Sam Naghshineh

DEVELOPMENT OF A VIRTUAL REAL TIME UPPER BODY LINK SEGMENT MODELING USING 3D ACCELEROMETERS

Sam Naghshineh, Golafsoun Ameri, Mazdak Zereshki, Dr. Sri Krishnan, Dr. Mohammad Abdoli-Eramaki
Department of Electrical and Computer Engineering, Ryerson University, ON.
Department of Occupational and Public Health, Ryerson University, ON

Naghshineh et al. “Development of a virtual real-time upper body link segment modeling using 3D accelerometers.� Canadian Society for Biomechanics. 14 Mar, 2009. 79-80

Introduction

Human motion tracking has been normally developed by optoelectronic or electromagnetic systems that require proximity to the hardware components which makes it inappropriate for field studies in biomechanics. The advantage of accelerometers is to that they do not require line of sight and if they are designed and installed properly they might be able to replicate human motion.

Aim
Combined with a virtual model, eight tri-axial accelerometers are used to develop a real time model of the upper body including eight segments (left and right hand-forearms, arms, head, upper trunk, lower trunk, and pelvis) to track human motion for field studies. The ultimate goal is to develop both hardware and software algorithms to acquire best data with least error.

Method
Hardware design:
The sensor that is used in this design is HITACHI H48C (Parallax Inc, California, USA) tri-axial accelerometer which operates in series. Therefore, there is a chip select to  etrieve data periodically. Basic Stamp 2px (Parallax Inc, California, USA) microcontroller is chosen for this design since by uniting HITACHI H48C (Parallax Inc, California, USA) MEMS accelerometer with this microcontroller with a high number of bits (12), 0.2% accuracy can be achieved while keeping the cost low. To compensate for the low sampling rate caused by using this microconroller (8 samples/s), two BS 2px (Parallax Inc, California, USA) microcontrollers are used so that each would receive data from 4 sensors instead of 8 to double the sampling rate. Power consumption was another factor that was considered when choosing a suitable microcontroller.

Software Design

The angle of rotation is obtained from the gravitational acceleration sensed by each axis of the accelerometers by utilizing the tan inverse functions. To maintain a real time system a chip select, timer, and counter are exploited and implemented in the software design. Labview 8.1 (NI, USA) is used to acquire three dimensional orientations to be displayed on the LSM.

Conference: OBC 2009 (Ontario Biomechanics Conference)

Detailed project Document:

HME Detailed.pdf