Load estimation for a twin-engine helicopter

1. A control system for an aircraft using at least one gas turbine engine, the control system comprising:

a controller that includes a load control module and an engine control module and is configured to communicate control signals to a plant, the plant including a gas generator and a rotor load;

an engine estimation module configured to receive engine state measurements from the plant and effector feedback/command signals from the controller and communicate a power turbine torque (QPT_SVM) estimate to the controller; and

a load estimation module that is configured to receive one or more signals including one or more of: the QPT_SVM estimate, a first power turbine speed (NP_sig) value, a first power turbine torque (QPT_sig) value, a second power turbine speed (NP_sigR) value, a second power turbine torque (QPT_sigR) value, and a rotor speed (NR_sig) value,

wherein the load estimation module is configured to generate one or more of: a power turbine speed estimate (NP_est), a power turbine torque estimate (Qpt_est), and a rotor load estimate (QR_est) based on the one or more received signals.

2. The control system of claim 1 , wherein the engine state measurements includes one or more of a Speed (N) measurement, a Pressure (P) measurement, and Temperature (T) measurement.

3. The control system of claim 1 , wherein effector feedback/command signals includes one or more of a fuel (WF), stability bleed (BLD) schedule, and inlet guide vane (IGV) schedules.

4. The control system of claim 1 , wherein the load estimation module is configured to provide the power turbine speed estimate (NP_est) to the load control module.

5. The control system of claim 1 , wherein the load estimation module is configured to provide the power turbine torque estimate (Qpt_est) to the engine control module.

6. The control system of claim 1 , wherein the load estimation module comprises:

a power turbine speed (NP) estimation module.

7. The control system of claim 6 , wherein the power turbine speed (NP) estimation module comprises:

input ports configured to receive the NR_sig, NP_sigR, and NP_sig;

a calculation module configured to sum the NP_sigR and NP_sig values, divide the summed value by two, subtract the NR_sig from the summed and divided value generating an intermediate value;

a low-pass filter G 1 ( s ) that is configured to filter the intermediate value;

the calculation module is configured to sum the NR_sig back into the output from the low-pass filter generating a second intermediate value;

and one or more notch filters configured to filter the output from a second low-pass filter providing a power turbine speed estimate (NP_est) output.

8. The control system of claim 1 , wherein the load estimation module comprises:

an power turbine torque (QPT) estimation module.

9. The control system of claim 8 , wherein the power turbine torque (QPT) estimation module comprises:

input ports that receive the QPT_sig, NP_est from the NP estimation module, and the QPT_svm;

a low-pass filter and one or more notch filters that filter the QPT_sig;

a calculation module configured to processes the NP_est, subtracts the processed NP_est value from the filtered QPT_sig, and subtracts the QPT_svm creating an intermediate signal;

a second low-pass filter that filter the intermediate signal; and

the calculation module that adds the QPT_svm signal back into the filtered intermediate signal creating the QPT_est that is output from the QPT estimation module.

10. The control system of claim 1 , wherein the load estimation module comprises:

a rotor load estimation module.

11. The control system of claim 10 , wherein the rotor load estimation module comprises:

input ports configured to receive the QPT_estR, QPT_est, and NP_est, a collective pitch signal (CLA), and flight conditions;

a calculation module configured to sum QPT_estR together with QPT_est; process NP_est, and then subtract the processed NP_est from the summed value creating a first intermediate value;

a rotor load model configured to receive NP_est, the collective pitch signal (CLA), and the flight conditions and generates an output value (QR_pre) based on the input collective pitch signal (CLA), NP_est, and flight conditions;

the calculation module is further configured to subtract the QR_pre value from the first intermediate value creating a second intermediate value;

a low-pass filter G(s) configured to filter the second intermediate value; and

the calculation module is additionally configured to sum the QR_pre value back into the filtered second intermediate value creating a rotor load estimate (QR_est) that is output from the rotor load estimation module.

12. A computer implemented method for an aircraft to calculate rotor load estimation, the method comprising:

receiving, by a processor, one or more signals including one or more of: a power turbine torque (QPT_SVM) estimate, a first power turbine speed (NP_sig) value, a first power turbine torque (QPT_sig) value, a second power turbine speed (NP_sigR) value, a second power turbine torque (QPT_sigR) value, and a rotor speed (NR_sig) value;

generating, by the processor, one or more of: a power turbine speed estimate (NP_est), a power turbine torque estimate (Qpt_est), and a rotor load estimate (QR_est) based on the one or more received signals; and

transmitting one or more of the NP_est, Qpt_est, and QR_est.

13. The computer implemented method of claim 12 , wherein generating the one or more of NP_est, Qpt_est, and QR_est further comprises:

receiving, at input ports of a power turbine speed (NP) estimation module, the NR_sig, NP_sigR, and NP_sig;

calculating using a calculation module an intermediate signal, wherein the calculation module sums the NP_sigR and NP_sig values, divides the summed value by two, subtracts the NR_sig from the summed and divided value generating the intermediate value;

filtering, using a low-pass filter G 1 ( s ), the intermediate value;

calculating using the calculation module a second intermediate signal, wherein the calculation module sums the NR_sig back into the output from the low-pass filter generating the second intermediate value;

filtering, using a second low-pass filter, the second intermediate value; and

filtering, using one or more notch filters, the output from the second low-pass filter generating a power turbine speed estimate (NP_est) output.

14. The computer implemented method of claim 12 , wherein generating the one or more of NP_est, Qpt_est, and QR_est further comprises:

receiving, at input ports of the power turbine torque (QPT) estimation module, the QPT_sig, NP_est from the NP estimation module, and the QPT_svm;

filtering, using a low-pass filter and, one or more notch filters, the QPT_sig;

calculating using a calculation module an intermediate signal, wherein the calculation module processes the NP_est, subtracts the processed NP_est value from the filtered QPT_sig, and subtracts the QPT_svm creating the intermediate signal;

filtering, using a second low-pass filter, the intermediate signal; and

calculating QPT_est, using the calculation module, wherein the calculation module adds the QPT_svm signal back into the filtered intermediate signal creating the QPT_est that is output from the QPT estimation module.

15. The computer implemented method of claim 12 , wherein generating the one or more of NP_est, Qpt_est, and QR_est further comprises:

receiving, at input ports of the rotor load estimation module, the QPT_estR, QPT_est, NP_est, a collective pitch signal (CLA), and flight conditions;

calculating using a calculation module a first intermediate value, wherein the calculation module sums QPT_estR together with QPT_est; processing NP_est, and then the processed NP_est is subtracted from the summed value creating the first intermediate value;

receiving at a rotor load model the NP_est, the collective pitch signal (CLA), and the flight conditions;

generating at the rotor load model an output value (QR_pre) based on the input collective pitch signal (CLA), NP_est, and flight conditions;

calculating a second intermediate value using the calculation module, wherein the calculation module subtracts the QR_pre value from the first intermediate value creating the second intermediate value;

filtering, using a low-pass filter G(s), the second intermediate value; and

generating a rotor load estimate (QR_est), wherein the calculation module sums the QR_pre value back into the filtered second intermediate value creating the rotor load estimate (QR_est) that is output from the rotor load estimation module.

16. A computer program product for an aircraft to calculate a rotor load estimation, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by one or more processors to cause the processors to:

receive, by a processor of a load estimation module, one or more signals including one or more of a power turbine torque (QPT_SVM) estimate, a first power turbine speed (NP_sig) value, a first power turbine torque (QPT_sig) value, a second power turbine speed (NP_sigR) value, a second power turbine torque (QPT_sigR) value, and a rotor speed (NR_sig) value;

generate, using the processor of the load estimation module, one or more of a power turbine speed estimate (NP_est), a power turbine torque estimate (Qpt_est), and a rotor load estimate (QR_est) based on the one or more received signals; and

transmit one or more of the NP_est, Qpt_est, and QR_est.

17. The computer program product of claim 16 , wherein the computer program product comprising additional program instructions executable by the one or more processors to cause the processors to:

receive, at input ports of a power turbine speed (NP) estimation module, the NR_sig, NP_sigR, and NP_sig;

calculate using a calculation module an intermediate signal, wherein the calculation module sums the NP_sigR and NP_sig values, divides the summed value by two, subtracts the NR_sig from the summed and divided value generating the intermediate value;

filter, using a low-pass filter G 1 ( s ), the intermediate value;

calculate using the calculation module a second intermediate signal, wherein the calculation module sums the NR_sig back into the output from the low-pass filter generating the second intermediate value;

filter, using a second low-pass filter, the second intermediate value; and

filter, using one or more notch filters, the output from the second low-pass filter generating a power turbine speed estimate (NP_est) output.

18. The computer program product of claim 16 , wherein the computer program product comprising additional program instructions executable by the one or more processors to cause the processors to:

receive, at input ports of the power turbine torque (QPT) estimation module, the QPT_sig, NP_est from the NP estimation module, and the QPT_svm;

filter, using a low-pass filter and, one or more notch filters, the QPT_sig;

calculating using a calculation module an intermediate signal, wherein the calculation module processes the NP_est, subtracts the processed NP_est value from the filtered QPT_sig, and subtracts the QPT_svm creating the intermediate signal;

filter, using a second low-pass filter, the intermediate signal; and

calculate QPT_est, using the calculation module, wherein the calculation module adds the QPT_svm signal back into the filtered intermediate signal creating the QPT_est that is output from the QPT estimation module.

19. The computer program product of claim 16 , wherein the computer program product comprising additional program instructions executable by the one or more processors to cause the processors to:

receive, at input ports of the rotor load estimation module, the QPT_estR, QPT_est, NP_est, a collective pitch signal (CLA), and flight conditions;

calculate using a calculation module a first intermediate value, wherein the calculation module sums QPT_estR together with QPT_est; processing NP_est, and then the processed NP_est is subtracted from the summed value creating the first intermediate value;

receive at a rotor load model the NP_est, the collective pitch signal (CLA), and the flight conditions;

generate at the rotor load model an output value (QR_pre) based on the input collective pitch signal (CLA), NP_est, and flight conditions;

calculating a second intermediate value using the calculation module, wherein the calculation module subtracts the QR_pre value from the first intermediate value creating the second intermediate value;

filter, using a low-pass filter G(s), the second intermediate value; and

generate a rotor load estimate (QR_est), wherein the calculation module sums the QR_pre value back into the filtered second intermediate value creating the rotor load estimate (QR_est) that is output from the rotor load estimation module.