teeny tiny start to magB

matlab/magnetfield.m

@@ -0,0 +1,65 @@
+function magB = magnetfield(mag,xyz,varargin)
+%MAGNETFIELD Calculate magnetic field from a magnet source
+
+switch mag.type
+
+  case 'cuboid'
+
+    magB = calc_cuboid_field(mag,xyz);
+
+  case 'cylinder'
+
+
+end
+
+end
+
+
+function magB = calc_cuboid_field(mag,xyz)
+
+Br = 1;
+u0 = 4*pi*10^-7 ;   
+
+
+if size(xyz,1) == 3
+elseif size(xyz,2) == 3
+  warning('xyz should be column vectors of position stacked along rows')
+  xyz = transpose(xyz);
+else
+  error('xyz funny size')
+end
+
+X = xyz(1,:);
+Y = xyz(2,:);
+Z = xyz(3,:);
+N = size(X);
+
+x_m = [-mag.dim(1)/2 +mag.dim(1)/2];
+y_m = [-mag.dim(2)/2 +mag.dim(2)/2];
+z_m = [-mag.dim(3)/2 +mag.dim(3)/2];
+
+[ii,jj,kk]=meshgrid(1:2,1:2,1:2);
+%reshape index array for 8 summations and size of field array
+ii=repmat(reshape(ii,[1,1,8]),N);
+jj=repmat(reshape(jj,[1,1,8]),N);
+kk=repmat(reshape(kk,[1,1,8]),N);
+%reshape field array to match index array
+x=ones(N(1),N(2),8).*X;
+y=ones(N(1),N(2),8).*Y;
+z=ones(N(1),N(2),8).*Z;
+%define equation constant D  - ravaud 2009
+D=((-1).^(ii+jj+kk));
+%define equation constant zeta  - ravaud 2009
+zeta = sqrt((x-x_m(ii)+eps).^2+(y-y_m(jj)+eps).^2+(z-z_m(kk)+eps).^2);
+zeta(isnan(zeta))=0;
+
+% +Z magnetisation
+
+Bx = (Br*u0/(4*pi))*sum(D.*-real(log((y-y_m(jj)+eps)+zeta)),3);
+By = (Br*u0/(4*pi))*sum(D.*-real(log((x-x_m(ii)+eps)+zeta)),3);
+Bz = (Br*u0/(4*pi))*sum(D.*(atan(((x-x_m(ii)+eps).*(y-y_m(jj)+eps))./((z-z_m(kk)+eps).*zeta))),3);
+
+magB = sum([Bx;By;Bz],2);
+
+
+end