Weihai Chen

Implementation of 2-axis Circular Interpolation for a FPGA-based 4-axis Motion Controller

To satisfy the motion control of numerical control machine and robot, this paper introduces an approach to implement 4-axis motion controller based on field programmable gate array (FPGA). Starting with introduction to existing excellent 4-axis motion controller MCX314, this paper describes the fundamental structure of the FPGA-based 4-axis motion controller. As the one of main function modules in controller, the implementation of 2-axis circular interpolation module in FPGA is the main content to be discussed in the paper. Employing a novel analogy digital differential analyzer (DDA), the interpolation module avoids plentiful complex on-the-motion computation with skillful combination with the hardware structure of FPGA; hence the real-time performance and precision are enormously improved. In the paper, the principle of algorithm and approach of hardware implementation are discussed in detail; with introduction to the structure of the circular interpolation module, a testing platform is developed to evaluate the performance of the module. The testing experiment indicates that the performance of controller is excellent, and the implementation approach will be valuable for domestic research and development about the motion controller.

Kinematic Analysis and Simulation of a 7-DOF Cable-Driven Manipulator

To improve the load capacity of the manipulator, based on the geometry analysis and screw theory, this paper is focused on the configuration design, cable-driven manner, and kinematics control for a cable-driven 7-DOF manipulator. First, aimed at the choice of cables-driven manners, a cable-driven mechanism that is coupled between elbow and wrist, and between shoulder and elbow is designed. Second, taking the 7-DOF joints such as the shoulder, elbow and wrist as medium, the relationship between the end-effector and driven cables is analyzed, i.e. through considering the relationship among the end-effectors pose and joint angles first for the manipulator, and then considering the relationship among joint angles and corresponding cable lengths, the kinematics of cable-driven manipulator can be solved. Lastly the simulation is realized. The simulation results show that the curves of manipulators joint angles and cable lengths are very smooth, and the error between actual trajectory and ideal trajectory of the end-effector is very small. These prove that the proposed algorithms are correct, the cable-driven manipulator runs well, and proposed approach can effectively overcome the negative effects from general robot brought by its deadweight.

Kinematic Analysis and Simulation of a Cockroach Robot

This paper does researches Into the configuration of our cockroach robot, its kinematics, and kinematic control. First, we design the cockroach robot, which has six legs with 18 DOFs in total. Each leg has 4 joints, coxa, femur, tibia, and tarsus. Based on cockroach robot kinematic analysis, screw theory, and POE (production-of-exponential) formula, this paper is focused on the inverse kinematics which uses Paden-Kahan sub-problems to directly obtain the displacement of joint angles. The forward kinematics derives the relationship between joint angles according to the natural restricts. Then, by using POE formula, it deduces the body pose and realizes online trajectory control and planning. What is more, this paper also demonstrates the inverse and forward kinematics, which lay a solid foundation for further kinematic analysis and trajectory planning.

Mathematical model of coordinate transformations for 3D Depth-of-field collection system

Calculating the Cartesian coordinate is the first step of image reconstruct based on primitive information from laser scanner. A novel 3D Depth-of-field information collection system in this article is consisted of tow 2D laser scanners and a servo-actuates rotating mirror assembly. The system has a much higher detecting precision than others which drive 2D laser scanner to rotate to get the 3rd dimension using motor. On the other hand the relationship between the 3D Cartesian coordination and the primitive information collected by the system is much more complicated than others because of the mirror assembly. Therefore traditional mathematical model which change polar coordinate to Cartesian coordinates can not be used to our system. In the article we build the solid geometry model of the laser beam between laser scanner and the detected object based on optical theory. Then a mathematical model for the transformations from primitive information to Cartesian coordinate is built according to the geometry model. The mathematical model has been tested in simulation on PC.

A flexible-resolution 3D laser scanning method based on DSP

This paper is focused on a method about collecting data from 3D data collection system for mobile robot efficiently. The system consists of a 2D laser scanner LMS291 and a motor module, through planning the motorpsilas velocity profile, the scanner can get the objectpsilas three-dimensional information, aiming at the traditional scanning modepsilas fault in collecting efficiency, this paper presents a flexible-resolution 3D laser scanning method based on DSP, utilizing the high capacity of DSP, we divide the process of collecting and location to different steps, according to the information collected from the fore-step, DSP can plan the next steppsilas velocity profile, through planning velocity profile, the scanner can have a high scanning efficiency, compared with the traditional scanning approach, utilizing this method can get more useful information under the same condition.

3D reconstruction embedded system based on laser scanner for mobile robot

For 3D reconstruction technology based on laser ranging for mobile robot, this paper presents the design of real-time embedded system for 3D data processing. Firstly, this paper introduces the home and abroad research situation of laser ranging for mobile robot, and analysis the method of 3D data acquisition with 2D laser scanner and ID driving motor module. Secondly, this paper introduces the hardware design and system building of multi-module embedded system, which consists of DSP data acquisition module, FPGA data processing module and ARM control. The ARM system is the main control system and realizes 3D reconstruction function. CAN bus communication is selected between these modules. Thirdly, this paper introduces the design of communication programming under ARM control system. At last, this paper presents the 3D reconstruction method with laser scanner and driving motor by Mesa3D based on RTLinux system.

Tension Analysis for a Cable-Driven 7-DOF Manipulator

A 7-DOF cable-driven manipulator is analyzed in the paper. First, according to the torque equilibrium, a static equation of the manipulator is deduced. Then, a dynamic formulation based on the static equation is followed, which includes the influence of external torque, gravity torque, inertial torque and gyroscopic torque. And then, an effective approach of calculating the external torque, gravity torque, inertial torque, gyroscopic torque and cable tension is obtained, which is simple to compute and its physical meaning is definite. Finally, the correctness of cable tension algorithm is testified by the simulation studies. Also, the elastic distortions of cables caused by cable tensions make the manipulator departure from its ideal trajectory and an error compensation is needed.

Walking phases detection on structured terrains by using a shoe-integrated system

Plantar pressure distribution and acceleration measurements are important to detect walking postures and states. This paper presents an in-shoe measurement and analysis system to do the detection. In-shoe information is acquired by the circuit board which is attached to the humans shank and transmitted to the remote receiver wirelessly. A real-time display and analysis software is developed. Experiments are taken on different terrains to analyze the walking states. The whole system presents a robust method to measure the walking phases and states.

An RGBD data based vehicle detection algorithm for vehicle following systems

Autonomous vehicle following system is an important research issue in the ITS(Intelligent Transportation System). After reviewing some currently used environment perception sensors, this paper employs Kinect sensor as the main device in detecting the angle and distance of the leader vehicle in relation to the following vehicle. This paper also propose a vision-based algorithm to process RGB-D data. For the color image, we use template matching and Camshift algorithm to detect and track our desired target, the result of which is to get an approximately location of the target in the image and a search window of a certain scale, both of which are used in the disposition of the depth image. We use K-means clustering to distinguish the leader vehicle and the background so that we can determine the pose information of our target. Offline simulations and online experiments have been performed to evaluate the effectiveness of the algorithm. Both of them have shown the feasibility in the vehicle following system.

Construction and realization of a 3D perceptual system based on 2D laser radar

This paper presents a 3D perceptual system based on 2D laser radar LMS291. The proposed system utilizes intelligent module to add a degree of freedom to LMS291. A new method of synchronization between LMS291 and intelligent module was proposed. We added Visual C++ multi-media timer to the timestamp method, the purpose we use this method is to change the level resolution conveniently, and control the number of the points we acquired, because in some condition we need speedy scanning to rebuild the reconstructed image of the terrain quickly. And we use Matlab to reconstruct the 2D and 3D images. To repair the singular points we selected absolute mean value method. The experiment shows that absolute mean value method works more accurately and effectively And this system we designed can be used for image reconstruction in unstructured environment by experiments.