5.1.3.2. Limitations of the analysis of acceleration

In the analysis conducted so far has not considered the characteristic of torque, the only consideration is that the engine provides the torque needed to move the load, and therefore the motor torque is equal to the load torque. Ie only have studied the resistive torque of the different types of cargo. The term TM (engine torque) is held constant to evaluate expressions, but this is a function of a variety of features. When considering the characteristic of the motor torque has to anticipate that it decreases with increasing frequency (ratio of steps), so that the acceleration at high speeds is limited by the decrease in motor torque and the increase the load torque due to inertia and friction.

Figure 5.5. Per pullout load and different profiles depending on the type of load.

Figure 5.5 shows the characteristic curve of torque and resistive torque of the load as a function of frequency. The intersection of both curves indicates the frequency ratio (steps) that can obtain maximum acceleration keeping. When applied to accelerate the system, the TL curve (f) suffers a shift in the pair equal to torque needed to accelerate the inertia J.

5.1.3.3. Need to optimize acceleration

When performing a linear acceleration the only consideration you have to realize is that the engine delivers the torque needed to pull the load. The limit is always at high speeds when the engine torque drops and the load increases. The intersection of both characteristics determines the speed limit for the acceleration. When the engine is in the area of low speeds and at full speed, the torque motor can deliver is higher than that required by the load, so this is wasted. If we look for an acceleration for each time, so that the required maximum torque motor that can deliver for each reason of steps, we optimize the acceleration curve, obtaining the maximum possible acceleration to move the load, resulting in few moves faster than using linear acceleration.