79 lines
3.2 KiB
Matlab
79 lines
3.2 KiB
Matlab
function [stewart] = computeJointsPose(stewart)
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% computeJointsPose -
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%
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% Syntax: [stewart] = computeJointsPose(stewart)
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%
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% Inputs:
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% - stewart - A structure with the following fields
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% - platform_F.Fa [3x6] - Its i'th column is the position vector of joint ai with respect to {F}
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% - platform_M.Mb [3x6] - Its i'th column is the position vector of joint bi with respect to {M}
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% - platform_F.FO_A [3x1] - Position of {A} with respect to {F}
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% - platform_M.MO_B [3x1] - Position of {B} with respect to {M}
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% - geometry.FO_M [3x1] - Position of {M} with respect to {F}
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%
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% Outputs:
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% - stewart - A structure with the following added fields
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% - geometry.Aa [3x6] - The i'th column is the position of ai with respect to {A}
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% - geometry.Ab [3x6] - The i'th column is the position of bi with respect to {A}
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% - geometry.Ba [3x6] - The i'th column is the position of ai with respect to {B}
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% - geometry.Bb [3x6] - The i'th column is the position of bi with respect to {B}
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% - geometry.l [6x1] - The i'th element is the initial length of strut i
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% - geometry.As [3x6] - The i'th column is the unit vector of strut i expressed in {A}
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% - geometry.Bs [3x6] - The i'th column is the unit vector of strut i expressed in {B}
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% - struts_F.l [6x1] - Length of the Fixed part of the i'th strut
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% - struts_M.l [6x1] - Length of the Mobile part of the i'th strut
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% - platform_F.FRa [3x3x6] - The i'th 3x3 array is the rotation matrix to orientate the bottom of the i'th strut from {F}
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% - platform_M.MRb [3x3x6] - The i'th 3x3 array is the rotation matrix to orientate the top of the i'th strut from {M}
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assert(isfield(stewart.platform_F, 'Fa'), 'stewart.platform_F should have attribute Fa')
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Fa = stewart.platform_F.Fa;
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assert(isfield(stewart.platform_M, 'Mb'), 'stewart.platform_M should have attribute Mb')
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Mb = stewart.platform_M.Mb;
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assert(isfield(stewart.platform_F, 'FO_A'), 'stewart.platform_F should have attribute FO_A')
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FO_A = stewart.platform_F.FO_A;
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assert(isfield(stewart.platform_M, 'MO_B'), 'stewart.platform_M should have attribute MO_B')
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MO_B = stewart.platform_M.MO_B;
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assert(isfield(stewart.geometry, 'FO_M'), 'stewart.geometry should have attribute FO_M')
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FO_M = stewart.geometry.FO_M;
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Aa = Fa - repmat(FO_A, [1, 6]);
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Bb = Mb - repmat(MO_B, [1, 6]);
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Ab = Bb - repmat(-MO_B-FO_M+FO_A, [1, 6]);
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Ba = Aa - repmat( MO_B+FO_M-FO_A, [1, 6]);
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As = (Ab - Aa)./vecnorm(Ab - Aa); % As_i is the i'th vector of As
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l = vecnorm(Ab - Aa)';
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Bs = (Bb - Ba)./vecnorm(Bb - Ba);
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FRa = zeros(3,3,6);
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MRb = zeros(3,3,6);
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for i = 1:6
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FRa(:,:,i) = [cross([0;1;0], As(:,i)) , cross(As(:,i), cross([0;1;0], As(:,i))) , As(:,i)];
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FRa(:,:,i) = FRa(:,:,i)./vecnorm(FRa(:,:,i));
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MRb(:,:,i) = [cross([0;1;0], Bs(:,i)) , cross(Bs(:,i), cross([0;1;0], Bs(:,i))) , Bs(:,i)];
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MRb(:,:,i) = MRb(:,:,i)./vecnorm(MRb(:,:,i));
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end
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stewart.geometry.Aa = Aa;
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stewart.geometry.Ab = Ab;
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stewart.geometry.Ba = Ba;
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stewart.geometry.Bb = Bb;
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stewart.geometry.As = As;
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stewart.geometry.Bs = Bs;
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stewart.geometry.l = l;
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stewart.struts_F.l = l/2;
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stewart.struts_M.l = l/2;
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stewart.platform_F.FRa = FRa;
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stewart.platform_M.MRb = MRb;
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