Hydraulic power system and method for controlling same

1. A method for controlling operation of a hydraulic power system coupled to a torque wrench, the hydraulic power system including a motor, a valve, and a controller, the method comprising:

defining a user set pressure;

advancing a fluid actuator of the torque wrench toward the user set pressure, the torque wrench applying torque to a work piece;

calculating a change in pressure per unit time during an initial advance operation of the fluid actuator below the user set pressure;

storing the calculated change in pressure per unit time as a reference pressure slope;

during a subsequent advance of the fluid actuator, measuring a change in pressure of fluid in the fluid actuator of the torque wrench;

comparing the measured change in pressure per unit time to the reference pressure slope; and

retracting the fluid actuator of the torque wrench when the change in pressure is greater than the stored pressure slope.

2. The method of claim 1 , further comprising detecting a first inflection interval at which a change in pressure per unit time transitions from a value that is greater than the reference pressure slope to a value that is less than the reference pressure slope.

3. The method of claim 2 , wherein the reference pressure slope is a first reference pressure slope, the method further comprising detecting a second inflection interval at which a change in pressure per unit time transitions from a value that is less than a second reference pressure slope to a value that is greater than the first reference pressure slope.

4. The method of claim 3 , wherein detecting the second inflection interval is performed following a predetermined amount of time following the first inflection interval and wherein the change in pressure per unit time exceeds a predetermined threshold.

5. The method of claim 3 , further comprising,

retracting the torque wrench when the change in pressure is less than the reference pressure slope; and

initiating an auto-complete cycle by advancing and retracting the torque wrench once more.

6. The method of claim 5 , further comprising, prior to initiating the auto-complete cycle, determining whether at least one of the following conditions is satisfied for initiating the auto-complete cycle:

a first condition in which, after the second inflection interval is detected, a difference between a measured pressure and a user-specified pressure is below a predetermined threshold, and the measured change in pressure per unit time is less than the second reference pressure slope; and

a second condition in which, after the first inflection interval is detected, a difference between a measured pressure and a user-specified pressure is below a predetermined threshold, and a pressure measured while retracting the fluid actuator from a point at which the change in pressure is greater than the stored pressure slope is approximately equal to the user-specified pressure.

7. The method of claim 1 , further comprising,

starting a cycle in response to receiving an actuation at a first button;

prior to the advancing step, receiving an actuation at a second button of the controller;

adjusting a relief valve to a maximum set pressure;

receiving an actuation at the first button;

outputting at least one of a light output and a haptic pulse from the controller; and

detecting a release of the first button and the second button.

8. The method of claim 7 , further comprising

Subsequent the detecting step, receiving an actuation at the second button and a third button; and

clearing the user set pressure.

9. The method of claim 7 , further comprising,

comparing a pressure of the torque wrench to the maximum set pressure; and

retracting the torque wrench when the pressure of the torque wrench is less than the maximum set pressure.

10. The method of claim 7 , further comprising,

retracting the torque wrench when a pressure of the torque wrench is less than the maximum set pressure and when the pressure approaches the maximum set pressure at a slope less than the reference pressure slope; and

starting an auto-complete cycle by advancing and retracting the torque wrench once more.

11. The method of claim 1 , wherein the reference pressure slope is a first reference pressure slope, the method further comprising,

calculating a second reference pressure slope based on the user set pressure, the first reference pressure slope greater than the second reference pressure slope.

12. The method of claim 11 , wherein advancing the torque wrench to the user set pressure occurs during an initial advancing step.

13. The method of claim 12 , wherein the torque wrench is applying torque to a work piece during the initial advance step.

14. The method of claim 11 , further comprising,

determining the location of a first inflection interval at which a change in pressure changes from greater than the first pressure reference slope to less than the first pressure reference slope;

determining the location of a second inflection interval at which the change in pressure changes from less than the second reference pressure slope to greater than the first pressure reference slope; and

wherein the retracting step occurs subsequent to determining the location of the second inflection interval.

15. The method of claim 1 , further comprising,

detecting actuation of one of a first button and a second button;

when actuation at the first button is detected, subsequently detecting a release of the first button, and starting an auto-cycle to automatically control the advancing and retracting steps;

when actuation at the second button is detected, starting a manual cycle to manually control the advancing and retracting steps.

16. The method of claim 15 , further comprising outputting at least one of light or vibrations from the controller to alert a user to release the second button and retract the fluid actuator in the manual cycle.

17. The method of claim 1 , further comprising detecting whether a stick-slip condition has occurred.

18. The method of claim 1 , further comprising

detecting the presence of an abnormal power supply, and when an abnormal power supply is detected, adjusting voltage operating limits of the hydraulic power system.