Motor control device

1. A motor control device, comprising:

a motor rotation angle detector for outputting a motor rotation angle signal for detecting a rotation angle of a motor;

a calculator for carrying out control for the motor; and

a monitoring device for detecting a presence and absence of an abnormality of the calculator, wherein:

the calculator has two operation states;

one of the two operation states is a first operation state in which the calculator uses a first amount of current to calculate the rotation angle of the motor based on the motor rotation angle signal output from the motor rotation angle detector to control the motor based on the calculated rotation angle of the motor; and

another one of the two operation states is a second operation state in which the control for the motor is stopped, and the calculator uses a second amount of current less than the first amount of current to calculate the rotation angle of the motor based on the motor rotation angle signal output from the motor rotation angle detector.

2. A motor control device according to claim 1 , wherein:

the calculator comprises a main calculator and a sub calculator;

in the first operation state, the calculator calculates the rotation angle of the motor based on the motor rotation angle signal output from the motor rotation angle detector using the main calculator, and controls the motor based on the calculated rotation angle of the motor; and

in the second operation state, the calculator stops the operation of the main calculator, and calculates the rotation angle of the motor based on the motor rotation angle signal output from the motor rotation angle detector using the sub calculator;

the monitoring device is provided in the sub calculator; and

the sub calculator monitors a presence and absence of an abnormality of the main calculator using the monitoring device in the first operation state.

3. A motor control device according to claim 2 , wherein:

the monitoring device comprises a first monitoring device and a second monitoring device;

the first monitoring device is provided in the sub calculator;

the sub calculator monitors a presence and absence of an abnormality of the main calculator using the first monitoring device in the first operation state; and

the second monitoring device is provided outside the sub calculator, and monitors a presence and absence of an abnormality of the sub calculation device in the first operation state and the second operation state.

4. A motor control device according to claim 2 , further comprising:

a first power supply for supplying the main calculator and the sub calculator with electric power; and

a second power supply having current consumption smaller than that of the first power supply,

wherein the sub calculator is provided with electric power by the second power supply in the second operation state.

5. A motor control device according to claim 4 , wherein the first power supply supplies the main calculator and the sub calculator with electric power in the first operation state, and supplies the main calculator and the sub calculator with no electric power in the second operation state.

6. A motor control device according to claim 1 , further comprising:

a first power supply for supplying the calculator with electric power; and

a second power supply having current consumption smaller than that of the first power supply,

wherein the calculator is provided with electric power by the first power supply in the first operation state, and is provided with electric power by the second power supply in the second operation state.

7. A motor control device according to claim 1 , wherein:

the calculator calculates the rotation angle of the motor in a predetermined first calculation cycle in the first operation state, and calculates the rotation angle of the motor in a predetermined second calculation cycle in the second operation state; and

the predetermined second calculation cycle is longer than the predetermined first calculation cycle.

8. A motor control device according to claim 7 , wherein the predetermined second calculation cycle is shortened as a rotation speed of the motor increases.

9. A motor control device according to claim 7 , wherein the predetermined second calculation cycle is shortened as an induced voltage of the motor increases.

10. A motor control device according to claim 1 , wherein the motor rotation angle detector comprises a resolver, and an excitation signal applied to the resolver is a pulse signal.

11. A motor control device according to claim 10 , further comprising a sample-and-hold device for sampling and holding the motor rotation angle signal output from the resolver,

wherein the sample-and-hold device samples the motor rotation angle signal immediately after the pulse signal turns on, and holds the motor rotation angle signal immediately before the pulse signal turns off.

12. A motor control device according to claim 10 , wherein at least a part of the monitoring device, an excitation circuit for applying the excitation signal to the resolver, a receiver circuit for receiving the motor rotation angle signal from the resolver, the sample-and-hold device, and a motor rotation state detector for determining a rotation state of the motor based on an induced voltage of the motor constitute a single monolithic IC.

13. A motor control device according to claim 12 , wherein the motor rotation state detection detector includes an amplifier circuit for amplifying the induced voltage of the motor, sets a gain of the amplifier circuit by a resistance of a resistor connected to the single monolithic IC, and determines the rotation state of the motor by comparing an output voltage of the amplifier circuit and a predetermined threshold set in advance with each other.

14. A motor control device according to claim 1 , wherein:

the motor control device is installed on an electric power steering device; and

the electric power steering device calculates a steering angle from the rotation angle of the motor calculated by the motor control device.