Non-contact method and apparatus for determining camber and caster of a vehicle wheel

In a non-contact wheel alignment machine for use in determining one or more wheel alignment characteristics of a vehicle, said wheel alignment machine having a computer and a plurality of non-contact measurement sensors electrically connected to said computer, wherein at least one of said measurement sensors includes:

• first and second toe light sources that project shaped light onto a sidewall of a tire of one of the vehicle's wheels at respective first and second locations;
• a third light source that projects shaped light onto the sidewall of the tire at a third location;
• and
• an optical sensor system having one or more fields of view that includes said first, second, and third locations;
• and
• wherein said computer is operable under control of a program and in response to data from said optical sensor system to determine a toe angle and a camber angle associated with the tire;
• wherein the improvement comprises:
• said third location being offset from a vertical measurement plane that extends through the center of the wheel perpendicular to the wheel's rotational plane,
• said computer being operable under control of said program to determine an offset distance relating to the distance between said third location and the center of the wheel;
• and
• said computer being operable under control of said program to utilize said offset distance in determining said camber angle.

A non-contact measurement sensor for use in determining one or more wheel alignment characteristics of a tire on a vehicle, comprising:

• first and second toe light sources that project shaped light onto a sidewall of the tire at respective fore and aft locations;
• a third light source that projects shaped light onto said wheel at an upper location;
• a fourth light source that projects shaped light onto said wheel at an offset location that is adjacent said upper location;
• and
• an optical sensor system having one or more fields of view that includes said fore, aft, upper, and offset locations.

A method of calculating the camber angle of a wheel of a vehicle using a measurement sensor that includes an optical sensor having a field of view and one or more light sources for projecting shaped light onto the wheel, the method comprising the steps of:

• illuminating a measurement point on the wheel using shaped light projected onto the wheel at a first location that is offset to one side of a vertical measurement plane that extends through the center of the wheel and generally perpendicular to the rotational plane of the wheel,
• sensing a portion of the shaped light reflected from the first location and generating data representative of the location of the measurement point,
• obtaining a toe angle for the wheel,
• determining the position of a camber reference point in at least one dimension,
• using the toe angle to determine the horizontal displacement within the vertical measurement plane of the measurement point from the camber reference point, and
• calculating the camber angle of the wheel using the horizontal displacement.

A method of determining one or more alignment characteristics of a wheel of a vehicle using a measurement sensor that includes an optical sensor and one or more light sources for projecting shaped light onto the wheel, the method comprising the steps of

• (a) illuminating a portion of the wheel using shaped light projected onto the wheel at an upper location that is offset to one side of a vertical measurement plane which extends through the center of the wheel,
• (b) sensing a portion of the shaped light reflected from the upper location and generating position data that corresponds to an offset measurement point located at the upper location,
• (c) obtaining a toe angle for the wheel, and
• (d) determining a camber angle for the wheel using the position data and toe angle.

A non-contact wheel alignment machine for use in determining one or more wheel alignment characteristics of a vehicle, comprising:

• a circuit having a microprocessor and memory accessible by said microprocessor, said memory having an executable computer program stored therein;
• one or more non-contact measurement sensors electrically connected to said circuit, wherein at least one of said measurement sensors includes:
• one or more light sources that projects shaped light onto a sidewall of the tire at fore, aft and upper locations, with said shaped light being projected onto the sidewall at said upper location along an axis that is parallel to and offset from a vertical reference plane, wherein said vertical reference plane corresponds to a measured toe angle of zero degrees when the rotational plane of the tire is perpendicular to said vertical reference plane;
• and
• an optical sensor system having one or more fields of view that includes said fore, aft, and upper locations, said optical sensor system being operable to provide data related to images contained within said fields of view;
• wherein said microprocessor is operable under control of said program to determine a camber angle associated with the tire using the data received from said optical sensor system.