| Summary: | ObjectiveHybrid robots that combine the advantages of serial/parallel robots have become one of the important research directions in the field of robots. The establishment of the Jacobian matrix is the key to the combination of theoretical research and engineering application in robot theory. However, when using the robot base coordinate system as the reference, the velocity Jacobian matrix obtained by applying the screw theory cannot directly obtain the velocity of the end effector point, and the force Jacobian obtained cannot be directly used to conduct static analysis based on the force received by the end effector. To solve this problem, a new method for establishing the Jacobian matrix of "parallel + serial" hybrid robots based on the end effector screw description coordinate system is proposed.MethodsFirst, based on the screw theory, the concept of end-effector screw describing coordinate systems is described, and the advantages of applying screw theory for velocity and static force modeling in this coordinate system are analyzed. Secondly, a general approach for establishing the velocity and force Jacobian matrix of the“parallel + serial” hybrid robot is proposed utilizing the end-effector screw describing coordinate and applying screw theory. Then, taking the typical domestic "parallel+serie" hybrid robot TriMule as an example, by employing the end-effector screw describing coordinate, and based on the screw reciprocal product theory, a theoretical derivation model for its velocity and force Jacobian matrix was established. and compared with the traditional methods to verify the correctness of the theoretical derivation model.ResultsThe Jacobian matrix of the "parallel + serial" hybrid robot established based on the end-effector screw description coordinate system can directly obtain the mapping from the joint drive speed to the end operation point speed, and the transposed matrix can directly obtain the force Jacobian matrix. Compared with the traditional method, the proposed new method has more obvious physical meaning, and is more convenient for real-time speed calculation and static analysis.
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