Drives #

The type of a constraint describes the interactions of two nodes. Using only the core module the type can be set as free or const to allow or disallow motion respectively. mec2.drive allows this type to be set as drive as well. A constraint of type drive has a determined motion, which allows linkages with one degree of freedom to be fully determined.

Further properties can be provided to describe the motion (all angles in radiant):

• func: The function used to describe the motions. Default is linear. A lot of other functions are implemented after VDI 2145, as well as web easing functions.
• ref: Use the angle of another constraints as reference.
• Dw: Angle of rotation. Default: 2 * Math.PI.
• t0: Time in milliseconds when to start the drive, after model initialization.
• Dt: Time needed for one turn.
• bounce: Perform a reversed motion after each interval (bounce is issued between repetitions).
• repeat: Repeat the motion this many times.
• args: Arguments for sequential functions. Implemented in the second example.

Using combinations of these properties a variety of motions can be described.

Example: #

{
    "nodes": [
        {
            "id":"A0", "x": 200, "y": 40, "base": true
        }, {
            "id":"A", "x": 200, "y": 140
        }
    ],
    "constraints": [
        {
            "id":"a","p1":"A0","p2":"A",
            "len":{"type":"const"},
            "ori":{"type":"drive","repeat":10,"Dt":3 }
        }
    ]
}  

- Drive Sequence

Drive functions can be composed as a sequence ('func':'seq') of normalized functions, being one of ['const', 'linear', 'quadratic', 'harmonic', 'sinoid', 'poly5'] each. Every segment of a drive sequence must specify its function type func, its duration dt (always positive) and its value range dz (might be negative).

{
    "nodes": [
        {"id":"A0","x":175,"y":125,"base":true},
        {"id":"A1","x":175,"y":225}
    ],
    "constraints": [
        { "id": "a", "p1": "A0", "p2": "A1",
          "len": { "type": "const" },
          "ori": { "type": "drive", 
          "Dt": 3, "Dw": -3.14, "repeat":2,
          "func": "seq", "args": [
            { "func": "quadratic", "dt": 3, "dz": 1 },
            { "func": "const", "dt": 1 },
            {"func": "linear", "dt": 3, "dz": -1 }]
        }
    }]
}

{
    "nodes":[
        { "id": "A0", "x": 100, "y": 125, "base": true },
        { "id": "B", "x": 175, "y": 125 },
        { "id": "B0", "x": 250, "y": 125,"base": true },
        { "id": "A", "x": 175, "y": 125 }
    ],
    "constraints":[
        { "id": "b", "p1": "B0", "p2": "A",
          "len": { "type": "const" },
          "ori": { "type": "drive", "repeat":3 }
        },
        { "id": "c", "p1": "A0", "p2": "B",
          "len": {"type": "const" },
          "ori": { "type": "const", "ref":"b"}
        }
    ]
}