Method and system for motor vehicle longitudinal control
The invention relates to a method for longitudinal control of a motor vehicle, the motor vehicle having an engine and a braking system. The method including receiving a torque demand from a controller for controlling the speed of the vehicle, and providing a torque on the basis of this torque demand, whereby, depending on the value of the torque demand, a brake torque counteracts the torque demand to control longitudinal vehicle movement.
1. A method for longitudinal control of a motor vehicle comprising:
determining a drive torque based on a set vehicle speed and actual speed;
calculating an engine speed from said drive torque;
using the higher of the calculated engine speed and an engine idle speed to determine a propulsion torque;
comparing said propulsion torque with said drive torque; and
applying a brake torque to compensate for the difference in said drive torque and said propulsion torque when said propulsion torque is greater than said drive torque.
2. The method of claim 1 including changing said idle speed to change said propulsion torque while maintaining said brake torque at a constant value.
3. The method of claim 1 wherein said brake torque is independent of and does not vary with respect to a change in said engine idle speed.
4. The method of claim 1 wherein the method is performed by a PID controller controlling vehicle speed, said controller having an integral component; and
deactivating the integral control if a deviation of the vehicle speed lies within a predetermined tolerance range.
5. The method of claim 4 wherein if the deviation of the vehicle speed lies outside a predetermined tolerance range, the algebraic sign of the deviation, multiplied by an amplification factor, is integrated in the integral component of the PID controller.
6. The method of claim 5 wherein in the differential component of the PID controller the derivative of the deviation is supplied to an integrator, minus a feedback amplification signal of the integrator.
7. A method for longitudinal control of a motor vehicle comprising:
determining a requested output torque based on a set vehicle velocity;
using an engine idle speed to determine a propulsion torque;
determining a delta torque from said requested output torque and said propulsion torque;
establishing an overlap torque;
using said overlap torque and said delta torque to determine a brake torque demand; and
applying said brake torque demand to a brake system to control vehicle longitudinal movement.
8. The method of claim 7 wherein the method is performed by a PID controller to control vehicle velocity, said controller having an integral component; and
deactivating the integral component if a control deviation of the vehicle velocity lies within a predetermined tolerance range.
9. The method of claim 8 wherein if the value of the deviation of the vehicle velocity lies outside a predetermined tolerance range, the algebraic sign of the deviation, multiplied by an amplification factor, is integrated in the integral component of the PID controller.
10. The method of claim 9 wherein in the differential component of the PID controller the derivative of the deviation is supplied to an integrator, minus a feedback amplification signal of the integrator.