CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119(a) to Korean Patent Application No. 10-2019-0107190 filed on Aug. 30, 2019 in the Korean Intellectual Property Office, which is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

Embodiments of the present disclosure relate to an apparatus and method for controlling a motor-driven power steering (MDPS) apparatus, and more particularly, to an apparatus and method for controlling an MDPS apparatus, which enable an autonomous vehicle to make a mode transition without a sense of difference and can improve noise robustness against a command steering angle for autonomous driving by more clearly determining whether a driver intervenes in steering, when a mode of the autonomous vehicle switches from an autonomous driving mode to a manual mode and adjusting a transition speed based on an autonomous driving situation.

2. Related Art

With the recent development of the automobile technology, it is expected that autonomous vehicles capable of autonomous driving without a manipulation of a driver will be rapidly supplied. Such an autonomous vehicle refers to a vehicle capable of autonomous driving by controlling various sensors and a control system in an artificial intelligence way.

Furthermore, the autonomous vehicle can prevent an accident attributable to a driver's careless mistake or driving of an aggressive form, and has an advantage in that even unlicensed drivers, the blind, and minors can freely use the autonomous vehicle. In particular, a lot of research is carried out on the safety of the autonomous vehicle. For example, if a mode of the autonomous vehicle switches (or transitions) from an autonomous driving mode to a manual mode in which a driver directly manipulates the autonomous vehicle, research related to a technology for safely assigning, to a driver, the rights to control the vehicle is carried a lot.

However, there is insufficient research related to the field for maintaining stability (e.g., if stability is low, anxiety or distrust about autonomous driving may occur) provided to a driver while an autonomous vehicle travels in the autonomous driving mode.

For example, when the traveling speed of an autonomous vehicle changes (e.g., when the traveling speed changes from a low speed to a high speed or from a high speed to a low speed) during an autonomous driving mode operation, there is a problem in that a sense of difference may occur when an operation mode for control of MDPS (or an MDPS control mode) switches.

For example, if the traveling speed of an autonomous vehicle changes from a low speed to a high speed (or from a high speed to a low speed), an operation mode for MDPS control also changes from a location control mode to a torque control mode (or from the torque control mode to the location control mode). There is a problem in that an output difference occurs in an intermediate process in which an operation mode for control of an MDPS apparatus is changed as described.

If an output difference occurs in an intermediate process in which an operation mode for control of an MDPS apparatus is changed as described, there is a problem in that a passenger feels uneasy (i.e., stability is reduced).

Accordingly, there is a need for a method for preventing unwanted mode transition in addition to such a problem and enabling smooth mode transition based on an autonomous driving situation by more precisely detecting whether a driver intervenes in steering.

The related art of the disclosure is disclosed in Korean Patent No. 10-1779823 (Sep. 13, 2017, entitled “METHOD FOR SWITCHING THE CONTROL MODE IN AUTONOMOUS VEHICLE AND APPARATUS THEREOF”).

SUMMARY

Various embodiments are directed to the provision of an apparatus and method for controlling an MDPS apparatus, which enable an autonomous vehicle to make a mode transition without a sense of difference and can improve noise robustness against a command steering angle in an autonomous driving mode by more clearly determining whether a driver intervenes in steering, when a mode of the autonomous vehicle switches from the autonomous driving mode to a manual mode and adjusting a transition speed based on an autonomous driving situation.

In an embodiment, an apparatus for controlling a motor-driven power steering (MDPS) apparatus includes a driving information input unit configured to receive driving information generated while a vehicle travels, a steering angle location control unit configured to receive a command steering angle for autonomous driving and a current motor steering angle of a driving motor and to output an autonomous driving command through location control, and an MDPS control unit configured to drive the driving motor based on the autonomous driving command received from the steering angle location control unit in an autonomous driving mode, determine whether a driver intervenes in steering, based on the driving information received from the driving information input unit during the autonomous driving, compute a driver command according to the driver' steering based on a result of the determination on whether the driver intervenes in steering, compute a compensation output between the autonomous driving command and the driver command by applying a weighting according to a steering angular speed, and make a mode transition from the autonomous driving mode to a driver mode while driving the driving motor.

In an embodiment, the driving information input unit may receive any one or more of a vehicle speed, the motor steering angle of the driving motor, and a steering angle, steering angular speed and column torque according to the driver' steering, while the vehicle travels.

In an embodiment, the steering angle location control unit may receive error values of the command steering angle and motor steering angle and filter out the error values through a variable high-pass filter for varying a cutoff frequency based on a command steering angular speed, adjust a location control gain, and output the autonomous driving command.

In an embodiment, the steering angle location control unit may lower the cutoff frequency when the command steering angular speed is high and raise the cutoff frequency when the command steering angular speed is low.

In an embodiment, the MDPS control unit may include a steering controller configured to compute the driver command according to the driver' steering based on a vehicle speed, steering angle and column torque received from the driving information input unit, a steering intervention determination unit configured to receive the steering angle, the motor steering angle and the column torque and to determine whether the driver intervenes in steering, based on a result of a comparison between retention times of the column torques and phases of the steering angle and motor steering angle, a weighting calculator configured to determine a blending cycle and weighting for compensating for the autonomous driving command and the driver command based on the steering angular speed when an operation mode switches, and an output controller configured to compute the compensation output in such a way as to compensate for the autonomous driving command and the driver command by applying the weighting based on the blending cycle determined by the weighting calculator if the steering intervention determination unit determines that the driver has intervened in steering and to output the compensation output.

In an embodiment, the steering intervention determination unit may determine that the driver has intervened in steering if the column torque is maintained to a set torque or more for a set time or more and the phase of the steering angle is faster as a result of a comparison between the phases of the steering angle and the motor steering angle.

In an embodiment, the output controller may compute the compensation output using an equation [(1−weighting)*autonomous driving command+weighting*driver command] while increasing the weighting from 0 to 1 based on the blending cycle.

In an embodiment, a method of controlling a motor-driven power steering (MDPS) apparatus includes receiving, by an MDPS control unit, an autonomous driving command from a steering angle location control unit and driving a driving motor in an autonomous driving mode, determining, by the MDPS control unit, whether a driver intervenes in steering, based on driving information received from a driving information input unit during autonomous driving, computing, by the MDPS control unit, a driver command according to the driver' steering if it is determined that the driver has intervened in steering, computing, by the MDPS control unit, a compensation output between the autonomous driving command and the driver command by applying weighting according to a steering angular speed, and making a mode transition, by the MDPS control unit, from the autonomous driving mode to a driver mode while driving the driving motor using the compensation output.

In an embodiment, the determining of whether the driver intervenes in steering may include receiving, by the MDPS control unit, a steering angle, a motor steering angle and a column torque, and determining that the driver has intervened in steering if the column torque is maintained to a set torque or more for a set time or more and a phase of the steering angle is faster as a result of a comparison between the phases of the steering angle and the motor steering angle.

In an embodiment, the computing of the compensation output may include determining, by the MDPS control unit, a blending cycle and weighting for compensating for the autonomous driving command and the driver command based on the steering angular speed, and computing, by the MDPS control unit, the compensation output in such a way as to compensating for the autonomous driving command and the driver command by applying the weighting based on the determined blending cycle.

In an embodiment, the computing of the compensation output may include computing, by the MDPS control unit, the compensation output using an equation [(1−weighting)*autonomous driving command+weighting*driver command] while increasing the weighting from 0 to 1 based on the blending cycle.

In an embodiment, the method may further include receiving, by the steering angle location control unit, error values of the command steering angle and motor steering angle and filtering out the error values through a variable high-pass filter for varying a cutoff frequency based on a command steering angular speed, adjusting a location control gain, and outputting the autonomous driving command to the MDPS control unit.

In an embodiment, when varying the cutoff frequency, the steering angle location control unit may lower the cutoff frequency when the command steering angular speed is high and raise the cutoff frequency when the command steering angular speed is low.

