Lab 1

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Pennsylvania State University *

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111

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Mechanical Engineering

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Oct 30, 2023

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docx

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GETTING MOVING Lab goals: 1) Exploring the operation of the IOLab: Wheel Position Sensor 2) Exploring the concept of position, velocity and acceleration Instructions: Enter your answers by typing below the solid line after each question. If you wish to use a different color text to make sure your answer stands out, feel free to do so. Include pictures by copy pasting them in this file. Pictures can be snapshot of IOLab data, Excel tables or even pictures of handwriting drawing. Save the file and submit to canvas (either as word or as a pdf). Important Notes About Displaying Graphs: You rarely show all your raw data when presenting a graph. For example, you may have started the data collection before you released the cart and stopped the data collection after the experiment ended. Or just part of your data is relevant for the question you are answering. You usually want your graph to (a) focus on just the relevant data (if you include it all, it suggests that you didn’t know what data really was relevant) and (b) use the full “real estate” of the graph. Compare, for example, the two graphs below – which is easier to read and interpret?

Getting Moving p. 2 of 9 ACTIVITY 1: EXPLORING THE OPERATION OF THE IOLAB: WHEEL POSITION SENSOR The purpose of this activity is to investigate the use of the IOLab’s Wheel Position Sensor The set of three wheels on the IOLab measures the displacement, velocity and acceleration of the cart as a function of time. Sampling : The sampling rate of a measuring device is the number of measurements it makes per second. The IOLab is an extremely sensitive device with a high sampling rate for all of its sensors. As such, it takes a lot of data per second and you do not need to perform very big motions to get interesting data! Be gentle! The sampling rate for the wheel is 100 Hz or 100 measurements per second. Because of this high sampling rate, data you obtain will often not be smooth and may have some small perturbations. Some of these jagged features may be instrumental (i.e. noise) but most of the small spikes are real perturbations! Real life data is often messy like that. Since we are often interested in the overall motion and not the very small bumps due to dust on the table, we can smooth the data. We can get a smoother line by using the Data smoothing option. A data smoothing of 5 will average 5 data points before displaying on the graph. Data smoothing of 1 is the raw data. Let’s take some data! 1. From the list of sensors select Wheel and keep the data smoothing at 5. (Smoothing can be accessed through the Tool bar at the bottom of the graph.) 2. Click record and move the cart steadily back and forth a few times so that you get a graph like this one: (you will need to unclick the velocity and acceleration boxes).

Getting Moving p. 3 of 9 You can zoom in the data by using the zoom tool (select an area of the data that you want). Let’s explore the basic motion of the IOLab first. 1. What is name of the axes along which you move the device? What is the name given to that variable in the IOLab software? What is the origin of this coordinate system? Does it reset when you stop and restart taking data (do not reset all the data, just stop and restart, the data screen should stay there)? What does the button “Rezero sensor” do? The devices moves along its Y-axis. The name the software gives this variable is “t Y ”. The origin point of this coordinate system is 0. The graph does not reset when stopping and restarting to record the data. The rezero sensor sets the tracker on the graph back to zero no matter where it is on the graph to act as the new point of origin. 2. In which way is the position reported by the wheel sensor indicating direction of motion? What happen when you rotate the IOLab around (lift it up, do a 180 degree rotation and put it back down and roll)? The position reported by the wheel sensor moves to the positive(+) Y coordinate when the device is moved in the direction where the Y arrow (on the device) points. Picking up the device, rotating it 180°, placing it back down, and pushing back to its origin point will record data as if it was continuing on in the same direction, I.e. if its traveling along the +Y, lifted and turned 180°, then set back Note: You can “unzoom” and see all the data by simply clicking without selecting anything while the zoom tool is selected.

Getting Moving p. 4 of 9 down and pushed back to start the device will continue to record a position moving in the +Y. For the next set of problems, you will be asked to reproduce a motion with your IOLab. We highly recommend making relatively large motions so that you can better see features. Also, you will be asked to plot position, velocity and acceleration. Rather than using IOLab notation r y (t) for position, we will refer to r y (t) as the y(t) graph from now on . The coordinate system x,y,z is “attached to” the IOLab, you can see it drawn on the device. In this lab, we will reproduce one dimensional motion along the wheel which is the y direction in the IOLab coordinate system. Turning around in 1 dimension means you are going in the positive y direction and then negative y direction. For the IOlab, this means forward then backward. Do not turn the iOlab itself as you would still be going in the same y direction. First, here is a motion diagram for simple linear motion. This is one-dimensional motion but because we backtrack we split the motion diagram on two lines to help us visualize it. Check the velocity and displacement (red and green) curves, and reset the origin so that your motion begins at y = 0. 3. Reproduce this motion with the IOLab and include a snapshot of your y(t) and v y (t) graphs here . Describe in words the motion you made. The motion made was a quick acceleration from point 0  point 1 with an equally quick slow down from points 1  5. From points 5  11 the acceleration was gradual slowly increasing in speed along the way back.

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