MSc Thesis proposal The Impact of Active Forces on Vehicle ... · 11/15/2018  · MSc Thesis proposal in Vehicle Dynamics: The Impact of Active Forces on Vehicle Suspension Kinematics

Page 1

MSc Thesis proposal in Vehicle Dynamics:

The Impact of Active Forces on Vehicle Suspension Kinematics

Version, modified: 2018-11-15 15:13

Background

Design of vehicle suspension kinematics (or linkage geometry) is a way to optimize the

vehicle behaviour upon steering, braking, accelerating, etc. It includes the tuning of hard

points (joint positions for the link members) for the optimization of:

• Steering geometry.

• Anti-roll geometry.

• Geometry to combat squat and dive during acceleration and braking.

For passive suspensions, the kinematic analyses and trade-offs are well known (e.g. [2, 3]).

Currently, chassis technology is evolving towards active suspensions, in which electro-

mechanic actuators can provide forces to each wheel individually. See also picture on page 4.

This allows to overcome the traditional conflict between comfort and handling, but it also needs

to be balanced with the expense of increased cost and complexity.

For active suspensions, the kinematic analyses and trade-offs are different. This involves both

design of the passive parts, such as hard points, and the active parts, such as actuator sizing

and control algorithms.

Active suspensions can be classified according to their bandwidth:

• “Load-levelling suspensions” has an actuation bandwidth well below the main

suspension dynamics, i.e. well below 1 Hz.

• Slow-active suspensions has a bandwidth in between body and wheel dynamics.

• Fully-active suspensions with bandwidth above wheel dynamics, i.e. typically above 5

Hz, see reference [4].

Page 2

Problem motivating the project

The kinematic analyses and trade-offs for active suspensions are not well enough known.

Without this knowledge, it is very likely that today’s active suspension designs are far from

optimal, regarding vehicle performance, product cost and variant handling within vehicle

programmes.

Envisioned solution

The following design tools is predicted to contribute with new knowledge which will reduce

the defined problem.

• A generalization of the two-dimensional graphical and mathematical tools through

addition of arbitrary active forces at the wheels. An example of such graphical tool for

dive upon braking for passive suspension is given in Figure 1 and Reference [5].

Figure 1: Example of graphical kinematic diagram [2].

• A study of the interaction of the suspension geometry and the presence of forces 𝐹(𝑡) for some cases. How do given geometries affect control strategies for 𝐹(𝑡)? How do -

𝐹(𝑡) profiles modify the optimal geometry?

Objectives / Research Questions

The objective of the project is to understand the impact of active suspension forces on

suspension kinematics:

• Which are the important active suspensions design support tools to include complete

vehicle motion aspects?

• How can these tools look like?

• How can the suspension geometry be simplified (or performance be improved) by

means of active suspension?

Deliverables

• Tools and design guide-lines for active suspension

• Master thesis report in English

• Ideally, the project should lead to a submitted scientific paper

Limitations (to be further developed during planning report)

• At first, only instantaneous active forces need to be considered.

• The vehicle model will be as simple as possible. For example, [1] claims that a 6 degrees

of freedom model is sufficient to study anti-squat effects.

Page 3

Sketch of activities

• Literature study / Information search

• Start-up analysis model and manoeuvres:

o Select relevant manoeuvres for assessment and development, e.g. squat and

dive optimization under braking and accelerating straight-line manoeuvres,

steady-state cornering, step steering, going over bump, etc..

o One realistic suspension geometry to be selected.

o First implement fully-active suspensions, capable of inserting energy in the

four force-velocity-quadrants, instantly and independently at each wheel, and

without actuation saturations and time delays. Then, implement actuated force

saturated at 6 kN per wheel and a bandwidth up to 5 Hz.

• Study the case in terms of:

o Generalization to the presence of active forces. Precise formulation of solvable

problems. Communication with experts from different fields (vehicle

dynamics, control, etc) for refinement and potential formulation of more

advanced dynamical problems.

o Graphical, analytical or numerical solutions of the solvable problems. I.e.

(develop) and apply tools.

o Conclusions from initial case

• Presentation, 1st version/draft of report

• Development phase:

o Develop simplification of geometry as a result of the active suspension.

o Assess possible improved vehicle dynamics performance as a result of the

active suspension.

• Presentation, 2nd version/draft of report

• Exploratory analyses and sensitivity studies with software such as IPG CarMaker.

Tenneco can provide detailed active suspension models.

• Conclusion: Lessons learnt, developed tools and design guide-lines for active control

design.

• Final version of report and final presentation, possibly also at Tenneco in Belgium.

• (Potential scientific paper)

Interest for the student

The student will:

• improve his/her modelling, analysis, and problem-solving skills.

• acquire engineering knowledge that can be applied in a wide range of industries, beyond

the automotive.

• will be involved in a real, open-ended industrial research problem.

• become versed in vehicle dynamics and chassis mechanics.

• get experience with the software package IPG CarMaker.

• write a scientific paper, therefore strengthening a possible PhD application.

Pre-knowledge

• Required: BSc/MSc programme in Mechanical or Automotive engineering

• Required: Course(s) in Vehicle Dynamics

• Desired: Course(s) in Control engineering

Page 4

Administrative

• Number of credits: 30 points per student (nominally 20 weeks)

• Number of students: 1 or 2 students

• Starting date: A.s.a.p., for instance January 2019

• Stakeholder: Tenneco

• Subject/research group at Chalmers: Vehicle Dynamics group

o Examiner: Bengt Jacobson, [email protected], 0046-703821383

o Academic Supervisor: Ingemar Johansson, [email protected], 0046-

721843726

o Industrial supervisor: Joan Vazquez Molina, Tenneco Automotive bvba, Belgium

• Application to: Ingemar Johansson, [email protected], 0046-721843726 with CV and

transcripts

• Physical location: At Chalmers VEAS office with regular conference calls with Tenneco

References:

[1] Azman, M., Rahnejat, H. & King, P. D., Influence of anti-dive and anti-squat geometry in combined vehicle bounce and pitch dynamics, Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics, Vol. 218, 2004.

[2] Barton, D. C. & Fieldhouse, J. D, Automotive Chassis Engineering, Springer, 2018.

[3] Genta, G. & Morello, L., The Automotive Chassis (Vol 1: Components Design & Vol 2: System Design), Springer, 2009.

[4] Savaresi, S. M. et al, Semi-Active Suspension Control for Vehicles, Elsevier, 2010.

[5] Jacobson et al, Vehicle Dynamics Compendium, 3.4.6-3.49, 4.3.9.3, Chalmers University of Technology, https://research.chalmers.se/publication/505928, 2018