Kevin A. Rider

A Pilot Study of the Effects of Vertical Ride Motion on Reach Kinematics

Abstract : Vehicle motions can adversely affect the ability of a driver or occupant to quickly and accurately push control buttons located in many advanced vehicle control, navigation and communications systems. A pilot study was conducted using the U.S. Army Tank Automotive and Armaments Command (TACOM) Ride Motion Simulator (RMS) to assess the effects of vertical ride motion on the kinematics of reaching. The RMS was programmed to produce 0.5 g and 0.8 g peak-to-peak sinusoidal inputs at the seat-sitter interface over a range of frequencies. Two participants performed seated reaching tasks to locations typical of in-vehicle controls under static conditions and with single-frequency inputs between 0 and 10 Hz. The participants also held terminal reach postures during 0.5 to 32 Hz sine sweeps. Reach kinematics were recorded using a 10-camera VICON motion capture system. The effects of vertical ride motion on movement time, accuracy, and subjective responses were assessed. Performance decrements associated with vertical ride motion were found to depend strongly on reach direction and frequency.

Effects of Ride Motion on Reaction Times for Reaching Tasks

In future operational environments, the ability of Soldiers to quickly and accurately reach controls and displays, while they are in enclosed moving vehicles, is critical to the design of U.S. Army crew stations. This study examines degradations in the timing and accuracy of reaches associated with such enclosed and moving environments. Twenty participants completed several series of reaches to touch-screens. The results supported that the motion environment, touch-screen location, target size and appearance, and the number of target choices influenced reach timing and accuracy. These results illustrate the need to develop mitigation strategies for effective Soldier performance in future vehicle crew stations.

Redesigning Workstations Utilizing Motion Modification Algorithm

Workstation design is one of the most essential components of proactive ergonomics, and digital human models have gained increasing popularity in the analysis and design of current and future workstations (Chaffin 2001). Using digital human technology, it is possible to simulate interactions between humans and current or planned workstations, and conduct quantitative ergonomic analyses based on realistic human postures and motions. Motion capture has served as the primary means by which to acquire and visualize human motions in a digital environment. However, motion capture only provides motions for a specific person performing specific tasks. Albeit useful, at best this allows for the analysis of current or mocked-up workstations only. The ability to subsequently modify these motions is required to efficiently evaluate alternative design possibilities and thus improve design layouts. Utilizing the MemoryBased Motion Simulation (MBMS) algorithm (Park et al. 2002), movements of a lifting task were recorded by motion capture and then modified to create realistic movements for different scenarios: different statures of the subject and alternative workstation geometries. Based on the motion simulations, the current study suggested a preferred height of the workstation, which was determined by the motion that minimized the calculated low back compression force and joint-strength requirements. Also, the effect of human stature on the biomechanical stresses was evaluated.

A Biodynamic Model for the Assessment of Human Operator Performance under Vibration Environment

A combined biodynamic and vehicle model is used to assess the vibration and performance of a human operator performing driving and other tasks. The other tasks include reaching, pointing and tracking by the driver and/or passenger. This analysis requires the coordinated use of separate and mature software programs for anthropometrics, vehicle dynamics, biodynamics, and systems analysis. The total package is called AVB-DYN, an acronym for Anthropometries, Vehicle and Bio-DYNamics. The biodynamic component of AVB-DYN is described, and then compared with an experiment that studied human operator in-vehicle reaching performance using the U.S. Army TACOM Ride Motion Simulator.

Effects of ride motion on the speed and accuracy of in-vehicle pointing tasks

Terrain-induced vibration of a moving vehicle adversely affects the ability to quickly and accurately perform in-vehicle pointing tasks by altering the planned fingertip trajectory. The relationship between movement speed and accuracy is a result of the combined use of visual and somatosensory feedbacks which are used to discern movement deviations and make necessary compensatory movements. Participants (N=20) performed three-dimensional rapid pointing tasks under stationary and ride motion conditions to three touchpanel displays. Ride motion contributed to increased reaction and movement times and increased endpoint variability. Trajectory deviations were correlated to the principal direction of vehicle acceleration. Reaches orthogonal to the dominant vehicle acceleration exhibited larger endpoint variability, and reaches to the elevated touchpanel resulted in the largest variability across all motion conditions. Principal axes of endpoint ellipses were along the on-axis and off-axis directions of fingertip movement.