Method of simulating the performance of a vehicle on a road surface

• US 6,754,615 B1
• Filed: 03/09/2000
• Issued: 06/22/2004
• Est. Priority Date: 03/12/1999
• Status: Expired due to Fees

• Current Assignee: Dr. Ing. H.C.F. Porsche Ag
• Original Assignee: Dr. Ing. H.C.F. Porsche Ag, AVL Deutschland GmbH (List Privatstiftung)
• Inventors: Pfeiffer, Michael, Kopecky, Wolfgang, Germann, Stefan, Witte, Lothar, Brodbeck, Peter, Abler, Georg, Xuan, Hai Tran, Nonn, Harald
• Primary Examiner(s): Broda, Samuel
• Application Number:
  US09/522,223
• Time in Patent Office: 1,566 Days
• Field of Search: 703/2, 703/7, 703/1, 702/140, 701/36, 731/46
• US Class Current: 703/8
• CPC Class Codes: B60C 19/00 Tyre parts or constructions not otherwise provided for
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00
• CPC Class Codes: B60C 99/006 Computer aided tyre design or simulation
• CPC Class Codes: B60T 2270/86 Optimizing braking by using ESP vehicle or tire model
• CPC Class Codes: G01M 13/025 Test-benches with rotational drive means and loading means; Load or drive simulation
• CPC Class Codes: G06F 30/15 Vehicle, aircraft or watercraft design
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]

Abstract

Method of simulating the performance of a vehicle on a roadway on a power train test bed with the help of torque-controlled electric load machines mounted on the shafts of the power train of the vehicle and with the help of a computer with a vehicle model stored therein and a tire model simulating the slip-dependent friction, in which method the angular wheel speed is measured on at least one of the shafts, and the tire model determines a force transmitted from the tire to the roadway at this angular wheel speed on the basis of the tire model using a vehicle velocity and a tire normal force, and it also determines a setpoint torque for this force for the torque-controlled load machine mounted on this shaft, in such a way that a difference corresponding to the actual slip is established between the measured angular wheel speed and a nominal angular wheel speed value corresponding to the vehicle velocity used in the tire model and calculated in the vehicle model with feedback of the force transferred to the road surface.

Claims

1. A method of simulating the performance of a vehicle on a road surface on a power train test bed by means of torque-controlled electric load machines mounted on shafts of a power train of the vehicle and by means of a computer forming a feedback control system with a torque-controlled electric load machine mounted on at least one of said shafts for providing a setpoint torque value for said at least one torque-controlled electric load machine,

the method comprising the following steps:

a) storing within said computer

a tire model providing values of a coefficient of friction as a function of slip of a tire for determining a slip-dependent friction of the tire on the road surface, and

a vehicle model for calculating a velocity of said vehicle and a normal force at the tire,

b) measuring an angular wheel speed on said at least one shaft,

c) determining a force transferred from the tire to the road surface at the measured angular wheel speed using the tire normal force provided by the vehicle model and a slip-dependent friction of the tire provided by the tire model using a value of the coefficient of friction for a slip of the tire occurring between the measured angular wheel speed and a nominal angular wheel speed which corresponds to the calculated vehicle velocity provided by the vehicle model,

d) determining a setpoint torque value for the torque-controlled load machine mounted on the at least one shaft at said measured angular wheel speed value using the vehicle velocity provided by the vehicle model and the tire normal force and the slip-dependent friction of the tire determined in step c),

e) feeding back the force transferred from the tire to the road as determined in step c) from the tire model into the vehicle model to be used in the vehicle model for recalculating the vehicle velocity,

f) reentering the value of the vehicle velocity recalculated in step e) into the tire model, and

g) repeating steps b) to d) to recalculate the setpoint torque value for the torque-controlled load machine mounted on the at least one shaft.

2. A method according to claim 1 wherein step a) comprises entering parameters of the tire to be simulated and parameters of the road surface into the tire model.

3. A method according to claim 1 comprising calculating, in the vehicle model of the computer, a vehicle resistance force which depends on the vehicle velocity, subtracting the force transferred from the tire to the road surface from the calculated resistance force, and determining the vehicle velocity using the resulting difference value and a mass of the vehicle.

4. A method according to claim 1 comprising calculating, in the vehicle model of the computer, a vehicle resistance force which depends on the vehicle velocity, subtracting the force transferred from the tire to the road surface and forces transmitted to the road surface from any other tire to be simulated from the calculated resistance force, and determining the vehicle velocity using the resulting difference value and a mass of the vehicle.

5. A method according to claim 1 comprising:

calculating a steering angle of a wheel comprising the tire, said steering angle resulting from a given steering-wheel angle, and

using a side slip angle of the wheel which results from the above steering-wheel angle in order to calculate a lateral and a longitudinal slip of the tire in the tire model.

6. A method according to claim 5 wherein a lateral force, a longitudinal force and a self aligning torque of the tire are determined taking into account said lateral and said longitudinal slip and are fed back into the vehicle model.

7. A method according to claim 1 comprising taking into account vehicle dynamics when determining the tire normal force in the vehicle model.

8. A method according to claim 1 comprising calculating a rolling resistance force as a function of the tire normal force and the measured angular wheel speed value and using the calculated rolling resistance force when determining the force transferred from the tire to the road surface.

9. A method according to claim 1 wherein step a) comprises entering:

constants for taking into consideration slip dynamics and related damping,

a radius of the tire, and

at least one characteristic map selected from a group consisting of;

a characteristics map for a longitudinal force transferred to the road surface,

a characteristics map for a lateral force applied by the tire to the road surface, and

a characteristics map for a self aligning torque of the tire,

as tire parameters for the tire model into the computer.

10. A method according to claim 1 comprising entering a king pin angle and a braking moment into the computer to be used in the tire model and the vehicle model.

11. A method according to claim 1 wherein electric load machines each simulating a moment of inertia of a respective wheel are used as said torque-controlled electric load machines.

12. A method according to claim 1 wherein feedback control means are provided for each one of said torque-controlled electric load machines respectively mounted on a shaft of said vehicle.