Hydraulic accumulator pre-charge pressure detection

Abstract

A system including a hydraulic accumulator, a pressure sensor, a fluid source and a data processor to detect a pre-charge pressure is provided. The hydraulic accumulator includes first and second fluid chambers and a separator therebetween. The hydraulic accumulator has an associated pre-charge pressure. The pressure sensor is connected to the first fluid chamber. The data processor is connected to the pressure sensor. The data processor is configured to determine a first and second rate of pressure changes, and a transition pressure between the first and second rates. The approximate pre-charge pressure is determined based on the transition pressure.

What is claimed is: 
     
         1 . A system comprising:
 a hydraulic accumulator capable of a minimum volume state and a maximum volume state, and an associated pre-charge pressure;   a fluid pressure sensor coupled to the hydraulic accumulator;   a fluid source coupled to the hydraulic accumulator; and   a data processor connected to the fluid pressure sensor, configured to:
 reduce to the hydraulic accumulator to the minimum volume state; 
 charge the hydraulic accumulator with a pressurized fluid; 
 in response to the charge of the hydraulic accumulator, determine a first transition between a first rate of pressure change and a second rate of pressure; 
 determine an approximate pre-charge pressure of the hydraulic accumulator based on the first transition pressure; 
 compare the approximate pre-charge pressure with a threshold; and 
 if the approximate pre-charge pressure is outside a threshold range, provide notification via at least one of visual and audio feedback. 
   
     
     
         2 . The system of  claim 1 , wherein the fluid pressure sensor is configured to provide a fluid pressure reading of the hydraulic accumulator to the data processor. 
     
     
         3 . The system of  claim 1 , wherein the approximate pre-charge pressure is the difference of a fluid pressure of the hydraulic accumulator between the minimum volume state and the first transition pressure. 
     
     
         4 . The system of  claim 1 , wherein the data processor is further configured to monitor a rate of pressure change with respect to time of the fluid of the hydraulic accumulator and to determine frictional forces associated with a separator of the hydraulic accumulator. 
     
     
         5 . The system of  claim 4 , wherein the hydraulic accumulator is a piston-based accumulator and the separator is a piston having one or more seals. 
     
     
         6 . The system of  claim 4 , wherein the hydraulic accumulator is a bladder-based accumulator and the separator is a flexible membrane. 
     
     
         7 . The system of  claim 1 , wherein the data processor is configured to:
 determine a peak pressure after the charge of the hydraulic accumulator;   compare the approximate pre-charge pressure with the peak pressure; and   determine a dynamic response of the hydraulic accumulator based on the difference between the peak pressure and the approximate pre-charge pressure.   
     
     
         8 . The system of  claim 1 , wherein the data processor is configured to:
 in response to a discharge of the hydraulic accumulator after the charge of the hydraulic accumulator, determine a second transition pressure between a third rate of pressure change and a fourth rate of pressure;   determine an approximate pre-charge pressure of the hydraulic accumulator based on the first transition pressure and the second transition pressure;   compare the approximate pre-charge pressure based on the first transition pressure and the second transition pressure with a threshold; and   if the approximate pre-charge pressure based on the first transition pressure and the second transition pressure is outside a threshold range, provide notification via at least one of visual and audio feedback.   
     
     
         9 . The system of  claim 1 , wherein the data processor is configured to store the determined approximate pre-charge pressure of the hydraulic accumulator in a database. 
     
     
         10 . The method of  claim 9 , wherein the data processor is configured to determining a change in pre-charge pressure of the hydraulic accumulator based on a comparison between a monitored pre-charge pressure and a previously stored pre-charge pressure. 
     
     
         11 . A method comprising:
 withdrawing fluid from a hydraulic accumulator such that the hydraulic accumulator is in a minimum volume state;   providing a pressurized fluid to the hydraulic accumulator, wherein a fluid pressure of the hydraulic accumulator has a first transition pressure between a first rate of pressure change and a second rate of pressure;   determining an approximate pre-charge pressure of the hydraulic accumulator based on the first transition pressure;   comparing the approximate pre-charge pressure with a threshold; and   providing notification via at least one of visual and audio feedback when the approximate pre-charge pressure is outside a threshold range.   
     
     
         12 . The method of  claim 11  further comprising receiving a fluid pressure reading from a pressure sensor associated with the hydraulic accumulator. 
     
     
         13 . The method of  claim 12 , wherein the determining an approximate pre-charge pressure step includes determining the difference of a fluid pressure of the hydraulic accumulator between the minimum volume state and the first transition pressure. 
     
     
         14 . The method of  claim 11 , further including:
 determining a peak pressure after the providing a pressurized fluid to the hydraulic step;   comparing the approximate pre-charge pressure with the peak pressure; and   determining a dynamic response of the hydraulic accumulator based on the difference between the peak pressure and the approximate pre-charge pressure.   
     
     
         15 . The method of  claim 11 , further including:
 discharging fluid from the hydraulic accumulator after the providing a pressurized fluid to the hydraulic step,   determining a second transition pressure between a third rate of pressure change and a fourth rate of pressure during the discharging fluid step; and   determining an approximate pre-charge pressure of the hydraulic accumulator based on the first transition pressure and the second transition pressure.   
     
     
         16 . The method of  claim 15 , wherein the determining an approximate pre-charge pressure of the hydraulic accumulator based on the first transition pressure and the second transition pressure step includes calculating an average of the first and second transition pressures. 
     
     
         17 . The method of  claim 11 , further including monitoring a rate of pressure change with respect to time of the fluid of the hydraulic accumulator, and determining frictional forces associated with a separator of the hydraulic accumulator 
     
     
         18 . The method of  claim 11 , further including storing the determined approximate pre-charge pressure of the hydraulic accumulator in a database. 
     
     
         19 . The method of  claim 18 , determining a change in pre-charge pressure of the hydraulic accumulator based on comparing a monitored pre-charge pressure to a previously stored pre-charge pressure. 
     
     
         20 . A system comprising:
 a hydraulic accumulator capable of a minimum volume state and a maximum volume state, and an associated pre-charge pressure;   a fluid pressure sensor coupled to the hydraulic accumulator;   a fluid source coupled to the hydraulic accumulator; and   a data processor connected to the fluid pressure sensor, configured to:
 reduce to the hydraulic accumulator to the minimum volume state; 
 charge the hydraulic accumulator with a pressurized fluid; 
 in response to the charge of the hydraulic accumulator, determine a first transition between a first rate of pressure change and a second rate of pressure; 
 determine an approximate pre-charge pressure of the hydraulic accumulator based on the first transition pressure; 
 store the determined approximate pre-charge pressure of the hydraulic accumulator in a database; 
 determine a change in pre-charge pressure of the hydraulic accumulator based on a comparison between a monitored pre-charge pressure and a previously stored pre-charge pressure; and 
 provide notification via at least one of visual and audio feedback when the pre-charge pressure change is outside a threshold.