搞不明白是什么错误。。。。

ERROR: At time 5.999999994E+00 the integrator is unable to proceed. Possible Causes:
(1) The accuracy required for the numerical solution can not be attained.
Relax (increase) the value of the acceptable integration ERROR.
(2) Incompatible redundant constraints, a lock up, or a bifurcation
situation. The latter two indicate a mechanism design problem.
(3) The system includes a zero (or relatively small) mass on a part with
an unconstrained translational degree of freedom.
Make sure you have mass on all parts with translational degrees of freedom.
(4) The system includes a zero (or relatively small) inertia on a part
with an unconstrained rotational degree of freedom.
Make sure you have inertias on all parts with rotational degrees of freedom.
(5) An Adams element has a function expression that equals exactly itself.
For example,
SFORCE/id1,I=id2,J=id3,ROT,FUNC=SFORCE(id1,jflag,comp,rm),and
DIFF/id4,IMPLICIT,IC=0,FUNC=DIF1(id4).
Similarly,
VARIABLE/id5, FUNC=VARVAL(id5)*TIME
equals itself at 1 second. Avoid setting an Adams element equal to itself.
上面是错误提示，搞不明白到底什么错误，我运行的是几个关节的联合运动，本来只有6秒得控制，后来我想加入6秒之后的控制，结果就这样的错误了，高手帮忙看看是什么错误
下面是其中一个关节的控制函数，几个关节的控制函数差不多
if((time-5):-(pi-acos((700*700+430*430-(dx(marker_3,marker_27)*dx(marker_3,marker_27)+dy(marker_3,marker_27)*dy(marker_3,marker_27)))/(2*700*430)))*time/5,-(pi-acos((700*700+430*430-(dx(marker_3,marker_27)*dx(marker_3,marker_27)+dy(marker_3,marker_27)*dy(marker_3,marker_27)))/(2*700*430))), if((time-6):-(pi-acos((700*700+430*430-(dx(marker_3,marker_27)*dx(marker_3,marker_27)+dy(marker_3,marker_27)*dy(marker_3,marker_27)))/(2*700*430))),3d*time,3d*time))
我感觉可能是最后这句有什么问题，但是搞不明白。。。