Development Of A Real Time, Industrially Hardened, Ski Performance Analysis System

At Penn State Altoona, as a senior design project in the Electro-Mechanical Engineering Technology department, we have developed an instrumentation system to measure the dynamic response of skis under real time skiing conditions. The intent is to monitor the ski response during different styles of high performance use. Consequently, initial modeling and static testing were required to determine both sensor type and placement to capture the critical parameters during a specific ski maneuver. Apart from the determination of sensor type and optimum placement, environmentally hardening (handling of large temperature variations and large and rapid loading) of the system proved challenging. The specific measurements performed were ski displacement and acceleration. In this work, we will discuss the design and construction processes, the testing processes, and the specific results of the static and dynamic testing. This information and testing system, which is coordinated with ski manufacturers, will then be available for the future redesigning of skis for specific performance constraints such as freestyle or slalom. Introduction The use of sophisticated industrially hardened data acquisition (DAQ) tools and software along with instrumentation is a growing field in industry. The applications cover a very broad range from measuring human biomechanics to the thermal conductivity of fluids in motion. 1, 3 The typical process of instrumentation and data acquisition is as follows. Transducers are applied to the system to measure some physical quantity and convert it into an electrical signal. This electrical signal must sometimes be amplified and electrical noise must be filtered. These electrical signals are then converted to digital format for data storage in a data acquisition device. 5 The collected data can then be retrieved and uploaded to a number of software packages for analysis. While the concept of monitoring of a physical event is simple enough, the difficulty arises when the system must perform outside a laboratory-type setting. 4 Currently most ski analysis systems measure static response in a laboratory setting. 9 The associated DAQ equipment is not designed to handle the harsh environment in which actual skiing is performed. Additionally, ski loads are primarily dynamic. Therefore, the design of a system that can withstand the environmental conditions of a ski slope and acquire dynamic real time data is a significant challenge. However, the resultant data and subsequent analysis offers significant insight into ski behavior for ski users P ge 820.1 “Proceedings of the 2003 American Society for Engineering Education Annual conference & Exposition Copyright © 2003. American Society for Engineering Education” and designers/manufacturers. Additionally, the value of this project exists on multiple levels for engineering and engineering technology students. Firstly, it prepares the students for developing system test schemes as is done in industry. Many businesses are now eliminating testing departments and are requiring that the design engineers test their own projects. So, it is essential that new graduates have some familiarity with instrumentation and data acquisition systems. 4 Secondly, it gives the students an opportunity to develop a project that is open-ended as opposed to a strictly defined design project. The general project scope and goals provide direction, while the undefined result allows for creative design alterations. Lastly, the students get to experience and work with a project from birth to completion. This allows the students to participate and obtain experience in all phases of a design project. Design Issues and Design Criteria The project goal is defined as developing a real time, industrially hardened, ski performance analysis system. To begin, the team chose specific types of measurements that were to be taken (acceleration, force, and displacement). It was determined that strain gauges and accelerometers would work well to measure the parameters. The transducers needed to be able to withstand rapid load changes and extreme temperature changes. Before purchasing sensors, a compatible data acquisition unit had to be found. The minimum specification requirements of the data acquisition system were defined as follows: Must have at least 8 analog double ended channels • Must have a minimum sample rate of 5 kHz per channel • Must have a minimum memory amount of 100 MB • Must be portable and able to be powered from a dc battery power source • Must be industrially hardened to withstand cold temperatures, moisture, and vibration • Must be within a reasonable price range • Preferably have built-in signal conditioning for strain gauges and accelerometers • Due to budgetary constraints, the team had to extensively search for a system to meet the minimum specifications. The data acquisition system selected (the Omega OMB-LogBook 300) was very versatile and met all the requirements except it did not have the desired built-in signal conditioning. The software for acquisition configuration was LogView 2.3, and the data viewing software was PostView 3.4. For the system to read analog inputs, the DBK 11A expansion card with screw terminals was purchased. For remote system control during testing, the LBK 1 remote terminal was purchased. The block diagram of the system identifies the connection scheme of all the hardware, Figure 1.