angle = theta2 - theta1;
    helical_length = hypot(angle * radius, axis_len);
    thelix = fabs(helical_length / ini_maxvel);
    //helix_angle = atan2((radius * angle),axis_len);
    radial_vel = radius * angle / thelix;
    //find the centripetal acceleration of the helix
    centripetal_acc = radial_vel * radial_vel / radius;
    acc = MIN(acc, centripetal_acc);
    printf("angle: %g\n helical_length: %g\n thelix: %g\n radial_vel: %g\n centripetal_acc: %g acc: %g", angle, helical_length, thelix, radial_vel, centripetal_acc, acc);