We will use the Multibody modeling tools in Simscape to build this model. We will hook up this model to control algorithms developed in Simulink and MATLAB. This model can also be used as a digital twin for the actual robot that I am building for my lab. I will talk about digital twins at length in another post.<\/p>\n\n\n\n
In this post, we are going to build our robot model in a step-by-step fashion, as follows:<\/p>\n\n\n\n
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- Breakdown the model into a hierarchical structure<\/a><\/li>\n\n\n\n
- Arrive at a flow-chart for building the parts<\/a><\/li>\n\n\n\n
- Build steps:\n
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- Passive wheel and axle<\/a><\/li>\n\n\n\n
- Wheel hub assembly<\/a><\/li>\n\n\n\n
- Finish Wheel assembly<\/a><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n
We will attach the wheels to the robot chassis and model the interaction with the ground plane in the next blog entry.<\/p>\n\n\n\n
If you would like to first go take a look at the basics of Multibody modeling in Simscape, follow the link to the documentation. You can find it in the getting started section at the bottom of the page.<\/code>.<\/mark><\/p>\n\n\n\nBreakdown the model into a hierarchical structure<\/h3>\n\n\n\n
Let us start by breaking down the robot assembly into a hierarchical structure. This is how that structure looks conceptually.<\/p>\n\n\n
\n![\"\"](\"https:\/\/i0.wp.com\/siddharthv.com\/wp-content\/uploads\/2024\/04\/breakdown.png?resize=660%2C385&ssl=1\")
Fig 2.1: Hierarchical structure of the omni-directional robot.<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n Arrive at a flow-chart for building the parts<\/h3>\n\n\n\n
Starting out on a modeling project feels daunting when you look at the assembly as a whole. Still, once you have broken it down into smaller parts, it’s easy to see the repetitive elements. You need to model them only once. Also, as we model the smaller parts, the steps become more intuitive. When we assemble them into the next higher order part, the process becomes more straightforward. This is how the flowchart is actually going to look like once we get started.<\/p>\n\n\n
\n![\"\"](\"https:\/\/i0.wp.com\/siddharthv.com\/wp-content\/uploads\/2024\/04\/flowchart-1.png?resize=660%2C168&ssl=1\")
Fig 2.2: Flow-chart for the modeling steps.<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n Modeling the Passive wheel with axle<\/h3>\n\n\n\n
Before we start modeling the wheel, we are going to need some 3D models to represent its components. These components are the passive wheel and the wheel hub. Here is the STL file for the passive wheel used in this project:<\/p>\n\n\n\n
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\n\n<\/model-viewer>\n <\/div>\n - Wheel hub assembly<\/a><\/li>\n\n\n\n
- Arrive at a flow-chart for building the parts<\/a><\/li>\n\n\n\n