Foothold position control system and method for biped robot

A control method of a foothold position control system for a biped robot, wherein the foothold position control system comprises a laser radar or vision sensor, a gyroscope, a six-component force sensor, and an industrial computer, wherein a fuzzy controller in the industrial computer separately uses xsd, xen, ysd, yen, θsd, and θpt as inputs and performs fuzzy processing to obtain a specific foothold position of a swing foot in an available foothold area, wherein xsd, ysd is a real-time position of a support foot of a biped robot obtained by the six-component force sensor, xen, yen is a position of an obstacle in a robot body coordinate system obtained by the laser radar or vision sensor, θsd is an initial yaw angle of the biped robot obtained by the gyroscope, and θpt is an angle between a straight line formed by a current path node and an associated path node in a next step and an x axis of a world coordinate system;

• wherein the control method comprising:
• planning a passing path;
• determining the available foothold area of the swing foot on the passing path according to step-length constraints, movement capabilities, foot sizes, and center offsets of the biped robot;
• and
• performing fuzzy processing to determine a specific foothold position of the biped robot;
• wherein the fuzzy processing comprises fuzzification, fuzzy rule reasoning, and defuzzification;
• wherein a process of the fuzzy processing on yen and ysd is:
• inputting ypt−ypt−1 and yen, and outputting Δynext;
• (1) fuzzification
• fuzzifying ypt−ypt−1 as inward, small swing outward, medium swing outward, and big swing outward, with corresponding ranges being respectively
• [
• L
• min
• ,
• B
• ]
• ,
• [
• B
• ,
• B
• +
• 1
• 2
• ⁢
• (
• L
• max
• -
• B
• )
• ]
• ,
• [
• B
• +
• 1
• 3
• ⁢
• (
• L
• max
• -
• B
• )
• ,
• B
• +
• 2
• 3
• ⁢
• (
• L
• max
• -
• B
• )
• ]
• ,
• and
• [
• B
• +
• 1
• 2
• ⁢
• (
• L
• max
• -
• B
• )
• ,
• L
• max
• ]
• ;
• fuzzifying yen as very near, near, medium, far, and very far, with corresponding ranges being respectively
• [
• L
• max
• ,
• 2
• ⁢
• L
• max
• ]
• ,
• [
• 3
• 2
• ⁢
• L
• max
• ,
• 5
• 2
• ⁢
• L
• max
• ]
• ,
• [
• 2
• ⁢
• L
• max
• ,
• 3
• ⁢
• L
• max
• ]
• ,
• [
• 5
• 2
• ⁢
• L
• max
• ,
• 7
• 2
• ⁢
• L
• max
• ]
• ,
• and
• [
• 3
• ⁢
• L
• max
• ,
• 4
• ⁢
• L
• max
• ]
• ;
• fuzzifying Δynext as inward, small, medium, and large, with corresponding ranges being respectively
• [
• L
• min
• ,
• B
• ]
• ,
• [
• B
• ,
• B
• +
• 1
• 2
• ⁢
• (
• L
• max
• -
• B
• )
• ]
• ,
• [
• B
• +
• 1
• 3
• ⁢
• (
• L
• max
• -
• B
• )
• ,
• B
• +
• 2
• 3
• ⁢
• (
• L
• max
• -
• B
• )
• ]
• ,
• and
• [
• B
• +
• 1
• 2
• ⁢
• (
• L
• max
• -
• B
• )
• ,
• L
• max
• ]
• ;
• wherein Lmax is a maximum outward movable distance, Lmin is a maximum inward movable distance, and B is a distance between projections of centers of gravity of two legs when the biped robot stands upright;
• (2) fuzzy rule reasoning
• if ypt−ypt−1=inward, then Δynext=inward;
• if ypt−ypt−1=small swing outward, and yen=very near, then Δynext=small;
• if ypt−ypt−1=small swing outward, and yen=near, then Δynext=small;
• if ypt−ypt−1=small swing outward, and yen=medium, then Δynext=medium;
• if ypt−ypt−1=small swing outward, and yen=far, then Δynext=large;
• if ypt−ypt−1=small swing outward, and yen=very far, then Δynext=large;
• if ypt−ypt−1=medium swing outward, and yen=very near, then Δynext=small;
• if ypt−ypt−1=medium swing outward, and yen=near, then Δynext=small;
• if ypt−ypt−1=medium swing outward, and yen=medium, then Δynext=medium;
• if ypt−ypt−1=medium swing outward, and yen=far, then Δynext=large;
• if ypt−ypt−1=medium swing outward, and yen=very far, then Δynext=large;
• if ypt−ypt−1=big swing outward, and yen=very near, then Δynext=small;
• if ypt−ypt−1=big swing outward, and yen=near, then Δynext=small;
• if ypt−ypt−1=big swing outward, and yen=medium, then Δynext=medium;
• if ypt−ypt−1=big swing outward, and yen=far, then Δynext=large;
• if ypt−ypt−1=big swing outward, and yen=very far, then Δynext=large;
• and
• (3) defuzzification using a centroid method
• Δ
• ⁢
• y
• n
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• ⁢
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• ⁢
• t
• =
• (
• y
• p
• ⁢
• t
• -
• y
• pt
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• ⁢
• μ
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• p
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• t
• -
• y
• pt
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• 1
• +
• y
• e
• ⁢
• n
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• μ
• y
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• n
• μ
• y
• p
• ⁢
• t
• ⁢
• y
• pt
• -
• 1
• +
• μ
• y
• e
• ⁢
• n
• wherein u is a membership value.

A control method of a foothold position control system for a biped robot, wherein the foothold position control system comprises a laser radar or vision sensor, a gyroscope, a six-component force sensor, and an industrial computer, wherein a fuzzy controller in the industrial computer separately uses xsd, xen, ysd, yen, θsd, and θpt as inputs and performs fuzzy processing to obtain a specific foothold position of a swing foot in an available foothold area, wherein xsd, ysd is a real-time position of a support foot of a biped robot obtained by the six-component force sensor, xen, yen is a position of an obstacle in a robot body coordinate system obtained by the laser radar or vision sensor, θsd is an initial yaw angle of the biped robot obtained by the gyroscope, and θpt is an angle between a straight line formed by a current path node and an associated path node in a next step and an x axis of a world coordinate system;

• wherein the control method comprising:
• planning a passing path;
• determining the available foothold area of the swing foot on the passing path according to step-length constraints, movement capabilities, foot sizes, and center offsets of the biped robot;
• and
• performing fuzzy processing to determine a specific foothold position of the biped robot;
• wherein the fuzzy processing comprises fuzzification, fuzzy rule reasoning, and defuzzification;
• wherein a process of the fuzzy processing on θsd and θpt is:
• inputting θsd and θpt, and outputting Δθnext;
• (1) fuzzification
• fuzzifying θsd as inward yaw, small-amplitude outward yaw, medium-amplitude outward yaw, and large-amplitude outward yaw, with corresponding ranges being respectively
• [
• -
• θ
• min
• ,
• 0
• ]
• ,
• [
• 0
• ,
• 1
• 2
• ⁢
• θ
• max
• ]
• ,
• [
• 1
• 3
• ⁢
• θ
• max
• ,
• 2
• 3
• ⁢
• θ
• max
• ]
• ,
• and
• [
• 1
• 2
• ⁢
• θ
• max
• ,
• θ
• max
• ]
• ;
• fuzzifying θpt as negative big orientation, negative small orientation, medium, positive small orientation, and positive big orientation, with corresponding ranges being respectively
• [
• -
• π
• 2
• ,
• -
• π
• 4
• ]
• ,
• [
• -
• π
• 3
• ,
• -
• π
• 6
• ]
• ,
• [
• -
• π
• 4
• ,
• π
• 4
• ]
• ,
• [
• π
• 6
• ,
• π
• 3
• ]
• ,
• and
• [
• π
• 4
• ,
• π
• 2
• ]
• ;
• fuzzifying Δθnext as inward yaw, small-amplitude outward yaw, medium-amplitude outward yaw, and large-amplitude outward yaw, with corresponding ranges being respectively
• [
• -
• θ
• min
• ,
• 0
• ]
• ,
• [
• 0
• ,
• 1
• 2
• ⁢
• θ
• max
• ]
• ,
• [
• 1
• 3
• ⁢
• θ
• max
• ,
• 2
• 3
• ⁢
• θ
• max
• ]
• ,
• and
• [
• 1
• 2
• ⁢
• θ
• max
• ,
• θ
• max
• ]
• ;
• wherein θmin is a maximum inward yaw angle of the swing foot, and θmax is a maximum outward yaw angle of the swing foot;
• (2) fuzzy rule reasoning
• when the support foot is a left foot:
• if θsd=inward yaw, and θpt=negative big orientation, then Δθnext=large-amplitude outward yaw;
• if θsd=inward yaw, and θpt=negative small orientation, then Δθnext=medium-amplitude outward yaw;
• if θsd=inward yaw, and θpt=medium, then Δθnext=small-amplitude outward yaw;
• if θsd=inward yaw, and θpt=positive small orientation, then Δθnext=inward yaw;
• if θsd=inward yaw, and θpt=positive big orientation, then Δθnext=inward yaw;
• if θsd=small-amplitude outward yaw, and θpt=negative big orientation, then Δθnext=large-amplitude outward yaw;
• if θsd=small-amplitude outward yaw, and θpt=negative small orientation, then Δθnext=medium-amplitude outward yaw;
• if θsd=small-amplitude outward yaw, and θpt=medium, then Δθnext=small-amplitude outward yaw;
• if θsd=small-amplitude outward yaw, and θpt=positive small orientation, then Δθnext=inward yaw;
• if θsd=small-amplitude outward yaw, and θpt=positive big orientation, then Δθnext=inward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=negative big orientation, then Δθnext=large-amplitude outward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=negative small orientation, then Δθnext=medium-amplitude outward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=medium, then Δθnext=inward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=positive small orientation, then Δθnext=inward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=positive big orientation, then Δθnext=inward yaw;
• if θsd=large-amplitude outward yaw, and θpt=negative big orientation, then Δθnext=medium-amplitude outward yaw;
• if θsd=large-amplitude outward yaw, and θpt=negative small orientation, then Δθnext=small-amplitude outward yaw;
• if θsd=large-amplitude outward yaw, and θpt=medium, then Δθnext=inward yaw;
• if θsd=large-amplitude outward yaw, and θpt=positive small orientation, then Δθnext=inward yaw;
• if θsd=large-amplitude outward yaw, and θpt=positive big orientation, then Δθnext=inward yaw;
• when the support foot is a right foot:
• if θsd=inward yaw, and θpt=negative big orientation, then Δθnext=inward yaw;
• if θsd=inward yaw, and θpt=negative small orientation, then Δθnext=inward yaw;
• if θsd=inward yaw, and θpt=medium, then Δθnext=small-amplitude outward yaw;
• if θsd=inward yaw, and θpt=positive small orientation, then Δθnext=medium-amplitude outward yaw;
• if θsd=inward yaw, and θpt=positive big orientation, then Δθnext=large-amplitude outward yaw;
• if θsd=small-amplitude outward yaw, and θpt=negative big orientation, then Δθnext=inward yaw;
• if θsd=small-amplitude outward yaw, and θpt=negative small orientation, then Δθnext=inward yaw;
• if θsd=small-amplitude outward yaw, and θpt=medium, then Δθnext=small-amplitude outward yaw;
• if θsd=small-amplitude outward yaw, and θpt=positive small orientation, then Δθnext=medium-amplitude outward yaw;
• if θsd=small-amplitude outward yaw, and θpt=positive big orientation, then Δθnext=large-amplitude outward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=negative big orientation, then Δθnext=inward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=negative small orientation, then Δθnext=inward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=medium, then Δθnext=inward yaw;
• if ∝sd=medium-amplitude outward yaw, and θpt=positive small orientation, then Δθnext=small-amplitude outward yaw;
• if θsd=medium-amplitude outward yaw, and θpt=positive big orientation, then Δθnext=medium-amplitude inward yaw;
• if θsd=large-amplitude outward yaw, and θpt=negative big orientation, then Δθnext=inward yaw;
• if θsd=large-amplitude outward yaw, and θpt=negative small orientation, then Δθnext=inward yaw;
• if θsd=large-amplitude outward yaw, and θpt=medium, then Δθnext=inward yaw;
• if θsd=large-amplitude outward yaw, and θpt=positive small orientation, then Δθnext=small-amplitude outward yaw;
• if θsd=large-amplitude outward yaw, and θpt=positive big orientation, then Δθnext=medium-amplitude inward yaw;
• and
• (3) defuzzification
• defuzzification using a centroid method:
• Δ
• ⁢
• θ
• next
• =
• θ
• p
• ⁢
• t
• ⁢
• μ
• θ
• p
• ⁢
• t
• +
• θ
• s
• ⁢
• d
• ⁢
• μ
• θ
• sd
• μ
• θ
• p
• ⁢
• t
• +
• μ
• θ
• sd
• wherein u is a membership value.