Inside and Outside Flank Alternate Meshing Silent Chain and Experimental Evaluation of Dynamic Performance

Abstract: A new silent chain with inside and outside flank alternating meshing mechanism and sprockets were designed, and the main technical parameters and structure type of the plate and sprocket profile were described. In order to verify the good meshing transmission performance of the new silent chain, we did the performance comparison test for inside and outside flank alternate meshing silent chain and the ANSI standard silent chain with regard to transverse displacement vibration and wear extension. The results show that the new silent chain transmits smoothly, with standard silent chain compared to significantly reduce vibration quantity of transverse displacement, and it has good wear resistance properties, which is much superior to the standard silent chain. The results also verify low impact characteristics of the new silent chain and the rationality of design method. Because of its special meshing mechanism and structure type of alternate load, the new silent chain reduces meshing impact, vibration and polygon effect when chain and sprocket meshes, and fundamentally improves silent chain transmission performance, then extends the life of the chain

Support polygon in the hybrid legged-wheeled CENTAURO robot: modelling and control

Search for the robot capable to perform well in the real-world has sparked an interest in the hybrid locomotion systems. The hybrid legged-wheeled robots combine the advantages of the standard legged and wheeled platforms by switching between the quick and efficient wheeled motion on the flat grounds and the more versatile legged mobility on the unstructured terrains. With the locomotion flexibility offered by the hybrid mobility and appropriate control tools, these systems have high potential to excel in practical applications adapting effectively to real-world during locomanipuation operations. In contrary to their standard well-studied counterparts, kinematics of this newer type of robotic platforms has not been fully understood yet. This gap may lead to unexpected results when the standard locomotion methods are applied to hybrid legged-wheeled robots. To better understand mobility of the hybrid legged-wheeled robots, the model that describes the support polygon of a general hybrid legged-wheeled robot as a function of the wheel angular velocities without assumptions on the robot kinematics or wheel camber angle is proposed and analysed in this thesis. Based on the analysis of the developed support polygon model, a robust omnidirectional driving scheme has been designed. A continuous wheel motion is resolved through the Inverse Kinematics (IK) scheme, which generates robot motion compliant with the Non-Sliding Pure-Rolling (NSPR) condition. A higher-level scheme resolving a steering motion to comply with the non-holonomic constraint and to tackle the structural singularity is proposed. To improve the robot performance in presence to the unpredicted circumstances, the IK scheme has been enhanced with the introduction of a new reactive support polygon adaptation task. To this end, a novel quadratic programming task has been designed to push the system Support Polygon Vertices (SPVs) away from the robot Centre of Mass (CoM), while respecting the leg workspace limits. The proposed task has been expressed through the developed SPV model to account for the hardware limits. The omnidirectional driving and reactive control schemes have been verified in the simulation and hardware experiments. To that end, the simulator for the CENTAURO robot that models the actuation dynamics and the software framework for the locomotion research have been developed

The 15th Aerospace Mechanisms Symposium

Technological areas covered include: aerospace propulsion; aerodynamic devices; crew safety; space vehicle control; spacecraft deployment, positioning, and pointing; deployable antennas/reflectors; and large space structures. Devices for payload deployment, payload retention, and crew extravehicular activities on the space shuttle orbiter are also described

Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

A basis for the representation, manufacturing tool path generation and scanning measurement of smooth freeform surfaces

Freeform surfaces find wide application, particularly in optics, from unique single-surface science programmes to mobile phone lenses manufactured in billions. This thesis presents research into the mathematical and algorithmic basis for the generation and measurement of smooth freeform surfaces. Two globally significant cases are reported: 1) research in this thesis created prototype segments for the world’s largest telescope; 2) research in this thesis made surfaces underpinning the redefinition of one of the seven SI base units – the kelvin - and also what will be the newly (and permanently) defined value for the Boltzmann constant. Theresearchdemonstratestwounderlyingphilosophiesofprecisionengineering, the critical roles of determinism and of precision measurement in precise manufacturing. The thesis presents methods, and reports their implementation, for the manufacture of freeform surfaces through a comprehensive strategy for tool path generation using minimum axis-count ultra-precision machine tools. In the context of freeform surface machining, the advantages of deterministic motion performance of three-axis machines are brought to bear through a novel treatment of the mathematics of variable contact point geometry. This is applied to ultra-precision diamond turning and ultra-precision large optics grinding with the Cranfield Box machine. New techniques in freeform surface representation, tool path generation, freeform tool shape representation and error compensation are presented. A comprehensive technique for very high spatial resolution CMM areal scanning of freeform surfaces is presented, with a new treatment of contact error removal, achieving interferometer-equivalent surface representation, with 1,000,000+ points and sub-200 nm rms noise without the use of any low-pass filtering

Mechanical advantaged single drum vibratory roller earth compactor design for rural road construction, maintenance & upgrading within S.A.

Abstract: “Rural South Africa is characterised by poor infrastructure, large distances, dispersed demand and low incomes. There are also historical backlogs in service delivery, rural people also have poor access to basic social services and the economic mainstream [1].” Rural areas in South Africa are in need of better services regarding their existing infrastructure and maintenance. Some services includes the building, upgrading and maintenance of roads [1]. These roads have to be cost effective and yet efficient enough to carry the loads and traffic of vehicles that will use these roads. Roads are the backbone of rural well-being and advances rural economy in many ways. Without proper roads, accessibility becomes a huge problem and thus the rural economy suffers. Road building is subjective to many types of road construction machinery. These machines are used at various stages of the road construction process. Due to budget constraints that local municipalities encounter in rural areas, expensive machinery to build and maintain these roads are difficult or in some cases almost impossible to purchase. To alleviate the constraints rural budgets are facing, a fresh look has to be taken on the cost of road construction machinery. In this dissertation, focus is placed on the compaction part of the earth road building process and the ultimate design of a towed road roller...M.Tech. (Mechanical Engineering