System for guiding a driverless vehicle

• US 4,703,240 A
• Filed: 03/05/1986
• Issued: 10/27/1987
• Est. Priority Date: 03/07/1985
• Status: Expired due to Fees

• Current Assignee: Murata Machinery Limited (Muratec)
• Original Assignee: Murata Kikai Kabushiki Kaisha (Muratec)
• Inventors: Kondoh, Minoru, Terada, Yoshiyuki, Yoshimoto, Yoshio
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/836,309
• Time in Patent Office: 601 Days
• Field of Search: 318/587, 318/640, 250/202, 250/214, 180/169
• US Class Current: 318/587
• CPC Class Codes: G05D 1/0242 using non-visible light signals, e.g. IR or UV signals
• CPC Class Codes: G05D 1/0244 using reflecting strips

Abstract

A driverless vehicle is guided along a guideline which is detected on a floor by an optical sensor having a plurality of light receiving elements. A value representing the amount of light received by each of the light receiving elements is composed with a value representing the amount of light received by one or more neighbouring light receiving elements and smoothed to an appropriately large value so that the detection of the guideline may be based on the smoothed value.

Claims

1. A method for guiding a driverless vehicle along a guideline which is detected on a surface by an optical sensor having a plurality of light receiving elements, each of said elements being operable to detect the amount of light reflected from a different region of said surface and to generate a signal in response thereto, said method comprising the steps of:

measuring a plurality of values representing the amount of light received by each of said plurality light receiving elements,

comparing the measured value associated with each of said plurality of light receiving elements with a value representing the amount of light received by one or more neighboring light receiving elements,

selecting a smoothed value associated with each light receiving elements based upon the comparison of measured values,

assigning a weighted value associated with each light receiving element based upon the relative position of said light receiving element;

calculating the location of the guideline based on said smoothed value and said weighted value associated with each light receiving element,

whereby said vehicle is guided along said surface in accordance with the calculated location of the guideline.

2. The method as claimed in claim 1, wherein said step of selecting a smoothed value further comprises the steps of:

comparing the amount of light received by each light receiving element with the amount of light received by at least one adjacent light receiving element,

selecting the smaller amount of light received as a smoothed value for each light receiving element having only one adjacent light receiving element, and

selecting the mean amount of light received as a smoothed value for each light receiving element having more than one adjacent light receiving element.

3. The method as claimed in claim 2 further comprising the steps of:

selecting a threshold value from among all of the smoothed values, and

multiplying the smoothed values exceeding the threshold value by said weighted value associated with each sensor element.

4. The method as claimed in claim 3, wherein the center of the guide line is determined by:

numbering all of said light receiving elements in order according to the relative positions of said light receiving elements, and

dividing the sum of the numbered values of those light receiving elements showing the smoothed values which exceed the threshold value by the total of the light receiving elements showing the smoothed values which exceed the threshold value.

5. A system for guiding a vehicle along a surface having a light reflecting guide line, said system comprising:

a plurality of sensor elements associated with said vehicle, each of said sensor elements being operable to detect the amount of light reflected from a different region of said surface and to generate a signal in response thereto, said signal having a value corresponding to the amount of light reflected by said region;

first comparison means for comparing the value of signals generated by adjacent sensor elements;

selection means for selecting a smoothed value associated with each sensor element based upon the comparison of values made by said first comparison means;

weighting means for assigning a weighted value associated with each sensor element based upon the relative position of said sensor element;

calculation means for calculating the location of the guide line based upon the smoothed value and the weighted value associated with each sensor element;

whereby said vehicle is guided along said surface in accordance with the location of the guide line calculated by said calculated means.

6. A system as in claim 5 further comprising:

second comparison means for comparing each of said smoothed values with a predetermined threshold value, and

multiplication means for multiplying the smoothed values greater than the threshold value by said weighted value associated with each sensor element.

8. A system as in claim 5 further comprising:

guide means responsive to said calculation means for guiding said vehicle.

7. A method for guiding a vehicle along a surface having a light-reflecting guideline, said vehicle having a plurality of sensor elements associated therewith, said method comprising the steps of:

detecting the amount of light reflected from a plurality of different regions of said surface and generating a corresponding plurality of signals in response thereto, each of said signals having a value corresponding to the amount of light reflected by one of said different regions,

comparing the value of signals generated by adjacent sensor elements;

selecting a smoothed value associated with each sensor element based upon the comparison of values;

assigning a weighted value associated with each sensor element based upon the relative position of said sensor element;

calculating the location of the guideline based upon the smoothed value and the weighted value associated with each sensor element;

whereby said vehicle is guided along said surface in accordance with the calculated location of the guideline.