Create a Mechanism with Different Joints in MATLAB

R2026b
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This example shows how to model a mechanism that contains different types of joints in MATLAB®. It also shows a way of setting operating point targets for the joint primitives of the joints.

Create a Multibody object and add the necessary components, such as WorldFrame.

import simscape.Value simscape.multibody.*;

mb = Multibody;
addComponent(mb, 'World', WorldFrame());

sep = Value(20, 'cm'); % Separation between blocks

% Ground plane
ground = UniformSolid(Brick([[5 4] * sep, Value(1, 'cm')]), Value(1000, 'kg/m^3'));
addComponent(mb, 'Ground', ground);
addComponent(mb, 'Ground_Pose', RigidTransform(CartesianTranslation([2 1.5 0] * sep)));
connectVia(mb, 'Ground_Pose', 'World/W', 'Ground/R');

Add different types of joints to the Multibody object using the custom function addJoint.

% Row 1:  Single-primitive joints
addJoint(mb, 'Revolute',         [0 0] * sep,   [1 0 0]);
addJoint(mb, 'Prismatic',        [1 0] * sep,   [1 1 0]);
addJoint(mb, 'Spherical',        [2 0] * sep,   [0 .8 0]);
addJoint(mb, 'LeadScrew',        [3 0] * sep,   [0 0 .9]);
addJoint(mb, 'ConstantVelocity', [4 0] * sep,   [.8 0 .8]);

% Row 2:  2-DOF multi-primitive joints
addJoint(mb, 'Universal',        [0.5 1] * sep, [.95 .4 0]);
addJoint(mb, 'Rectangular',      [1.5 1] * sep, [.4 .9 0]);
addJoint(mb, 'Cylindrical',      [2.5 1] * sep, [0 .7 .7]);
addJoint(mb, 'PinSlot',          [3.5 1] * sep, [.6 0 1]);

% Row 3:  3-DOF and 4-DOF multi-primitive joints
addJoint(mb, 'Gimbal',           [0 2] * sep,   [.37 .86 .57]);
addJoint(mb, 'Cartesian',        [1 2] * sep,   [.28 .55 .96]);
addJoint(mb, 'Planar',           [2 2] * sep,   [.91 .63 .10]);
addJoint(mb, 'Bearing',          [3 2] * sep,   [.96 .49 .80]);
addJoint(mb, 'Telescoping',      [4 2] * sep,   [.8 .8 .5]);

% Row 4:  0-DOF and 6-DOF joints
addJoint(mb, 'Weld',             [1 3] * sep,   .1 * [1 1 1]);
addJoint(mb, 'Bushing',          [2 3] * sep,   .8 * [1 1 1]);
addJoint(mb, 'SixDof',           [3 3] * sep,    1 * [1 1 1]);

Use the custom function randomOpPoint to create an operating point specifying random velocities for all the joints.

op = randomOpPoint(mb, Value(90, 'deg/s'), Value(1, 'cm/s'));

After you create the operating point, compile the Multibody object and use the computeState method to view if the above random velocity targets are achieved.

cmb = compile(mb);
state = computeState(cmb,op)
state = 
  State with properties:

    Status: Valid

To perform any simulation workflows, generate the Simulink® model of the mechanism by using the makeBlockDiagram method.

makeBlockDiagram(mb,op,'jointZooModel');

See Also

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