Systems and methods for managing noise in compact high speed and high force hydraulic actuators
Presented herein are systems and methods for attenuating certain pulsations in a hydraulic system comprising a pump and a hydraulic actuator. In certain aspects, an accumulator comprising an internal volume that is divided into a working chamber and a contained chamber may be utilized to at least partially attenuate propagation of certain pulsations in the system. The working chamber may be fluidically coupled to the pump via a first flow path and fluidically coupled to a chamber of the actuator via a second flow path. The system may be designed such that a first inertance of the first flow path is greater than a second inertance of the second flow path. Additionally or alternatively, the system may be designed such that a resonance associated with the first inertance and a compliance of the accumulator may occur at a resonance frequency of less than 90 Hz.
1. A hydraulic apparatus comprising:
a hydraulic actuator comprising an actuator housing that at least partially defines a compression chamber and an extension chamber;
a pump; and
a compression-side accumulator comprising:
a compression-side accumulator housing defining a first internal volume that is divided, by a first barrier, into a first contained chamber and a first working chamber, wherein:
the first working chamber is fluidically coupled to the pump by a compression-side first flow path having a first inertance;
the first working chamber is fluidically coupled to the compression chamber by a compression-side second flow path having a second inertance; and
the first inertance is larger than the second inertance.
2. The hydraulic apparatus of claim 1 , wherein a first TFmag of a first transfer function has at least one of a first global maximum or first local maximum at a first frequency, and a second TFmag of a second transfer function has at least one of a second global maximum or second local maximum at a second frequency, wherein:
the second frequency is higher than the first frequency;
the first transfer function describes a first relationship between pressure at a first point and pressure at a second point;
the second transfer function describes a second relationship between pressure at the second point and pressure at a third point;
the first point is located in one of: the pump, a port of the pump, or the compression-side first flow path;
the second point is located in the first internal volume of the compression-side accumulator; and
the third point is located in the compression chamber of the hydraulic actuator.
3. The hydraulic apparatus of claim 2 , wherein the second frequency is equal to at least 5 or at least 20 times the first frequency.
4. The hydraulic apparatus of claim 3 , wherein the second frequency is greater than the first frequency by a factor of less than 100.
5. The hydraulic apparatus of claim 2 , wherein the first frequency is higher than a first lower limit and lower than a first upper limit, wherein the first lower limit is one of 0 Hz, 2 Hz, 5 Hz, or 10 Hz and the first upper limit is one of 100 Hz, 80 Hz, 60 Hz, 50 Hz, 30 Hz, 20 Hz, or 15 Hz.
6. The hydraulic apparatus of claim 2 , wherein the second frequency is higher than a second lower limit and lower than a second upper limit, wherein the second lower limit is one of 100 Hz, 200 Hz, 300 Hz, 400 Hz, or 500 Hz and the second upper limit is one of 800 Hz, 1000 Hz, or 1500 Hz.
7. The hydraulic apparatus of claim 1 , wherein a first TFph of a first transfer function is equal to +/−90° at a first frequency, and a second TFph of a second transfer function is equal to +/−90° at a second frequency, wherein
the first transfer function describes a first relationship between pressure at a first point and pressure at a second point;
the second transfer function describes a second relationship between pressure at the second point and pressure at a third point;
the first point is located in one of: the pump, a port of the pump, and the compression-side first flow path;
the second point is located in the first internal volume of the compression-side accumulator; and
the third point is located in the compression chamber of the hydraulic actuator.
8. The hydraulic apparatus of claim 7 , wherein the compression-side accumulator is a type-2 accumulator.
9. The hydraulic apparatus of claim 7 , further comprising:
an extension flow path fluidically coupling the pump to the extension chamber; and
an extension-side accumulator comprising:
an extension-side accumulator housing defining a second internal volume that is divided, by a second barrier, into a second contained chamber and a second working chamber, wherein:
the second working chamber is fluidically coupled to the pump via an extension-side first flow path; and
the second working chamber is fluidically coupled to the compression chamber via an extension-side second flow path.
10. The hydraulic apparatus of claim 1 , wherein the compression-side accumulator is a type-2 accumulator.
11. The hydraulic apparatus of claim 1 , further comprising:
an extension flow path fluidically coupling the pump to the extension chamber; and
an extension-side accumulator comprising:
an extension-side accumulator housing defining a second internal volume that is divided, by a second barrier, into a second contained chamber and a second working chamber, wherein:
the second working chamber is fluidically coupled to the pump via an extension-side first flow path; and
the second working chamber is fluidically coupled to the compression chamber via an extension-side second flow path.
12. The hydraulic apparatus of claim 11 , wherein the extension-side accumulator has a second stiffness and the compression-side accumulator has a first stiffness, wherein the second stiffness is greater than the first stiffness.
13. The hydraulic apparatus of claim 11 , wherein the extension-side accumulator is a type-2 accumulator.
14. The hydraulic apparatus of claim 13 , wherein the compression-side accumulator is a type-2 accumulator.
15. A hydraulic apparatus comprising:
a hydraulic actuator comprising an actuator housing that at least partially defines a compression chamber of the hydraulic actuator and an extension chamber of the hydraulic actuator;
a bi-directional pump; and
a compression-side accumulator comprising:
a compression-side accumulator housing defining a first internal volume that is divided, by a first barrier, into a first contained chamber and a first working chamber, wherein the first contained chamber includes a compressible fluid, and wherein:
the first working chamber is fluidically coupled to the bi-directional pump by a compression-side first flow path;
the first working chamber is fluidically coupled to the compression chamber of the hydraulic actuator by a compression-side second flow path;
wherein the compression-side first flow path is entirely distinct from the compression-side second flow path, and wherein at least one of (a) or (b) is true;
(a) a first TFmag of a first transfer function has at least one of a first global maximum or first local maximum at a first frequency, and a second TFmag of a second transfer function has at least one of a second global maximum or second local maximum at a second frequency, wherein the second frequency is higher than the first frequency;
(b) a first TFph of the first transfer function is equal to +/−90° at a first frequency, and a second TFph of a second transfer function is equal to +/−90° at a second frequency, wherein the second frequency is higher than the first frequency and wherein:
the first transfer function describes a first relationship between pressure at a first point and pressure at a second point;
the second transfer function describes a second relationship between pressure at the second point and pressure at a third point;
the first point is located in one of: the bi-directional pump, a port of the bi-directional pump, and the compression-side first flow path;
the second point is located in the first internal volume of the compression-side accumulator; and
the third point is located in the compression chamber of the hydraulic actuator.
16. The hydraulic apparatus of claim 15 , wherein (a) is true.
17. The hydraulic apparatus of claim 15 wherein (b) is true.
18. The hydraulic apparatus of claim 15 , wherein the second frequency is higher than the first frequency by a factor of at least 5.
19. The hydraulic apparatus of claim 18 , wherein the compression-side accumulator is a type-2 accumulator.
20. The hydraulic apparatus of claim 15 , wherein the first frequency is higher than a first lower limit and lower than a first upper limit, wherein the first lower limit is one of 0 Hz, 2 Hz, 5 Hz, or 10 Hz and the first upper limit is one of 100 Hz, 80 Hz, 60 Hz, 50 Hz, 30 Hz, 20 Hz, or 15 Hz.
21. The hydraulic apparatus of claim 15 , wherein the second frequency is higher than a second lower limit and lower than a second upper limit, wherein the second lower limit is one of 100 Hz, 200 Hz, 300 Hz, 400 Hz, or 500 Hz and the second upper limit is one of 800 Hz, 1000 Hz, or 1500 Hz.
22. The hydraulic apparatus of claim 15 , wherein the compression-side first flow path is the shortest flow path of a first set of one or more flow paths, and the compression-side second flow path is the shortest flow path of a second set of one or more flow paths, wherein:
the first set of one or more flow paths consists of each flow path of the hydraulic apparatus that fluidically couples the bi-directional pump to the first working chamber; and
the second set of one or more flow paths consists of each flow path of the hydraulic apparatus that fluidically couples the first working chamber to the compression chamber.
23. The hydraulic apparatus of claim 15 , wherein the compression-side accumulator is a type-2 accumulator.
24. The hydraulic apparatus of claim 15 , wherein the compression-side first flow path has a first inertance, the compression-side second flow path has a second inertance, and wherein the first inertance is larger than the second inertance.