各位大佬好，我建了一個模型，拉索牽引水管的模型，拉索建立的桁架單元，水管建立的實體單元，兩者通過MPC的PIN約束，控制點選取桁架單元端點，從節點選擇水管的一端上端面。提交作業時，報錯顯示桁架單元已經被其他方程消除了  MPC，剛體，運動耦合約束。

   所以我想請教一下大神們，那我要在實體和桁架單元間 施加pPIN約束要怎么做？？？

  

DAT文件報錯如下：

***ERROR: DEGREE OF FREEDOM 2 DOES NOT EXIST FOR NODE 7720 INSTANCE 

           LASUOFENXI-1-1. IT HAS ALREADY BEEN ELIMINATED BY ANOTHER EQUATION, 

           MPC, RIGID BODY, KINEMATIC COUPLING CONSTRAINT, TIE CONSTRAINT OR 

           EMBEDDED ELEMENT CONSTRAINT. THE REQUIRED MPC (TYPE PIN) CANNOT BE 

           FORMED.

 ***ERROR: DEGREE OF FREEDOM 3 DOES NOT EXIST FOR NODE 7720 INSTANCE 

           LASUOFENXI-1-1. IT HAS ALREADY BEEN ELIMINATED BY ANOTHER EQUATION, 

           MPC, RIGID BODY, KINEMATIC COUPLING CONSTRAINT, TIE CONSTRAINT OR 

           EMBEDDED ELEMENT CONSTRAINT. THE REQUIRED MPC (TYPE PIN) CANNOT BE 

           FORMED.

 ***ERROR: DEGREE OF FREEDOM 1 DOES NOT EXIST FOR NODE 7721 INSTANCE 

           LASUOFENXI-1-1. IT HAS ALREADY BEEN ELIMINATED BY ANOTHER EQUATION, 

           MPC, RIGID BODY, KINEMATIC COUPLING CONSTRAINT, TIE CONSTRAINT OR 

           EMBEDDED ELEMENT CONSTRAINT. THE REQUIRED MPC (TYPE PIN) CANNOT BE 

           FORMED.

 ***ERROR: DEGREE OF FREEDOM 2 DOES NOT EXIST FOR NODE 7721 INSTANCE 

           LASUOFENXI-1-1. IT HAS ALREADY BEEN ELIMINATED BY ANOTHER EQUATION, 

           MPC, RIGID BODY, KINEMATIC COUPLING CONSTRAINT, TIE CONSTRAINT OR 

           EMBEDDED ELEMENT CONSTRAINT. THE REQUIRED MPC (TYPE PIN) CANNOT BE 

           FORMED.

 ***ERROR: DEGREE OF FREEDOM 3 DOES NOT EXIST FOR NODE 7721 INSTANCE 

           LASUOFENXI-1-1. IT HAS ALREADY BEEN ELIMINATED BY ANOTHER EQUATION, 

           MPC, RIGID BODY, KINEMATIC COUPLING CONSTRAINT, TIE CONSTRAINT OR 

           EMBEDDED ELEMENT CONSTRAINT. THE REQUIRED MPC (TYPE PIN) CANNOT BE 

           FORMED.