| 5th November 2001
Machinery Cab Stabilization
Using damping Developed by VTT
Bouncing and vibration in machinery cabs reduce the drivers comfort and cause back complaints. The active damping developed by VTT reduces vibration in moving machinery, thus reducing the health risks to the driver. The need for damping is predicted by G-sensors installed in the machinery.
In many situations, the exposure of the driver to long-term, repeated vibration causes health and safety risks. Cabs that vibrate less than at present are required to give drivers better working conditions, making working comfort a new competitive advantage for machiner manufacturers.
Typically an increase in the level of vibration leads to a slowing down in working or drive speed. Vibration can also become so intense that it becomes difficult for the driver to control the vehicle, which can even lead to a risk of accidents.
The benefits of the active damping developed by VTT include improved driving comfort, longer periods of continuous work over difficult ground, and the possibility to use higher drive and working speeds.
Active damping brings new push-pull forces to each vibration at the desire attachment points. In active damping, vibration is measured using acceleration, force, and tilt sensors, the counter movements being formed using hydraulic cylinders, which control the attachements between the wheels and the machines chassis, and the chassis and the cab, or the cab and the drivers seat.
The elimination of bounce and vibration has already been implemented in forestry machinery using wheel-specific hydraulic cylinders in the machine. Seat stabilization has been tested in mining machinery and cab stabilization in agricultural tractors. Tractor vibration has been tested under difficult conditions, for example, driving at right-angles over the furrows of a ploughed field in winter.
The elimination of cab bounce is diffcult, because the large mass demands large counter forces while it is difficult to implement the controllable suspension mechanisms. In cabs, even a 50 % reduction in bounce will significantly improve driving comfort.
Lateral bounce in cabs is the most detrimental to the human body. This and, for example, vertical bounce arises in machinery in the frequency range 1 10 Hz. Work protection regulations set clear limits for this kind of bounce. At present, the cost of eliminating bounce account for 5 - 10 % of the price of a machine, but systematic work in bounce control will reduce the proportion of the cost.
Generally, active dampoing can be used to eliminate nearly all externally caused vibrations in any small mechanical structure.
|Feel free to use all news. Photographs copyright Kalle Heiska.|
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