Changes between Version 19 and Version 20 of UserGuideGit


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Timestamp:
Apr 7, 2016, 1:25:33 PM (10 years ago)
Author:
fma
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  • UserGuideGit

    v19 v20  
    2525There 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.
    2626
    27 === Ground coordinates system ===
    28 
    29 This coordinates system is attached to the ground; it is a fixed referential.
    30 
    31 * the origin is somewhere on the ground
    32 * X and Y axes define a plane parallel to the ground
    33 * Z axis points up
    34 
    3527=== Robot coordinates system ===
    3628
    3729This coordinates system is attached to the robot itself:
    3830
    39 * the origin is at the center of the robot
    40 * X and Y axes define a plane parallel to the ground, so that Y axis is the back-to-front axis of the robot
     31* the origin is at the center of the robot, in the ground plane
     32* X and Y axes are in the ground plane
     33* Y axis is the back-to-front axis of the robot
    4134* Z axis points up
    42 
    43 In the ground coordinates system, the robot coordinates system is just translated in the X/Y plane, and rotated arround Z.
    4435
    4536=== Body coordinates system ===
    4637
    47 This coordinates system is attached to the body. It is defined from the ground coordinates system:
     38This coordinates system is attached to the body. It is defined from the body coordinates system:
    4839
    4940* the origin is at the center of the body
    50 * X and Y axes define a plane parallel to the body, so that Y axis is the back-to-front axis of the body
     41* X and Y axes define a plane parallel to the body
     42* Y axis is the back-to-front axis of the body
    5143* Z define the top side of the body
    5244
    … …  
    5749This coordinates systems are attached to the legs, so each leg has its own coordinates system. They are defined from the body coordinates system:
    5850
    59 * the origin is at the origin of the leg (usually the coxa joint)
     51* the origin is at the coxa joint
     52* X and Y axes define a plane parallele to the body
    6053* X axis is along the coxa of the leg
    61 * X and Y axes are in the same plane as the one defined by the body X/Y axes
    62 * Z axis is orthogonal to X/Y
     54* Z points up
    6355
    64 To summurize, from the body coordinate system, the legs coordinates systems are translated by '''(x, y)''' in the X/Y plane and rotated by '''gamma''' arround Z.
     56To summurize, from the body coordinate system, the legs coordinates systems are translated by '''(x, y)''' and rotated by '''gamma''' arround Z.
    6557
    6658The origin of a leg is defined as following, from the body coordinates system:
    … …  
    7264=== Gait coordinates system ===
    7365
    74 ''Or use feet coordinates system?''
     66''Or feet coordinates system?''
    7567
    76 There is the last coordinates system, which is used by the gaits, to make to robot walk.
     68There is the last coordinates system, which is used by the gaits, to make to robot walk. They are defined from the robot coordinates system:
    7769
    78 This coordinate systems is defined from the robot coordinates system, and only translated along body X/Y axes:
     70* the origins are at the center of the feet, in the ground plane
     71* X and Y axes are in the ground plane
     72* Y axis is the back-to-front axis of the robot
     73* Z axis points up
     74
     75To summurize, from the robot coordinate system, the gaits coordinates systems are translated by '''(x, y)'''.
    7976
    8077=== Misc notes ===