48 lines
2.6 KiB
Markdown
48 lines
2.6 KiB
Markdown
## Analysis for Motion Tracking System on the Pepper Robot.
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---
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For our project, we want our users to be able to see the movement they're making, so they can
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see whether they're executing the fitness task correctly. For a tracking system as such, we'll need to use quite
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some mathematics.
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Our current approach is defining the required path by a set of vertices; points in 3d space.
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These points define along which path the user has to move their limbs to, depending on what the activity is
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and where they've placed the tracking devices.
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A path can look like the following
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<img height="128" src="../assets/motion-path-example-vertices.png" width="128"/>
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To be able to measure the position of our tracking device, we'll have to use sensors that allow us
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to retrieve useful information that can provide us with either position or velocity. The device will have
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to be calibrated initially, of course, due to position being relative.
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To acquire our measurements, we've chosen for the following configuration for the tracking device:
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- ESP8266 (Wi-Fi only)
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- Accelerometer / Gyroscope combination (BNO085)
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We've chosen for this configuration due to the fact that it delivers all of our needs, with the smallest form factor,
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whilst also delivering quality measurements.
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This sadly does come at the cost that the ESP8266 does not have a dedicated Bluetooth chip, therefore making
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connectivity to our robot a little more complicated.
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The calculations behind the tracking system will be done in the following steps:
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1. Acquire calibration point (zero point)
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2. Convert relative acceleration and rotation to position, relative to the calibration point
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3. Generate a path object that can be compared to the correct one
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4. Calculate the difference of the path at every measurement sample
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At first, to get the calibration point, the user will have to stand still for a moment without moving.
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This can be sensed by the device, which will then be sent to the Pepper robot.
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We've decided to send this data using Wi-Fi using a HTTP WebSocket connection, due to the fact that our
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ESP8266 does not have a Bluetooth chip present, and due to the fact that a WebSocket connection allows us
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for a both fast and secure data transfer.
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Second, to convert our relative acceleration rotation to a useful position, we'll have to first convert the
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acceleration vector `A(x, y, z)` and rotation vector `R(x, y, z)` to an acceleration vector that is
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perpendicular to the normal vector of the earth. This is because the acceleration vector of the device
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is relative to its own axes, and not to the earth's normal vector.
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To convert this, we'll have to multiply the acceleration vector `A(x, y, z)` by the rotation matrix |