In-oil autonomous operation detection robot of storage tank bottom plate and autonomous operation detection method

An in-oil autonomous operation detection robot of a storage tank bottom plate, wherein the in-oil autonomous operation detection robot of the storage tank bottom plate comprises a motion module, a positioning and attitude recognition module, an obstacle avoidance module, a detection module, a control module and a dredging module;

• wherein the control module is connected with the motion module, the positioning and attitude recognition module, the obstacle avoidance module, the dredging module and the detection module, respectively;
• the motion module is configured to adjust and control a motion direction, a speed and an attitude of the robot under a control of the control module;
• the positioning and attitude recognition module is configured to recognize a position and the attitude of the robot under the control of the control module;
• the obstacle avoidance module is configured to avoid obstacles under the control of the control module;
• and
• the detection module is configured to detect corrosions of the bottom plate under the control of the control module;
• the detection module comprises a detection component, a communication component and a detection control board;
• the detection component comprises a combination of one or more of a magnetic flux leakage detection sensor, an electromagnetic acoustic detection sensor, a guided wave detection sensor and a pulsed eddy current detection sensor;
• the detection component and the communication component are both connected with the detection control board;
• the detection control board is connected with the control module via the communication component and is configured to transmit a detection result back to the control module;
• wherein
• the control module is configured to activate the positioning and attitude recognition module to recognize the position and the attitude of the robot, control the motion module to adjust the position and the attitude at a start of the autonomous operation to a predetermined position and attitude and
• allow the robot to move according to an autonomously pre-planned traveling route;
• when the obstacle avoidance module explores unexpected obstacles in a traveling process, the control module is further configured to plan an optimal route, and control the motion module to modify the traveling route to avoid obstacles;
• wherein, the control module is further configured to control the detection module to perform a required detection on the storage tank bottom plate in the traveling process, and meanwhile, transmit a detection result back, during which the positioning and attitude recognition module continuously positions the robot to realize a one-to-one correspondence between position information and the detection result;
• wherein, the control module is further configured to control the motion module return the robot to an initial position according to a set traveling route, after a detection task is completed;
• wherein the positioning and attitude recognition module comprises acoustic signal generators installed on the robot, acoustic signal receivers installed on a tank wall and a gyroscope placed inside the robot;
• the positioning and attitude recognition module determines the position and a horizontal attitude of the robot via a robot positioning and attitude algorithm based on transmitted and received acoustic signals, and calculates a pitch attitude of the robot based on the gyroscope;
• the motion module comprises a wheel set and a driving motor;
• the obstacle avoidance module comprises pairs of acoustic signal generator and acoustic signal receiver;
• the control module comprises an upper computer and a main control board which are connected with each other;
• and
• the dredging module comprises dredging wheels arranged at both ends of the robot and is configured to cut oil sludge on a traveling route to expose the bottom plate to be detected;
• wherein, a path tracking algorithm is stored in the control module,
• wherein, at time tk, position coordinates of the robot itself are taken as coordinates of one of the acoustic signal generators in the positioning and attitude recognition module, which are denoted as Mk;
• a direction angle is calculated by an included angle between a connecting line of two acoustic signal generators and a front of the robot, and two front and rear positioning points of the two acoustic signal generators, which is denoted as θk;
• original values of an attitude of the robot are denoted as {Mk, θk};
• at time tk+1, if abnormal noise occurs, which leads to a change of a position or a direction beyond allowable values, measured values of the attitude are discarded, but the attitude at time tk+1 is predicted by using a speed, an angular speed and the attitude at the time tk instead, to obtain predicted values {{tilde over (M)}k+1, {circumflex over (θ)}k+1} of the attitude;
• otherwise, the attitude is updated;
• considering that there are errors in the positioning points of the two front and rear acoustic signal generators of the robot, a Kalman filter is used to reduce errors of the direction angle of the robot;
• an estimated value of the direction angle is {circumflex over (θ)}k;
• in order to eliminate distortion of a motion trajectory, a piecewise fitting method is used;
• every K points form a group to perform piecewise fitting;
• coordinates form a set M{M1, M2, . . . MK};
• a line segment L1 defined in a range of point set is obtained by a linear fitting formula;
• at this time, a robot coordinate is MK, that is, k=K;
• a vertical line of L1 is taken from point MK, and an obtained intersection point is an estimated value BK of current position of the robot;
• estimated values of the attitude is {BK, {circumflex over (θ)}K};
• a path update scale coefficient is assumed to be α, first rounded αK points in the set M are discarded, thereafter, (K-αK) points are updated to obtain a new set M′{MαK+1, MαK+2, . . . MαK+K} to be fit to obtain a line segment L2;
• wherein, for a point set B{M1, B1, B2, . . . , BP}, M1 and BP are estimated values of starting point and current point;
• P+1 is a number of points in the point set B;
• in order to allow a curve to be continuous and local, a B-spline curve is used to draw the motion trajectory of the robot, which is used to give a mapping of detection data in a movement;
• a previous path point of the robot is denoted as T, and a target path point is T′;
• according to a geometric relationship, a vertical deviation d of a path between a current path point BK and a path TT′ of the robot is calculated, and a direction deviation between a current direction and a path direction is γ;
• it is assumed that γmax is a maximum allowable direction deviation, and γmin is a minimum allowable direction deviation;
• dmax is a maximum allowable position error, and dmin is a minimum allowable position error;
• when γ<γmin and d<dmin, left and right drivers of the robot output a same rotational speed;
• when γ>γmax, and d<dmin, the direction deviation γ is input into a Proportion Integration Differentiation (PID) controller A as a control variable to correct a movement direction of the robot, and a speed ratio of left and right motors is proportional to an output of the controller until γ<γmin;
• when d>dmax, the vertical deviation d of the path is input into PID controller B as a control variable until d<dmin;
• if the coordinates of the robot are located in a circle in which a radius is a positioning error for many times in succession, it is judged that the robot has stopped due to manual operation or abnormal conditions, and path tracking stops.