P18572: Telescope K-Mirror Array
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

Electrical

For this phase of the design process, the goals of the electrical system include: finalizing motor and controller selection, finalizing encoder, and developing the emergency shut down controls.

Mechanical

The goals of the mechanical system include: having a working CAD model of the K-mirror systems including mating components, preliminary FEA and defection calculations used to help further the design.

Progress Report

Electrical

Major subsystems are still under development at this point. Critical information required for completion is still waiting for answers.

Mechanical

The CAD model is still being developed at this point. The development of the CAD model is being designed to include enough free space for the mirror mounts that are still under development by the customer. Preliminary FEA analysis has been used to study the structural advantages of different designs.

Engineering Analysis

Load Cases

Figure 1: Load Case 1

Figure 1: Load Case 1

Figure 2: Load Case 2

Figure 2: Load Case 2

Figure 3: Load Case 3

Figure 3: Load Case 3

Preliminary Arm Design

Figure 4: 1st Revised Arm

Figure 4: 1st Revised Arm

Figure 5: Displacement

Figure 5: Displacement

Material Max Displacement [mm] Load Case 1 Max Displacement [mm] Load Case 2
SW "Alloy Steel" 0.0368 0.0051
Figure 6: 2nd Revised Arm

Figure 6: 2nd Revised Arm

Figure 7: Displacement

Figure 7: Displacement

Material Max Displacement [mm] Load Case 1 Max Displacement [mm] Load Case 2
SW "Alloy Steel" 0.072 0.0051

Drawings

Project Ownership

Figure 8: Center Centric Design

Figure 8: Center Centric Design

Preliminary CAD Drawings

 Figure 9: OverView

Figure 9: OverView

Figure 10: Side View

Figure 10: Side View

Further development of the CAD drawings are currently in the works. Changing developments in the optic system are being incorporated to create a more accurate representation of the final design.

Control System Design

Figure 1 shows the schematic for the Raspberry Pi and the USB to RS485 board. The USB to RS485 board interfaces with the Raspberry Pi through the USB 2.0 port. This board allows the Raspberry Pi to send out serial data to the motor controller. The USB to RS485 board and the motor controller will be physically connected through RJ45 jacks and Cat5E cable.

Figure 11: Schematic of Raspberry Pi and USB to RS485 board.

Figure 11: Schematic of Raspberry Pi and USB to RS485 board.



The motor controller, shown in Figure 2, provides power to the motor. In addition, it is also capable of actuating the motor brake and interfaces with the encoder built into the motor; this provides feedback of the motor shaft position.



Figure 12: Schematic of motor and motor driver.

Figure 12: Schematic of motor and motor driver.



Figure 3 shows the schematic for the 24VDC and 5 VDC power supplies, as well as the absolute encoder. The encoder is powered by the 5V output of the Raspberry Pi. It is also interfacing with the Raspberry Pi of a SPI connection.



Figure 13: Schematic of power supply and encoder.

Figure 13: Schematic of power supply and encoder.

Bill of Material (BOM)

Great effort has been taken to ensure parts with the longest lead time have been ordered. Parts critical to testing the K-Mirror control system, have been ordered. This BOM does not currently reflect the number of spare components that will be required for this project.

We are currently well under budget, the only remaining high price items are that related to metal material and machining.

Figure 14: Bill of Materials for K Mirror Assembly.

Figure 14: Bill of Materials for K Mirror Assembly.

Flow Chart

Figure 15: K Mirror high level Electrical System design.

Figure 15: K Mirror high level Electrical System design.

Test Plan

A majority of the testing required for this system will be on the electrical and software side. We currently have established two test plans that the critical to the K-Mirror working properly. This includes testing the RS485 communication between the Raspberry Pi and the motor controller. Additionally, rigorous testing needs to be conducted to ensure the emergency switches and limit switches operate as intended.

Figure 16: K Mirror Test Plan.

Figure 16: K Mirror Test Plan.

Design Review Materials


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