Research On Tool Trajectory Planning Of Spray Robot Based On Moving Frame

The auto-trajectory planning of spray gun is an important research in intelligent spray robot field. Currently the format of CAD model of the part to be painted is mostly based on tessellated models, which has the disadvantages such as lack of geometrical information about edges and curve and existing of much redundant information. Mesh model is too complicated for ruled surface and causes missing and overlapping facets for large curvature surface which increases the trajectory planning difficulty for mesh repairing and spray path connections of mall facets. It causes the lower trajectory planning efficiency and spray quality. For CAD parameterized model of spray surface, differential geometry theory combining with spray process is applied to the spray gun model, path pattern, spray accumulation model, spray trajectory planning, conversion of spray trajectory and spray gun trajectory optimization, and trajectory planning of compound surfaces. The major research content of this dissertation is as follows:1. For CAD parametric model of part to be painted, using the standard for exchange of product STEP as the format of model in spray path planning, data drawn from STEP format of the part to be painted is converted into the parameters of surface expression required in spray trajectory planning.2. Based on curve and surface theory of differential geometry, elliptic double-(3distribution model of air gun is used to generate the spray paths, a comparison between the raster pattern and spiral patterns path regarding continuous material deposion is made and draw a conclusion on the relationship between continuous material deposion and surfaces measurement.3. Given the path of the regular surface, the relations of continuous material deposion model between a point and the center in the spary region along the normal curvature direction is specified based on the moving frames of differential geometry. The coefficients of velocity of one point to the center and sparying direction are defined. Spraying in equal height and constant velocity, regarding the mean square error of the material thickness deviation form required material thicknes as optimized objective, and spraying velocity is expressed as a function of overlapping distance, the optimization problem become a one-dimensional variable optimization, optimal spary gun velocity and overlapping distance are calculated. Material thickness and uniformity of two kinds of path and different overlapping distance on cylindrical surface are compared.4. Based on Gauss-Bonnet theory of differential geometry, the method offseting start geodesic and offseting start section with minimum geodesic curvature on freeform surface are adopted to generate spraying trajectory. Considering uniformity of material thickness and a minimum spray time the start geodesic curve and the start section are specified by theoretical analysis and formula reduction. Based on the moving frame and exterior differentiation conclude relationship between the frames of spray trajectory on surface and tool ones, and gives motion formula of the position and oriention of spray gun.5. According to the relationship between the spray path of single patch and the intersection line of the composite surface, material deposition model on intersection region is given. Using graph theory, the spray paths sequence on the composite surface is regarded as open-loop Hamiltonian graph, based on genetic algorithm the sequence and direction of spraying path of the composite surface are optimized, and the optimal results is obtained.