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Expand on Robot Config documentation
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# Robot Config | ||
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Both the GUI and PathPlannerLib require various configuration options to be set in order to generate trajectories that | ||
are accurately limited for the performance of your robot. All of these values have an effect on the performance of your | ||
robot, determining its maximum velocity, acceleration, etc. Therefore, you should take care to ensure that these options | ||
are configured as accurately as possible. | ||
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## Robot Config Options | ||
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Robot Mass | ||
: The mass of the robot, including bumpers and battery, in Kilograms. In most cases, choosing the maximum robot weight | ||
of ~68 KG (150 lbs) will work fine. However, lightweight robots may benefit from increased acceleration and better | ||
friction estimates if the robot mass is measured accurately. | ||
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Robot MOI | ||
: The Moment of Inertia, or MOI, of the robot, including battery and bumpers. This can be calculated via CAD software, | ||
or measured in various ways. | ||
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### Calculating MOI through sysID (Recommended) | ||
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Once sysID has been performed, the robot's MOI can be calculated using the following formula: | ||
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$$ | ||
\begin{equation} | ||
I = \text{mass} * \frac{\text{trackwidth}}{2} * \frac{kA_{\text{angular}}}{kA_{\text{linear}}} | ||
\end{equation} | ||
$$ | ||
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Where $kA_{\text{angular}}$ is the acceleration constant of the drive motors while rotating the robot, | ||
and $kA_{\text{linear}}$ is the acceleration constant of the drive motors while driving straight. | ||
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### Calculating a Rough MOI Estimate | ||
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The robot's MOI can be roughly estimated using the following formula: | ||
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$$ | ||
\begin{equation} | ||
I = \frac{1}{12} * \text{mass} * (\text{length}^2 + \text{width}^2) | ||
\end{equation} | ||
$$ | ||
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However, this will likely lead to an inaccurate estimate as it assumes a uniform distribution of mass. | ||
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Wheelbase | ||
: The distance between the front and back of the drivebase, in meters. Only relevant in holonomic mode. | ||
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Trackwidth | ||
: The distance between the left and right sides of the drivebase, in meters. | ||
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## Module Config Options | ||
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Wheel Radius | ||
: The radius of the drive wheels, in meters. This should be listed wherever you buy your wheels from, but can also be | ||
measured. | ||
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Drive Gearing | ||
: The gear reduction from the motors to the wheels. Since this is a reduction, this value should be greater than 1. For | ||
example, the gearing of an SDS MK4i module with L3 gearing is ~6.12 | ||
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True Max Drive Speed | ||
: The true maximum speed of the robot/drive module while driving under load, in meters/second. | ||
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> **Note** | ||
> | ||
> It is very important that the True Max Drive Speed is measured for your actual robot. This value is not simply a "max | ||
> velocity" limit on the robot. It encodes information about how much motor torque can actually be used to accelerate the | ||
> robot. | ||
> | ||
> This can be easily measured by driving the robot in a straight line as fast as possible on a charged battery, and | ||
> measuring the robot's maximum velocity. | ||
> | ||
> However, this test requires a lot of space and access to the robot. If you are unable to measure this value, it can be | ||
> estimated by using about 85% of the module's free speed. | ||
> | ||
{style="note"} | ||
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Wheel COF | ||
: The coefficient of friction between the drive wheels and the carpet. Some wheels will have their COF listed on their | ||
store page. The COF of friction can also be calculated by measuring how much force is required to pull the robot ( | ||
causing the wheels to slide) across the carpet. You can also tune this number until the wheels no longer slip while | ||
accelerating or turning in corners. | ||
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Drive Motor | ||
: The type of motor used to drive the wheels of the robot. | ||
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Drive Current Limit | ||
: The supply current limit applied to the drive motor controllers, in Amps. |
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