Degraded mode operation of hybrid electric propulsion systems
A hybrid electric engine control module (ECU) can be configured to be operatively connected to a hybrid electric aircraft powerplant having a heat engine system and an electric motor system to control a torque output from each of the heat engine system and the electric motor system. The ECU can be configured to determine whether at least one of the electric motor system or the heat engine system are in a normal mode such that one of the electric motor system and/or the heat engine can provide a predetermined amount of torque. The ECU can be configured to switch to a degraded mode if either of the electric motor system or the heat engine system cannot provide the predetermined amount of torque. In the degraded mode the ECU can be configured to control the electric motor system and the heat engine system differently than in the normal mode or to not control one or both of the electric motor system or the heat engine system.
1. A hybrid electric engine control system configured to be operatively connected to a hybrid electric aircraft powerplant having a heat engine system and an electric motor system to control a torque output from each of the heat engine system and the electric motor system, the heat engine system including a hybrid electric engine control module for controlling the heat engine system, the electric motor system including a motor control module for controlling an electric motor of the electric motor system, the hybrid electric engine control system being configured to:
determine that the electric motor system and the heat engine system are in a normal mode such that the electric motor system and the heat engine system can provide respective first and second predetermined amounts of torque;
when the electric motor system and the heat engine system are in the normal mode, receive a raw power lever angle (PLA) indicative of a torque command from a power lever and split output power between the electric motor system and the heat engine system as a function of the torque command;
switch to a degraded mode when the electric motor system cannot provide the first predetermined amount of torque;
switch to the degraded mode when the heat engine system cannot provide the second predefined amount of torque based on a health verification of the hybrid electric engine control module by the motor control module using a comparison of the raw PLA received at the motor control module from the power lever and a communicated PLA received at the motor control module from the hybrid electric engine control module;
in the degraded mode:
when the electric motor system cannot provide the first predefined amount of torque, eliminate a use of the electric motor system and control the heat engine system using a heat engine PLA torque schedule defining a relationship between the PLA and the torque output from the heat engine system; and
when the heat engine system cannot provide the second predefined amount of torque, eliminate a use of the heat engine system and control the electric motor system using an electric motor PLA torque schedule defining a relationship between the PLA and the torque output from the electric motor system.
2. The hybrid electric engine control system of claim 1 , wherein the hybrid electric engine control module comprises a torque splitting module configured to either pass through the PLA to the motor control module.
3. The hybrid electric engine control system of claim 1 , wherein the electric motor PLA torque schedule and/or the heat engine PLA torque schedule are linear.
4. The hybrid electric engine control system of claim 1 , wherein the hybrid electric engine control module comprises a torque splitting module configured to either pass through the PLA to a fuel flow control module or provide a heat engine motor torque value to the fuel flow control module.
5. A method comprising:
operating a hybrid electric aircraft powerplant having a heat engine system and an electric motor system in a normal mode while the heat engine system and the electric motor system are both in a normal operational state, the heat engine system including a hybrid electric engine control module for controlling the heat engine system, the electric motor system including a motor control module for controlling an electric motor of the electric motor system;
when the electric motor system and the heat engine system are in the normal mode, receiving a raw power lever angle (PLA) indicative of a torque command from a power lever and splitting output power between the electric motor system and the heat engine system as a function of the torque command;
operating the hybrid electric aircraft powerplant in a degraded mode when the electric motor system is not in a normal operational state;
operating the hybrid electric aircraft powerplant in the degraded mode when the heat engine system is not in a normal operational state based on a health verification of the hybrid electric engine control module by the motor control module using a comparison of the raw PLA received at the motor control module from the power lever and a communicated PLA received at the motor control module from the hybrid electric engine control module;
wherein operating in a degraded mode includes:
when the electric motor system is not in the normal mode, eliminating a use of the electric motor system and controlling the heat engine system using a heat engine PLA torque schedule defining a relationship between the PLA and a torque output from the heat engine system; and
when the heat engine system is not in the normal mode, eliminating a use of the heat engine system and controlling the electric motor system using an electric motor PLA torque schedule defining a relationship between the PLA and a torque output from the electric motor system.
6. A control system for a hybrid electric aircraft powerplant having a heat engine system and an electric motor system, the control system having one or more modules configured to execute the method of claim 5 .