System and method for operating a hybrid aircraft power plant
Hybrid aircraft power plants are provided together with associated systems and methods for operating such hybrid aircraft power plants. A hybrid aircraft power plant includes a thermal engine, an electric motor and one or more controllers operatively connected to the thermal engine and to the electric motor. The thermal engine and the electric motor are drivingly connected to an air mover of an aircraft via a combining gear train. The one or more controllers are configured to govern an actual output torque of the electric motor to reduce an error between a target operating speed for the air mover and an actual operating speed of the air mover, and govern an output of the thermal engine to reduce an error between a target output torque for the electric motor and the actual output torque of the electric motor.
1. A method of operating a parallel hybrid aircraft power plant including an electric motor and a thermal engine cooperatively driving a shaft, the method comprising:
when a first load magnitude is applied to the shaft:
using the parallel hybrid aircraft power plant to drive the shaft; and
controlling the parallel hybrid aircraft power plant to achieve a target rotational speed for the shaft with the first load magnitude being applied to the shaft;
before applying a second load magnitude to the shaft receiving an anticipatory signal indicative of a second load magnitude; and
adjusting an output of the thermal engine in advance of the second load magnitude being applied to the shaft based on the second load magnitude of the anticipatory signal;
applying the second load magnitude to the shaft, the second load magnitude being different from the first load magnitude;
controlling an actual output of the electric motor to achieve the target rotational speed for the shaft with the second load magnitude being applied to the shaft; and when the electric motor is being controlled to achieve the target rotational speed for the shaft with the second load magnitude being applied to the shaft,
controlling the thermal engine to permit the electric motor to achieve a target output of the electric motor based on an error between the target output of the electric motor and the actual output of the electric motor.
2. The method as defined in claim 1 , wherein the target output of the electric motor is ≤20% of a maximum continuous torque rating of the electric motor.
3. The method as defined in claim 1 , wherein the target output of the electric motor is nil.
4. The method as defined in claim 1 , comprising:
using electric energy from a battery to drive the electric motor; and
determining the target output of the electric motor as a function of a state of charge of the battery.
5. The method as defined in claim 4 , comprising, when the state of charge of the battery is within a desired range, the target output of the electric motor is ≤2% of a maximum continuous torque rating of the electric motor.
6. The method as defined in claim 4 , comprising, when the state of charge of the battery is lower than a desired range or a desired value, the target output of the electric motor is negative to cause operation of the electric motor as a generator to charge the battery.
7. The method as defined in claim 4 , comprising, when the state of charge of the battery is higher than a desired range or a desired value, the target output of the electric motor is positive to cause operation of the electric motor as a motor to drive the shaft.
8. The method as defined in claim 1 , wherein, when the second load magnitude applied to the shaft is smaller than the first load magnitude applied to the shaft, the actual output of the electric motor is negative to cause operation of the electric motor as a generator to hinder an overspeed condition of the shaft.
9. The method as defined in claim 1 , wherein, when the second load magnitude applied to the shaft is greater than the first load magnitude applied to the shaft, the actual output of the electric motor is positive to cause operation of the electric motor as a motor to drive the shaft.
10. The method as defined in claim 1 , wherein:
the shaft is drivingly connected to a main rotor of a helicopter; and
applying the second load magnitude to the shaft includes changing a collective pitch of the main rotor and/or changing an attitude of the helicopter.
11. The method as defined in claim 1 , wherein controlling the actual output of the electric motor to achieve the target rotational speed for the shaft is based:
on an error between the target rotational speed for the shaft and an actual rotational speed of the shaft; and/or
on an error between a target operating speed for the electric motor and an actual operating speed of the electric motor.