Fall 2016 Solar Panels: Requirements Update

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By Stephan Khamis (Missions, Systems, and Test)

Approved by Inna Echual (Project Manager)

Introduction

This blog post contains our most up-to-date requirements for the Solar Panel system of the Pathfinder project. Within this blog post you will learn about the changes we have made since the CDR to update this document.

Updated Requirements

Solar Panel Requirements

  1. The Pathfinder shall be self-sufficient using solar panels.
    • According to accuweather the sun rises at 6:50 AM and sets at 4:46 PM on December 15, 2016. The Pathfinder will start to explore at 2:45 PM.
    • Starting at 80% battery life, the Solar Panels shall be able to charge the battery system to 95% in under 8 hours.
      • The solar panel shall be wired to produce at least 12 Volts and 300 mA to charge our battery system.
      • The battery will have a charge controller to prevent the battery from exceeding 12 Volts of charge, which is the maximum capacity of the battery system.
  1. The solar panels shall be able to enter and exit a cocoon state.
    • The motorized folding mechanism shall be done using a stepper motor, a motor bracket, a worm gear, and a piano hinge for each of the 3 folds.
  2. The Solar Panels will have a fixed north/south orientation for the panels to track the east to west movement of the sun.
    • Two main side panels consisting of two smaller panels shall articulate with the sun using stepper motors specified to handle 1188 oz/inch.
      • The solar cells should be used to measure and compare the voltage at an angle using a voltage divider.
    • The Solar Panels will be able to withstand 50 lbs, under the force of gravity.
  3. The form factor of the Solar Panels shall be identical to that of the Spirit and Opportunity
    • Six panels shall be cut proportional to the six panels on the Spirit and Opportunity
    • The solar panels shall use 39 mm x 39 mm polycrystalline solar cells to accommodate the customized shape of the Spirit and Opportunity
  4. The Pathfinder will be able to fit into the east most cabinet in ECS – 317.
    • The Pathfinder shall have dimensions no greater than 19” x 34” x 26” in its closed cocoon state.
    • The Solar Panel component of the Pathfinder shall be able to be added and removed from the Chassis within 20 minutes (wiring and mechanical), without the use of power tools for future separate usage of the Chassis and Solar Panel system.
  5. The Pathfinder shall have requirements agreed between both the Solar Panel and Chassis group within the Interface Control Document (ICD).
    • The Solar Panel group will provide 5.76 inches from the front top plate towards the center to accommodate the placement of the Chassis’ Pan & Tilt Mechanism.
    • The Solar Panel group will provide an availability of 10 inches between side panel motors required by the Chassis group.
    • The base of the Solar Panel will have four equally spaced 0.5” holes to establish a concentric interfacing point with the Chassis
    • The Solar Panel group will be allowed a power allocation of 2 Amps at 12 Volts, while the Chassis group will be allowed a power allocation of 11.4 Amps at 12 Volts.
    • The Solar Panels will not exceed 50 lbs as required by the Chassis group.
  6. The Pathfinder should be able to ride itself back up using the side Solar Panels and Custom Command; Cocoon.
  7. The expenses of the Solar Panel system should be limited to $200.
  8. The Solar Panel System shall be completed by December 14, 2016.
  9. The Solar Panel system shall use a custom PCB.
  10. The Solar Panel system shall use custom commands.
  11. The Solar Panel system should use custom telemetry.

Above are the Solar Panel system’s most up-to-date requirements. These requirements are more than just sentences asking what needs to be done, they’re directing the path we are taking in order to complete this project. These are requirements that we must meet and must be able to verify and validate. Requirements must satisfy two of three questions:

  1. Is it verifiable?
    1. Meaning is this a requirement that we are capable of verifying?
  2. Is it quantifiable?
    1. Meaning is this a requirement that we can quantify in numbers and test.
  3. Is it realizable?
    1. Given the fact that we have only 16 weeks in this course to design and build, some things just aren’t realizable to do within that timeframe.

Throughout the semester, we have been refining our requirements and finalized them by CDR. But, after speaking with the customer, president, and systems divison manager, we added a few requirements that would help us in creating a test plan. The added requirements are the last few; 7-12. These are requirements to help show that we will have the project completed by a certain date, under a budget, interfacing requirements, and some custom commands/telemetry the customer would like.

Past Requirements 

As stated before, we have added quite a few requirements since CDR. These requirements stemmed from speaking with the customer, president, and systems division manager while creating a test plan matrix for the final on December 14 & 15, 2016.

Future Updates

As of now, we have no plans to updating or changing anything. But, to speak for what I think should be done in the following semester, there could be work done. I believe these are decent requirements but, they are not perfect.