Pathfinder Chassis & Solar Array Spring 2019

Pathfinder Project: Interface Control Document

Author:

Daniel Enverga (Mission, Systems, and Testing)

Approval:

Brendan Guitron (Project Manager – Pathfinder Solar Array)

Alexandrea Jackson (Project Manager – Pathfinder Chassis)

Table of Contents

System Overview

The system will include the two different projects: Pathfinder Chassis and the Pathfinder Solar Array. Together, the system will mimic the NASA rovers Opportunity and Spirit in design and function. These projects will work as a single unit to move the Chassis through a predetermined course.

System 1: Pathfinder Chassis

The Pathfinder Chassis system will include the main body, motor functions, vision functions, and Arxterra Control Panel access. The Pathfinder Chassis is responsible for physically being able to move from Point A to Point B while following GPS waypoints. On these pathways the Pathfinder Chassis will be able to avoid obstacles and traverse various terrain.

System 2: Pathfinder Solar Array

The Pathfinder Solar Array system will include the top panel covering the main body of the Chassis as well as the solar panel array which includes a central panel, two wing panels, and a tail panel. These solar panels will be responsible for charging the Pathfinder Chassis’ battery to power the Chassis’ components.

Concept of Operation and Interface Requirement

This Interface Control Document provides an outline of interface requirements imposed on the participating systems, including the Pathfinder Chassis and Pathfinder Solar Array systems. It will describe briefly the concept of operations and functionality related to the interface of the two systems. Further information on interface requirements will be described the subsequent sections.

Weight Allocation

Weight of the Chassis and Solar Array is a key factor contributing to interface the chassis and array to carry on the load of both system. The Pathfinder Chassis System will be designed to overcome obstacles on CSULB .09 mile course. From the stress test conducted by Pathfinder Chassis Generation 3, the maximum weight the Chassis body can support is 22.76 kg (50 lbs). The overall weight of the current Chassis body will weigh no more than 13.5 ± 0.61 kg (8.82 ± 1.35 lbs). The weight allocation for the Solar Array is 5.26 ± 0.41 kg (3.82 ± 1.35 lbs). At a worst-case scenario the overall weight of the interfaced systems will be 19.78 kg (43.61lbs) which will still be within acceptable range.

Space Accommodation

The Pathfinder Chassis and Solar Array systems share the space inside the main body of the Chassis system. This will include the battery, battery charger, and Arduino Mega. The Solar Array will need space for their Power Hub PCB with size 8.397 x 5.349 cm (3.306 x 2.103 in) which will be provided in the Chassis main body.

Functional Allocation

The Pathfinder Solar Array will be responsible for charging the main power source, the battery, of the Pathfinder Chassis. At the same time, Solar Array, will be sending current and voltage readings from the solar panels to allow quick repairs toward replacing solar panels. The Pathfinder Chassis will be responsible for carrying the weight of the Solar Array throughout the entirety of the predetermined GPS course.  

Control Mechanism and Data Transfer

The Pathfinder Chassis and Pathfinder Solar Array systems will be controlled together through the Arduino Mega microcontroller from Pathfinder Chassis. The telemetry from the Solar Array (Voltage/Current) will be transferred to the Arxterra Control Panel from the Arduino Mega. The telemetry from the Chassis (RPM/Voltage/Current/Ultrasonic) will be transferred to the Arxterra Control Panel from the Arduino Mega.

Power Transactions

The Pathfinder Chassis and Solar Array will be energized via a common powertrain, supplied by a 7-Ah, 12-V battery stored in the main Pathfinder Chassis body. The battery will directly power the motors of the Chassis and the PCB of the Chassis. The Chassis PCB will reduce the incoming voltage to 5V to power the rest of the Chassis system. The Chassis system will be powered using 529.34 ± 59.67 mA. The Solar Array system will be powered through the same 5V plane using 35.35 ± 1.63 mA.

Mechanical Interface

The Pathfinder Chassis and Solar Array system will have mechanical interface on the top side of the Pathfinder Chassis main body. The pathfinder Solar Array will be in charge of the top panel to enclose the Chassis main body. This has been decided due to the Solar Array system being attached to the top panel of the Chassis. As of right now the top panel does not fit securely on top of the Chassis Body and will be up to Solar Array to secure it.

Electronics Interface

The main electronic interface between both systems include the Arduino Mega microcontroller and the battery. The Pathfinder Chassis will include (4) pins for Solar Array to use on the Arduino Mega. (2) pins will be used for the SDL/SCA wires to allow the telemetry (Voltage/Current) from Solar Array to be read on the Arxterra Control Panel. The other (2) allocated pins will be used to power the current and voltage sensors from the Solar Array. Pathfinder Solar Array will be responsible for charging the battery before and after the Chassis completes the mission course.

Software Interface

The Pathfinder Chassis and Solar Array will be interfaced through the Arduino Code in order to communicate telemetry with the Arxterra App and Control Panel. Pathfinder Chassis will add the Solar Array arduino code to allow the telemetry from the Solar Array to be read from the Arxterra Control Panel.

Aesthetics

The Pathfinder Chassis and Solar Array will have a matching appearance with the NASA rovers Opportunity and Spirit. The material for both systems appearance is aluminum. The color palette is currently kept as the natural color of the aluminum plating.

Processing Schedule

The Pathfinder Solar Array, in conjunction with the Pathfinder Solar Array will have their respective systems ready for integration by the tentative date of 4/15/2019.

Safety

The Pathfinder Chassis and Solar Array systems will follow the regulations of the Engineering Standards and Constraints as stated from previous generations:

ENGINEERING STANDARDS AND CONSTRAINTS

Applicable Engineering Standards

  1. IEEE 29148-2018 – ISO/IEC/IEEE Approved Draft International Standard – Systems and Software Engineering — Life Cycle Processes –Requirements Engineering.
  2. NASA/SP-2007-6105 Rev1 – Systems Engineering Handbook
  3. Bluetooth Special Interest Group (SIG) Standard (supersedes IEEE 802.15.1)
  4. C++ standard (ISO/IEC 14882:1998)
  5. Federal Communications Commission (FCC) Relevant standards for a product implementing a 2.4GHz radio, FCC Intentional Radiators (Radio) Part 15C, and Unintentional Radiators FCC Part 15B for CPU, memories etc.
  6. NXP Semiconductor, UM10204, I2C-bus specification and user manual.
  7. ATmega16U4/ATmega32U4, 8-bit Microcontroller with 16/32K bytes of ISP Flash and USB Controller datasheet section datasheet, Section 18, USART.
  8. USB 2.0 Specification released on April 27, 2000, usb_20_20180904.zip
  9. Motorola’s SPI Block Guide V03.06

Environmental, Health, and Safety (EH&S) Standards

CSULB College of Engineering (COE) Safety Resources.  Start your search for applicable CSULB COE Safety Standards and Procedures here. Please review and acknowledge if any safety issues as defined by the COE applicable to your project. For example, the closest safety constraint for a linear actuator is for use of the Hydraulic Press located in the Engineering Technology (ET) Building Lab. Here is a link to the Hydraulic Press Safety document.

CSULB Environmental Health & Safety (EH&S)

IEEE National Electrical Safety Code (NESC)

NCEES Fundamental Handbook (FE) Reference Handbook

ASTM F963-17, The Standard Consumer Safety Specification for Toy Safety, is a comprehensive standard addressing numerous hazards that have been identified with toys. In 2008, the Consumer Product Safety Improvement Act of 2008 (CPSIA) mandated that the voluntary toy safety standard in effect at that time become a nationwide mandatory children’s product safety rule.

Disposal of Hazardous Waste including Electronic and Solar Cells

CSULB Physical Planning & Facilities Management (PPFM) Environmental Compliance Electronic Waste Handling and Disposal Procedures. These procedures shall be followed for the disposal of all batteries.

Qualification Methods

This section provides a set of qualification methods used to verify the interface requirements defined in Section 2 “Conception of Operation and Interface Requirements.” The further details of each qualification method will be described in the verification and validation test plan. The Qualification methods include:

Demonstration – An observation of the functional operation of interfacing Pathfinder Chassis and Solar Array systems will be used to verify the interface requirements defined in Section 2.3 and 2.8.

Test – A use of instrumentation and test equipment to collect data needed to verify the performance will be conducted to test the requirements defined in Section 2.1, 2.2, 2.4, 2.5, 2.6, 2.7.

Inspection – A visual examination of the outer appearance of two systems will be used to verify the Aesthetics requirement defined in section 2.9.

Approvals

The Interface Control Document has been written on agreement between the Pathfinder Chassis and Pathfinder Solar Array. Approvals for the Interface Control Document:

Pathfinder Chassis

Project Manager: Alexandrea Jackson          Date: April 7th, 2019

Pathfinder Solar Array

Project Manager:  Brendan Guitron Date: April 8th, 2019

Records of Change

Specification of this document is subject to change. A summary and an explanation of changes between the approved versions of this document and a new agreement will be submitted for approval as a supplemental of this document.

Change 1: Weight Allocation 1.2.1 (4/10/19)

Due to review of the Stress test conducted by Pathfinder Chassis Generation 3. It was discovered that the initial allocation for both systems was 22.76 kg instead of 50 kg. This was determined due to initial belief that the stress test was done given an amount of kg instead of the actual unit, lbs. Due to this error the overall allocation to both systems was reduced by more than 50%. Luckily however, from the mass reports, as of 4/10/19, both systems are within the mass range.

Change 2: Space Allocation 1.2.2 (5/10/19)

Removed a portion of the Space Allocation since the PCB from Solar Array will not be enclosed within the Chassis body.

Control Mechanism and Data Transfer

Added a telemetry reading for temperature to be shown in the control panel.