Initial rotor position detection
Publication Date: 2005-Dec-02
The IP.com Prior Art Database
1. Initial rotor position detection
1.1 Description of algorithm
The initial rotor position detection is idea-based on the algorithm originally described in . ( Matsui, N. ). During the implementation work, this has been modified and the main differences from the original idea are described in the following. Also, an auto tuning procedure has been designed, who's purpose is to find the correct voltage pulse amplitude and duration in accordance with each motor's properties. Also, a main difference is that the method does not estimate the phase inductance, and does not require any motor data, except the nominal current of the machine.
For determining the alignment of the rotor, voltage pulses are fired for a very short period of time, in the three phases of the machine, in both positive and negative directions. In figure 1.1, the pilot voltage pulses are depicted, with blue, is the first sequence of pulses, and with red, the second sequence.
The current raises when a positive pulse is applied, and decreases to zero, during the negative pulse. Based on the phase currents measurements, the initial angle can be deducted.
The overall algorithm's flowchart, as it is implemented, is divided in three different stages. They are not stand-alone, except for the autotuning part, which is normally run only once. Flowcharts are presented in the following, for each stage.
Figure 1.1 Pilot voltage pulses applied to the three phases
The pilot voltage pulses can be seen in figure 1.2, as well as the voltage angle. The figure shows more accurate the way the pulses are applied.
Figure 1.2 Pilot voltage pulses and voltage angle
The phase currents and voltages are depicted in figure 1.3.
Figure 1.3 Pulses of phase voltages and currents
1.1.1 Auto tuning procedure
The autotuning procedure is run once at the beginning of the initial position algorithm. Figure 1.4 shows the voltage pulses and angle during autotuning.
Figure 1.4 Voltage pulses and voltage angle for auto tuning
Figure 1.5 Phase voltage pulses and currents for auto tuning
The autotuning voltage pulses are fired in the a phase. (see figure 1.4). The phase currents are sampled, and three different values are acquired, for each phase:
istart is the values of the corresponding phase current before the positive voltage pulse to be applied
itop is the value of the current after the positive pulse have been applied and right before the negative one to be applied
iend is the value of the current after the negative voltage pulse (see figure 1.5)
The delta values are calculated as follows:
[ ] [ ]
start top up
top end dn
where j is a dummy variable, symbolising phase name (a, b, c) or number (0, 1, 2 for the start, top and end values which in implementa...