## Creating a Multibody Model

### Step 1: Study the System to Model

Identify the relevant bodies, joints, and constraints to incorporate in your model. Consider the forces and torques acting between bodies or directly at joints.

### Step 2: Model the Bodies

Specify the solid properties of the various bodies. Add frames to the bodies so that you can connect joints and constraints, apply forces and torques, and sense motion. See Model a Simple Link for an example showing how to model a simple body—one comprising a single solid. See Try It: Create a Compound Geometry for a more elaborate example showing how to model a compound body—one comprising multiple solids.

### Step 3: Assemble the Multibody System

Connect the bodies by pairs through joints. Constrain body motion through gears and other kinematic constraints. See Model an Open-Loop Kinematic Chain for an example showing how to connect bodies through joints. See Model a Compound Gear Train for an example showing how to constrain motion through gears.

### Step 4: Specify and Sense Dynamic Variables

Model external loads, interactions between bodies, and joint actuation inputs. Sense forces, torques, and motion variables as functions of time. See Specify Joint Actuation Torque for an example showing how to specify a joint actuation torque. See Sense Motion Using a Transform Sensor Block for an example showing how to sense frame position using the Transform Sensor block.