Uncommanded steering detection

Patent metadata

Field	Value
Publication number	US-2017001663-A1
Application number	US-201514755634-A
Country	US
Kind code	A1
Filing date	Jun 30, 2015
Priority date	Jun 30, 2015
Publication date	Jan 5, 2017
Grant date	—

Abstract

Uncommanded steering detection in a machine can be performed by comparing commanded and actual steering positions of an electro-hydraulic steering cylinder along with a velocity of movement of the cylinder to understand a steering error and whether the actual steering position is moving toward the commanded steering position. A steering error, when above a predetermined threshold, may be cumulatively summed and, if the cumulative sum exceeds a predetermined limit, an alarm may be triggered and the machine may be forced to a safe state (slowed or stopped). The steering error for the actual steering position may be increased if the velocity of movement is not toward the commanded steering position so that the alarm will be triggered sooner. In either case, the response of the machine to steering uncommanded motion will be swifter when the uncommanded motion is more severe (greater error and/or steering in the wrong direction).

First claim

What is claimed is:

1 . A steering control system for a machine, the steering control system comprising:
a hydraulic steering cylinder having a steering piston that moves in a first piston direction to cause the machine to turn toward a first turn direction and moves in a second piston direction to cause the machine to turn toward a second turn direction; a steering control mechanism operatively connected to the hydraulic steering cylinder and actuatable to cause the steering piston to move in the first piston direction and the second piston direction; a steering control device for providing a steering command signal indicating a command to cause the machine to turn in one of the first turn direction and the second turn direction; a steering piston position sensor operatively connected to the hydraulic steering cylinder to detect a position of the steering piston and to transmit a steering piston position signal indicating the position of the steering piston; and an electronic control unit operatively connected to the steering control mechanism, the steering control device, and the steering piston position sensor, the electronic control unit configured to:
receive the steering command signal from the steering control device and output a steering control mechanism command signal to cause the steering control mechanism to actuate to move the steering piston in the one of the first piston direction and the second piston direction corresponding to the one of the first turn direction and the second turn direction in the steering command signal,
determine an actual steering piston position of the steering piston based on the steering piston position signal,
compare the actual steering piston position to a commanded steering piston position,
determine a steering position error in response to determining that the actual steering piston position is not equal to the commanded steering piston position,
add the steering position error to a cumulative integration value, the cumulative integration value being increased so long as the actual steering piston position is not equal to the commanded steering piston position,
compare the cumulative integration value to an integration limit for uncommanded motion of the machine, and
execute an uncommanded motion response strategy in response to determining that the cumulative integration value is greater than the integration limit.

2 . The steering control system of claim 1 , wherein the electronic control unit is configured to set the steering position error equal to a difference between the actual steering piston position and the commanded steering piston position.

3 . The steering control system of claim 1 , wherein the electronic control unit is configured to determine a steering piston velocity from a previous steering piston position to the actual steering piston position, and the electronic control unit is configured to set the steering position error to a greater value in response to determining from the steering piston velocity that the steering piston is moving in an actual piston movement direction that is opposite the one of the first piston direction and the second piston direction corresponding to the one of the first turn direction and the second turn direction in the steering command signal.

4 . The steering control system of claim 1 , wherein the electronic control unit is configured to determine an actual piston movement direction from a previous steering piston position to the actual steering piston position, and the electronic control unit is configured to set the steering position error to a greater value in response to determining that the actual piston movement direction is opposite the one of the first piston direction and the second piston direction corresponding to the one of the first turn direction and the second turn direction in the steering command signal.

5 . The steering control system of claim 4 , wherein the electronic control unit is configured to set the steering position error equal to a difference between the actual steering piston position and the commanded steering piston position in response to determining that the actual piston movement direction is equal to the one of the first piston direction and the second piston direction corresponding to the one of the first turn direction and the second turn direction in the steering command signal, and the electronic control unit is configured to set the steering position error equal to the difference between the actual steering piston position and the commanded steering piston position multiplied by a direction weighting factor in response to determining that the actual piston movement direction is opposite the one of the first piston direction and the second piston direction corresponding to the one of the first turn direction and the second turn direction in the steering command signal.

6 . The steering control system of claim 4 , wherein the electronic control unit is configured to set the steering position error equal to a difference between the actual steering piston position and the commanded steering piston position in response to determining that the actual piston movement direction is opposite the one of the first piston direction and the second piston direction corresponding to the one of the first turn direction and the second turn direction in the steering command signal, and the electronic control unit is configured to set the steering position error equal to the difference between the actual steering piston position and the commanded steering piston position divided by a direction weighting factor in response to determining that the actual piston movement direction is equal to the one of the first piston direction and the second piston direction corresponding to the one of the first turn direction and the second turn direction in the steering command signal.

7 . The steering control system of claim 1 , wherein the electronic control unit is configured to set the cumulative integration value equal to zero in response to determining that the actual steering piston position is equal to the commanded steering piston position.

8 . The steering control system of claim 1 , wherein the electronic control unit is configured to repeat steps for determining whether the actual steering piston position is equal to the commanded steering piston position in response to determining that the cumulative integration value is less than the integration limit.

9 . A method for detecting and responding to uncommanded motion in a machine having a hydraulic steering cylinder with a steering piston that moves in a first piston direction to cause the machine to turn in a first turn direction and moves in a second piston direction to cause the machine to turn in a second turn direction, the method for detecting and responding to uncommanded motion in the machine comprising:
generating, at an electronic control unit, a steering command signal to move the steering piston in one of the first piston direction and the second piston direction; determining, at the electronic control unit, an actual steering piston position of the steering piston; comparing, at the electronic control unit, the actual steering piston position to a commanded steering piston position; determining, at the electronic control unit, a steering position error in response to determining that the actual steering piston position is not equal to the commanded steering piston position; adding, at the electronic control unit, the steering position error to a cumulative integration value for uncommanded motion, the cumulative integration value being increased so long as the actual steering piston position is not equal to the commanded steering piston positio

Assignees

• Caterpillar Paving Products Inc

Inventors

• Moberg Carl

Classifications

• B60W10/18

  including control of braking systems · CPC title

• B62D6/04 Primary

  responsive only to forces disturbing the intended course of the vehicle, e.g. forces acting transversely to the direction of vehicle travel · CPC title

• B62D5/0481

  monitoring the steering system, e.g. failures · CPC title

• A01B69/00

  Steering of agricultural machines or implements; Guiding agricultural machines or implements on a desired track · CPC title

• B60W2300/17

  Construction vehicles, e.g. graders, excavators · CPC title