Method and apparatus for constructing an environment map of a self-propelled, mobile unit

• US 5,684,695 A
• Filed: 03/10/1995
• Issued: 11/04/1997
• Est. Priority Date: 03/11/1994
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Bauer, Rudolf
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): WALDER, STEPHEN JOSEPH
• Application Number:
  US08/401,968
• Time in Patent Office: 970 Days
• Field of Search: 364/424.02, 364/513, 364/424.027, 364/424.029, 364/424.031, 364/424.032, 364/424.033, 364/461, 364/460, 358/103, 180/167, 180/168, 180/169, 318/568.16
• US Class Current: 701/23
• CPC Class Codes: G01S 13/881 for robotics
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 15/89 for mapping or imaging
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30

Abstract

An improved method and apparatus for constructing a cellularly structured environment map of a self-propelled, mobile unit is provided. Examples of such self-propelled, mobile units are household robots, self-propelled vacuum cleaners and industrial transport vehicles. To this end, a higher increment for the occupancy degree of a currently evaluated cell is selected for near objects. Further, the occupancy degree is also incremented dependent on a velocity. As an additional measure given standstill of the unit, all cells of the environment map that are located within the aperture cone of a wavefront that emanates from the sensor of the mobile unit are modified in terms of their occupancy degree values. Additionally, a blind zone in which grid cells of the environment map experience no modification of the occupancy degree is defined around the mobile unit.

Claims

1. Method for producing a cellularly structured environment map of a self-propelled, mobile unit which orients itself in the environment with the assistance of sensors based on wave reflection, said method comprising the steps of:

measuring a distance using a sensor in at least one measuring cycle, said distance being between the sensor and an environmental object and a position thereof being defined in a number of first cells located on a circular arc segment with the sensor as mid-point of the arc and the distance as radius, whereby the circular arc segment is limited by the aperture angle of a conical wavefront emanating from the sensor;

arbitrarily selecting one of the first cells;

positively incrementing the occupancy degree of the selected first cell, when an environmental object is present, lying on the circular arc segment dependent on the respective measuring cycle; and

negatively incrementing the occupancy degree, insofar as such an occupancy degree is present, of at least one second cell that is located within the circular sector that is defined by the aperture angle of the wavefront and the circular arc segment.

2. Method according to claim 1, further comprising the steps of:

defining a blind zone that adjoins the sensor in the measuring direction of at least one sensor dependent on a measuring imprecision of the sensor such that the occupancy degree of a cell of the environment map which is located within the blind zone is not modified.

3. Method according to claim 1, wherein the increment with which the occupancy degree is incremented is dependent on the distance of the environmental object from the mobile unit.

4. Method according to claim 3, further comprising the step of:

selecting a greater increment for a relatively small distance than for a greater distance.

5. Method according to claim 1, whereby the increment is dependent on a locomotion velocity of the serf-propelled, mobile unit.

6. Method according to claim 5, further comprising the step of:

selecting a greater increment for a relatively high locomotion velocity than for a lower locomotion velocity.

7. Method according to claim 1, further comprising the step of:

producing at least two cellularly structured environment maps representing the environment at different heights of the self-propelled, mobile unit.

8. A method for producing a cellularly structured environment map of a self-propelled, mobile unit which orients itself in the environment with the assistance of sensors based on wave reflection, said method comprising the steps of:

measuring a distance using a sensor in at least one measuring cycle of a plurality of measuring cycles, said distance being between the sensor and an environmental object and a position thereof being defined in a plurality of cells located on a circular arc segment with the sensor as mid-point of the arc and the distance as radius, whereby the circular arc segment is limited by the aperture angle of a conical wavefront emanating from the sensor;

arbitrarily selecting one of the first cells;

positively incrementing an occupancy degree of the selected first cell, when an environmental object is present, lying on the circular arc segment dependent on a respective measuring cycle of the plurality of measuring cycles; and

negatively incrementing the occupancy degree, insofar as such an occupancy degree is present, of cells other than the selected first cell that is located within the circular sector that is defined by the aperture angle of the wavefront and the circular arc segment.

9. The method according to claim 8, wherein the increment is dependent on a locomotion velocity of the self-propelled, mobile unit.

10. The method according to claim 9, further comprising the step of:

selecting a greater increment for a relatively high locomotion velocity than for a lower locomotion velocity.

11. The method according to claim 9, further comprising the step of:

producing at least two cellularly structured environment maps representing the environment at different heights of the self-propelled, mobile unit.

12. The method according to claim 8, further comprising the steps of:

defining a blind zone that adjoins the sensor in the measuring direction of at least one sensor dependent on a measuring imprecision of the sensor such that the occupancy degree of a cell of the environment map which is located within the blind zone is not modified.

13. The method according to claim 8, wherein the increment with which the occupancy degree is incremented is dependent on the distance of the environmental object from the mobile unit.

14. The method according to claim 13, further comprising the step of:

selecting a greater increment for a relatively small distance than for a greater distance.