59 research outputs found
Theoretical Analysis of an Innovative Volumetric Rotary Machine
No full textIn this paper a study of an innovative volumetric rotary machine is presented . The machine consists in a stator and a number of pistons rotating inside the stator and attached to a crank. The mechanism realizes for every piston a chamber that varies its volume during crank rotation, and consequently it can be used to design a volumetric rotary machine. In order to obtain the analytical equation of the stator profile the geometrical constraints that characterize the mechanism are analyzed. Once the stator profile is determined and suitable design parameters settled, the profile of the rolling pistons is obtained numerically, considering their relative motion in respect to the stator. In order to evaluate the performance of the machine, the specific displacement and the maximum compression ratio are calculated as a function of the design parameters. Finally a basic dynamic analysis of the machine is presented. The results obtained permit to choose the design parameters for a particular application, showing that the mechanism can be particularly suitable for pumps, compressors and pneumatic engines
Sensitivity Performance of Input Shapers Applied to Command Profiles as Diagnostic Tool for Flexible Robots
No full textIn this paper the motion input pre-shaping method, applied to flexible manipulators for space applications, is analyzed in terms of sensitivity and robustness to parameters uncertainties. The special environment of space operations and the project specifications lead to the design of manipulators with light and flexible structures. In order to highlight the performances of these methods an open loop control technique was implemented. The control technique is verified with both numerical simulations and experiments. This paper presents the results of a series of experimental tests carried out on the Space Robot Simulator assembly, called Test-bed for Microgravity Simulation in Robotic Arm Dynamics (TeMSRAD) (Mimmi et al., 2004), which has been set up at the Dipartimento di Meccanica Strutturale, Università di Pavia. The innovative task of the research was to determine experimentally the sensitivity curve for One- Hump and Two-Hump Extra-Insensitive input shapers, for different vibration limits, by purposely introducing errors in the system model, in order to simulate typical operating conditions
Estimation of biomechanical parameters and propulsive efficiency of flat-water kayak single (K1) at race pace
No full textFlat-water Kayaking is an Olympic discipline in which the boats race are held on calm water in separate lanes delineated with ropes and buoys over the distance of 500 m and 1000 m. A new Sprint 200 m race will make its Olympic debut at London 2012. Few are the experimental data in literature on this particular type of race in which the athlete exerts his maximum effort on a very short distance.
This paper presents the analysis of the paddling performance of elite athletes in single K1 training session keeping up a typical stroke race cadence (over 100 spm). In order to reproduce the regatta conditions the tests were performed at Idroscalo water basin (Milan, Italy) with kayaker at the top of the training preparation. The on purpose experimental device, successfully tried out in previous on-water kayaking and canoeing researches was integrated with cardiopulmonary testing portable system. By means of experimental acquisitions including stroke forces, estimated position of the blade propulsion centre (EPPC), boat speed and the movements around the three main axes of the hull it is possible to evaluate the athletes performance during the different phases of the race. Particular attention was devoted to refine the efficiency of stroke through the analysis of the exertion of the force in the active part of paddling (drive phase) related to the metabolic cost of the stroke cycle.
The main goal of the research was to implement a low cost stand-alone instrumentation and acquisition system for the on-the-water measurement of biomechanical and dynamical parameters during race paddling of elite athletes to quantify performance and improve technique
Experimental analysis of paddling efficiency of elite and non-elite athletes with instrumented canoe sprint C1
No full textCanoeing is an on-water sport admitted by the International Canoe Federation (ICF) and Canoe Sprint became an Olympic discipline in 1936: its programme includes events over 200 m, 500 m and 1000 m. There are numerous Canoe events in single (C1), double (C2) and four (C4) boats. In this discipline the canoeist is kneeling on one knee, and uses a single-bladed flat paddle. In the same way as kayaking, canoeing is a sport whereby propulsion of the boat is derived mainly from muscle actions of the upper body. Conversely, the kneeling position of the canoeist influences the dynamic behaviour of the hull and the force stroke exerted by the single-bladed paddle results in augmented ‘fluctuation’ of the average speed, in greater roll angle and wider pitch span of the canoe with respect to the kayak boat. Besides, the flat shape of the paddle determines the particular paddling technique.
In canoeing high forces must be applied at high stroke rates and athletes are coached both in stroke technique and power or resistance training. Elite athletes stand out for the style and efficiency of the stroke, for power and resistance and for skills in the race strategy. Biomechanical measures of canoeing is an important asset to improve performance. In addition comparing results from test to test enables monitoring of an athlete's yearly, and year-to-year improvement. Finally, the experimental analysis of the main kinematical and dynamical parameters allows to examine the shape of the force curves for stroke error detection purposes and to reduce the ineffective hull movements. In this paper the performance and the paddling technique of two elite and two non-elite canoeists are presented by means of an on-water experimental apparatus. Moreover a comparison between the drive phase of the stroke in kayaking and canoeing is proposed.
The goals of this research project were to (1) develop a system for on-the-water measurement of paddling performance in kayaking and canoeing, (2) demonstrate the potential of such a system to quantify efficiency and then (3) compare the main kinematical and dynamical parameters of single K1 and C1 boats and the technique differences in paddling style
Lateral Force Components on Pedals measured by a Cycle Ergometer with Three Axial Load Cells
No full textThis paper is focused on the measurements and analysis of the three components of the force on pedals in bicycling through a special cycle-ergometer prototype [4]. This machine allows to study the kinematics and dynamics of the bycicle-riders by quantitative measurements.
The pedals are equipped with a three-axial load cells measuring the pedalling force in three orthogonal directions, and with two encoders measuring the angular positions of foots. A third encoder is mounted on the central movement, for the measurement of the crank rotation angle.
The ergometer, developed for cycling sport performances and for clinical analysis, allows to measure the lateral components on the pedals, perpendicular to the para-sagittal plane. Notwithstanding the literature usually neglects the lateral components in non pathological subjects, they represent meaningful informations in rehabilitation treatment of pathological subjects. Moreover the biomechanical analysis of pedalling through three-axial force measurements allows to improve efficiency during cycling sports
Theoretical and experimental sensitivity analysis of extra insensitive input shapers applied to open loop control of flexible arm
No full textIn this paper the motion input pre-shaping, applied to flexible manipulators for space applications, is analyzed in terms of sensitivity and robustness to parameters uncertainties. The special environment of space operations and the project specifications lead to the design of manipulators with light and flexible structures. In order to highlight the performances of these methods an open loop control technique is implemented. The control technique is verified by both numerical simulations and experiments. This paper presents the experimental set-up and the results of a series of experimental tests carried out on the Space Robot Simulator assembly, called Test-bed for Microgravity Simulation in Robotic Arm Dynamics (TeMSRAD). The innovative task of the research is to determine experimentally the sensitivity curve for One-Hump and Two-Hump Extra-Insensitive input shapers, for different vibration limits, by purposely introducin
An original 3-D cycle ergometer (3-DCE) for three-axial force measurements
No full textIn this paper is presented an original prototype of cycle ergometer suitable for measuring the three components of the force exerted by the two feet on the two pedals. The prototype is a cycle ergometer suitably instrumented to collect quantitative data that allow the kinematics and dynamics of the bicycle-rider model to be solved. A tri-axial load cell, which measures the pedalling force in three orthogonal directions, and two encoders, that measure the angles between the feet and the central movement, are mounted on each pedal. These angles are measured through encoders as well as the crank rotation of the central movement
On Twin Screw Compressors Design
No full textTwin screw compressors are widely used in many applications, such as compressing air, refrigerating, industrial gas processing, engines supercharging, etc. In the last quarter of the twentieth century the number of units manufactured registered an extraordinary increase: in fact the development of advanced manufacturing techniques permitted to exploit the basic advantages of these machines in respect to the other types of compressors. In particular twin screw compressors are characterized by the ability to satisfy varying load demands, reliability in service, high efficiency, simple maintenance.
Despite the diffusion of this type of machines in many industrial fields, the available literature about them is still limited, in particular regarding the rotor profile geometry. In fact, almost every industrial profile of the rotors is protected by patents, and the companies that hold them seldom diffuse information about the generating methods.
In this paper a general description of this type of machine is presented, focusing on the mechanical aspects and in particular on the shape of the rotors.
The first part of the paper introduces the main advantages and disadvantages in respect to the other compressor types and the state of the art of this type of machine. Then a deep mathematical analysis of a method for the profiling of screw compressor rotors, based on the theory of gearing, and typical aspects related to the machine design, such as the rotor flow area, the sealing line on the cross-sectional plane and on the rotors and the blow-hole area, are discussed.
In the second part of the work the theory above presented is applied to three different geometries of the rotors, and other possible more complex profiles are introduced
Evaluation of Paddling Performances through Force Acquisitions with a Specially Instrumented Kayak Ergometer
No full textThis paper presents a prototype machine working as a kayak ergometer, specially designed to closely reproduce the athletic performance during a training K1 indoor session. Drag and inertia actions on paddles are reproduced through a fan connected to the movement of the paddle-bar. The resistance action can be adjusted by regulating the air intake with a shutter, to compensate for size and weight of the paddler. Paddle action, simulated by an instrumented bar with strain gauges at both ends, pulls the rotating fan by means of ropes rolling up on pulleys. Load cells are mounted in correspondence of the bearings of the pulleys, and an encoder is mounted on the fan shaft to measure the rotational speed. This system is particularly suitable to evaluate the paddling performances and to refine the technique of strokes and style
Special Cycle-Ergometer to Optimize the Rider Position through Force Measurement
No full textThis paper presents an original 7-degrees of freedom device to analyze, test and optimize different positions of a bicycle rider. The system allows data acquisitions of forces, angles and velocities during cycling performance. An overall of eight forces and three angles are simultaneously measured.
An efficient position enables the rider to reduce the muscular effort for a given power produced. Basically good bike position presents three general parameters: saddle height, saddle-to-bar distance, and fore/aft saddle position. Determining the correct horizontal saddle position is of relevant importance in finding the correct fit for a road cyclist and the optimal frame geometry.
Moreover saddle position determines seat tube angle as well as the top tube/stem length dimension. The traditional method consists of positioning the rider's saddle so that the knee (the tibial tuberosity) is over the pedal spindle with the crank in horizontal position. This method considers only partially the relation between the positions of arms and torso for different physiques. This special device, adjusted through hydraulic cylinder actuators, allows to achieve optimum horizontal saddle position by measuring horizontal forces on saddle and handlebar. The aim of the research is to determine a quantitative method to establish the optimum rider position in order to minimize the muscular efforts in aerobic phase. Moreover special pedals, developed both for cycling sport performances and for clinical analysis, equipped with three-axial load cells, measure the effective pedalling force exerted by the rider in three orthogonal directions. In particular the lateral force components on the pedals, perpendicular to the para-sagittal plane are measured. Notwithstanding literature usually neglects the lateral components in pathological and non pathological subjects, these components provide meaningful information in rehabilitation treatment of pathological subjects and moreover the biomechanical analysis of pedalling through three-axial force measurements over each pedal allows to improve efficiency during cycling performance
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