Hydraulic fluid flow control

1. A hydraulic fluid system, comprising:

a first hydraulic motor comprising an output;

a first magneto-rheological fluid (MRF) brake interconnected with the output of the first hydraulic motor, the first MRF brake comprising a magneto-rheological fluid, wherein the first hydraulic motor and the first MRF brake define a first set;

a second hydraulic motor and a second MRF brake operatively interconnected with the second hydraulic motor and that defines a second set, wherein the first set and the second set are connected in series;

a third hydraulic motor and a third MRF brake operatively interconnected with the third hydraulic motor and that defines a third set;

a fourth hydraulic motor and a fourth MRF brake operatively interconnected with the fourth hydraulic motor and that defines a fourth set, wherein the third set and the fourth set are connected in series, and wherein the first set and the second set are collectively connected in parallel with the third set and the fourth set; and

a controller coupled to at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake,

wherein the controller is configured to control an amount of current flowing through a magnetic coil of the at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake based on an input,

wherein the current flowing through the magnetic coil of the at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake corresponds with a viscosity of the magneto-rheological fluid of the at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake, and

wherein the input to the controller is selected from a group consisting of a differential pressure between an input side of at least one of the first hydraulic motor, the second hydraulic motor, the third hydraulic motor, or the fourth hydraulic motor and an output side of the at least one of the first hydraulic motor, the second hydraulic motor, the third hydraulic motor, or the fourth hydraulic motor and an operational speed of the at least one of the first hydraulic motor, the second hydraulic motor, the third hydraulic motor, or the fourth hydraulic motor.

2. The hydraulic fluid system of claim 1 , wherein the first hydraulic motor comprises an idler gear and an output gear, and wherein said MRF brake is interconnected with the output gear.

3. The hydraulic fluid system of claim 1 , further comprising:

a hydraulic fluid circuit fluidly connected with the first hydraulic motor, wherein the magneto-rheological fluid of the first MRF brake is fluidly isolated from the hydraulic fluid circuit.

4. The hydraulic fluid system of claim 1 , wherein the first MRF brake comprises a rotatable rotor disposed within the magneto-rheological fluid.

5. The hydraulic fluid system of claim 1 , wherein the first hydraulic motor comprises a motor housing and the first MRF brake comprises a brake housing, and wherein the motor housing is completely separate from the brake housing.

6. The hydraulic fluid system of claim 1 , further comprising a common hydraulic load fluidly connected with each of the first hydraulic motor, the second hydraulic motor, the third hydraulic motor, and the fourth hydraulic motor.

7. The hydraulic fluid system of claim 1 , further comprising a housing assembly, wherein the first hydraulic motor and the first MRF brake are disposed within the housing assembly.

8. The hydraulic fluid system of claim 7 , further comprising a first shaft, wherein the output comprises an output gear mounted on the first shaft at a first location, and wherein the first MRF brake comprises a rotor mounted on the first shaft at a second location that is spaced from the first location.

9. The hydraulic fluid system of claim 8 , further comprising a seal engaged with the first shaft between the first location and the second location.

10. The hydraulic fluid system of claim 7 , wherein the housing assembly comprises a motor housing, a brake housing, and a housing disposed between and engaged with each of the motor housing and the brake housing.

11. A method of controlling a hydraulic fluid system, comprising:

directing a hydraulic fluid through at least one of a first hydraulic motor comprising an output, a second hydraulic motor, a third hydraulic motor, or a fourth hydraulic motor;

applying a braking torque to the output using at least one of a first magneto-rheological fluid (MRF) brake, a second MRF brake, a third MRF brake, or a forth MRF brake, the applying comprising using a magneto-rheological fluid, wherein the first MRF brake is operatively interconnected with the first hydraulic motor and define a first set, wherein the second MRF brake is operatively interconnected with the second hydraulic motor and define a second set, wherein the first set and the second set are connected in series, wherein the third MRF brake is operatively interconnected with the third hydraulic motor and define a third set, wherein the fourth MRF brake is operatively interconnected with the fourth hydraulic motor and define a fourth set, wherein the third set and the fourth set are connected in series, and wherein the first set and the second set are collectively connected in parallel with the third set and the fourth set; and

controlling, via a controller, a magnitude of the braking torque using a current applied to the magnetic coil of the at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake,

wherein the controller is configured to control an amount of the current flowing through a magnetic coil of the at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake based on an input,

wherein the current flowing through the magnetic coil of the at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake corresponds with a viscosity of the magneto-rheological fluid of the at least one of the first MRF brake, the second MRF brake, the third MRF brake, or the fourth MRF brake and thus magnitude of the braking torque, and

wherein the input to the controller is selected from a group consisting of a differential pressure between an input side of at least one of the first hydraulic motor, the second hydraulic motor, the third hydraulic motor, or the fourth hydraulic motor and an output side of the at least one of the first hydraulic motor, the second hydraulic motor, the third hydraulic motor, or the fourth hydraulic motor and an operational speed of the at least one of the first hydraulic motor, the second hydraulic motor, the third hydraulic motor, or the fourth hydraulic motor.

12. The method of claim 11 , wherein the directing comprises inputting the hydraulic fluid to the first hydraulic motor and outputting the hydraulic fluid from the first hydraulic motor, wherein a pressure of the hydraulic fluid for the inputting is greater than a pressure of the hydraulic fluid for the outputting.

13. The method of claim 11 , further comprising:

rotating the output of the first hydraulic motor using the directing, wherein the applying comprises applying the braking torque to the output.

14. The method of claim 11 , further comprising:

isolating the hydraulic fluid from the magneto-rheological fluid.

15. The method of claim 11 , wherein the applying comprises:

precluding the magneto-rheological fluid from exiting the first MRF brake and then re-entering the first MRF-brake.