POLITECNICO DI TORINO Master of Science in Automotive Engineering Panda 4WD - Hybrid: design and analysis of a new suspension system for a hybrid vehicle for rally competitions Tutor Candidate Prof. Stefano Carabelli Riccardo Breda Academic year 2018/2019 INDEX 1. INTRODUCTION ....................................................................................................... 8 1.1. Objective ...................................................................................................... 8 1.2. Work steps ................................................................................................... 8 1.3. Panda Raid competition ............................................................................. 11 2. TRADE-OFF ANALYSIS BETWEEN 2WD AND 4WD STARTING PLATFORMS .................................................................................................................................... 14 2.1. 2WD and 4WD preliminary considerations .............................................. 14 2.2. Transmission system of the 4WD Panda ................................................... 15 2.3. Transmission system of the 2WD Panda ................................................... 26 2.4. Possible hybridization strategies for the Panda 4WD ............................... 29 2.4.1. Modification of the rear rigid axle with the installment of a transaxle ……………………………………………………………………….29 2.4.2. Installment of an electric motor and gearbox along the transmission shaft ……………………………………………………………………….31 2.5. Possible hybridization strategies for the Panda 2WD ............................... 44 2.5.1. Ω shape geometry modification ......................................................... 45 2.6. Trade-off conclusions ................................................................................ 49 3. DESIGN OF THE NEW REAR SUSPENSION SYSTEM ...................................... 50 3.1. Creation of the 3D CAD model ................................................................. 50 3.1.1. Old suspension system ....................................................................... 50 3.1.2. New suspension system ...................................................................... 56 3.2. Multibody model for the determination of the loads ................................. 63 3.2.1. Creation of the model ......................................................................... 64 3.2.2. Simulations ......................................................................................... 78 3.2.3. Obtained results .................................................................................. 79 1 3.3. Topological optimization and FEM structural analysis ............................. 84 3.3.1. Analysis of convergence of the results ............................................... 86 3.3.2. Setting of the structural analysis and optimization on the box flange 90 3.3.3. Obtained results .................................................................................. 97 3.3.4. Verification analysis of the new geometry ......................................... 99 3.4. From the engineering phase to the manufacturing process ..................... 101 3.4.1. Creation of the 2D drawings from the 3D models ........................... 101 3.4.2. PDF files ........................................................................................... 104 3.4.3. DXF files .......................................................................................... 107 4. CONCLUSIONS AND FUTURE DEVELOPMENTS ........................................... 108 5. REFERENCES ......................................................................................................... 109 2 FIGURE INDEX Figure 1: Work phases .................................................................................................... 10 Figure 2: Panda Raid [1] ................................................................................................. 11 Figure 3:Panda Raid [2] .................................................................................................. 12 Figure 4: Repairings during the race ............................................................................... 13 Figure 5: 4WD Panda transmission ................................................................................ 15 Figure 6: 2WD and 4WD operation modes .................................................................... 16 Figure 7: Components involved in power flow during 4WD operation ......................... 17 Figure 8: 4WD activation system ................................................................................... 19 Figure 9: Transmission shaft ........................................................................................... 20 Figure 10: Rigid axle suspension (above) and MacPherson (below) ............................. 21 Figure 11: Transmission scheme .................................................................................... 23 Figure 12: Section view of the differential group ........................................................... 24 Figure 13: Bodywork dimensions Panda 4WD .............................................................. 25 Figure 14: Panda 2WD gearbox and differential ............................................................ 26 Figure 15: Rear suspension system Panda 2WD ............................................................ 28 Figure 16: Transaxle group ............................................................................................. 29 Figure 17: Transaxle drive shafts .................................................................................... 30 Figure 18: New powertrain scheme ................................................................................ 31 Figure 19: Engine power and torque curves ................................................................... 32 Figure 20: Gearbox-differential scheme with 5th gear engaged ..................................... 34 Figure 21: Panda 4WD hybridization scheme ................................................................ 36 Figure 22: Electric motor attached to the differential ..................................................... 37 Figure 23: Electric motor attached to the central part of the transmission shaft ............ 38 Figure 24: Electric motor on the first part of the transmission shaft .............................. 39 Figure 25: Components of the front part of the transmission ......................................... 40 Figure 26: 3D model of solution 1 .................................................................................. 42 Figure 27: 3D model of solution 2 .................................................................................. 43 Figure 28: 3D model of the omega tube with the transaxle unit centrally positioned .... 44 Figure 29: New suspension geometry (side view) .......................................................... 45 Figure 30: New suspension geometry (front and bottom views respectively) ............... 46 Figure 31: Old and new design (left and right respectively) .......................................... 47 Figure 32: Front wheel hub ............................................................................................. 48 3 Figure 33: Scan of old suspension with range of motion ............................................... 51 Figure 34: Remarkable points of the suspension ............................................................ 52 Figure 35: Old Panda suspension system ....................................................................... 54 Figure 36: Spring seat and swinging arm attachment to the tube with a flange ............. 55 Figure 37: Detail of the flange connecting the tube to the drum and supporting the damper ........................................................................................................................................ 55 Figure 38: New suspension system ................................................................................. 56 Figure 39: Inclination angle of the new tube design ....................................................... 57 Figure 40: Spring seat detail ........................................................................................... 58 Figure 41: Detail of the pin connecting the damper to the tube ..................................... 59 Figure 42: Old wheel hub (left) compared with new wheel hub (right) ........................ 60 Figure 43: Different geometries for the flange ............................................................... 61 Figure 44: Isometric and orthogonal views of the final version of the flange ................ 62 Figure 45: CAD model of the Panda .............................................................................. 64 Figure 46: Vehicle model with center of mass highlighted in red .................................. 67 Figure 47:Multibody model ............................................................................................ 69 Figure 48: Detail of the rear suspension system ............................................................. 69 Figure 49: Detail of the central attachment point of the tube to the chassis ................... 70 Figure 50: Detail of the spring attachment both on the tube and on the chassis ............ 70 Figure 51: Detail of the swinging arm attachment points ............................................... 71 Figure 52: Detail of the flange in the multibody model 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