FEATURES OF USE OF RESCUE MODE IN BETAFLIGHT FIRMWARE FOR UAV ON THE BASIS OF STM32F405 CONTROLLER

The paper considers the practical possibility of implementing the GPS Rescue mode for Betaflight ver.4.1.1 firmware in order to return the quadrocopter (UAV) to a point close to the take-off point coordinates. In this regard, an experimental prototype was built with a 250mm frame, but with which the OMNIBUSF4V3 flight controller was installed based on the STM32F405 microcontroller with a GPS receiver and a directional video camera for FTP flights. Betaflight OSD was configured to receive flight data in order to analyze the correct operation of the copter return algorithm. During flight tests, it was shown that the GPS Rescue mode allows you to return the UAV to the launch zone, subject to the settings presented in the work on the assembled quadcopter. When performing GPS Rescue mode, an important condition is the stable connection of the GPS receiver with the number of satellites not less than those installed when setting the firmware. If the number of satellites becomes less than the set, then within a few seconds the motors turn off and the copter falls. It is shown that for stable operation of the GPS Rescue mode, the copter during flight should use the stabilization mode (Angle) with the accelerometer turned on, perform a flight with small angles of inclination. It was found that the greater the angle of inclination of the coprera, the smaller the number of satellites the GPS receiver catches. Therefore, the GPS rescue mode is not advisable to use in Acro, 3D, Horizon flight modes when making flip-s. It has been practically established that the GPS Rescue mode is more appropriate to use in the event of a break in video communication with the heading camera (FPV flights) while maintaining communication with the control panel. In this case, the flight orientation is lost and the copter in automatic mode must be returned to the video communication zone. To do this, the control mode sets the stabilization mode (angle) and turns on the GPS Rescue mode. When establishing a video connection, determining the location, GPS Rescue mode is disabled from the remote control and the copter can continue flying via FPV. It was noticed that in case of communication failure with the control panel, GPS Rescue mode is automatically turned on. In this case, the copter returns to the starting point and in case of restoration of radio communication, the copter automatically restores control with the remote control. This moment must be monitored by the pilot, otherwise the copter may crash. Therefore, it is advisable in case of loss of communication to set the toggle switch on the control panel to GPS Rescue mode. Then, when the radio is restored, the copter will operate according to the GPS Rescue mode from the remote control and will automatically return to the start area and can be detected visually with subsequent control from the remote control.

The performance improvement of a lowcost INS/GPS integration system using the street return algorithm

During the last decades, MEMS technology has undergone rapidly development, leading to the successful fabrication of miniaturized mechanical structures integrated with microelectronic components. Accelerometers and gyroscopes are in great demand for specific applications ranging from guidance and stabilization of spacecraft to research on vibrations of Parkinson patient’s fingers. The demand of navigation and guidance has been urgent for many years. In fact, INS is used daily in flight dynamics control. Nowadays, with the strong growth of Microelectromechanical system (MEMS) technology, the Inertial Navigation Systems are applied widely. However, there are existing errors in the accelerometer and gyroscope signals that cause unacceptable drifts. Even when the Inertial Navigation System (INS) was supported by the Global Positioning System (GPS), the position error is still large, especially in the case of GPS signal lost. In this paper, we will present a simple algorithm called Street Return Algorithm(SRA) to reduce this kind of error. Experimental result showed that this algorithm could be applied in the real-time operation.

Computational Aspects of Elasto-Plastic Deformation in Polycrystalline Solids

The overall elasto-plastic behavior of single crystals is governed by individual slips on crystallographic planes, which occur when the resolved shear stress on a critical slip system reaches a certain maximum value. The challenge lies in identifying the activated slip systems for a given load increment since the process involves selection from a pool of linearly dependent slip systems. In this paper, we use an “ultimate algorithm” for the numerical integration of the elasto-plastic constitutive equation for single crystals. The term ultimate indicates exact integration of the elasto-plastic constitutive equation and explicit tracking of the sequence of slip system activation. We implement the algorithm into a finite element code and report the performance for polycrystals subjected to complicated loading paths including non-proportional and reverse/cyclic loading at different crystal orientations. It is shown that the ultimate algorithm is comparable to the widely used radial return algorithm for J2 plasticity in terms of global numerical stability.

Solver for Finite Element Analysis of Ring Rolling Process

A dynamic explicit finite element solver is developed for numerical simulation of metal ring rolling process, which is a complex process of material nonlinearity, geometric nonlinearity and contact nonlinearity. An elastro-plastic dynamic explicit finite element equation and central difference algorithm are used. To control hourglass, a stable matrix hourglass control method is used to ensure energy balance in the simulation. Two-step method of global search and local search is used to reduce the contact judging time. In the elastic-plastic stress updating, tangent forecasting and radical return algorithm are used to eliminate the stress deviate from the yield surface. The accuracy and stability of the solver is verified by comparison of two ring rolling processes with the experimental results.

A Radial Return Algorithm Application in Elastoplastic Frame Analysis Using Plastic Hinge Approach

A new method is presented for first-order elastoplastic analysis of framed structures using a radial return predictor/corrector solution strategy. The proposed method assumes plastic hinge formation coupled with a yield surface. The yield surface is defined as a general function of axial force, shear forces, twisting, and biaxial bending moments on the cross-section of the frame. The material is regarded as linear and elastic-perfect plastic. The plastic deformations are governed by the normality criterion. Combining the Newton-Raphson method and the radial return algorithm, a consistent tangent modular matrix is proposed and fast and converging algorithms are presented. Examples demonstrate the accuracy and effectiveness of the proposed method.