System and method for assigning a service life estimate of a hydraulic cylinder

Abstract

A system for monitoring a hydraulic cylinder in a work machine is disclosed. The system calculates a normalized seal damage for the hydraulic cylinder based on a normalized wear coefficient. An estimated degradation rate is determined from normalized seal damage calculations performed over a timestep during operation of the work machine, and the estimated degradation rate is compared to a degradation model formed from population hydraulic cylinder data. A service life estimate of a seal of the hydraulic cylinder is identified based on the alignment of the estimated degradation rate within the degradation model.

What is claimed is: 
     
         1 . A work machine having a system for monitoring a hydraulic cylinder in the work machine, the work machine comprising:
 a frame;   a boom movably attached to the frame;   an engine mounted on the frame;   an undercarriage supporting the frame;   an implement movably attached to the boom;   a hydraulic cylinder operatively associated with the boom and including a cylinder barrel, a piston moveably disposed in the cylinder barrel, a seal provided with the hydraulic cylinder, and a pressure sensor configured to monitor a pressure of a fluid in the hydraulic cylinder; and   an electronic control unit, the electronic control unit in communication with the pressure sensor, the electronic control unit programed to:   receive pressure signals from the pressure sensor,   determine a piston displacement of the piston,   calculate a normalized seal damage based on the received pressure signals, the determined piston displacement, and a normalized wear coefficient,   determine an estimated degradation rate of the seal from the calculated normalized seal damage,   compare the estimated degradation rate to a degradation model, and   identify a service life estimate to the seal based on the alignment of the estimated degradation rate within the degradation model.   
     
     
         2 . The work machine of  claim 1 , in which the normalized wear coefficient is calculated from merged population data of population hydraulic cylinders of the same cylinder type as the hydraulic cylinder. 
     
     
         3 . The work machine of  claim 2 , in which the degradation model is constructed by calculating a normalized population seal damage of at least two population hydraulic cylinders of the same cylinder type as the hydraulic cylinder, compiling normalized population seal damage data over a timestep that includes at least two normalized population seal damage calculations for each population hydraulic cylinder, and calculating the population degradation rate for each population hydraulic cylinder for the timestep from the compiled data. 
     
     
         4 . The work machine of  claim 3 , in which constructing the degradation model further includes bucketizing the calculated population degradation rates into ranges of machine operation hours. 
     
     
         5 . The work machine of  claim 4 , in which the identification of the service life estimate to the seal is based on the alignment of the estimated degradation rate within a bucket of the degradation model. 
     
     
         6 . The work machine of  claim 1 , in which prior to calculating the normalized seal damage, the electronic control unit enables a service life estimate based on one or more of a preset range of the cylinder displacement, cylinder pressure, oil temperature, and operator commands. 
     
     
         7 . The work machine of  claim 1 , in which after the service life estimate is identified, the electronic control unit configured to display the assigned service life estimate on an external display. 
     
     
         8 . The work machine of  claim 1 , in which the hydraulic cylinder further includes a displacement sensor in the hydraulic cylinder that sends displacement signals to the electronic control unit for use in determining the piston displacement. 
     
     
         9 . The work machine of  claim 1 , in which the electronic control unit makes an estimate of the piston travel distance for the determined piston displacement. 
     
     
         10 . The work machine of  claim 1 , in which the degradation rate is calculated at the end of a predetermined timestep, and the degradation rate includes multiple calculations of the normalized seal damage calculated during the timestep. 
     
     
         11 . The work machine of  claim 10 , in which the timestep is between 50 and 100 hours of operating the work machine. 
     
     
         12 . The work machine of  claim 1 , in which the service life estimate is a range of work machine operation hours that the seal is estimated to need to be replaced at. 
     
     
         13 . The work machine of  claim 1 , in which the normalized seal damage is calculated from merged population data of population hydraulic cylinders of the same hydraulic cylinder type, and the merged population data includes mean pressure data and mean piston displacement data collected from the population hydraulic cylinders. 
     
     
         14 . A system for identifying a service life estimate to a seal of a hydraulic cylinder of a work machine, the system comprising:
 a degradation model constructed by periodically calculating a normalized population seal damage of a population of hydraulic cylinders of the same cylinder type as the hydraulic cylinder of the work machine, and periodically determining the population degradation rate for the population of hydraulic cylinders based on the normalized population seal damage calculations;   the hydraulic cylinder for the work machine including a cylinder barrel, a piston moveably disposed in the cylinder barrel, a seal provided with the hydraulic cylinder, and a pressure sensor configured to monitor a pressure of a fluid in the hydraulic cylinder; and   an electronic control unit, the electronic control unit in communication with the pressure sensor, the electronic control unit configured to receive pressure signals from the pressure sensor, determine a piston displacement of the hydraulic cylinder for the work machine, calculate a normalized work machine seal damage based on the received pressure signals, the determined piston displacement, and a normalized wear coefficient, determine an estimated degradation rate of the seal from the calculated normalized seal damage, compare the estimated degradation rate to the degradation model, and identify the service life estimate to the seal based on the alignment of the estimated degradation rate within the degradation model.   
     
     
         15 . The system of  claim 14 , in which the hydraulic cylinder for the work machine is part of a hydraulic circuit of the work machine that includes multiple hydraulic cylinders. 
     
     
         16 . The system of  claim 15 , in which each hydraulic cylinder in the hydraulic circuit includes at least two seals, and the system identifies a service life estimate for each seal in the hydraulic circuit. 
     
     
         17 . A method of assigning a service life estimate to a seal of a hydraulic cylinder of a work machine, the method including:
 constructing a degradation model by periodically calculating a normalized population seal damage of population hydraulic cylinders of the same cylinder type as the hydraulic cylinder of the work machine, determining the estimated population degradation rate of the population hydraulic cylinders based on the normalized population seal damage calculations, and bucketizing the estimated population degradation rates;   periodically calculating a normalized work machine seal damage during operation of the work machine based on received pressure signals as they are received from at least one pressure sensor on the hydraulic cylinder, a piston displacement of a piston of the hydraulic cylinder as it is determined by an electronic control unit of the work machine, and a normalized wear coefficient;   determine an estimated degradation rate of the seal based on the periodic normalized work machine seal damage calculations; and   identify a service life estimate to the seal based on the alignment of the estimated degradation rate within the bucketized population degradation rates.   
     
     
         18 . The method of  claim 17 , in which the normalized population seal damage calculation is calculated based on pressure measurements of the population hydraulic cylinders, piston displacement of the population hydraulic cylinders, and the normalized wear coefficient. 
     
     
         19 . The method of  claim 18 , in which the normalized wear coefficient is calculated from the mean merged pressure measurements and mean piston displacement of the population hydraulic cylinders. 
     
     
         20 . The method of  claim 17 , in which prior to calculating the normalized seal damage during operation of the work machine, the electronic control unit determines the work machine is in an operating mode.