Patent ID: 8886415

Claim:
A hydraulic system, comprising: a pump configured to pressurize fluid; a lift actuator; a lift valve arrangement configured to meter pressurized fluid from the pump into the lift actuator to lift a work tool; a tilt actuator; a tilt valve arrangement configured to meter pressurized fluid from the pump into the tilt actuator to tilt the work tool; at least one sensor configured to generate a first signal indicative of an actual tilt angle of the work tool; at least one operator interface device movable by an operator to generate a second signal indicative of a desired lift velocity of the work tool, and a third signal indicative of desired tilt velocity of the work tool; and a controller in communication with the lift valve arrangement, the tilt valve arrangement, the at least one sensor, and the at least one operator interface device, the controller being configured to: command the lift valve arrangement to meter pressurized fluid into the lift actuator to lift the work tool based on the second signal; command the tilt valve arrangement to meter pressurized fluid into the tilt actuator to tilt the work tool based on the third signal; and when the desired tilt velocity is non-zero and below a threshold: determine a target tilt velocity that results in the work tool being maintained at a desired tilt angle during lifting by scaling the desired lift velocity using: a first scaling factor when the work tool is tilting in a first direction, and a second scaling factor different from the first scaling factor when the work tool is tilting in a second direction opposite the first direction; determine a tilt command based on the target tilt velocity; and direct the tilt command to the tilt valve arrangement during work tool lifting, when the first signal indicates that the actual tilt angle of the work tool has entered a specified range of tilt angles during lifting, command the tilt valve arrangement to meter pressurized fluid into the tilt actuator based on the second signal and maintain the desired tilt angle of the work tool as long as the actual tilt angle of the work tool remains within the specified range, and when the first signal indicates that the actual tilt angle of the work tool is no longer within the specified range of tilt angles during lifting, command the tilt valve arrangement to gradually reduce the meter of pressurized fluid into the lift actuator and gradually reduce the meter of pressurized fluid into the tilt actuator.