Research On Measurement Method Of Rigid Body Dynamic Pose Parameters Based On Monocular High Speed Camera

A large number of mechanical systems in paddy field machinery can be reduced to multi-body systems.With the improvement of dynamic performance requirements of mechanical system products in farm operation,dynamic modeling and validation of complex mechanical system are needed.In order to validate the dynamic model of multi-body system,it is often necessary to measure the dynamic motion parameters of the rigid body of the mechanical system,including the position(velocity,acceleration)of the points and the attitude angle(angular velocity,angular acceleration)of the rigid body.As a non-contact pose measurement method,vision pose measurement technology has the advantages of simple structure,convenient measurement and high measurement accuracy.However,the price of vision measurement equipment on the market is also expensive.Especially for the parameter measurement of multi camera,it needs high-precision calibration equipment to complete the stereo calibration.The calibration process is tedious,and each measurement needs to be calibrated to increase the measurement Difficulty.In addition,the coordinate system of the camera is generally used as the reference system to measure the relevant parameters in the vision measuring equipment,so that the measurement results are not comparable due to the camera position changes.In view of the above problems,the main research contents of this paper include the following aspects:(1)Research on the measurement method of pose parameters of monocular high speed camera.Aiming at the problem of complicated calibration,expensive price and comparability of each measurement,this paper presents a method of absolute pose parameter measurement of moving rigid body realized by monocular camera.This method does not need to be calibrated beforehand.By using more than six non-coplanar control points symmetrically arranged in the rigid body coordinate system and the world coordinate system,the rotation matrix and translation matrix between the camera and the two coordinate systems can be measured,and the absolute pose measurement of the rigid body can be realized.In this paper,the absolute pose measurement formula of moving rigid body is deduced systematically,and the complete algorithm implementation steps are given.(2)Research on identification method of control points.In the aspect of control point recognition,the pixel coordinates of the starting image are determined first.The method is to identify the pixel coordinates of the clearly marked points first,then use the clearly marked points to narrow the scanning range,and finally determine all the marked points;then use the method of artificial search area to dynamically determine the pixel coordinates of the marked points,which can reduce the recognition error rate on the premise of ensuring the recognition speed.(3)The measurement method of absolute pose parameters of moving rigid body realized by monocular camera is tested and verified.Through static contrast experiments of different attitude measurement methods,it is found that the accuracy of DLT measurement method is not much different from that of Zhang Zhengyou method,and it has more advantages in the case of inconvenient target installation.The experiment of dynamic measurement of rigid body attitude by monocular camera shows that the attitude angle error will increase with the increase of rigid body’s tilt relative to camera lens,and the average absolute attitude angle measured is absolute.The error is 0.8092 degrees and the standard deviation is 0.6623 degrees.The DLT method is insensitive to the measurement distance and can be repeated by measuring the rigid posture at different positions of the camera.Because the rigid posture measured is converted into world coordinates,the results obtained at any time are comparable.The comparison test between monocular camera and binocular camera shows that the DLT method is insensitive to the measurement distance.Monocular camera has more advantages than binocular camera in attitude angle measurement,and has little difference with binocular camera in coordinate measurement.The feasibility of DLT in pose measurement is proved by the above experiments.(4)Research on the application of monocular camera to measure the pose parameters of rigid body.Aiming at the verification of the dynamic model of the flat shovel and providing the basis for improving the control performance of the flat shovel,the application tests of the position and attitude parameters,angular velocity and angular acceleration of the flat shovel are designed.Two dynamic application tests of the flat shovel have proved that this method can realize the measurement of the position and attitude parameters of the moving rigid body on the flat shovel.The measurement results of the attitude angle and the position of the center of mass reflect that the movement amplitude of the second flat shovel is much larger than that of the first.The first center of mass has the maximum 2cm fluctuation in the x-axis and the y-axis direction,while the second center of mass has the18 cm range in the x-axis direction,There is a 5cm range change in Y-axis direction,and the second movement range in z-axis direction is more than 1cm larger than the first one,which indicates that the faster and larger the moving range of flat shovel is,the worse the stability of flat shovel is.This is in line with the actual movement of flat shovel,and provides a method guidance for the dynamic model simulation of flat shovel.Finally,the measurement of the angular velocity and acceleration of the rigid body is realized by using the pose parameters,which provides the method guidance for the next step of calculation and analysis of the vibration change and dynamic detailed analysis of the rigid body.