FORM 2
THE PATENTS ACT 1970
(39 of 1970)
AND
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rulel3)
1. TITLE OF THE INVENTION:
"HYDRAULIC OIL MONITORING FOR AN OFF-ROAD VEHICLE"
2. APPLICANT:
(a) NAME: KPIT Cummins Infosystems Limited
(b) NATIONALITY: Indian Company incorporated under the
Companies Act, 1956
(c) ADDRESS: 35 & 36 Rajiv Gandhi Infotech Park, Phase 1, MIDC,
Hinjewadi, Pune 411057, Maharashtra, India.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it is to be formed.

FIELD OF INVENTION:
The present invention relates to a control module to monitor the hydraulic oil degradation in the off-road vehicles. More particularly, the present invention relates to the control module in an off-road vehicle, to estimate the degradation in the hydraulic oil properties during running / dynamic condition of the vehicle and generate an oil-change indicator if the oil has been degraded sufficiently.
BACKGROUND AND PRIOR ART:
Hydraulic oil is a fluid which is mainly used for powering hydraulic machinery. Other uses in hydraulic systems are for heat transfer, as a sealing medium, lubricant, for pump efficiency, as a fire resistant etc.
The hydraulic oil have tendency to degrade over the time or due to various other reasons such as extreme change in oil temperature, oil contamination etc., thus it may fail to fully protect the hydraulic machinery once it degrades. Therefore, there arises the need to change the hydraulic oil after recognizing that the oil has degraded sufficiently. Traditionally, the oil is replaced when a vehicle had reached a predetermined mileage or after a specified duration of the vehicle use. There are many systems existing which indicate the degraded condition of oil.
US6327900 calculates the rate of degradation of engine oil which is affected by the extreme change in oil temperature or amounts of contaminants entering in the oil at high load or both. US7043402 discloses a method and an on-line monitoring system for oil degradation, water contamination and fuel dilution for internal combustion engine oils by an electrochemical impedance analysis technique. US4646070 provides an apparatus, for detecting degree of deterioration, which includes a sensor capacitor having capacity varying with dielectric constant of lubricating oil. US4733556 provides an on-board sensor system which compares the dielectric properties of lubricating oil in an internal combustion engine with the dielectric properties of unused oil in a contained volume and provides an output signal indicative of the changes of the viscosity correlated to the dielectric constant.

The present invention attempts to provide a solution for detecting oil degradation condition based on the variation in the oil properties such as oil density, viscosity etc. The present invention discusses an approach to develop a control module to monitor the hydraulic oil degradation online in the vehicle running condition.
SUMMARY OF INVENTION:
The present invention discloses a control module to monitor hydraulic oil degradation online in the off-road vehicles. The hydraulic oil degradation is monitored online, which is while the vehicle is in a running condition or off-line while the vehicle is in off condition. The term 'online monitoring', in the description, hereinafter, refers to the hydraulic oil monitoring while the vehicle is in a running state. It comprises an oil monitoring means employing a pilot spool position method and a pump flow output method to determine the system controlled outputs e.g. pilot spool position and pump flow under the fresh oil condition and degraded oil condition; a fault detection means employing a fault detection mechanism for comparing the difference between the fresh oil system output and the degraded oil system output with a set threshold value; and a transient detect means employing a transient detection mechanism for monitoring the number of transient conditions in the system, wherein oil degradation measured is based on change in physical properties of oil. The control module estimates the hydraulic oil degradation based on hydraulic system dynamics and compares the estimated degradation with a threshold value thereby generating an oil-change indicator.
In an aspect, the present invention focuses on the mathematical computation of the oil degradation based on the hydraulic system dynamics instead of the data driven implements. The hydraulic systems desired outputs, such as pilot spool position and the supply pump flow are mathematically computed. The mathematically computed outputs are then compared with the actual system outputs measured through various sensors. As the oil degrades in the system, the measured outputs differ significantly from the computed system outputs.
BRIEF DESCRIPTION OF DRAWINGS:
Fig. 1 illustrates the system architecture of a typical wheel-loader hydraulic system. Fig. 2 illustrates flowchart for online monitoring system.

Fig. 3 illustrates oil monitoring algorithm implementation.
Fig. 4 illustrates oil monitoring algorithm implementation by a pilot spool position
method.
Fig. 5 illustrates flowchart for fault detection mechanism.
Fig. 6 illustrates fault detection mechanism implementation.
Fig. 7 illustrates flowchart for threshold value determination.
Fig. 8 illustrates model system for problem analysis.
Fig. 9 illustrates spool performance with varying oil properties.
Fig. 10 illustrates results of online monitoring technique the pilot spool position method
for fresh oil condition.
Fig. 11 illustrates results of online monitoring technique a pump flow output method for
fresh oil condition.
Fig. 12 illustrates Change in Viscosity in hydraulic oil.
Fig, 13 illustrates Change in Density in hydraulic oil.
Fig. 14 illustrates Online Monitoring Technique Results by the pilot spool position
method.
Fig. 15 illustrates Threshold Values Changes with Increased Number of Shakes by the
pilot spool position method.
Fig. 16 Online Monitoring Technique Results by a pump flow output method.
Fig. 17 illustrates Threshold Values Changes with Increased Number of Shakes by the
pump flow output method.
DETAILED DESCRIPTION:
The present invention represents an improved approach of the oil life monitoring in terms of the cost effectiveness, the experimental effort reduction and the manual effort reduction. The method of invention focuses on the mathematical computation of the oil quality degradation based on the hydraulic system dynamics instead of the data-driven implementations.
Accordingly, a control module is disclosed herein for online monitoring of hydraulic oil degradation in the off-road vehicles. It comprises an oil monitoring means employing a pilot spool position method and a pump flow output method to determine the system controlled outputs e.g. pilot spool position and pump flow under the fresh oil condition

and degraded oil condition; a fault detection means employing a fault detection mechanism for comparing the difference between the fresh oil system output and the degraded oil system output with a set threshold value; and a transient detect means employing a transient detection mechanism for monitoring the number of transient conditions in the system, wherein oil degradation measured is based on change in physical properties of oil.
The control module of the invention estimates the hydraulic oil degradation based on hydraulic system dynamics and by comparing the estimated degradation with a threshold value thereby generating an oil-change indicator. Oil degradation according the invention is determined based on change in oil properties like oil viscosity, oil density, bulk modulus, etc. The control module of the invention which monitors the oil degradation is integrated into the ECU of the typical hydraulic system known in the art. A typical hydraulic system comprises of a pilot valve assembly, a main valve body, a hydraulic actuator, a hydraulic valve control unit, a main pump, an ECU (electronic control unit), an engine/ECM and at least a sensor.
The method of invention is used to mathematically compute the desired system outputs of the hydraulic system. These system outputs are determined under the fresh oil conditions e.g. oil properties at the normal ambient temperature and no oil contamination or oil aging. The method of invention, which is numerical in its approach, stresses on the computation of the system outputs, which are affected by the oil properties degradation e.g. spool damping effect, spool sticking at the edges of the valve, sluggish response time etc. The hydraulic system desired outputs, such as hydraulic spool position controlled output and the supply pump flow output, are mathematically computed in the fresh oil/fuel conditions. An allowable error margin of ±10% is considered in these mathematical computations with respect to the actual system output. These mathematically computed outputs are then compared with the actual system outputs measured through the physical sensors available in the machine. As the oil/fuel degrades in the actual system the measured system outputs differ significantly from the mathematically computed system outputs.

A fault detection mechanism is implemented to compare the difference in the two system outputs, e.g. with fresh oil & with degraded oil, with a threshold value and confirm the fault upto a calibrated period of time. However, there may be chances of false fault detection caused due to the increased number of transients or noise conditions in the system. For example, the boom shake is one type of the transient. In order to avoid such false fault detection, a 'transient detect mechanism' is implemented. The 'transient detect mechanism' monitors the number of transient conditions in the system and indicates for the modification in the fault detection threshold values if a higher number of the transient conditions or higher noise are detected. The fault detection thresholds are calibrated based on the allowable oil-properties degradation level.
The present invention can be understood by referring to figures which are for exemplary purpose and do not restrict the invention to the embodiments shown.
FIG. 1 is system architecture of a typical wheel-loader hydraulic system. It illustrates a two stage valve assembly of a boom control subsystem which comprises of a Pilot Valve Assembly (5), a Main Valve Body (10), a Hydraulic Valve Control Unit (20), an Engine/ ECM (25) and a Hydraulic Cylinder (30), which as an actuator. The Pilot Valve Assembly (5) includes the pilot spool valves. The Main Valve Body (10) comprises of two main stage spool valves, 10a and 10b. A flow inlet and a flow outlet are provided between the Main Valve Body (10) and the Hydraulic Cylinder (30). The main pump (15) consists of a load sensing pump. The Hydraulic Valve Control Unit (20) comprises of the ECU that controls all the hydraulic functions performed by the vehicle. The control module of the invention, which monitors the oil degradation, is integrated within the ECU of the Hydraulic Valve Control Unit (20) of the off-road vehicle. The Engine/ ECM (25) provides a constant power source to drive the main pump (15).
FIG. 2 illustrates a flowchart for online monitoring according to the method of the invention. The online oil monitoring according to the invention utilizes two methods of monitoring, a pilot spool position method and a pump flow output method, based on the sensor placement for position monitoring of the hydraulic components. The pilot spool position method, referred to as Method-1, is applicable to the hydraulic machinery having a position sensor for the pilot valve assembly and measures the oil degradation based on

the change in oil properties like oil viscosity, oil density, bulk modulus, etc. The pump flow output method, referred to as Method-2, is applicable to the hydraulic machinery having a load pressure sensor and the supply pressure/flow sensor and measures the oil degradation based on change in oil properties like oil density, oil viscosity, bulk modulus, etc. When the position sensor for the pilot valve assembly is present and when pilot valve component is not failed, the pilot spool valve position Xcal is determined mathematically with fresh oil condition. The pilot spool valve position Xact is subsequently stored with the help of the spool position sensor. Further, Xcal and Xact are compared and determined whether the difference between Xcal and Xact is greater than or equal to a threshold value Xthreshoid- Similarly, when the position sensor for main valve assembly, the load pressure sensor and the supply pressure / flow sensor is present and the main component is not failed, the pump flow output Qact, which is a function of supply pressure, is determined. The pump losses are stored Qloss- Further, main valve flow output Qmain is determined mathematically with fresh oil condition and is compared with Qact. Subsequently, it is determined whether the difference between Qact and Qmain is greater than or equal to Ql0SS-Furthermore, it is determined whether both the differences i.e. Xcal - Xact and Qact - Qmain persist for pre-specified time. If this condition is satisfied, then oil change indicator is lit. The need for oil change may be indicated by any know methods in the art; e.g. an alarm, a visual display on a screen, a LED, analogue display, digital display, etc. The implementation of oil monitoring method is shown in FIG. 3, whereas oil monitoring implementation, as perMethod-1 is shown in FIG. 4.
In a preferred embodiment, the oil monitoring method of the invention is utilized for online monitoring i.e. while the vehicle is running, However, the oil monitoring method may also be utilized for offline monitoring i.e. while the vehicle is not running. In a preferred embodiment of the invention, the two methods described above, Method-1 and Method-2 are utilized simultaneously for accurate oil monitoring. However, the two methods maybe utilized independently, based on system requirement. Additionally, it is to be noted that the two methods described based on two different sensor positions are exemplary only. The method of the invention may be utilized for oil monitoring based on any other different sensor positions that can monitor movement of various hydraulic components like accumulator, actuator, etc. without departing from the scope of the invention.

The verification of the stated differences, which is the difference between the fresh oil condition and the degraded oil condition, and the calibration of pre-specified time, is done by implementing the fault detection mechanism. Referring to FIG. 5, if the differences between the calculated values and the actual values are greater than set threshold values, then the fault counter is intialised. Otherwise, the fault counter, and simultaneously timer tmax, started after initialization. If tmax is lapsed and fault count is not greater than the maximum count, then the fault counter is restarted. Otherwise, a fault is detected. The fault detection mechanism implementation is shown in FIG. 6.
The threshold values are determined based on the acceptable range of the oil properties, i.e. viscosity, density & bulk modulus. The threshold values may be set based on specific system requirements. Table 1 shows an exemplary range of oil properties.
Table 1 Acceptable Range of the Oil Properties:

Temp Absolute Viscosity
(Pa.sec) = Kinematic
VtscosiyDensity Density [kg/mA3| Bulk Modulus (Pa) Kinematic Viscosity (mmA2&ec} Absolute Viscosity fcP)
-30 4.04BE-00 1190 1.9Q9E+09 5.85E-05 3400 4046.09 -
-25 2.622E+00 1140 1.900E+O9 4.99E-05 2300 2822.00
20 1.526E+00 1090 1.870E-K39 3.52E-05 1400 1526.00
15 8.320E41 1040 1.840E-HK 2.58E-05 800 832.00
10 5.940E-01 990 1.B10E+09 2.13E-05 600 594.00
5 3.7EOE-01 940 1.7B0E+G9 1.95E4J5 400 378.00
0 2.403E-01 890 1.750E409 1.79E05" 270 240.30
5. 1.74GE-01 870 1.720E-KB 1JB5E-05 200 17400
10 1.190E-01 850 1.690E+09 1.41E-05 140 11900
15- 8.3Q0E-02 830 1.660E-HD9 1.22E-05 100 8303
20 6.480E-02 810 1.630E-KJ9 1.14E-05 60 64.80
25 4.740E-02 790 \SX£MB 9.95E-06 60 4740
30 3.850E-02 770 1.570E+09 9.34E-06 50 3850
40 2.625E-02 750 1.540&09 7.40E-G5 35 26.25
50 1.825E-02 730 1.510E+O9 6.O3E-06 25, 182
SO 1.278E-02 710 1.480E-t09 5.25E-Q6 18 12.78
TO B.970E-O3 690 U50E+03 4.82E-05 13 837
80 6.700E-C3 670 1.420E+09 4.2BE436 10 670
90 5.200E-O3 650 13BQ9 3.97E-Q6 8 5.33
99 3.780E-03 630 1.360E*09 3.5BE-05 6 378
For example, the oil properties in the temperature range 0-70 may be acceptable.
However, in the condition of the high number of transients, there are high chances of the false failure detection. To avoid such a false failure detection, a 'transient detect

mechanism' is implemented. The transient detect mechanism detects the number of the transient conditions and noise. These transient conditions are the sharp rise or fall of the pilot position in the Method-1 and the sharp rise & fall of the flow output in the Method-2. At the increased number of the transient conditions and/or noise, the threshold values are raised.
Determination of the threshold values is illustrated in FIG. 7. Referring to FIG. 7, the transient count and transient flag are initialized. The threshold value is set for Method-1. Further, the transient condition for pilot spool position is detected and the count is incremented. If the transient count is greater than a calibrated value, then the transient condition is identified and second threshold value is set for Method-1. This threshold value is preferably greater than previous one. If timer tmax is lapsed, then steps from initializing transient flag are repeated.
Examples:
A system for problem analysis, as illustrated in FIG, 8, is modeled to demonstrate
technical issue. The hydraulic control model is developed using the LMS.imagine
AMESim graphical modeling tool. The hydraulic valve displacement control performance
is analyzed at the various oil properties. The model analysis results are obtained under
three cases of the spool position controlled, namely
(i) when oil viscosity is kept high at around 3000 mm2/sec i.e. thick oil shows degraded
oil condition.
(ii) when oil viscosity is kept low at around 5 mm2/sec i.e. thin oil shows degraded oil,
and
(iii) when oil viscosity is kept normal at around 300 mm2/sec shows fresh oil condition.
It is observed that as oil becomes thick, the spool response time increases & the higher viscous damping force resists the closing of the spool. Further, as oil becomes thin, the spool settling becomes unsteady and it starts oscillating around its steady state position. FIG. 9 illustrates the results of above analysis.
The above stated analysis is followed by three test cases, which are mentioned hereafter.

Test case 1:
The hydraulic oil under test is fresh i.e. with no contamination. It is observed that the oil degradation estimated by Method-1 is zero. Further, the oil fault counter value remains to its initialized value, the oil fault counter start/stop status remains zero and the oil fault flag is found to be zero. The observations are shown in FIG. 10. Thus, the method-1 is verified at fresh oil condition.
Test case 2:
Again the oil under test is fresh. Applying Method-2, the estimated oil degradation is
found to be under acceptable limits. Further, the oil fault counter value remains to its
initialized value, the oil fault counter start/stop status remains zero and the oil fault flag is
zero. The observations are shown in FIG. 11. Thus, the Method-2 is verified at fresh oil
condition.
Test case 3:
In this experiment, the hydraulic oil properties are changed considerably. The hydraulic oil/fuel viscosity is changed from -20 cP to -1550 cP (outside the acceptable range as shown in Tablel) and the hydraulic oil/fuel density is changed from -734 kg/m3 to -1100 kg/m3 (outside the acceptable range as shown in Table 1).. These changes are shown in FIG. 12-13. Here, Method-1 as well as Method-2 is implemented.
(i) The estimated oil properties degradation is determined in percentage and
compared with a percentage threshold value, (ii) In the monitoring algorithm, the threshold value is increased if the boom
shakes are greater than a calibrated value, (iii) The oil fault counter value increments whenever the oil fault counter status is
'start' and stops incrementing at the 'stop' status, (iv) The oil fault counter start/stop status is as shown. (v) The oil fault flag is one as the oil fault counter value exceeds the threshold
limit of 6000 counts, (vi) The oil fault count is latched once detected
(vii) The boom shake flag is reset after the fault detection window lapses and the threshold value is set to its previously low value.

Online monitoring technique results for Method-1 and Method-2 are depicted in FIG. 14 and FIG 16, respectively. Threshold values changes with increased number of shakes (transients) for Method-1 and Method-2 are depicted in FIG. 15 and FIG. 17, respectively.
The advantages of present invention are reduced cost and less experimental and manual effort. The present invention is integrated with the main ECU of the hydraulic system and is used to monitor the oil degradation under all the operating and non-operating conditions of the vehicle.
Additionally, the method of invention does not include any hardware related cost. It does not include any data driven implementation. Hence, the method of the invention significantly reduces the experimental efforts. As there are no physical sensors available for the direct measurement of the oil quality, the "online monitoring technique' is extremely useful in monitoring the current condition of the oil in less time and effort.
The method of invention is implemented by using two-methods, which broadens the applicability of this technique for the various sensors availability & the position arrangements in the hydraulic system of an off road vehicle. It is to be noted that the two methods described maybe used simultaneously or independently, as per the system requirements. Additionally, the method of the invention may be utilized for oil monitoring based on any other different sensor positions that can monitor movements of various hydraulic components like accumulator, actuator, etc. The oil monitoring method of the invention may be utilized for online monitoring .i.e. while the vehicle is running and offline monitoring .i.e. while the vehicle is not running. The exemplary methods described will serve to illustrate the practice of this invention being understood that the particular shown by way of example are for illustrative purposes only and are not limiting the scope of the invention in any manner.

We claim,
1. A control module for monitoring hydraulic oil degradation in the off-road vehicles
comprising:
an oil monitoring means employing a pilot spool position method and a pump
flow output method to determine the system controlled outputs under the fresh oil
condition and degraded oil condition;
a fault detection means employing a fault detection mechanism for comparing the
difference between the fresh oil system output and the degraded oil system output
with a set threshold value; and
a transient detect means employing a transient detection mechanism for
monitoring the number of transient conditions in the system,
wherein oil degradation measured is based on change in physical properties of oil.
2. The control module for monitoring hydraulic oil degradation according to Claim
1; wherein said pilot spool position method for estimating hydraulic oil
degradation comprises
(i) determining pilot spool position Xcal with fresh oil conditions;
(ii) storing pilot spool position sensor feedback Xact;
(iii) comparing pilot spool positions in Xcal and Xact using a fault detection
mechanism; and (iv) verifying whether difference between.a calculated pilot spool position and
an actual pilot spool position greater than a threshold Xthreshow using a fault
detection mechanism.
3. The control module for monitoring hydraulic oil degradation according to Claim
1, wherein said pump flow output method for estimating hydraulic oil degradation
comprises
(i) determining pumpflow output Qact; (ii) storing pump losses Qloss;
(iii) determining main valve flow output Qmain with fresh oil conditions; and (iv) verify whether difference between pumpflow output Qact and Qmain is greater than or equal to threshold Ql0SS using a fault detection mechanism.

4. The control module for monitoring hydraulic oil degradation according to Claim 1 & 2, wherein said pilot spool position method for estimating hydraulic oil degradation is applicable to hydraulic machinery having a position sensor for the pilot valve assembly.
5. The control module for monitoring hydraulic oil degradation according to Claim 1 & 3, wherein said pump flow output method for estimating hydraulic oil degradation is applicable to hydraulic machinery having a load pressure sensor and the supply pressure/flow sensor.
6. The control module for monitoring hydraulic oil degradation according to Claim 1; wherein said fault detection mechanism comprises
(i) verifying whether difference between Xcal and Xact is greater than Xthreshoid;
(ii) initializing fault counter if (i) is satisfied else following step (iv);
(iii) starting fault counter and timer tmax
(iv) stopping of fault counter;
(v) verifying whether fault counter is greater than maximum count; and
(vi) indicating the occurring of the fault if (iv) is satisfied else restarting of fault
counter.
7. The control module for monitoring hydraulic oil degradation according to Claim
1; wherein said threshold value is determined using steps
(i) initializing transient flag and transient count;
(ii) setting threshold-1 for said pilot spool position method;
(iii) detecting transient condition for pilot spool position;
(iv) verifying whether transient count is greater than a calibrated value; and
(v) setting threshold-2 for method-1 if step (iv) is satisfied.
8. The control module for monitoring hydraulic oil degradation according to claim 1,
wherein the transient detection mechanism indicates for modification in the fault
detection threshold values if a higher number of the transient conditions or noises
are detected.

9. The control module for monitoring hydraulic oil degradation according to claim 1, wherein said oil monitoring means comprises of a pilot valve assembly including plurality of pilot spool valves, a main valve body including plurality of main stage spool valves, a main pump including a load-sensing pump, and plurality of sensors including spool position sensor & load pressure sensor.
10. The control module for monitoring hydraulic oil degradation according to Claim 1, wherein said pilot spool position method and said pump flow output method for estimating hydraulic oil degradation are utilized simultaneously or independently.
11. The control module for monitoring hydraulic oil degradation according to any of the preceding claim is utilized either for online monitoring of oil degradation or offline monitoring of oil degradation.