Control system for hydrostatic pump

Abstract

A control system that can be used on a hydrostatic pump has a feedback sensor to detect the angle of a swashplate. From the information gathered by the feedback sensor about the swashplate and another set command, this information is sent to a microprocessor. The microprocessor then uses an algorithm to create an output signal and also sends out a superimposed dither signal. This dithered output signal is then received by a pressure control that causes a dither servo pressure in a servo system. Because of the dither pressure the servo system adjusts the position of the swashplate.

1 . A control system for a hydrostatic unit having a swashplate comprising: 
 an electronic means for producing a dithered output signal;    a pressure control adapted to receive the dithered output signal and position the swashplate.    
   
   
       2 . The control system for a hydrostatic unit of  claim 1  wherein the electronic means is a microprocessor.  
   
   
       3 . The control system of  claim 2  wherein the microprocessor receives information from a set point command signal.  
   
   
       4 . The control system of  claim 2  wherein the microprocessor receives information from a feedback sensor.  
   
   
       5 . The control system of  claim 1  wherein the pressure control is a flapper nozzle style pilot valve with two boost spools.  
   
   
       6 . The control system of  claim 1  further comprising: 
 a servo system operably connected to the pressure control and swashplate.    
   
   
       7 . A method of controlling the angle of a swashplate of a hydrostatic unit having a swashplate comprising steps of: 
 generating an electric signal based on a set point signal;    receiving the electric signal in a microprocessor;    interpolating the information from the electric signal using an algorithm contained in the microprocessor;    sending an output signal from the microprocessor to a pressure control;    dithering the output signal; and    generating a dithered pressure from the pressure control that displaces the swashplate.    
   
   
       8 . The method of  claim 7  wherein the set point signal is generated by measuring an operational parameter.  
   
   
       9 . The method of  claim 8  wherein the operational parameter is the angle of the swashplate.  
   
   
       10 . The method of  claim 7  wherein the algorithm is a PID type algorithm.  
   
   
       11 . The method of  claim 7  wherein the algorithm is a PID+feed forward algorithm.  
   
   
       12 . The method of  claim 7  wherein the algorithm is a KIDT1 algorithm.  
   
   
       13 . The method of  claim 7  wherein the pressure control is a flapper nozzle style pilot valve with two boost spools.  
   
   
       14 . The method of  claim 7  wherein the pressure control is a flapper nozzle style pilot valve with one boost spool.  
   
   
       15 . The method of  claim 7  wherein the pressure control is a flow control.  
   
   
       16 . The method of  claim 7  wherein the pressure control is comprised of two pressure controls.  
   
   
       17 . The method of  claim 7  wherein the output signal is dithered by the pressure control.  
   
   
       18 . The method of  claim 7  wherein the output signal is dithered by the microprocessor.  
   
   
       19 . A control system for a hydrostatic pump having a swashplate comprising: 
 a feedback sensor adapted to sense the angle of the swashplate;    a microprocessor adapted to receive information from the feedback sensor and produce a dithered output signal;    a pressure control adapted to receive the dithered output signal and position the swashplate.    
   
   
       20 . The control system of  claim 19  wherein the microprocessor is also adapted to receive information from a set point command signal.