Study On Vision Measurement System For Vehicle Wheel Alignment Parameters

The operating stability and driving security, unusual tire wearing and increasingfuel consumption of the vehicle are related to the wheel alignment parameters, whichare some angles and distances in static installation of the wheel, including mainlycaster, KPI (King Pin Inclination), camber and toe-in. At present, most wheelalignment equipments use contact-type method at home and abroad. Because of thelimitation of measurement principle, the inspection process of the contact wheelalignment system is very complex. So it can't realize rapid inspection and is difficultto widely use in modern auto manufactory and inspection line. This paper presents ameasurement method for wheel alignment parameters with computer vision inspectiontechnology, and develops a non-contact alignment system with advantages ofhigh-speed inspection, operating convenience and moderate precision.The main research work in this paper includes:1. Based on the theory of computer vision inspection, this paper sets up anon-contact vision measurement system for vehicle wheel alignment parameters,and which can indirectly measure caster and KPI cooperated with the turntable.The scheme for two steering-wheels alignment is introduced in this thesis.2. In order to control the selection of multiplex video channels conveniently andrealize automatic measurement, a multiplexer switch circuit is designed based onserial communication between computer and singlechip.3. After analyzing and summarizing current alignment algorithms, a tangent planealgorithom is presented, which is composed of ellipse fitting in 2D space andsearching algorithm in 3D space.4. To obtain the value of rotation in the steering process of the wheel, a wheel rimand laser strip alignment algorithm is presented. According to the characteristic ofthe wheel and image, the curves of the rim and the laser strip can be gained byimage processing techniques. And this algorithm works out the locating plane andthe rotation angle of the wheel.5. The alignment parameters of single wheel are measured in field experiment, andthe results of the system are stable and reliable.