WCA September 2016

Otherwise by using ideal motors (very easy and simple in RecurDyn ® ) there would be the risk to obtain an imprecise answer. In fact, such an approach would generate unrealistic torque peaks in the simulated signals; motors

with unlimited torque simply do not exist. Figure 5 shows an example of motor laws.

Dynamic simulation and results A lot of dynamic simulations are run, and more than 60 cases are analysed, based on the possible different load cases preliminarily defined. Each dynamic simulation is composed of three phases: acceleration (from zero to the maximum speed), a steady state condition at the maximum speed, and the emergency braking (deceleration from maximum speed to zero in a few seconds). From the large volume of data collected it is possible to define all the information necessary for the design; in particular the maximum power required to the motors and the maximum torque and speed on each part. This data is fundamental for the right choice of motors and for a good structural design of the parts (rotor, cradles, joints, and so on). Figure 6 shows the results in terms of rotation speed and torque on each part of the transmission chain. Figure 7 shows a typical torque output on a gear. The peaks, clearly visible in the curve, are due to spools unbalance.

Vertical position

Deformation

Vertical position

Von Mises stress

Horizontal position

❍ ❍ Figure 8 : Load on cradles

Horizontal Force

Deformation

Horizontal position

Vertical Force

Von Mises stress

❍ ❍ Figure 9 : Cradle equivalent deformation and Von Mises stress Dynamic results as structural input As previously explained, the results obtained from the dynamic simulation are the input of the structural simulation.

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Wire & Cable ASIA – September/October 2016