Patent Description:
To control the power request for a hybrid electric aircraft, the control system is required to calculate the power request for both the thermal engine and the electric motor system components. In addition, e.g. for a turboprop aircraft, a propeller/engine speed is commanded for the low speed/power portion of flight.

It is required to transition into and out of the various control loops without any adverse transient or steady state effects while meeting the constraints of the electrical and thermal engine such as maximum output, response rate, protection functions, and the like.

The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for control loops for hybrid electric aircraft. This disclosure provides a solution for this need.

Examples of the prior art are provided by <CIT> and <CIT>.

A method of controlling a hybrid-electric aircraft powerplant includes, for a hybrid-electric aircraft powerplant having a thermal engine and an electric motor, running a first control loop for command of the thermal engine based on the total response commanded for the hybrid-electric powerplant and torque feedback from the thermal engine. The method includes running a second control loop in parallel with the first control loop for commanding the thermal engine based on the maximum thermal engine output and torque feedback from the thermal engine. The method includes using a low selector between the first control loop and the second control loop to command the thermal engine with the lower of responses commanded from the first and second control loops. The method includes running a third control loop in parallel with the first and second control loops for commanding engine/propeller speed, wherein the third control loop outputs a speed control enable or disable status, and using a high selector between output of the third control loop and the low selector. The method includes running a fourth control loop in parallel with the first, second, and third control loops for commanding the electric motor with non-zero demand when the second control loop is above control to add response from the electric motor to response from the thermal engine to achieve the response commanded.

The response in total response commanded and total response in the first control loop can be torque. The response in the total response commanded in the second control loop can be torque. The response in the fourth control loop can be torque.

Commanding the thermal engine can include controlling fuel flow to the thermal engine. Commanding the electric motor can include controlling electrical power supplied to the electric motor. The electric motor and thermal engine can be connected together in parallel to a combining gear box (CGB) to drive a propeller. The combining gear box can connect to the propeller through a reduction gear box (RGB). Sensory feedback from the RGB can be combined with sensory feedback from the electric motor to determine torque feedback from the thermal engine.

A system includes a hybrid-electric powerplant for an aircraft including a thermal engine and an electric motor each operatively connected to provide torque to drive an air mover for thrust. A first control loop is connected for command of the thermal engine based on the total response commanded for the hybrid-electric powerplant and torque feedback from the thermal engine. A second control loop is connected in parallel with the first control loop for commanding the thermal engine based on the maximum thermal engine output and torque feedback from the thermal engine. A low selector is connected between the first control loop and the second control loop to command the thermal engine with the lower of responses commanded from the first and second control loops. A third control loop is connected in parallel with the first and second control loops for commanding engine/propeller speed, wherein the third control loop outputs a speed control enable or disable status. A high selector is connected between output of the third control loop and the low selector. A fourth control loop is connected in parallel with the first, second, and third control loops for commanding the electric motor with non-zero demand when the second control loop is above control to add response from the electric motor to response from the thermal engine to achieve the response commanded.

The air mover can be a propeller. The electric motor and thermal engine can be connected together in parallel to a combining gear box (CGB) to drive the propeller. The combining gear box can connect to the propeller through a reduction gear box (RGB).

So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to:
<FIG> is a schematic view or simulation diagram of an embodiment of a system constructed in accordance with the present disclosure, showing the four parallel control loops.

For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a system in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. The systems and methods described herein can be used for controlling hybrid-electric powerplants such as for driving air movers for aircraft thrust.

The system <NUM> includes a hybrid-electric powerplant <NUM> for an aircraft including a thermal engine <NUM> and an electric motor <NUM> each operatively connected to provide torque to drive an air mover, e.g. propeller <NUM>, for thrust. The air mover is a propeller <NUM>, however those skilled in the art will readily appreciate that any other suitable type of air mover such as a fan, ducted fan, or the like can be used without departing from the scope of this disclosure. The electric motor <NUM> and thermal engine <NUM> are connected together in parallel to a combining gear box (CGB) <NUM>. The CGB <NUM> connects to the propeller <NUM> through a reduction gear box (RGB) <NUM>.

A first control loop <NUM> is connected for command of the thermal engine <NUM> based on error between total torque (MrqTot) commanded, e.g. commanded from a pilot or autonomous system, for the hybrid-electric powerplant <NUM> and MfbTM, torque feedback from the thermal engine <NUM>. Commanding the thermal engine <NUM> includes controlling fuel flow to the thermal engine.

A second control loop <NUM> is connected in parallel with the first control loop <NUM> for commanding the thermal engine <NUM> based on error between maximum thermal engine output (MrqTMMax) and torque feedback from the thermal engine MfbTM. A low selector <NUM> is connected between the first control loop <NUM> and the second control loop <NUM> to command the thermal engine <NUM> with the lower of the responses commanded from the first and second control loops <NUM>, <NUM>. While torque is used herein as an example of response used for feedback control, those skilled in the art will readily appreciate that any suitable response can be used, such as speed, power, or the like, without departing from the scope of this disclosure.

A third control loop <NUM> is connected in parallel with the first and second control loops <NUM>, <NUM> for commanding speed of the thermal engine <NUM> (and/or the propeller <NUM>). The third control loop <NUM> outputs a speed control enable or disable status of the speed controller <NUM>. A high selector <NUM> is connected between combined output of the third control loop/speed controller <NUM>, <NUM> (anded by anding component <NUM>) and the low selector <NUM> to output MrqTM (torque demanded from the thermal engine <NUM>). Sensor feedback <NUM> from the RGB (MfbTH in <FIG>) is combined with sensor feedback from the electric motor (MfbEM in <FIG>) at box <NUM> to determine torque feedback from the thermal engine, MfbTM. The prioritization component selects the correct commanded or requested torque MrqTM from among the first, second, and third control loops <NUM>, <NUM>, <NUM>. The requested or commanded torque MrqTM is summed/differenced with the torque feedback from the thermal engine MfbTM at component <NUM>, which outputs the error between the two (MrqTM and MfbTM). This sum/difference is passed to the major control loop <NUM>, which outputs WfRq (fuel flow required to the thermal engine <NUM>) to the minor control loop <NUM>, which outputs Wf (actual fuel flow going to the thermal engine <NUM>) to the thermal engine <NUM>.

A fourth control loop <NUM> is connected in parallel with the first, second, and third control loops <NUM>, <NUM>, <NUM> for commanding the electric motor <NUM> with non-zero demand when the second control loop <NUM> is above control to add response (e.g. torque) from the electric motor <NUM> to response (e.g. torque) from the thermal engine <NUM> to achieve the response commanded. Commanding the electric motor <NUM> includes controlling electrical power supplied to the electric motor <NUM>. The fourth control loop <NUM> outputs MrqEM, requested torque for the electric motor <NUM>. This is summed/differenced with feedback <NUM> from the electric motor <NUM> at component <NUM>, which outputs the error between the two (MrqEM, MfbRM). This sum/difference is passed through the major loop control <NUM>, which outputs iEMrq (current commanded by the electronic powertrain controller or EPC) to the minor loop control <NUM>, which outputs iEM (actual current going to the EPC) to the electric motor <NUM>.

The first control loop <NUM> includes a proportional-integral-derivative (PID) integrator <NUM> that receives as input the output of a summation/differencing component <NUM>. The component <NUM> receives total torque demanded or commanded MrqTot and torque feedback of the thermal engine <NUM> MfbTM, and outputs the sum/difference to the integrator <NUM>. The integrator <NUM> outputs to the low selector <NUM>.

The second control loop <NUM> includes a PID integrator <NUM> that receives the output of a summation/differencing component <NUM>. The component <NUM> receives maximum torque output of the thermal engine <NUM> (MrqTMmax) and torque feedback of the thermal engine <NUM> (MfbTM), and outputs the sum/difference to the integrator <NUM>. The integrator <NUM> outputs to the low selector <NUM> for selection of the lower of the two outputs of the first and second control loops <NUM>, <NUM> as described above.

The speed controller <NUM> of the third control loop <NUM> incudes a PID integrator <NUM> that receives the output of a summation/differencing component <NUM>. The component <NUM> receives propeller speed commanded or required (Nrq) and actual propeller speed feedback (Nfb), and outputs the sum/difference to the integrator <NUM>. The integrator <NUM> outputs to the anding component <NUM> to the integral output is anded with the beta mode input of the third control loop <NUM> a described above. The beta mode in this context, and the box labeled "Beta Mode" in <FIG>, refer to speed control mode for the engine control system.

The fourth control loop <NUM> includes a PID integrator <NUM> that receives the output of a summation/differencing component <NUM>. The component <NUM> receives the difference between total torque demanded or commanded and maximum torque output of the thermal engine <NUM> (MrqTot minus MrqTMmax) and sums/differences this with torque feedback of the electric motor <NUM> (MfbEM) to outputs the sum/difference to the integrator <NUM>. The integrator <NUM> outputs to the <NUM> as described above.

The methods herein include constantly resetting a respective integrator <NUM>, <NUM>, <NUM>, <NUM> to the value of the loop in control, defined as the loop whose torque request is selected as MrqTM based on the prioritization component <NUM>, while the respective control loop is running in the background and is not actively commanding, thus preventing integrator windup error and assuring seamless transition between loops actively controlling the thermal engine <NUM>. The respective integrators <NUM>, <NUM>, <NUM>, <NUM> are reset with a respective reset command ("Loop in ctrl" in <FIG>) once a respective control loop <NUM>, <NUM>, <NUM> begins actively commanding.

For each control loop <NUM>, <NUM>, <NUM>, <NUM>, the PID control integrator path (including the respective integrator <NUM>, <NUM>, <NUM>, <NUM>) is reset to the value of the loop in control. For example if the first control loop <NUM> is in control (meaning MrqTM=signal from the integrator <NUM> of the first control loop <NUM> (Loop <NUM> in <FIG>), the integrators <NUM>, <NUM> of the PID controllers for the second and third control loops <NUM>, <NUM> (Loops <NUM> and <NUM> in <FIG>) are reset to the value of the signal coming from the PID controller (integrator <NUM>) of the first control loop <NUM> (Loop <NUM> in <FIG>). This is indicated in <FIG> for each of the integrators <NUM>, <NUM>, <NUM> by the respective arrow designated "Loop in ctl.

Potential benefits of this disclosure include the following. It is possible to control the power demand of a hybrid-electric powerplant without any abrupt transitions between control loops. The parallel control loops can ensure continuous control of the propulsion system. This architecture can provide an opportunity to adjust the overall system power response of the hybrid-electric powerplant by adjusting the gains and constants of the individual control loops. This can also allow for switching commands from energy/torque demand to a particular engine or propeller speed command.

Claim 1:
A method of controlling a hybrid-electric aircraft powerplant (<NUM>) comprising:
for a hybrid-electric aircraft powerplant (<NUM>) having a thermal engine (<NUM>) and an electric motor (<NUM>), running a first control loop (<NUM>) for command of the thermal engine (<NUM>) based on an error between a total response commanded for the hybrid-electric aircraft powerplant (MrqTot) and torque feedback from the thermal engine (MfbTM);
running a second control loop (<NUM>) in parallel with the first control loop (<NUM>) for commanding the thermal engine (<NUM>) based on an error between a maximum thermal engine output (MrqTMmax) and torque feedback from the thermal engine (MfbTM);
using a low selector (<NUM>) between the first control loop (<NUM>) and the second control loop (<NUM>) to command the thermal engine (<NUM>) with the lower of responses commanded from the first and second control loops (<NUM>, <NUM>);
running a third control loop (<NUM>) in parallel with the first and second control loops (<NUM>, <NUM>) for commanding engine/propeller speed, wherein the third control loop (<NUM>) outputs a speed control enable or disable status;
using a high selector (<NUM>) between output of the third control loop (<NUM>) and the low selector (<NUM>); and
running a fourth control loop (<NUM>) in parallel with the first, second, and third control loops (<NUM>, <NUM>, <NUM>) for commanding the electric motor (<NUM>) with non-zero demand when the second control loop (<NUM>) is above control to add response from the electric motor (<NUM>) to response from the thermal engine (<NUM>) to achieve the total response commanded for the hybrid-electric aircraft powerplant (MrqTot).