Research On Door Opening Control System Based On Vision Information And Azimuth For A Mobile Manipulator

Autonomous door opening control with robot is a challenging research topic in thefield of automation, recognition and location of target in the movement of robot andcoordination control between manipulator and mobile platform are the difficulties ofresearch on autonomous door opening control, study on door opening allows robot to havea wider workspace, which has theoretical and practical significance makes robot theability to serve mankind has been further improved. Mobile manipulator platform wasstudied in this paper, the operation of door handle by manipulator was conbined with themotion control of mobile platform, visual imformation and azimuth were adopted as theinformation acquisition for mobile manipulator, implementation of door opening controlsystem was researched, door opening control strategy for mobile manipulator wasdesigned, the mission of door opening when mobile manipulator is in any initial positionwas accomplished, the main research achievements of this dissertation are shown asfollows:1) An approach to locate the door handle with color space was adopted. As the visualinformation observation range is wider and easier acquisition characteristics, the visualapproach was applied to locate the door handle in this paper. Based on the analysis of thecolor space theory of image processing, the HSI color space was selected for colordescription. Color space transform method was used to transform the image captured byKinect from RGB color space to HSI color space, the threshold segmentation of H,S,I wasoperated in HSI color space, and the door handle was separated from the captured image.Based on the threshold value range of the three components, the door handle was real-timecaptured and located within the movement of MT-A. Experiments demonstrate theeffectiveness of this method.2) A judge method of door opening degree which combines the azimuth control,eigenvalue method and depth data was proposed. First, digital compass was used tocontrol the azimuth of MT-A, which ensure the X axis of movement coordinate wasperpendicular to the plane of the door. Then, by selecting the top right three-dimensionalcoordinates of the depth image of the door handle, using the depth data to fit a planewithin eigenvalue method, the normal vector of the plane could be obtained by the theplane equation coefficients a,b,c,d. Finally, combining with the normal vector of yoz planeof the Kinect real coordinate, the door opening degree was calculated. The depth datas were analyzed when the door opening degree were0°,30°,45°,60°, the resultsdeviation were all less±5°, the experimental results demonstrate the effectiveness of theproposed method.3) A control strategy of door open based on visual guiding was designed andimplemented when MT-A is in a fixed position. Based on the characteristics of the mobileplatform and the manipulator of MT-A, a pushdown action of the end effector wasselected to accomplish the door open experiment. The initial conditions of the experimentsare that the X axis of movement coordinate is perpendicular to the door plane, usingKinect to real-time locate the door handle, and get the three-dimensional coordinates ofdoor handle in Kinect real coordinate, and the distance between door handle and MT-A inMT-A movement coordinate was obtained by transforming the coordinates from Kinectreas coordinate to MT-A movement coordinate. MT-A was guided best position in front ofthe door based on the distance information, by calculating the angle of five joints of themanipulator with the inverse kinematics method, steering the manipulator to push downthe door handle and the door opened. Experimental results demonstrate the effectivenessof this control strategy.4) A control strategy of door open was devised when MT-A is in any initial position.The focus of this research was identified with navigation control of MT-A, based on thespecial requirements of experimental environment of door open, a non-map navigationwas selected, making the X axis of movement coordinate is perpendicular to the doorplane by using the digital compass LP3300, the value of x was mapped to the realmovement environment of MT-A, so the horizontal offset distance was obtained. Based onthe MT-A motion characteristics which is two-wheel drive, therefore, the operation oftarget guidance, combining with visual information and azimuth control was adopted, amethod combining with three-dimensional coordinates measurement, azimuth anglecontrol and positionloop of MT-A motion was proposed, a control strategy of door openwas designed when MT-A is in any initial position, the experimental results verify theeffectiveness of this method.