Design and experiment of variable rate orchard sprayer based on laser scanning sensor

During different growth periods,canopy size and density in orchards are variable,which need application conditions(flow rate and air flow)to be adjusted to match the canopy’s characteristics.In order to improve orchard sprayer’s automatic operating performance,an automatic variable-rate orchard sprayer(VARS)fixed with 40 electromagnetic valves and 8 brushless fans was developed based on the canopy’s spatial dimensions.Each solenoid valve and brushless motor can be individually adjusted in real-time through pulse width modulation(PWM)signals emitted by a control system to adjust each nozzle’s spout and fan rotation speed.A high-precision laser scanning sensor(light detecting and ranging,LIDAR)was adopted as the detector to measure the canopy volume using the variable rate algorithm principle.Field experiments were conducted in an apple orchard,and conventional air blast sprayer(CABS)and directed air-jet sprayer(DAJS)were tested as a comparison.Results showed that on average,46%less spraying solution was applied compared to conventional applications,while penetration rate was similar to DAJS.Normalized deposition in the canopy with variable application was higher than that of conventional applications,indicating that electronic sprayers are more efficient than conventional sprayers.It was also observed that VARS could significantly reduce off-target loss.The field experiment showed that the newly developed variable-rate sprayer can greatly reduce pesticide use and protect the environment for the orchard fruit production,and also provide a reference for design and performance optimization for plant protection machinery.

A Rapid Calibration Technique for Scanning Line-Structured Laser Sensor

A novel procedure to calibrate the scanning line-structured laser sensor is presented. A drone composed of two orthogonal planes is designed, with the result that camera parameters and light-plane equation parameters is achieved simultaneously.

Extrinsic calibration of a laser displacement sensor in a non-contact coordinate measuring machine

In order to implement 3D scanning of those complicated parts such as blades in the aviation field,a non-contact optical measuring system is established in the paper,which integrates a laser displacement sensor,a probe head,the frame of a coordinate measuring machine（CMM）,etc.As the output of the laser sensor directly obtained possesses the 1D length of the laser beam,it needs to determine the unit direction vector of the laser beam denoted as（l,m,n）by calibration so as to convert the 1D values into 3D coordinates of target points.Therefore,an extrinsic calibration method based on a standard sphere is proposed to accomplish this task in the paper.During the calibration procedure,the laser sensor moves along with the motion of the CMM and gathers the required data on the spherical surface.Then,both the output of the laser sensor and the grating readings of the CMM are substituted into the constraint equation of the spherical surface,in which an over-determined nonlinear equation group containing unknown parameters is established.For the purpose of solving the equation group,a method based on non-linear least squares optimization is put forward.Finally,the system after calibration is utilized to measure the diameter of a metallic sphere 10 times from different orientations to verify the calibration accuracy.In the experiment,the errors between the measured results and the true values are all smaller than 0.03 mm,which manifests the validity and practicality of the extrinsic calibration method presented in the paper.