Final Project: 1st Classroom Visit

The goal:
My goal for the visit was to see if our idea would work well in a real classroom and to get some feedback from the teacher.

Storyboard:
I presented the teacher with this story board in to help explain our idea.

Her suggestions:

1. The mat doesn't need to detect if the child is still sitting on the mat, they only need to get the kids to the mat in the first place.
2. Red and blue and black and white would be the best colors because those are some of the first colors they can distinguish.
3. The mats should be no wider than 16.5 in in diameter, but they could be longer lengthwise if they are oval shaped.
4. Make sure that the wheel is not too distracting to the children, and that the teacher has the option to calmly change the color.
5. Make sure they are easy to stack and distribute.

Final Project: Brainstorming

The Need:
The problem which our projects seeks to address is that the children often have trouble getting settled onto their mats during group time when they are supposed to be paying attention to the teacher. Another additional problem related to the mats is that the kids sometimes have trouble staying on the mat once they get settled because they want to squirm around. The teacher expressed a greater interest in getting the children to settle on their mats initially.

Initial Idea:

Our initial thought was to have a mat with four different sections, each with one of the 4 colors red, blue, yellow, or green. The teacher would have a switch which would control which part of the mat the children needed to sit on in case the children are getting restless.

Possible Problems:

1. Four Sections could be too large for the size of the classroom
2. If they were connected to a wire that the teacher controlled then there would be a lot of wires from 16 mats. The wires could become a hazard and a distraction to the children as well as being cumbersome to put away and get back out.
3. A switch wouldn't be visible enough to the children; they need reinforcement from many different senses

Edited Idea:
Having considered the possible flaws of our initial design we decided that the new design would only have two colored sections in order to save space. We would also like to look into a wireless approach to controlling the mats. We also decided to create a spinning mechanism that could be spun like a carnival wheel to create a fun way for the kids to choose which color they get to sit on. The teacher would also be able to more discretely adjust the spinner without making it super exciting or distracting so that she could refocus the children during group time.

Types of Sensors:

We considered many different kinds of sensors before landing on a final preference of the weight or Button touch sensor.

• Touch Sensor: The touch sensor is the same one that we used on our sciborg. If we were to use these in our design we would need several to be under the mat on a hard surface in order to pick up whether or not the child was on the mat. Our concerns with this approach is how comfortable the mats would be and  making sure that all parts of the section would set off the sensor. We could possibly have a layer of wood, then the sensor, then a layer of stiffer material, then the mats.
• Light Sensor: The light sensor would sense whether or not the child was blocking the light in order to figure out if they are on their mats or not. A problem with this is that the light sensor would have to be poking through the mat which would be uncomfortable and possible encourage the children to pick at it.
• Weight Sensor: We aren't sure if this is within our budget, but a weight sensor that is able to detect the weight of the child rather than just telling whether or not the button is pressed in or not, would be very useful. This way the child could be on any part of the mat and the child wouldn't be able to trick the sensor like the light sensor or possibly the button sensor.
• Color Sensor: The color sensor would be used on the spinner to see which color the arrow landed on.
• Light and Dark Sensor: The light and dark sensor could also be used to pick up the color differences between red and blue.

Moving Forward:

Our next step in this process is to go to the classroom to observe group time and run the idea behind the teacher to see if she has any concerns and to help us answer some lingering questions we have. 

MATLAB Day 2:Thermal Systems

The Assignment:
In class today we explored MATLAB further by altering mathematical models of thermal systems. The selected exercises are shown below.

Question 1: How does the cooling behavior change if we vary the parameters Rth and C?
Before increasing anything the graph looked like this with values of C=1000 and Rth=0.85...

If we increased C then the resulting graph looks like this...

If we increase Rth then the resulting graph looks like this...

If both C and Rth are increased then the graph looks like this

If we decrease C then the resulting graph looks like this...

If we decrease Rth then the resulting graph looks like this...

If both C and Rth are decreased then the resulting graph looks like this...

Based on the way the graphs above behaved Rth and C seem to make the slope more positive and more linear when increased. This makes sense intuitively because C is capacitance or the amount of heat it can hold, Rth is the thermal resistance so if the resistance is increased then the heat does not escape as easily. In both cases the heat is retained longer. When either C of Rth are decreased the function decays even more exponentially. Mathematically the expression...

Which can be rearranged to include Rth and C as shown below shows that these observations are grounded in the mathematical properties of the function...

Question 2: Calculate the value for P if we want our coffee to heat up to the Starbucks ideal 84 C.
Using the equation given in the text we were able to find P by setting dT equal to zero since as the function approaches the temperature we want, in this case 84 C (357 K) dT will approach zero. We can then simplify the expression and plug in the correct numbers.

The Code which implements this power value and the resulting graph are shown below...

Page 9: Bang-Bang and Proportional Control of Thermal Systems

1. Modify the program to stimulate a temperature controller using bang-bang control to reach the temperature. Why is bang-bang control appropriate for many thermal systems? Why might it be insufficient?

The original heatsim program is shown below...

In order to create a bang bang control system we altered the code so that if the temperature reahced the target then the power would turn off completely. If the the temperature was lower than the target then the power would turn completely on. The altered code and the resulting graph are shown below...

As you can see from the graph, once the temperature reaches the target then the power will turn on and off completely to make it oscillate sharply around the target. Bang bang control like this is common in heating systems because it allows the heater to reach the target quickly. With proportional control the temperature can never mathematically reach the target, and it takes much longer to get to a close approximation. 

2. Create a program that uses proportional control to reach and maintain the desired temperature. How does this approach compare to bang-bang control?

Our proportional control program actually reached the target faster than the bang bang control program, but that was only because the power used in the proportional program was much higher and most likely unrealistic for a real device. When we ran the program with the same power as the bang bang control it never even got close to the target within the time window, Mathematically the temperature can never reach the target because there is an asymptote. Our code and graph are shown below...

3. Modify both programs to add a sensor delay to both programs. What is the impact of this "sensor delay" on each system? What other delay(s) might you expect in your thermodynamic system, apart from sensor delays?

Shown below is the modified proportional delay program to include a sensor delay of 5 seconds. This forces the temperature to actually surpass the target temperature because by the time the program senses that the temperature has exceeded the target, the temperature has continued to rise for 5 seconds. After this the program will respond causing it to pull the temperature back down. In this way it will continue to oscillate with an increasingly subtle curve towards infinity,

The modified heatsim_banbang program to include a delay shown below changes the program by increasing the amount of time that passes before the heater is turned back on all the way to reach the target. This would prevent the heater from turning on and off too quickly preventing mechanical malfunctions that could occur as a result.

As for other forms of delays. I would say that there could be an action delay which rather than delaying how often the sensor reads the information, delaying the response to that reading. In this way the sensor would constantly be reading but the action for a given kind of stimuli would not occur until 5 seconds after the stimuli occurred if the delay was 5 seconds.

Reflection:
This set of problems really helped to ground the concept of bang bang and proportional control for me since I now have graphical/visual references for their effects. Moving forward this knowledge will be very helpful when trying to incorporate bang bang and proportional control into my final project.

MATLAB Introduction

The Assignment: 
For this assignment we read through the 1st 4 chapters of the Allen Downey's book Physical Modeling in MATLAB and completed selected exercise contained in those chapters.

Exercise 2.1: fibonacci1 script
For this first exercise we had to transform a Fibonacci sequence equation into a language that could be understood by the program. We also had to make sure that the program updated itself. We separated the equation into a part 1 (P1) and part 2 (P2) to make it easier to read.

Exercise 2.3: car_update script
For this excercise we were given a word problem which was about a car rental company with two locations, one in Boston and the other in Albany. Customers could rent cars one way, which meant that the number of cars at each location would fluctuate over time until it reached an equilibrium. Initially we had trouble making sure that the a (Albany) and b (Boston) values wouldn't update before the program had run through. This made the values only slightly off, and would have been unnoticeable if the round function had been there originally.  We fixed this by creating anew and bnew within the program then updating them at the end.

Exercise 3.1: car_loop script
With the previous script if we wanted it to run 52 times then we would have had to tell it to run over and over again 52 time. By creating a loop the program automatically runs the script 52 times then gives us the answer.

Exercise 3.2: car_loop script with plotting (also try values of a&b = 10000)
Next we plotted the car_update function we created earlier. The first time we wrote the program we wrote car_loop rather than car_update inside the for statement and the function wouldn't work. This was because we created a double loop that didn't reference our original program. Changing it to car_update gave us the correct graph.

Below is what the plot looks like if a&b = 10000 initially. Notice how smooth the curve is compared to the one above.

Exercise 3.5: fibonacci2 sequence script
WE rewrote the fibonacci sequence without all the cumbersome language we used in exercise 2.1. The range i=3:10 starts at 3 becasue if it started at 2 then the program would get stuck since f(i-2) = 0.

Exercise 4.6: plotting fibonacci ratios
We changed he f to an F to conform to the conventions of vector notation which the book talked about. we also moved the ans line out of the loop. We also created a range that has a upper limit equal to n.

Plotting the ratio proved to be very difficult. We got the golden ratio that the ration is supposed to approach, but it wouldn't plot it consecutively instead there would only be a dot in the center of the plot for the answer. Also, if we tried to plot F then it gave us the fibonacci sequence exponential curve. We addressed this problem by creating another function Y to stand for the ration. We then told it to plot Y(n) rather than Y(i) which finally gave us a fully plotted graph.

Reflection:
I found that while reading the book the operations seemed to be logical and easily applicable, however once we started trying to write code for ourselves it became difficult. AS he mentions many times throughout the first 4 chapters, often it is difficult to tell whether or not the code is executing properly or not. With the Fibonacci sequence we found ourselves having to do the math ourselves to check if it was running correctly. Also, the programming language is not terribly intuitive so we need to be especially careful about which signs and symbols we use.

Final Project Ideas

Assignment: 
In class today we observed children of two different age groups in order to brainstorm ideas for our final project that would enhance the experience of the children and their teachers while utilizing all of the skills we have learned thus far in the class, including  feedback and control methods we have been working with these past few weeks.

My Observations:
Since we only were able to observe the children for a shorter period of time I wasn't able to truly get a sense of the needs of the students and their teachers. However, the things I did notice are listed below.

• Only a certain number of children were allowed to play on a certain object at one time.
• Some kids wanted to jump from activity to activity without cleaning up after themselves
• A few of the kids got out too many toys and lost track of all of them
• The teacher had to remind the children to keep the volume down
• A few of the kids playing in the tree house-like structure threw toys off of the top through the bars. 

Teachers Suggestions:
I found the teacher's suggestions to be very useful for generating ideas since she has a more intimate knowledge of the dynamics of the class room. Her suggestions of problems to address and other important information is listed below.

• The children are very fidgety and won't stay on their carpet squares
• The children are not able to see out of the window downstairs
• The kids sometimes put things in between the cracks of the cabinets and the wall 
• They often get very loud while playing and the teacher has to constantly remind them to quiet down
• The children get so involved in playing with the water and sand tables that they don't realize that the sand and water is getting all over the floor
• The bathroom toilet flushes very loudly and scares some of the children
• The bathroom locks are confusing to the children and sometimes they are unable to get them open
• The children often forget to flush the toilet or wash their hands
• Sometimes they leave the water faucet running
• They often take more than one paper towel or piece of toilet paper

The teacher also brought to our attention some things to keep in mind after her years as a teacher about the nature of children and how that relates to our projects.

• Ideas need to be reinforced through different senses such as sight and hearing for the children to understand and remember
• Ideas need to be repeated
• Feedback should be positive when possible
• We need to make sure that the signal that our device is not so interesting that it distracts, scares or encourages the children to do the thing which we are trying to prevent.
• Educational devices are highly encouraged
• There are certain size parameters that they must abide by in order to follow safety laws
• With safety in mind, they encourage the children to engage in "risky play" which allows them to test and realize their limits

Problems/Ideas of Interest

1. Carpet Squares: As a child I was very fidgety and had a lot of trouble sitting on my carpet square, for that reason this problem interests me. The most obvious place to start with this problem it seams to be is with a touch sensor that knows when the child is or is not sitting on their carpet square 
2. Washing their hands: Hygiene and cleanliness is of vital importance to make sure that the children and teachers stay healthy. For this reason implementing a device that helps the children remember how long to wash their hands for and remind them to  
3. Noise level: Some sort of noise sensor would need to be implemented that would go off either by lighting up or some other signal. The challenge with this is to make sure the signal is not too exciting to encourage the noise or conversely to scare them. Also, there needs to be a clear correlation between the sound and the noise level that can be understood by the kids.
4. "Risky Play": I was intrigued by the idea of "risky play" but I am unsure how that could be implemented given our parameters

Reflection:
It was surprising that the teachers have chosen to purposefully limit the children's interaction with technology in the class room. I find their reasoning compelling and tend to agree for the most part that children need to be in charge of their own play and interact with the world without a screen. Seeing as the teachers are allowing us to build new electronic devices for their classroom, they are not completely against technology, rather they encourage a healthy balance. It is important to me in this design to make sure that our goals for the design align as best they can with the educational philosophy of the teacher.

Arduino Day 4: More Adventures with Frank

The Assignment:
Our challenge was to

Encoders:
The encoder is a sensor which is located inside of the Lego motor. It measures the number of times the shaft has rotated. This can be very useful in describing the position of the sciborg when trying communicate that to the code. Below is the base code that runs the encoder. When the arduino software reads the code it begins at 0 because the shaft has not rotated. As the shaft rotates the number read by the encoder becomes increasingly negative. The magnitude of the number shows the number of times it has rotated since the beginning position marked by 0.

The version below has better comments

Touch Switch:
The touch switch sensor is located on the arm of the sciborg. It is similar to the Lego button sensor explored in the the previous post, but due to its design it is generally more effective in stopping when it encounters an object. This is because the Lego button sensor is very small and is often not positioned at the appropriate angle to ensure that the obstacle pushes the button. The arm covers a larger vertical space in front of the sciborg. A sample code for this sensor is also pictured below.

In this example code, the LED light stays on forever after the button is pushed because the code never resets itself to receive any other input after the first time. We altered the code so that it would only turn on when the button was being pressed. The video and code are shown below.

 

Ultrasonic Sensor:
In my opinion, the ultrasonic sensor is the coolest sensor we have used thus far. It works in the same way that a bat uses echolocation to project a small sound wave that is then bounced back to the sensor. The distance that the sensor reads is dependent on how quickly the wave returns to the sensor. The sample code is shown below. We found that it's range is from about 6 to 280 as measured by our tests; that translates to about a distance of 2.5 - 3 meters. The sensor is most accurate to large flat objects such as a wall or board, although it is capable of picking up other objects as you will see later on in this post. The accuracy of the sensor is also affected by the periphery. We found during tests that after calibrating the sensor by pointing it into open space, that sometimes it would pick up us or the walls when we were on the outskirts of its field.

Feedback & control Activities:
Encoders: Fixed distance, bang bang control
In this activity we had to use the encoder sensors in the motor to tell the arduino to stop after 10 ft. At first we misinterpreted the challenge by assuming that the number of turns of the wheel corresponded directly to the number of the turns of the shaft. This however is not the case. Once that confusion was sorted out though, we were able to write a code that accomplished what we wanted it to. Our original 10 ft code is directly below and the improved encoder bang bang code is under that.

Button Sensor: Fixed distance, bang bang control
Next we used the button sensor to make Frank travel 10 ft then stop. We just altered the code we wrote earlier for the button sensor slightly. In order for this code to work though there needs to be an obstacle to at the 10 ft mark to push the button sensor.

Ultrasonic Sensor: Fixed distance, bang bang control
Next we wrote a code that would make Frank travel forward until he sensed something close enough in his path as measured by the ultrasonic sensor. We had a lot of trouble initially writing this code because the ultrasonic sensor wouldn't run while the motor was running. We found that the solution was simply to change the while to an if statement.

We then used this code to create a konga line code that relied on bang bang control

Encoder: Fixed Distance, Proportional Control
Our next challenge was to alter the codes so that they were proportional control rather than bang bang. proportional control allows us to gradually slow down the motor based on the input from the various sensor rather than just turning off the motor entirely. In order to do this we had to understand that proportional control must be written in terms of output=error*gain where output=(goal - measurement)*gain. Once this was explained to us we were able to write a code using proportional control.

Ultrasonic: Fixed Distance, Proportional Control...KONGA LINE!!!
The ultrasonic proportional code is written so that if the object in front of it is within a certain range picked up by the ultrasonic sensor then the motor's speed increases, but if it it is too close then a bang bang control back up is implemented to make sure the car does not run into the car in front of it a konga line is.

Reflection: 
After this project I feel that I have gained a better understanding of the coding language which I think will serve me well as I begin to consider the problems related to my final project. That being said, there is so much that I have yet to understand fully about the coding language, so it will continue to be a challenge to work with it.