Jeremy S. Daily

Data reliability from an instrumented vertical jump platform.

Caruso, JF, Daily, JS, Mclagan, JR, Shepherd, CM, Olson, NM, Marshall, MR, and Taylor, ST. Data reliability from an instrumented vertical jump platform. J Strength Cond Res 24(10): 2799-2808, 2010-A Vertec jump measurement and training system measures vertical jump heights but not additional variables that would reveal how the performance was achieved. Technology advances to equipment now include additional variables that elucidate how jump performance is achieved. However, acceptance of new jump-related equipment is predicated on the reliability of the vertical heights it measures in relation to those assessed by the Vertec. Thus, our study compared vertical jump height reliability data from a newly created instrumented platform to those concurrently derived from the Vertec. Methods required subjects (n = 105) to perform 2 jump trials separated by at least 2 days of rest. Trials began with a warm-up, followed by 3 to 5 maximal-effort jumps. The Vertec was placed directly over the platform so, as jumps occurred, subjects took off and landed on the instrumented device. At the jump apex subjects contacted the highest Vertec slapstick possible to assess maximum height attained. Four height measurements were derived from each jump: 3 platform-based calculations (from subjects take-off, hang time, and landing) and 1 Vertec. The platform-based calculations were compared to Vertec data to assess the reliability of the instrumented device. Intraclass correlation coefficient (0.90), coefficient of variation (17.3%), standard error of measurement (0.9 cm), and smallest real difference (3.7 cm) results showed heights calculated from platform take-offs were most reliable to Vertec values. It was concluded take-off from the platform yielded jump heights that are a viable alternative to those derived from the Vertec. Practical applications suggest coaches may use the platform to derive reliable vertical jump data in addition to other variables to better understand the performance of their athletes.

Accuracy of event data in the 2010 and 2011 Toyota Camry during steady state and braking conditions

Independent verification of the accuracy of data from Event Data Recorders (EDRs) is useful when using the information to help reconstruct a crash. To this end, the accuracy of the EDR function of the Airbag Control Module (ACM) was tested on 2010 and 2011 Toyota Camry sedans during straight line operation. During steady state operation, and maximum ABS-braking runs starting from approximately 80 km/h (50 mph), and 113 km/h (70 mph), non-deployment events were artificially induced to store event data. Following each run, the EDR was imaged using the Bosch Crash Data Retrieval (CDR) system. The CDR reported speed values were compared to Racelogic VBox differential GPS speed records. Data recorders were also used to monitor the vehicle Controller Area Network (CAN) bus traffic, including the indicated speed, brake pressure, engine RPM, and accelerator pedal position. The speed and RPM reporting algorithms stated in CDR Data Limitations were confirmed. Exemplar graphs of EDR-reported speed/brake/RPM/accel pedal data versus GPS speed and CAN bus data are presented and discussed. The timing of the reported data with respect to the event is also discussed. The difference between vehicle speed recorded by the EDR and the GPS speed during steady state operation varied from +0.4 to −2.3 km/h, with the EDR typically reporting lower than the GPS. During heavy braking the difference in speed was observed to be from −7 to +15 km/h, with wheel slip causing negative differences, and time delay since the last CAN bus update causing positive differences. Language: en

Practical DoS Attacks on Embedded Networks in Commercial Vehicles

The Controller Area Network (CAN) protocol has become the primary choice for in-vehicle communications for passenger cars and commercial vehicles. However, it is possible for malicious adversaries to cause major damage by exploiting flaws in the CAN protocol design or implementation. Researchers have shown that an attacker can remotely inject malicious messages into the CAN network in order to disrupt or alter normal vehicle behavior. Some of these attacks can lead to catastrophic consequences for both the vehicle and the driver. Although there are several defense techniques against CAN based attacks, attack surfaces like physically and remotely controllable Electronic Control Units (ECUs) can be used to launch attacks on protocols running on top of the CAN network, such as the SAE J1939 protocol. Commercial vehicles adhere to the SAE J1939 standards that make use of the CAN protocol for physical communication and that are modeled in a manner similar to that of the ISO/OSI 7 layer protocol stack. We posit that the J1939 standards can be subjected to attacks similar to those that have been launched successfully on the OSI layer protocols. Towards this end, we demonstrate how such attacks can be performed on a test-bed having 3 J1939 speaking ECUs connected via a single high-speed CAN bus. Our main goal is to show that the regular operations performed by the J1939 speaking ECUs can be disrupted by manipulating the packet exchange protocols and specifications made by J1939 data-link layer standards. The list of attacks documented in this paper is not comprehensive but given the homogeneous and ubiquitous usage of J1939 standards in commercial vehicles we believe these attacks, along with newer attacks introduced in the future, can cause widespread damage in the heavy vehicle industry, if not mitigated pro-actively.

Accuracy and Characteristics of 2012 Honda Event Data Recorders from Real-Time Replay of Controller Area Network (CAN) Traffic

Prior EDR testing methodologies required setting events in the airbag control module in the vehicle during controlled driving behavior. Duplicating events was nearly impossible, and it was difficult to separate how much differences in recorded speeds to reference speeds was due to measurement error, wheel slip, reporting time delays, or data truncation within the EDR. Recording thresholds have also increased making non-deployment and deployment events closer in magnitude, increasing the risk of accidentally exceeding the deployment threshold while setting events. The new methodology eliminates the risk of accidentally deploying airbags while gathering GPS and CAN bus data in the test vehicle. The techniques presented in this paper also allows gathering of data in vehicle without tampering with the airbag control module, which reduces the potential liability to testers using rental or borrowed test vehicles. The new methodology allows for repeatable testing and mapping the transfer function between the vehicle CAN bus data and the EDR. Should a manufacturer make a design change to an ACM EDR, identical inputs can be given to exemplar ACMs from before and after the changes to document any change in the transfer function. This methodology allows researchers the ability to re-create events of interest in a low-cost, repeatable manner. The accuracy of the 2012 Honda CR-V and 2012 Honda Civic event data recorders were tested using this new two part methodology. First, the test vehicles were instrumented with both a Racelogic VBOX differential GPS speed measurement system and a Vector CAN data logger. The measurements from the VBOX were transmitted onto the vehicles Controller Area Network (CAN) bus that also contained messages reflecting indicated vehicle speed, brake status, accelerator pedal position, steering wheel angle, individual wheel speeds and other signals. This put the GPS speed data on the same time base as the vehicle CAN speed signal such that no additional synchronization was required. This permitted analysis of the accuracy and update rate of the vehicle speed CAN signal, which is the source for speed data used in the Event Data Recorder (EDR). Second, a system was developed to replay the recorded CAN data to an exemplar airbag control module in the laboratory, such that the exemplar was receiving data exactly as if it were in a moving vehicle. A pneumatic fixture with a slide was built to allow the exemplar module to be accelerated to nearly 10 km/h (6 mph) and then stopped in about 80 msec. to create a non-deployment event that met the minimum 5 mph delta-V over 150ms threshold. Actuation of the event setting fixture was computer controlled (using LabVIEW) and synchronized with the CAN replay system so that the desired test condition could be replicated precisely. An external accelerometer was mounted to the airbag control module to mark when the ACM began recording and the accelerometer data was matched to the acceleration and delta-V data in the EDR. The desired test conditions were replayed to the airbag control module and a series of non-deployment events were set. Each event on the EDR data was read using the Bosch Crash Data Retrieval system. The EDR data was compared to the inputs, and it was determined that the two byte vehicle CAN bus signal was truncated to the next lower whole km/h when recorded in the EDR. Under steady state conditions the speed data was accurate within 2%. The vehicle CAN signal published new values every 0.1 seconds, and the CR-V updated values every 0.1 seconds, but the Civic only updated every 0.6 seconds during hard brake events. During hard ABS braking events the expected wheel slip led to the vehicle speed signal under-reporting ground speed, but the delay in the CAN bus update rate resulted in over-reporting ground speed in many of the tests. Language: en

Light Vehicle Event Data Recorder Forensics

While traffic crash reconstruction focuses primarily on interpreting physical evidence, the proper generation and preservation of digital data from Event Data Recorders (EDRs) can provide invaluable evidence to crash reconstruction analysts. However, data collected from the EDR can be difficult to use and authenticate, as exemplified through the analysis of a General Motors 2001 Sensing and Diagnostic Module (SDM). Fortunately, advances in the digital forensics field and memory technology can be applied to EDR analysis in order to provide more complete and usable results. This paper presents a developmental model for EDR forensics, centered on the use of existing digital forensic techniques to preserve digital information stored in automobile event data recorders.

Automobile Event Data Recorder Forensics

Automobile event data recorders (EDRs) provide vital information for reconstructing traffic crashes. This paper examines the primary issues related to evidence recovery from EDRs and its use in crash reconstruction. Recommendations related to the use of EDR data in court proceedings are also presented.

A Dissipated Energy Approach to Fatigue Crack Growth in Ductile Solids and Layered Materials

This paper summarizes recent work on a new theory of fatigue crack growth in ductile solids based on the total plastic energy dissipation per cycle ahead of the crack. The fundamental hypothesis of the theory proposes a unified criterion for crack extension under monotonic and fatigue loading, so that the fatigue crack growth rate is given explicitly in terms of the total plastic dissipation per cycle and the monotonic fracture properties of the material. The total plastic dissipation per cycle is obtained by 2-D elastic-plastic finite element analysis of a stationary crack under constant amplitude loading, for both mode I (C(T)) and general mixed-mode I/II specimen geometries. Both elastic-perfectly plastic and bi-linear kinematic hardening constitutive behaviors are considered, and numerical results for a dimensionless plastic dissipation per cycle are presented over a wide range of relevant mechanical properties and mixed-mode loading conditions. Results are further extended to include fatigue delamination of layered material systems, where either discrete mismatches or a continuous grading of mechanical properties can exist across the interface.

Reproducibility of vertical jump data from an instrumented platform

To assess the reproducibility of data collected from a newly created instrumented platform that measures vertical jump performance, healthy college-age subjects (n = 178) made three visits to our laboratory. Per jump, the platform offered six performance-related variables: static weight, time to takeoff, peak takeoff force, and maximum jump heights as they ascended, remained in the air and landed. Per subject, the two highest jumps from the final two visits were used to assess data reproducibility. Prior to the reproducibility assessment, Z-scores identified statistical outliers that were removed from subsequent analyses. Paired intra- and inter-jump session data per variable were assessed with the following statistical test-retest tools: intraclass correlation coefficients, coefficient of variation, standard error of measurement, smallest real difference and critical difference. Current results show most data had a high level of reproducibility with few exceptions. Since the platform also has potential applicability in the rehabilitation of disabled persons, future research should assess the data reproducibility associated with gait, balance and mobility collected from the device.

Buckling Analysis of Drill Strings in Inclined Wellbores Using the Explicit Finite Element Method

Understanding drill string buckling behavior is a significant challenge to the petroleum industry. In this paper, the explicit finite element method implemented in Abaqus software is employed to study the buckling of drill strings for inclined straight wellbores. Classic solutions for the critical buckling length of self-weighted columns as well as critical buckling load for drill pipe inside inclined wellbores are compared to explicit FEA and accurate results are provided by the finite element based predictions. The effect of different inclination angles and string effective weight due to the buoyancy effect has been studied and the results for sinusoidal and helical buckling are compared to analytical results and experimental data in the literature. The theoretical predictions for different inclination angles agree with the simulations. Theoretical buckling load of inclined drill strings approaches zero by decreasing the effective weight of a floating drill string. However, the results of finite element simulations show that significant buckling load would still exist for very low drill string effective weight. These results are confirmed by experimental results provided by other researchers. Overall, the efficacy of using explicit finite element methods to model drill string buckling behavior is demonstrated.Copyright

Determining the Scatter in Fatigue Crack Growth Rate Based on Variations in Bulk Property Data

A technique to predict the variability of the Paris regime fatigue crack growth rates in ductile materials based on bulk property (yield strength, hardening modulus, and fracture toughness) variation is presented. The prediction, based on the plastic dissipation in the reversed plastic zone ahead of the crack tip, is carried out for Ti-6Al-4V. The empirical distributions of the bulk properties of Ti-6Al-4V are characterized and directly used in the probabilistic assessment of the fatigue crack growth rate. Since computing the plastic dissipation is a computationally intensive procedure, a novel sampling scheme based on confidence interval minimization was used to generate the empirical distribution of fatigue crack growth rate. This technique also predicts correlation between fatigue crack growth rate and fracture toughness, which may be useful in probabilistic design of turbines.Copyright