Question

Hello, I have a lab that we have used bending sense in our hand joint and we build a voltage decider to record voltage change as angle of hand joint change as number (4) said : I did record my values in a table1 below. However, I need help in number (5). How would I plot these values in Matlab ? can some one help me plotting what is asked in #5 ? I need help in this Matlab coding plotting part that they ask about in #5. Thank you

4. Build the voltage divider on a breadboard in the Electronics Lab with a +1.5 V excitation voltage. Perform a calibration between joint angle and output voltage by changing joint angle in 15°-steps between 0 - 90° and recording output voltage. Perform two sets of measurements, first increasing from 0° and then decreasing from 90% Provide these tables 5. Plot the data (use different symbols or colors for the increasing/decreasing data sets). Do you see any hysteresis? Fit a calibration function to all of the data using the MATLAB command "fit". Create the function such that an angle will be computed for a measured voltage. Try first-, second-, and third-order polynomials. Write the estimated equation for each and compare R2 and RMSE values for each. Plot the curve for the model which best fits the data on a graph with the actual data points.

Table (1)

Answer 1

The code for plotting the data is

angle=[0:15:90];%means angle starts from 0, increments by 15 until angle is 90
inc=[0.35 0.37 0.385 0.55 0.82 0.91 0.95];
dec=[0.35 0.39 0.4 0.45 0.54 0.88 0.96];
plot(angle,inc,'r',angle,dec,'g'); %plot angle on x axis and inc on y axis with red color and dec with green color

The plot looks like

As you can see in the graph, there is hysterisis. Hysterisis means the forward and reverse path are not the same and the direction in which the values are changing (inc or dec) also effects the quantity.

To fit the curves properly, use "cftool" command in matlab and you can try fitting it to different functions, This opens a graphical window where you can see the fitted curves and it is really interesting.

We will use the avg of both inc and dec to fit into a function

Code:

angle=[0:15:90];%means angle starts from 0, increments by 15 until angle is 90
inc=[0.35 0.37 0.385 0.55 0.82 0.91 0.95];
dec=[0.35 0.39 0.4 0.45 0.54 0.88 0.96];
avg=(inc+dec)/2
plot(angle,inc,'r',angle,dec,'g',angle,avg,'b');

Now the blue line shows the average of inc and dec

now type the command "cftool" to open the cftool

select x and y variables as angle and avg respectively. and choose different fitting functions

All the data required is present in the screenshots

All the requested data is present in the screen shots.

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