The invention relates to the field of turbopropeller control systems.
With reference to
With reference to
In the case of a centralized control system 24, the turbopropeller control system 10 comprises a multivariable corrector taking into account the screw propeller power PRW and screw propeller rotation speed XNP outputs to synthesize the fuel flow rate WF and screw propeller pitch β controls based on of screw propeller power PRWref and screw propeller rotation XNPref set points set by the pilot.
Moreover, there exist, in a turbopropeller, limits on the fuel flow rate WF and screw propeller pitch β controls imposed by the operating constraints of the turbopropeller.
In order for the calculated controls to comply with these operating constraints, it is known, as illustrated in
Yet, as each limiter 311, 312 intervenes on a control independently of the other control, the controls applied are no longer consistent with one another.
Solutions have been proposed for correcting the desynchronization of controls saturated by limiters.
One solution consists of adding supplementary states, such as temperature, pressure or altitude, so as to take operating constraints into account at the time of elaboration of the control laws. This first solution is complex to implement.
Another solution consists of recalculating the control not affected by the saturation so as to make it compatible with the saturated control. This second solution is complex to implement and its complexity increases with the number of inputs/outputs.
The prior art solutions for correcting the desynchronization of controls saturated by limiters are therefore not satisfactory.
One aim of the invention is therefore to propose a control system for a turbopropeller allowing consistent controls to be synthesized, complying with the operating constraints of the turbopropeller.
This aim is achieved in the scope of the present invention thanks to a screw propeller power PRW and a screw propeller rotation speed XNP control system of a turbopropeller based on a screw propeller power set point PRWref and a screw propeller rotation speed set point XNPref, including:
the control system being characterized in that it includes:
the values
and
being selected so that the fuel flow rate WF and screw propeller pitch β controls comply with the constraints imposed by operating constraints of the turbopropeller.
The limiting values of the errors
and
i.e. the error limits that can be corrected without violating the operating constraints of the turbopropeller, are calculated before the controls.
The screw propeller power ΔPRW and screw propeller speed ΔXNP errors calculated by the control system are then saturated by the limiting values of the errors
and
which makes it possible to guarantee that the synthesized controls will conform to the operating constraints.
The synthesized controls are therefore not saturated, which makes it possible to guarantee the consistency of the controls applied and therefore to avoid overshoots of the outputs with respect to the set points, due to the limiters.
The control system proposed is simple and effective and further has the advantage of being suited to complex systems.
The invention is advantageously completed by the following features, taken individually or in any one of their technically possible combinations.
The limiting value of the power error
is defined as the more constraining limit between:
imposed by the fuel flow rate WF constraints; and
in case of saturation of the screw propeller speed error
In particular:
The limiting value of the screw propeller speed error
is defined as the more constraining limit between:
imposed by the screw propeller pitch β constraints; and
in case of saturation of the power error
In particular:
The fuel flow rate WF constraints are a limit of variation of fuel flow rate
not to be exceeded.
The screw propeller pitch β constraints are a limit of variation of the screw propeller pitch
not to be exceeded.
When the limits {dot over (W)}Fsat(Max) and {dot over (β)}sat(Max) are maximums:
ΔPWRsat(max)=min(ΔPWRsat1(max),ΔPWRsat2(max))
ΔXNPsat(max)=min(ΔXNPsat1(max),ΔXNPsat2(max))
When the limits {dot over (W)}Fsat(Min) and {dot over (β)}sat(Min) are minimums:
ΔPWRsat(min)=max(ΔPWRsat1(min),ΔPWRsat2(min))
ΔXNPsat(min)=max(ΔXNPsat1(min),ΔXNPsat2(min))
The centralized control is a linear quadratic regulator.
The centralized control is a linear quadratic regulator with integral action.
The invention further proposes a method for controlling the screw propeller power PRW and the screw propeller rotation speed XNP of a turbopropeller based on a screw propeller power set point PRWref, and a screw propeller rotation speed set point XNPref, the method including steps of:
guaranteeing that the fuel flow rate control WF complies with constraints imposed by operating constraints of the turbopropeller;
and the screw propeller rotation speed error ΔXNP by the limiting value
Step E3 includes steps of:
based on a fuel flow rate limit
imposed by the operating constraints;
based on the power error limit
calculated during step E31 and on
based on a screw propeller pitch limit
imposed by the operating constraints;
based on the limit of the screw propeller speed error
calculated during step E33 and on
being defined as the more constraining limit between
being defined as the more constraining limit between
Other objectives, features and advantages will be revealed by the detailed description that follows with reference to the drawings, provided as illustrations and not limiting, among which:
A turbopropeller control system 10 is an onboard computer synthesizing the screw propeller pitch β and fuel flow rate controls for the turbopropeller 1 based on the screw propeller power and screw propeller rotation set points set by the pilot.
As illustrated in
The centralized control 24 is a feedback loop including a multivariable corrector 26 taking into account the screw propeller power PRW and screw propeller rotation speed XNP outputs to synthesize fuel flow rate 37 and screw propeller pitch 38 controls, without taking the operating constraints into account.
The multivariable corrector 26 is a static multivariable regulator implemented by linear combinations of the screw propeller power PRW and screw propeller rotation speed XNP values.
The multivariable corrector 26 can in particular be a linear quadratic regulator (LQR), as illustrated in
In order to ensure continuity of control, the centralized control 24 can include a single integrator 25 downstream of the limiters 11 and 12, the multivariable corrector 26 calculating the increments of control. The term used is then LQR regulator with integral feedback.
The centralized control 24 is configured to slave the screw propeller power PRW of the turbopropeller 1 to the screw propeller power set point PRWref and the screw propeller rotation speed XNP of the turbopropeller 1 to the screw propeller rotation speed set point XNPref.
In the case of an LQR regulator with integral feedback, the equations linking the controls, the output variables and the set points are given below:
The gain matrix of the centralized control 24 is determined by the known method of linear quadratic control, called LQ control.
Limiters
The limiter 11 ensures that the screw propeller rotation speed error ΔXNP, i.e. the difference between the measured screw propeller rotation speed XNP at the output of the turbopropeller and the screw propeller rotation speed set point XNPref, does not exceed a limiting value
The limiter 12 ensures that the screw propeller power error ΔPRW, i.e. the difference between the screw propeller power PRW at the output of the turbopropeller and the screw propeller power set point PRWref, does not exceed a limiting value
The limiting values
are selected so that the fuel flow rate control WF does not exceed a limiting value of fuel flow rate
and so that the screw propeller pitch control does not exceed a limiting value of the screw propeller pitch
The limits
are imposed by the operating constraints.
By way of illustration and without limitation, the limit
can be imposed by:
Temperature and pressure are measured at the inlet of the combustion chamber. For each pressure/temperature pair, there exists a fuel value not to be exceeded so as to protect the engine.
By way of illustration and without limitation, the limit
can be imposed by:
In practice, the limiters of screw propeller rotation speed error 11 and of screw propeller power error 12 can be feedback loops which run in parallel with the feedback loop of the centralized control.
When the limits {dot over (W)}Fsat(Max) and {dot over (β)}sat(Max) are a maximum, the associated limiting values ΔXNPsat(Max) and ΔPRWsat(Max) are maximums. Likewise, when the limit {dot over (W)}Fsat(Min) or {dot over (β)}sat(Min) is a minimum, the associated limiting values ΔXNPsat(Min) are minimums.
If the limiting value ΔXNPsat(max) (respectively ΔPRWsat(max)) is a maximum, the limiter saturates the error (i.e., it replaces the value of the error measured by the centralized control with the limiting value) when the measured error is greater than the limiting value ΔXNPsat(max) (respectively ΔPRWsat(max)).
If the limiting value ΔXNPsat(min) (respectively ΔPRWsat(min)) is a minimum, the limiter saturates the error (i.e., it replaces the value of the error measured by the centralized control with the limiting value) when the measured error is less than the limiting value ΔXNPsat(min) (respectively ΔPRWsat(min))
Turbopropeller Control Method
The control system 10 implements a turbopropeller 1 control method which consists of synthesizing screw propeller pitch and fuel flow rates controls for the turbopropeller 1 based on screw propeller power and screw propeller rotation set points set by the pilot.
The control method includes the following steps:
the limiting values
being selected so that the fuel flow rate control WF does not exceed a limiting value of fuel flow rate
imposed by operating constraints of the engine and so that the screw propeller pitch control β does not exceed a limiting value of the screw propeller pitch
imposed by operating constraints of the engine;
and of the screw propeller rotation speed error ΔXNP by the limiting value
During step E3, the limiting value of the error of each variable is defined, taking into account the effect that saturation of the error would have on the other variable.
To this end, the limiting values
are calculated according to the following steps:
based on
based on the allowable limit of the power error
calculated during step E31 and on
based on
based on the allowable limit of the screw propeller speed error
calculated during step E33 and on
in case of saturation of the screw propeller speed error.
based on the allowable fuel flow rate and screw propeller pitch.
The limiting value of the power error
being defined as the more constraining limit between:
imposed by the limiting value of the fuel flow rate
calculated in E31 and;
in case of saturation of the screw propeller speed error as calculated in E34.
The limiting value of the screw propeller speed error
is defined as the more constraining limit between:
imposed by the limiting value of the screw propeller pitch
calculated in E33; and
in case of saturation of the power error as calculated in E32.
In particular:
The limiting values
are calculated upstream of the controls. The screw propeller power ΔPRW and screw propeller speed ΔXNP errors calculated by the control system are then saturated by the limiting values of the errors
which makes it possible to guarantee that the controls calculated by the centralized control will conform to the operating constraints. The synthesized controls will therefore not be saturated, which will make it possible to guarantee the consistency of the controls applied and therefore avoid overshoots with respect to the set points.
As illustrated in
Number | Date | Country | Kind |
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16 57739 | Aug 2016 | FR | national |
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5274558 | High et al. | Dec 1993 | A |
9845145 | Lu | Dec 2017 | B2 |
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201729270 | Feb 2011 | CN |
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Entry |
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Preliminary Research Report received for French Application No. 1657739, dated Apr. 3, 2017, 3 pages (1 page of French Translation Cover Sheet and 2 pages of original document). |
GB Search Report for Patent Application No. 1712716.8, dated Jan. 24, 2018, 3 pages. |
Number | Date | Country | |
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20180045123 A1 | Feb 2018 | US |