Key Engineering Materials Vols. 579-580

Abstract: This paper describes the reconstruction process of a 3P2R type combined robot platform on the basis of a 2-axis linearly moving worktable. An additive 3-DOF manipulator installed above the worktable has one prismatic and two revolute joints by using a novel integrated ball screw and spline axis. The control system of the platform is composed of a 4-axis motion control card and a PLC. Meanwhile, this paper deduces the kinematic equations of this special combined platform for measurement. The 3P2R type platform could be used to measure 3D contour of small work piece automatically.

Abstract: The drive system with linear motor of precision machine tools can generate a lot of heat and part of it is conducted to machine tools structures. Therefore, it can lead to the thermal deformation of the structures and hence seriously influences the processing accuracy. In this paper, the finite element model (FEM) considering convection of the planes, the pipelines of the cooler system and thermal resistance is adopted to investigate the thermal distribution and thermal deformation of the carriage system of precision machine tools driven by linear motor. In addition, position-independent thermal errors models of the carriage system are proposed for the main heat source, the primary part of the linear motor, of the carriage system travels with the worktable; the feature genetic algorithm is used to procure the thermal key points of the carriage due to the great number of candidate points. At last, the experiment is conducted on the Y-axis carriage system of precision three-axis machine tool, which demonstrates the two geometric errors δ_x and ε_z caused by the thermal deformation are significantly tiny. The mathematical models of three thermal errors are obtained through the temperatures of the key thermal points because the interferometer cannot measure the roll error ε_y. Also, the comparison between the measurements and the thermal errors models indicates that the position-independent thermal models are capable of satisfactorily predicting the magnitude of the other three geometric errors of the carriage system caused by the thermal deformation and also being used in further study of compensation system.

Abstract: Reverse engineering has become an independent research area in CAD/CAM system with the development of modern manufacturing. The 3D reconstruction technology of generating a digit model from physical model is an important part of reverse engineering. The 3D reconstruction technology based on stereo vision has advantages such as non-contact measurement, simple system structure, being fast and efficient. In this paper, a fast 3D reconstruction technology based on stereo vision is presented. Firstly, BP neural network is used to simulate the mapping relationship between the 3D object and its images. Then, the epipole positions and adjusting coefficients for epipolar lines are calculated according to the epipolar line constraint. After the rectification transformations on the left and right image planes is conducted, the pairs of conjugate epipolar lines become collinear and parallel to the horizontal image axis. Therefore, when the stereo correspondences between the left and right images are being performed, the search is done only along the horizontal lines of the rectified images, which is highly advantageous to fast image matching for stereo vision and 3D reconstruction of free-form surface.

Abstract: t presents the parallel mechanism and variable acceleration control method, which is composed of slider, connecting rod, moving platform and linear guide etc. The motion platform is supported by three connecting rods through hinging, the other end of the connecting rods are respectively hinged with two sliders. Among them two pairs of connecting rod, two sliders and the moving platform formed a symmetric structure that is the so called Parallel Mechanism. The third connecting rod is parallel to one of two connecting rods, so that the two parallel connecting rods, slide block and the moving platform formed a parallelogram structure, it makes that the moving platform is always parallel to liner guiderail in the process of movement. By controlling the two sliders moving in the way of variable acceleration, it can make the trajectory curve, speed curve and acceleration curve of the moving platform are continuous, smooth, so impact and vibration of the moving platform is limited in the operation process.

Abstract: Since traditional pose estimation methods with the features of points, lines and so on might not be applied directly to round-shape workpieces, a new pose estimation method for round-shape workpieces genetic algorithm based was proposed. Compared with previous studies, this method needs no auxiliary information, such as points, lines, concentric circles and so on. Firstly, transformation model of perspective projection of round-shape workpiece was created, and the round-shape workpiece was characterized by analytic equation. Secondly, via detecting the contour and extracting its feature of workpiece, a feature error function was established with respect to the pose angles, which was a multi-objective nonlinear function. Finally, the error function was solved by an improved genetic algorithm and the pose estimation of round-shape workpiece was achieved. The result of related experiments showed that the method had high accuracy, and to some extent inhibited the effects of noise.

Abstract: As for the shortcomings of poor rigidity and strength of weak of thin-walled tube parts, a device of an adaptive PID controller which based on neural network has been proposed by regarding the thin-walled tube fixture system as the research object. The controller which integrates the characteristics of neural network and PID regulator can realize the self-tuning of PID parameters effectively and make the control system equip with the feature of fast response, small overshoot and strong robustness etc. Simulation results show that the controller can meet the system requirements commendably and it can implement the automatic chucking control of the thin-walled steel cutting process with fast and non-destructive in the experimental prototype.

Abstract: Odometry is a relative position measuring method widely used in robot position estimation. However, the error accumulates in an unbounded fashion. In this paper, a new model based on castors is proposed. The final pose accuracy is only affected by the position of castors according to the new model. Experiment is also conducted to demonstrate the feasibility and high accuracy of the new method.

Abstract: The 32-bit ARM Cortex-M3 core processor Stm32f107vc which integrates two sets of bxCAN interfaces is used as hardware platform to achieve the design of hardware module and software module in this paper. Firstly, real-time multi-tasking operating system μCOS-II is ported to stm32 processor, then open source protocol stack microCANopen which is high real-time and reliable is transplanted under the μCOS-II, so a design of CANopen slave station is achieved. The CAN analyzer which is equipped with monitor trace functionality is used as CANopen master station to start the network, with three CANopen slave stations and one HMI, a distributed multi-axis motion control system based on CANopen which achieves network management and synchronous transmission of data in distributed control system is designed. On above basis, Fuji ALPHA5 Smart servo is used as executive member, modular design of reconfigurable motion control algorithm is realized, furthermore, The flexible module configuration enables the designer to develop systems conveniently according to the change of control requirement and network topology. This distributed control system not only has good real-time performance and stability, but also can reduce the complexity, enhance the flexibility of control system and save cost.

Abstract: An integrated design method of the compliant linear positioning device (CLPD) was researched, which was composed of a compliant guide mechanism and two electromagnetic actuators. Typically, the actuators are designed after the compliant mechanism, which may make it more complex to improve the performances of the CLPD. With the utilization of the multi-physics co-simulation technology, established a parametric multi-physics finite element model (MFEM) of the CLPD including the compliant linear guide mechanism and the electromagnetic actuators simultaneously in the COMSOL environment. Proposed the constraints of the dominant parameters, based on the analysis of their influence on the characteristics of the CLPD. Then an integrated optimizing design strategy of the CLPD was put forward. According to the strategy, a two degree of freedom long-range linear compliant mechanism and its matching actuators were designed. The experimental results showed the performance of the designed CLPD, which validated the design strategy.

Abstract: Aiming at additional load consisted in jumping performance testing of actuator at present, the paper designed a testing system of mechanical speed jumping performance, and made compensation calculation by shortening the corresponding time of reach a certain speed point. At last, the compensation method was verify that correct and feasible by simulation experiments.