MSc Thesis proposal in Vehicle Dynamics: Configurable and Modular Axles for Heavy Vehicles Version, modified 2018-12-22 09:20 Background Heavy truck manufacturers have very many variants to develop. One way to handle this is to develop modular axles. Mechanical modularization, see Figure 1, is already a fact, but with increasing software-function content in the vehicles, it is also relevant to modularize the software connected to the axles, see Figure 2. It mainly refers to functional architecture of motion request flow and information flow (estimates, capabilities, etc). Automated driving, active safety, electric propulsion and longer combination vehicles drives the development. Also, other actuators, such as brake systems go through a development, see [1]. Figure 1: Mechanical design of axles for heavy truck (Volvo GTT). Vehicle Motion Management Figure 2: An overview of function architecture. The thesis will analyse cons and pros for establishing axle modules within the Vehicle Motion Management. From [3]. A typical application where advanced control is useful is construction trucks, which often operate on uneven road. Solutions and inspiration can be found in the NASA projects like the NASA Mars Exploration Rover vehicle, see Ref [2] and Figure 3.
Transcript
MSc Thesis proposal in Vehicle Dynamics:
Configurable and Modular Axles for Heavy Vehicles Version, modified 2018-12-22 09:20
Background
Heavy truck manufacturers have very many variants to develop. One way to handle this is to
develop modular axles. Mechanical modularization, see Figure 1, is already a fact, but with
increasing software-function content in the vehicles, it is also relevant to modularize the
software connected to the axles, see Figure 2. It mainly refers to functional architecture of
motion request flow and information flow (estimates, capabilities, etc). Automated driving,
active safety, electric propulsion and longer combination vehicles drives the development.
Also, other actuators, such as brake systems go through a development, see [1].
Figure 1: Mechanical design of axles for heavy truck (Volvo GTT).
Vehicle Motion Management
Figure 2: An overview of function architecture. The thesis will analyse cons and pros for establishing axle
modules within the Vehicle Motion Management. From [3].
A typical application where advanced control is useful is construction trucks, which often
operate on uneven road. Solutions and inspiration can be found in the NASA projects like the
NASA Mars Exploration Rover vehicle, see Ref [2] and Figure 3.
Figure 3: NASA’s Mars Exploration Rover with rocker-bogie suspension.
Problem/opportunity motivating the project
Number of axle variants are increasing, especially driven by higher degree of actuation. This
number has to be minimized and still offer possibility for adjustments for special application.
Envisioned solution
A generic signal interface (requests, capabilities, status/actual/estimates values) between
Vehicle Motion Control and Axle Management would enable quick and efficient integration
of axles both mechanically and software-wise.
Objectives/Research Questions
• Optimization of one use case
• A proposal of interfaces of an axle SW module
Deliverables
• Optimal control trajectories and measures of energy and transport efficiency for
reference axle and studied axle for the use case.
• Simulation model used in optimization, including signal interface on axle SW-
modules.
Limitations
• Only rigid truck (no towed units)
• Only one Axle to optimize (see below)
• Trajectory Optimization (no control design)
Sketch of activities
• Literature study/Information search
• Define a use case: Compare One certain vehicle (rigid, construction), where the
tandem axle is subject for optimization:
o Reference tandem axle: Rigid axles, All 4 wheels differential driven. Differential
lock only when/if stuck.
o Axle to optimize:
▪ Mechanical installation: Individual rear suspension, No steering
▪ Wheel-individual torque actuation (4xT(t))
▪ Suspension actuation (TBD whether passive or 4 × 𝑑 (𝑑 is damping
coefficient) or 3 × 𝛥𝐹𝑧(𝑡)) o One certain task: Uneven ground profile, gravel/sand, some hundred meter long
o Cost functions: Energy consumption (J/(kg*m)), Transport efficiency (kg*m/s)
o Constraints: Shaft loads, comfort, Actuator level and rate, Road friction, …
• Model the Reference/Baseline tandem axle. Approximate results from a high-fidelity
model from Volvo GTT (VTM) will be available as inspiration.
• Model the Axle to optimize
• Find energy and transport time for the Reference/Baseline tandem axle.
• Trajectory optimization for the Axle to optimize, i.e. find optimal actuation requests as
[2] Harrington, Brian D.; Voorhees, Chris, The challenges of designing the rocker-bogie suspension for the Mars Exploration Rover, https://trs.jpl.nasa.gov/handle/2014/38435, 2004
[3] Tagesson, Kristoffer K D, Driver-centred Motion Control of Heavy Trucks, Doctoral thesis, https://research.chalmers.se/en/publication/?id=249103, 2017
