Cascaded multi-variable control system for a turboshaft engine
A control system for a gas turbine engine is disclosed. The control system may include a computer processor. The control system may also include an outer loop control module programmed into the computer processor to determine a torque request based at least in part on a real-time collective lever angle command. The control system may also include an inner loop control module programmed into the computer processor to receive the torque request from the outer loop control module, to determine fuel flow and inlet guide vane schedules based at least in part on the received torque request, and to send signals to a gas generator of the gas turbine engine in order to control the gas generator according to the determined fuel flow and inlet guide vane schedules.
1. A control system for a gas turbine engine, comprising:
a computer processor;
an outer loop control module programmed into the computer processor configured to determine a torque request that is a torque value, based at least in part on a real-time collective lever angle command and a real-time power turbine speed; and
an inner loop control module programmed into the computer processor configured to receive the torque request from the outer loop control module, to determine fuel flow and inlet guide vane schedules based at least in part on the received torque request, and to command a gas generator of the gas turbine engine to control the gas generator according to the determined fuel flow and inlet guide vane schedules.
2. The control system of claim 1 , further comprising a load estimation module in communication with the outer loop control module, the inner loop control module, and the gas turbine engine, the load estimation module programmed to estimate the real-time power turbine speed and a real-time power turbine torque.
3. The control system of claim 2 , wherein the outer loop control module determines the torque request based at least in part on a desired power turbine speed.
4. The control system of claim 2 , wherein the inner loop control module determines the fuel flow and inlet guide vane schedules based at least in part on the real-time power turbine speed.
5. The control system of claim 1 , wherein the outer loop control module determines the torque request based at least in part on operational inputs.
6. The control system of claim 1 , wherein the outer loop control module includes inversion of a dynamic model of a rotor.
7. The control system of claim 1 , wherein the inner loop control module determines stability bleed schedules based at least in part on the received torque request, and commands the gas generator of the gas turbine engine to control the gas generator according to the determined stability bleed schedules.
8. The control system of claim 1 , wherein the inner loop control module includes inversion of a dynamic gas generator model.
9. The control system of claim 8 , wherein the dynamic gas generator model of the inner loop control module is constrained to limits of the gas turbine engine.
10. The control system of claim 9 , wherein the inner loop control module determines the fuel flow and inlet guide vane schedules based at least in part on operational inputs.
11. The control system of claim 1 , wherein the wherein the inner loop control module determines a difference between the torque request and an estimated torque in order to control the gas generator.
12. The control system of claim 2 , wherein the wherein the load estimation module estimates the real-time power turbine torque based at least on a torque sensor measurement.
13. A method for controlling a gas turbine engine, comprising:
a computer processor receiving a real-time collective lever angle command and a real-time power turbine speed;
the computer processor generating a torque request that is a torque value, based at least in part on the real-time collective lever angle command and the real-time power turbine speed;
the computer processor generating a fuel flow command and an inlet guide vane command based at least in part on the generated torque request; and
the computer processor commanding a gas generator of the gas turbine engine according to the fuel flow command and the inlet guide vane command to control a power turbine torque of the gas turbine engine.
14. The method of claim 13 , further comprising a sensor detecting the real-time power turbine speed, and sending the real-time power turbine speed to the computer processor.
15. The method of claim 13 , further comprising a sensor detecting a real-time power turbine torque, and sending the real-time power turbine torque to the computer processor.
16. The method of claim 13 , further comprising the computer processor generating a stability bleed command based at least in part on the generated torque request and commanding the gas generator according to the stability bleed command to control the power turbine torque of the gas turbine engine.
17. The method of claim 13 , further comprising the computer processor using inversion of a dynamic model of a rotor to generate the torque request, and the computer processor using inversion of a dynamic gas generator model to generate the fuel flow command and the inlet guide vane command.
18. A turboshaft engine, comprising:
a gas generator section;
a power turbine section downstream of the gas generator section; and
a control system in communication with the gas generator section and the power turbine section, the control system including at least one computer processor configured to:
receive a collective lever angle command and a power turbine speed,
generate a torque request that is a torque value, based at least in part on the collective lever angle command and the power turbine speed,
generate a fuel flow command and an inlet guide vane command based at least in part on the generated torque request, and
command the gas generator section according to the fuel flow command and the inlet guide vane command in order to control a torque of the power turbine section.
19. The turbo shaft engine of claim 18 , wherein the computer processor is configured according to a cascaded architecture.
20. The turboshaft engine of claim 19 , wherein the cascaded architecture includes an outer loop control module to generate the torque request and an inner loop control module to generate the fuel flow command and the inlet guide vane command.
21. The turboshaft engine of claim 20 , wherein the outer loop control module uses dynamic inversion of a rotor model to generate the torque request, and wherein the inner loop control module uses dynamic inversion of a gas generator model to generate the fuel flow command and the inlet guide vane command.
22. The turboshaft engine of claim 18 , wherein the computer processor is further configured to generate a stability bleed command based at least in part on the generated torque request, and to command the gas generator section according to the stability bleed command in order to control the torque of the power turbine section.