33701205
Inverse dynamics and simulation of a 3-DOF spatial parallel manipulator
Recently the parallel manipulators with less DOF have attracted the researchers, but works on their dynamics are relative few. In this paper, an inverse dynamic formulation is presented by the Newton-Euler approach for a spatial parallel manipulator, which has two translational degrees of freedom and one rotational degree of freedom. The inverse kinematics analysis is firstly performed in closed form. Then the force and moment equilibrium equations for the manipulator are presented. According to the kinematic constraints of the legs and the platform, some joint constraint forces are eliminated and an algorithm to solve the actuator forces is given. In addition, ADAMS is used to perform the kinematic and dynamic simulation for the manipulator. The simulation results are compared to those derived from algebraic formulae and the comparison shows the validity of the mathematical model.
10565448
Singularity analysis of the HALF parallel manipulator with revolute actuators
This paper concerns the singularity of the half parallel manipulator, a novel three degrees of freedom (DOFs) mechanism, with revolute actuators. The parallel manipulator, proposed previously, consists of a base plate, a movable platform, and three connecting legs. It has the advantages in terms of only single-DOF joints and high rotational capability. The parallel manipulator has wide application in the fields of industrial robots, simulators, parallel machine tools and any other manipulating devices that high rotational capability is required. The inverse kinematics problem and Jacobian matrices are recalled firstly. And then all possible singularities of the manipulator are analyzed in detail. The results of the paper are very useful for the apprehension and the application of the manipulator.
7114960
On the optimum design of planar 3-DOF parallel manipulators with respect to the workspace
The design of the robotic mechanisms is one of the most important activities, because these mechanisms determine the performance characteristics of the robots. The paper concerns the issue of computer-aided design (CAD) for planar 3-DOF parallel robotic mechanisms by means of the physical model of the solution space, which can be used systematically to express the relationships between the performance criteria and all link lengths of one type of the robotic mechanism. The performance atlases of the workspace volume for the manipulators are plotted in the physical model of the solution space. The characteristics of the distribution of the workspace shapes in the physical model of the solution space are presented. The results are useful for the optimum design of the robotic mechanisms. The paper proposes a new way for the robotic CAD.
14450831
Some New Parallel Mechanisms Containing the Planar Four-Bar Parallelogram
A parallelogram allows the output link to remain at a fixed orientation with respect to an input link, for which it acts as a unique role in the design of parallel mechanisms. In this paper, the unique role of a parallelogram is used completely to design some new parallel mechanisms with two to six degrees of freedom (DoFs). In these mechanisms, some with three DoFs possess the advantage of very high rotational capability and some with two DoFs have the translational output of a rigid body. More than that, the design concept is also applied first to some parallel mechanisms to improve the systems' rotational capability. The parallel mechanisms proposed in this paper have wide applications in industrial robots, simulators, micromanipulators, parallel kinematics machines, and any other manipulation devices in which high rotational capability and stiffness are needed. Especially, the paper provides new concepts of the design of novel parallel mechanisms and the improvement of rotational capability for such systems.
3096595
Analysis of a novel cylindrical 3-DoF parallel robot
Abstract In this paper, a novel three degrees of freedom (DoFs), that are two degrees of translational freedom and one degree of rotational freedom, parallel robot is proposed. The parallel robot consists of a base plate, a movable platform, and three connecting legs. Because the locus of any point on the moving platform is the subset of a cylinder if z is specified, the robot is called a cylindrical parallel robot. The inverse and forward kinematics problems are described in closed forms. And the velocity equation of the new parallel robot is given. Three kinds of singularities are presented. The workspace for the robot is analyzed systematically, especially, a new index to evaluate the mobility (In this paper, mobility means rotational capability.) of the moving platform of the robot is defined and discussed in detail. The parallel robot has wide application in the fields of industrial robots, simulators, microrobots and parallel machine tools.
790904
A new three-degree-of-freedom parallel manipulator
In this paper, a novel spatial three degree-of-freedom, that are two degrees of translational freedom and one degree of orientational freedom, parallel manipulator is proposed. The parallel manipulator consists of a base plate, a movable platform, and three non-identical connecting legs. The kinematics problems and velocity equation of the new parallel manipulator are given. Three kinds of singularities are presented. The parallel manipulator has wide application in the fields of industrial robots, motion simulators, and parallel kinematics machines.
17545097
Design of Rotary Clock Based Circuits
Rotary clock technique has been shown to reduce the power dissipation of clock distribution by up to 80%. However, to our knowledge, no practical digital synchronous circuit has been designed that utilizes the rotary technique due to the multi-phase nature of rotary clock signals and the strong coupling between a rotary clock network and the circuit it drives. In this paper, we make the first attempt to design rotary based circuit by proposing a unified clock and circuit design methodology. Given a sequential circuit and a clock frequency, our scheme derives a rotary clock network and a functionally equivalent circuit so that they can be integrated to operate reliably at the target frequency. We have applied our scheme to design several rotary clock based DSP modules. Simulation results show that all designs operate correctly with no timing violation. Compared with designs using conventional clock trees, our designs achieve an average clock power saving of more than 70%.
16235665
Real-time 3D fluid simulation on GPU with complex obstacles
In this paper, we solve the 3D fluid dynamics problem in a complex environment by taking advantage of the parallelism and programmability of GPU. In difference from other methods, innovation is made in two aspects. Firstly, more general boundary conditions could be processed on GPU in our method. By the method, we generate the boundary from a 3D scene with solid clipping, making the computation run on GPU despite of the complexity of the whole geometry scene. Then by grouping the voxels into different types according to their positions relative to the obstacles and locating the voxel that determines the value of the current voxel, we modify the values on the boundaries according to the boundary conditions. Secondly, more compact structure in data packing with flat 3D textures is designed at the fragment processing level to enhance parallelism and reduce execution passes. The scalar variables including density and temperature are packed into four channels of texels to accelerate the computation of 3D Navier-Stokes equations (NSEs). The test results prove the efficiency of our method, and as a result, it is feasible to run middle-scale problems of 3D fluid dynamics in an interactive speed for more general environment with complex geometry on PC platform.
16862069
Progressive geometry compression for meshes
A novel progressive geometry compression scheme is presented in this paper. In this scheme, a mesh is represented as a base mesh followed by some groups of vertex split operations using an improved simplification method in which each level of the mesh can be refined into the next level by carrying out a group of vertex split operations in any order. Consequently, the progressive mesh (PM) representation can be effectively encoded by permuting the vertex split operations in each group. Meanwhile, a geometry predictor using the Laplacian operator is designed to predict each new vertex position using its neighbours. The correction is quantized and encoded using a Huffman coding scheme. Experimental results show that our algorithm obtains higher compression ratios than previous work. It is very suitable for the progressive transmission of geometric models over the Internet.
14510898
Evolutionary learning of dynamic probabilistic models with large time lags
In this paper, we explore the automatic explanation of multivariate time series (MTS) through learning dynamic Bayesian networks (DBNs). We have developed an evolutionary algorithm which exploits certain characteristics of MTS in order to generate good networks as quickly as possible. We compare this algorithm to other standard learning algorithms that have traditionally been used for static Bayesian networks but are adapted for DBNs in this paper. These are extensively tested on both synthetic and real-world MTS for various aspects of efficiency and accuracy. By proposing a simple representation scheme, an efficient learning methodology, and several useful heuristics, we have found that the proposed method is more efficient for learning DBNs from MTS with large time lags, especially in time-demanding situations. © 2001 John Wiley & Sons, Inc.
17132126
Recovery of material under complex illumination conditions
To calculate the inter-reflection between real objects and virtual ones in augmented reality, recovery of material for the real objects is necessary. In this paper, an approach is proposed to recover the material properties from a single high dynamic range image for a homogeneous object under complex illumination conditions. By the method, we first acquire a high dynamic range image for the object, and one or a few environment maps in high dynamic range as illumination of the object. Then a simulated annealing algorithm is employed to solve the inverse rendering problem. Finally, we obtain optimal parameter values for the reflection model in approximating the material of the object. In the course of optimization, image-based lighting and ray tracing techniques are used, and as a result the inter-reflection can be calculated in convenience. In addition, the transparent and translucent properties can be also recovered.