US 11,692,563 B2
Milling machine having a valve current based height measurement system
Eric S. Engelmann, Delano, MN (US); Conwell K. Rife, Jr., Wayzata, MN (US); and Mark Holub, Chillicothe, IL (US)
Assigned to Caterpillar Paving Products Inc., Brooklyn Park, MN (US)
Filed by CATERPILLAR PAVING PRODUCTS INC., Brooklyn Park, MN (US)
Filed on Jan. 28, 2020, as Appl. No. 16/774,280.
Prior Publication US 2021/0231138 A1, Jul. 29, 2021
Int. Cl. F15B 15/28 (2006.01); E01C 23/088 (2006.01)
CPC F15B 15/2838 (2013.01) [E01C 23/088 (2013.01); F15B 2211/4053 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A milling machine, comprising:
a frame;
a milling drum attached to the frame;
a plurality of ground engaging tracks configured to support the frame and to propel the milling machine in a forward or rearward direction;
a plurality of actuators connecting the frame to the tracks, the actuators being configured to adjust a height of the frame relative to a ground surface, each of the actuators including:
a cylinder attached to the frame and containing a hydraulic fluid;
a piston slidably disposed within the cylinder; and
a rod having a first end connected to the piston and extending to a second end connected to a track from among the plurality of ground engaging tracks;
a tank configured to store the hydraulic fluid;
a fluid conduit connecting the tank to the cylinder;
a control valve configured to selectively control a flow rate of the hydraulic fluid in the fluid conduit; and
a controller configured to determine the height of the frame relative to the ground surface by:
determining an amount of current flowing through the control valve; and
determining the flow rate based on the amount of current.