Development of a transfer function for DML's IMU

DML的GaitSmart系统使用惯性测量单元（伊穆斯）来测量一个人走路时四肢的运动方式。然后，这些数据将以简单易读的报告形式呈现，也可用于确定个性化的锻炼计划。有许多疾病会影响人的行走方式，包括骨关节炎、虚弱、中风和帕金森氏病。由于疾病的早期发作，正常步态模式的变化很小，因此测量系统必须精确到一定程度。对于医疗器械，该精度应参考SI单位。DML已经通过之前与NPL成功合作的A4i项目确定了稳态循环运动的精度。该项目的目的是扩展这一点，使其包括由于医疗条件和步态事件（如脚跟着地）而引入的自然干扰的准确性。为了做到这一点，IMU需要在不同平面的周期运动期间受到脉冲响应。然后，使用计量系统测量的取向和IMU响应将用于确定传递函数。该传递函数可用于确定IMU在任何运动下的预期精度。该方法适用于任何拥有基于IMU的系统的公司，并将为SI单位提供参考标准。随着可穿戴技术变得越来越普遍，对参考标准的需求变得至关重要。该项目将使NPL能够提供在该项目中开发的解决方案。

DML's GaitSmart system uses Inertial Measurement Units (IMUs) to measure how a person's limbs move when they walk. This data is then presented in a simple to read report and can also be used to determine a personalised exercise plan. There are many conditions that affect the way a person walks, including osteoarthritis, frailty, stroke and Parkinson's Disease.With the early onset of conditions, changes from a normal gait pattern are small, and therefore it is essential that the measurement system is accurate to within a degree. And for a Medical Device this accuracy should be referenced back to SI Units.DML has already ascertained the accuracy from steady state cyclic motion through a previous successful A4i project with NPL. The aim of this project is to extend this so that it includes the accuracy when natural interferences are introduced as a result of medical conditions and gait events such as heel strike.In order to do this the IMU needs to be subjected to an impulse response during cyclic movement in the different planes. The orientation measured using a metrology system and the IMU response will then be used to determine the transfer function. This transfer function can then be used to determine the expected accuracy under any motion that the IMU may be exposed to.This approach will be applicable for any company with an IMU based system and will provide a reference standard back to SI units. As wearable technology becomes more widespread the need for a reference standard becomes essential. This project will enable NPL to offer the solution developed in this project.