Control device, electric power steering device, and drive device
A control device includes a model following controller in which a transfer function of a control target is restricted to a transfer function of a nominal model in a frequency band in which a complementary sensitivity gain, which is a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the control target and the nominal model, is approximately one. A steady gain of the complementary sensitivity function is about 0.1 or more. A lower limit value of a frequency band in which the complementary sensitivity gain is about one is higher than a first resonance frequency that is a resonance frequency of a yaw rate of a vehicle. A second resonance frequency is higher than the first resonance frequency and lower than a lower limit value of a frequency band in which the complementary sensitivity gain is about one.
1 . A control device to control, as a control target, a portion in a steering mechanism that includes an input shaft to which a steering wheel steered by a steering operator is coupled, an output shaft coupled to the input shaft via a torsion bar, and a motor coupled to the output shaft and that is mounted on a vehicle, the portion including at least the motor, the control device comprising:
a model following controller configured or programmed to generate a correction torque to correct an input torque input to the control target based on output of the control target and a nominal model based on a configuration of the control target; wherein
the model following controller is configured or programmed such that a transfer function of the control target is restricted to a transfer function of the nominal model in a frequency band in which a complementary sensitivity gain, which is a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the control target and the nominal model, is approximately one;
a steady gain of the complementary sensitivity function is about 0.1 or more;
a lower limit value of a frequency band in which the complementary sensitivity gain is about one is higher than a first resonance frequency that is a resonance frequency of a yaw rate of the vehicle;
a second resonance frequency that is a resonance frequency of the steering mechanism is higher than the first resonance frequency and lower than a lower limit value of a frequency band in which the complementary sensitivity gain is about one;
the complementary sensitivity gain at the second resonance frequency is higher than the complementary sensitivity gain at the first resonance frequency, and is about 0.5 or more and less than about 1;
the control target is defined by a two-inertia system which includes the steering mechanism; and
the steering mechanism is driven with the corrected input torque generated by the model following controller.
2 . The control device according to claim 1 , further comprising:
a base assist controller configured or programmed to generate an assist torque to compensate for at least a portion of a self-aligning torque generated in a tire of the vehicle based on a torsion bar torque generated in the torsion bar; wherein
when a spring constant of the torsion bar is Ktor, an inclination of a self-aligning torque generated in a tire of the vehicle with respect to a steering angle that is a rotation angle of the output shaft is KSAT, an inclination of the assist torque with respect to the torsion bar torque is Kass, the steady gain is T(0), and a ratio of the correction torque to disturbance input to the control target is m, a following formula is satisfied:
T
(
0
)
=
K
tor
+
K
ass
+
mK
SAT
K
tor
+
K
ass
+
K
SAT
.
3 . The control device according to claim 1 , wherein control of returning an angle of the steering wheel to a predetermined reference angle is executable by using the control device.
4 . The control device according to claim 1 , wherein
the steady gain is about 0.3 or more; and
the complementary sensitivity gain at the second resonance frequency is about 0.8 or more.
5 . The control device according to claim 1 , wherein a lower limit value of a frequency band in which the complementary sensitivity gain is about one is lower than about 10 Hz.
6 . The control device according to claim 1 , wherein the complementary sensitivity function is a function including a transfer function of a low-pass filter and a transfer function of a phase advance compensator.
7 . The control device according to claim 1 , wherein the complementary sensitivity function is a function including a transfer function of a low-pass filter and a transfer function of a high-pass filter.
8 . An electric power steering device comprising:
the control device according to claim 1 ; and
the steering mechanism.
9 . A control device to control a control target including a motor in a drive device to rotate a drive shaft to which a tire of a vehicle is coupled, the control device comprising:
a model following controller configured or programmed to generate a correction torque to correct an input torque input to the control target based on output of the control target and a nominal model based on a configuration of the control target; wherein
the model following controller is configured or programmed such that a transfer function of the control target is restricted to a transfer function of the nominal model in a frequency band in which a complementary sensitivity gain, which is a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the control target and the nominal model, is approximately one;
a steady gain of the complementary sensitivity function is about 0.1 or more;
a lower limit value of a frequency band in which the complementary sensitivity gain is about one is higher than a first resonance frequency that is a resonance frequency of the drive device;
a second resonance frequency that is a resonance frequency of a drive mechanism including the tire, the drive shaft, and the drive device is higher than the first resonance frequency and lower than a lower limit value of a frequency band in which the complementary sensitivity gain is about one;
the complementary sensitivity gain at the second resonance frequency is higher than the complementary sensitivity gain at the first resonance frequency, and is about 0.5 or more and less than about 1;
the control target is defined by a two-inertia system which includes the motor; and
the motor is driven with a corrected input torque in accordance with the correction torque generated by the model following controller.
10 . A drive device comprising:
the control device according to claim 9 ;
the motor; and
a gear mechanism connected to the motor.