1. A high voltage sensing circuit, with temperature compensation, for an x-ray source, comprising:
a. high voltage sensing resistors comprising:
i. a first resistor having a first resistance (R1), a second resistor having a second resistance (R2), a third resistor having a third resistance (R3), and a fourth resistor having a fourth resistance (R4);
ii. a first series comprising the first resistor and the second resistor electrically connected in series, the connection between the first resistor and the second resistor called a first connection, and having one end of the first series configured to be electrically connected to a cathode of the x-ray source and another end of the first series configured to be electrically connected to an anode of the x-ray source;
iii. a second series comprising the third resistor and the fourth resistor electrically connected in series, the connection between the third resistor and the fourth resistor called a second connection;
iv. the first series and the second series electrically connected in parallel;
v. the first series comprising a first resistive material that has a first temperature coefficient of resistance, the second series comprising a second resistive material that has a second temperature coefficient of resistance, and the first temperature coefficient of resistance is different from the second temperature coefficient of resistance; and
b. a voltage measurement circuit configured to calculate a total voltage (VT) between the cathode and the anode of the x-ray source by:
i. determining a voltage differential across the first resistor, called a first voltage (V1);
ii. determining a voltage between the first connection and the second connection, called a differential voltage (Vd); and
iii. using the first voltage and the differential voltage to calculate the total voltage.
2. The high voltage sensing circuit of claim 1, wherein the total voltage VT is calculated by:
V
T
=
V
\u2062
\u2062
1
*
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
+
k
*
V
d
in which k is a factor used to compensate for temperature differentials between the first and second resistors.
3. The high voltage sensing circuit of claim 2, wherein the factor k is determined by recording voltages VT, V1, and Vd at different temperature differentials between the first and second resistors and by the equation:
V
T
=
V
\u2062
\u2062
1
*
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
+
k
*
V
d
.
4. The high voltage sensing circuit of claim 1, wherein the resistances and temperature coefficients of resistance of the resistors are selected such that:
a.
\uf603
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
–
R
\u2062
\u2062
3
+
R
\u2062
\u2062
4
R
\u2062
\u2062
3
\uf604
=
X
when there is no temperature differential between one end of the first series and an opposing end of the first series;
b.
\uf603
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
–
R
\u2062
\u2062
3
+
R
\u2062
\u2062
4
R
\u2062
\u2062
3
\uf604
=
Y
when there is 1 degree Celsius temperature differential between one end of the first series and an opposing end of the first series; and
c. |X\u2212Y|>0.00000025.
5. The high voltage sensing circuit of claim 1, wherein the resistances and temperature coefficients of resistance of the resistors are selected such that:
a.
\uf603
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
–
R
\u2062
\u2062
3
+
R
\u2062
\u2062
4
R
\u2062
\u2062
3
\uf604
=
X
when there is no temperature differential between one end of the first series and an opposing end of the first series;
b.
\uf603
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
–
R
\u2062
\u2062
3
+
R
\u2062
\u2062
4
R
\u2062
\u2062
3
\uf604
=
Y
when there is 1 degree Celsius temperature differential between one end of the first series and an opposing end of the first series; and
c. |X\u2212Y|>0.000003.
6. The high voltage sensing circuit of claim 1, wherein the resistances and temperature coefficients of resistance of the resistors are selected such that:
a.
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
=
R
\u2062
\u2062
3
+
R
\u2062
\u2062
4
R
\u2062
\u2062
3
when there is substantially no temperature differential between one end of the first series and an opposing end of the first series; and
b.
\uf603
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
–
R
\u2062
\u2062
3
+
R
\u2062
\u2062
4
R
\u2062
\u2062
3
\uf604
>
0
when there is a temperature differential between one end of the first series and an opposing end of the first series.
7. The high voltage sensing circuit of claim 1, wherein the voltage measurement circuit calculates the total voltage with improved accuracy by including a temperature compensation factor based on the differential voltage.
8. The high voltage sensing circuit of claim 1, wherein the voltage measurement circuit is configured to calculate a total voltage of at least 4000 volts.
9. The high voltage sensing circuit of claim 1, wherein R2 minus R1 is greater than 1000 ohms.
10. The high voltage sensing circuit of claim 1, wherein R2 divided by R1 is greater than 500.
11. The high voltage sensing circuit of claim 1, wherein R2 is at least 10 mega ohms.
12. The high voltage sensing circuit of claim 1, wherein R2 is at least 1 giga ohm.
13. The high voltage sensing circuit of claim 1, wherein R2 is at least 10 giga ohms.
14. The high voltage sensing circuit of claim 1, wherein a larger of the first or second temperature coefficient of resistance divided by a smaller of the first or second temperature coefficient of resistance has an absolute value that is greater than 10.
15. The high voltage sensing circuit of claim 1, wherein a larger of the first or second temperature coefficient of resistance divided by a smaller of the first or second temperature coefficient of resistance has an absolute value that is greater than 1.3.
16. The high voltage sensing circuit of claim 1, wherein at least one of the high voltage sensing resistors is disposed on an x-ray tube of the x-ray source.
17. A high voltage sensing circuit with temperature compensation comprising:
a. high voltage sensing resistors comprising:
i. a first resistor having a first resistance (R1), a second resistor having a second resistance (R2), a third resistor having a third resistance (R3), and a fourth resistor having a fourth resistance (R4);
ii. a first series comprising the first resistor and the second resistor electrically connected in series, the connection between the first resistor and the second resistor called a first connection, and having one end of the first series configured to be electrically connected to a high voltage and another end configured to be electrically connected to a low voltage;
iii. a second series comprising the third resistor and the fourth resistor electrically connected in series, the connection between the third resistor and the fourth resistor called a second connection;
iv. the first series and the second series electrically connected in parallel;
v. the first series comprising a first resistive material that has a first temperature coefficient of resistance, the second series comprising a second resistive material that has a second temperature coefficient of resistance, and the first temperature coefficient of resistance is different from the second temperature coefficient of resistance; and
b. a voltage measurement circuit configured to calculate a total voltage (VT) of at least 1000 volts between the high voltage and the low voltage by:
i. determining a voltage differential across the first resistor, called a first voltage (V1);
ii. determining a voltage between the first connection and the second connection, called a differential voltage (Vd); and
iii. using the first voltage V1 and the differential voltage Vd to calculate the total voltage.
18. The high voltage sensing circuit of claim 17, wherein the voltage between the high voltage and the low voltage is calculated by:
V
T
=
V
\u2062
\u2062
1
*
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
+
k
*
V
d
in which k is a factor used to compensate for temperature differentials between the first and second resistors.
19. An x-ray source, comprising:
a. an x-ray tube having a cathode and an anode attached to the tube, the cathode and the anode separated from each other by electrically insulative material;
b. high voltage sensing resistors comprising:
i. a first resistor having a first resistance (R1), a second resistor having a second resistance (R2), a third resistor having a third resistance (R3), and a fourth resistor having a fourth resistance (R4);
ii. a first series comprising the first resistor and the second resistor electrically connected in series, the connection between the first resistor and the second resistor called a first connection, one end of the first series electrically connected to the cathode and another end electrically connected to the anode, R2 is at least 1 mega ohm, and R2 divided by R1 is greater than 100;
iii. a second series comprising the third resistor and the fourth resistor electrically connected in series, the connection between the third resistor and the fourth resistor called a second connection;
iv. the first series and the second series electrically connected in parallel;
v. the first series comprising a first resistive material that has a first temperature coefficient of resistance, the second series comprising a second resistive material that has a second temperature coefficient of resistance, and the first temperature coefficient of resistance is different from the second temperature coefficient of resistance; and
c. a voltage measurement circuit configured to determine a total voltage (VT), of at least 4000 volts, between the cathode and the anode by:
i. determining a voltage differential across the first resistor, called a first voltage (V1);
ii. determining a voltage between the first connection and the second connection, called a differential voltage (Vd); and
iii. using the first voltage V1 and the differential voltage Vd to determine the total voltage VT by using the relationship:
V
T
=
V
\u2062
\u2062
1
*
R
\u2062
\u2062
1
+
R
\u2062
\u2062
2
R
\u2062
\u2062
1
+
k
*
V
d
in which k is a factor used to compensate for temperature differentials between the first and second resistors.
20. The high voltage sensing circuit of claim 19, wherein a larger of the first or second temperature coefficient of resistance divided by a smaller of the first or second temperature coefficient of resistance has an absolute value that is greater than 10.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for performing a parking assist control for automatically guiding a vehicle to a target parking position, comprising:
calculating a first change of a vehicle direction based on output of a speed sensor and a steering angle obtained by a steering angle sensor;
calculating a second change of the vehicle direction based on a yaw rate obtained by a yaw rate sensor;
comparing the first change of the vehicle direction and the second change of the vehicle direction; and
determining whether or not the parking assist control is required to be stopped based on a result of a comparison between the first and second calculated changes of the vehicle direction.
2. A method for performing a parking assist control according to claim 1, wherein the calculation of the first change of the vehicle direction and the calculation of the second change of the vehicle direction are performed at the same time.
3. A parking assist apparatus for performing a parking assist control for automatically guiding a vehicle to a target parking position, comprising:
a traveling distance calculating means for calculating a traveling distance of a vehicle during an implementation of the parking assist control;
a first calculating means for calculating a first change of a vehicle direction occurring within the traveling distance based on output of a speed sensor and output of a steering angle sensor;
a second calculating means for calculating a second change of the vehicle direction occurring within the traveling distance based on a yaw rate obtained by a raw rate sensor; and
a determining means for comparing calculated results obtained by the first calculating means and the second calculated means and determining that the parking assist control is to be stopped when a difference between the first change of the vehicle direction and the second chance of the vehicle direction is greater than a predetermined value.
4. A vehicle assist apparatus according to claim 3, wherein the determining means compares the calculated results of the first calculating means and the second calculated means which are calculated at the same time.
5. A parking assist apparatus according to claim 3, wherein the second calculating means calculates a deflection angle \u03b8 y based on the yaw rate sensor.
6. A parking assist apparatus according to claim 3, wherein
the first calculating means calculates a deflection angle \u03b8 h based on the speed sensor and the steering angle sensor.
7. A parking assist apparatus according to claim 3, wherein
the second calculating means calculates a deflection angle \u03b8 y based on the yaw rate sensor.
8. A parking assist apparatus according to claim 3, wherein
the determining means determines that one of the yaw rate sensor and the steering angle sensor is fault when a difference between the deflection angles \u03b8 h and \u03b8 y is greater than the predetermined value.
9. A parking assist apparatus for performing a parking assist control for guiding a vehicle to a target parking position, comprising:
a first calculating means for calculating a first change of a vehicle direction based on output of a speed sensor and output of a steering angle sensor;
a second calculating means for calculating a second change of the vehicle direction based on output obtained by a raw rate sensor; and
a determining means for comparing calculated results obtained by the first calculating means and the second calculated means and determining that the parking assist control is to be stopped based on a result of a comparison between the calculated results when a difference between the first change of the vehicle direction and the second chanae of the vehicle direction is greater than a predetermined value.
10. A parking assist apparatus according to claim 9, wherein the first calculating means calculates a deflection angle \u03b8 h based on the output of the speed sensor and the steering angle sensor.
11. A parking assist apparatus according to claim 10, wherein the second calculating means calculates a deflection angle \u03b8 y based on the output of the yaw rate sensor.
12. A parking assist apparatus according to claim 11, wherein the determining means determines that one of the yaw rate sensor and the steering angle sensor is fault when a difference between the deflection angles \u03b8 h and \u03b8 y is greater than the predetermined value.
13. A method for performing a parking assist control according to claim 1, further comprising determining that the parking assist control is required to be stopped when a difference between the first change of the vehicle direction and the second change of the vehicle direction is greater than a predetermined value.