Chapter 1 - Objectives
- Examine how to describe a body's position
- Define how to determine the number of independent quantities (called degrees of freedom) necessary to describe a point or a body in space
- Define how to measure and calculate changes in linear position (displacement) and the time derivatives velocity and acceleration.
- Describe how to present the results of a kinematic analysis
- Explain how to directly measure position, velocity, and acceleration by using motion capture systems or transducers
DESCRIPTION OF POSITION
Is a runner 60 m from the start or 40 m from the finish?
Line up on the 20 yd line.
What is the position of my knee?
x, y, z, θx, θy, and θz
- How many camera views are needed to obtain x, y data?
- How many camera views are needed to obtain x, y, z data?
- How many points are needed to obtain θx, θy, and θz?
- Scaling Rod
- s = actual length (m) / digitized length (pixels)
- x = su
- y = sv
- Practice with Dartfish
Distance:The length of a curve or line
Displacement: Change of position (Straight-line distance from start to finish)
- Speed: Distance / Time
- Velocity: Displacement / Time
- Acceleration: Velocity / Time
A Projectile is any body that has been set on its path by some force and continues in motion by its own inertia. (Gravity has a major effect on motion).
Examples of Projectiles include: Arrow, Basketball, Shotput, Human Body,Tigers
Let's begin simply with purely vertical motion
Now let's add horizontal motion
Horizontal and vertical components are independent
Equations of motion for projectiles
Characteristics of projectiles
Demonstration on what happens as initial conditions are altered
Another projectile cartoon
Initial Velocity of Projectile
V = 20 m/s
at 27 degrees
from a height of 5m
|Flight Time = ?
Maximum Height = ?
Horizontal Displacement = ?
Shot Put Example
METHODS FOR MEASURING AND ESTIMATING BODY SEGMENT PARAMETERS
- Cadaver studies
- Mathematical modeling
- Scanning and imaging techniques
- Kinematic studies
Segment mass = mass% (total mass)
Segment center of mass = proximal + length% (distal - proximal)
- xcm = xproximal + length% (xdistal - xproximal)
- ycm = yproximal + length% (ydistal - yproximal)
Calculating center of mass in a person
Practice calculating the center of mass in this situation
Moment of Inertia
Center of mass while airborne
Online Book chapters 8 and 9
DIRECT LINEAR TRANSFORMATION
A procedure for generating three-dimensional data from multiple two-dimensional images.
- For camera 1, we can obtain two equations relating to the three-dimensional object space.
- The L's represent camera constants (DLT parameters). In order to find out the values for the camera constants, we must have at least 11 unique equations. If we film enough points in the object space from at least two unique camera views, we can accomplish this.
- Typically, at least two cameras are used with at least 8 "control points" in the field of view.
- What is the minimum number of control points to solve the 11 camera constants?
- What is the benefit to using additional control points and camera views?
- Once the camera constants are solved, other objects in the object space can be filmed and three-dimensional coordinates (x, y, z) can be determined.
- What is the minimum number of cameras to solve for x, y, and z?
- What is the benefit to using additional camera views?
Objectives: Cameras and optics
- Demonstrate an understanding of (and how they interact with each other)
- Depth of field
- Exposure time
- Shutter speed
- Frame rate
- Demonstrate an understanding of how video information is stored
- Demonstrate how to adjust the above characteristics on typical digital video cameras
- Field of View
- Exposure Time
- Frame Rate
- Depth of Field
- Focal Length
|Standard Photographic Apertures, Exposure Times, and Film Speeds
|Exposure time (s)
|Film Speed (ISO or ASA)
|APEX stands for the Additive Photographic Exposure System. Each increase in APEX value indicates a decrease in the light level by one-half.
Each faster film speed requires half the amount of light that the previous speed needed for proper exposure.
- Motion Blur
- Field of View and Aperture
00000000 = 0 00000001 = 1 00000010 = 2 00000011 = 3 00000100 = 4 00000101 = 5
11111111 = 255
-Photoshop Example of RGB data
- Data rate of 25Mbps = 3.125MB/s
- 1 frame of video = 720 x 480 = 345,600 pixels
- 30 frames of video per second
- 60 fields of video per second
- This would be 345,600 pixels (8 bytes x 3 colors) x 30 frames = 248Mbps = 31 MB/s
- 2,073,600 pixels (8 bytes x 3 colors) x 30 frames = 1492.99 Mbps = 186.6 MB/s
Ultra HD 4320p
- 33,177,600 pixels (8 bytes x 3 colors) x 60 frames = 47775.7 Mbps = 5971.97 MB/s
- Class 2 - 2 MB/s
- Class 4 - 4 MB/s
- Class 6 - 6 MB/s
- Class 10 - 10 MB/s
Ball toss filtered
Giant swing with macro