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= User guide (git) =

''This documentation tries to follow the developement version of Py4bot. It may or may not be up-to-date.''

For installation instructions, see [InstallationGuide here].

== Usage overview ==

As Py4bot is a framework, you will find here a description of the main things you need to understand to write your own applications.

Together with this page, have a look at the [htdocs:api/index.html complete API].

== Architecture ==

The main parts of the framwork are:

* the robot itself;
* the gait sequencer;
* some remote controllers.

== Geometry definition ==

There are several coordinates systems involved when computing maths in order to make a robot walk; it is important to understand how they are defined. All these systems are cartesian.

=== Ground coordinates system ===

This coordinates system is attached to the ground; it is a fixed referential.

* the origin is somewhere on the ground
* X and Y axes define a plane parallel to the ground
* Z axis points up

=== Robot coordinates system ===

This coordinates system is attached to the robot itself.

* the origin is at the center of the robot
* X and Y axes define a plane parallel to the ground, so that Y axis is the back-to-front axis of the robot
* Z axis points up

In the ground coordinates system, the robot coordinates system is just translated in the X/Y plane, and rotated arround Z.

=== Body coordinates system ===

This coordinates system is attached to the body. It is defined in the ground coordinates system.

* the origin is at the center of the body
* X and Y axes define a plane parallel to the body, so that Y axis is the back-to-front axis of the body
* Z axis is orthogonal to X/Y

This system is used to define the position of the body in the robot coordinates system, allowing it to move along the 6 DoF (3 translations, 3 rotations).

=== Legs coordinates systems ===

This coordinates systems are attached to the legs, so each leg has its own coordinates system. They are defined in the body coordinates system.

* the origin is at the origin of the leg (usually the coxa joint)
* X axis is along the coxa of the leg
* X and Y axes are in the same plane as the one defined by the body X/Y axes
* Z axis is orthogonal to X/Y

To summurize, in the body coordinate system, the legs coordinates systems are just translated in the X/Y plane, and rotated arround Z.

The origin of a leg is defined as following:

[[Image(body_legs.png, 500px, nolink)]]

''Todo: improve drawing''

=== Inverse Kinematic ====

==== 3 DoF legs ====

[[Image(IK3DoF.png, 500px, nolink)]]

==== 4 DoF leg ====

[[Image(IK4DoF.png, 500px, nolink)]]

== Robot ==

== Drivers ==

=== Servos calibration ===

You can use the '''{{{py4bot-gui-servocal.py}}}''' to fine tune your servos calibration, and generate the {{{SERVOS_CALIBRATION}}} dict.

[[Image(py4bot-gui-servocal.png, 500px, nolink)]]

== Gaits ==

== Controllers ==

=== Add a new Frontend ===