Calculation Of Actual Rotation Speed; Calculation Of Target Rotation Speed - Renesas M16C/Tiny User Manual

In our program, when motor mode changes into turnon mode, TB1 interrupt is enabled, after the
next carrier wave cycle interrupt, motor woke mode become run mode. Every 50us, TB1
interrupts. If the TB1 interrupt request bit is set to 1, after another 50us, the TB1 interrupt request
bit is still set to 1, the zero-crossing of induced voltages is detected, and it is at the mid-point (30
electrical degrees) of each output pattern. Switching of the output pattern is delayed by 30
electrical degrees from zero-crossing detected. The process avoid occurring wrong pulses to be
mistaken the detection of zero-crossing of induced voltages because of motor demagnetization
at the point of output pattern switching. The U phase processing is shown as figure 3.1.2
When motor work mode changes into stop mode, tb1s is set to "0", TB1 interrupt stops but
interrupt enable is still open. The detection of induced voltage is shown as figure 3.1.1

2.3 Calculation of Actual Rotation Speed

The actual rotation speed is calculated by interval between two zero-crossings of induced
voltages. The interval comprises certain carrier wave cycle pulses. In the PWM mode, 6 intervals
are passed every 360 electrical degree. So if counting the carrier wave pulses every a rotate, the
actual rotation speed can be calculated by the following formula.
2π × 5kHz
Actual rotation speed= (3.3.1)
Zero − crossing interval × 6
In the actual programming, the method of lookup table can be used. Given an array of
zero-crossing interval pulses, the corresponding actual rotation speed can be calculated based
the above formula. A zero-crossing interval pulses is subtracted 13, the corresponding actual
rotation speed can be looked up using the sequence number of array.

2.4 Calculation of Target Rotation Speed

The target rotation speed is brought towards the current rotation speed command at a rate of 0.5
rad/s every certain interval until target rotation speed is approach to the rotation speed command.
If knowing current target rotation speed, the carrier wave cycle pulses between intervals of
zero-crossings can be calculated using the above formula.
RSBJEUM0001-0101 Rev. 1.01
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