Machine Learning Based Approach to a Crane Load Estimation

In the presence of increasing demands for safety and efficiency of material handling systems, the development of advanced supervisory control, monitoring, data acquisition and diagnostic systems is involved, especially for large industrial cranes. The important part of such systems is the continuous monitoring of a crane load. The crane load monitoring system proposed in the paper is based on a fuzzy model that estimates a payload mass transferred by a crane based on measuring the crane girder deflection and trolley position. The model was identified using the fuzzy subtractive clustering and least mean square with the data collected during experiments carried out on the laboratory scaled overhead crane.

Estimating the oscillation frequency of a payload mass on quadcopter in non-autonomous flight

Unmanned aerial vehicles (UAVs) have been employed in several engineering applications, such as aerial photography, environmental surveillance, delivery tasks, and others. Most of these applications have attracted increasing attention due to their ability to carry different payloads, which can change the dynamic of flight. The present article investigates the dynamics of a quadcopter with a payload mass including the stiffness of the attachment to the aerial vehicle. An approach to obtain non-dimensional equations of motion is introduced, and as a consequence, it is possible to determine the frequency of vibration of the payload mass during the flight. The results are presented for non-autonomous flight, and they establish a simple equation to estimate the oscillation frequency depending on the relation between the quadcopter and the payload masses, also considering the stiffness of attachment, without requiring a solution to the equation of motion in the time domain.

Design and Control of an Inflatable Spherical Robotic Arm for Pick and Place Applications

We present an inflatable soft robotic arm made of fabric that leverages state-of-the-art manufacturing techniques, leading to a robust and reliable manipulator. Three bellow-type actuators are used to control two rotational degrees of freedom, as well as the joint stiffness that is coupled to a longitudinal elongation of the movable link used to grasp objects. The design is motivated by a safety analysis based on first principles. It shows that the interaction forces during an unexpected collision are primarily caused by the attached payload mass, but can be reduced by a lightweight design of the robot arm. A control allocation strategy is employed that simplifies the modeling and control of the robot arm and we show that a particular property of the allocation strategy ensures equal usage of the actuators and valves. The modeling and control approach systematically incorporates the effect of changing joint stiffness and the presence of a payload mass. An investigation of the valve flow capacity reveals that a proper timescale separation between the pressure and arm dynamics is only given for sufficient flow capacity. Otherwise, the applied cascaded control approach can introduce oscillatory behavior, degrading the overall control performance. A closed form feed forward strategy is derived that compensates errors induced by the longitudinal elongation of the movable link and allows the realization of different object manipulation applications. In one of the applications, the robot arm hands an object over to a human, emphasizing the safety aspect of the soft robotic system. Thereby, the intrinsic compliance of the robot arm is leveraged to detect the time when the robot should release the object.

Development of automatic system for Unmanned Aerial Vehicle (UAV) motion control for mine conditions

Underground mining operations are connected with significant risks of technogenic accidents, which can be catastrophic. Mitigating the consequences of such phenomena directly depends on the reliability and efficiency of information about the state of parameters of many technological processes, mine workings and facilities located in them. At failure of standard systems of industrial telemetry in conditions of underground mining the creation of new information channels and places of information measurementbecomes practically impossible in case of emergency situation development. This predetermines necessity of use of essentially new systems of gathering and transfer of the information, based on robotized autonomous complexes. The task of acquiring reliable information about the situation in an emergency mine working with the help of drones (unmanned aerial vehicles or UAV) in order to make rational decisions in the course of the rescue operation is quite relevant. The aim of the paper was to develop a system of automatic control of an unmanned aerial vehicle (UAV) movement in confined space of a mine working, with significant perturbations of the mine air flow. The mathematical model of UAV movement in mine conditions, based on Euler angles or quaternions, was substantiated. The method of positioning through triangulation with the use of radio beacons was accepted as the basic method that allowed to determine the current position of an UAV. It was proposed to solve the problem of creation of the automatic system for an unmanned aerial vehicle movement control with the use of a hierarchical multiloop control system. The route planning algorithm was formed on the basis of the Dijkstra algorithm. For this purpose, discretization of the future motion space was performed, a labeled connected graph was constructed, on which the arc weights were the distances between the route points. A simulation experiment was implemented. The average deviation from the planned trajectory when flying at a speed of 10 m/s with payload mass up to 0.6 kg did not exceed 1 m, and the maximum deviation was unacceptably large. When flying at 6 m/s with payload mass up to 0.6 kg the average deviation did not exceed 0.3 m, and the maximum deviation, 1.2 m. The results of simulation of movement along the route towards the disturbing mine airflow showed that the control system allowed the UAV with payload of 0.6 kg to withstand the oncoming flow up to 8 m/s. It was obtained that with payload mass of 0.6 kg, the braking distance does not exceed 6 m if the UAV had a speed of 6 m/s, and the braking distance does not exceed 12 m at the speed of 10 m/s. The performed simulation studies confirmed the operating capability of the developed system for automatic motion control.

Damping Oscillation of Suspended Payload by Varying String Length

Many modern day applications involve transport of objects suspended through cables such as in overhead cranes or landing of rovers on the Martian surface. Any undesired oscillation of the payload has the potential risk of instability and the problem of damping such oscillation and stabilizing the payload at a desired length is the control objective of this paper. The system is modeled as a variable length pendulum (VLP) which comprises of a payload suspended via a string wrapped around a pulley. The length of the pendulum is varied using clockwise/counterclockwise rotation of the pulley through torque applied by a motor. For a known payload mass, a nonlinear control design is first presented that guarantees asymptotic stability of the desired equilibrium with limited state measurements. The design is then modified for it to handle significant uncertainty in payload mass. The effectiveness of both the designs are validated in simulations.

Design Optimization and Parameter Analysis of a Hybrid Rocket Motor-Powered Small LEO Launch Vehicle

In this paper, the effects of different grain shapes of a hybrid rocket motor (HRM) and different payload mass/orbit heights on the design of small launch vehicles (SLVs) are systematically discussed. An integrated overall design model for the hybrid rocket motor-powered small launch vehicle (HPSLV) is established, and two groups of three-stage SLVs capable of sending small payloads to the low earth orbit (LEO) are designed and optimized. In the first group, the SLVs with different grain shapes and different numbers of chambers in HRMs at the 1st and the 2nd stages are optimized and analyzed. In the second group, the SLVs capable of sending different payload mass to different orbit heights are optimized and analyzed. Pareto graphs of the design results show that the design of HRM at the 1st stage has the greatest impact on the take-off mass, total velocity increment, and maximum axial overload of the SLV. Self-organizing maps show that the take-off mass, maximum diameter, overall length, and velocity increment of the SLVs have the same variation tendency. For the 1-chamber HRM at the 1st stage, the wheel-shaped grain is better than circle-shaped and star-shaped grains in terms of reducing the total mass and length of the SLV, and the 4-chamber parallel HRM has more advantages over all 1-chamber designs for the same reason. The theoretical velocity increments are calculated by the Tsiolkovsky formula, and the actual velocity increments are obtained based on the trajectory simulation data. The results indicate that the HPSLV has a regular distribution in terms of the ratio of theoretical (actual) velocity increments at three different stages, and the estimated distribution ratio is around 1 : 1.55 : 1.69 (1 : 1.9 : 2.39), which can provide some reference for future development of HPSLV.

Sway and Disturbance Rejection Control for Varying Rope Tower Cranes Suffering from Friction and Unknown Payload Mass

Tower cranes are well-known underactuated systems, where the design of controllers for them with time-varying rope length was weak in the past because of their complex dynamic characteristic. The payload oscillation will become worse when the jib slew angle, the trolley position and the rope length are changed simultaneously. The proposed method is designed based on robust adaptive sliding mode control via tracking non-zero initial reference trajectories, in which, frictions and lumped disturbances in the crane system are eliminated, as well as unknown payload mass is effectively estimated online. Lyapunov technique is combined with LaSalle's invariance theorem to design controller and analyze stability. Various and strict simulations are applied, which validate the effectiveness and extreme robustness of the proposed method.

A completely reusable aerospace system based on subsonic carrier with the return of the first stages to the starting point

The concept of aerospace system based on air launch from subsonic twin-fuselage aircraft and the rocket launch into orbit is investigated. The scheme of aerospace system trajectory providing a return to the starting point both of the carrier and the first rocket stage with liquid-fuel motors is proposed. It was shown that the use of subsonic carrier as a launching platform of the rocket system increases the payload mass by 1.2% of the rocket segment MTOW as compared to autonomous ground take-off. The comparative analysis of three versions of carrier aircraft and three fuel options at the first rocket stage was carried out. Analysis showed that compared to kerosene variant the hydrogen hypersonic booster makes it possible to significantly increase the payload mass while the launching costs stay the same.