Mobile robot internal position error correction system

• US 5,559,696 A
• Filed: 02/14/1994
• Issued: 09/24/1996
• Est. Priority Date: 02/14/1994
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Borenstein, Johann
• Primary Examiner(s): PARK, COLLIN
• Application Number:
  US08/194,873
• Time in Patent Office: 953 Days
• Field of Search: 364/424.01, 364/424.02, 364/449, 364/450, 364/453, 364/457, 364/460, 364/571.01, 340/988, 340/992, 342/450, 342/457, 342/463, 342/465, 371/67.1
• US Class Current: 701/23
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G05D 1/0255 using acoustic signals, e.g. ultra-sonic singals sonar systems designed for anti-collision purposes G01S15/93
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00

Abstract

An improved device and method for performing accurate mobile robot dead-reckoning by performing Internal Position Error Correction (IPEC) which corrects systematic as well as non-systematic dead-reckoning errors. A first variation utilizes a smart encoder trailer which adapts an existing dead-reckoning mobile robot. A second variation provides a pair of robotic vehicles coupled with a compliant linkage which monitors relative positioning between the vehicles in order to perform internal position error correction. A third and final variation utilizes a pair of decoupled mobile robotic vehicles, each performing dead-reckoning, further provided with individual transmitter and receiver arrays which determine relative positioning therebetween in order to perform internal position error correction.

Claims

1. A mobile robot positioning system for performing internal correction of dead-reckoning errors comprising:

a first mobile robotic vehicle;

a second mobile robotic vehicle spaced apart from said first vehicle;

a relative positioning system for ascertaining relative bearing between said first and second vehicles;

a dead-reckoning system for ascertaining position and bearing of said first vehicle relative to a last known position;

error discriminating means for detecting and correcting systematic and non-systematic dead-reckoning errors of said first vehicle by comparing said ascertained relative bearing between said first and second vehicles from said relative positioning system with an ascertained position and bearing from said dead-reckoning system;

wherein said first and second vehicles travel in spaced apart relation while collaborating via said relative positioning system to measure the bearing of said first vehicle with respect to said second vehicle to obtain relative position information for correcting dead-reckoning errors of said robot positioning system.

2. The mobile robot positioning system of claim 1 wherein said second mobile robotic vehicle is a passively towed robotic vehicle trailer having a rotatable coupling with a rotary encoder which is coupled to said first mobile robotic vehicle such that said second vehicle is trailed behind said first vehicle with said vehicles collaborating via said relative positioning system to correct dead-reckoning errors.

3. The mobile robot positioning system of claim 2 wherein said robotic vehicle trailer has a pair of spaced apart rotary encoder wheels on said trailer to provide input to said dead-reckoning system.

4. The mobile robot positioning system of claim 1 wherein said first mobile robotic vehicle is a mobile robot with a plurality of rotary encoder wheels carried in spaced apart relation which provide input to said dead-reckoning system.

5. The mobile robot positioning system of claim 1 wherein said first mobile robotic vehicle is an agricultural vehicle adapted with a plurality of rotary encoders carried in spaced apart relation which provide input to said dead-reckoning system.

6. The mobile robot positioning system of claim 1 wherein said first mobile robotic vehicle is a self-guided vehicle having a plurality of spaced apart rotary encoders which provide input to said dead-reckoning system.

7. The mobile robot positioning system of claim 1 wherein said relative positioning system is a rotatably and axially compliant linkage fixed between said first and second vehicles for sensing relative bearing between said vehicles, said linkage being movable between extended and retracted positions.

8. The mobile robot positioning system of claim 1 wherein said first mobile robotic vehicle is a first end of an automobile and said second mobile robotic vehicle is a second end of said automobile and said relative positioning system further comprises a rotatable coupling with a rotary encoder which couples said first end to said second end such that said second end is trailed behind said first end with said pair of ends collaborating via said relative positioning system to correct dead-reckoning errors.

9. The mobile robot positioning system of claim 1 wherein said first and second mobile robotic vehicles each comprise individual motorized robots with dedicated relative positioning systems which cooperate to determine dead-reckoning errors therebetween, such that said first and second mobile robotic vehicles are decoupled, and travel together in spaced apart relation.

10. The mobile robot positioning system of claim 9 wherein said relative positioning system further comprises a spaced apart array of receivers and at least one transmitter carried on a rotatable sensor arm on each of said vehicles, each of said transmitters for transmitting soundwaves from one of said vehicles to said receivers on the other of said vehicles, so as to determine both position and bearing between said first mobile robotic vehicle and said second mobile robotic vehicle.

11. The mobile robot positioning system of claim 10 wherein said rotatable sensor arm is further provided with a rotary encoder for monitoring geometric positioning of said receivers and said transmitter, said arms, receivers, and transmitters respectively cooperating between each of said vehicles to provide a relative positioning system therebetween.

12. A mobile robot positioning system for adapting an existing dead reckoning mobile robot in order to perform internal correction of dead-reckoning errors which comprises:

a passively towed mobile robotic trailer with a rotatable coupling for connecting said trailer to said mobile robot having a rotary encoder and a plurality of spaced apart rotary encoder wheels for performing dead-reckoning, said rotary encoder further ascertaining relative bearing between said mobile robot and said trailer;

error discriminating means for detecting and correcting systematic and non-systematic dead-reckoning errors of said robot by comparing said ascertained relative bearing between said robot and said trailer from said rotary encoder with an ascertained position and bearing of said robot;

wherein the robot and said trailer travel in a known and constant spaced apart relation while collaborating via said rotary encoder to measure bearing of the robot with respect to the trailer to obtain relative positioning information for correcting dead-reckoning errors of said robot.

13. A method for performing internal correction of dead-reckoning errors for a mobile robot positioning system having a first mobile robotic vehicle, a second mobile robotic vehicle spaced apart from the first vehicle, a relative positioning system for detecting relative bearing between said first and second vehicles, a dead-reckoning system for detecting position and bearing of the first vehicle, and error discriminating means for detecting and correcting dead-reckoning errors of said first vehicle relative to the said second vehicle, said method comprising:

detecting position and bearing of said second vehicle relative to a last known position;

detecting relative bearing between said first and second vehicles;

detecting and correcting systematic and non-systematic dead-reckoning errors of said first vehicle by comparing said detected relative bearing between said first and second vehicles from said relative positioning system with said detected position and bearing from said dead-reckoning system so as to perform error discrimination.

14. A method for performing internal correction of dead-reckoning errors for a mobile robot positioning system of claim 13 wherein said first and second vehicles travel in a spaced apart relation while collaborating via said relative positioning system to measure bearing of said first vehicle with respect to said second vehicle in order to obtain relative position information for correcting dead-reckoning errors of said robot positioning system.