UnityでアームロボットIK

前回のアームロボットシミュレーションに逆運動学(Inverse Kinematics)を導入してみました。スライダーでアーム先端の位置と姿勢（６軸）を指定するとロボットがこれを満足するように動きます。

IKの計算は広瀬著「ロボット工学」を参考にしました。あまり広範囲には動かせないようにしていますのでとりあえずうまくいっているようです。

public class CalcIK : MonoBehaviour {

    public Slider S_Slider;    //PositionX min=4 max=12
    public Slider L_Slider;    //PositionY min=-4 max=4
    public Slider U_Slider;    //PositionZ min=4 max=12
    public Slider R_Slider;    //RotationX min=-90 max=90
    public Slider B_Slider;    //RotationY min=-90 max=90
    public Slider T_Slider;    //RotationZ min=-90 max=90
    public static double[] theta = new double[6];    //angle of the joints

    private float L1, L2, L3, L4, L5, L6;    //arm length in order from base
    private float C3;

    // Use this for initialization
    void Start () {
        theta[0] = theta[1] = theta[2] = theta[3] = theta[4] = theta[5] = 0.0;
        L1 = 4.0f;
        L2 = 6.0f;
        L3 = 3.0f;
        L4 = 4.0f;
        L5 = 2.0f;
        L6 = 1.0f;
        C3 = 0.0f;
    }
	
	// Update is called once per frame
	void Update () {
        float px, py, pz;
        float rx, ry, rz;
        float ax, ay, az, bx, by, bz;
        float asx, asy, asz, bsx, bsy, bsz;
        float p5x, p5y, p5z;
        float C1, C23, S1, S23;

        px = S_Slider.value;
        py = L_Slider.value;
        pz = U_Slider.value;
        rx = R_Slider.value;
        ry = B_Slider.value;
        rz = T_Slider.value;

        ax = Mathf.Cos(rz * 3.14f / 180.0f) * Mathf.Cos(ry * 3.14f / 180.0f);
        ay = Mathf.Sin(rz * 3.14f / 180.0f) * Mathf.Cos(ry * 3.14f / 180.0f);
        az = -Mathf.Sin(ry * 3.14f / 180.0f);
        
        p5x = px - (L5 + L6) * ax;
        p5y = py - (L5 + L6) * ay;
        p5z = pz - (L5 + L6) * az;

        theta[0] = Mathf.Atan2(p5y, p5x);

        C3 = (Mathf.Pow(p5x, 2) + Mathf.Pow(p5y, 2) + Mathf.Pow(p5z - L1, 2) - Mathf.Pow(L2, 2) - Mathf.Pow(L3+L4, 2))
            / (2 * L2 * (L3+ L4));
        theta[2] = Mathf.Atan2(Mathf.Pow(1 - Mathf.Pow(C3, 2), 0.5f), C3);

        float M = L2 + (L3+ L4) * C3;
        float N = (L3+ L4) * Mathf.Sin((float)theta[2]);
        float A = Mathf.Pow(p5x*p5x + p5y*p5y, 0.5f);
        float B = p5z - L1;
        theta[1] = Mathf.Atan2(M*A - N*B, N*A + M*B);

        C1 = Mathf.Cos((float)theta[0]);
        C23 = Mathf.Cos((float)theta[1] + (float)theta[2]);
        S1 = Mathf.Sin((float)theta[0]);
        S23 = Mathf.Sin((float)theta[1] + (float)theta[2]);

        bx = Mathf.Cos(rx * 3.14f / 180.0f) * Mathf.Sin(ry * 3.14f / 180.0f) * Mathf.Cos(rz * 3.14f / 180.0f)
            - Mathf.Sin(rx * 3.14f / 180.0f) * Mathf.Sin(rz * 3.14f / 180.0f);
        by = Mathf.Cos(rx * 3.14f / 180.0f) * Mathf.Sin(ry * 3.14f / 180.0f) * Mathf.Sin(rz * 3.14f / 180.0f)
            - Mathf.Sin(rx * 3.14f / 180.0f) * Mathf.Cos(rz * 3.14f / 180.0f);
        bz = Mathf.Cos(rx * 3.14f / 180.0f) * Mathf.Cos(ry * 3.14f / 180.0f);

        asx = C23 * (C1 * ax + S1 * ay) - S23 * az;
        asy = -S1 * ax + C1 * ay;
        asz = S23 * (C1 * ax + S1 * ay) + C23 * az;
        bsx = C23 * (C1 * bx + S1 * by) - S23 * bz;
        bsy = -S1 * bx + C1 * by;
        bsz = S23 * (C1 * bx + S1 * by) + C23 * bz;

        theta[3] = Mathf.Atan2(asy, asx);
        theta[4] = Mathf.Atan2(Mathf.Cos((float)theta[3]) * asx + Mathf.Sin((float)theta[3]) * asy, asz);
        theta[5] = Mathf.Atan2(Mathf.Cos((float)theta[3]) * bsy - Mathf.Sin((float)theta[3]) * bsx,
            -bsz / Mathf.Sin((float)theta[4]));
    }
}

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