User's Manual

HARSFEN0602
full electrical cycles possible for that motor. Enter the "encoder counts in revolution"
CA[18] parameter as the number of encoder counts for CA[19] electrical cycles.
The encoder parameters are listed in the following table.
CA[18] Encoder bits per revolution, after resolution multiplication by 4, in the range
[24..10,000,000]. For an incremental encoder with 1000 lines, CA[18] will be 4000
CA[19] Number of motor pole pairs [1..50].
CA[23] Counts per meter (any positive integer)
0: Rotary motor
1: Counts per meter in a linear motor.
This parameter is not used directly by the amplifier – it is just stored there for the
convenience of a host
9.4 Commutation search
9.4.1 General
When starting the motor, the rotor can be anywhere.
The torque of a brushless DC motor is given by the equation
)sin(IKT
T
θ⋅⋅=
(1)
rs
θ−θ=θ
(2)
where
T Motor torque
T
K
Motor constant
I Motor current
The electrical angle between the rotor and the field at the stator
s
θ
The electrical angle of the stator field
r
θ
The electrical angle of the rotor
The angle
s
θ is known, since the amplifier controls it directly.
The angle
r
θ is unknown.
If we rotate
s
θ , i.e. tf2
s
⋅π−θ where f is some frequency and t is the time, we get the sinusoidal torque
)tf2sin(IKT
rT
θ−⋅π⋅⋅=
(3)
For that torque, the motor shaft will move according to
))f(tf2sin(IK)f(A)t(P
rT
φ−θ−⋅π⋅⋅⋅= , where
P(t) Motor shaft position
)f(j
e)f(A
Transfer function of the motor and its load at the frequency f.
By applying the torque of (3) and measuring the position, we can identify both A(f) and
r
θ .
9.4.2 Selecting the parameters
The parameters I and f can be selected from the range specified below:
I The torque is selected by the parameter CA[26].
CA[26] defines I as a percentage of the continuous current rating CL[1].
For example, if CA[26]=50, then I=0.5 CL[1].
f CA[15] controls the frequency of the sinusoidal motor torque .
The basic frequency (with CA[15]=0) is so that a cycle is completed in 128 * TS
microseconds. For a Harmonica with TS=50, this will be a cycle of 6400