Hang Wang

Dynamic force analysis of n.-d.f. multiloop complex spatial mechanisms

Abstract This paper presents the dynamic force analysis of the multiloop complex spatial mechanism with n .-d.f.. An equivalent hypothetical mechanism is used to analyze and solve the six-dimensional inertia forces at first, and further to get all input torques including the hypothetical inputs. A concept of local equivalent moments is introduced. Using the local equivalent moments and the first-order kinematic influence coefficients, the crucial constraint forces of the end pair of each branch connected to the centric polygon are obtained. Thereby the total mechanism can be solved. Because all the calculations contain only the multiplications and/or reversion of six or three-order matrices, the tedious calculations of more than a hundred simultaneous equations are avoided. A numerical example, a 4-d.f. six-branch mechanism, is given at the end of this paper.

Kinematic influence coefficient method of kinematic and dynamic analysis

Abstract The kinematic influence coefficient method is extended to kinematic and dynamic force analysis in one-DOF single-loop spatial mechanism in this paper. The formulas of velocities and accelerations are deduced. A concept of local equivalent force and moment is presented. On the concept, the constraint reactions acting on the kinematic pair, which is connected with frame and end link, are obtained. These formulas are simply explicit expressions and are suited for all one-DOF single-loop spatial mechanisms which include that an input link is any link. The 7 R seven-link spatial mechanism with three parallel axes is analyzed in a numerical example.

Isotropic Design of Stewart Platform-Based Force Sensor

The modified isotropy indices of Stewart platform-based force sensor are proposed by introducing the orthogonality condition, the physical meanings of the modified isotropy indices, the orthogonality condition and the concept of full isotropy are given. The isotropy performance of the general 6-6 Stewart platform-based force sensor is studied in detail based on the modified isotropy indices, the result indicates that it is impossible to realize full isotropy in theory, and the best comprehensive isotropy performance is obtained by compromising the isotropy indices. A novel 6/3-3 Stewart platform-based force sensor which can achieve full isotropy is proposed and a numeric example is given. The research results are useful for structure design of the six-axis force sensor.

Configuration and isotropy study of a novel fully pre-stressed and double-layer six-component force/torque sensor

A novel fully pre-stressed six-component force/torque sensor based on double-layer Stewart platform is proposed, and the parameter optimization of the sensor structure with genetic algorithms (GA) is presented. The structure characteristic of the fully pre-stressed sensor is analyzed in comparison with the traditional Stewart platform-based sensor. The number of the elastic limbs is determined by using Carathodorys theorem and Steinitzs theorem in convex analysis. In order to achieve the best performance, the static mathematical model is built by using screw theory, and the isotropy indices of the sensor are studied systematically. By compromising all the isotropy indices, the optimal design of the sensor structure is performed based on genetic algorithms, and the best comprehensive index of Stewart platform-based force sensor is obtained. The research results of the paper are useful for the design and further research of the six-component force/torque sensor.

Task-oriented design of a fully pre-stressed double-layer six-component force/torque sensor

This paper presents a method to study and design a fully pre-stressed double-layer six-component force/torque sensor. The structure characteristic of the fully pre-stressed sensor is analyzed. In order to achieve the best performance, the static mathematical model is built by using screw theory. Based on the task ellipsoid, the task model of the pre-stressed force sensor is built. The relationship between the sensor and the task is studied systematically. And the mathematic description of task-oriented performance evaluation of the fully pre-stressed sensor is proposed. The key parameters of the fully pre-stressed force sensor satisfying the purpose of the task are obtained. The research results of this paper are useful for the further research and practical application of the six-component force sensor.