TECHNICAL FIELD

The present disclosure generally relates to a milling machine such as a cold planer. More particularly, the present disclosure relates to a system and method for steering the milling machine.

BACKGROUND

Milling machines can include machines such as cold planers and reclaimers. Cold planers are powered machines used to remove at least part of a surface of a paved area such as a road, bridge, or parking lot. Typically, cold planers include a frame, a power source, a milling assembly positioned below the frame, and a conveyor system. The milling assembly includes a cutting rotor having numerous cutting bits disposed thereon. As power from the power source is transferred to the milling assembly, this power is further transferred to the cutting rotor, thereby rotating the cutting rotor about its axis. As the rotor rotates, its cutting bits engage the hardened asphalt, concrete or other materials of an existing surface of a paved area, thereby removing layers of these existing structures. The spinning action of the cutting bits transfers these removed layers to the conveyor system which transports the removed material to a separate powered machine such as a haul truck for removal from a work site.

Larger road milling machines require multiple cylinders to provide enough force to steer the tracks. Having multiple cylinders can limit changing from Ackerman steering to parallel steering, which is used to improve machine maneuverability.

US 2013/0158802 discloses a steering system for a crawler track machine having multiple steering modes.

SUMMARY

In an example according to this disclosure, a milling machine can include a frame; at least two tracks coupled to the frame for propelling the milling machine; first and second hydraulic cylinders configured to steer each of the at least two tracks, respectively; an adjustable hydraulic tie rod extending between the at least two tracks; first and second steering collars coupled to the each of the tracks to move the tracks, wherein the first hydraulic cylinder is coupled to the first steering collar and the second hydraulic cylinder is coupled to the second steering collar, and wherein the adjustable hydraulic tie rod is coupled to both of the steering collars; one or more sensors to determine the positions of the at least two tracks; and a hydraulic steering control system coupled to the first and second hydraulic cylinders and the adjustable hydraulic tie rod and configured to vary a steering mode of the at least two tracks between a parallel steering mode and an Ackerman steering mode, wherein if one of the one or more sensors fails, the hydraulic steering control system defaults to move the at least two tracks into the Ackerman steering mode.

In one example, a steering control system for a milling assembly can include first and second hydraulic cylinders configured to steer each of at least two tracks of the milling assembly, wherein the first and second cylinders are coupled to first and second steering collars coupled to each of the first and second tracks, respectively; an adjustable hydraulic tie rod extending between the at least two tracks, wherein the adjustable hydraulic tie rod is coupled to each of the first and second steering collars; and a hydraulic steering control system including one or more sensors to determine the positions of the at least two tracks, the hydraulic steeling control system being coupled to the first and second hydraulic cylinders and the adjustable hydraulic tie rod and configured to vary a steering mode of the at least two tracks between a parallel steering mode and an Ackerman steering mode, wherein if one of the one or more sensors fails, the hydraulic steering control system defaults to move the at least two tracks into the Ackerman steering mode.

In one example, a method of controlling steering of a milling machine can include coupling first and second hydraulic cylinders configured to steer each of at least two tracks of the milling machine to first and second steering collars coupled to each of the first and second tracks, respectively; coupling an adjustable hydraulic tie rod extending between the at least two tracks to each of the first and second steeling collars; and activating a hydraulic steering control system including one or more sensors to determine the positions of the at least two tracks, the hydraulic steeling control system being coupled to the first and second hydraulic cylinders and the adjustable hydraulic tie rod and configured to vary a steering mode of the at least two tracks between a parallel steering mode and an Ackerman steering mode, wherein if one of the one or more sensors fails, the hydraulic steering control system defaults to move the at least two tracks into the Ackerman steering mode.

