Electronic pressure limiting for dual path systems

Abstract

A pressure limiting system for a dual path machine wherein an input propel command from a propel device is scaled based upon the largest detected pressure in a hydraulic system to determine a modified propel command. Also, response time is adjusted within an electrical control system based upon the type of input propel command signal received.

Claims

1. A method of electronically limiting pressure and providing pressure sensitive overrides for a dual path machine, comprising the steps of: transmitting an input propel command from a propel device to a computer of an electronic control system; transmitting signals from pressure sensors from a hydraulic system; determining a modified propel command using a processor and software from the computer by scaling the input propel command based upon the largest pressure sensor signal received; and adjusting an actuator on a pump based upon the modified propel command; and determining a type of the input propel command and adjusting a response time of the hydraulic system based on the determination; wherein response time is decreased when the input propel command is determined to be a speed command.

2. The method of claim 1 wherein electronic hydraulic valves are connected to the actuators and are adapted to vary speed ratios and direction of operation on the pump.

3. The method of claim 1 wherein the input control command includes a steering command and a speed command.

4. The method of claim 1 wherein the step of scaling is applied in conjunction with a control system.

5. The method of claim 1 wherein output from the computer is commanded to pump actuators and motors.

6. The method of claim 1 further comprising the step of determining whether the input propel command is a steering command or a speed command.

7. The method of claim 6 wherein response time is increased when the input propel command is determined to be a steering command.

8. A method of electronically limiting pressure and providing pressure sensitive overrides for a dual path machine, comprising the steps of: transmitting an input propel command from a propel device to a computer of an electronic control system, wherein the input control command includes a steering command and a speed command; transmitting signals from pressure sensors from a hydraulic system; determining a modified propel command using a processor and software from the computer; adjusting an actuator on a pump based upon the modified propel command; and determining whether the input propel command is a steering command or a speed command.

9. A method of electronically limiting pressure and providing pressure sensitive overrides for a dual path machine, comprising the steps of: transmitting an input propel command from a propel device to a computer of an electronic control system; transmitting signals from pressure sensors from a hydraulic system; determining a modified propel command using a processor and software from the computer; adjusting an actuator on a pump based upon the modified propel command; and determining whether the input propel command is a steering command or a speed command and adjusting response time of the hydraulic system based on the determination.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of a pressure limiting system for a dual path machine; and

(2) FIG. 2 is a flow diagram of a method of limiting pressure in a dual path machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) Referring to the Figures, a method and system of electronically limiting pressure and providing pressure compensated overrides for dual path machines 10 includes a hydraulic system 12 and an electrical control system 14. The hydraulic system 12 generally includes a pair of pumps 16 having pump actuators 18 in fluid communication via fluid conduits 20 with a pair of motors 22. The motors 22 are operatively connected to and drive the dual path machine 10. The hydraulic system 12 also has a plurality of sensors 24 that sense pressure in the system 12 and motor actuators 26 which are in fluid communication with the pump actuators 18 to vary speed ratios and the direction of operation of the machine 10.

(4) The electrical control system 14 includes a computer 28 having a processor 30, memory 32, software 34, a display 36, and an input device 38. A propel device 40, used to steer and control the speed of the dual path machine 10, is connected to the computer 28. The propel device 40, based upon manual operation, provides an input propel command 42 to the computer 28. The input propel command 42 includes a steering command 44 and/or a speed command 46. Also connected to the computer 28 are the pressure sensors 24 the pump actuators 18, and the motor actuators 26 through a control system 48.

(5) In operation, an input propel command 42 and signals from sensors 24 are sent to the computer 28. Using the software 34, the processor 30 scales the input propel command 42 according to the largest pressure sensor 24 feedback signal to determine a modified propel command 50. For example, as shown in the table below, as the pressure increases, the input control command 42 is reduced.

(6) TABLE-US-00001 Pressure Modified In 300 bar IPC 100% 360 bar IPC 50% 420 bar IPC 0%

(7) The control system 48 uses the scaling to control the machine. In one example the pressure limit scaling is applied in conjunction with a state brake which is used to control the machine acceleration states.

(8) The modified propel command 50 is output from the control system 48 and commanded to the pump actuators 18 and the motor actuators 26. This varies the fluid flow to vary the speed ratios and the travel rate of the machine 10.

(9) When scaling the input propel command 42 the software 34 also distinguishes between whether the input propel command 42 is a steering command 44 or a speed command 46. Based upon this distinction, the response time of the pressure limit is increased or decreased based upon the type of situation the machine encounters.

(10) For example, if the machine 10 is being steered, the pressure limit needs to respond very quickly to increase the motor torque and reduce steering delay. If the machine 10 is climbing a long gradual hill, the pressure limit needs to respond slowly to reduce oscillations and overshoots. The response rates are adjusted by control system 48 by changing the acceleration and deceleration rates depending on the machine state such as propel command, pressure input, and the like.

(11) Accordingly, a method and system for limiting pressure and providing pressure compensated overrides for dual path machines 10 has been disclosed that, at the very least, meets all the stated objectives.

(12) From the above discussion and accompanying figures and claims it will be appreciated that the dual path machine 10 offers many advantages over the prior art. It will be appreciated further by those skilled in the art that other various modifications could be made to the device without parting from the spirit and scope of this invention. All such modifications and changes fall within the scope of the claims and are intended to be covered thereby. It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in the light thereof will be suggested to persons skilled in the art and are to be included in the spirit and purview of this application.