PREDICTIVE VEHICLE CONTROLLER

• US 20090048748A1
• Filed: 10/22/2008
• Published: 02/19/2009
• Est. Priority Date: 06/12/2002
• Status: Active Grant

• Current Assignee: Hyster-Yale Materials Handling Incorporated (Nacco Industries Incorporated)
• Original Assignee: NMHG Oregon, LLC
• Inventors: Chen, Chenyao, Zhao, Side
• Granted Patent: US 8,135,531 B2
• Time in Patent Office: Days
• US Class Current: 701/59
• CPC Class Codes: B60W 10/04 including control of propulsion units
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/10 including control of change-speed gearings
• CPC Class Codes: B60W 2050/001 Proportional integral [PI] controller
• CPC Class Codes: B60W 2050/0022 Gains, weighting coefficients or weighting functions
• CPC Class Codes: B60W 2050/0031 Mathematical model of the vehicle
• CPC Class Codes: B60W 2530/10 Weight
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 30/188 Controlling power parameters of the driveline, e.g. determining the required power
• CPC Class Codes: B60W 40/105 Speed
• CPC Class Codes: B60W 50/0097 Predicting future conditions
• CPC Class Codes: B60W 50/06 Improving the dynamic response of the control system, e.g. improving the speed of regulation or avoiding hunting or overshoot
• CPC Class Codes: B60Y 2400/428 Double clutch arrangements; Dual clutches
• CPC Class Codes: G05B 13/048 using a predictor
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Due to time delays, vehicle speed may become difficult to control. A predictive speed controller is configured to receive a desired speed request for a vehicle and simulate vehicle responses according to the desired speed request. A compensation value is derived from the simulated vehicle responses that compensates for the time delays of the vehicle. The actual speed of the vehicle is then controlled according to the compensation value.

Claims

1. A vehicle speed control system, comprising:

a controller configured to;

receive a desired speed request for a vehicle;

simulate vehicle responses associated with the desired speed request;

derive a compensation value from the simulated vehicle responses associated with delays in the vehicle responding to the desired speed request; and

control the actual vehicle speed according to the compensation value.

2. The vehicle speed control system according to claim 1 wherein the controller is further configured to:

use one or more models to simulate the vehicle responses;

identify model errors by comparing the simulated vehicle responses with an actual vehicle response;

derive a correction value corresponding with the identified model errors; and

feed the correction value back into one or more of the models to generate corrected simulated vehicle responses.

3. The vehicle speed control system according to claim 2 wherein the controller is further configured to apply different gains to the identified modeling errors according to different associated actual vehicle speeds.

4. The vehicle speed control system according to claim 3 further comprising a look up table having a predetermined set of gain values that the controller applies to the identified modeling errors according to the actual vehicle speed.

5. The vehicle speed control system according to claim 4 further comprising different predetermined sets of gain values that are used by the controller for different vehicle operations or different vehicle conditions.

6. The vehicle speed control system according to claim 1 wherein the controller is further configured to:

use a first model to simulate a first vehicle response having a time delay;

use a second model to simulate a second vehicle response without the time delay; and

compare the first simulated vehicle response with the second simulated vehicle response to derive the compensation value.

7. The vehicle speed control system according to claim 6 wherein the first model and the second model together comprise a Smith Predictor.

8. The vehicle control system according to claim 7 wherein the controller is further configured to:

identify a modeling error in the Smith Predictor by comparing the first simulated vehicle response from the first model with the actual vehicle speed;

derive a correction value for the identified modeling error; and

apply the correction value to the first and second model in the Smith Predictor.

9. The vehicle speed control system according to claim 6 wherein the controller is further configured to output control values for controlling the actual speed of the vehicle and feed-back the control values to the first and second models to generate the first and second simulated vehicle response, respectively.

10. The vehicle control system according to claim 1 wherein the controller is further configured to:

simulate a response of an industrial vehicle that uses a power shift transmission;

derive the compensation value according to the simulated industrial vehicle response; and

use the compensation value to control the speed of the industrial vehicle via the power shift transmission.

11. The vehicle control system according to claim 1 wherein the controller is further configured to:

monitor a speed pedal position that corresponds with the desired speed request;

use the simulated vehicle responses to generate a compensation value that predicts at least some changes in the vehicle speed caused by the delays of the vehicle responding to the desired speed request; and

use the compensation value to compensate for at least some changes in the vehicle speed caused by the time delays.

12. A method, comprising:

receiving a speed control signal for controlling the speed of a vehicle;

predicting a first vehicle speed with a time delay according to the speed control signal;

predicting a second vehicle speed without the time delay according to the speed control signal;

identifying a difference between the first predicted vehicle speed and the second predicted vehicle speed; and

using the identified difference between the first predicted vehicle speed and the second predicted vehicle speed as feed-back for adjusting the speed control signal.

13. The method according to claim 12 further comprising:

using a first mathematical model to predict the first vehicle speed; and

using a second mathematical model to predict the second vehicle speed.

14. The method according to claim 13 further comprising:

identifying a modeling error by comparing the output from the first mathematical model with an actual vehicle speed;

deriving a correction value corresponding with the identified modeling error; and

feeding the correction value back into the first and second mathematical models.

15. The method according to claim 14 further comprising:

storing a set of different predetermined gain values;

identifying one of the gain values associated with the actual vehicle speed; and

applying the identified gain value to the identified modeling error to derive the correction values.

16. The method of claim 12 further comprising predicting the first vehicle speed and the second vehicle speed for a vehicle having a power shift transmission.

17. The method according to claim 12 further comprising deriving a compensation value according to the identified difference between the first predicted vehicle speed and the second predicted vehicle speed.

18. The method according to claim 17 further comprising:

combining an actual vehicle travel speed with the compensation value to derive a final predicted travel speed;

deriving a predicted travel speed tracking error by taking a difference between the desired vehicle speed and the final predicted travel speed; and

adjusting the speed control signal according to the predicted travel speed tracking error.

19. A Pedal Based Speed Control (PBSC) system for an industrial vehicle, comprising:

a first sensor configured to identify different pedal positions corresponding to different selected travel speed;

a second sensor configured to identify an actual vehicle speed; and

a processor configured to derive an intended travel speed that predicts what the vehicle travel speed would have been if the vehicle had little or no time delay responding to the selected travel speed, the processor further configured to control the actual vehicle speed according to the difference between the selected travel speed and the intended travel speed.

20. The PBSC system according to claim 19 wherein the processor is further configured to:

predict the vehicle speeds with a time delay and without a time delay;

subtract the differences between the predicted vehicle speeds to derive a time delay compensation value;

combine the actual vehicle speed with the time delay compensation value to derive the intended travel speed;

derive a travel speed tracking error by taking the difference between the selected travel speed and the intended travel speed; and

adjusting the actual vehicle travel speed according to the derived travel speed tracking error.

21. The PBSC system according to claim 20 wherein the processor is further configured to:

use a first model to predict a response of a vehicle with a power shift transmission and with a time delay;

use a second model configured to predict a response of the vehicle with the power shift transmission and without a time delay; and

compare prediction outputs from the first and second model to generate the time delay compensation value.

22. The PBSC system according to claim 21 wherein the processor is further configured to dynamically compensate for errors between the predicted responses and actual responses of the vehicle and power shift transmission.

23. The PBSC system according to claim 21 wherein the first and second model use:

a vehicle mass value representing vehicle translation inertia, a vehicle rotational inertia, and a vehicle workload capacity;

a damping coefficient representing a vehicle load and a constant travel speed; and

a discrete integrator that converts an acceleration value generated according to the vehicle mass value and the damping coefficient into a speed signal.

24. The PBSC system according to claim 23 wherein the first and second models are implemented using the relationship: