Rotational angle detecting device and electric power steering device using the same

A rotational angle detecting system, comprising:

• a rotational angle detecting device that is directly supplied with electric power from a battery;
• and
• a controller provided separately from the rotation angle detecting device and being connected to the battery through an ignition switch that switches power supply to the controller from the battery, wherein
• the rotational angle detecting device includes
• a sensor that detects a detection value that is variable according to a rotation of a detection object;
• a calculator that calculates a rotational information of the detection object based on the detection value detected by the sensor;
• a memory that stores power supply failure information indicating an occurrence of a power supply failure in which electric power is not supplied to the rotational angle detecting device from the battery;
• and
• a communication portion that outputs the rotational information to the controller,
• the memory is a volatile memory that, when the power supply failure occurs, sets the power supply failure information to an initial value indicating the occurrence of the power supply failure,
• the rotational angle detecting device is programmed to:
• determine whether the power supply failure information stored in the memory indicates the occurrence of a power supply failure,
• after determining that the power supply failure information stored in the memory indicates the occurrence of a power supply failure, output the power supply failure information to the controller and receive a notifying signal from the controller, and
• after receiving the notifying signal from the controller, set the supply failure information to a normal value indicating no occurrence of the power supply failure, and
• the controller is programmed to:
• receive the power supply failure information indicating the occurrence of a power supply failure from the rotational angle detecting device,
• after receiving the power supply failure information, detect a neutral position of the detection object, and
• after detecting the neutral position of the detecting object, output the notifying signal to the rotational angle detecting device.

A rotational angle detecting system, comprising:

• a rotational angle detecting device that is directly supplied with electric power from a battery;
• and
• a controller provided separately from the rotation angle detecting device and being connected to the battery through an ignition switch that switches power supply to the controller from the battery, wherein
• the rotational angle detecting device includes
• a sensor that detects a detection value that is variable according to a rotation of a detection object;
• a calculator that calculates a rotational information of the detection object based on the detection value detected by the sensor;
• a memory that stores power supply failure information indicating an occurrence of a power supply failure in which electric power is not supplied to the rotational angle detecting device from the battery;
• and
• a communication portion that outputs the rotational information to the controller,
• the memory is a volatile memory that, when the power supply failure occurs, sets the power supply failure information to an initial value indicating the occurrence of the power supply failure,
• the rotational angle detecting device is programmed to:
• upon the occurrence of a power supply failure, set the power supply failure information in the memory to the initial value indicating the occurrence of a power supply failure,
• after setting the power supply failure information in the memory indicating the occurrence of a power supply failure, output the power supply failure information to the controller and receive a notifying signal from the controller, and
• after receiving the notifying signal from the controller, set the supply failure information to a normal value indicating no occurrence of the power supply failure, and
• the controller is programmed to:
• receive the power supply failure information indicating the occurrence of a power supply failure from the rotational angle detecting device,
• after receiving the power supply failure information, detect a neutral position of the detection object, and
• after detecting the neutral position of the detecting object, output the notifying signal to the rotational angle detecting device.