P08201: RP10 Drive Platform 2nd Generation
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Design Information

Motor Module

To satisfy the customer need of reusing as many parts from previous designs as possible, the team decided to base its overall structure of the motor module around the previous team (P07201). The motor module was divided into several sections which include the yoke, encoder box, turning plate, and the driving components connecting the first two sections. The yoke is located below the turn table and is used to provide housing for the horizontal driving shafts and the wheels. The encoder box is used to house steering and drive encoders, as well as a support to mount the motors. The vertical shaft transmits power from the motor to the horizontal shaft located in the yoke using a set of miter gears.

Motor Module Concept

Motor Module Concept

One of the objectives for P08201 is to reduce the size and weight of the overall robotic platform. Replacing the original turning plate with a six inch square one resulted in a smaller space taken up by the motor module along the horizontal plane.
Motor Module

Motor Module

The overall height was reduced by changing the wheel from five inches in diameter to three inches in diameter. In order to preserve the performance of the original P07201 design, the diameter of the timing pulleys was changed from 1:1 (top: bottom), to 2:1.

Along with the changes in the turning plate and wheel dimension, the acrylic plate thickness was also reduced. The fastening system between acrylic plates used aluminum brackets to re-enforce the connection between them. This made the assembly process faster and more efficient.

The fastening system for the driving components has also been changed. At the customer's request, the team looked for ways to secure and connect gears and shafts while maintaining easy access to change components. The solution was to use cotter pins to secure and connect the driving components.

The main design of the P08201 required the robotic platform to have infinite turning angles. Also, because of the requirement to reuse components of P07201, the old system and components were reused when possible. The same ring gears and spur gears were initially chosen to provide a reasonable rate of rotation for accurate control. The spur gear was however changed due to an inability to find the original part. As such, the ratio was changed from 15.6:1 to 13:1 which results in about 5.56 rpm or 10.58 s/rev.

Performance Specification:

8020 Platform

8020 Frame Concept

8020 Frame Concept

A major design requirement is a lightweight platform which is strong enough to support a payload of 10 kg. The P07201 team selected acrylic tubes as their main structural material. However, machining and drilling required for the fastening screws compromised the structural integrity. This team, under the recommendation of the customer, selected 8020 Aluminum extrusion as the main structural material. The benefit of 8020 comes from a slot and gap along the length of each of the four sides for easy construction and mounting of other, non 8020, components. Also, off the shelf fastening system are available for quick assembly. The Aluminum material used in 8020 is stronger and can withstand a greater payload with less deflection then the previously used acrylic tubing. The basic unit of assembly for the frame design is the Y-Bar. The Y-Bar contains two U shaped ends for attaching the motor modules, and a beam connecting to each of the two ends.

With the Y-Bar as the basic structural unit, the platform can be easily reconfigured to meet the requirements verifying design needs. The rest of the platform was used to connect two y-bars to fit the 4 wheel requirement with connector and the cargo platform to transport the payload.

Mechanical Components

Complete Assembly

Motor Module

Motor Module

Motor Module

Platform

Part Information

Strengths

Areas for Improvement

RP-10

RP-10


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