer reaches its’ destination in the drift.The deposition machine forms a complete unit with the lifting pallet and the sliding plate, figure 2-1. Thelifting pallet and sliding plate are moved in turns to make the stepwise motion. The machine body runs onwheels while moving the sliding plate which is directly attached to the machine body. The lifting palletwhich is attached to the radiation shield is moved using linear actuators between the machine body andthe radiation shield as the machine is standing still.The lifting pallet is guided on the sliding plate by guiding profiles on the sides of the sliding plate, keepingthe whole unit lined in the drift. The lifted Supercontainer is kept in balance by a counterforce produced bythe masses of the machine body and a counterweight ballast that can be adjusted sideways. The balancingforce is brought to the lifting pallet as a torsional force over the linear actuators between the machine bodyand the shield. The machine body is centered in the drift by steering with the wheels. The wheel axles areinterconnected and mounted to the machine body on spherical bearings allowing active steering of thebody by turning the axles. The steering is actuated by driving the wheels on each side with different speedsto adjust the angle of the interconnected axles relative to the machine body.Figure 2-1. The main functional parts of the horizontal deposition machine.The deposition machine is parked on a start tube outside the deposition drift while not in operation.Between the start tube and the drift there is a space for the transport tube in which Superconatiners anddistance blocks are transported to the deposition site, Figure 2-2. To be able to move the transport tube tothe drift opening the start tube with the deposition machine must first be moved aside. The machine islonger than the start tube and therefore the sliding plate and lifting pallet are detached and pushed underthe machine before the start tube can be moved. When the transport tube and start tube are placed inposition for deposition, they are aligned with the drift using adjustable position blocks. Finally the slidingplate and lifting pallet are pulled forwards and attached to the machine again. Alignment of the tubes is9

important for the sliding plate and machine to pass the transition points from start tube to transport tubeand the transport tube to the drift.Figure 2-2. Placing of transport tube and start tube outsidethe drift. The tubes stand on transport supports which areadjusted to correct position and height with the position blocks on the ground.During functional testing of the KBS-3H deposition machine in 2007-2009 it became apparent that themachine was not ready for performance evaluation of the horizontal deposition concept. Some mechanicalenhancements were done in parallel with previous testing, /SKB R-08-43/ but it was clear that the machinesuffered from greater control problems than mechanical enhancements could solve. A software analysisproject was conducted in 2010, which resulted in a set of corrective recommendations. Correction of the control software structureInstrumenting the machine to gain complete knowledge of its’ behaviourInvestigation of machine behaviour by testing and dataloggingDesigning an actuation system to gain complete controllabilityDevelopment of a new control method for the machine balancingIt was discovered that the distributed control software was built together from software modules with aninadequate overall view resulting in an overcomplex structure, partially overlapping functions anddiscontinuous functional sequences. The software was also not finalised in terms of functional exceptions,error handling and error recovery which often led to unexpected and irrecoverable jamming situations.Since the operators could not see the reasons for the stops on the user interface, they soon adapted toerror handling by experimental manual operation and consequently the error reports containedassumptions that were of limited value.10

Beside the structural problems in the control system, a more serious problem was the recurring imbalanceof the machine. As the machine could not keep the load in balance in all situations, but drifted intoirrecoverable imbalance from time to time and did obviously not fulfil the design objectives. The machinecould work well for certain periods after calibration of pallet and sliding plate, but situations wouldeventually come when the machine could not maintain the balance. Understanding of this problem was notclear and the operators did also not have any rules for correct calibration of the machine. As a consequencethe operators again adapted to the problem by experimenting how to manually bring back the machineinto balance. A normal balancing operation being a few strokes of reverse driving in hope of returning intobalance. Clearly, solving this problem was the main challenge of this project as the machine was supposedto work automatically without repeated manual intervention.Based on previous observations of the balancing problem /Halvarsson B, 2008/ it was concluded thatalignment of the sliding plate and the lifting pallet with the drift is of high importance for the balancing.Further, it was found that the cushions are sensitive to load variations and a too uneven weight distributionwould lead to unmanageable problems. It was concluded that it is of highest importance that the liftingpallet is accurately placed underneat the Supercontainer and the proposed corrective actions were betterfixation of the lifting pallet and sliding plate to the machine for a more rigid and straight machine structure.However, based on the software analysis in 2010 it was concluded that the insufficient ability of the controlsystem to control the mechanics was a more severe problem than the lack of rigidity in the mechanics.By the start of this project it was decided that the old software, despite many flaws, contained much usefulcode and should be corrected instead of writing an entirely new application. The project was thereforestarted by further investigating the structure of the software and documenting the starting point of thecode before doing the rebuilding work. Simultaneously the instrumentation of the machine was expandedto cover its’ behaviour as comprehensively as possible and an efficient logging system was applied toenable thorough functional investigation. Mechanically the deposition machine was considered well suitedfor the work, though somewhat worn or deformed in some parts so no significant changes were planned,only minor repair and overhaul tasks.11

2.2RequirementsThe requirements set in the project were primarily to ensure a consistent and reliable function of thehorizontal deposition machine. The reliability should be on such a level that repetitive driving could beperformed to demonstrate that the horizontal deposition principle is working and that a realisticperformance evaluation and safety analysis could be done. The functionality should be on such a level thatdeposition of the Supercontainer and distance blocks in the MPT demonstration could be safely carried outwithin the time restrictions posed by the project schedule.The original functional requirements for the machine were given as reference for this project. It was soonrealized that the machine control software was not fully corresponding to the requirement specificationsand that all requirements could not be completely met. The project therefore started by matching thesoftware to the specifications in order to define and prioritize the required corrective actions.High priority was given to requirements on control ability from the operators interface feedback to the operators interface automation level of the machine functional reliability of the system functional safety of the system fulfilment of all occurring deposition situationssince these requirements strongly affect the usability of the machine and are directly related to thesoftware application. Lower priority was given to requirements on load capacity deposition speed powering adequacy other physical or mechanical requirementsas these requirements are more related with the mechanics and components of the machine and mainlyfall outside the software scope of this project.Not all specified requirements have been fulfilled by the end of this project due to limited time andresources. However, despite a rather limited testing period the machine control now has all the requiredfunctionality and can be considered consistent enough for repetitive performance testing and for the MPTdeposition work. The operators interface provides the necessary command functions and error handling,but is not finalized in terms of visualization and commanding functionality. These appearance requirementshad to be left with lower priority.12

3Updates3.1Hardware UpdatesThe mechanical overhaul of the machine was planned simply to get rid of troublesome disturbances causedby wear and deformation as well as corrosion and dirt. Only a few mechanical changes were planned withfunctional enhancement in mind. The main hardware update aimed at instrumenting the machine for acomplete behavioural investigation focussing on solving the balancing problem. A hardware work notanticipated beforehand, but necessary in order to ensure reliable operation was a partial rebuild of theelectrical system.3.1.1Basic Mechanical UpdatesStraightening the start tubeThe start tube had been deformed so that it was shaped somewhat like a hammock. The result was that thepath of the machine over the transport tube and start tube into the drift did not constitute a straight line.As a result, the height and angle of the start tube could not be adjusted to eliminate a harmful stepbetween the transport tube and start tube. The machine always jammed in one way or the other whenattempting to drive in under the Supercontainer in the transport tube.Since the start tube is a rather complicated welded structure with unknown internal strains and the shapeis difficult to measure and verify on site it was decided not to modify the structure itself. Instead, thedistance between the wheel tracks of the start tube and a straight liner were measured over the wholestart tube and the wheel tracks were straightened by adding steel plates of different thicknesses along thewheel tracks. Steel plates of 2 and 3 mm thickness were combined in one to four layers on top of eachother in order to form straight wheel tracks. The plates were mounted onto the start tube withcountersunk screws for easy removal and further adjustment. The shapes of the wheel tracks beforestraightening and consequently the amount of filling are presented in figure 3-1.1098filling [mm]7654321001432distance from transport tube [m]56Figure 3-1. Thickness of steel filling on wheel tracks of start tube, blue – right track, red – left track.13

The work resulted in a reasonably straight start tube and the jamming problems when driving the slidingplate and pallet in under a Supercontainer in the transport tube could be reduced remarkably.Sliding plate overhaulThe sliding plate is constantly dragged on the rock surface of the drift and then kind of rolled by the slidingSupercontainer. During every stroke the sliding plate is differently supported by the drift bottom andtherefore the rolling forces deform the plate in different ways. Since the lifting cushions slide on the middlepart and the sliding plate has stiff box type structures in each end the plate is slowly deformed into ahammock shape. Figure 3-2 shows the two cushion tracks on the plate. Since the front end of the slidingplate is a stiff box-type structure it keeps its’ shape. As a result the sliding plate tends to lift its’ front endfrom the drift bottom causing an extra space requirement between the drift bottom and theSupercontainer. Another result is that the front end of the sliding plate is not stably supported over its’whole width by the drift bottom and tends to wiggle somewhat depending on which side the main weightlies on. This is causing some inaccuracy in the angle detection of the front of the sliding plate. It wastherefore planned that the sliding plate should be reshaped as part of the machine upgrade. However, thesliding plate is a very large structure and reshaping of the macro deformation could not be done at site.Instead some local deformations caused by stones or local bending caused by the step between the starttube and the transport tube were repaired, figure 3-3. To avoid excessive wear of the cushions scratches onthe upper sliding surface of the plate were removed by polishing.Figure 3-2. The sliding plate is deformed by the pressure from the cushions. The metal sheet is clearly stretched at thetwo cushion tracks.14

Figure 3-3. A heavy load has stamped the shape of the underneath drift surface into the metal sheet.Assembly of sliding plate coll

software application has suffered from unexpected functional stops and the system has not been able to fully control the balancing of the load. In order to ensure reliable deposition of the components in the MPT experiment the control system of the horizontal