Roadway grip tester and method

• US 20070204683A1
• Filed: 01/11/2007
• Published: 09/06/2007
• Est. Priority Date: 01/11/2006
• Status: Active Grant

• Current Assignee: Donald Halliday
• Original Assignee: Donald Halliday
• Inventors: Halliday, Donald
• Granted Patent: US 7,509,847 B2
• Time in Patent Office: Days
• US Class Current: 73/146
• CPC Class Codes: G01N 19/02 Measuring coefficient of friction between materials testing of tyres G01M17/02; determinations of friction coefficient used in vehicle braking or traction control systems B60T8/172

Abstract

A method for measuring-road surface friction of a road surface uses a vehicle that moves across the road surface wherein (1) an auxiliary independent wheel assembly is towed behind the vehicle and is in contact with the road surface, an auxiliary wheel of the wheel assembly is freely rotatable by movement of the vehicle and is one or more of toed in or toed out with respect to a direction of travel of the vehicle so as to create an isolated axial force on the auxiliary wheel: (2) the axial force on the auxiliary wheel is measured while the vehicle moves across the road surface, and the measured axial force is correlated with the road surface friction. The independent wheel assembly is load isolated from the weight of the towing vehicle and the independent wheel assembly is loaded by placing ballast thereon.

Claims

1. In a method for measuring road surface friction of a road surface using a vehicle that moves across the road surface wherein (1) an auxiliary independent wheel assembly is towed behind said vehicle and is in contact with the road surface, an auxiliary wheel of said wheel assembly is freely rotatable by movement of said vehicle and being one or more of toed in or toed out with respect to a direction of travel of said vehicle so as to create an isolated axial force on said auxiliary wheel:

(2) the axial force on said auxiliary wheel is measured while said vehicle moves across said road surface; and

said measured axial force is correlated with the road surface friction;

the improvement which comprises the steps of;

(A) the independent wheel assembly is load isolated from the weight of said towing vehicle; and

(B) the independent wheel assembly is loaded by placing ballast thereon.

2. The method of claim 1, wherein said independent wheel assembly is rigidly mounted to said towing vehicle.

3. The method of claim 1, wherein said load isolated is accomplished with a shock absorbing system placed between said towing vehicle and said independent wheel assembly.

4. The method of claim 1, wherein said ballast is placed in close proximity to said wheel of said independent wheel assembly.

5. The method of claim 1, wherein said axial force is measured with a load cell, which is fitted with a stop assembly to prevent overloading of said load cell.

6. The method of claim 5, wherein a spring be placed on either side of the load cell to allow the stop assembly to function.

7. The method of claim 5, wherein a heat insulating material thermally isolates said load cell.

8. The method of claim 1, wherein said independent wheel assembly is fitted with a wishbone support rigidly attached to said vehicle.

9. The method of claim 1, wherein said independent wheel assembly is connected by an arm that swings.

10. The method of claim 1, wherein said measured axial force is compensated by one or more of a tread depth factor, a road surface factor, a tire temperature factor, a speed factor, or a vehicle steering factor.

11. The method of claim 1, wherein said independent wheel assembly retains a wheel displacement sensor that is used to calculate tread depth.

12. The method of claim 8, wherein said independent wheel assembly is placed to one side of the center of the vehicle.

13. The method of claim 1, wherein a static height adjustment plate is placed between said independent wheel assembly and said vehicle.

14. The method of claim 1, wherein said independent wheel assembly can be lifted off the ground for transport.

15. The method of claim 1, wherein a linear relationship is developed between a friction number and the axial force on said independent wheel assembly, whereby 0 represents no force between the surface and the said independent wheel assembly and 100 represents the force between said independent wheel assembly and a good tarmac surface without surface contamination.

16. The method of claim 1, wherein a pair of independent wheel assemblies are mounted via a common support arm and on an independent wishbone that allows independent movement in the up and down direction.

17. In a device for measuring road surface friction of a road surface using a vehicle that moves across the road surface, including (1) an auxiliary freely rotatable independent wheel interposed between said vehicle and the road surface, and being one or more of toed in or toed out with respect to a direction of travel of said vehicle so as to create an axial force on said auxiliary wheel;

(2) an axial force sensor mounted with respect to said auxiliary wheel so as to measure the axial force exerted on said auxiliary wheel while said vehicle moves across said road surface;

(3) a converter for correlating the measured axial force with the road surface friction, the improvement which comprises;

(A) the independent wheel assembly being load isolated from the weight of said towing vehicle; and

(B) the independent wheel assembly being loaded by placing ballast thereon.

18. The device of claim 17, wherein said independent wheel assembly is rigidly mounted to said towing vehicle.

19. The device of claim 17, wherein said load isolated is accomplished with a shock absorbed placed between said towing vehicle and said independent wheel assembly.

20. The device of claim 17, wherein said ballast is placed in close proximity to said wheel of said independent wheel assembly.

21. The device of claim 17, wherein said axial force is measured with a load cell, which is fitted with a stop assembly to prevent overloading of said load cell.

22. The device of claim 21, wherein a spring is located on either side of the load cell to allow the stop assembly to function.

23. The device of claim 21, wherein a heat insulating material thermally isolates said load cell.

24. The device of claim 17, wherein said independent wheel assembly is fitted with a wishbone support rigidly attached to said vehicle.

25. The device of claim 17, wherein said independent wheel assembly is connected by an arm that swings.

26. The device of claim 17, wherein said measured axial force is compensated by one or more of a tread depth factor, a road surface factor, a tire temperature factor, a speed factor, or a vehicle steering factor.

27. The device of claim 17, wherein said independent wheel assembly retains a wheel displacement sensor that is used to calculate tread depth.

28. The device of claim 24, wherein said independent wheel assembly is placed to one side of the center of the vehicle.

29. The device of claim 17, wherein a static height adjustment plate is located between said independent wheel assembly and said vehicle.

30. The method of claim 17, wherein said independent wheel assembly is liftable off the ground for transport.

31. The device of claim 17, wherein a linear relationship is developed between a friction number and the axial force on said independent wheel assembly, whereby 0 represents no force between the surface and the said independent wheel assembly and 100 represents the force between said independent wheel assembly and a good tarmac surface without surface contamination.

32. The device of claim 17, wherein said independent wheel assembly comprises a pair of independent wheel assemblies supported via a common support arm and on an independent wishbone that allows independent movement in the up and down direction.

33. A method for measuring road surface friction of a road surface using a vehicle that moves across the road surface said vehicle having one or more independently suspended wheel assemblies having an axle and an axle support, which comprises the steps of:

(a) fitting one or more of each independently suspended wheel assemblies of said vehicle with an assembly that that measures axial force between the axle and the axle support of said vehicle; and

(b) measuring said axial force as said vehicle moves across a road surface; and

(c) correlating said measured axial force with the road surface friction of said road surface.

34. The method of clam 33, wherein larger measured axial forces correlate with greater road surface friction and smaller measured axial forces correlate with smaller road surface friction.

35. The method of clam 33, wherein said vehicle is driven in a straight line direction, opposite wheel assemblies are fitted with said axial force measuring assemblies, and the measured axial forces are compared to determine the road surface friction.

36. The method of clam 33, wherein toe angle of at least one of said wheel assemblies is set to be greater during winter driving then during summer driving of said vehicle.

37. The method of clam 33, wherein the measured road surface friction is communicated to a driver of said vehicle or to a remote location.

38. A method for signaling a second vehicle driver driving a second vehicle on a road and following a first driver driving a first vehicle on said road, which comprises providing a visual display in said first vehicle to said second driver correlative to the degree to which said first vehicle is decelerating.

39. The method of claim 38, wherein deceleration of said first vehicle is determined by one or more of sensing change in wheel speed, actual sensed values from the change in rotational speed of a wheel, an accelerometer, a decelerometer, or actual sensed values of the brake pressure applied by the first driver.

40. The method of claim 38, wherein said visual display comprises a grouping of lights displayed to said second driver wherein more lighted lights correlates with increased deceleration.

41. The method of claim 38, wherein said visual display comprises a grouping of lights displayed to said second driver wherein different colored lighted lights correlates with increased deceleration.

42. The method of claim 38, wherein the second vehicle is fitted with displacement sensors to determine the proximity of the first vehicle and said first vehicle senses above normal deceleration and that this sensed value of deceleration is used to one or more of visually or audibly indicate to the second driver the rapid closing of the distance between the two vehicles or that this sensed value be used to automatically decelerate the following vehicle.

43. A method for measuring road surface friction of a road surface using a vehicle that moves across the road surface said vehicle having one or more independently suspended wheel assemblies having wheel centers, which comprises measuring the axial force at one or more wheel centers.

44. A method for measuring road surface friction of a road surface using a vehicle that moves across the road surface said vehicle having one or more independently suspended wheel assemblies having an axle and an axle support, which comprises measuring the load on one or more of said struts.

45. A method for measuring road surface friction of a road surface using a vehicle that moves across the road surface said vehicle having one or more independently suspended wheel assemblies having an axle and an axle support, which comprises sensing the torque change (in plan view) by measuring a load on one or more of said struts.