E-Semitrailer longitudinal wheel torque control within safe operation

E-Semitrailer longitudinal wheel torque control within safe operating envelope

The move towards electrifying heavy commercial vehicle transport offers exciting opportunities. It allows us to explore innovative vehicle configurations, where both trucks and trailers can have electrified axles. Effective wheel torques distribution between units is essential to ensure both top performance and safety, while also enhancing productivity.

The addition of drivetrain on semitrailers increases the number of overall actuators required to control vehicle combination motion. This allows several possible torque distribution strategies to achieve desired longitudinal, lateral, yaw and roll motion on each unit. Control allocation can be used to solve such over actuated systems [1,2]. The objective of the thesis is to develop a control allocation strategy that efficiently allocates propulsion and brake requests between the tractor and the electrified semitrailer (e-trailer) to ensure that the vehicle combination operates within its safe operating envelop. The safe operating envelope can be defined as the condition where the vehicle remains stable, ensuring that any combination of forces will not lead to jackknifing, trailer sway, or rollovers [3]. The vehicle combination that will be used in this thesis is 4x2 tractor with semitrailer (refer figure 1).

Figure 1. 4x2 tractor and semitrailer

The strategy needs to be developed for two different types of e-trailers. In type (A) e-trailer, there will be limited communication between the tractor and the trailer. Consequently, both the units are responsible for its own control allocation and torque distribution such that entire vehicle combination is stable. The limited information that can be available for the controller can be brake torque request, coupling force sensor data, etc. But no other information such as tractor’s velocities and accelerations should be considered for trailer’ control logic and vice-versa.

In contrast, type (B) e-trailer will have full communication with the tractor and thus, the control logic can be implemented on tractor only to control both units. Here, the inputs to tractor can be all the states of trailer and tractor, but there will be no coupling force sensor. The control logic should also consider signal latency and delays arising from the electrical architecture within the vehicle combination.

The objectives of this master thesis are as follows:

  • Investigate existing research on the safe operating envelope of a tractor and e-trailer combination, proposing controllers for type (A) and type (B) e-trailers.
  • Develop control allocation algorithm to distribute torque on both units to ensure overall safety of the vehicle combination.
  • Test the algorithm for various scenarios, including different speeds and curve conditions both laden and unladen, and varying friction coefficient.
  • Integrate additional logic to handle latency and delays in communication.


[1]. Uhlén, K., Nyman, P., Eklöv, J., Laine, L., Sadeghi Kati, M. and Fredriksson, J., “Coordination of Actuators for an A-double Heavy Vehicle Combination”, 17th International IEEE Conference on Intelligent Transportation Systems, 2015.
[2]. Hjelte Ulmehag R., “Energy management for a tractor and semitrailer combination using control allocation”, Master thesis, Chalmers, 2016.
[3] Axel Hansson, Erik Andersson, Leo Laine, Maliheh Sadeghi Kati, Umur Erdinc and Mats Jonasson, Control envelope for limiting actuation of electric trailer in tractor-semitrailer combination, to be presented in ITSC 2022 Conference, October 8-12, in Macau, China,2022.

Suitable background

The thesis work will include vehicle dynamics, control theory and signal processing. The work will be carried out at Volvo Group Trucks Technology. The thesis is recommended for two students with vehicle dynamics and control knowledge and good mathematical skills

Thesis Level: Master

Language: English

Starting date: Jan 2024

Number of students: 2

Christian Oscarsson


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