Whole-body vibration (WBV) of mobile machines used in the steel making industry has not previously been quantified in six-degrees-of-freedom (6DOF). The purpose of this paper was to quantify 6DOF vibrations during the daily operating tasks of 5 commonly used mobile machines types used in the steel making and metal smelting industries. Vibration data were recorded from the chassis of five commonly used mobile machines using a MEMSense MAG3 triaxial accelerometer & gyroscope (MEMSense, SD, USA), and analyzed using custom MatlabTM code. Elevated values were observed at the chassis for crest factors, peak running root mean squared accelerations, and vibration total values, resulting in ISO 2631-1 (1997) comfort predictions ranging from Uncomfortable to Extremely Uncomfortable. Vibration dominant frequencies were generally between 1 and 8Hz. A second peak which occurred at approximately 27 Hz was observed for each vehicle in almost all axes. Occurring at a frequency that has the potential to produce negative health effects, this second peak was probably caused by the engine idling or running at low speeds. Field vibration profiles from this study have been used as inputs to a 6DOF robot for use in a corresponding laboratory study designed to optimize seat selection thus allowing the steel making and other similar industries to select operator seats based on industry specific field vibration characteristics.
Abstract. BACKGROUND: Heavy mobile equipment operation exposes operators to whole-body vibration (WBV) through the seat. The decision of which seat to retrofit a machine with is usually done statically. OBJECTIVE: To report on the third phase of a three phase project designed to intelligently retrofit seats in heavy mobile machines with the purpose of reducing machine operator WBV exposure. METHODS: Three slag pot haulers were retrofitted with a 6801 Isringhausen seat in which the seat pan cushion was retrofitted with Skydex TM seating material. Vibration dose values (weighted for health), vibration total values (weighted for comfort) and Seat Effective Amplitude Transmissibility were determined from field measurements. RESULTS: WBV was reduced from the first field study to below the upper boundary of the ISO 2631-1 (1997) health guidance caution zone and comfort weighted vibration total values were reduced to the second lowest discomfort rating. CONCLUSIONS: Steel making and other similar industries have been provided with information to more efficiently retrofit existing machines.
OBJECTIVE: The purpose of this work was to help a steel industry partner select the most appropriate of three high end heavy equipment seats to retrofit a number of their heavy mobile machines used in the steel making process. PARTICIPANTS: The participants included 8 males (22.3 ± 2.0 yrs.) and 8 females (23.5 ± 1.8 yrs.) with no experience operating heavy mobile equipment. METHODS: Previously recorded 6-DOF chassis acceleration data from a Pot Hauler (a machine which picks up and transports pots of slag) were used to extract six, 20 second representative profiles for implementation on a lab-based heavy machine simulator (6-DOF Parallel Robotics System Corporation robot). Subjects sat on three heavy equipment seats (BeGe7150, Grammar MSG 95G1721, and a 6801 Isringhausen with the seat pan cushion retrofitted with a Skydex TM cushion) mounted on the simulator. Each subject completed three trials for each combination of seat (n = 3) and vibration profile (n = 6). Chassis and operator/seat interface vibration were measured by 2, 6-DOF vibration transducers. Variables included Seat Effective Amplitude Transmissibility (SEAT) (X,Y,Z,Roll,Pitch,Yaw,6DOF Vector Sum) to determine if the seat was attenuating or amplifying the vibration, 6-degree of freedom (DOF) vibration total value weighted predicted comfort (Avc) (according to ISO 2631-1) and operator reported comfort (ORC). RESULTS: Factorial ANOVAs revealed significant differences (p 0.05) between seats for all SEAT variables but different seats performed better than others depending on the axis. Significant differences between males and females were observed for SEAT in X,Y, and Pitch as well as for Avc. As expected there were significant differences between vibration profiles for all assessed variables. A number of interaction effects were observed, the most frequently occurring of which was between seat and vibration profile. CONCLUSIONS: Based upon the number of seat and vibration profile interactions, results suggest that a single seat is not suited for all tested conditions. However, SEAT values for all of the seats tested were extremely low (e.g., 6-DOF SEAT < 30%) indicating that all of the seats were capable of providing good vibration attenuation.
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