UNC RoverSat IV

UNC RoverSat IVUniversity of Northern ColoradoCritical Design ReviewFriday, June 25 2010

UNC RoverSat IVMission Overview:

To sucsefully deploy an autonomous rover from a balloon payload.

To improve upon previous RoverSat missions by reducing mass.

To improve upon previous RoverSat missions by increasing reliability.

To engage highschool students in the design and testing of a Balloon payload.UNC RoverSat IVMission Objective:

Using a COTS Accelerometer determine when the payload has landed.

Upon landing determine that conditions are stable (no movement) and begin deployment.

Deploy a rover by first opening the payload then activating the rover.

Rover will then exit the payload and begin operations. UNC RoverSat IVMission History:

The RoverSat project has been on going for the last 4 years at UNC.

Three payloads have been built using similar methods of sensing and deployment.

The payloads have deployed successfully but in all cases the rover has failed to leave the box.

Each failure has demonstrated new problems in payload Boxdesigns.

Other failures included the failure of activation devices.UNC RoverSat IVRoverSat I

RoverSat I First Attempt at rover payload

Sucsesses Gained video footage of flight and box sucssessfully opened

Failures Rover activated early in the flight causing batteries to be drained before landing.

UNC RoverSat IVRoverSat II

RoverSat II Attempted to integrate camera into rover for flight and operation.

Sucsesses Gained video footage of flight and box sucssessfully opened.

Failures Rover activated early in the flight. Rover also was damaged by rough landing.

UNC RoverSat IVRoverSat III

RoverSat III Attempt at rover simplification and deployment mechanism revisited.

Sucsesses Box successfully opened Rover successfully activated.

Failures Rover failed to leave box due to software failure involving obstacle avoidance sensors.

UNC RoverSat IVSupport From Frontiers of Science Institute:

This will be the first year FSI students will assist in a balloon project. FSI students have been developing the concept and designs for the latch mechanism and over all box design.UNC RoverSat IVRoverSat IV Design Features:

RoverSat IV We intend to improve on the design of RoverSat III with a new type of locking latch.

The former payloads relied on a fishing line that was destroyed to un-lock the box. This is being replaced with a non-destructive linear actuator and dead-bolt method.

The rover will have a wireless communication path to the box to prevent premature activation. Activation will only come after the doors are verified to be open. This will also enable ground support to manually deploy the rover in the event of an autonomous failure.UNC RoverSat IVRoverSat IV Mechanical Hardware:

Two Components:Box Rover enclosure and deployment- Mechanical latch to ensure box remains closed during flight- Mechanical device to open box facilitating deployment- Use of composites to decrease weight of payloadRover Small autonomous rover to be deployed- Light weight plastic design - Small rocker-bogie design for traction- Press fit frame for quick assembly and durabilityUNC RoverSat IVRoverSat IV Latch Mechanism:

Small linear actuator provides motion to un-lock bolt

LockedOpen (Pin in locked position)UNC RoverSat IVRoverSat IV Deployment Mechanism:

A servo will be used to push the box open. The servo will have an arm and two push rods much like RoverSat III.UNC RoverSat IVRoverSat IV Box Materials:

Sandwich Foam Carbon Fiber Sheet This material is very rigid for its weightAvailable from Hobby Stores online

Tongue and groove construction improves reliability.

Cargo Strapping will provide the hingeMaterial for the box.

UNC RoverSat IVRoverSat IV Box Dimensions:

Box Dimensions:

UNC RoverSat IVRoverSat IV Rover Construction:

All Parts are 2D and can be cut on laser table for quick production.

UNC RoverSat IVRoverSat IV Rover Suspension:

Rocker-bogie design provides superior traction with minimal effort.

UNC RoverSat IVRoverSat IV Rover Dimensions:

Side View

UNC RoverSat IVRoverSat IV Rover Dimensions:

Bottom View

UNC RoverSat IVRoverSat IV Electronics:

Box Electronics for the box will be based around the arduino pro.- Accelerometer- Door Lock actuator- Deployment mechanism actuator- Xbee Radio (Communication between rover and box)

Rover Electronics for the rover will be based around the arduino pro.- Motor Controllers- IR sensors (Obstacle avoidance)- Xbee Radio (Communication between rover and box)UNC RoverSat IVRoverSat IV Electronics (Box) :

Arduino pro

ADXL213AEADC

PWM

Linear Actuator

UARTUNC RoverSat IVRoverSat IV Software (Box) :

Description: Program begins with 1.5hr sleep cycle.Sleep cycle exitsAccelerometer measures 2 axisAccelerometer makes about 100 measurements over 30 secondsArduino calculates standard deviation.If standard deviation is acceptable for landing program proceeds to deploymeneLinear actuator is drawn in by arduino, unlocking the payload doors.Servo pushes the doors open for rover to exit.Xbee radio sends communication to rover telling it to deploy.UNC RoverSat IVRoverSat IV Electronics (Rover) :

Arduino proADC

PWM

Motors

UART

IR Ranger

UNC RoverSat IVRoverSat IV Software (Rover) :

Description: Program begins with sleep cycle.Sleep cycle exits when told by main box through Xbee radioRover begins automated deployment routineRover then enters autonomous mode for explorationIf accessed by user through Xbee rover can switch from autonomous to manual mode.UNC RoverSat IVRoverSat IV Major Parts List:

Box- mechanicalcarbon fiber foam platedelrin plasticaluminum angle ironcargo strap materiallinear actuatorjoint assemblylarge servodeployment mechanism- electrical7.4 lipoly pack 1000maharduino proADXL Series AccelerometerXbee wireless radioRover- mechanicaldelerin plate for chassis50:1 Copal motors2 Light flight tires standoffs - electrical7.4 lipoly pack 1000maharduino proSharp Irvrangefindermotor controllerXbee wireless radioUNC RoverSat IVRoverSat IV Testing :

Tests to be performed:Drop Test (15 ft)Cold Test (70f to -70f over one hour)Deployment testing (Premature)Deployment testing (Ideal)Deployment testing (Non-Ideal)Rover test drive (Terrain evaluation)Day in life test (Full program, full environment)

UNC RoverSat IVRoverSat IV Mass Breakdown :

Mass Budget:Rover 500g-motors 200g-battery 100g-wheels 40g-electronics 60g-chassis 100g

Box 1000g-locking mechanism 200g-deployment mechanism 250g-battery 100g-electronics 60g-chassis 390g