In this paper the decomposition method for kinematic synthesis and analysis is extended to 7-link spatial mechanisms. By the way of examples mathematical models for the general 7R mechanism, and RRRPRRR, RRRRPPRR, RRPRPPR 7-link spatial mechanisms are developed whichi are representative of the 42 types of single-loop 7-link spatial mechanisms. 相似文献
In this paper the decomposition method for kinematic synthesis and analysis is extended to all 5-link, single-loop spatial mechanisms. This is accomplished by solving sets of equations which can be used to describe the mathematical models of all spatial 5-link mechanisms. These sets of equations can be sub-divided into sets of three equations describing the intersection of two planes and a sphere (computer program PREB0), and into sets of pairs of equations describing the intersection of a plane and a sphere (computer program PREB1). By way of examples the mathematic models for RRRSR, RSRRR, RRTTR, RRPSP and RTPPC spatial mechanisms are described, and an RRRSR mechanism used in sewing machines is analyzed. 相似文献
In this paper the decomposition method for kinematic synthesis and analysis is extended to all 6-link, single-loop spatial mechanisms. This is accomplished by solving sets of equations which can be used to describe mathematical models of all 6-link spatial mechanisms. These sets of equations are solved sequentially in an organised way by subdividing the sets of equations into groups of equations which describe the intersection of two planes with a unit radius sphere (computer programme PREB3), and the intersection of a plane and a unit radius sphere (computer programme PREB2). By way of examples mathematical models for RRRTRR, RRPRTR, RTRPRP, RRPPRC spatial mechanisms are described which are representative of the 130 distinct 6-link spatial mechanisms. 相似文献
Velocity fluctuations have been recognized as important in the statics and dynamics of mechanisms [1]. The geometric conditions governing the existence of extreme velocity ratios in a spatial 4-link mechanism having two revolute, one cylindrical and one prismatic pair have been obtained. The present investigation presents an algebriac solution of the velocity fluctuation problem. It is shown that, in the general case, the extreme velocity ratios must be among the real roots of an 8th degree polynomial in gemometric parameters of the mechanism. The extreme velocity ratios of any given mechanism can be obtained from the above results. Numerical example is presented to illustrate the procedure.The results presented in this paper can be extended to synthesize a spatial four link mechanism with prescribed extreme velocity ratios. 相似文献
The generalised 4-link RSSR mechanism is analysed which is kinematically equivalent to the more general 7-link spatial mechanism. and joint arrangements represent, respectively, two and three co-intersecting revolute pairs. 相似文献
The equations for complete shaking force balancing of an open-loop spatial chain consisting of pairs without sliding freedom, a single loop spatial n-bar linkage with R-R link consisting of pairs without sliding freedom, as well as a single loop spatial n-bar linkage with only one P pair are derived in this paper. For a single loop n-bar linkage with R-S link, the equations of complete shaking force balancing are derived also, if the mass center of the R-S link has some constraint. In the examples, the equations of complete shaking force balancing of Bennett, RRRSR, RRPSR and RRSRR linkages are given. 相似文献
In this paper, multi-objective optimization of a rack-and-pinion steering linkage is proposed. This steering linkage is a common mechanism used in small cars with three advantages as it is simple to construct, economical to manufacture, and compact and easy to operate. In the previous works, many researchers tried to minimize a steering error but minimization of a turning radius is somewhat ignored. As a result, a multi-objective optimization problem is assigned to simultaneously minimize a steering error and a turning radius. The design variables are linkage dimensions. The design problem is solved by the hybrid of multi-objective population-based incremental learning and differential evolution with various constraint handling schemes. The new design strategy leads to effective design of rack-and-pinion steering linkages satisfying both steering error and turning radius criteria.
The use of direction cosines and projections is shown to be adequate and efficient for deriving the input-output displacement equations for spatial mechanisms, up to 6-link 5R-C mechanisms. The displacement equations are derived for several 5-link mechanisms and 6-link 4R-P-C mechanisms. These derivations are quick and direct and automatically avoid extraneous roots. The method of derivation for 6-link 5R-C mechanisms is indicated, showing how extraneous roots are avoided by the approach. Part I explains the method, applied to 5-link mechanisms that yield a 4th degree equation. Part II shows the application to 5- and 6-link mechanisms with equations of higher degree. 相似文献
This paper deals with the synthesis of a spatial 4-link mechanism with two kinematic revolute pairs, a spherical pair and a spherical pair with a latch, using the Rosenbrock method of optimization.Several variants are considered according to various rhythms of the tracing of a point on the coupler along the traced curve. The digital data obtained during the synthesis of the mechanism was displayed on the “Mir-2” Electronic Digital Computer. 相似文献
Developing an intelligent robot platform that has multiple motion modes and can actively adjust the motion mode according to an operation situation is necessary in resolving the inability of single-mode robots to adapt completely to complex environments. In this study, we designed a robot that has multiple motion modes and can switch freely in these existing modes. The robot has the following modes: Four-legged walking, two-legged walking, pulse scrolling, and crawler movement. In the robot’s design, these modes are not just simple mechanisms involving superposition and motion switching. These modes involve a degree of freedom in reuse, thereby reducing the number of drives and obtaining a compact structure while achieving a coherent transition of each action mode. For higher load ratios, motion continuity are increased. The robot platform can balance itself during movement by adjusting its own mechanism or providing additional force and change its shape and posture over some obstacles by adjusting its own mechanism.
The traditional formulae for degree of freedom are not valid in solving the platform for certain complex spatial parallel mechanisms. Therefore, by uniformly depicting the kinematic and geometric constraints of a mechanism with a screw theory, we put forward a new method to study the degree of freedom for the platform of spatial parallel mechanisms. This method should solve the analysis and calculation problems of the degree of freedom in many complex spatial parallel mechanisms, which may not always be solved correctly with traditional formulae. 相似文献
Using a parallel mechanism in the wear test simulators of prosthetic knees provides an easy access to the femoral and tibial components during tests. Moreover, because of its higher accuracy and load capacity, in comparison with serial mechanisms, it allows simulation of heavier tasks, such as climbing stairs, to be performed. This paper describes a new 3 Degree of freedom (DoF) spatial 2T1R (T: Translational DoF; R: Rotational DoF) parallel mechanism, for reproducing the force and motion of the tibial component of the knee prostheses in a wear test simulator. Kinematics and dynamics analysis of the mechanism indicated that it can satisfy the required DoFs, workspace and load capacity prescribed in the standard. Also, evaluation of the performance of the mechanism using the simMechanics toolbox of MATLAB revealed that it can reproduce the prescribed forces/torques with relatively high accuracy. However, the mechanism’s force outcomes were found to be affected by inaccuracies in mounting the prosthesis components, although less than the previous serial simulators. In comparison of the different possible architectures, a lateral leg angulation of 45 degrees provided the best efficacy, considering the size of actuators, the overall size of the mechanism and the accessibility of the test sample.