Jing-Shan Zhao

Synthesis of Rectilinear Motion Generating Spatial Mechanism With Application to Automotive Suspension

This paper proposes a synthesis method for rectilinear motion generating spatial mechanism with application to automotive suspension. First, it presents a generic process to synthesize the kinematic chains of a mechanism with the prescribed mobility, and then it deduces the construction criteria of feasible kinematic chains for such a mechanism. The most outstanding advantages of the rectilinear motion generating spatial mechanism used as the independent automotive suspension are that the orientation and position parameters such as kingpin, caster, camber, axis distance, and wheel track are always maintained constant during jounce and rebound. These ideal characteristics are guaranteed by the particular rigid guidance mechanism whose end effector only has one translation along an exact straight line.

The free mobility of a parallel manipulator

Singularities of a manipulator have been addressed repeatedly. However, the singularities and the degree(s) of freedom, as a matter of fact, are two different aspects of the mobility of a manipulator. Consequently, this paper dedicates to discussing the mobility properties through mobility space, which synchronously define the type, number and direction characteristics of the independent motions that the manipulator should execute. The mobility space of a manipulator can be obtained with reciprocal screws of the manipulator via singular value decomposition, which instantaneously depicts the singularity and mobility problems of the manipulators. Application example demonstrates that this methodology can investigate the all-sided mobility properties of parallel manipulators.

Synthesis of a Rear Wheel Suspension Mechanism With Pure Rectilinear Motion

This paper focuses on the synthesis of an independent suspension that can guide the wheel to track a straight line when moving up (jounce) and down (rebound). With displacement subgroups, it first synthesizes a rigid body guidance mechanism and verifies the result through screw theory. To simplify and optimize the loads of each kinematic chain of the knuckle, it investigates the static equations and ultimately synthesizes a symmetric redundant-constraint suspension structure, which could not only eliminate the shambling shocks induced by the jumping of wheels but also decrease the abrasion of tires. Theoretically, only one pair of noncoplanar kinematic chains is necessary to realize straight line guidance. However, a second pair of noncoplanar kinematic chains is particularly utilized to improve the load status of the links. Because of the redundant constraints induced by the suspension structures, the whole weight can be significantly reduced compared with the initial one. ADAMS simulations with a set of real parameters indicate that the rear suspension mechanism proposed in this paper can guide the wheel to follow a rectilinear locus during jounce and rebound. Therefore, this kind of independent suspension can improve the ride and handling properties of advanced vehicles.

Design of an Ackermann type steering mechanism

This article focuses on the synthesis of a steering mechanism that exactly meets the requirements of Ackermann steering geometry. It starts from reviewing of the four-bar linkage, then discusses the number of points that a common four-bar linkage could precisely trace at most. After pointing out the limits of a four-bar steering mechanism, this article investigates the turning geometry for steering wheels and proposes a steering mechanism with incomplete noncircular gears for vehicle by transforming the Ackermann criteria into the mechanism synthesis. The pitch curves, addendum curves, dedendum curves, tooth profiles and transition curves of the noncircular gears are formulated and designed. Kinematic simulations are executed to demonstrate the target of design.

The concept design and dynamics analysis of a novel vehicle suspension mechanism with invariable orientation parameters

This paper starts with a classical mechanism synthesis problem and focuses on the concept design and dynamics analysis of an independent suspension that has invariable orientation parameters when the wheel moves up (jounces) and down (rebounds). The paper first proposes a symmetric redundant constraint suspension structure that has invariable orientation parameters. And then, it analyses the mechanism mobility with the reciprocal screw theory, after which it establishes the displacement constraint equations of the suspension. This type of suspension has all the advantages of the sliding pillar suspension but overcomes its disadvantage of over-wearing. Through differentiating the constraint equations with respect to time, it obtains the kinematics relationship and builds up the dynamics equations of the suspension via Newton–Euler method. Numerical simulations indicate that this kind of independent suspensions should not only eliminate the shambling shocks induced by the jumping of wheels but also decrease the abrasion of the wheels. Therefore, this kind of independent suspensions can obviously improve the ride and handling properties of advanced automobiles.

Research on an intelligent manufacturing system based on an information-localizing machining mode

Abstract To raise the response speed of manufacturing enterprises to the dynamic change of market, this paper presents a new machining mode of information-localization and an intelligent manufacturing system based on that mode. Feasible solutions to the key problems involved in this mode and system, such as the acquirement of workpiece contour information, fast calculation of workpiece state, and adaptive machining control based on the actual state information of the workpiece, etc. are given. Experimental verification has been carried out. The theoretical analysis and experimental results show that the proposed method is feasible. It provides a new effective approach to the fast-response manufacturing of complex parts with small lot size.

The singularity study of spatial hybrid mechanisms based on screw theory

In this paper, a novel methodology based on screw theory to study the singularity of spatial hybrid mechanisms is presented. According to the physical meaning of inverse screws, we introduce the equivalent kinematic screws to replace the function of those of the parallel limbs, and therefore the hybrid branch can be transformed into a pure series kinematic chain which can facilitate the whole analytical process of the singularity of complex spatial hybrid mechanisms. In fact, this methodology can be widely used to solve the singularity problems of spatial hybrid mechanisms based on the analysis of their kinematic characters.

Singularity loci research on high-speed travelling type of double four-rod spatial parallel mechanism

Abstract Based on the author’s research results on high-speed travelling type of double four-rod spatial parallel mechanism in new type virtual axis machine tools with combined architecture, this paper lays emphasis on the problems of singularity analysis and singularity loci calculation of such mechanism. In theory, it has found out three kinds of singularity loci of the mechanism by utilizing an identification matrix that is constructed on the conception of screw, and revealed the relationship between the structural parameter b and the singularity loci, thus laid a theoretical foundation for optimizing the parameter of the mechanism. In aspect of application, by applying the result in the design of new five-coordinate virtual axis machine tool with combined architecture, it has effectively solved the affection of singularity, greatly increased the working space of the machine tool and achieved good effect.

Planar Deployable Linkage and Its Application in Overconstrained Lift Mechanism

This paper investigates the application of a planar deployable structure with screw theory and discusses its possible applications in overconstrained lift platforms via calculating its stiffness. These platforms are all made up of a number of identical scissor-form pivoted links. Compared with their traditional counterparts, the lift platforms with planar deployable structures have higher stiffness and higher strength in applications because every lift platform is multiplane overconstrained mechanism connected by a strengthened frame at each deployable layer. In operation, these deployable structures are always symmetric about the vertical central axis connecting the moving platform and the fixed one. Therefore, the stress conditions of the links in each layer can be assumed to be identical as the lift platform is moving up and down. Prototype test illustrates the innovation of the lift mechanisms while keeping the same load capacity.

Free Motion of the End Effector of a Robot Mechanism

Terminal constraints of robot end effectors from kinematic chains and the free motions under these constraints are discussed. The analytical theory of constraint space of the end effector of parallel robotic mechanism is studied according to the terminal constraint space of its kinematic chains. The degree of freedom of the end effector of a parallel robot should have the three attributes, namely, quantity, type, and direction. The degree of freedom of robot end effector is one of the core issues in the free motion analysis of mechanisms. Therefore, this chapter establishes analytical theory for the constrained space of the end effectors. On this basis, the equivalent description of the complex kinematic chain is discussed, which provides a theoretical support for the equivalent description of the complex kinematic chains to pure serial kinematic chains and lays a foundation for the study of actuation of the prescribed end effector.