The impact dynamics of a flexible multibody system is investigated.By using a partition method,the system is divided into two parts,the local impact region and the region away from the impact.The two parts are connected by specific boundary conditions,and the system after partition is equivalent to the original system.According to the rigid-flexible coupling dynamic theory of multibody system,system’s rigid-flexible coupling dynamic equations without impact are derived.A local impulse method for establishing the initial impact conditions is proposed.It satisfies the compatibility conditions for contact constraints and the actual physical situation of the impact process of flexible bodies.Based on the contact constraint method,system’s impact dynamic equations are derived in a diferential-algebraic form.The contact/separation criterion and the algorithm are given.An impact dynamic simulation is given.The results show that system’s dynamic behaviors including the energy,the deformations,the displacements,and the impact force during the impact process change dramatically.The impact makes great efects on the global dynamics of the system during and after impact.
The dynamics for multi-link spatial flexible manipulator arms is investigated.The system considered here is an N-flexible-link manipulator driven by N DC-motors through N revolute flexiblejoints.The flexibility of each flexible joint is modeled as a linearly elastic torsional spring,and the mass of the joint is also considered.For the flexibility of the link,all of the stretching deformation,bending deformation and the torsional deformation are included.The complete governing equations of motion of the system are derived via the Lagrange equations.The nonlinear description of the deformation field of the flexible link is adopted in the dynamic modeling,and thus the dynamic stiffening effects are captured.Based on this model,a general-purpose software package for dynamic simulation of multi-link spatial flexible manipulator arms is developed.Several illustrative examples are given to validate the algorithm presented in this paper and to indicate that not only dynamic stiffening effects but also the flexibility of the structure has significant influence on the dynamic performance of the manipulator.
The dynamics for multi-link spatial flexible manipulator arms consisting of n links and n rotary joints is investigated. Kinematics of both rotary-joint motion and link deformation is described by 4 × 4 homogenous transformation matrices, and the Lagrangian equations are used to derive the governing equations of motion of the system. In the modeling the recursive strategy for kinematics is adopted to improve the computational eflciency. Both the bending and torsional flexibility of the link are taken into account. Based on the present method a general-purpose software package for dynamic simulation is developed. Dynamic simulation of a spatial flexible manipulator arm is given as an example to validate the algorithm.
