Danny Mann

Sensitivity and diagnosticity of NASA-TLX and simplified SWAT to assess the mental workload associated with operating an agricultural sprayer

The objectives of the present study were: a) to investigate three continuous variants of the NASA-Task Load Index (TLX) (standard NASA (CNASA), average NASA (C1NASA) and principal component NASA (PCNASA)) and five different variants of the simplified subjective workload assessment technique (SSWAT) (continuous standard SSWAT (CSSWAT), continuous average SSWAT (C1SSWAT), continuous principal component SSWAT (PCSSWAT), discrete event-based SSWAT (D1SSWAT) and discrete standard SSWAT (DSSWAT)) in terms of their sensitivity and diagnosticity to assess the mental workload associated with agricultural spraying; b) to compare and select the best variants of NASA-TLX and SSWAT for future mental workload research in the agricultural domain. A total of 16 male university students (mean 30.4 ± 12.5 years) participated in this study. All the participants were trained to drive an agricultural spraying simulator. Sensitivity was assessed by the ability of the scales to report the maximum change in workload ratings due to the change in illumination and difficulty levels. In addition, the factor loading method was used to quantify sensitivity. The diagnosticity was assessed by the ability of the scale to diagnose the change in task levels from single to dual. Among all the variants of NASA-TLX and SSWAT, PCNASA and discrete variants of SSWAT showed the highest sensitivity and diagnosticity. Moreover, among all the variants of NASA and SSWAT, the discrete variants of SSWAT showed the highest sensitivity and diagnosticity but also high between-subject variability. The continuous variants of both scales had relatively low sensitivity and diagnosticity and also low between-subject variability. Hence, when selecting a scale for future mental workload research in the agricultural domain, a researcher should decide what to compromise: 1) between-subject variability or 2) sensitivity and diagnosticity. Statement of Relevance: The use of subjective workload scales is very popular in mental workload research. The present study investigated the different variants of two popular workload rating scales (i.e. NASA-TLX and SSWAT) in terms of their sensitivity and diagnositicity and selected the best variants of each scale for future mental workload research.

A study of tractor yaw dynamics for application in a tractor driving simulator

This study was performed to investigate tractor yaw dynamics for application in a tractor driving simulator. Tractor yaw rate was measured at different forward speeds in response to a range of steer angle input frequencies. Tire cornering stiffness and relaxation length values were estimated using a system identification approach. Analysis shows that the bicycle model accurately predicted tractor yaw rate at low steer angle frequencies. At higher frequencies, though, the consideration of tire relaxation length was necessary. Sensitivity of the model to estimation of tire parameters was also discussed.

A New Methodology for Evaluating Guidance Systems for Agricultural Vehicles

Evaluation of new technologies in agricultural machinery guidance is very important and can help producers choose the right equipment for their applications. At present, comparison between different guidance systems has typically been based on the amount of guidance error (i.e., the deviation of the vehicle from the desired path). This paper proposes a new methodology for evaluating these guidance systems. An RTK-GPS was used to record the exact location of a tractor while the operator used one of seven lightbar guidance systems to drive along parallel passes in the field. Frequency-domain analysis of the tractor path was used to compare the performance of the seven systems. Fourier analysis of the tractor path was performed by dividing the changes in the tractor path into low-, medium-, and high-frequency changes. Guidance systems with lower driving error have more high-frequency changes in the tractor path. This means that there is a tradeoff between the driving accuracy and operator workload. It is suggested that a comparison of the frequency spectrum of the tractor path can be used to better evaluate or compare agricultural guidance systems.

Concurrent Teaching of Technical Communication and the Engineering Design Process

A fundamental component of any capstone design class is the preparation of a written design report and an oral presentation describing the design solution. The recording of project information is another essential communication skill that is critical to the engineering design process. Thus, it has long been recognized that communication is essential for the design engineer and essential to the engineering design process. For the last four years, technical communication has been formally integrated with the capstone design courses in the Department of Biosystems Engineering at the University of Manitoba. This paper will review the learning objectives, the technical communication curriculum, and the experiences from the past four years with emphasis on the lessons that have been learned. Currently, increased emphasis is being placed on the completion of project journals because students are unaware of the value associated with a detailed project journal.

Drivers’ Mental Workload In Agricultural Semi-Autonomous Vehicles

Drivers’ mental workload when using driving assistant systems and in-vehicle automation has been the subject of many studies in recent years. Drivers of semi-autonomous agricultural vehicles are experiencing an increasing number of automated systems. Due to implications of automation support on the operators’ performance, a human factors perspective is needed to identify the consequences of such automated systems. In this simulator study, the effects of vehicle steering and implement monitoring and control automation were investigated using a tractor air-seeder system as a case study. Experiments were conducted using the tractor air-seeder driving simulator (TAS-DS) located in the Agricultural Ergonomics Laboratory at the University of Manitoba. Study participants were university students with tractor driving experience. Based on the results from the experiment, most of the automation conditions impose moderate levels of mental workload on operators. Implement monitoring and control automation show significant effect on the drivers’ mental workload, contrary to the steering automation.

INVESTIGATING THE RELATIVE IMPORTANCE OF THE CEAB GRADUATE ATTRIBUTES: STUDY DESIGN AND INITIAL FINDINGS

This study represents the PhD thesis research of the lead author. The greater study is designed as a mixed-methods explanatory case study. The overarching objective is to explore whether the CEAB graduate attributes are emphasized in the engineering programs in the Faculty of Engineering at the University of Manitoba in the most optimal way. The first phase of the study is designed to determine the relative importance and the levels of dependencies of the graduate attributes across three engineering stakeholder groups: faculty, students, and industry members. In this paper, the design and methodology of the first phase of this mixed methods research study are explained, and the preliminary findings from the participation rates and participants’ familiarity with the graduate attributes on the survey data are presented. Results show that a sizable percentage of students, faculty and industry members are not highly familiar with the CEAB graduate attributes. Therefore, work to develop a common knowledge about the CEAB graduate attributes needs to continue.

Design and Evaluation of Individual Elements of the Interface for an Agricultural Machine

If a user-centered approach is not used to design information displays, the quantity and quality of information presented to the user may not match the needs of the user, or it may exceed the capability of the human operator for processing and using that information. The result may be an excessive mental workload and reduced situation awareness of the operator, which can negatively affect the machine performance and operational outcomes. The increasing use of technology in agricultural machines may expose the human operator to excessive and undesirable information if the operators information needs and information processing capabilities are ignored. In this study, a user-centered approach was used to design specific interface elements for an agricultural air seeder. Designs of the interface elements were evaluated in a laboratory environment by developing high-fidelity prototypes. Evaluations of the user interface elements yielded significant improvement in situation awareness (up to 11%; overall mean difference = 5.0 (4.8%), 95% CI (6.4728, 3.5939), p 0.0001). Mental workload was reduced by up to 19.7% (overall mean difference = -5.2 (-7.9%), n = 30, a = 0.05). Study participants rated the overall performance of the newly designed user-centered interface elements higher in comparison to the previous designs (overall mean difference = 27.3 (189.8%), 99% CI (35.150, 19.384), p 0.0001.

Effect of Steering Torque Feedback on Driving Performance in a Tractor Simulator

A tractor simulator is being developed at the University of Manitoba and it is necessary to determine appropriate steering torque feedback that will promote driver control. An experiment was conducted with ten subjects to determine how constant torques of 0, 2, 5, and 10 Nm would affect driving performance in a tractor simulator. When no torque feedback was applied to the steering column, subjects had difficulty following a prescribed path and had a large lateral error. As steering torque was increased, subjects tended to have more control and were able to follow the prescribed path with more precision. The experimental evidence suggests that a constant steering torque of 10 Nm is appropriate to promote driver control in a simulator environment.

Does Agricultural Spraying Involve Mental Workload

Mental workload is defined as the proportion of mental resources invested to meet the task demand. This study measures the mental workload associated with agricultural spraying under simulated day, dusk, and night driving conditions. Each of the three participants received two, 15 min testing sessions. Each session consisted of a set of three randomized, 5 min driving only, monitoring only, and a dual task under a randomized illumination level. Workload was measured by primary task performance, secondary task performance, eye-glance behaviour, low frequency heart rate variability power, and NASA-TLX scale. During the driving only condition, the driving error increased by 65% from day to night illumination. During the monitoring only condition, the reaction time increased by 3 times from day to night illumination. The dual-task-night-driving error was 43.9% and 41.9% more than day and dusk driving error. There was 19% average increment in driving error and 83.5% increment in reaction time for the left boom from single to dual task condition. During the dual task, 56.4% of the total driving time was spent to look at lightbar. During dual task night driving, subjects spent 6 times more looking at lightbar than outside. Driving and monitoring errors were more under night illumination. The HRV power spectra values and NASA-TLX did not behave as expected. However, the eye glance behaviour data, primary and secondary performance data suggested that agricultural spraying in response to a commercial GPS lightbar from day to night illumination invokes high mental workload.