Operation control device for leg-type mobile robot and operation control method, and robot device Number:7,386,364 from the United States Patent and Trademark Office (PTO) owispatent A legged mobile robot gives up a normal walking motion and starts a tumbling motion when an excessively high external force or external moment is applied thereto and a behavior plan of a foot part thereof is disabled. At this time, the variation amount .DELTA.S/.DELTA.t of the area S of a support polygon of the body per time t is minimized and the support polygon when the body drops onto a floor is maximized to distribute an impact which acts upon the body from the floor when the body drops onto the floor to the whole body to suppress the damage to the body to the minimum. Further, the legged mobile robot autonomously restores a standing up posture from an on-floor posture thereof such as a supine posture or a prone posture.<H operation, Operation, Operation, contr, 7386364.html, Patent, pto, 7386364

Title: Operation control device for leg-type mobile robot and operation control method, and robot device

Abstract: A legged mobile robot gives up a normal walking motion and starts a tumbling motion when an excessively high external force or external moment is applied thereto and a behavior plan of a foot part thereof is disabled. At this time, the variation amount .DELTA.S/.DELTA.t of the area S of a support polygon of the body per time t is minimized and the support polygon when the body drops onto a floor is maximized to distribute an impact which acts upon the body from the floor when the body drops onto the floor to the whole body to suppress the damage to the body to the minimum. Further, the legged mobile robot autonomously restores a standing up posture from an on-floor posture thereof such as a supine posture or a prone posture.

Patent Number: 7,386,364 Issued on 06/10/2008 to Mikami, et al.

Inventors: Mikami; Tatsuo (Kanagawa, JP), Yamaguchi; Jinichi (Tokyo, JP), Miyamoto; Atsushi (Kanagawa, JP)
Assignee: Sony Corporation (Tokyo, JP)
Yamaguchi, Jinichi (Tokyo, JP)

Appl. No.: 10/477,452

Filed: March 17, 2003

PCT Filed: March 17, 2003

PCT No.: PCT/JP03/03131

371(c)(1),(2),(4) Date: August 23, 2004

PCT Pub. No.: WO03/078109

PCT Pub. Date: September 25, 2003

Foreign Application Priority Data


Mar 15, 2002 [JP]			2002-073390
Mar 18, 2002 [JP]			2002-073499

Current U.S. Class: 700/245 ; 318/443; 318/568.12; 318/568.22; 318/580; 318/653; 700/247; 700/249; 700/250; 700/258; 700/264; 701/23; 701/25; 901/1; 901/46; 901/47; 901/9

Field of Search: 700/66,245,246,247,248,249,250,253,257,260,262,264,275,261,300 318/9,443,568.12,568.22,580,653,800 701/23,25 901/1,9,46,47

References Cited [Referenced By]

U.S. Patent Documents


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5929585	July 1999	Fujita
6064167	May 2000	Takenaka et al.
6243623	June 2001	Takenaka et al.
6289265	September 2001	Takenaka et al.
6330494	December 2001	Yamamoto
6463356	October 2002	Hattori et al.
6480761	November 2002	Ueno et al.
6493606	December 2002	Saijo et al.
6505098	January 2003	Sakamoto et al.
6567724	May 2003	Yamamoto
6697709	February 2004	Kuroki et al.
6711469	March 2004	Sakamoto et al.
2002/0116091	August 2002	Yamamoto

Foreign Patent Documents


0 856 457	Aug., 1998	EP
1 081 026	Mar., 2001	EP
1 103 450	May., 2001	EP
1 103 451	May., 2001	EP
10-202562	Aug., 1998	JP
11-48170	Feb., 1999	JP
2000-61872	Feb., 2000	JP
2001-62760	Mar., 2001	JP
2001-150370	Jun., 2001	JP
2001-157972	Jun., 2001	JP
2001-212785	Aug., 2001	JP
2001-225289	Aug., 2001	JP

Primary Examiner: Tran; Khoi H.
Assistant Examiner: Marc; McDieunel
Attorney, Agent or Firm: Frommer Lawrence & Haug LLP Frommer; William S.

Claims

The invention claimed is:

1. A motion controlling apparatus for a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, characterized in that said legged mobile robot has a plurality of postures or states, and that said motion controlling apparatus comprises: first means for calculating an area S of a support polygon formed from landed points of a body of said legged mobile robot and a floor; second means for calculating the variation .DELTA.S/.DELTA.t of the area S of the support polygon per time .DELTA.t; and third means for determining a motion of said body when the posture or state is to be changed based on the area S of the support polygon or the variation rate .DELTA.S/.DELTA.t of the area S.

2. A motion controlling apparatus for a legged mobile robot according to claim 1, characterized in that said third means includes: landed location searching means for searching for a landed location upon tumbling of said legged mobile robot based on the variation per time .DELTA.t of the area S of the support polygon formed from the landed points of said body and the floor; target landing point setting means for setting a target landing point at which the location selected by said landed location searching means should be landed so that the variation .DELTA.S/.DELTA.t per time .DELTA.t of the area S of the support polygon formed from the landed points of said body and the floor may be minimized; and location landing means for landing the location selected by said landed portion searching means at the target landing point set by said target landing point setting means.

3. A motion controlling apparatus for a legged mobile robot according to claim 2, further comprising: support polygon expansion means for moving the landed portion so that the support polygon newly formed by landing of the location selected by said location landing means may be further expanded.

4. A motion controlling apparatus for a legged mobile robot according to claim 2, characterized in that the landing operation of the portion by said landed portion searching means and said target landing point setting means and/or the expansion operation of the support polygon by said support polygon expansion means are performed repetitively.

5. A motion controlling apparatus for a legged mobile robot according to claim 2, characterized in that said legged mobile robot is formed from a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, and said target landing point setting means sets a location at which a link with which the number of non-landed links is maximized exists as a target.

6. A motion controlling apparatus for a legged mobile robot according to claim 1, characterized in that said legged mobile robot is formed from a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, and said third means includes: means for searching, when said legged mobile robot returns from its tumbling state, for the narrowest support polygon formed from the least number of links from among landed polygons formed, in an on-floor posture of said legged mobile robot in which two or more links including a gravity center link positioned at the center of gravity of said body are landed on the floor, from the landed links; means for taking off the landed links in the landed polygons except those of the searched out support polygon; means for bending two or more continuous ones of non-landed links until end portions of the end links land onto the floor to form a narrower landed polygon; and means for taking off a number of links greater than a first predetermined number from one end side of said link structure to stand said body uprightly in response to that the support polygon is sufficiently narrow.

7. A motion controlling apparatus for a legged mobile robot according to claim 6, characterized in that said means for searching for the support polygon extracts a landed link which can be taken off from the floor while a zero moment point remains plannable.

8. A motion controlling apparatus for a legged mobile robot according to claim 6, characterized in that said means for searching for the support polygon searches for a narrower support polygon while keeping the gravity center link in the landed state.

9. A motion controlling apparatus for a legged mobile robot according to claim 6, characterized in that said means for standing said body uprightly determines whether or not the gravity center link can be taken off in a state wherein the end portions of the opposite end links of the landed polygon are landed thereby to determine whether or not the support polygon is sufficiently narrow.

10. A motion controlling apparatus for a legged mobile robot according to claim 6, characterized in that said means for standing said body uprightly includes: means for taking off the gravity center link from the floor in a state wherein the end portions of the opposite end links of the support polygon are landed; means for reducing the distance between the end portions of the opposite end links of the support polygon in a state wherein the gravity center link is taken off to move a zero moment point to the other end side of said link structure; and means for taking off, in response to that the zero moment point enters a landed polygon formed only from a number of landed links smaller than a second predetermined number from the other end of said link structure, a number of links greater than a first predetermined number from the one end side of said link structure while the zero moment point is kept accommodated in the landed polygon to expand the non-landed links in the lengthwise direction.

11. A motion controlling apparatus for a legged mobile robot according to claim 10, characterized in that said means for expanding the non-landed links in the lengthwise direction operates positively using a joint degree-of-freedom having a comparatively great mass operation amount.

12. A motion controlling apparatus for a legged mobile robot according to claim 6, characterized in that said link structure includes at least shoulder joint pitch axes, a trunk pitch axis, hip joint pitch axes and knee pitch axes connected to each other in the heightwise direction of said body.

13. A motion controlling apparatus for a legged mobile robot according to claim 12, characterized in that said means for searching for the support polygon extracts two or more continuous links extending from one end side of said link structure which includes at least the shoulder joint pitch axes as links which can be taken off from the floor while the zero moment point remains plannable.

14. A motion controlling apparatus for a legged mobile robot according to claim 12, characterized in that said means for searching for the support polygon searches for a narrower support polygon while a link which interconnects said trunk pitch axis and said hip joint pitch axes is kept as the gravity center link in the landed state.

15. A motion controlling apparatus for a legged mobile robot according to claim 12, characterized in that said means for forming a narrower landed polygon bends the non-landed links around said shoulder joint pitch axes to land the hands which are an end portion of one of the end links onto the floor.

16. A motion controlling apparatus for a legged mobile robot according to claim 15, characterized in that, where the length of the upper arms is represented by l.sub.1, the length of the forehands by l.sub.2, the shoulder roll angle by .alpha., the elbow pitch angle by .beta., the length from the shoulders to the hands by l.sub.12, the angle defined by a line interconnecting each of the shoulders and a corresponding one of the hands by .gamma., and the height of the shoulders by h, each of the arm parts operates so as to satisfy the following expressions: l.sub.12=l.sub.1 cos .alpha.+l.sub.2 sin (.alpha.+.beta.-90) l.sub.12 sin .gamma.<h.

17. A motion controlling apparatus for a legged mobile robot according to claim 12, characterized in that said means for searching for the support polygon extracts two or more continuous links extending from the other end side of said link structure and including at least said knee joint pitch axes as the links which can be taken off from the floor while the zero moment point remains plannable.

18. A motion controlling apparatus for a legged mobile robot according to claim 12, characterized in that said means for forming a narrower landed polygon bends the non-landed links around said knee joint pitch axes to land the soles which are end portions of the end links of said link structure.

19. A motion controlling apparatus for a legged mobile robot according to claim 12, characterized in that said means for standing said body uprightly determines whether or not the gravity center link which interconnects said trunk pitch axis and said hip joint pitch axes can be taken off from the floor in a state wherein the hands and the soles as the end portions of the opposite end links of the landed polygon to determine whether or not the support polygon is sufficiently narrow.

20. A motion controlling apparatus for a legged mobile robot according to claim 12, characterized in that said means for standing said body uprightly includes: means for taking off the gravity center link which interconnects said trunk pitch and said hip joint pitch axes from the floor in a state wherein the hands and the soles as the end portions of the opposite end links of the landed polygon are landed; means for contracting the distance between the hands and the soles as the end portions of the opposite end links of the landed polygon in a state wherein the gravity center link is taken off from the floor to move the zero moment point to the soles; and means for taking off, in response to that the zero moment point enters the landed polygon formed from the soles, the links from said shoulder pitch axes to said knee pitch axes while the zero moment point is kept accommodated in the landed polygon to expand the non-landed links in the lengthwise direction to stand said body uprightly.

21. A motion controlling apparatus for a legged mobile robot according to claim 20, characterized in that said means for expanding the non-landed links in the lengthwise direction operates positively using said knee joint pitch axes having a comparatively great mass operation amount.

22. A motion controlling apparatus for a legged mobile robot according to claim 6, characterized in that said means for producing a narrower landed polygon selectively utilizes one of a step changing motion and a dragging motion on the floor of the hand parts or the foot parts in response to whether it is possible to take off two or more of the links which do not relate to the smallest support polygon from the floor to form a narrower landed polygon.

23. A motion controlling method for a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, characterized in that said legged mobile robot has a plurality of postures or states, and that said motion controlling method comprises: a first step of calculating an area S of a support polygon formed from landed points of a body of said legged mobile robot and a floor; a second step of calculating the variation .DELTA.S/.DELTA.t of the area S of the support polygon per time .DELTA.t; and a third step of determining a motion of said body when the posture or state is to be changed based on the area S of the support polygon or the variation rate .DELTA.S/.DELTA.t of the area S.

24. A motion controlling method for a legged mobile robot according to claim 23, characterized in that said third step includes: a landed location searching step for searching for a landed location upon tumbling of said legged mobile robot based on the variation per time .DELTA.t of the area S of the support polygon formed from the landed points of said body and the floor; a target landing point setting step of setting a target landing point at which the location selected at the landed location searching step should be landed so that the variation .DELTA.S/.DELTA.t per time .DELTA.t of the area S of the support polygon formed from the landed points of said body and the floor may be minimized; and a location landing step of landing the location selected at the landed portion searching step at the target landing point set at the target landing point setting step.

25. A motion controlling method for a legged mobile robot according to claim 24, further comprising: a support polygon expansion step for moving the landed portion so that the support polygon newly formed by landing of the location selected at the location landing step may be further expanded.

26. A motion controlling method for a legged mobile robot according to claim 24, characterized in that the landing operation of the portion at the landed portion searching step and the target landing point setting step and/or the expansion operation of the support polygon at the support polygon expansion step are performed repetitively.

27. A motion controlling method for a legged mobile robot according to claim 24, characterized in that said legged mobile robot is formed from a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, and the target landing point setting step sets a location at which a link with which the number of non-landed links is maximized exists as a target.

28. A motion controlling method for a legged mobile robot according to claim 23, characterized in that said legged mobile robot is formed from a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, and the third step includes the steps of: searching, when said legged mobile robot returns from its tumbling state, for the narrowest support polygon formed from the least number of links from among landed polygons formed, in an on-floor posture of said legged mobile robot in which two or more links including a gravity center link positioned at the center of gravity of said body are landed on the floor, from the landed links; taking off the landed links in the landed polygons except those of the searched out support polygon; bending two or more continuous ones of non-landed links until end portions of the end links land onto the floor to form a narrower landed polygon; and taking off a number of links greater than a first predetermined number from one end side of said link structure to stand said body uprightly in response to that the support polygon is sufficiently narrow.

29. A motion controlling method for a legged mobile robot according to claim 28, characterized in that, at the step of searching for the support polygon, a landed link which can be taken off from the floor while a zero moment point remains plannable is extracted.

30. A motion controlling method for a legged mobile robot according to claim 28, characterized in that, at the step of searching for the support polygon, a narrower support polygon is searched for while keeping the gravity center link in the landed state.

31. A motion controlling method for a legged mobile robot according to claim 28, characterized in that it is determined at the step of standing said body uprightly whether or not the gravity center link can be taken off from the floor in a state wherein the end portions of the opposite end links of the landed polygon are landed thereby to determine whether or not the support polygon is sufficiently narrow.

32. A motion controlling method for a legged mobile robot according to claim 28, characterized in that, at the step of standing said body uprightly, the gravity center link is taken off from the floor in a state wherein the end portions of the opposite end links of the support polygon are landed, and the distance between the end portions of the opposite end links of the support polygon is reduced to move a zero moment point to the other end side of said link structure, and, in response to that the zero moment point enters a landed polygon formed only from a number of landed links smaller than a second predetermined number from the other end of said link structure, a number of links greater than a first predetermined number from the one end side of said link structure are taken off from the floor while the zero moment point is kept accommodated in the landed polygon to expand the non-landed links in the lengthwise direction.

33. A motion controlling method for a legged mobile robot according to claim 32, characterized in that, at the step of expanding the non-landed links in the lengthwise direction, a joint degree-of-freedom having a comparatively great mass operation amount is positively used for the operation.

34. A motion controlling method for a legged mobile robot according to claim 28, characterized in that said link structure includes at least shoulder joint pitch axes, a trunk pitch axis, hip joint pitch axes and knee pitch axes connected to each other in the heightwise direction of said body.

35. A motion controlling method for a legged mobile robot according to claim 34, characterized in that, at the step of searching for the support polygon, two or more continuous links extending from one end side of said link structure which includes at least the shoulder joint pitch axes are extracted as links which can be taken off from the floor while the zero moment point remains plannable.

36. A motion controlling method for a legged mobile robot according to claim 34, characterized in that, at the step of searching for the support polygon, a narrower support polygon is searched for while a link which interconnects said trunk pitch axis and said hip joint pitch axes is kept as the gravity center link in the landed state.

37. A motion controlling method for a legged mobile robot according to claim 34, characterized in that, at the step of forming a narrower landed polygon, the non-landed links are bent around said shoulder joint pitch axes to land the hands which are an end portion of one of the end links onto the floor.

38. A motion controlling method for a legged mobile robot according to claim 37, characterized in that, where the length of the upper arms is represented by l.sub.1, the length of the forehands by l.sub.2, the shoulder roll angle by .alpha., the elbow pitch angle by .beta., the length from the shoulders to the hands by l.sub.12, the angle defined by a line interconnecting each of the shoulders and a corresponding one of the hands by .gamma., and the height of the shoulders by h, each of the arm parts operates so as to satisfy the following expressions: l.sub.12=l.sub.1 cos .alpha.+l.sub.2 sin (.alpha.+.beta.-90) l.sub.12 sin .gamma.<h.

39. A motion controlling method for a legged mobile robot according to claim 34, characterized in that, at the step of searching for the support polygon, two or more continuous links extending from the other end side of said link structure and including at least said knee joint pitch axes are extracted as the links which can be taken off from the floor while the zero moment point remains plannable.

40. A motion controlling method for a legged mobile robot according to claim 34, characterized in that, at the step of forming a narrower landed polygon, the non-landed links are bent around said knee joint pitch axes to land the soles which are end portions of the end links of said link structure.

41. A motion controlling method for a legged mobile robot according to claim 34, characterized in that it is determined at the step of standing said body uprightly whether or not the gravity center link which interconnects said trunk pitch axis and said hip joint pitch axes can be taken off from the floor in a state wherein the hands and the soles as the end portions of the opposite end links of the landed polygon to determine whether or not the support polygon is sufficiently narrow.

42. A motion controlling method for a legged mobile robot according to claim 34, characterized in that, at the step of standing said body uprightly, the gravity center link which interconnects said trunk pitch and said hip joint pitch axes is taken off from the floor in a state wherein the hands and the soles as the end portions of the opposite end links of the landed polygon are landed and the distance between the hands and the soles as the end portions of the opposite end links of the landed polygon is reduced in a state wherein the gravity center link is taken off from the floor to move the zero moment point to the soles, and, in response to that the zero moment point enters the landed polygon formed from the soles, the links are taken off from said shoulder pitch axes to said knee pitch axes while the zero moment point is kept accommodated in the landed polygon to expand the non-landed links in the lengthwise direction to stand said body uprightly.

43. A motion controlling method for a legged mobile robot according to claim 42, characterized in that, at the step of expanding the non-landed links in the lengthwise direction, said knee joint pitch axes having a comparatively great mass operation amount are used positively for the operation.

44. A motion controlling method for a legged mobile robot according to claim 28, characterized in that, at the step of producing a narrower landed polygon, one of a step changing motion and a dragging motion on the floor of the hand parts or the foot parts is selectively utilized in response to whether it is possible to take off two or more of the links which do not relate to the smallest support polygon from the floor to form a narrower landed polygon.

45. A legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, comprising: external force detection means for detecting application of an external force to a body of said legged mobile robot; zero moment point trajectory planning means for disposing a zero moment point at which moments applied to said body balance each other on or on the inner side of a side of a support polygon formed from a sole landed point and a floor based on a result of the detection by said external force detection means; and tumbling motion execution means for executing a tumbling motion of said body in response to that the disposition of the zero moment point in the support polygon by said zero moment point trajectory planning means is rendered difficult or impossible by the external force applied to said body.

46. A legged mobile robot according to claim 45, characterized in that said external force detection means detects the external force applied to said body using a floor reactive force sensor or an acceleration sensor disposed on each of the soles or an acceleration sensor disposed at a position of the waist of the body.

47. A motion controlling method for a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, comprising: an external force detection step of detecting application of an external force to a body of said legged mobile robot; a zero moment point trajectory planning step of disposing a zero moment point at which moments applied to said body balance each other on or on the inner side of a side of a support polygon formed from a sole landed point and a floor based on a result of the detection at the external force detection step; and a tumbling motion execution step of executing a tumbling motion of said body in response to that the disposition of the zero moment point in the support polygon by said zero moment point trajectory planning means is rendered difficult or impossible by the external force applied to said body.

48. A motion controlling method for a legged mobile robot according to claim 47, characterized in that, at the external force detection step, the external force applied to said body is detected using a floor reactive force sensor or an acceleration sensor disposed on each of the soles or an acceleration sensor disposed at a position of the waist of the body.

49. A motion controlling apparatus for a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, comprising: means for calculating an impact moment applied to a body of said legged mobile robot at each stage upon tumbling of said body; means for calculating an impact force applied to said body from the floor at each stage upon tumbling; means for calculating an area S of a support polygon formed from a landed point of said body and the floor; first landed location searching means for selecting a next landed location so that the area S of the support polygon may be minimized or fixed; and second landed location searching means for selecting a next landed location so that the area S of the support polygon may be increased.

50. A motion controlling apparatus for a legged mobile robot according to claim 49, characterized in that a tumbling motion of said body is performed by said second landed location searching means if the impact force applied to said body from the floor is within a predetermined tolerance, but a tumbling motion of said body is performed by said first landed location searching means if the impact force is outside the predetermined tolerance.

51. A motion controlling method for a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, comprising: a step of calculating an impact moment applied to a body of said legged mobile robot at each stage upon tumbling of said body; a step of calculating an impact force applied to said body from the floor at each stage upon tumbling; a step of calculating an area S of a support polygon formed from a landed point of said body and the floor; a first landed location searching step of selecting a next landed location so that the area S of the support polygon may be minimized or fixed; and a second landed location searching step of selecting a next landed location so that the area S of the support polygon may be increased.

52. A motion controlling method for a legged mobile robot according to claim 51, characterized in that a tumbling motion of said body is performed by the second landed location searching step if the impact force applied to said body from the floor is within a predetermined tolerance, but a tumbling motion of said body is performed by the first landed location searching step if the impact force is outside the predetermined tolerance.

53. A motion controlling apparatus for controlling a series of motions relating to tumbling and standing up of a body of a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, characterized in that said legged mobile robot is formed from a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, and said motion controlling apparatus comprises: means for searching for the narrowest support polygon formed from a minimum number of links from among landed polygons formed from landed links in an on-floor posture wherein two or more links including a gravity center link at which the center of gravity of said body is positioned are landed on a floor upon tumbling of said legged mobile robot; means for setting a zero moment point at a location at which the number of links which do not relate to the smallest support polygon is maximized to perform a tumbling motion; means for searching for a link or links which can be taken off from the floor in the tumbling posture of said body; and means for taking off all of the links which can be taken off from the floor to perform a standing up motion.

54. A motion controlling method for controlling a series of motions relating to tumbling and standing up of a body of a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, characterized in that said legged mobile robot is formed from a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, and said motion controlling method comprises the steps of: searching for the narrowest support polygon formed from a minimum number of links from among landed polygons formed from landed links in an on-floor posture wherein two or more links including a gravity center link at which the center of gravity of said body is positioned are landed on a floor upon tumbling of said legged mobile robot; setting a zero moment point at a location at which the number of links which do not relate to the smallest support polygon is maximized to perform a tumbling motion; searching for a link or links which can be taken off from the floor in the tumbling posture of said body; and taking off all of the links which can be taken off from the floor to perform a standing up motion.

55. A robot apparatus having a trunk part, leg parts connected to said trunk part and arm parts connected to said trunk part, comprising: support polygon detection means for detecting a first support polygon formed from a plurality of end portions of said leg parts, trunk part and/or arm parts at which said leg parts, trunk part and/or arm parts are landed on a floor; support polygon changing means for bending said leg parts toward said trunk part to reduce the area of the first support polygon; zero moment point motion controlling means for determining whether or not a zero moment point which is positioned in the changed first support polygon can be moved into a landed polygon formed from the soles of said leg parts; and control means for moving, when said zero moment point motion controlling means determines that the zero moment point can be moved, the zero moment point from within the first support polygon into the landed polygon formed by the soles and changing the posture of said robot apparatus from a tumbling posture to a basic posture while the zero moment point is maintained within the landed polygon.

56. A robot apparatus which includes at least a body, one or more arm links connected to an upper portion of said body each through a first joint (shoulder), a first leg link connected to a lower portion of said body through a second joint (hip joint), and a second leg link connected to an end of said second leg link through a third joint (knee), comprising: means for landing ends of said arm links and a foot part at an end of said second leg link to form a first support polygon; means for moving said second joint upwardly higher than said third joint in a normal direction to the floor while the ends of said arm links and said foot part are kept landed, decreasing the area of the first support polygon and moving a zero moment point into a landed polygon formed from said foot part; and means for standing a body of said robot apparatus uprightly while the zero moment point is kept in the landed polygon formed from said foot part.

Description

TECHNICAL FIELD

The present invention relates to a motion controlling apparatus and a motion controlling method for a legged mobile robot having a great number of joint degrees of freedom, and a robot apparatus, and more particularly to a motion controlling apparatus and a motion controlling method for a legged mobile robot which includes a plurality of movable legs and has a basic standing posture, and a robot apparatus.

More specifically, the present invention relates to a motion controlling apparatus and a motion controlling method for a legged mobile robot wherein a ZMP (Zero Moment Point) is used as a posture stability determination criterion to stabilize and control the position of the body during movement, and more particularly to a motion controlling apparatus and a motion controlling method for a legged mobile robot wherein the damage which may otherwise be given to the robot is reduced as far as possible by motion control of the entire body during tumbling (fall down) or dropping and a standing posture is restored from an on-floor posture such as a supine posture or a prone posture by a stable motion with comparatively low torque, and a robot apparatus.

BACKGROUND ART

A mechanical apparatus which performs movements similar to motions of a human being using mechanical or magnetic actions is called "robot". It is said that the word "robot" originates from a word `ROBOTA` (slave machine) of a Slavic language. Here in Japan, robots began to be popularized at the end of the nineteen sixties. Most of them, however, were industrial robots such as manipulators or transport robots intended for automation and unmanning of manufacturing works in a factory.

Recently, research and development regarding legged mobile robots such as pet type robots which copy body mechanisms and motions of animals that perform four-leg walking like a dog or a cat, or robots (humanoid robot) called "human-type" or "humanoid" robots which are designed by modeling body mechanisms and motions of animals which perform bipedal upright walking such as a human being have proceeded, and also expectation that they be placed into practical use is increasing.

The significance in research and development of legged mobile robots of bipedal locomotion type called human-like or humanoid robots can be grasped, for example, from the following two points of view.

One of them is a human scientific point of view. In particular, a mechanism of a natural motion of a human being beginning with walking can be clarified in an engineering sense through a process that a robot having a structure similar to the lower limbs and/or the upper limbs of a human being is produced and a controlling method for the robot is devised to simulate a walking motion of a human being. It is expected that results of such research can be fed back significantly to the progress in various other research fields which handle a movement mechanism of a human being such as the human engineering, rehabilitation engineering or sports engineering.

Another point is development of a robot for practical use which supports the life of a human being as a partner of the human being, that is, which supports human activities in dwelling environments and other various scenes in everyday life. It is necessary for a robot of the type just described to learn a method of adaptation to human beings having individually different identities and to environments while being taught by human beings in various phases of life environments of human beings. It is considered that, in this instance, if the robot is a "human type" robot, that is, if the robot has a same configuration or a same structure as that of the human being, then the robot functions effectively in smooth communication between a human being and the robot.

For example, in such a case that it is tried to actually teach to a robot a method of passing through a room while bypassing an obstacle which must be kept off, where the robot which is an object of teaching is a bipedal locomotion robot having a similar configuration to that of a user (operator), it is much easier for the user to teach the robot and also it is easier for the robot to learn than where the robot has a structure quite different from the user such as a crawler type robot or a four-legged robot (refer to, for example, TAKANISHI, "Control of a Bipedal locomotion Robot", the Kanto Branch of the Society of Automotive Engineers of Japan <Koso>, No. 25, 1996 APRIL).

A great number of proposals have been made for a technique for posture control or stable walking relating to a robot of the type which performs legged movement by bipedal locomotion. The stable "walking" here can be defined as "traveling without tumbling through use of the legs".

Posture stabilization control of a robot is very important in order to prevent tumbling of a robot. This is because tumbling of a robot signifies interruption of a work being performed and considerable labor and time are required until the robot stands up uprightly from the tumbling state and resumes the work. Above all, there is the possibility that the tumbling may critically damage the robot body itself or also damage a substance with which the tumbling robot collides. Accordingly, in research and development of legged mobile robots, posture stabilization control upon walking or upon any other legged operation is considered one of the most significant technical subjects.

Upon walking of a robot, the gravity and the force of inertia and moments of them originating from the gravity and an acceleration generated by the walking movement act from the walking system of the robot upon the road surface. According to the "d'Alembert's principle", they are balanced with a floor reactive force and a floor reactive force moment as a reaction from the road surface to the walking system. As a consequence of mechanical inference, a point at which the pitch axis moment and the roll axis moment are zero, that is, a "ZMP (Zero Moment Point)", is present on or on the inner side of a side of a support polygon formed by landed points (contact points) of the soles and the road surface.

Most of proposals regarding posture stabilization control of legged mobile robots and prevention of tumbling upon walking uses the ZMP as a criterion for determination of the stability of walking. Production of a bipedal locomotion pattern based on the ZMP criterion is advantageous in that a sole landing point can be set in advance and it is easy to take a kinetic restriction condition of the sole according to a shape of the road surface into consideration. Further, to adopt the ZMP as a stability determination criterion does not signify to handle not a force but a trajectory as a target value on motion control, and therefore, it technically raises the feasibility. It is to be noted that a concept of the ZMP and application of the ZMP to a stability determination criterion for a walking robot are disclosed in Miomir Vukobratovi'c, "LEGGED LOCOMOTION ROBOTS" (Ichiro KATO et al., "Walking Robot and Artificial Feet", the Nikkan Kogyo Shimbun, Ltd.).

Normally, a bipedal locomotion robot such as a humanoid robot is higher in the position of the center of gravity and narrower in the ZMP stable region upon walking than a four-legged walking robot. Accordingly, the problem of a posture variation caused by a variation of the road surface condition is significant particularly with a bipedal locomotion robot.

Several proposals are already available which use the ZMP as a posture stability determination criterion for a bipedal locomotion robot.

For example, a legged mobile robot disclosed in Japanese Patent Laid-Open No. Hei 5-305579 performs stable walking by making a point on a floor at which a ZMP is zero coincide with a target value.

Meanwhile, another legged mobile robot disclosed in Japanese Patent Laid-Open No. Hei 5-305581 is configured such that a ZMP is positioned in the inside of a supporting polyhedron (polygon) or, upon landing or upon taking off, the ZMP is positioned at a position having at least a predetermined margin from an end portion of the support polygon. In this instance, even if the legged mobile robot is subject to some disturbance, it has a margin for the ZMP by the predetermined distance, and the stability of the body upon walking is improved.

Further, Japanese Patent Laid-Open No. Hei 5-305583 discloses that the walking speed of a legged mobile robot is controlled depending upon a ZMP target position. In particular, walking pattern data set in advance is used, and a leg part joint is driven so that a ZMP may coincide with a target position whereas a slope of the upper part of the body is detected and the discharging rate of the set walking pattern data is changed in response to the detection value. If the robot steps on an unknown concave or convex place and tilts forwardly, then the posture thereof can be restored by raising the discharging rate. Further, since the ZMP is controlled to the target position, there is no trouble even if the discharging rate is changed within a double support phase.

Japanese Patent Laid-Open No. Hei 5-305585 discloses that the landing position of a legged mobile robot is controlled in accordance with a ZMP target position. In particular, the legged mobile robot disclosed in the patent document mentioned detects a displacement between a ZMP target position and an actually measured position and drives one or both of the leg parts so that the displacement may be canceled. Or, the legged mobile robot detects a moment around a ZMP target position and drives the leg parts so that the moment may be reduced zero. The legged mobile robot thereby achieves stabilized walking.

Japanese Patent Laid-Open No. Hei 5-305586 discloses that a tilting posture of a legged mobile robot is controlled in accordance with a ZMP target position. In particular, a moment around a ZMP target position is detected, and if a moment appears, then the leg parts are driven so that the moment may be reduced to zero thereby to achieve stabilized walking.

Posture stabilization control of a robot which adopts a ZMP as a stability determination criterion basically resides in search for a point at which a moment is zero on or on the inner side of a side of a support polygon formed from landed points of the soles and the road surface.

As described hereinabove, for a legged mobile robot, possible much effort has been made to prevent the robot from tumbling during walking or during execution of some other motion pattern by taking such a countermeasure as to introduce a ZMP as a posture stabilization criterion.

Naturally, the state of tumbling of a robot signifies interruption of a work being performed by the robot and considerable labor and time are required until the robot stands up uprightly from the tumbling state and resumes the work. Further, there is the possibility that, above all, the tumbling may critically damage the robot body itself or also damage a substance with which the tumbling robot collides.

Although the possible best posture stabilization control is performed in order to prevent tumbling of a robot, the robot may still lose its stability in posture because of some defect in control, some unpredictable external factor (such as, for example, accidental collision with another substance, a road surface situation such as a projection or a depression on the floor, appearance of an obstacle or the like) to such a degree that it cannot be supported only with the movable legs thereof, resulting in tumbling.

Particularly in the case of a robot which performs bipedal legged traveling such as a human-type robot, since the position of the center of gravity is high and an uprightly standing stationary state itself of the robot is originally instable, the robot is likely to tumble. If the robot tumbles, then there is the possibility that critical damage may be applied to the robot itself or to the other party side with which the robot collides by the tumbling.

For example, Japanese Patent Laid-Open No. Hei 11-48170 discloses a control apparatus for a legged mobile robot by which, when the legged mobile robot is in a situation wherein it seems to tumble, the damage which may be given to the robot by the tumbling or the damage to the other party side with which the robot may collide upon the tumbling can be reduced as far as possible.

However, the patent document merely proposes control by which the center of gravity of the robot when landing upon tumbling is merely lowered, but does not make such an argument that, in order to minimize the possible damage when the robot actually tumbles, in what manner the entire body including not only the leg parts but also the body and the arm parts should operate.

In the case of a legged mobile robot of the uprightly standing walking type, a posture which makes a reference when a movement of a body such as walking is taken into consideration is a standing posture in which the robot stands uprightly with the two feet. For example, a state in which the robot is most stable among various standing postures (that is, a point at which the instability is in the minimum) can be positioned as a basic standing posture.

Such a basic standing posture as just described requires generation of torque by joint axis motors for the leg parts and so forth by execution of posture stabilization control and control instruction. In other words, in a no-power supply condition, no standing posture is stable. Therefore, it is considered preferable that the robot starts activation thereof from an on-floor posture in which the robot is physically most stable such as a supine posture or a prone posture.

However, even if power supply to the robot in such an on-floor posture as just described is made available, if the robot cannot stand up autonomously, then an operator must give a hand to lift the body, which is cumbersome to the operator.

Further, when the robot once assumes a standing posture and performs walking or some other autonomous legged operation, it basically makes an effect to travel using the legs without tumbling. However, the robot may sometimes tumble unfortunately. "Tumbling" is inevitable when a robot operates under dwelling environments of human beings which involve various obstacles and unforeseeable situations. In the first place, a human being also tumbles. Also in this instance, it still is cumbersome if an operator must give a hand to lift the body.

If the robot cannot stand up by itself every time it assumes an on-floor posture, then it cannot be operated in unmanned environments after all, and the operation lacks in self-conclusion. Thus, the robot cannot be placed into fully self-contained environments.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a superior legged mobile robot and a superior tumbling motion (fall down motion) controlling method for a legged mobile robot by which damage which may otherwise be given to the robot can be reduced as far as possible by motion control of an entire body including not only the leg parts but also the body and the arm parts during tumbling and dropping.

It is another object of the present invention to provide a superior motion controlling apparatus and motion controlling method for a legged mobile robot and a superior robot apparatus by which the robot can autonomously restore its standing posture from an on-floor posture such as a supine posture or a prone posture.

It is a further object of the present invention to provide a superior motion controlling apparatus and motion controlling method for a legged mobile robot and a superior robot apparatus by which the robot can restore its standing posture from an on-floor posture such as a supine posture or a prone posture through a stabilized motion with comparatively low torque.

The present invention has been made in view of the subjects described above, and according to a first aspect of the present invention, there is provided a motion controlling apparatus or a motion controlling method for a legged mobile robot which includes movable legs and performs a legged operation in a standing posture thereof, characterized in that

the legged mobile robot has a plurality of positions or states, and that

the motion controlling apparatus or method includes:

first means for or a first step of calculating an area S of a support polygon formed from landed points (contact points to the floor) of a body of the legged mobile robot and a floor;

second means for or a second step of calculating the variation .DELTA.S/.DELTA.t of the area S of the support polygon per time .DELTA.t; and

third means for or a third step of determining a motion of the body when the position or state is to be changed based on the area S of the support polygon or the variation rate .DELTA.S/.DELTA.t of the area S.

In many legged mobile robots, a ZMP is utilized as a stability determination criterion so that the posture stability of the body within a period of a particular legged operation such as walking may be maintained. With the motion controlling apparatus or the motion controlling method for a legged mobile robot according to the first aspect of the present invention, when the robot changes the posture or the state thereof such as when the robot which is in a walking or uprightly standing state or when the robot stands up from a horizontally lying position after tumbling or the like, the motion pattern of the body is successively determined based on the area S of the support polygon formed by the landed points of the body and the floor or the variation rate .DELTA.S/.DELTA.t of the area S. By this, a tumbling motion or a standing up motion can be realized such that they may be performed more efficiently with a reduced load.

Here, the third means or step may include:

landed location searching means (means for searching contacting part) for or a landed location searching step (step of searching contacting part) of searching for a landed location (part) upon tumbling of the legged mobile robot based on the variation per time .DELTA.t of the area S of the support polygon formed from the landed points of the body and the floor;

target landing point (target contacting point) setting means for or a target landing point setting step of setting a target landing point at which the location selected by the landed location searching means should be landed (contacting to the floor) so that the variation .DELTA.S/.DELTA.t per time .DELTA.t of the area S of the support polygon formed from the landed points of the body and the floor may be minimized; and

location landing means for landing the location selected by the landed portion searching means or at the landed portion searching step, at the target landing point set by the target landing point setting means or at the target landing point setting step.

While the legged mobile robot performs a legged operation in the standing posture, it detects an external force applied to the body by means of floor reactive force sensors, acceleration sensors disposed on (mounted on) the soles or acceleration sensors disposed at the position of the waist of the body or the like. Then, the legged mobile robot establishes a ZMP balance equation based on the thus detected external forces to normally plan a ZMP trajectory so that a ZMP at which moments applied to the body balance with each other may be disposed on or on the inner side of a side of the support polygon formed from the landed points of the soles and the floor to perform posture stabilization control.

However, if a moment error on the ZMP balance equation cannot be canceled due to such a situation that the external force applied to the body is excessively high or the situation of the road surface is not favorable, then it sometimes becomes difficult or impossible to dispose the ZMP in the support polygon in accordance with the ZMP trajectory plan. In such an instance, the legged mobile robot according to the present invention gives up the posture stabilization control of the body and executes a predetermined tumbling motion to minimize the damage to the body upon dropping onto the floor.

In particular, upon tumbling, the legged mobile robot searches for a location (part) at which the variation .DELTA.S/.DELTA.t per time .DELTA.t of the area S of the support polygon formed from the landed points of the body and the floor is minimized and sets a target landing point at which the selected location should be landed so that the variation .DELTA.S/.DELTA.t per time .DELTA.t of the area S of the support polygon formed from the landed points of the body and the floor may be minimized, and then lands the location onto the floor. Then, the legged mobile robot further expands the support polygon formed newly by the landing.

Then, the legged mobile robot repetitively executes the motion of searching for a location at which the variation .DELTA.S/.DELTA.t is minimized and landing the location at the target landing point at which the variation .DELTA.S/.DELTA.t is minimized and the motion of expanding the newly formed support polygon until after the potential energy of the body becomes minimum and the tumbling motion comes to an end.

Where the variation .DELTA.S/.DELTA.t per time .DELTA.t of the area S of the support polygon is minimized and the support polygon upon dropping onto the floor is maximized in this manner, the impact applied from the floor upon dropping can be dispersed to the whole body thereby to suppress the damage to the body to the minimum. Where the legged mobile robot is regarded as a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, moderation of the impact force can be achieved by setting a location at which a link with which the number of non-landed links (non-contacting to the floor) is maximized exists as a target.

Further, the legged mobile robot may be formed from, for example, a link structure wherein a plurality of substantially parallel joint axes having a joint degree-of-freedom are connected to each other in a lengthwise direction, and

the third means or step may include:

means for or a step of searching, when the legged mobile robot returns from its tumbling state, for the narrowest support polygon formed from the least number of links from among landed polygons (contacting to the floor) formed, in an on-floor posture of the legged mobile robot in which two or more links including a gravity center link positioned at the center of gravity of the body are landed on (contacted to) the floor, from the landed links (contacting to the floor);

means for or a step of taking off the landed links in the landed polygons except those of the searched out support polygon;