Abstract
For spatial multibody systems, the dynamic equations of multibody systems with compound clearance joints have a high level of nonlinearity. The coupling between different types of clearance joints may lead to abundant dynamic behavior. At present, the dynamic response analysis of the spatial parallel mechanism considering the three-dimensional (3D) compound clearance joint has not been reported. This work proposes a modeling method to investigate the influence of the 3D compound clearance joint on the dynamics characteristics of the spatial parallel mechanism. For this purpose, 3D kinematic models of spherical clearance joint and revolute joint with radial and axial clearances are derived. Contact force is described as normal contact and tangential friction and later introduced into the nonlinear dynamics model, which is established by the Lagrange multiplier technique and Jacobian of constraint matrix. The influences of compound clearance joint and initial misalignment of bearing axes on the system are analyzed. Furthermore, validation of dynamics model is evaluated by ADAMS and Newton–Euler method. This work provides an essential theoretical basis for studying the influences of 3D clearance joints on dynamic responses and nonlinear behavior of parallel mechanisms.
Highlights
Robots are becoming an indispensable part of modern industry and are playing an increasingly important role.[1,2] For some reasons, such as manufacturing tolerance, assembling errors, and wear phenomenon of the kinematic joints, clearance always exists in kinematics joints, and the performance of the robot is unsatisfactory.[3,4,5] Planarization of spatial clearance joints has limitations in studying the dynamics behavior for mechanical systems because the complex motion mechanism of spatial clearance joints is neglected
Nonlinear dynamics model of the parallel mechanism with 3D revolute clearance joint and spherical clearance joint is presented in the third section
Dynamics equation for 4-UPS/RPS parallel mechanism with both 3D revolute clearance joint and 3D spherical clearance joint utilizing Baumgarte stabilization method can be written in matrix form as where M is a 66 Â 66diagonal matrix, representing system mass matrix
Summary
Robots are becoming an indispensable part of modern industry and are playing an increasingly important role.[1,2] For some reasons, such as manufacturing tolerance, assembling errors, and wear phenomenon of the kinematic joints, clearance always exists in kinematics joints, and the performance of the robot is unsatisfactory.[3,4,5] Planarization of spatial clearance joints has limitations in studying the dynamics behavior for mechanical systems because the complex motion mechanism of spatial clearance joints is neglected. Ambrosio and Pombo[14] and Marques et al.[15] improved pre-existing dynamic modeling methods of the mechanisms containing clearance joint, respectively. A dynamics modeling method of parallel mechanism considering 3D compound clearance joint is given. The influence of the compound clearance joint on the dynamic response of the spatial parallel mechanism is discussed. The purposes of the article are to analyze the influences of 3D compound clearance joint on dynamics responses of parallel mechanisms. Nonlinear dynamics model of the parallel mechanism with 3D revolute clearance joint and spherical clearance joint is presented in the third section. Influences of compound clearance joint and axis misalignment on system response are explored, and dynamics model is verified by ADAMS and Newton–Euler method, respectively. Radii of ball and socket can be written as Rbj and Rsi
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