INTRODUCTION TO ROBOTICS Part 2: Structural System Robotics and Automation Copyright © Texas Education Agency, All rights reserved.

Robot Systems Structural System Physical system that provides support and stability Propulsion System (motion) Drive system includes motors, wheels, and gears Control System Microcontroller, operating program, electrical power, and joystick Tool and Actuator system Arms, grippers, manipulators Sensor and feedback system Perception, transducers Copyright © Texas Education Agency, All rights reserved.

Structural System The structural subsystem of the robot is responsible for physical support. Holds everything in place Also provides physical protection The durable “skeleton” of the robot to which all the other subsystems are attached The Structure and Motion sub- systems are tightly integrated to form the chassis of the robot. Copyright © Texas Education Agency, All rights reserved. Photo Credit: VEX Robotics, Inc.

Before You Begin Many types of tools and parts are necessary. Some tools and parts are required, others are simply nice to have. The larger the variety of supplies, the more creative the design can be. Systems can look better and be more structurally sound. Also increases the need for a tool/part inventory and management system. Copyright © Texas Education Agency, All rights reserved.

Recommended Tools Allen wrench set (also called an L-wrench) Open ended wrench Screwdrivers Flat head and Phillips Needle nose pliers and diagonal cutters Wire strippers Crescent wrench Copyright © Texas Education Agency, All rights reserved. Photo Credit: VEX Robotics, Inc.

Additional Tools Drill and drill bit set Saws for metal, wood, and plastic Examples: Hacksaw, band saw, chop saw, scroll saw A variety of screws, nuts, bolts Vise Multi-purpose rotary power tool to cut and smooth metal Wire, soldering iron, electrical connectors Copyright © Texas Education Agency, All rights reserved.

Example Parts Types of bolts 6-32 and 8-32 Keps nuts Square drive shaft Bearing flat Spacers and friction reducers Metal sized by number of holes 5 X 15 1 X 25 Copyright © Texas Education Agency, All rights reserved. Photos Credit: VEX Robotics, Inc.

Copyright © Texas Education Agency, All rights reserved. Photos Credit: VEX Robotics, Inc.

The Robot Base The platform or base determines the stability, the durability, the maneuverability, and the functionality of the robot. Usually made from wood or metal Provides the support structure for the rest of the robot Everything connects and mounts here The frame or skeleton Copyright © Texas Education Agency, All rights reserved.

Robot Stability Stability is defined as when the center of gravity is over the points of support for the base (called the support polygon). To increase stability, lower the center of gravity. Long arms need additional support. With one point of support an arm will rotate. If the center of gravity is moved outside the support polygon the robot will tip over. Copyright © Texas Education Agency, All rights reserved.

Base Material Considerations Common materials are wood, aluminum, sheet metal, or plastic (HDPE). Consider both weight and strength. Metals have a high strength to weight ratio. Some plastics like plexiglass will crack or break when cut and drilled. Sheet metal and aluminum conduct electricity. Wood can splinter or split but is cheap. Copyright © Texas Education Agency, All rights reserved.

Base Material Considerations Angled metal in an L or C shape will retain its shape under load. A solid square or round tube makes a very strong support structure. Can be metal or PVC – be creative! Wood is great when load is not too great. Wood can flex, bend, or break. Works well for a superstructure or platform. Copyright © Texas Education Agency, All rights reserved.

Base Material Considerations Even if you use wood or plastic for the base, you will need to use and cut metal. Motor mounts can be made from metal bent to a 90 degree angle (like angle iron). Wheels are an assembly with a mounting hub adapter to connect motor shaft to the wheel. 2 types of adapters: set screw and collet type Other types include keyway and D hubs. These are usually for larger shafts. Copyright © Texas Education Agency, All rights reserved.