Yanjie Liu

A Method of Energy-Optimal Trajectory Planning for Palletizing Robot

In this work, the energy-optimal trajectory planning and initial pick point searching problem for palletizing robot with high load capacity and high speed are studied, in which the pick point and place point of the robot are fixed to a desired location for each single task. These optimization problems have been transformed to ternary functional extremum problem and parameters optimal selection problem in which the performance index of the problems the rigid-flexible coupling dynamics model of the robot, and the constraint and boundary conditions of the robot are given. The fourth-order Runge-Kutta method, multiple shooting method, and traversing method are used to solve these specific mathematical problems. The effectiveness of the trajectory planning method is validated by the experimental and simulating results; thus the research work done here provides important support for subsequent palletizing robot research.

Time-Optimal Trajectory Generation of a Fast-Motion Planar Parallel Manipulator

This paper proposes time-optimal trajectory generation method for industrial robots. The proposed time-optimal trajectory generation method studies the relationship between the maximum acceleration and the maximum velocity, and presents an algorithm for deriving the optimal trajectory based on this relationship. In order to verify this method, a new planar parallel robotic manipulator with fast motion and high precision is designed. Finally, the proposed method is applied to the designed robot, and the simulation results prove that the method is effective for the industrial robot

Design and simulation of a macro-micro dual-drive high acceleration precision XY-stage for IC bonding technology

A macro-micro dual-drive high acceleration precision XY-stage is presented in this paper. Combining macro with micro actuator, a system of large workspace and high acceleration with high resolution of motion is developed. Two linear voice coil motors (VCM) are used into the macro motion, and two PZT-driven micro stages of high frequency are mounted on each motor to compensate the position error. A novel elastic decoupling mechanism is used in the stage to avoid the moving gap. The high resolution linear encoder is integrated into the closed-loop feedback, which is used to measure the position of the output end of macro stage and micro stage. By using the mechanical dynamic simulation and FEA method, the decoupling mechanism and the micro mechanism are optimized, and the dynamic characteristics of the high acceleration stage are investigated, which is based on the rigid-flexible dynamic analysis of mechanical system. The simulation results show that this new configuration allows a workspace of 25/spl times/25mm/sup 2/ and an acceleration exceeding 100m/s/sup 2/ with a resolution of motion better than 10nm. The significantly improved performance of the XY-stage can meet the requirement of the rapid development of IC bonding technology.

A novel 2-DOF planar parallel robot with high accelerate / high precision

Orient to urgently demand for high speed and high precision robot of advanced manufacture fields such as packaging and assembly of micro-electronic manufactures, a novel 2-DOF planar parallel robot is presented, which is driven directly by linear voice coil motors. Firstly, the optimum configuration is obtained based on conditioning index of Jacobian. Then optimal dimension design is performed based on the proposed comprehensive performance evaluation index, which integrating kinematic dextrous with dynamic manipulability together. The distribution of conditioning index, dynamic manipulability and acceleration over the workspace is analysed respectively according to optimal structure. Lastly experimental results demonstrated that the novel robot allows a workspace of 55times55 mm2 and an acceleration exceeding 12 g with repeatability better than 1.5 mum. The obtained technical characteristics indicate that the robot can satisfy the proposed application.

A Novel High Speed/High Precision Displacement Measurement Method Using Double Grating Scales for a Macro/Micro Driven System: Principle Design and Experimental Verification

High speed and high precision displacement measurement is hard to be achieved because of the restriction of displacement sensors: the maximum allowable moving speed is in contradiction to the measuring accuracy. In order to enable the high precision displacement measurement of the ending to achieve high speed moving course, a high speed and high precision displacement measurement method based on double grating scales is presented. Based on the analysis of measuring theory of grating scale, the method of signals switch and merge of double grating scales is discussed. By using the analysis of the subdivision error of Moire fringe, the error of the count impulses switch process is decreased. The signal process circuit is designed by using the programmable logic device-FPGA. And through the logical and timing simulation by the design software of FPGA, the feasibility of method is proved. The experimental results verify that the method is effectively used to control a macro/micro driven system.

An approach for generating high velocity and high acceleration trajectories of industrial robots

For fast-motion industrial robots, the limits of the velocity and the acceleration vary over the whole work-space. To make industrial robots move with fully high velocity and high acceleration along the specified trajectory in the entire workspace, a trajectory generation technique for fast-motion industrial robots is presented in this paper. The maximum possible values of the velocity and the acceleration along the specified trajectory are firstly investigated, in consideration of the speed and torque limits of the actuators. Then, based on these maximum velocity and maximum acceleration, the proposed technique generates various motion profiles by using coefficients which are determined by the acceleration and deceleration characteristics. Finally, the experiment is conducted to confirm the proposed technique by commanding a two-degree-of-freedom (2-DOF) direct-drive planar parallel robot to move along the trajectories with the unsymmetrical smooth motion profile generated by the proposed technique.

Gold wire stress analysis of wire feed system in automatic wire bonder

The wire feed system is an important subsystem of typical automatic wire bonder. The resistance control of wire transmission and tensile force control are the key technologies of the wire feed system, which has a strong impact on the bonding quality. This paper describes the stress analysis of gold wire in the automatic wire bonder. The analysis is useful in the low friction wire feed system and the low resistance transmission. Two stress models of gold wire are developed in the air guide and vacuum tensioner. The relationships between the control parameters of air guide and vacuum tensioner and the stress on gold wire are found out. Results of the experiments of this stress analysis procedure are given to illustrate the proposed models. Emphasis is placed on the construction of the mathematical models of air guide and vacuum tensioner by which the stress of gold wire is evaluated.

Fast-motion trajectory generation for a new direct-drive planar parallel manipulator

A new direct-drive planar parallel robotic manipulator is presented for fast-motion positioning in this paper. Because of the nonlinearity of kinematics and dynamics of the robotic manipulator, the achievable maximum velocity and maximum acceleration vary at different points and directions in the whole workspace. In order to make the manipulator move with fully high velocity and high acceleration along the specified trajectory in the workspace, a fast-motion trajectory generation technique is introduced in detail. Given the limitations on speed and torque of the actuators, the available values of maximum velocity and maximum acceleration along the specified trajectory are firstly derived. Then, based on these values, several motion profiles are generated with different acceleration and deceleration characteristics. Finally, the experiments of trajectory generation are conducted on the new robotic manipulator, which moves along the trajectories with the unsymmetrical velocity profiles, and the results validate the proposed technique

Vibration suppression for wafer transfer robot during trajectory tracking

In order to solve the vibration during the process of transferring wafers and achieve the purpose of transferring wafers accurately and stably, the wafer transfer robot dynamic model was modelled and the strategy of vibration suppression based on input shaping was proposed. Based on the characteristics of wafer transfer robot, ZV input shaper and skewed shaper was designed to solve the single axiss vibration caused by timing belt and harmonic reducer, and most importantly, the vibration of end effector during trajectory tracking was suppressed with input shapers using multi-modal system cascade method in the Cartesian space. Through comparison of different effects during the straight-line trajectory tracking in different spaces, the experiments demonstrated that the input shaping in Cartesian space suppressed vibration of end effector and improved the accuracy of trajectory tracking.

Research on a New Composite Ultrasonic Energy Transmission System with the Serial Structure

A composite ultrasonic energy transmission system with the serial structure horn is presented for the wire bonding application. Compared with the conventional parallel structures, this one can greatly reduce the structural coupling effect. Energy density formulation is deducted theoretically. Through the vibration characteristic analysis and FEA verification, it is proved that this serial structure can obviously increase the composite output amplitude of the ultrasonic horn and the ultrasonic energy density so that it will shorten the bonding time and improve the bonding efficiency.