Electronic control for a rotary fluid device

Abstract

A fluid system is provided including a fluid pump having an output and an electric motor coupled to the fluid pump. The electric motor is adapted to operate the fluid pump in response to an electrical signal. A controller adapted to communicate the electrical signal to the electric motor, the controller including an initial lookup table having initial performance data related to the fluid pump and the electric motor. The initial performance data from the initial lookup table and sensed performance data applied to a modifiable lookup table are used by the controller to set aspects of the electrical signal communicated to the electric motor to achieve a desired system pressure generated by the fluid pump. A pressure sensor in communication with the output that is adapted to communicate a sensed system pressure to the controller, the controller being adapted to update the modifiable lookup table based on a difference between the desired system pressure and the sensed system pressure to minimize variation between the sensed system pressure and the desired system pressure.

What is claimed is: 
     
         1 . A fluid system comprising:
 a fluid pump having an output:   an electric motor coupled to the fluid pump, the electric motor being adapted to operate the fluid pump in response to an electrical signal;   a controller adapted to communicate the electrical signal to the electric motor, the controller including an initial lookup table having initial performance data related to the fluid pump and the electric motor, wherein the initial performance data from the initial lookup table and sensed performance data applied to a modifiable lookup table are used by the controller to set aspects of the electrical signal communicated to the electric motor to achieve a desired system pressure generated by the fluid pump; and   a pressure sensor in communication with the output that is adapted to communicate a sensed system pressure to the controller, the controller being adapted to update the modifiable lookup table based on a difference between the desired system pressure and the sensed system pressure to minimize variation between the sensed system pressure and the desired system pressure.   
     
     
         2 . The fluid system of  claim 1 , wherein the initial lookup table establishes a relationship between motor current, motor speed, and the desired system pressure. 
     
     
         3 . The fluid system of  claim 1 , further comprising a motor speed sensor for communicating a sensed motor speed to the controller, wherein the electrical signal includes a motor current command, and wherein the controller determines a value of the motor current command for achieving the desired system pressure. 
     
     
         4 . The fluid system of  claim 1 , further comprising a temperature sensor for sensing a hydraulic fluid temperature of hydraulic fluid passing through the fluid pump, wherein the controller includes a plurality of initial lookup tables and plurality of modifiable lookup tables corresponding to different hydraulic fluid temperatures, and wherein the controller selects an appropriate modifiable lookup table from the plurality of updatable lookup tables based on the hydraulic fluid temperature sensed by the temperature sensor. 
     
     
         5 . The fluid system of  claim 4 , wherein the controller is configured to monitor the sensed motor speed over time to determine whether an acceleration condition exists, and wherein the controller is configured to modify the motor current command when the acceleration condition exits. 
     
     
         6 . The fluid system of  claim 5 , wherein the controller adjusts a magnitude of the motor current command based on a calculation to maintain the desired system pressure when the acceleration condition is detected. 
     
     
         7 . The fluid system of  claim 1 , further comprising a current sensor for sensing a sensed current provided to the motor, wherein the controller is configured to compare the sensed current with a desired current corresponding to a value of the motor current command, wherein the comparison between the sensed current and the desired current results in a motor control signal, and wherein the controller modifies the motor control signal to compensate for variations between the sensed current and the desired current. 
     
     
         8 . The fluid system of  claim 1 , wherein initial data corresponding to the initial lookup table is stored in a memory module of the controller. 
     
     
         9 . The fluid system of  claim 1 , wherein a recalibration routine is used to update the modifiable lookup table based on the sensed system pressure sensed while the fluid system is operating at steady state. 
     
     
         10 . The fluid system of  claim 1 , wherein the controller is configured to perform a recalibration routine to update the modifiable table, wherein the recalibration routine comprises:
 receiving sensed performance data from a sensor;   retrieving initial performance data related to the fluid pump and the electric motor from the initial lookup table;   storing the sensed performance data and the initial performance data in the modified lookup table;   in response to a sensed measurement from the pressure sensor, comparing the sensed performance data and the initial performance data to determine a correlation between the sensed performance data, the initial performance data and the desired system pressure;   generating an updated version of the modifiable lookup table; and   using the updated version of the modifiable lookup table to send a motor current command signal to the controller.   
     
     
         11 . The fluid system of  claim 10 , wherein determining a correlation between the sensed performance data, the initial performance data, and the desired system pressure comprises calculating a least squares error of an operating point between sensed performance data and the initial performance data. 
     
     
         12 . The fluid system of  claim 11 , wherein generating an updated version of the modifiable lookup table is based on maintaining the desired system pressure. 
     
     
         13 . The fluid system of  claim 12 , wherein generating an updated version of the modifiable lookup table further comprises reducing the least squares error of the operating point between the sensed performance data and the initial performance data. 
     
     
         14 . The fluid system of  claim 11 , wherein the controller is further configured to determine remaining life of a component of the fluid system, wherein determining the remaining life comprises comparing the correlation between the sensed performance data and the initial performance data to at least one threshold over a time period. 
     
     
         15 . The fluid system of  claim 1 , wherein the fluid pump is one of a plurality of fluid pumps, wherein each one of the plurality of fluid pumps is coupled to a motor, wherein the fluid system includes a junction location for combining fluid output flow from the fluid pumps, and wherein the pressure sensor is positioned at or downstream of the junction location and wherein each motor is controlled by the controller. 
     
     
         16 . The fluid system of  claim 15 , wherein the controller is further configured with a plurality sub-controllers to individually control each electric motor and wherein the controller establishes a communication link between the plurality of sub-controllers. 
     
     
         17 . The fluid system of  claim 15 , wherein check valves are positioned between each pump in the plurality of pumps and the junction location. 
     
     
         18 . The fluid system of  claim 15 , wherein the controller operates an individual pump or a combination of fluid pumps depending upon a demand placed on the fluid system. 
     
     
         19 . The fluid system of  claim 17 , wherein the fluid pump is one of a plurality of fluid pumps incorporated into a power pack controlled by the controller, wherein the power pack includes a power pack outlet that receives a total flow provided by the fluid pumps. 
     
     
         20 . The fluid system of  claim 19 , wherein check valves are provided between the fluid pumps and the power pack outlet, wherein the total flow passes through a power pack outlet filter, and wherein the pressure sensor is positioned downstream from the power pack outlet filter. 
     
     
         21 . The fluid system of  claim 15 , wherein the controller is configured to recalibrate the modifiable lookup table of an individual pump in the plurality of pumps, wherein the individual pump is powered during the fluid system operation with remaining pumps in the plurality of pumps unpowered. 
     
     
         22 . The fluid system of  claim 21 , wherein the controller is configured to recalibrate the modifiable lookup table of the individual pump in the plurality of pumps, wherein the individual pump that is powered is alternated. 
     
     
         23 . The fluid system of  claim 20 , wherein the controller is configured to recalibrate the modifiable lookup table of the individual pump in the plurality of pumps, wherein the individual pump in the plurality of pumps is operated at a desired system pressure and remaining pumps in the plurality of pumps are operated at a pressure lower than the desired system pressure, wherein output of the remaining pumps is blocked by the attached check valves. 
     
     
         24 . The fluid system of  claim 23 , wherein the controller is configured to recalibrate the modifiable lookup table of the individual pump in the plurality of pumps, wherein the individual pump that operates at the desired system pressure is alternated. 
     
     
         25 . The fluid system of  claim 10 , wherein the controller is configured to monitor the correlation, wherein when the correlation exceeds the threshold, a responsive action is triggered, wherein the responsive action comprises the fluid system reverting to operate based on initial performance data from an initial lookup table. 
     
     
         26 . The fluid system of  claim 15 , wherein the controller is configured to determine the pressure sensor functionality, wherein determine the pressure sensor functionality comprises:
 sensing a first pressure measurement while a first individual pump in the plurality of pumps is producing an output flow and remainder pumps in the plurality of pumps are not producing a flow output;   determining whether the first pressure measurement is an anomaly based on a predetermined threshold for system pressure;   in response to determining that the first pressure measurement is an anomaly, sensing a second pressure measurement wherein the second pressure measurement is based on alternating the first individual pump to a no flow output state and producing the flow output from a second individual pump from the remainder pumps; and   determining whether the second pressure measurement is an anomaly based on the predetermined threshold for system pressure.   
     
     
         27 . The fluid system of  claim 26 , wherein the controller is configured to determine the pressure sensor functionality, wherein determine the pressure sensor functionality further comprises, in response to determining that the second pressure measurement is an anomaly, performing a responsive action on the pressure sensor. 
     
     
         28 . The fluid system of  claim 26 , wherein the controller is configured to determine the pressure sensor functionality, wherein determine the pressure sensor functionality further comprises, in response to determining that the second pressure measurement is not an anomaly, performing a responsive action on the first individual pump. 
     
     
         29 . The fluid system of  claim 4 , wherein determine whether an acceleration condition exists comprises sensing at least one of: a change flow demand in the system and a decrease in pressure in the system. 
     
     
         30 . The fluid system of  claim 1 , wherein the controller samples the measured pressure from the pressure sensor at a rate greater than 1 hertz. 
     
     
         31 . The fluid system of  claim 1 , wherein the aspects of the electrical signal are voltage, phase current, phase angle, or combinations thereof. 
     
     
         32 . The fluid system of  claim 1 , wherein the electric motor is a brushless DC motor and the fluid pump is an axial piston type pump. 
     
     
         33 . The fluid system of  claim 1 , wherein the fluid pump is a fixed displacement pump. 
     
     
         34 . The fluid system in  claim 1 , wherein the electric motor is a brushless DC motor and the fluid pump is a radial piston type pump. 
     
     
         35 . A fluid system comprising:
 a fluid pump having an output;   an electric motor coupled to the fluid pump, the electric motor being adapted to operate the fluid pump in response to an electrical signal;   a controller adapted to communicate the electrical signal to the electric motor, the controller including a lookup table having performance data related to the fluid pump and the electric motor, wherein the performance data from the lookup table is used by the controller to set aspects of the electrical signal communicated to the electric motor to achieve a desired system pressure generated by the fluid pump; and   a pressure sensor in communication with the output that is adapted to communicate a sensed system pressure to the controller, the controller being adapted to update the lookup table based on a difference between the desired system pressure and the sensed system pressure to minimize variation between the sensed system pressure and the desired system pressure.   
     
     
         36 . The fluid system of  claim 35 , wherein the lookup table establishes a relationship between motor current, motor speed, and the desired system pressure. 
     
     
         37 . The fluid system of  claim 36 , further comprising a motor speed sensor for communicating a sensed motor speed to the controller, wherein the electrical signal includes a motor current command, and wherein the controller determines a value of the motor current command for achieving the desired system pressure from the lookup table based on the sensed motor speed. 
     
     
         38 . The fluid system of  claim 35 , wherein the lookup table is updated based on sensed system pressure sensed while the fluid system is operating at steady state and the lookup table is not updated based on sensed system pressure sensed while system is operating in a transitory state. 
     
     
         39 . A fluid system comprising:
 a fluid pump having an output;   an electric motor coupled to the fluid pump, the electric motor being adapted to operate the pump in response to an electrical signal;   a controller adapted to communicate the electrical signal to the electric motor, the controller including a lookup table having performance data related to the fluid pump and the electric motor, wherein the performance data from the lookup table is used by the controller to set aspects of the electrical signal communicated to the electric motor in order to achieve a desired attribute of the fluid pump; and   a pressure sensor in communication with the output is adapted to communicate a sensed pressure to the controller, the controller adapted to create a modified lookup table to minimize variation in the output.   
     
     
         40 . A fluid system comprising:
 at least two fluid pumps, each pump having an output;   an electric motor coupled to each fluid pump, the electric motor being adapted to operate the pump in response to an electrical signal;   at least one controller adapted to communicate the electrical signal to the electric motor, the controller including a lookup table having performance data related to the fluid pumps and the electric motors, wherein the performance data from the lookup table is used by the controller to set aspects of the electrical signal communicated to each electric motor in order to achieve a desired attribute of the fluid pumps; and   a pressure sensor in communication with the outputs is adapted to communicate a sensed pressure to the controller, the controller adapted to create a modified lookup table to minimize variation in the outputs.