Dynamic velocity planning method for autonomous vehicle and system thereof

1. A dynamic velocity planning method for an autonomous vehicle, which is performed to plan a best velocity curve of the autonomous vehicle, and the dynamic velocity planning method for the autonomous vehicle comprising:

performing an information storing step to drive a memory to store an obstacle information of an obstacle, a road information and a vehicle information of the autonomous vehicle, wherein the vehicle information comprises a jerk threshold and a jerk switching frequency threshold;

performing an acceleration limit calculating step to drive a processing unit to receive the vehicle information from the memory and calculate the vehicle information according to a calculating procedure to generate an acceleration limit value range of the autonomous vehicle;

performing an acceleration combination generating step to drive the processing unit to receive the obstacle information and the road information from the memory and plan an acceleration interval of the autonomous vehicle according to the obstacle information, the road information and the acceleration limit value range, and then generate a plurality of acceleration combinations of the autonomous vehicle according to the acceleration interval;

performing an acceleration filtering step to drive the processing unit to filter the acceleration combinations according to the jerk threshold and the jerk switching frequency threshold to obtain a selected acceleration combination; and

performing an acceleration smoothing step to drive the processing unit to execute a driving behavior procedure to adjust the selected acceleration combination to generate the best velocity curve;

wherein the vehicle information further comprises a front wheel cornering stiffness, a rear wheel cornering stiffness, a front wheelbase, a rear wheelbase, a vehicle inertia and a vehicle mass.

2. The dynamic velocity planning method for the autonomous vehicle of claim 1 , wherein the acceleration limit calculating step comprises:

performing a lateral acceleration calculating step to drive the processing unit to calculate the vehicle information according to a dynamics calculating model to generate a lateral acceleration of the autonomous vehicle;

performing a longitudinal acceleration calculating step to drive the processing unit to calculate the lateral acceleration according to a friction circle calculating model to generate a longitudinal acceleration of the autonomous vehicle; and

performing a longitudinal-velocity and lateral-velocity calculating step to drive the processing unit to calculate the lateral acceleration and the longitudinal acceleration according to a kinematics calculating model to generate a lateral velocity and a longitudinal velocity of the autonomous vehicle, respectively.

3. The dynamic velocity planning method for the autonomous vehicle of claim 1 , wherein the acceleration combination generating step comprises:

performing an acceleration interval generating step, wherein the acceleration interval generating step is implemented by the processing unit and comprises:

performing an obstacle limiting step to limit the acceleration limit value range of the autonomous vehicle according to the obstacle information to generate an initial acceleration interval; and

performing a road limiting step to limit the initial acceleration interval according to the road information to generate the acceleration interval.

4. The dynamic velocity planning method for the autonomous vehicle of claim 3 , wherein the acceleration combination generating step further comprises:

performing an acceleration dispersing step, wherein the acceleration dispersing step is implemented by the processing unit and comprises:

performing a dispersing step to generate a plurality of acceleration groups according to a predetermined time interval and the acceleration interval and disperse each of the acceleration groups according to a predetermined acceleration interval to generate at least one acceleration target point; and

performing a target point combining step to sequentially combine the at least one acceleration target point of each of the acceleration groups to generate the acceleration combinations.

5. The dynamic velocity planning method for the autonomous vehicle of claim 1 , wherein each of the acceleration combinations comprises a maximum jerk and a jerk switching frequency, the jerk threshold is represented as J threshold , the maximum jerk of each of the acceleration combinations is represented as J max , the jerk switching frequency of each of the acceleration combinations is represented as Jfrequency, and the jerk switching frequency threshold is represented as f threshold and conforms to the following equation:

J max ≤J threshold ; and

EJfrequency≤ f threshold .

6. The dynamic velocity planning method for the autonomous vehicle of claim 1 , wherein the acceleration smoothing step comprises:

performing an adjusting step to adjust the selected acceleration combination according to one of a progressive model, a normal model and a conservative model to generate an artificial acceleration combination, wherein the artificial acceleration combination has a plurality of optimal accelerations; and

performing a fitting step to integrate and smooth the optimal accelerations of the artificial acceleration combination to fit the best velocity curve.

7. A dynamic velocity planning system for an autonomous vehicle, which is performed to plan a best velocity curve of the autonomous vehicle, and the dynamic velocity planning system for the autonomous vehicle comprising:

a memory configured to access an obstacle information of an obstacle, a road information, a vehicle information of the autonomous vehicle, a calculating procedure and a driving behavior procedure, wherein the vehicle information comprises a jerk threshold and a jerk switching frequency threshold; and

a processing unit electrically connected to the memory, wherein the processing unit is configured to implement a dynamic velocity planning method for the autonomous vehicle comprising:

performing an acceleration limit calculating step to calculate the vehicle information according to the calculating procedure to generate an acceleration limit value range of the autonomous vehicle;

performing an acceleration combination generating step to plan an acceleration interval of the autonomous vehicle according to the obstacle information, the road information and the acceleration limit value range, and then generate a plurality of acceleration combinations of the autonomous vehicle according to the acceleration interval;

performing an acceleration filtering step to filter the acceleration combinations according to the jerk threshold and the jerk switching frequency threshold to obtain a selected acceleration combination; and

performing an acceleration smoothing step to execute the driving behavior procedure to adjust the selected acceleration combination to generate the best velocity curve;

wherein the vehicle information further comprises a front wheel cornering stiffness, a rear wheel cornering stiffness, a front wheelbase, a rear wheelbase, a vehicle inertia and a vehicle mass.

8. The dynamic velocity planning system for the autonomous vehicle of claim 7 , wherein the memory comprises a dynamics calculating model, a friction circle calculating model and a kinematics calculating model, and the acceleration limit calculating step comprises:

performing a lateral acceleration calculating step to calculate the vehicle information according to the dynamics calculating model to generate a lateral acceleration of the autonomous vehicle;

performing a longitudinal acceleration calculating step to calculate the lateral acceleration according to the friction circle calculating model to generate a longitudinal acceleration of the autonomous vehicle; and

performing a longitudinal-velocity and lateral-velocity calculating step to calculate the lateral acceleration and the longitudinal acceleration according to the kinematics calculating model to generate a lateral velocity and a longitudinal velocity of the autonomous vehicle, respectively.

9. The dynamic velocity planning system for the autonomous vehicle of claim 7 , wherein the processing unit is configured to implement an acceleration interval generating step, and the acceleration interval generating step comprises:

performing an obstacle limiting step to limit the acceleration limit value range of the autonomous vehicle according to the obstacle information to generate an initial acceleration interval; and

performing a road limiting step to limit the initial acceleration interval according to the road information to generate the acceleration interval.

10. The dynamic velocity planning system for the autonomous vehicle of claim 9 , wherein the processing unit is configured to implement an acceleration dispersing step, and the acceleration dispersing step comprises:

performing a dispersing step to generate a plurality of acceleration groups according to a predetermined time interval and the acceleration interval and disperse each of the acceleration groups according to a predetermined acceleration interval to generate at least one acceleration target point; and

performing a target point combining step to sequentially combine the at least one acceleration target point of each of the acceleration groups to generate the acceleration combinations.

11. The dynamic velocity planning system for the autonomous vehicle of claim 7 , wherein each of the acceleration combinations comprises a maximum jerk and a jerk switching frequency, the jerk threshold is represented as J threshold , the maximum jerk of each of the acceleration combinations is represented as J max , the jerk switching frequency of each of the acceleration combinations is represented as Jfrequency, and the jerk switching frequency threshold is represented as f threshold and conforms to the following equation:

J max ≤J threshold ; and

EJfrequency≤ f threshold .

12. The dynamic velocity planning system for the autonomous vehicle of claim 7 , wherein the processing unit is configured to implement the acceleration smoothing step, and the acceleration smoothing step comprises:

performing an adjusting step to adjust the selected acceleration combination according to one of a progressive model, a normal model and a conservative model to generate an artificial acceleration combination, wherein the artificial acceleration combination has a plurality of optimal accelerations; and

performing a fitting step to integrate and smooth the optimal accelerations of the artificial acceleration combination to fit the best velocity curve.