Search results

With the development of automation technology, the accuracy, bearing capacity and self-adaptation requirements of wheeled mobile robots are more and more demanding under various complex conditions, which will urge designers such shortcomings as the low accuracy, poor flexibility and weak obstacle crossing ability of traditional heavy haul vehicles and improve the wear resistance and bearing capacity of traditional omnidirectional wheels.

The optimal configuration for heavy payload transportation is obtained by building sliding friction consumption model of traditional wheels with different driving types based on Hertz tangential contact theory. The heavy payload omnidirectional wheel with a double-wheel steering and a coupled differential wheel driving is designed with the optimal configuration. The wheel consists of a differential gear train unit and a nonindependent suspension unit. Kinematics model of the wheel is established and relative parameters are optimized.

The prototype experiments show that the wheel has higher motion accuracy and environment adaptability. The results are consistent with the theoretical calculation, which show that the accuracy is more than 50% higher than that of differential prototype. The motion stability and the accuracy of the coupled differential omnidirectional wheel are better than those of the traditional omnidirectional wheels during the moving and obstacle crossing process under complex conditions, which verifies the correctness and advantages of the design.

Aiming at the specific application of heavy payload omnidirectional transportation, a new omnidirectional mobile mechanism with a two-wheel coupling drive structure and an adaptive mechanism is proposed. The simulation and experimental results show that it can realize the high-precision heavy-load omnidirectional movement, the effective contact with the ground and improve the adaptability to the rugged ground. It is flexible, simple and modular and can be widely applied to transportation, exploration, detection and other related industrial fields.

THE DESIGN and manufacture of the complete flap and slat operating systems and of the tailplane actuator for the A300B Airbus is being undertaken by H. M. Hobson Ltd (now absorbed within the Hydro‐mechanical Products Group of the newly formed Company, Lucas Aerospace Ltd).

THE Trident IE fuel system, designed to operate on cither kerosene or JP.4, has a straightforward layout with few controls. Five integral tanks (FIG. 1), comprising four in the wings and one in the centre section, give a total of 5,880 Imp. gall, of which 2,000 Imp. gall, are contained in the centre tank. (Total fuel capacity of the Trident 1C is 4,960 Imp. gall, with 1,160 Imp. gall, in the centre tank.) Each wing inner tank has slightly more than twice the capacity of the outer.

A cowl for an air‐cooled aircraft engine comprising a series of rearwardly‐extending plate‐like flaps entirely separate from the cowl, a pair of rearwardly‐extending arms associated with each flap one at each margin thereof, a pair of longitudinal flanges on the side of each arm adjacent the flap so as to form a groove between them of which grooves at least one is of greater width than the thickness of the margin of the flap which can thus slide in at least one of said grooves, said margins being supported within said grooves, the circumferential distance between the flanges on one arm and the flanges on the other arm being substantially less than the corresponding dimension of the flap at all operating positions of the arms and the circumferential distance between the base of the groove on one arm and the base of the groove on the other arm being greater than the corresponding dimension of the flap, whereby the flap is supported solely by the arms at all operating positions thereof despite its being entirely separate from the cowl, a pivot for each arm lying along an axis at right‐angles to a fore‐and‐aft central plane, and driving mechanism carried by a fixed part of the cowl and operatively connected to each said arm to rotate it about said pivotal axis.

In an aeroplane, a control column comprising a grip member, a base member, and a cutaway member provided with slots, said base member being movably mounted in said slots.

THE MRCA head up display incorporates a camera recorder, fig J, which is mounted directly on the pilot's display unit, and is used to provide a film record of the HUD symbology superimposed on the pilot's view of the outside world.

THE electrical supply system is designed to provide both 200 volt a.c. and 28 volt d.c. services for operation of the aircraft. Although electrical power is required for the operation of the auto‐stabiliser system, this is not essential for flight and the flying controls are non‐electric. The aircraft does not therefore, depend on the integrity of the electrical system for flight. Loads, such as undercarriage lowering selection etc., required to operate if a total generation failure has occurred, are all d.c. and are fed by the main aircraft batteries. As a further precaution basic flight and communication facilities can also be powered in an emergency from a standby battery which is not charged in flight and is therefore independent of any of the normal aircraft services.

The DC‐9 Super 80 will be delivered with advanced avionics in early 1980. This paper discusses from the aircraft manufacturer's point of view the avionics system architecture, its digital implementation, and some hardware details of most major system elements. New operational features are discussed including Category IIIa autoland, some new autopilot and autothrottle cruise modes, a head‐up display system, and a “hot on‐board spare” flight guidance computer. Finally, some of the advantages of the digital system over analog systems are noted.

The analysis of power flow and mechanical efficiency constitutes an important phase in the design and analysis of gear mechanisms. The aim of this paper is to present a systematic procedure for the determination of power flow and mechanical efficiency of epicyclic-type transmission mechanisms.

A novel epicyclic-type in-hub bicycle transmission, which is a split-power type transmission composed of two transmission units and one differential unit, and its clutching sequence table are introduced first. By using the concept of fundamental circuits, the procedure for calculating the angular speed of each link, the ideal torque and power flow of each link, the actual torque and power flow of each link determined by considering gear-mesh losses, and the mechanical efficiency of the transmission mechanism is proposed in a simple, straightforward manner. The mechanical efficiency analysis of epicyclic-type gear mechanisms is largely simplified to overcome tedious and complicated processes of traditionally methods.

An analysis of the mechanical efficiency of a four-speed automotive automatic transmission completed by Hsu and Huang is used as an example to illustrate the utility and validity of the proposed procedure. The power flow and mechanical efficiency of the presented 16-speed in-hub bicycle transmission are computed, and the power recirculation inside the transmission mechanism at each speed is detected based on the power flow diagram. When power recirculation occurs, the mechanical efficiency of the gear mechanism at the related speed reduces. The mechanical efficiency of this in-hub bicycle transmission is more than 96 percent for each speed. Such an in-hub bicycle transmission possesses reasonable kinematics and high mechanical efficiency and is therefore suitable for further embodiment design and detail design.

The proposed approach is suitable for the mechanical efficiency analysis of all kinds of complicated epicyclic-type transmissions with any number of degrees of freedom and facilitates a less-tedious process of determining mechanical efficiency. It is a useful tool for mechanical engineering designers to evaluate the efficiency performance of the gear mechanism before actually fabricating a prototype as well as measuring the numerical data. It also helps engineering designers to cautiously select feasible gear mechanisms to avoid those configurations with power recirculation in the preliminary design stage which may significantly reduce the time for developing novel in-hub bicycle transmissions.

The purpose of this paper is to propose an improved method which can shorten the calculation time and improve the calculation efficiency under the premise of ensuring the calculation accuracy for calculating the response of dynamic systems with periodic time-varying characteristics.

An improved method is proposed based on Runge–Kutta method according to the composition characteristics of the state space matrix and the external load vector formed by the reduction of the dynamic equation of the periodic time-varying system. The recursive scheme of the holistic matrix of the system using the Runge–Kutta method is improved to be the sub-block matrix that is divided into the upper and lower parts to reduce the calculation steps and the occupied computer memory.

The calculation time consumption is reduced to a certain extent about 10–35% by changing the synthesis method of the time-varying matrix of the dynamics system, and the method proposed of paper consumes 43–75% less calculation time in total than the original Runge–Kutta method without affecting the calculation accuracy. When the ode45 command that implements the Runge–Kutta method in the MATLAB software used to solve the system dynamics equation include the time variable which cannot provide its specific analytic function form, so the time variable value corresponding to the solution time needs to be determined by the interpolation method, which causes the calculation efficiency of the ode45 command to be substantially reduced.

The proposed method can be applied to solve dynamic systems with periodic time-varying characteristics, and can consume less calculation time than the original Runge–Kutta method without affecting the calculation accuracy, especially the superiority of the improved method of this paper can be better demonstrated when the degree of freedom of the periodic time-varying dynamics system is greater.