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

Building Progress 3: controller and complete assembly

   This week we concentrated on the assembly of controller and the main body. Also, a simple test was made after the complete assembly.

figure 1: the assembled controller

      Figure 1 shows the shape of the controller. There are totally 4 swithes attached to the control box. Two toggle swithes that located on the main plane control the action of left and right propellers separately. Two push-button switches are located on the top of the control box which correspond to the rise and sink of seaperch.


Figure 2: the arrangement of wires

     Figure 2 shows the inner arrangement of wires. Red/black cables are linked to the anode/cathode of the battery and the power cards in the control box. The thiner green wires are linked to the right starboard corresponding to the motor on right side. Similarly, the thiner blue wires are linked to the left starboard corresponding to the motore on left side, and the orange wires are linked to the up/down motor.
   Finally, a simple test had run to test the underwater performance of the seaperch. A short video will be uploaded in a few minutes.

Building Progress 2: Motors

     This week, we made three motors for our seaperch.
     Because the seaperch is used in the water, the most important thing is to keep the motors dry, or they won't anymore if they have contact with water. We used electrical tape to wrap the motors. Then, we connected each motor to a wire by soldering. After that, we put the motors into three film cans and used wax to fix and warp up the whole motors. And the propellers were connected to the motors at the outside of the film cans, because the propellers are the power of movement. Figure 1 below shows one of the motors is fixed on the seaperch.

Figure 1: One of the motors fixed on the seaperch.

     Two motors are fixed on the back of the seaperch. One is on the left and another one is on the right. If both motors are running, the seaperch can go forward or backward. And the seaperch can also turn around by running only one motor. Figure 2 and Figure 3 below show the front side and the left side of the seaperch.

Figure 2: Front side of the seaperch with three motors.

Figure 3: Left side of the seaperch with three motors.

      From Figure 2, we can see the third motor is vertically fixed in the middle of  the seaperch. Apparently, this motor controls the seaperch to go up or down. Besides, the two wires, which are connected to the left and right motors in the back is green and blue. And the wire connected to the middle motor is orange. These are important to be used in the next step: remote controller. Since the controller we received is the old version, which is different from others, we need put more work on the remote controller in this week's lab.