Data processing: measuring – calibrating – or testing – Calibration or correction system – For mechanical system
Patent
1997-04-15
2000-08-08
Assouad, Patrick
Data processing: measuring, calibrating, or testing
Calibration or correction system
For mechanical system
36414801, 36452817, G05B 1300
Patent
active
061014567
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an output correcting method in a control system, a control system, and a hydraulic pump control system, and more particularly to an output correcting method in a control system, a control system, and a hydraulic pump control system which are suitably employed to control the delivery rate of a variable displacement hydraulic pump mounted on hydraulic working machines such as hydraulic excavators.
BACKGROUND ART
Heretofore, a known hydraulic pump control system for controlling the delivery rate of a variable displacement hydraulic pump has been proposed in, e.g., JP-U-5-64506. This conventional control system comprises a variable displacement hydraulic pump, a hydraulic actuator driven by a hydraulic fluid delivered from the hydraulic pump, a flow control valve of a center bypass type controlling the flow rate of the hydraulic fluid supplied to the hydraulic actuator, a center bypass line extended from the hydraulic pump to a reservoir while penetrating a center bypass of the flow control valve, a throttle valve disposed in the center bypass line on the downstream side thereof for generating a control pressure (negative control pressure), a sensor for detecting a value of the generated control pressure, a controller for receiving a signal from the sensor, calculating a target pump tilting of the hydraulic pump and outputting a drive current corresponding to the calculated target pump tilting, a proportional solenoid valve for producing a command pressure corresponding to the drive current, and a regulator for controlling the tilting of the hydraulic pump in accordance with the command pressure from the proportional solenoid valve.
In the above construction, when the stroke amount of the flow control valve is small and the flow rate of the hydraulic fluid passing through the center bypass line is large, i.e., when the pressure upstream of the throttle valve is high, the controller calculates the target pump tilting so as to reduce the delivery rate of the hydraulic pump. When the stroke amount of the flow control valve is large and the flow rate of the hydraulic fluid passing through the center bypass line is small, i.e., when the pressure upstream of the throttle valve is low, the controller calculates the target pump tilting so as to increase the delivery rate of the hydraulic pump.
Further, the controller converts the target pump tilting calculated as mentioned above into a command value in the form of a drive current, and then outputs the drive current to the proportional solenoid valve. As a result, the proportional solenoid valve outputs a command pressure corresponding to the drive current, and the hydraulic fluid is delivered from the hydraulic pump at a flow rate corresponding to the target pump tilting.
DISCLOSURE OF THE INVENTION
However, the foregoing conventional control system has described below.
In the conventional control system, as stated above, the controller outputs a drive current corresponding to the calculated target pump tilting, the proportional solenoid valve produces a command pressure corresponding to the drive current, and the regulator controls the tilting of the hydraulic pump in accordance with the command pressure produced by the proportional solenoid valve. It is inevitable, however, that input/output characteristics of the proportional solenoid valve and the regulator have certain tolerances with respect to the target input/output characteristics, and characteristics of individual components vary depending on the components. Accordingly, even though the controller outputs a drive current corresponding to the target pump tilting based on the target input/output characteristics of the proportional solenoid valve and the regulator, there occurs a deviation between the target pump tilting and the actual pump tilting if an actual characteristic of the installed proportional solenoid valve or regulator is deviated from the target input/output characteristic thereof within the range of tolerance. The amount of such a deviation
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Hirata Toichi
Ishikawa Kouji
Kowatari Youichi
Sugiyama Genroku
Takegahara Hidefumi
Assouad Patrick
Hitachi Construction Machinery Co. Ltd.
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