Method and system for controlling a hybrid motor vehicle during decelerations
A method for controlling a hybrid motor vehicle includes a disengageable combustion engine, involving the following steps: the power absorbed by the main electric machine to meet the target torque required at the wheels is determined, the electrical power to be expended by the second electric machine to meet the target torque required at the wheels is determined by subtracting the power absorbed by the main electric machine from the charging capacity of the traction battery, a gross value is determined for the minimum speed of rotation of the combustion engine, as a function of the electrical power to be expended by the second electric machine, and a setpoint for the minimum speed of rotation of the combustion engine is determined from the minimum speed of rotation of the combustion engine as a function of positive and negative gradients.
1 . A method for controlling a motor vehicle comprising a combustion engine, a first electric machine and a second electric machine, the combustion engine being connected to the wheels by a disengageable connection and to the second electric machine by a connection that can also be disengaged, the electric machines being electrically connected to a battery, the control method comprising the following steps:
the driver's torque requirement is determined,
the power absorbed by the main electric machine to meet the target torque required at the wheels is determined,
the electrical power to be expended by the second electric machine to meet the target torque required at the wheels is determined by subtracting the power absorbed by the main electric machine from the charging capacity of the traction battery,
the equivalent mechanical power to be produced by the second electric machine is determined as a function of the electrical power to be expended by the second electric machine and the average electrical efficiency value from mechanical power,
a gross value is determined for the minimum rotation speed of the combustion engine, modelled by a linear model of the power losses of the combustion engine as a function of the equivalent mechanical power to be produced by the second electric machine, and
a setpoint for the minimum speed of rotation of the combustion engine is determined from the minimum speed of rotation of the combustion engine as a function of positive and negative gradients.
2 . The control method according to claim 1 , in which the gross value of the minimum rotation speed of the combustion engine is limited to a maximum authorized rotation speed of the combustion engine for decelerations to take account of vibration constraints.
3 . The control method according to claim 1 , in which, in order to determine the gross setpoint for the minimum rotation speed of the combustion engine, the following sub-steps are carried out:
a minimum rotation speed differential of the combustion engine is determined as being equal to the difference between the minimum rotation speed of the combustion engine and the gross minimum rotation speed setpoint of the combustion engine,
a Boolean status value is determined as a function of a comparison between the minimum rotation speed of the combustion engine and a rotation speed threshold for a minimum duration,
a positive gradient is determined as a function of a first predetermined table receiving as input the minimum rotation speed differential of the combustion engine and as a function of said Boolean state value,
a negative gradient is determined as a function of a second predetermined table receiving as input the minimum rotation speed differential of the combustion engine and as a function of said Boolean state value, and
the gross setpoint for the minimum rotation speed of the combustion engine is then determined as a function of the positive gradient, the negative gradient and the minimum rotation speed of the combustion engine.
4 . The control method according to claim 3 , in which the minimum rotation speed setpoint of the combustion engine is determined as the minimum value between the gross minimum rotation speed setpoint of the combustion engine and the maximum permissible rotation speed of the combustion engine for decelerations.
5 . A control system for a motor vehicle comprising a combustion engine, a first electric machine and a second electric machine, the combustion engine being connected to the wheels by a disengageable connection and to the second electric machine by a connection that can also be disengaged, the electric machines being electrically connected to a battery, the control system being wherein it comprises a sensor for measuring the target torque required at the wheels, a sensor for measuring the charge capacity of the traction battery, computing means and memories configured to execute the control method according to claim 1 .