Weekly Progress 7

As we head into the last week, most works has been done. Writing final report and preparing for the presentation are two major works of the week. And we have finished the report so far. Two short videos have been posted already and they are going to be played during the presentation as demonstrations. The sea perch was still running in the bath tub so the effect would not be perfect. However the main performance of sea perch was still demonstrated. Last but not least, the presentation was scheduled later today, so Good luck to us!

Presentation_Motion

Presentation_BlockingSeaweeds__6/3/2012

Building Progress 6

    As we head into the lab of the 9th week, there are only a few more physical modifications left. During this week, several improvements has been done in purpose of sloving porblems which had been detected last week.

    First, a small box filled with pebbles has been attached in order to balancing the floating force and the gravity of the seaperch. (Figure.1)  Currently there is only a rough paper box which is located in the middle of the seaperch, and the box will be cocooned by plastic bag and tapes. Paper box was selected because it is easier to fasten than other containers such as rigid plastic box. Since then, the weight of seaperch can be easily adjusted by adding or dropping pebbles.

Figure.1 Seaperch with weighs

       The second task is the shape modification of seaperch in terms of bionic shape. As it was stated in the proposal,our original goal was making the a fishlike seaperch as much as we can. The purpose to do so was reduing the influence of disturbance by fish school as well as other potential threatens. In stead of building an enormous seaperch equipped with series of protection, a much more simplified solution was used. (Figure.2)
As it has been shown in the figure, a black board was sticked in the front of the seaperch. The board was designed for blocking trash and weeds underwater, while the cartoon and safety eyewear was used just for fun.


Figure.2 one of the solution

                                                            

Building Progress 5

      After the experiment in the bathtub, we found a problem that the back side of the seaperch is too heavy that the back side is always going to sink. It will cause a big problem for us to keep the seaperch stable enough to get the water sample at different level.The reason why the back side is so heavy is that there are two motors which are located at the back giving the driving force. At first, we designed to bind a balloon at the back side of the seaperch to give an enough floating force. However, we thought the environment under the water could be very complicated. The balloon is so breakable that when it meets something sharp, the balloon will break. The seaperch will sink. In that way, we changed our idea. We sealed the two ends of the pipe located in the back side of the seaperch. We used the same theory like the balloon. If we sealed the two ends of the pipe, when the seaperch is under the water, the tube will be full of air instead of water. It can provide enough floating force. Figure 1 below is the pipe, the both ends of which are sealed.

Figure 1: The pipe with both end sealed.

     After the experiment, the method worked. With the extra help of the two pieces of round blue sponge, the seaperch can float in the water steadily. Figure 2 below shows the steady floating of the seaperch in the bath tub.

The position of the two pieces of the sponge can be adjusted to keep the level balance of the seaperch. Because of the weight of two motors, the sponge is more at the back side of the seaperch which is obvious.

More Challenge

     Because we want to make our seaperch to stay at any depth of the water, if the floating force is bigger than the weight of the seaperch, the downward movement of the seaperch can only be accomplished by the driving force from the third motor which is located in the middle of the seaperch. Whenever the motor stops, the seaperch will go up automatically. As we all know, the floating force equals to the volume of the part under the water times the density of the water and the gravity constant. After the whole seaperch is under the water, in theory, the floating force won't change anymore. Under this circumstance, we want to add some weight to the seaperch to balance the weight and the floating force when the whole seaperch is under the water. If these two forces are equal, it means the seaperch can stay at any depth of the water. We are going to get some sands and some stones into a bottle. And we will bind the bottle to the middle of the seaperch. It can both add weight and keep the balance of the seaperch. In this week, we will emphasis on this challenge by doing more experiments. It is a key step that make our seaperch to be like a depth sensor.

Building Progress 4

     This week we thought about the ways to make our seaperch more fishlike which help the control of the seaperch. However, it was difficult to find a place where we can make tests. Thus, we are going to have a negoation with managers in the swimming pool of Drexel. If it doesn't work, we are going to buy a big litter bin, since we want to focus on the balance of our seaperch. When we did the first test in a bathtub, we found a problem that the front of the seaperch was to light that it would float on the water. So we want to bind something heavy to the front of the seaperch. However, the bathtub was not deep enough. We could not do a lot tests on it. It was the task on this weeks lab. We want our seaperch can balance in the middle of the water, so we can make the seaperch up down easily which is important to be a good sensor to test the height.

Test_001__5/10/2012