6.8.1.2 Test signal generator
The test signal generator is required in order to ensure that the Kalman filter will be
able to estimate position and speed information even at low speeds (all the way to a
stop). There are various signals available for this purpose.
The forms available are a sinusoidal signal and a 32-bit PRBS signal. The
frequencies can be freely selected within a range of 100 Hz to 1000 Hz. In addition,
there is the option of subjecting the d or q axis to the signals either individually (in an
additive manner) or in combination (in a multiplicative manner).
P 792[0] - Signal: 0 = No measuring signal; 1 = Addition; 2 = Multiplication
When using the additive solution, each signal will have its own amplitude. In
contrast, when using the combination solution, only the amplitude value of the
sinusoidal signal will be used.
In addition, scaling for the test signal amplitudes has been implemented. This
ensures that the signal can be applied gradually over a specified speed range. The
speed ranges in which the test signal will be applied fully (P 792[7] - Full signal
range) and in which it will increase (P 792[8] - Increasing signal range) can be
defined as necessary.
MOOG
ID No.: CB40859-001 Date: 11/2020
MSD Servo Drive - Device Help
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6 Encoder
Image 6.7: Test signal generators
The following is recommended as a good test signal: A sinusoidal signal with a
current amplitude of approx. 10% of the rated current on the d axis with a frequency
of approx. 400 Hz. (P 792[0] = 1; P 792[1] = 400; P 792[2] = 10% Irated)
In the case of problematic motors, it can be useful to inject an additive d current. This
current can be configured to be dependent on the speed (P 792[9] - d current offset)
or load (796). The following two diagrams use examples to illustrate the influence
that the ramp parameters have on the additive d components. Please note, however,
that this current will also increase motor losses, meaning it should only be used in
exceptional cases.
