After a planetary gearing system was designed, including the outer casing and a protruding drive shaft, it was analysed in Solidworks.
This system has a ratio of 10:1. Due to the small size of the teeth and the quality of the 3D printer being used, it was highlighted that the individual gear teeth would more than likely result in being merged into one.
As this is only for testing, to prove feasibility, the team decided to study this design on Solidworks instead of physically printing it which would give us more information about forces that it suffers whilst working and can help us work out the wear
The meshing of the gears was then tested and approved in solidworks. To bypass the problems of gearing printing we decided to invest in a higher torque, lower RPM motor. This would also avoid the problem of debris getting in the system.
The main purpose of the ROV is to survey infrastructure underwater. In order to accomplish this we are using a camera mounted on the top. In order to make the camera more functional we wanted it to have the ability to move allowing for a larger view while staying stationary.
We tested if this is feasible using 3-axis servo mounts. A video of our test is shown below:
As the video shows we programmed the servos to move based on the input on a controller.
When designing the chassis, there were four main constraints;
- The first was that the design could be manufactured without many long winded and expensive processes
- Secondly I had to ensure that it would fill all requirement set by the client
- Thirdly it should meet the requirements of the parts that my team will be designing i.e. mounts for electric component boxes, camera mounts and other components
- Lastly it needed to be updated to any extra specifications will be supplied with when Babcock visited
With those restraints in mind, the final design is this:
The frame has all the mountings for the prop housings, servo housings, and serves as a platform to mount all the components.
The chassis has been designed to allow the ROV to rotate on the spot, this will facilitate maneuvering in tight spaces and has allowed the design to be a bit larger which will allow it to have more space for the electronic components.
The camera mount will be placed in the middle of the chassis and we are currently working on the design for this. The image bellow shows an example for the camera mount.
The camera would be mounted on this which will rotate to allow the users a better view of the object being inspected
This week we focused on finding the best way to transmit data/communicate between the ROV and the team stationed on the dock. We also looked at what we think would be the most important sensors to use within our ROV.
We found a variety of ways in which we can communicate with the ROV however a few of the methods found would not be feasible to use. We narrowed it down to two methods we planned on testing:
We were going to select low frequency transmission however we found that all Radio Controlled Models in the UK are only permitted to function under a specific frequency. This is to prevent interference with other devices such as radio broadcasts. This limited us to using a buoy for communication.
The sensors we think are the most suitable for use on the ROV are:
A Magnetic Sensor – This will allow us to calculate the direction in which the ROV facing effectively acting as a compass.
Gyroscopic Sensor – This would help by determining the orientation of the ROV when it is underwater.
Proximity Sensor – Proximity sensors would allow us to detect when an object is within a certain range of the ROV.
Pressure Sensor – This will allow us detect the depth at which the ROV.
This week the main focus of our research was the movement of the ROV. We have decided to use DC Brushless Motors as they a water resistant so will work fine in the required environment. We have ordered a motor to test the gearing we will require as well as how well the propellers work. Its specs are below:
Rather then making our own propeller we have decided to download one off of GrabCAD. This will save us a lot of time compared to making one from scratch due to the number of calculations we would need to make as well as repeated testing to make sure the design functions. The CAD is shown below:
We are planning to 3D print 5 of these propellers each with a different pitch to find the best one to use on the ROV.
Finally we looked at what type of gearing we want to use. We concluded the best would be worm and wheel gearing as this will reduce the size of the gearing system. We are looking for an in water RPM of about 300-400, which will require a gearing ratio of 1:10-20. The RPM will be reduced in water, so testing it is highly necessary for these calculations.
 https://grabcad.com/library/5-blade-propeller by David Thomas, Uploaded: August 26th, 2011. Access date: 5/10/16
 https://grabcad.com/library/marine-propeller by Chao Wey, Uploaded: August 17th, 2011. Access date: 5/10/16
This week we came up with our first draft for our CAD design.
This is shown above. We have 4 holes made for vertical fan slots allowing the ROV to move up and down. It then has 4 horizontal thrusters allowing the ROV to move forwards, backwards and turn.
We also researched the following:
- Communication method between the ROV and the controller
- Which sensors we can use on the ROV
- Ways to attach/remove the ROV and detection of a problem
- The behaviour of propellers in water and he necessary gearing to accompany it.
We have also made a list for parts to buy to build a small prototype to prove feasibility. This will allow us to prove that our design works without the need for a large budget.
During the first week we discussed all the ideas we had for the ROV under three main headings. The first thing we considered was how we wanted the ROV to move:
The next thing we looked at was what electronic components we might want to use:
The final thing we discussed was any other additions to the ROV that would help with detecting faults: