Abstract: A system for providing torque assist in a vehicle includes a hydrostatic transmission that is associated with otherwise unpowered wheels of the vehicle. Operation of the hydrostatic transmission can be commanded by a controller based on sensor inputs, indicative of wheel speeds of each wheel present in the vehicle, to provide torque to the otherwise unpowered wheels of the vehicle. Moreover, when torque difference exists between one wheel and another from the otherwise unpowered wheels, the controller can independently and selectively actuate one or more pumps that are included in the hydrostatic transmission so that each wheel from the set of otherwise unpowered wheels rotates at the same wheel speed.

Abstract: A hydraulic system is disclosed for use with a machine. The hydraulic system may have a closed-loop, meterless hydraulic circuit with a first pump fluidly connected to a first actuator. The hydraulic system may also have a closed-loop, metered hydraulic circuit with a second pump fluidly connected to a second actuator. The hydraulic system may further have a combiner valve configured to selectively direct fluid from the closed-loop metered hydraulic circuit to the closed-loop meterless hydraulic circuit.

Abstract: A hydraulic system is disclosed for use with a machine. The hydraulic system may have a closed-loop, meterless hydraulic circuit with a first pump fluidly connected to a first actuator. The hydraulic system may also have a closed-loop, metered hydraulic circuit with a second pump fluidly connected to a second actuator. The hydraulic system may further have a combiner valve configured to selectively direct fluid from the closed-loop metered hydraulic circuit to the closed-loop meterless hydraulic circuit.

Abstract: A method and apparatus for controlling a hydraulic power system that includes a hydraulic motor and a hydraulic pump configured to supply hydraulic fluid to the hydraulic motor is provided. A relief valve is provided that is configured to release hydraulic fluid from a location between the hydraulic pump and the hydraulic motor when a pressure of the hydraulic fluid exceeds a predetermined pressure. A controller is in communication with the hydraulic motor and the hydraulic pump. The controller is configured to determine a first hydraulic fluid flow across the relief valve and determine a desired maximum flow across the relief valve. The controller also can regulate one or both of the hydraulic pump and the hydraulic motor to control the first hydraulic fluid flow based on the desired maximum flow.

Abstract: A flushing system for a transmission is disclosed. The system has a first pump and a first actuator connected to the first pump to form a first loop. The system also has a second pump and a second actuator connected to the second pump to form a second loop. The system further has a charge pump configured to replenish the first and second loops. The system also has a single charge relief valve situated to receive fluid from the first pump, the second pump, and the charge pump.

Abstract: A flushing system for a transmission is disclosed. The system has a first pump and a first actuator connected to the first pump to form a first loop. The system also has a second pump and a second actuator connected to the second pump to form a second loop. The system further has a charge pump configured to replenish the first and second loops. The system also has a single charge relief valve situated to receive fluid from the first pump, the second pump, and the charge pump.

Abstract: A method of flowing hydraulic fluid in a work machine is disclosed. The method includes generating a control signal from an input mechanism and generating a property signal indicative of a viscosity of the hydraulic fluid. The control signal and the property signal are received at a control module. The method also includes determining a desired volume flow rate for the control signal and determining a valve control signal required to achieve the desired volume flow rate for the control signal. The valve control signal is based upon the property signal. The valve control signal is output to a proportional valve to provide the desired volume flow rate through the valve for the command signal.