Automatic steering method and apparatus for a non- railed transfer crane

• US 5,610,816 A
• Filed: 04/14/1995
• Issued: 03/11/1997
• Est. Priority Date: 09/15/1992
• Status: Expired due to Term

• Current Assignee: Samsung Heavy Industries Company Limited (Samsung Group)
• Original Assignee: Samsung Heavy Industries Company Limited (Samsung Group)
• Inventors: Kim, Young Bae
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US08/422,646
• Time in Patent Office: 697 Days
• Field of Search: 364/424.02, 364/424.01, 364/424.05, 364/571.04, 364/444, 364/443, 364/450, 364/449, 318/587, 318/568.12, 212/124-128, 212/131, 180/167-169, 348/155, 348/207, 348/123, 348/116, 348/119, 348/114, 355/60, 355/77, 382/110, 382/153, 356/376
• US Class Current: 701/24
• CPC Class Codes: B66C 9/16 with means for maintaining alignment between wheels and track
• CPC Class Codes: G05D 1/0246 using a video camera in combination with image processing means

Abstract

The present invention relates to an automatic system for controlling the steering of a non-railed transfer crane travelling along a lane indicant. The system comprises a vision sensor for continuously photographing the condition of a crane'"'"'s actual travelling direction with respect to lanes represented by the lane indicant, and outputting predetermined deviations (distance as well as angle) showing off-centered degrees between the crane'"'"'s actual travelling direction and the lanes based on the photographed image signal, and a deviation processor for outputting a control signal to a motor driver so that the crane can travel toward removing the deviation distance. By properly changing a rotative velocity of the crane'"'"'s wheels, the present invention prevents the crane'"'"'s travelling direction from being off-centered from the lanes.

Claims

1. A method for automatically steering a non-railed transfer crane travelling along a lane indicant, comprising the steps of:

photographing a lane indicant along the crane'"'"'s travelling direction with a photographing unit having a previously set horizontal center line intersecting with a previously set vertical center line to define a video center point and generating an image signal;

calculating an actual deviation distance between said video center point and the lane indicant; and

generating a motor control signal for controlling the rotation of a motor which drives wheels of the crane so that the crane travels toward minimizing said calculated actual deviation distance wherein said generating step further comprises the sub-steps of

calculating a differential deviation distance δ

_E equal to the difference between said calculated actual deviation distance and a reference deviation distance, and

calculating a voltage signal V_ref '"'"' for controlling said motor so that said differential deviation distance can approach zero, wherein said voltage signal V_ref '"'"' is calculated with the following equation;

##EQU2## wherein K_p represents a proportionality constant having units of voltage per differential deviation distance;

K_v represents a differential constant having units of voltage per time variation of differential deviation distance;

K_i represents an integral constant having units of voltage per accumulated values of differential deviation distance; and

Δ

T represents a sampling period having units of time.

2. An automatic steering apparatus for controlling a non-railed transfer crane travelling along a lane indicant defining a lane, comprising:

a camera having a photographing unit for continuously photographing an off-centered condition between the direction of travel of said crane and said lane during the travel of said crane, said photographing unit having a previously set horizontal line intersecting with a previously set vertical line to define a video center point at said intersection;

means for converting a video signal input from said camera into a digital image signal;

means for calculating an actual deviation distance between said video center point and said lane indicant from said image signal;

a deviation processor for receiving the calculated actual deviation distance from said calculating means, said deviation processor calculating a differential deviation distance δ

_E equal to the difference between said calculated actual deviation distance and a reference deviation distance, calculating a voltage signal V_ref '"'"' so that said differential deviation distance can approach zero, and generating a control signal based upon said calculated voltage signal to control a motor which drives wheels of said crane to travel toward minimizing the actual deviation distance; and

a motor driver for controlling said motor according to the control signal supplied from said deviation processor, wherein said voltage signal V_ref '"'"' is calculated with the following equation;

##EQU3## wherein K_p represents a proportionality constant having units of voltage per differential deviation distance;

K_v represents a differential constant having units of voltage per time variation of differential deviation distance;

K_i represents an integral constant having units of voltage per accumulated values of differential deviation distance; and

Δ

T represents a sampling period having units of time.

3. The automatic steering apparatus of claim 2, wherein said means for calculating said actual deviation distance further comprises:

an interfacing unit for converting said video signal supplied from said camera into said image signal;

a memory for storing the image signal input from said interfacing unit; and

means for calculating actual deviation distance between the crane'"'"'s travelling direction and the lane based on image data input from said memory and stored data representing a normal condition of steering.