On the Control of Engine Start/Stop Dynamics in a Hybrid Electric Vehicle

Abstract

The starter/alternator technology is considered an easily realizable hybrid electric vehicle (HEV) configuration to achieve significant fuel economy without compromising consumer acceptability. Several examples can be found in production or near-production vehicles, with implementation based on a spark ignition (SI) engine coupled with either a belted starter/alternator (BSA) or an integrated starter/alternator (ISA). One of the many challenges in successfully developing a starter/alternator HEV is to achieve engine start and stop operations with minimum passenger discomfort. This requires control of the electric motor to start and stop the engine quickly and smoothly, without compromising the vehicle noise, vibration, and harshness signature. The issue becomes more critical in the case of diesel hybrids, as the peak compression torque is much larger than in SI engines. This paper documents the results of a research activity focused on the control of the start and stop dynamics of a HEV with a belted starter/alternator. The work was conducted on a production 1.9 l common-rail diesel engine coupled to a 10.6 kW permanent magnet motor. The system is part of a series/parallel HEV powertrain, designed to fit a midsize prototype sport utility vehicle. A preliminary experimental investigation was done to assess the feasibility of the concept and to partially characterize the system. This facilitated the design of a control-oriented nonlinear model of the system dynamics and its validation on the complete HEV hardware. Model-based control techniques were then applied to design a controller for the belted starter/alternator, ensuring quick and smooth engine start operations. The final control design has been implemented on the vehicle. The research outcomes demonstrated that the BSA is effective in starting the diesel engine quickly and with very limited vibration and noise.

Powertrain Control for Hybrid-Electric and Electric Vehicles

“…Some examples are the following: an X-EV could operate in pure EV mode or in hybrid mode (whether series, parallel, or power-split), could use special control algorithms during regenerative braking events to provide maximum energy recovery without adversely affecting brake and vehicle stability control systems, and could implement special startstop control strategies that minimize fuel consumption at idle without adversely affecting engine cold-or warm-start emissions and without inducing unwanted transient vibrations (Canova et al 2009). Figure 3 depicts an example of a state flow diagram that could be implemented in a finite state machine.…”

Design of a hydraulic servo-actuation fed by a regenerative braking system

“…This estimated fuel saving should be further refined also considering the impact of engine restarts which typically causes slight increase of fuel consumptions as studied by many works in literature, as example of Canova [37,38]. In this preliminary phase of the design this aspect has been neglected but it should be better investigated when it will be possible to perform further experimental activities on a fleet of prototypes.…”

Coordinated Engine-Start Control of Single-Motor P2 Hybrid Electric Vehicles with Respect to Different Driving Situations

“…Like conventional powertrain system, some HEVs use an additional starter which can be individually controlled to start the engine. Canova et al [10] adopted a 10.6 kW belted starter/alternator (BSA) to start the diesel engine of a series/parallel HEV, and designed closed-loop control for engine start-stop. Wang et al [11] developed HEVs start and acceleration strategies based on the integrated starter/generator (ISG), and came up with the concept of ISG "fast" and "slow" torque to overcome the conventional engine transient fuel.…”