rigidBodyTree是什麼(附使用例子和代碼)

介紹

rigidBodyTree是較新版本的MATLAB(小虎用的是2019b)自帶的robotics相關工具箱裏面的一個剛體樹。它可以實現簡單機器人剛體關節的連接仿真,這是在創建模型中使用的。其他詳情見官方說明。

將連桿加入剛體樹

rbtree=rigidBodyTree;
body1=rigidBody('b1');

jnt1=rigidBodyJoint('jnt1','revolute');
body1.Joint=jnt1;

basename=rbtree.BaseName;
addBody(rbtree,body1,basename);

showdetails(rbtree);

DH參數添加機器人關節連桿

% first column is the distance between z axis(d), first column is angle
% rotate with x axis(\alpha); third is the distance between x axis (a)
dhparams = [0   	pi/2	0   	0;
            0.4318	0       0       0;
            0.0203	-pi/2	0.15005	0;
            0   	pi/2	0.4318	0;
            0       -pi/2	0   	0;
            0       0       0       0];
robot=rigidBodyTree;

body1 = rigidBody('body1');
jnt1 = rigidBodyJoint('jnt1','revolute');

setFixedTransform(jnt1,dhparams(1,:),'dh');
body1.Joint = jnt1;

addBody(robot,body1,'base')

body2 = rigidBody('body2');
jnt2 = rigidBodyJoint('jnt2','revolute');
body3 = rigidBody('body3');
jnt3 = rigidBodyJoint('jnt3','revolute');
body4 = rigidBody('body4');
jnt4 = rigidBodyJoint('jnt4','revolute');
body5 = rigidBody('body5');
jnt5 = rigidBodyJoint('jnt5','revolute');
body6 = rigidBody('body6');
jnt6 = rigidBodyJoint('jnt6','revolute');

setFixedTransform(jnt2,dhparams(2,:),'dh');
setFixedTransform(jnt3,dhparams(3,:),'dh');
setFixedTransform(jnt4,dhparams(4,:),'dh');
setFixedTransform(jnt5,dhparams(5,:),'dh');
setFixedTransform(jnt6,dhparams(6,:),'dh');

body2.Joint = jnt2;
body3.Joint = jnt3;
body4.Joint = jnt4;
body5.Joint = jnt5;
body6.Joint = jnt6;

addBody(robot,body2,'body1')
addBody(robot,body3,'body2')
addBody(robot,body4,'body3')
addBody(robot,body5,'body4')
addBody(robot,body6,'body5')

showdetails(robot)

show(robot);
axis([-0.5,0.5,-0.5,0.5,-0.5,0.5])
axis on

修改剛體樹模型

load exampleRobots.mat
showdetails(puma1)

body3=getBody(puma1,'L3');
childBody=body3.Children{1};

body3Copy = copy(body3);
newJoint=rigidBodyJoint('prismatic');
replaceJoint(puma1,'L3',newJoint);

showdetails(puma1)

設置剛體樹動態特性

設置質點的位置。

robot=rigidBodyTree('DataFormat','row');
body1 = rigidBody('body1');
body2 = rigidBody('body2');

joint1 = rigidBodyJoint('joint1','revolute');
joint2 = rigidBodyJoint('joint2');
setFixedTransform(joint2,trvec2tform([1 0 0]))
body1.Joint = joint1;
body2.Joint = joint2;

body1.Mass = 2;
body1.CenterOfMass = [0.5 0 0];
body1.Inertia = [0.167 0.001 0.167 0 0 0];

body2.Mass = 1;
body2.CenterOfMass = [0 0 0];
body2.Inertia = 0.0001*[4 4 4 0 0 0];

addBody(robot,body1,'base');
addBody(robot,body2,'body1');

comPos = centerOfMass(robot);

show(robot);
hold on
plot(comPos(1),comPos(2),'or')
view(2)

body2.Mass = 20;
replaceBody(robot,'body2',body2)

comPos2 = centerOfMass(robot);
plot(comPos2(1),comPos2(2),'*g')
hold off

外力作用導致關節的移動

load exampleRobots.mat lbr
lbr.DataFormat = 'row';
lbr.Gravity = [0 0 -9.81];% z axis direction
q = homeConfiguration(lbr);
wrench=[0 0 0.5 0 0 0.3];
fext=externalForce(lbr,'tool0',wrench,q);
qddot = forwardDynamics(lbr,q,[],[],fext);

載入自帶機器人模型並顯示

robot = importrobot('iiwa14.urdf');
show(robot);