Controllable Suspension Design Using Magnetorheological Fluid

Transcription

1 Controllable Suspension Design Using Magnetorheological Fluid Public Defence October 213 Student: Supervisor: Co-Supervisor: Anria Strydom Prof Schalk Els Dr Sudhir Kaul

2 1 Outline Project background MR damper characterization Vehicle modeling and model validation Suspension control Ride comfort simulation and results Handling simulation and results Suspension control results summary Conclusion Recommendations and future work

3 2 Project Background Ride comfort and Handling Trade-off Handling Sudden swerve manoeuvres Hard spring High damping Minimize pitch and roll movement Ride Comfort Minimize driver fatigue Soft spring Low damping Minimize vertical acceleration

4 3 Project Background Passive, Active & Semi-active Damping Magnetorheological (MR) Fluid Active

5 4 Project Background Baja Vehicle Study Purpose: Mitigate ride comfort and handling compromise of Baja vehicle Semi-active suspension control of MR dampers Tasks: MR damper modeling Vehicle model development and validation Implementation of skyhook- and groundhook control Determination of suspension control settings: Rough Belgian paving track Single lane change

6 5 MR Damper Characterization MR Damper Characteristic

7 Force ; F MR ; [N] Force ; F MR ; [N] 6 MR Damper Characterization MR Damper Models F = F c Force-displacement relationship of M R damper 3 2tan 1 bx π 2 F = kx + cx + αz + F cx + F z = γz x z n 1 βx z n + Ax z = tanh βx + δsgn x F = σ zv + σ 1 z + σ 2 x z = x -2 σ a x z 1 + a 1 v Force-velocity relationship of M R damper 3.5A M easured.5a Predicted A M easured 1.75A Predicted F = δ 1 I + δ 2 tanh δ 3 x + δ 4 x + δ Displacement ; x n i F = b i + c i I x i= Velocity ; x' ; [m/s]

8 7 Baja Model Overview Spring-Damper Data Centre of Mass CAD Moments of Inertia Pneumatic Spring Characteristic Hydraulic Damper Characteristic Pacejka 89 Tyre Model ADAMS Model Baseline Testing Inputs Test Vehicle Preparation Baseline Testing RESULTS RESULTS Model Verified

9 Slalom Test Bump Test 8 Baja Vehicle Modeling and Model Validation Non-linear 2 Moving bodies 12 unconstrained DOF Contains experimentally determined properties Validated using bump and slalom tests

10 Displacement ; Z su4 Displacement ; Z su2 Displacement ; Z su3 Displacement ; Z su1 9 Bump Test Simulation Results (1) 3 Suspension deflection Front left damper displacement Front right damper displacement Rear left damper displacement Measured Simulation Rear right damper displacement

11 Pitch rate ; ' ; [ /s] Pitch rate ; ' ; [ /s] Roll rate ; ' ; [ /s] Roll rate ; ' ; [ /s] Yaw rate ; ' ; [ /s] Pitch rate ; ' ; [ /s] Ro Bump Test Simulation Results (2) 1 Pitch rate of sprung mass Sprung mass angular rates Roll rate of sprung mass Yaw rate of sprung mass 4 Roll rate of sprung mass Pitch rate of sprung mass 1-2 Pitch rate of sprung mass Measured Simulation -5 5 ; ' ; [ /s] Yaw rate of sprung mass 4 Yaw rate of sprung mass 2 4 [ /s] 2

12 Displacement ; Z su4 Displacement ; Z su2 Displacement ; Z su3 Displacement ; Z su1 11 Slalom Test Simulation Results (1) 4 Suspension deflection Front left damper displacement Front right damper displacement Measured Simulation2 Simulation Rear left damper displacement 4 Rear right damper displacement

13 12 Skyhook- and Groundhook Control Ideal Skyhook Ideal Groundhook Control Implementation Passive damping F SA = G aσ sky + 1 a σ gnd

14 Skyhook Control 13 Ride Comfort Simulation: Belgian Paving Passive damping: % Skyhook gain: 12 Ns/m

15 Acceleration ; Z s,cm '' ; [m/s 2 ] 14 Ride Comfort Results Weighted RMS vertical acceleration of sprung mass Weighted RMS acceleration of sprung mass Skyhook Control X: 1 Y: Z: 2.47 X:.75 Y: Z:.9533 Ride Comfort Optimal Passive X: Y: 12 Z:.8827 Ride Comfort Optimal Controlled 1.5 Passive Baseline Skyhook gain ; G ; [Ns/m] 4 1 Passive damping factor ; ; [-]

16 Current ; I 4 ; [A] ] Current ; I 3 ; [A] ] Force ; F MR4 ; [N] 15 Ride Comfort Results Prescribed damping forces and damper current Skyhook Control Front left prescribed current Front left M R damper force Front right prescribed current F SA F MR Rear left prescribed current Time -.2 ; t ; [s] Rear right prescribed current Velocity ; x' ; [m/s] 8 Rear left MR damper force

17 Skyhook Control Groundhook Control 16 Handling Simulation: Single Lane Change Passive damping: 5% Skyhook gain: 4 Ns/m Passive damping: 5% Groundhook gain: 4 Ns/m

18 Yaw Rate Angle ; ' ; ; [ /s] ; [ ] Lateral displacement ; Y cm Roll Rate Angle ; ' ; ; [ /s] ; [ ] Pitch Rate Angle ; ' ; ; [ /s] ; [ ] 15 5 Sprung Sprung mass mass pitch pitch angle rate Handling Results c -25 fac = 1% = 5% -5 Vehicle body roll 3 angle and 4 c yaw 5 rate 5.5 fac 6 = 2% 6.5 [s] = 5% ; G = 4 Sprung Sprung mass mass roll roll angle rate 15 = 5% ; G = 8 Groundhook Control c 1 fac = 2% ; G = 4 Location c 5 fac = 2% on grid ; G = = fac 1% 1% = fac 5% c 56 fa = 6 2% 6.5 c Sprung mass mass yaw yaw angle fac = 5% ; G = 4 rate = 5% ; G = 8 c 4 fac = 2% ; G = = 2% ; G = Longitudinal displacement ; X cm

19 Vertical force ; F t,z4 ; [N] Vertical force ; F t,z2 ; [N] Vertical force ; F t,z3 ; [N] Vertical force ; F t,z1 ; [N] Lateral displacement ; Y cm 18 Handling Results Road-tyre contact 4 Front left tyre vertical force 4 Front right tyre vertical force 6 Location on grid Groundhook Control = 1% = 5% = 2% = 5% ; G = 4 = 5% ; G = = 2% ; G = 4 = 2% ; G = 8 4 Rear left tyre vertical force 4 Rear right tyre vertical force Longitudinal displacement ; X cm

20 Yaw Rate ; ' ; [ /s] Yaw Angle ; ; [ ] Lateral displacement ; Y cm Roll Rate ; ' ; [ /s] Roll Angle ; ; [ ] Pitch Rate ; ' ; [ /s] Pitch Angle ; ; [ ] 5 15 Sprung mass pitch angle rate Handling Results c -25 fac = 1% = 5% -5 Vehicle body roll angle and yaw rate c fac 6 = 2% 6.5 = 5% ; G = 4 Sprung mass roll roll angle rate 15 = 5% ; G = 8 Skyhook Control c 1 fac = 2% ; G = 4 c 5 fac = 2% ; G = 8 Location on grid 6-15 c = -5 fac = 1% 1% 58 c = -1-3 fac = 5% 5% c fac c = fac = 2% 2% 6.5 c Sprung Sprung mass mass yaw yaw angle fac c = rate fac = 5% 5% ; G ; G = 4 = c = fac = 5% 5% ; G ; G = 8 = c = fac = 2% 2% ; G ; G = 4 = 4 c = fac = 2% ; G ; G = 8 = Longitudinal displacement ; X cm Time [s] 52

21 Vertical force ; F t,z4 ; [N] Vertical force ; F t,z2 ; [N] Vertical force ; F t,z3 ; [N] Vertical force ; F t,z1 ; [N] Lateral displacement ; Y cm 2 Handling Results Road-tyre contact 3 Front left tyre vertical force 3 Front right tyre vertical force 6 Location on grid Skyhook Control = 1% = 5% = 2% = 5% ; G = = 5% ; G = = 2% ; G = 4 = 2% ; G = Rear left tyre vertical force 3 25 Rear right tyre vertical 5 force Longitudinal displacement ; X cm

22 21 Suspension Control Results Summary Control Gain Passive Level Result Baseline Result Ride Comfort Skyhook 12Ns/m % Optimal Passive 7.5%.88m/s 2 RMS vertical acceleration..95m/s 2 RMS vertical acceleration. 58% 55% 2.1m/s 2 RMS vertical acceleration. Handling (Conventional off-road vehicles) Skyhook 8Ns/m 5% Up to 6% contact loss at 1 wheel. Body roll reduced. Up to 12% contact loss at 3 wheels. Handling (Test vehicle) Optimal Passive 2% Yaw rate of 88 /s obtained. 42% Yaw rate of 62 /s obtained.

23 22 Conclusion 12 DOF full vehicle model developed using ADAMS View software and validated Various MR damper models developed and superior model combined with vehicle model Ride comfort improved using skyhook control Directional response of test vehicle improved using low passive damping Body roll and road-tyre contact of conventional off-road vehicle improved using skyhook control and high passive damping

24 23 Recommendations & Future Work Recommendations Recursive MR damper modeling with force feedback Vehicle model improvement Suspension characteristics for other handling manoeuvres Future Work Combined ride comfort and handling Suspension control algorithms: focus on vehicles without differentials Hardware-in-the-Loop tests to measure MR damper force

25 Thank You