Investigations of the design and performance of high-speed spring-loaded cam systems

This investigation of the design and performance of high-speed spring loaded cam systems attempts to relate the design technique to a more realistic model of the system. The testing of the validity of experimental and analytical results is also a requirement that has received particular attention. Where appropriate, experimental, analytical and design techniques are examined in a more general way. The starting point of this work is the author's study of pushrod operated valve gear in an automobile engine. Investigations have been continued on a variety of engines, all having the basic common factor of a controlling valve spring. The results are therefore particularly relevant to this class of system and appropriate to the types of motion controls required to operate automobile valves efficiently

Motion coordination and control in the development of a gait rehabilitation system

While most take their ability to walk for granted, some are unable to walk due to any number of pathologies, such as traumatic brain injury (TBI), spinal cord injury (SCI), and Parkinson\u27s disease. Decreased activity has been shown to be associated with rapidly deconditioning. Rehabilitation techniques that afford patients the ability to begin reconditioning through walking sooner may ultimately enhance their return to a better quality of life. To assist the functional recovery of such patients, an appropriate afferent input to the spinal cord will help in the therapy of the patient. Manual training is labor intensive, costly, and ergonomically unfavorable and tiring to the trainer, which will make training sessions short. Task-specific exercises delivered by robotic devices have registered success in reducing impairment and increasing motor power. Advantages of using robotic devices over the manual training include: reproducibility of the movement in a physiological manner, prolongation of the training sessions. However, several shortcomings exist in the existing devices. The reliability of the hardware and software is critical for their safe operation. These devices are expensive and only available in some large rehabilitation research institutions, which limit many disabled people to get the therapy they require. A gait pattern generation system was developed, which uses close-chain linkage mechanisms to guide the legs with coordinated movement of the leg joints to follow normal physiological gait pattern. The natural kinematics constraints of the mechanisms produce trajectories that limit the joints\u27 range of motion (ROM) thus improving the gait training safety. The movement of the input links of gait generation mechanisms must be controlled to provide proper timing of both stance and swing phases during a training session. This research describes the development of two methods for the motion control and coordination of the linkage mechanisms. First, the desired motion profile of the input crank of the linkage mechanism is obtained in the form of continuous function of time. The first method controls the input crank of the linkage mechanism directly with a servomotor based on the derived continuous motion profile. The coordination of the mechanisms for the two legs is carried out in the motion control software. The second method proposes to achieve both timing and coordination through mechanical means so that the system works under a simple speed control. A combination of cam and planetary gear mechanisms is synthesized for this approach. The procedures for obtaining the gears ratio of the planetary mechanism, the follower motion profile and the cam profile of the cam mechanism are discussed. Computer simulation is used to demonstrate the correct timing of the ankle movements on the closed path with the two methods. It also shows that the corresponding hip and knee joints follow normal physiological gait pattern

Vision technology/algorithms for space robotics applications

The thrust of automation and robotics for space applications has been proposed for increased productivity, improved reliability, increased flexibility, higher safety, and for the performance of automating time-consuming tasks, increasing productivity/performance of crew-accomplished tasks, and performing tasks beyond the capability of the crew. This paper provides a review of efforts currently in progress in the area of robotic vision. Both systems and algorithms are discussed. The evolution of future vision/sensing is projected to include the fusion of multisensors ranging from microwave to optical with multimode capability to include position, attitude, recognition, and motion parameters. The key feature of the overall system design will be small size and weight, fast signal processing, robust algorithms, and accurate parameter determination. These aspects of vision/sensing are also discussed

Nonlinear System Modeling, Optimal Cam Design, and Advanced System Control for an Electromechanical Engine Valve Drive

A cam-based shear force-actuated electromechanical valve drive system offering variable valve timing in internal combustion engines was previously proposed and demonstrated. To transform this concept into a competitive commercial product, several major challenges need to addressed, including the reduction of power consumption, transition time, and size. As shown in this paper, by using nonlinear system modeling, optimizing cam design, and exploring different control strategies, the power consumption has been reduced from 140 to 49 W (65%), the transition time has been decreased from 3.3 to 2.7 ms (18%), and the actuator torque requirement has been cut from 1.33 to 0.30 N·m (77%).Sheila and Emanuel Landsman Foundatio

An approach for smooth trajectory planning of high-speed pick-and-place parallel robots using quintic B-splines

This paper presents a new, highly effective approach for optimal smooth trajectory planning of high-speed pick-and-place parallel robots. The pick-and-place path is decomposed into two orthogonal coordinate axes in the Cartesian space and quintic B-spline curves are used to generate the motion profile along each axis for achieving C4-continuity. By using symmetrical properties of the geometric path defined, the proposed motion profile becomes essentially dominated by two key factors, representing the ratios of the time intervals for the end-effector to move from the initial point to the adjacent virtual and/or the via-points on the path. These two factors can then be determined by maximizing a weighted sum of two normalized single-objective functions and expressed by curve fitting as functions of the width/height ratio of the pick-and-place path, so allowing them to be stored in a look-up table to enable real-time implementation. Experimental results on a 4-DOF SCARA type parallel robot show that the residual vibration of the end-effector can be substantially reduced thanks to the very continuous and smooth joint torques obtained

MUSME 2011 4 th International Symposium on Multibody Systems and Mechatronics

El libro de actas recoge las aportaciones de los autores a través de los correspondientes artículos a la Dinámica de Sistemas Multicuerpo y la Mecatrónica (Musme). Estas disciplinas se han convertido en una importante herramienta para diseñar máquinas, analizar prototipos virtuales y realizar análisis CAD sobre complejos sistemas mecánicos articulados multicuerpo. La dinámica de sistemas multicuerpo comprende un gran número de aspectos que incluyen la mecánica, dinámica estructural, matemáticas aplicadas, métodos de control, ciencia de los ordenadores y mecatrónica. Los artículos recogidos en el libro de actas están relacionados con alguno de los siguientes tópicos del congreso: Análisis y síntesis de mecanismos ; Diseño de algoritmos para sistemas mecatrónicos ; Procedimientos de simulación y resultados ; Prototipos y rendimiento ; Robots y micromáquinas ; Validaciones experimentales ; Teoría de simulación mecatrónica ; Sistemas mecatrónicos ; Control de sistemas mecatrónicosUniversitat Politècnica de València (2011). MUSME 2011 4 th International Symposium on Multibody Systems and Mechatronics. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/13224Archivo delegad