The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 27, 2008
Filed:
Mar. 18, 2005
Keith A. Tabor, Richfield, WI (US);
Joseph L. Pfaff, Wauwatosa, WI (US);
Keith A. Tabor, Richfield, WI (US);
Joseph L. Pfaff, Wauwatosa, WI (US);
HUSCO International, Inc., Waukesha, WI (US);
Abstract
A servomechanism includes a controller which dynamically estimates the resistance of the solenoid coil in an electrohydraulic valve as part of determining a level of electric voltage to apply to open the valve. The servomechanism receives a current setpoint designating a desired electric current level and senses the actual level of current flowing through the coil. A proportional term is derived from the current setpoint and the actual level of current. Creation of a derivative term is based on the difference between the current setpoint and the actual level of current. A feedforward term is produced by estimating the resistance of the electrohydraulic valve and limiting the feedforward term to a predefined range of acceptable values. The proportional term, derivative term, and the feedforward term are summed to define a desired voltage level, and a PWM signal for driving the electrohydraulic valve is generated based on the desired voltage level.