Vehicle automatic control
A vehicle autosteering system having a controller determines steering commands based on GNSS receiver position data, inertial measurement system data, and steering shaft rotation encoder data. The controller outputs a signal to drive an electric motor that rotates the vehicles steering shaft, changing the steering angle and guiding the vehicle along a predefined path e.g., a straight line.
1 . A method for steering a vehicle comprising:
receiving vehicle position data from a Global Navigation Satellite System (GNSS) receiver;
receiving vehicle motion data from an Inertial Measurement Unit (IMU);
receiving steering shaft encoder data from a steering shaft rotation encoder;
determining a current wheel angle of the vehicle based on the vehicle position data, the vehicle motion data, and the steering shaft encoder data;
determining a steering command based on the current wheel angle and a desired wheel angle; and
transmitting the steering command to a steering motor,
wherein the current wheel angle of the vehicle is determined using the equation:
a
tan
(
L
*
ω
z
V
)
where L is a length between a front axle and a rear axle of the vehicle, ω z is a vertical angular rate of the vehicle, and V is a longitudinal speed of the vehicle, and the result of the equation is filtered using a second order closed loop filter that uses encoder data multiplied by a reduction ratio factor.
2 . The method of claim 1 , wherein ω z is measured by a vertical gyro as the vehicle motion data.
3 . The method of claim 2 , wherein V is determined using the vehicle position data.
4 . The method of claim 3 , wherein the desired wheel angle is determined using the equation:
w
1
*
Y
+
w
2
*
θ
where w 1 and w 2 are weight factors, Y is a cross track metric, and θ is an angular heading offset.
5 . An automatic steering system for a vehicle comprising:
a global navigation satellite system (GNSS) receiver for transmitting vehicle position data to a steering controller;
an inertial measurement unit (IMU) for transmitting vehicle motion data to the steering controller; and
a steering shaft rotation encoder for transmitting steering shaft encoder data to the steering controller,
wherein the steering controller is configured to:
determine a current wheel angle using the vehicle position data, the vehicle motion data, and the steering shaft encoder data;
determine a steering command based on a current wheel angle and a desired wheel angle; and
transmit the steering command to a steering motor,
wherein the current wheel angle of the vehicle is determined using the equation:
a
tan
(
L
*
ω
z
V
)
where L is a length between a front axle and a rear axle of the vehicle, ω z is a vertical angular rate of the vehicle, and V is a longitudinal speed of the vehicle, and the result of the equation is filtered using a second order closed loop filter that uses encoder data multiplied by a reduction ratio factor.
6 . The system of claim 5 , wherein ω z is measured by a vertical gyro as the vehicle motion data.
7 . The system of claim 6 , wherein V is determined using the vehicle position data.
8 . The system of claim 7 , wherein the desired wheel angle is determined using the equation:
w
1
*
Y
+
w
2
*
θ
where w 1 and w 2 are weight factors, Y is a cross track metric, and θ is an angular heading offset.
9 . A computer readable medium storing computer program instructions for determining a position of a mobile station, the computer program instructions, when executed on a processor, cause the processor to perform operations comprising:
receiving vehicle position data from a Global Navigation Satellite System (GNSS) receiver;
receiving vehicle motion data from an Inertial Measurement Unit (IMU);
receiving steering shaft encoder data from a steering shaft rotation encoder;
determining a current wheel angle of the vehicle based on the vehicle position data, the vehicle motion data, and the steering shaft encoder data;
determining a steering command based on the current wheel angle and a desired wheel angle; and
transmitting the steering command to a steering motor,
wherein the current wheel angle of the vehicle is determined using the equation:
a
tan
(
L
*
ω
z
V
)
where L is a length between a front axle and a rear axle of the vehicle, ω z is a vertical angular rate of the vehicle, and V is a longitudinal speed of the vehicle, and the result of the equation is filtered using a second order closed loop filter that uses encoder data multiplied by a reduction ratio factor.
10 . The computer readable medium of claim 9 , wherein ω z is measured by a vertical gyro as the vehicle motion data.
11 . The computer readable medium of claim 10 , wherein V is determined using the vehicle position data.
12 . The computer readable medium of claim 11 , wherein the desired wheel angle is determined using the equation:
w
1
*
Y
+
w
2
*
θ
where w 1 and w 2 are weight factors, Y is a cross track metric, and θ is an angular heading offset.