Research On The Key Technology Of 3D Motion Capture System Based On Inertial Measurements Units

Limb movement is the most important part of human daily activities.The motion status of the limbs detected in real time can provide a more scientific diagnosis basis for the rehabilitation exercise process of patients with physical inconvenience.The 3D human motion capture system based on the inertial measurement unit can not be restricted by the use scene,The system provides patients with easy to use and comfortable to wear without burden,nternal IMU data fusion algorithm,which can output precise posture and joint angle of movement,and at the same time,it can provide patients with a visually consistent experience through the virtual human motion simulation model.This article focuses on the key technologies in the inertial motion capture system,There are 4 parts including hardware solution,data fusion algorithm,motion simulation technology and software implementation.At the end of each part,a physical experiment or a simulation experiment is designed to verify it.The specific research of each key technology in this article is as follows:The design of hardware scheme based on IMU is the basis for the realization of motion capture system.This article first analyzes the patient’s use needs and gives the design framework of the hardware system.Then for the four parts of control,acquisition,wireless transmission and power management,the device selection,function design and circuit design operation are carried out respectively.Finally,all devices are integrated to develop a hardware device that can collect and process nine-axis IMU data in real time.IMU data fusion algorithm research is divided into two parts: attitude estimation and joint angle estimation.According to the different characteristics of the IMU sensor,this paper uses the observed values of acceleration and magnetic field strength to correct the drift of the gyroscope,and designs an extended Kalman filter method based on quaternion.Then use the bone motion constraint relationship to identify the position of the joint axis in the local coordinate system of the IMU,and design a method for calculating the joint angle,which is used to estimate the pose quaternion when the joint angle produces relative motion.The motion simulation of the three-dimensional human body model needs to realize the establishment of the virtual character model and the driving control of the model in turn.In this paper,first,a simplified analysis of the structure of real bones is carried out.Based on the dynamic joint constraint relationship,a three-dimensional rod model and epidermis model are designed.Through the analysis of human motion process,the realization process of forward kinematics and inverse kinematics posture simulation are given respectively.At the end of the article,this paper designs a software solution for the motion capture system,which uses the MFC framework to write a TCP receiver program for the motion capture system.In addition,the motion simulation control of the three-dimensional human body model is realized in the Unity3 D software.The two softwares communicate through the local socket method.Experiments by gait simulation verify that the software’s solution can capture and reproduce human movements.