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Development of a novel mechatronic system for mechanical weed ...

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Materials and methods<br />

54<br />

Figure 4.6 Typical change <strong>of</strong> the torque intensity <strong>for</strong> trapezoidal<br />

response <strong>of</strong> the speed (MA – acceleration torque, MF –<br />

friction torque, MD – deceleration torque, ∆u – change <strong>of</strong><br />

the rotational speed, ∆t – change in time)<br />

It is obvious that the acceleration torque can be calculated as a subtraction<br />

between the maximal torque value applied <strong>for</strong> acceleration and the friction<br />

torque. A possibility to graphically interpret the both torque values, the rotational<br />

speed change and change in the time (picking up any two points along the<br />

speed pr<strong>of</strong>ile) <strong>of</strong> the accelerating <strong>system</strong> based on the online measurement<br />

allows calculation <strong>of</strong> the load inertia using Equation (4.8). The actual<br />

acceleration <strong>of</strong> the motor α can be calculated as a quotient <strong>of</strong> the rotational<br />

speed change and change in the time, while the inertia <strong>of</strong> the motor JM is a<br />

characteristic provided by the manufacturer.<br />

SigmaWin is the accompanying s<strong>of</strong>tware <strong>of</strong> the servo drive which beside other<br />

acquisitioning possibilities provides tracing <strong>of</strong> the torque and speed. Tracing<br />

graphs <strong>of</strong> the acceleration to 750 rpm with torque limitation to 100 % <strong>of</strong> the<br />

nominal value are presented in Figure 4.7 and Figure 4.8. Figure 4.8 contains<br />

the zoom <strong>of</strong> the acceleration, making possible the measurement <strong>of</strong> the change<br />

in time while the <strong>system</strong> accelerate from 100 to 600 rpm. Vertical marker<br />

cursors can be adjusted to the points where the speed reaches the mentioned<br />

values and the s<strong>of</strong>tware automatically returns the time passed between these<br />

two points.

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