Method for estimating an external force acting on an electrohydrostatic actuator

Patent metadata

Field	Value
Publication number	US-10976210-B2
Application number	US-201615574125-A
Country	US
Kind code	B2
Filing date	May 18, 2016
Priority date	May 18, 2015
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

The invention concerns a method for estimating an external force acting on an electrohydrostatic actuator, the actuator comprising a ram including a first chamber, a second chamber and a piston located between the first chamber and the second chamber, a pump capable of injecting fluid into the chambers for controlling a movement of the piston, and an electric motor driving the pump, the method comprising steps of: estimating, by means of at least one state observer ( 21, 22 ), a dynamic component and a static component of a difference in equivalent fluid pressure between the first chamber and the second chamber from a rotational speed of the electric motor, a position of the piston and a supply current of the electric motor, estimating the external force by means of a post-processing module ( 23 ) as a combination of the estimated dynamic component and static component of the difference in fluid pressure.

First claim

The invention claimed is:

1. A method for controlling an electrohydrostatic actuator, the actuator comprising a ram including a first chamber, a second chamber and a piston situated between the first chamber and the second chamber, a pump capable of injecting fluid into the chambers for controlling a movement of the piston, an electric motor driving the pump, by means of a control unit executing the following steps:
generating a control signal to control the electric motor,
estimating the external force acting on the electrohydrostatic actuator,
determining a correction variable of the control signal depending on the estimated external force, and
applying the correction variable to the control signal, so as to limit the fluid pressure difference between the chambers of the ram, the estimation of the external force comprising the steps of:
estimating, by means of at least one state observer, a dynamic component and a static component of an equivalent fluid pressure difference between the first chamber and the second chamber from a rotation speed of the electric motor, a position of the piston and a supply current of the electric motor,
estimating said external force by means of a post-processing module as a combination of the dynamic component and of the static component of the estimate fluid pressure difference.

2. The method according to claim 1 , wherein the estimation of the external force comprises steps of:
estimating, by means of a first state observer, the dynamic component of the equivalent fluid pressure difference between the first chamber and the second chamber, and a movement speed of the piston, from a rotation speed of the electric motor and a position of the piston, and
estimating, by means of a second state observer, the static component of the equivalent fluid pressure difference between the first chamber and the second chamber, from the movement speed of the piston estimated by the first observer, the rotation speed of the electric motor and the supply current of the electric motor.

3. The method according to claim 2 , wherein the first observer uses the rotation speed of the electric motor and the position of the piston.

4. The method according to claim 2 , wherein the second observer uses the rotation speed of the electric motor and the supply current of the electric motor, and a variable combining the movement speed of the piston and the rotation speed of the electric motor.

5. The method according to claim 2 , wherein the dynamic component of the equivalent fluid pressure difference is estimated by the first observer from a first mathematical model of the actuator in which the external force acting on the actuator is zero.

6. The method according to claim 5 , wherein the first mathematical model is in the form:

(

x
.

obs

v
.

obs

Δ
⁢

⁢

P
.

dyn_obs

)

=

(

0

1

0

0

0

μ

0

-
γ

0

)

·

(

x
obs

v
obs

Δ
⁢

⁢

P
dyn_obs

)

+

(

0

0

λ

)

·

Ω
motor

+

(

k
11

k
12

k
13

)

·

(

Assignees

• Safran Electronics & Defense

Inventors

• Feliste Nirina
• Delbecq Scott
• Mery Xavier

Classifications

• G01L1/083

  using hydraulic or pneumatic counterbalancing forces · CPC title

• B64C13/504

  using electro-hydrostatic actuators [EHA's] · CPC title

• G01L13/00

  Devices or apparatus for measuring differences of two or more fluid pressure values · CPC title

• F15B2211/761

  Control of a negative load, i.e. of a load generating hydraulic energy · CPC title

• F15B2211/7054

  Having equal piston areas · CPC title