1. Design and Performance Analysis of a Roll Damping Function for an Electromechanical Active Roll Control System
Meindert Solkesz, Department of Precision and Microsystems Engineering
Welcome, i’m very happy that you all could come to my presentation about my graduation project. My name is Meindert Solkesz, and today I will present a part of the work I did the past year.
The title of my graduation project is ‘Design and Performance analysis of a roll damping function for an electromechanical active roll control system.
First I will give some background information in which I explain what an eARC system actually is.
Then I will continue with the objective of this thesis, and after that i will dive into the design part of the roll damping function. Followed by some results of the tests I carried out.
But first, i introduce you the ford motor company in Cologne. After all this is where I spend most of my time.

2. The Ford Motor Company a brief introduction Ford Werke - Merkenich
m2 of design centres, test tracks, equipment
Global Advanced Vehicle Dynamics
Active suspensions
Active safety
I worked at GAVD where i worked on my graduation project
Also projects concerning active safety such as Stability control/ traffic sign recognition / lane keeping assistance
After i introduced the company, i would like to introduce the test vehicle that was available

3. SUV demonstrator vehicle
Range Rover Sport -specs
4.2L supercharged V8 (390Hp)
Hydraulic Active Roll Control system
Airsprings front & rear
2700 kg
Here she is
A normal passenger car weighs about 1500kg...

4. Terminology Degrees of Freedom Translational directions
This vehicle has six degrees of freedom... Roll most important, traditionally roll is reduced by a stabiliser bar
Translational directions
x-direction: longitudinal
y-direction: lateral
z-direction: heave
Rotational directions
θx: roll
θy: pitch
θz: yaw

5. Terminology suspension linkages dampers springs stabiliser bar
Here you see a front suspension of a conventional vehicle
Connection between wheels and body
Therefore responsible for the coupling between road inputs and body
Stabiliser bar in conventional vehicle reduces roll in conventional vehicle and it works like this

6. Stabiliser bar even input uneven input
However how large this angle will be give a certain cornering speed is dependent on the stiffness of the stabiliser bar. This effect of the stiffness on the driving behaviour of the vehicle is explained next

7. Stabiliser bar Weak vs. stiff weak stiff Cornering (handling)
Compromis between handling and comfort
The best would be to change the characteristics of the stabiliser bar according to the driving situation.
Straight driving
(comfort)

8. Active Roll Control (ARC)
Suspension layout
Actuator it is possible to manipulate the roll angle
Compromise improved
Hydraulic actuator mounted orginally in the vehicle as mentioned at the beginning of this presentation, however there are some advantages and disadventages:

9. Active Roll Control Hydraulic vs. Electromechanical system Hydraulic
pros
Lots of power
Relatively simple
Knowledge available
cons
Continuously running oil pump
Slow
Electromechanical
pros
Energy efficient
Fast
cons
Complex
Proven technology
Slow: therefore good in slow manoeuvres such as cornering, not good to filter out bumps in road for good comfort
Trent of electrification in the automotive industry, and demands for less fuel consumption
Expectation is that electromechanical is better, therefore implemented in demonstrator vehicle

10. SUV demonstrator vehicle
Range Rover Sport –modifications for eARC
Electromechanical actuators at front & rear
Sensors
Programmable control hardware
Data acquisition hardware
LCD-screen
It turned out software was not compatible with eARC because of lack of damping

11. Software modification
motivation
Lack of damping in the implemented actuators
Demand for a roll damping function in the existing control
software
Potential of energy regeneration
This is where my graduation project started

12. Objective
“Design a roll damping function for an electromechanical active roll control system (eARC) and analyse its performance”
Steps taken:
Modify veDYNA computer model
Validate computer model with SUV demonstrator vehicle
Modify the eARC controller with a roll damping function
Analyse the open-loop for stability
Analyse the closed-loop performance
Implement the controller in the real vehicle
Performance test of the roll damping function with regard to power consumption, comfort and handling

13. Validation
Kinematics & Compliance test rig
Quasi static measurements

14. Validation Parameters that qualified for validation: Tyre stiffness
Vehicle body mass, COG, inertia and roll centre
Vertical stiffness suspension
Roll stiffness
A lot those parameters not only relevant for computer model, but also for the eARC controller
That’s all about the validation and computer model
I will now continue with the development of the roll damping function

15. Roll damping function Control loop
Turned out that the system became unstable, unexpected when increasing damping
Analysed response of vehicle body as a function of the roll rate road input

16. Simulations Performance low level controller no stabiliser bar
demanded tq = 0

17. Roll damping function
Control loop

18. Roll damping function
Open-loop

19. Open-loop frequency response
Bode plot
Difficult to analyse stability with gain and phase margin

20. Open-loop frequency response
Nyquist plot
Magnitude
Phase
Therefore nyquist

21. Nyquist stability criterion
Most common phase & gain margin, easier however the vector margin which combines both stability creteria

22. Open-loop frequency response
Nyquist stability criterion

23. Phase lead filter

24. Notch filter

25. Modified roll damping function

26. Open loop with filter Optimal stability
Now that the stability is ok, let’s have a look what the closed-loop performance with regard to noise rejection looks like

27. Performance
4 poster rig measurements

28. Closed loop response Optimal stability demanded tq = 0
activated roll damping

29. Closed loop response Optimal performance demanded tq = 0
activated roll damping
Amplification for higher frequencies less relevant, because human body is tolerates it better

30. Stability optimal performance
Nyquist stability criterion
Stability ok, now let’s investigate the performance in real life with regard to power consumption, comfort and handling as mentioned at beginning

31. Closed loop response Optimal performance 1.8 passive
activated roll damping
1.8

32. 1.8 Hz
Passive stabiliser bars
Active with roll damping

33. Power consumption 4 poster test Roll damping function activated
No net energy regeneration
Not as expected

34. Power consumption
4 poster test

35. Comfort

36. Handling Slalom manoeuvre Without rolldamping With rolldamping
Now the results of the tests lead to the following conclusions

37. Summary Computer model modified and validated
Stability analysis performed
Stability improved with the use of notch and phase lead filters
Functioning of the roll damping function judged with regard to power consumption, comfort and handling

38. Conclusions
Stability of the roll damping feedback loop is improved with a combination of a notch and lead filter.
Filters tuned for optimal stability do not provide optimal performance
The roll damping does not regenerate energy.
The roll damping function has a positive / a negative / no influence on the comfort.
The roll damping function improves the handling.

39. questions

40. Validation
Vertical stiffness – vertical position

41. Validation Vertical stiffness - avarage Rebound stop Rebound spring
Air bellow
Spring aid

42. Validation
Vertical stiffness – 31 sec bounce cycle

43. Validation
Vertical stiffness sec bounce cycle

44. Validation
Roll stiffness

45. Validation
Roll stiffness

46. Active Suspension principles Fully active Semi active energy added
no energy added
Example:
damper with adjustable damping coefficients
Fully active
energy added
Example: electromechanic/hydraulic actuators at 4 corners

47. Vehicle model
veDYNA

48. Controller
high-level

49. Controller
low-level

50. Roll damping function
Frequency response

51. Damping ratio
Paragraaf subkop

52. Paragraafkop
Paragraaf subkop

53. Rollrate signal method Vertical acceleration sensors
Lateral acceleration sensors
Rollrate sensor

54. Rollrate signal estimation
Vertical acceleration sensors

55. Roll damping function
Control loop

56. Open loop measurement
Paragraaf subkop

57. Power consumption Simulation -double –step-steer manoeuvre
Average power consumption: 184 Watt
68 % decrease of powerconsumption

58. Power consumption Simulation -Bumpy road
Average power consumption: 31 Watt
50 % increase of powerconsumption

59. Validation
Kinematics & Compliance test rig

60. Closed loop response
Optimal performance
passive
filtered 6

61. 6Hz
Paragraaf subkop
Passive stabiliser bars
Active with roll damping

62. Closed loop response
Optimal performance
passive
filtered
7.6

63. 7.6Hz Paragraaf subkop Passive stabiliser bars
Active with roll damping

64. Open loop filtered
Bode plot