Project Objectives
High Priority Objectives
Ensure sensor is easily attachable / detachable
Log data that can be used to generate a velocity curve with +/-0.5 ft/s accuracy
Design the system to be rugged
House multiple sensors for more data collection in the case of faulty trials
Stabilize the velocity float such that it does not oscillate or cause much drag on the cart
Second Priority Objectives
Design the system to be passive with minimal electronics aside from the pressure sensors
Develop algorithm to convert time and pressure data to depth and velocity
Other Constraints and Issues
The accuracy of the current sensor is 0.6% of scale (+/- 1 ft)
The accuracy of the curve fit may represent a quadratic of polynomial fit (instead of linear)
The float must produce minimal drag before and during the experiment
Ocean waves produce a pressure signature that will be detected by the sensor. This should be filtered out of the data.
A proper testing facility will be needed to test the drag and underwater behavior of the prototyped floats.
WOW Design Solution
The objective of the velocity float is to measure the pressure of the ocean water in order to output the position and velocity of the float, and thus, the cart. The ideal design would be a float that
is low drag
produces minimal line tilt
has a high resolution
requires minimal electronics
is simple to use
is rugged and reliable
is cost effective
and an algorithm that generates the velocity profile with a high level of accuracy and will be able to correct for surface waves and tilt effects.
Risk Reduction Strategy
Risk Area: Stability
Strategy: An initial velocity float will be designed with a modular hinge for a swiveling bail. This will allow the float to sit horizontally prior to the experiment in order to reduce drag from the current. Then, once the cart begins to move, the float would ideally rotate in order to remain streamlined with the direction of travel. The ideal position of the bail will be determined analytically at first and then experimentally by testing a prototype in a swimming pool.
Risk Area: Accuracy
Strategy: Although a pressure sensor has already been acquired, research will be continued on whether there are other pressure sensors that would be more suitable for the project's purposes--that is, that would be able to obtain enough data to obtain a velocity profile with +/-0.5 ft/s accuracy. Minimizing the risk of inaccurate data will involve a statistical approach, incorporating the accuracy of the pressure Ensor, its sampling rate, and a rough model of the dynamics of the system. Finding and purchasing this sensor early in the process, if necessary, will allow for more validation testing of the system.
Risk Area: Line Tilt Angle
Strategy: In order to minimize the line tilt angle, and thus improve the quality of the data and minimize the need for correcting factors, an analytical approach will be used to determine the effects that buoyancy and drag have on the line in a range of currents. This will mostly be completed through free body diagrams of the system and making safe assumptions about the experiment conditions and then validating these assumptions.
Intermediate Milestones
The following milestones are also represented in the Gantt chart at the top of this page.
Week 1:
Finalize design for the first prototype
Finalize the test bed for the static test
Week 2:
Fabricate the first prototype
Week 3:
Perform a static test on the float
Week 4:
Fabricate the second prototype
Week 5:
Perform a dynamic test on the float
Week 6:
Fabricate the final float
Week 7:
Perform final testing of float
Week 8:
Buffer week for adjustments
Week 9:
Buffer week for tests
Week 10:
Compile information for final presentation