Development of a novel 6-DOF hybrid serial-parallel mechanism for pose adjustment of large-volume components

In this paper, a novel 6-degrees-of-freedom (DOF) hybrid mechanism is proposed to realize position and posture adjusting for large-volume equipment. The designed hybrid manipulator is composed of the lower and upper modules, namely, a 3-DOF redundant spatial parallel mechanism (SPM) and a 3-DOF planar parallel mechanism (PPM), which has three rotational and three translational DOFs. According to the step-by-step pose adjusting strategy, the kinematics analyses of the lower and upper modules have been carried out systematically. For the whole hybrid mechanism, a complete kinematic model has been established; and visualized workspace of the kinematic model with regular shape and large volume demonstrates profound application prospects in engineering. In order to evaluate the performance of the proposed mechanism, experimental tests have been conducted in an automated docking system for pose adjustment of large and heavy components. The analysis results demonstrate the effectiveness and practicability of the new mechanism.

Dynamic response analysis for multi-degrees-of-freedom parallel mechanisms with various types of three-dimensional clearance joints

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.

Direct Kinematic Analysis of the Spatial Parallel Mechanism with 3-R(P)S Structure Based on the Point Pair Relationship

This paper demonstrates a novel geometric modeling and computational method of the family of spatial parallel mechanisms with 3-R(P)S structure for direct kinematic analysis based on the point pair relationship. The point pair relationship, which is derived from the framework of conformal geometric algebra (CGA), consists of the relationship between the point and the point pair and two point pairs. The first research is on the distance relationship between the point and the point pair. Secondly, the derivation of the distance relationship between two point pairs is based on the aforementioned result, which shows the mathematical homogeneity. Thirdly, two formulations for a point of the point pairs that satisfy the distance relationship between two point pairs are reduced. Fourthly, the point pair relationship is applied to solve the direct kinematic analysis of the spatial parallel mechanism with 3-R(P)S structure. Finally, four numerical examples are provided to verify the validity of the proposed algorithm. Overall, the proposed method can be generalized for the direct kinematics of a series of spatial parallel mechanisms with 3-R(P)S structure.

300-N Class Convex-Based Telescopic Manipulator and Trial for 3-DOF Parallel Mechanism Robot

We designed a new telescopic manipulator that uses a clustered elastic convex tape. The manipulator has an ultra-wide expansion range and toughness against mechanical stress. Compared to conventional linear actuators, our convex-type manipulators have high extension range and are very lightweight. Moreover, they are compact when rolled up. The telescopic manipulators designed in the previous study had insufficient output due to structural problems and were unstable. In this study, we report a Type-K telescopic manipulator mechanism (Makijaku-Ude Type-K), which is a redesigned manipulator that can be easily used with a 300-N class power, and applied the mechanism to a three degrees-of-freedom spatial parallel-mechanism robot.

Effects of Spherical Clearance Joint on Dynamics of Redundant Driving Spatial Parallel Mechanism

SUMMARY This paper proposes a dynamic modeling method of redundant drive spatial parallel mechanism, dynamics of 4-UPS-RPU redundant driving spatial parallel mechanism considering spherical joint clearance are analyzed. The dynamic equation of spherical joint clearance with Lagrange multiplier is built. The influences of single clearance and multiple clearances on dynamic responses of redundant drive spatial parallel mechanisms are analyzed under different clearance values. The results show that the dynamic characteristics of the mechanism with single clearance are basically consistent with the ideal situation, and the dynamic characteristics of the mechanism with multi-clearance are significantly different from the ideal situation.

A generalized method for three-dimensional dynamic analysis of a full-vehicle model

Dynamic performances of the vehicle are significantly influenced by the suspension mechanisms. An understanding of the effects of the suspension kinematics and statics (or, briefly, kinestatics) is crucial to improve the dynamic performances of a vehicle. However, the suspension kinestatics is often neglected in the dynamic analysis. This paper presents a generalized full-vehicle model for the three-dimensional dynamic analysis, which consists of two pairs of the front and rear spatial suspension mechanisms. Each suspension is represented by a corresponding instantaneous screw joint supporting the vehicle body at any instant. The full-vehicle model is viewed to be a 6-degree-of-freedom spatial parallel mechanism. As the spatial parallel mechanism, the kinematics and statics of the full-vehicle model are analysed using the theory of screws. Taking the suspension kinestatics and tyre dynamics into consideration, the dynamic equations of the full-vehicle model are formulated in terms of the Lagrangian equations. As immediate applications, the dynamic behaviours of a vehicle are simulated and evaluated under two different road disturbances, respectively. By comparing with the simulation results from two other widely used methods, it confirms the validity of the theoretical method.

Jacobian approach to the kinestatic analysis of a full vehicle model with application to cornering motion analysis

The Jacobian approach to the kinestatic analysis of a planar suspension mechanism has been previously presented. In this paper, the theory is extended to three-dimensional kinestatic analysis by developing a full kinematic model and viewing it as a spatial parallel mechanism. The full kinematic model consists of two pairs of the front (double wishbone) and rear (multi-link) suspension mechanisms together with a newly developed ground-wheel contact model. The motion of each wheel of four suspension mechanisms is represented by the corresponding instantaneous screw at any instant. A vehicle is considered to be a 6-degrees-of-freedom spatial parallel mechanism whose vehicle body is supported by four serial kinematic chains. Each kinematic chain consists of a virtual instantaneous screw joint and a kinematic pair representing ground-wheel contact model. The kinestatic equation of the 6-degrees-of-freedom spatial parallel mechanism is derived in terms of the Jacobian. As an important application, a cornering motion of a vehicle is analysed under the assumption of steady-state cornering. A numerical example is presented to illustrate how to determine the optimal locations of strut springs for the least roll angle in cornering motion using the proposed method.