Six-degrees-of-freedom test rig design for simulation of mobile agricultural machinery vibrations

The growing importance of detrimental vibrations on mobile machinery, magnified by increasing working speed, emphasises the need to evolve from static to dynamic design of mechanical systems. Simulators are an indispensable tool to study present-day machinery dynamics in a repeatable way, under controlled laboratory conditions. The kinematic and dynamic aspects of a shaker design become more and more complex, as modern test rigs have an increased number of degrees of freedom and allow faster movements. In this paper, the design of a six-degrees-of-freedom test rig is worked out. With knowledge obtained from different studies of tractor vibrations in working conditions, test rig performance criteria (maximum load, amplitude and frequency), kinematic (actuator placement, choice of joints) and dynamic (resonance frequencies of structure, allowable stresses) are specified. The actuator placement is optimized. Both mechanical and hydraulic parts of the test rig are chosen and constructed according to the criteria. Performance measurements are executed. A frequency range from 1 Hz with an amplitude of 10 cm to 10 Hz with an amplitude of 1 mm can be excited as ultimate test rig performance criteria prescribe. (C) 2000 Silsoe Research Institute.