Final Design

   The following items were designed and delivered in order to meet the specified goals of Calit2 for this project:

Design Process

            Assumptions:

·         The magnitude of acceleration provides an accurate description of rope damage

·         Climber will not climb more than 100 meters away from the location of cellular device

·         Use of device will not exceed 12 hours of continuous use without recharging

·         Dummy is mainly used to simulate mass of a climber and the dynamics of the human body are not a key factor to determine fall severity in terms of rope damage.

            Test Dummy:

·         The test dummy was designed to simulate a falling rock climber

·         It is built from sections of PVC tube and its final weight is approximately 65 kg

·         It has segments which represent the general layout of the human body and joints are simulated using connected rope

·         The made constriction of dummy design was budget. While much more accurate human dummy’s exist this was the best solution arrived at while staying within our restrictive budget.

·         PVC tube and sand were used for cost reasons and were effective ways to simulate the mass of a climber

·         Simple density calculations were performed before purchasing materials to ensure appropriate weight of dummy

Climbing Equipment:

·         Climbing equipment was selected from REI, a common supplier for climbing gear

·         Much of the budget was expended here but it was considered a priority in order to ensure safety with equipment such as locking carabineers as well as to accurately simulate rope dynamics with a high quality climbing rope

·         Dry ropes were purchased which were slightly more expensive but rated to take more falls in order to increase the amount of testing we were capable of performing

Sensor Array: 

·         An MPU-9150 board with three axis accelerometer, gyroscope, and magnetometer as well as on board digital motion processor was implemented as the main sensing element due to its relative low cost and ability to handle low level digital to analog conversion and basic motion analysis internally

·          An Arduino 3.3V pro-mini was implemented for its simplicity and ability to run off a 3.7V input which only requires a single Li-ion cell

·         Bluetooth communication was included so that high level data processing could be conducted remotely using a smartphone application interface

·         An on board SD card data logger was included to ensure data capture even in the event of Bluetooth failure

·         Though currently the three axis gyro and magnetometer are unused these components would be key in future development of this product in order to determine climber orientation and implement Kalman filtering to determine climber position and height

 Packaging: 

·         A lightweight, low cost and sturdy package was printed using the on campus 

3-D printer 

·         This package is small enough to fit in a climbers pocket but its size could be easily reduced in the future by moving from multiple breakout boards which require excessive space to a single printed board which includes all the components in a surface mounted layout

Results

    A three dimensional theoretical simulation was done to determine the acceleration of a falling climber. The magnitude of acceleration is considerably easy to measure than a component of acceleration due to difficulty of estimation of orientation. The three dimensional simulation was done to see if magnitude of acceleration was considerably different from vertical component and to note if there were any discrepancy between a 1D and 3D fall. The MATLAB Code is in the Executive Summary Appendix. The results are shown in the following plots below.

MATLAB Simulation of a Falling Climber

    Two drop sites were used for the purpose of this project. The first site was at the University of California San Diego EBU II building at the 3rd floor. The setup involved loading one end of an I-beam with approximately 140 kg (~300 lbs) and the other end sticking out over the ledge. A belayer was down at the ground floor, and the climbing rope looped from him up through the carabiners attached to the overhead I-beam and finally attached the harness on the test dummy. The sensor package recorded the following data with a 14 meter fall of the dummy.

Recorded Acceleration During Drop Test