Papers by Author: Yu Zhang

Abstract: The aim of this paper is to test the trajectory precision of the execution terminal of the industrial robot based on a non-contact laser tracing measurement technique. The target is found in terms of tracing mirror attached in measurement position. This method utilizes the linear motion units and photo detection units to trace the target actively. The measurement of the target coordinates are measured with the laser interferometer linear measurement module and the grating ruler. This system can achieve the trajectory measurement of the planar motion objects without contact in real-time condition and also possesses the high precision. The experimental work and calculation were performed in order to achieve the trajectory precision of the research.

Abstract: The purpose of this paper is to study the ability of solder joints to resist thermal fatigue. 2D simplified models of Plastic Ball Grid Array package (PBGA) structures with ten different solder joints obtained from surface mount experiment are established by finite element software, then stress-strain response of solder joints subjected to the thermal cycle load are calculated. And the effects of shape parameters of solder joints on the ability to resist thermal fatigue are discussed. Results indicate that for the same material and volume solders, the solder joints which have higher height, smaller diameter and contact angle have a stronger ability against thermal fatigue, and that the thermal fatigue characteristics are also greatly influenced by the solder outlines. Comparing with SP solder joints, LF solder joints have stronger ability against thermal fatigue.

Abstract: A novel time-variant reliability model is developed after studying the traditional dynamic performance of mechanism. The expression of reliability is given based on stochastic process. A two-dimensional description of the error generating process is established by studying mechanism output kinematic accuracy. The reliability of mechanism output kinematic accuracy can be obtained according to this description. The model proposed can be used to calculate the reliability of mechanism directly, if the distribution of mechanism output kinematic accuracy is known.

Abstract: The characteristic of Instant Customerization (IC) and its job-shop scheduling problem is described. The customer requirements were divided into static forecasting and dynamic forecasting aiming at IC, that is common requirement forecasting and individualized requirement forecasting. According to the characteristics of the problem, the job shop scheduling part of the system is then programmed with an algorithm, PSO. Simulation results showed that requirement forecasting can provide an excellent delivery date to adapt to the IC job-shop problem.

Abstract: Although some research and commercial software for NC simulation is available, NC simulation modeling is still not matured. Most of them are based on G&M code. STEP-NC is a new data model for computer numerical control (CNC). It provides rich information for CNC machine tools, i.e. “what to do” based on features rather than “how to do” as for G-code. IDEF0 is a method designed to model the decisions, actions, and activities of an organization or system. It helps to organize and analyze a system and to promote a good communications between the analyst and the customer. So in this paper, from the view of system modeling, function modeling of NC simulation system based on STEP-NC is built by IDEF0 method. As a result, NC simulation system can be realized more efficiently.

Abstract: The measuring precision of error separation technology is directly related to error separation parameters selection. If the parameter selection rules aren’t followed correctly, the accuracy of error separation will be affected badly, and even the error figure got will be a distortion result. Through a discussion on the characters of error separation technology, eight rules for choosing error separation parameters of multi-probe method are made in this paper. These rules are regarded as the general laws to follow when measuring the geometrical error by multi-probe method. Based on the results of the online measurement experiment, the parameter selection rules are proved to be effective.

Abstract: There are some applications of error separation technique in actual measurement. However there exists a series of theoretical and technical obstacles, and the error separation technique lacks the objective assessment. The further discussion about the character of error separation technique by multi-probe method is made in this paper and six criteria for precision measurement of error separation technique by multi-probe method is also advanced. That is, (1) The criterion for veracity of error separation; (2) The criterion for periodicity of combination signal; (3) The criterion for the remnant first-harmonic in combination signal; (4) The criterion for validity of error separation results; (5) The criterion for validity of probes’ fixing angles ; (6) The criterion for nonzero character of weight function. These criteria are significant for the objective evaluation of the measuring apparatus’ measurement precision, the validity of the sampling data, and the confidence level of error separation results. The validity of the measuring condition was proved by the online measurement experiment.

Abstract: According to the definitions of the CIRP Unification Document, The locus equations of the rotating center and the average rotating center are deduced, and then, the parameter equations of the rotating axis and the average rotating axis are obtained. All of above verify the definition of the rotating axis of the CIRP Unification Document in theory, and it is also proved clearly that the rotating axis and the average rotating axis are sole.