Team Vision for System-Level Design Phase
The plan for the System-Level Design phase was to determine possible system configurations which would allow autonomous control of the dome. A simulation model as well as a schematic of the original system were to also be generated.
A concept for system control was finalized which will utilize a calibrated encoder as well as a 6-Degree-of-Freedom (6DoF) sensor for feedback into a microcontroller. The original dome control circuit was mapped into a schematic and was translated into LabVIEW for future testing.
ER Mapping to Functional Decomposition
Morphological Chart and Concept Selection
- Power Consumption
- Maintenance Requirements
- Easy Installation
- General Complexity
Feasibility: Prototyping, Analysis, Simulation
- Existing Encoder has 1000 PPR (Pulses per Rev)
- Each groove in the dome is spaced out about 0.0222m apart
- The dome has a Dia of 5m => Cir=15.7m
- 15.7m/.0222m~706 grooves along the circumference => ~2 grooves per degree
- With 1 rev of motor (Teeth on gear/ grooves per degree)
- 8 teeth on gear => 4 degrees of rotation for the dome
- 10 teeth on gear => 5 degrees of rotation for the dome
- 12 teeth on gear => 6 degrees of rotation for the dome
- 1000 PPR (PPR/degree of dome rotation)
- 8 teeth on gear => 250 pulses per degree of dome rotation
- 10 teeth on gear => 200 pulses per degree of dome rotation
- 12 teeth on gear => 166.67 pulses per degree of dome rotation
- Existing sensor should be feasible to control dome to <1 degree of accuracy after a calibration.
QuestionCan a 6DoF sensor (IMU) be used to report telescope position?
- The 6DoF will be mounted on the CoG (center of gravity) of the telescope.
- Only the gyroscope data will be utilized for dome tracking.
AnalysisA six degrees of freedom sensor utilizes an internal accelerometer as well as a gyroscope/magnetometer to track a system in 3 dimensions. Benchmarking was done to compare the acceleration as well as rotational sensitivity requirements of differently configured 6DoF sensors. It was found that a magnetometer would have a high tracking error due to magnetic field disruption caused by the dome. Therefore a 6DoF sensor utilized a gyroscope for rotational tracking was chosen and compared to the spec of the telescope.
The specs of the 12" f/10 LX200GPS are shown below:
Telescope Slew Rate-Rotational Speed
Min Rotational Speed = .25 arc-min/sec=.004 degrees/sec
Max Rotational Speed = 480 arc-min/sec=8 degrees/sec
The rotational speed was compared to the gyroscope sensitivity to ensure accurate data collection.
Most 6DoF sensors have variable sensitivity scales which can be set based on the speed of the device being monitored.
Simulation of SystemBelow is a link to a LabView model of the telescope and manual dome controls.
Designs and Flowcharts
The top level schematic of the control box can be found here:Control Box Schematic
For a master list of project risks, click here.
Plans for next phase
Raymond Castro's Three Week Plan: Ray's Goals
Sarah Williams's Three Week Plan: Sarah's Goals
Joseph Brescia's Three Week Plan: Joe's Goals
Wilson Quizhpi's Three Week Plan: Wilson's Goals
Ahmed Alhurubi'sThree Week Plan: Ahmed's Goals