100. the inverter 103 to reset the valves of the valve drive to initial positions.

At S515, the controller 100 resets previous calibration parameters. For example, the controller 100 may reset a variable reflecting calibration parameters for use during the calibration.

At S520, the controller 100 reads viscosity and oil characteristics from a database. For example, the database may be stored in the memory 120. The controller may determine a type of oil in the hydraulic system 1, and read oil characteristics from the database corresponding with the type of oil. The type of oil may be defined (e.g., initially set) according to factory settings. The type of oil may be set and/or changed by a user input. The oil characteristics may include viscosity characteristics, temperature characteristics, etc.

At S525, the controller 100 causes the hydraulic system 1 to initiate a transmission pressure. For example, the controller may cause the inverter 103 to drive the e-machine 105 to cause the hydraulic motor pump to ramp up a hydraulic pressure in the hydraulic system 1.

At S530, the controller determines calibration parameters including a steady state torque, a residual current, and/or a freeze parameter. The controller may determine the calibration parameters based on an adaptive control algorithm. The adaptive control algorithm may correlate the current and torque values measured by the inverter to pressure command and valve states.

At S535, the controller 100 causes the hydraulic system 1 to actuate a next uncharacterized valve of the pump 107.

At S440, the controller 100 records a characteristic current of the other valves not being actuated. This is done to create redundancy in the data collected.

At S545 the controller 100 correlates output parameters against the input parameters. The controller 100 may measure output parameters. For example, the controller 100 may measure a pump speed of the pump 107, an e-machine speed and/or a torque of the e-machine 105, valve states, etc. The output parameters may be correlated to a set of input parameters. For example, the controller 100 may determine what input pressure or valve on/off input caused a variation in the pump speed and/or the torque.

By correlating the output parameters caused by actuation of each valve, the controller 100 may characterize the interdependency of the valves. Characterizing the interdependent valves together with the e-machine 105 may provide a robust and more accurate detection as well as aiding in predicting oil degradation.

At S550, the controller stores calibration data for the various pressure vs. output parameters and a measured current provided to the e-machine 105 from the inverter 101 caused by the actuation of the valve. For example, the controller 100 may store a torque profile and a current profile of the hydraulic system 1 cause by the current pressure of the hydraulic system 1 with the current valve actuated. This calibration data (e.g., the torque profile and current profile) may reflect a primary characterization of independent valve operation.

At S555, the controller determines whether all points (e.g. all possible combinations of valves) have been covered for the current actuated valve. If the controller determines that all points have not been covered for the current actuated valve (No at S555), then the method proceeds to S560.

At S560, the controller causes the hydraulic system to increase the transmission pressure. For example, a step size of pressure may be determined according to a minimum pressure measurable by the hydraulic system 1. The step increase of pressure is used to generate fixed entry data characterization.

The fixed entry data characterization may be used with interpolation to obtain discrete time values. For example, the controller 100 may calculate discrete time values at the start of each step increase in pressure. These values may then be used to calculate the actual pressure gradient between steps (e.g., a rate of change). The method then proceeds to S540 and continues as discussed herein.

Returning to S555, if the controller determines that all points have been covered for the current actuated valve, then the method proceeds to S565.

At S565, the controller 100 determines whether all valves have been covered (e.g., whether all valves have been actuated and calibration data recorded). If the controller 100 determines that all of the valves have not been covered (No at S565), then the method proceeds to S510 and continues as described herein.

If the controller determines that all valves have been covered (Yes at S565), then the method proceeds to S570.

At S570, the controller 100 determines whether a first set of calibration data has been stored for the current calibration. For example, the controller 100 may check the memory 120 for the first set of calibration data. If the controller 100 determines that the first set of calibration data has not been stored (No at S570), then the method proceeds to S575.

At S575, the controller 100 stores the first calibration data in a nonvolatile memory of the memory 120. The first calibration data may be based on the calibration data recorded for each of the valves. The first calibration data may include various pressure vs. output parameters. For example, the first calibration data may include current values of the e-machine 105, torque values of the shaft of the e-machine 105 at the hydraulic pump 107, and/or valve conditions of the valves. For example, data for each step of the valves may be stored as a table and/or as a curve equation based on a computational capacity of the controller 100. The first calibration data may include a torque profile and/or a current profile. The method then proceeds to S515 and continues as described herein.

Returning to S570, if the controller 100 determines that the first set of calibration data has been stored (Yes at S570), then the method proceeds to S580.

At S580, the controller determines whether both of the first calibration data set and a second calibration data set are within a tolerance threshold of each other. For example, the tolerance threshold may be 3%. However, example embodiments are not limited thereto and the tolerance threshold may be greater than or less than 3%. The second calibration data set may be substantially similar to the first calibration data set. Repeated description is therefore omitted. If the first calibration data set and the second calibration data are not within the tolerance threshold of each other (No at S580), then the method proceeds to S585.

At S585, the controller deletes the first calibration data set from the memory 120. The method then proceeds to S505 and continues as discussed herein.

Returning to S580, if the controller determines that the first calibration data set and the second calibration data set are within the tolerance threshold of each other (Yes at S580), then the method proceeds to S590.

At S590, the controller 100 stores the second set of calibration data in the memory 120. Storing the second set of calibration data may be substantially the same as storing the first set of calibration data, described at S575. Repeated description is therefore omitted. The method then proceeds to S430 and continues as discussed herein.

FIG. 6 is a flow chart of a method for determining fluid degradation according to example embodiments.

For example purposes, the example embodiment shown in FIG. 6 will be discussed with regard to the system shown in FIG. 1. In at least this instance, it is understood that the processor 110 executing program code causes the controller 100 to perform the method of FIG. 6. However, example embodiments should not be limited to this example.

Referring to FIG. 6, at S600 the controller 100 determines whether calibration is available. The controller S600 may determine whether calibration is available by checking the memory 120 for the first set of calibration data and the second set of calibration data. If the first set of calibration data and/or the second set of calibration data is not stored in the memory 120, then the controller 100 determines that the calibration is not available (No at S600), and the method proceeds to S430 and continues as described herein.

If the first set of calibration data and the second set of calibration data is stored in the memory 120 (Yes at S600), then the controller 100 determines that the calibration is available and the method proceeds to S605.

At S605, the controller 100 reads a first segment of calibration from the memory 120. For example, the controller 100 may read the first set of calibration data.

At S610, the controller 100 measures the inputs and/or outputs of the hydraulic system 1. Measuring the inputs and/or outputs of the hydraulic system is described above with regard to S510-S565. Repeated description is therefore omitted.

Different from S565, if the controller 100 determines that all valves are covered (Yes at S565), the method proceeds to S615.

At S615, the controller determines whether the measurement is in range. For example, the controller 100 may compare a third set of calibration data to the first set of calibration data stored in the memory 120. The third set of calibration data may correspond with data that has been stored for the measurements performed at S610.

The controller 100 may determine whether the third set of calibration data is within a threshold range of the first set of calibration data. For example, the controller 100 may compare a torque profile and/or a current profile included in the third set of calibration data with a torque profile and/or current profile included in the first set of calibration data. The controller 100 may determine whether the torque profile and/or the calibration profile of the third set of calibration data is within the threshold range of the first set of calibration data.

For example, a slow variation of the calibration data set over time (e.g., months/days) is expected. A threshold of expected change of the calibration data may be set at X %, where X is dependent upon an oil type. A sudden change of the third set of calibration data vs. the first set of calibration data may be determined as leakage. For example, a sudden change may be determined as more than a 2X % change.

If the third set of calibration data is within the threshold range of the first set of calibration data (Yes at S615), the method proceeds to S620.

At S620, the controller 100 determines whether all sections of the hydraulic system 1 are verified. A determination as to whether all sections of the hydraulic system are verified is described with reference to S555 and S565. Repeated description is therefore omitted. If the controller 100 determines that all sections of the hydraulic system 1 are not verified (No at S620), then the method proceeds to S610 and continues as discussed herein.

If the controller 100 determines that all sections of the hydraulic system 1 are verified (Yes at S620), then the method proceeds to S625.

At S625, the controller 100 reports to a user that the hydraulics fluid health is okay. For example, the controller 100 may cause an indicator light to turn on and/or the controller may cause a display to display a notification to the user. The method then proceeds to S430 and continues as discussed herein.

Returning to S615, if the third set of calibration data is not within the threshold range of the first set of calibration data (No at S615), the method proceeds to S630.

At S630, the controller 100 determines whether the third set of calibration data is outside of a degradation threshold. The degradation threshold may be a predetermined (or alternately given) value based on the hydraulic fluid in the hydraulic system 1. For example, the degradation threshold may be stored in the memory 120 associated with the type of hydraulic fluid. The degradation threshold corresponding with various hydraulic fluid types may be stored in the database in the memory 120. For example, the degradation threshold may be calculated by checking the torque profile with respect to the valve positions and calculating the degradation threshold as a percent of the calibration dataset.

If the third set of calibration data is outside the degradation threshold (Yes at S630), then the controller determines that there is a leak in the hydraulic system 1 and the method proceeds to S445 and continues as discussed herein.

If the third set of calibration data is outside the degradation threshold (Yes at S630), then the method proceeds to S635.

At S635, the controller 100 determines whether a degradation threshold is reached. For example, the controller 100 may determine that the degradation threshold is reached when a percent of the torque profile correlation with a respective valve is less than a predetermined (or, alternately, given) percent of the calibration dataset. For example, the percent of the calibration dataset may be 5%. However, example embodiments are not limited thereto and the percent of the calibration dataset may be greater than or less than 5%.

If the degradation is threshold is reached (Yes at S635), then the controller 100 determines that the hydraulic fluid should be replaced and the method proceeds to S425 and continues as discussed herein.

If the degradation threshold is not reached (No at S635), then the controller determines that the hydraulic fluid should not yet be replaced and the method proceeds to S640.

At S640, the controller 100 updates the second set of calibration data. For example, the controller 100 may replace values stored in the second set of calibration data in the nonvolatile memory of the memory 120 with the values stored in the third set of calibration data. The second set of calibration data may be updated periodically to track gradual change in data set measurement. The second data set may be compared to the first data set to determine oil degradation. The method then proceeds to S