Fabio Vacca

Dr Fabio Vacca

My publications


Vacca F, Pinto De S, Hartavi Karci A, Gruber P, Viotto F, Cavallino C, Rossi J, Sorniotti A (2017) On the Energy Efficiency of Dual Clutch
Transmissions and Automated Manual Transmissions,
Energies 10 (10) 1562 pp. 1-22 MDPI
The main benefits of dual clutch transmissions (DCTs) are: (i) a higher energy efficiency
than automatic transmission systems with torque converters; and (ii) the capability to fill the torque
gap during gear shifts to allow seamless longitudinal acceleration profiles. Therefore, DCTs are viable
alternatives to automated manual transmissions (AMTs). For vehicles equipped with engines that
can generate considerable torque, large clutch-slip energy losses occur during power-on gear shifts
and, as a result, DCTs need wet clutches for effective heat dissipation. This requirement substantially
reduces DCT efficiency because of the churning and ancillary power dissipations associated with
the wet clutch pack. To the knowledge of the authors, this study is the first to analyse the detailed
power loss contributions of a DCT with wet clutches, and their relative significance along a set of
driving cycles. Based on these results, a novel hybridised AMT (HAMT) with a single dry clutch
and an electric motor is proposed for the same vehicle. The HAMT architecture combines the high
mechanical efficiency typical of AMTs with a single dry clutch, with the torque-fill capability and
operational flexibility allowed by the electric motor. The measured efficiency maps of a case study
DCT and HAMT are compared. This is then complemented by the analysis of the respective fuel
consumption along the driving cycles, which is simulated with an experimentally validated vehicle
model. In its internal combustion engine mode, the HAMT reduces fuel consumption by >9% with
respect to the DCT.
Vacca F, Capilli G, Sorniotti A, Fracchia M, Remondin T, Cavallino C, Bottiglione F (2018) A Novel Hybridized Automated Manual
Transmission for High Performance Cars,
Proceedings of AMC 2018 IEEE
Because of the introduction of progressively more
restrictive regulations that aim to reduce fuel consumption and
CO2 emissions, the automotive industry is focusing its efforts on
environmentally friendly passenger cars. In particular, different
electrification roadmaps are pursued by the individual car
makers, and electrified drivetrain layouts are progressively
introduced into the market. This process involves all vehicle
segments, including high performance passenger cars. In this
context, this study presents a novel hybridized automated manual
transmission (HAMT) for cars with high power characteristics.
The HAMT includes six gear ratios associated with the internal
combustion engine, and two gear ratios associated with an
electric motor. The energy efficiency of the HAMT is measured
on a drivetrain test rig, and compared with that of an equivalent
dual clutch transmission (DCT). Simulation results based on the
experimentally measured efficiency maps show the significant
energy consumption reduction of the HAMT in its internal
combustion engine mode, with respect to the DCT.

The research of this thesis focuses on the hardware-in-the-loop (HIL) assessment of proof-of-concept automotive systems. Two main applications are investigated: i) hybridised drivetrains; and ii) novel wheel slip controllers for anti-lock braking systems (ABS) applications.

The activities related to the assessment of proof-of-concept transmissions involve preliminary simulations and experimental evaluation of novel transmission prototypes for high performance passenger cars. A model-based approach is used to analyse the main power loss contributions of a baseline case study transmission. The newly developed hybridised transmission offers comparable performance (i.e. smooth acceleration profile during gearshift events), addressing comfort requirements. The experimental activity showed the efficiency improvements due to the mechanical layout of the new hybridised transmission. The benefits deriving by the hybridisation are also assessed through simulations carried out considering alternative proof-of-concept transmission layouts and an on-line implementable energy management strategy (A-ECMS). Other examples of hybridization layouts are also reported, i.e., the very recently developed hybrid rear axle module (HRAM). Furthermore, because of its ?modular? nature, the device can be equipped with advanced mechanical systems which allow a left-to-right torque distribution.

The wheel slip controller assessment on a HIL test rig setup involves an electro-hydraulic braking (EHB) unit. Because of their decoupled nature, EHBs offer independent and continuous modulation of the pressure levels at the four corners of the vehicle. For this test case, the HIL methodology is employed to quantify the performance benefits deriving from a PID-based wheel slip controller and a more advanced control strategy such as an explicit non-linear model predictive controller (eNMPC). The eNMPC performs better with respect the PID-based wheel slip controller on different test case scenarios. The results obtained during the development process have proven the effectiveness of the presented devices.