Juan Hao

Kinematic constraint analysis in a twin-robot system for curved-surface nondestructive testing

Purpose – Nondestructive testing based on cooperative twin-robot technology is a significant issue for curved-surface inspection. To achieve this purpose, this paper aims to present a kinematic constraint relation method relative to two cooperative robots. Design/methodology/approach – The transformation relation of the twin-robot base frame can be determined by driving the two robots for a series of handclasp operations on three points that are noncollinear in space. The transformation relation is used to solve the cooperative motion problem of the twin-robot system. Cooperative motions are divided into coupled and combined synchronous motions on the basis of the testing tasks. The position and orientation constraints for the two motion modes are also explored. Findings – Representative experiments between two industrial robots are conducted to validate the theoretical developments in kinematic constraint analysis. Artificial defects are clearly visible in the C-scan results, thereby verifying the validi...

The Relationship between Minimum Zone Sphere and Minimum Circumscribed Sphere and Maximum Inscribed Sphere

Among the four methods (minimum zone sphere, minimum circumscribed sphere, maximum inscribed sphere, and least square sphere), only the minimum zone sphere complies with ANSI and ISO standards and has the minimum sphericity error value. Evaluation of sphericity error is formulated as a non-differentiable unconstrained optimization problem and hard to handle. The minimum circumscribed sphere and the maximum inscribed sphere are all easily solved by iterative comparisons, so the relationship between the minimum zone sphere and the minimum circumscribed sphere, the maximum inscribed sphere is proposed to solve efficiently the minimum zone problem. The relationship is implemented and validated with the data available in the literature.

AN ULTRASONIC MODEL FOR REVEALING ELECTRONIC PACKAGE’S INNER STRUCTURE USING ACOUSTIC IMPEDANCE

The reflected ultrasonic echo’s amplitude is relative to the sample material’s acoustic impedance change. So the distribution of acoustic impedance is correlated with the inner structure. In this paper, an ultrasonic model is suggested to reveal electronic package’s inner structure using acoustic impedance. The model first reconstructs the impedance profile of layered medium through an incidence point, then gets other position’s impedance by moving the transducer regularly. Finally, the inner structure of the package can be revealed by the 3D image formed with the impedance matrix.

Magnetic field analysis and optimal design of magnetic bearing

Magnetic field distribution of a radial magnetic bearing with sixteen-pole was analyzed by using finite element method. It was verified by magnetic field measurement. Magnetic bearing structure was optimized based on finite element analysis (FEA) and magnetic circuit method. Optimization was done in object of maximum magnetic force. Two optimizations had similar results. Analysis showed that FEA-based optimization is more accurate and efficient, which had been performed with FEA software-ANSYS 10.0.

Sphericity Evaluation Based on Minimum Circumscribed Sphere Method

The search of sphericity evaluation is a time-consuming work. The minimum circumscribed sphere (MCS) is suitable for the sphere with the maximum material condition. An algorithm of sphericity evaluation based on the MCS is introduced. The MCS of a measured data point set is determined by a small number of critical data points according to geometric criteria. The vertices of the convex hull are the candidates of these critical data points. Two theorems are developed to solve the sphericity evaluation problems. The validated results show that the proposed strategy offers an effective way to identify the critical data points at the early stage of computation and gives an efficient approach to solve the sphericity problems.

Ultrasonic detection technology based on joint robot on composite component with complex surface

Some components have complex surface, such as the airplane wing and the shell of a pressure vessel etc. The quality of these components determines the reliability and safety of related equipment. Ultrasonic nondestructive detection is one of the main methods used for testing material defects at present. In order to improve the testing precision, the acoustic axis of the ultrasonic transducer should be consistent with the normal direction of the measured points. When we use joint robots, automatic ultrasonic scan along the component surface normal direction can be realized by motion trajectory planning and coordinate transformation etc. In order to express the defects accurately and truly, the robot position and the signal of the ultrasonic transducer should be synchronized.

Kinematic analysis and simulation of ultrasonic testing manipulator

Ultrasonic testing for these workpieces with complex shapes is still a challenge in NDT filed. In order to address this problem, this paper provide an effective solution for curved surface scanning using Staubli TX90XL manipulator with six freedom degrees. Here an arm-wrist separateness method is adopted to solve the inverse of manipulator and a shortest distance rule is used to optimize the inverse solutions. Furthermore, we have developed a 3D application software to simulate the ultrasonic trajectory planning for complex shape specimens. Finally, the validity of this scanning method is verified by the C-scan results of the specimen with a curved surface.

A Linear Algorithm of Spatial Straightness for Five Points

It is a non-linear problem to evaluate the minimum zone spatial (3-D) straightness. Because of the disadvantages of evaluating spatial straightness error with traditional method, such as difficulty in solving the non-linear equation, the evaluating precision is lower. This paper develops a solution that can transform the non-linear problem into a linear problem. The solution can obtain more exact results than traditional method using results of LSC as initial conditions. This methodology can also be applied to the problems of computing the minimum circumscribed cylinder and the maximum inscribed cylinder. The effectiveness and efficiency of the novel approach are illustrated by two examples.

A Special Solution of Spatial Straightness for Four Datapoints

Assessment of spatial straightness error is one of the most difficult tasks in form error evaluation, especially when the minimum zone three-dimensional (3D) straightness is decided by four datapoints. This paper develops a solution that can transform the non-linear system into a linear system. To solve the linear indeterminate system of equations, a method of factor fixed is proposed. Given adequate initial conditions, this solution will be the exact solution. The effectiveness and efficiency of the novel approach are illustrated by two examples.

A quick algorithm for circularity error evaluation based on minimum circumscribed circle method

The evaluation of circularity based on the minimum circumscribed circle method is an important method suitable for the circle with the maximum material condition of a convex like a shaft. The minimum circumscribed circle is determined by a small number data points according to the criteria of the minimum circumscribed circle. This article points out the minimum circumscribed circle can be obtained only at vertices of convex hull. Based on three theorems developed, a strategy is proposed to identify the critical data points. The validated results show that the method gives an efficient approach to solve the circularity problems on the minimum circumscribed circle, especially when the number of data points is large.