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MUCH time and money have been devoted to the development of the helicopter, but the achievement of a practical machine is apparently not yet in sight. Some of the problems, indeed, have been solved; others await solution. In any discussion of the helicopter the subject naturally divides itself into five headings. First, there is the problem of the provision of adequate lift. This has for many years been solved, and an airscrew can now be designed that will give its predicted lift with a certain degree of confidence. On the practical side, helicopters have demonstrated that they can be built with a sufficiently light structure weight that modern power plants are adequate to lift the aircraft vertically upwards. The problem has also been investigated theoretically, and a relationship between disc loading and pounds per horse power established which should permit of any designer producing a helicopter that will lift itself. This fact cannot be too strongly emphasised in view of the fact that many inventors consider that the major problem is one of lift.

Vertical take-off is commonly adopted in most insect-mimicking flapping-wing micro air vehicles (FMAV) while insects also adopt horizontal take-off from the ground. The purpose of this paper is to study how insects adjust their attitude in such a short time during horizontal take-off by means of designing and testing an FMAV based on stroke plane modulation.

An FMAV prototype based on stroke plane rotating modulation is built to test the flight performance during horizontal take-off. Dynamic gain and decoupling mixer is added to compensate for the nonlinearity during the rotation angle of the stroke plane getting too large at the beginning of take-off. Force/torque test based on a six-axis sensor validates the change of aerodynamic force and torque at different rotation angles. High-speed camera and motion capture system test the flight performance of horizontal take-off.

Stroke plane modulation can provide a great initial pitch toque for FMAV to realize horizontal take-off. But the large range of rotation angles causes nonlinearity and coupling of roll and yaw. A dynamic gain and a mixer are added in the controller, and the FMAV successfully achieves horizontally taking off in less than 1 s.

The research in this paper shows stroke plane modulation is suitable for insect’s horizontal take-off

Aiming at the unbalancing problem of the neutral equilibrium characteristic for balance hoist in the loading process, the purpose of this paper is to establish a dynamic equation for multi-body using the Lagrange method. It is not difficult to find that the deformation of the boom system has a great influence on the stability of the whole system, through the simulation analysis of the multi-rigid-body system model.

Aiming at the unbalancing problem of the neutral equilibrium characteristic for balance hoist in the loading process, the dynamic equation for multi-body is established by Lagrange method. It is not difficult to find that the deformation of the boom system has a great influence on the stability of the whole system, through the simulation analysis of the multi-rigid-body system model.

Result shows that different weights have a great influence on the force deformation and vibration of the boom system of balance hoist. With the increase in lifting weight, the force and deformation of the boom system increase; lead to balance hoist unique with characteristics of indifferent equilibrium, proportional amplification, labor-saving operation will be lost, easy to cause the imbalance of balance hoist. Therefore, the appropriate increase in the basic length of the compression bar, reduction in the basic length of the tension rod and the increase stiffness of the boom system can improve the stability of balance hoist, which provides a reference for the optimization and manufacture of the balance hoist structure.

The simulation model was established by analyzing the working principle and the load condition of the balance hoist, and the simulation and dynamic characteristics of three typical working conditions are analyzed by using ADAMS; result shows that different weights have a great influence on the force deformation and vibration of the boom system of balance hoist. With the increase in lifting weight, the force and deformation of a boom system increase, lead to balance hoist unique with characteristics of indifferent equilibrium, proportional amplification, labor-saving operation will be lost, easy to cause the imbalance of balance hoist.

SINCE man first aspired to fly the desire to take‐off and land vertically and to hover in flight has always presented a challenge to the engineer. To date only the rotary wing aircraft has achieved these aims in service but their shortcomings in terms of speed, range and economy have encouraged engineers to search for more elegant ways of achieving vertical flight.

In recent years little has been published on the mathematical theory of vertical flight, though more intelligent work is being done on the subject by various engineers than, probably, at any previous time. In this and a following article, to be published next month, one of the leading exponents of the helicopter, in a specialised and highly ingenious form, covers the whole field of sustentation, ascent, descent and the thorny problem of stability more completely than has ever hitherto been attempted

This paper deals with the estimation of the necessary masses of propulsion components for multirotor UAS. Originally, within the design process of multirotors, this is an iterative problem, as the propulsion masses contribute to the total takeoff mass. Hence, they influence themselves and cannot be directly calculated. The paper aims to estimate the needed propulsion masses with respect to the requested thrust because of payload, airframe weight and drag forces and with respect to the requested flight time.

Analogue to the well-established design synthesis of airplanes, statistical data of existing electrical motors, propellers and rechargeable batteries are evaluated and analyzed. Applying Rankine and Froude’s momentum theory and a generic model for electro motor efficiency factors on the statistical performance data provides correlations between requested performance and, therefore, needed propulsion masses. These correlations are evaluated and analyzed in the scope of buoyant-vertical-thrusted hybrid UAS.

This paper provides a generic mathematical propulsion model. For given payloads, airframe structure weights and a requested flight time, appropriate motor, propeller and battery masses can be modelled that will provide appropriate thrust to lift payload, airframe and the propulsion unit itself over a requested flight time.

The model takes into account a number of motors of four and is valid for the category of nano and small UAS.

The presented propulsion model enables a full numerical design process for vertical thrusted UAS. Hence, it is the precondition for design optimization and more efficient UAS.

The propulsion model is unique and it is valid for pure multirotor as well as for hybrid UAS too.

(1) An aircraft in steady, straight‐line motion can have no resultant force or couple acting upon it. This condition is never continuously maintained in flight, and the craft proceeds in a series of oscillations or wide, corrected curves. Continuous adjustment takes place in the direction of its flight through either an inherent stability or a judicious use of the controls by the pilot, but the motion may be regarded mostly without error as steady for purposes of design. Calculations carried out on the basis of steady equilibrium have for objects the determination of optimum lay‐out; the selection of most suitable component parts; the provision of adequate and easeful control; the specification of loading for strength design; and the prediction and testing of performance. In practice, such calculations go hand in hand with others concerned with statical and dynamical stability; with accel‐erated motions; with strength and weight; and with a host of purely practical considerations. Deductions drawn from the principles discussed in this Article may not be decisive in a given case till set in proper perspective. In this connection we note, without straying from our subject matter, that many secondary factors are here neglected, whose effect the engineer has, on occasion, to take carefully into account.

IN a departure from usual practice this issue concentrates to a large extent upon a single subject — Mechanical Handling. It coincides with that industry's exhibition at Earls Court from the 9th to 19th of this month, to be opened by the Rt. Hon. Christopher Chataway, M.P., Minister for Industrial Development. In consequence it was necessary to defer some regular features for a time, for which we apologise.

Prefabricated building has been widely applied in the construction industry all over the world, which can significantly reduce labor consumption and improve construction efficiency compared with conventional approaches. During the construction of prefabricated buildings, the overall efficiency largely depends on the lifting sequence and path of each prefabricated component. To improve the efficiency and safety of the lifting process, this study proposes a framework for automatically optimizing the lifting path of prefabricated building components using building information modeling (BIM), improved 3D-A* and a physic-informed genetic algorithm (GA).

Firstly, the industry foundation class (IFC) schema for prefabricated buildings is established to enrich the semantic information of BIM. After extracting corresponding component attributes from BIM, the models of typical prefabricated components and their slings are simplified. Further, the slings and elements’ rotations are considered to build a safety bounding box. Secondly, an efficient 3D-A* is proposed for element path planning by integrating both safety factors and variable step size. Finally, an efficient GA is designed to obtain the optimal lifting sequence that satisfies physical constraints.

The proposed optimization framework is validated in a physics engine with a pilot project, which enables better understanding. The results show that the framework can intuitively and automatically generate the optimal lifting path for each type of prefabricated building component. Compared with traditional algorithms, the improved path planning algorithm significantly reduces the number of nodes computed by 91.48%, resulting in a notable decrease in search time by 75.68%.

In this study, a prefabricated component path planning framework based on the improved A* algorithm and GA is proposed for the first time. In addition, this study proposes a safety-bounding box that considers the effects of torsion and slinging of components during lifting. The semantic information of IFC for component lifting is enriched by taking into account lifting data such as binding positions, lifting methods, lifting angles and lifting offsets.

The solution of the problem of estimating the take‐off distance to a height of 50 feet has to a certain extent been limited by the absence of a theoretical analysis of the airborne part of the take‐off manoeuvre. The three main physical quantities associated with the motion immediately after an aircraft leaves the ground are aircraft speed, the angle the flight path makes with the horizontal and the lift coefficient increment. This latter quantity is the lift coefficient in excess of that required for level flight at the unstick speed, and is produced when the pilot pulls the stick quickly back at take‐off. A linear theoretical analysis is obtained by assuming that variations of the physical quantities already mentioned are small enough for squares and higher powers of such variations to be neglected in comparison with the variations themselves. The results of the analysis depend on the solutions of a pair of ordinary simultaneous linear differential equations with constant coefficients. If the aircraft speed never falls below the unstick speed, the limiting values of the lift coefficient increment which define the safe range of take‐offs can be determined. By considering the mean value of the lift coefficient increment over the safe range of take‐offs it is possible to define a mean safe take‐off, and for such a take‐off, the mean safe airborne distance from the unstick point to a height of 50 feet can be estimated. The application of the theory as a means of estimating the take‐off performance of a bomber aircraft is given as an example at the end of this work.