Apparatus and methods for control of a vehicle
View Patent ↗Method for controlling a vehicle that includes a support, at least one wheel, a platform coupled to the at least one wheel, a coupling structure having a support portion coupled to the support and a platform portion coupled to the platform that allows the support portion to move or slide fore and aft with respect to the platform portion, an actuator coupled to the coupling structure to control the position of the support portion relative to the platform portion, a drive coupled to the at least one wheel to deliver power to the at least one wheel to propel the vehicle and maintain the platform level, and a controller coupled to the drive to control the drive and coupled to the actuator to control the actuator.
1. A method for determining motor current capability for a battery powered vehicle, the method comprising:
estimating, via an estimation module, a sagged battery voltage for a vehicle battery during operation based on:
a) a predetermined maximum expected battery bus current of the vehicle battery during operation, wherein the expected battery bus current is a current to which the battery current rises due to the sagging of the battery voltage,
b) an estimated battery open-circuit voltage, and
c) an estimated battery open-circuit resistance;
wherein the sagged battery voltage is a voltage to which a DC bus of the vehicle battery sags at a maximum expected operating speed of the battery powered vehicle, and the estimated sagged battery voltage for a vehicle battery during operation is estimated in accordance with:
V bat — sag =V oc −I bat — max *R bat ,
where V bat — sag is the estimated sagged battery voltage, V oc is estimated battery open-circuit voltage, I bat — max is the predetermined maximum expected battery bus current, and R bat is the estimated battery open-circuit resistance, and
estimating, via the estimation module, motor current capability for the battery powered vehicle based on:
d) operational speed of a motor propelling the battery powered vehicle,
e) back EMF constant of the motor windings,
f) electrical resistance of the motor windings,
g) the estimated sagged battery voltage,
h) electrical inductance of the motor windings, and
i) magnetic pole pair count for the motor;
wherein the motor current capability for the battery powered vehicle is estimated in accordance with:
I
mot
_
max
(
Spd
)
=
2
3
*
-
K
e
*
Spd
*
R
mot
+
V
bat
_
sag
2
*
[
R
mot
2
+
(
PP
*
Spd
*
L
mot
)
2
]
-
(
K
e
*
Spd
2
*
PP
*
L
mot
)
2
R
mot
2
+
(
PP
*
Spd
*
L
mot
)
2
where I mot — max is the motor current capability, Spd is the operating speed of the motor, K e is the line-to-line back EMF constant of the motor windings, R mot is the line-to-line resistance of the motor windings, PP is the magnetic pole pair count for the motor, and L mot is the line-to-line inductance of the motor windings.
2. The method of claim 1 , comprising limiting the motor current capability (I mot — cap (Spd)) for the battery powered vehicle based on a current limit of a motor drive for driving the motor in accordance with:
I mot — cap ( Spd ) Minimum( I mot — lim ,I mot — max ( Spd ))
where I mot — lim is the current limit of the motor drive.
3. The method of claim 2 , comprising limiting the value of the operating speed of the motor used to a maximum no-load speed of the motor based on Vbat_sag in accordance with:
Spd
NoLoadEst
=
V
bat
_
sag
K
e
,
where Spd NoLoadEst is the maximum no-load speed.
4. An apparatus for determining motor current capability for a battery powered vehicle, the apparatus comprising:
a measurement module configured to:
measure operational speed of a motor used to propel the battery powered vehicle; and
an estimation module configured to:
estimate a sagged battery voltage for a vehicle battery during operation based on:
a) a predetermined maximum expected battery bus current, wherein the expected battery bus current is a current to which the battery current rises due to the sagging of the battery voltage,
b) an estimated battery open-circuit voltage,
c) an estimated battery open-circuit resistance;
wherein the sagged battery voltage is a voltage to which a DC bus of the vehicle battery sags at a maximum expected operating speed of the battery powered vehicle, and the estimated sagged battery voltage for a vehicle battery during operation is estimated in accordance with:
V bat — sag =V oc −I bat — max *R bat ,
where V bat — sag is the estimated sagged battery voltage, V oc is estimated battery open-circuit voltage, I bat — max is the predetermined maximum expected battery bus current, and R bat is the estimated battery open-circuit resistance, and
estimate motor current capability for the battery powered vehicle based on:
d) operational speed of a motor used to propel the battery powered vehicle,
e) back EMF constant of the motor windings,
f) electrical resistance of the motor windings,
g) the estimated sagged battery voltage,
h) electrical inductance of the motor windings, and
i) magnetic pole pair count for the motor;
wherein the motor current capability for the battery powered vehicle is estimated in accordance with:
I
mot
_
max
(
Spd
)
=
2
3
*
-
K
e
*
Spd
*
R
mot
+
V
bat
_
sag
2
*
[
R
mot
2
+
(
PP
*
Spd
*
L
mot
)
2
]
(
K
e
*
Spd
2
*
PP
*
L
mot
)
2
R
mot
2
+
(
PP
*
Spd
*
L
mot
)
2
where I mot — max is the motor current capability, Spd is the operating speed of the motor, K e is the line-to-line back EMF constant of the motor windings, R mot is the line-to-line resistance of the motor windings, PP is the magnetic pole pair count for the motor, and L mot is the line-to-line inductance of the motor windings.
5. The apparatus of claim 4 , wherein the estimation module is configured to limit the motor current capability for the battery powered vehicle based on a current limit of a motor drive for driving the motor in accordance with:
I mot — cap ( Spd )=min( I mot — lim ,I mot — max ( Spd ))
where I mot — lim is the current limit of the motor drive.
6. The apparatus of claim 5 , wherein the estimation module is configured to limit the value of the operating speed of the motor used to a maximum no-load speed of the motor based on V bat — sag in accordance with:
Spd
NoLoadEst
=
V
bat
_
sag
K
e
,
where Spd NoLoadEst is the maximum no-load speed.