Apparatus for reducing belt slip
An apparatus for reducing belt slip of a vehicle, in which the vehicle includes an engine as a vibration source and an electric motor connected to the engine through a belt to transmit torque of the engine, includes: a signal generator configured to generate a reference signal with a frequency corresponding to vibration of the engine; an adaptive filter configured to calculate a filter coefficient to remove an error value between a rotational speed of the engine and a rotational speed of the electric motor and apply the filter coefficient to the reference signal to generate a reference torque signal; and a torque compensator configured to generate a belt slip compensation torque signal by changing an amplitude of the reference torque signal, and apply the belt slip compensation torque signal to determine a final torque command of the electric motor.
1. An apparatus for reducing belt slip of a vehicle, in which the vehicle includes an engine as a vibration source and an electric motor connected to the engine through a belt to transmit a torque of the engine, the apparatus comprising:
a signal generator configured to generate a reference signal with a frequency corresponding to vibration of the engine causing the belt slip;
an adaptive filter configured to:
calculate a filter coefficient to remove an error value between a rotational speed of the engine and a rotational speed of the electric motor, and
apply the calculated filter coefficient to the reference signal to generate a reference torque signal to drive the electric motor, and
a torque compensator configured to:
generate a belt slip compensation torque signal by changing an amplitude of the reference torque signal based on the torque of the engine, and
apply the belt slip compensation torque signal to determine a final torque command of the electric motor.
2. The apparatus of claim 1 , wherein the signal generator determines the reference signal based on a number of power strokes occurring within one rotational period of the engine, and a pulley ratio between a pulley coupled to a rotation shaft of the engine with the belt engaged the engine and a pulley coupled to a rotation shaft of the electric motor.
3. The apparatus of claim 2 , wherein the signal generator generates the reference signal using the following equation:
[ x ( k )=sin r 1 r 2 θ 1 ],
wherein θ 1 is a rotation angle of the engine, r 1 is the number of power strokes per one rotational period of the engine, and r 2 is the pulley ratio.
4. The apparatus of claim 1 , wherein the adaptive filter is further configured to:
calculate a filter coefficient to minimize an error value between an actual speed of the engine and an actual speed of the electric motor, and
filter the reference signal by applying the filter coefficient to generate the reference torque signal of the electric motor with a vibration occurrence frequency by the power strokes of the engine reflected to the electric motor.
5. The apparatus of claim 4 , wherein the adaptive filter calculates the filter coefficient to minimize the error value using a recursive least square (RLS) algorithm.
6. The apparatus of claim 4 , wherein the adaptive filter has a finite impulse response (FIR) format or an infinite impulse response (IIR) format.
7. The apparatus of claim 1 , wherein the torque compensator is further configured to:
change the amplitude of the reference torque signal by multiplying the reference torque signal of magnitude of 1 by a torque value corresponding to a magnitude of the torque of the engine to generate the belt slip compensation torque signal, and
add the belt slip compensation torque signal to a torque command of the electric motor received from a separate controller to generate the final torque command of the electric motor.
8. The apparatus of claim 7 , wherein the torque value corresponding to the magnitude of the output torque of the engine is an actual output torque of the engine, a value obtained by multiplying the actual output torque by a predetermined proportional coefficient, or a value obtained by multiplying a predetermined fixed engine torque by a predetermined proportional coefficient.
9. The apparatus of claim 1 , further comprising a phase compensator configured to compensate for a phase difference between an actual speed of the engine and the reference signal.
10. The apparatus of claim 9 , wherein the phase compensator:
calculates a speed of the electric motor by differentiating a rotation angle of the electric motor determined by applying a number of power strokes occurring within one rotational period of the engine, and a pulley ratio between a pulley coupled to a rotation shaft of the engine with the belt engaged with the engine and a pulley coupled to a rotation shaft of the electric motor to a rotation angle of the engine, and
calculates the phase difference based on the filter coefficient of the adaptive filter and the calculated speed of the electric motor to compensate the rotation angle of the electric motor for the phase difference.
11. The apparatus of claim 10 , wherein the rotation angle (θ 2 ) of the electric motor is calculated by the following equation:
θ 2 =r 1 r 2 θ 1 ,
wherein r 1 is the number of power strokes per one rotational period of the engine, and r 2 is the pulley ratio,
wherein the speed (ω 2 ) of electric motor is determined by differentiating the equation θ 2 =r 1 r 2 θ 1 , as in the following equation:
ω 2 =r 1 r 2 ω 1 ,
wherein ω 1 is the speed of the engine, and
wherein the phase difference (α) is determined by the following equation
α
=
∠
H
(
e
j
ω
T
s
)
=
tan
-
1
-
b
1
sin
(
ω
2
T
s
)
b
0
+
b
1
cos
(
ω
2
T
s
)
,
wherein b 0 , b 1 are filter coefficients of the adaptive filter and T s is a data acquisition time interval.